硕士研究生考试试题

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2022年考研数学真题(附解析答案)

2022年全国硕士研究生招生考试数学试题(数学三)(科目代码:303)一、选择题：1~10小题，每小题5分，共50分，下列每题给出的四个选项中，只有一个选项是符合题目要求的，请将所有选项前的字母填在答题卡指定位置（1）当0→x 时，)(),(x x βα是非零无穷小量，给出以下四个命题①若)(~)(x x βα，则)(~)(22x x βα②若)(~)(22x x βα，则)(~)(x x βα③若)(~)(x x βα，则))(()()(x o x x αβα=-④若))(()()(x o x x αβα=-，则)(~)(x x βα其中正确的是（）（A）①②（B）①④（C）①③④（D）②③④（2）已知,...)2,1()1(=--=n nn a nn n ，则}{n a （）（A）有最大值，有最小值（B）有最大值，没有最小值（C）没有最大值，有最小值（D）没有最大值，没有最小值（3）设函数)(t f 连续，令0(,)()()d x y F x y x y t f t t -=--⎰，则（）（A）y F x F y F x F 2222,∂∂=∂∂∂∂=∂∂（B）y Fx F y F x F 2222,∂∂-=∂∂∂∂=∂∂（C）yF x F y F x F 2222,∂∂=∂∂∂∂-=∂∂（D）yFx F y F x F 2222,∂∂-=∂∂∂∂-=∂∂（4）已知111123000ln(1)2d d d ,2(1cos )1cos 1sin x x xI x I x I x x x x+===+++⎰⎰⎰，，则（）（A ）321I I I <<（B ）312I I I <<（C ）231I I I <<（D ）123I I I <<（5）设A 为3阶矩阵，100010000⎛⎫⎪=- ⎪ ⎪⎝⎭Λ，则A 的特征值为0,11-，的充分必要条件是（）（A）存在可逆矩阵,P Q ，使得=A PΛQ（B）存在可逆矩阵P ，使得1-=A PΛP （C）存在正交矩阵Q ，使得1-=A QΛQ （D）存在可逆矩阵P ，使得T=A PΛP （6）设矩阵2211111,214a a b b ⎛⎫⎛⎫ ⎪ ⎪== ⎪ ⎪ ⎪ ⎪⎝⎭⎝⎭A b ，则线性方程组=Ax b 解的情况为（）（A）无解（B）有解（C）有无穷多解或无解（D）有唯一解或无解（7）设11,1λ⎛⎫ ⎪= ⎪ ⎪⎝⎭α21,1λ⎛⎫ ⎪= ⎪ ⎪⎝⎭α311,λ⎛⎫ ⎪= ⎪ ⎪⎝⎭α421,λλ⎛⎫ ⎪= ⎪ ⎪⎝⎭α若向量组123,,ααα与124,,ααα等价，则λ的取值范围是（）（A ）}1,0{（B ）}2|{-≠∈λλλ，R （C ）}2,1,|{-≠-≠∈λλλλR （D ）}1|{-≠∈λλλ，R （8）设随机变量)4,0(~N X ，随机变量)31,3(~B Y ，且X 与Y 不相关，则=+-)13(Y X D （）（A）2（B）4（C）6（D）10（9）设随机变量序列 ,,,,21n X X X 独立同分布，且1X 的概率密度为⎩⎨⎧<-=其他,01|||,|1)(x x x f ，则∞→n 时，211i n i X n =∑依概率收敛于（）（A）81（B）61（C）31（D）21（10）设二维随机变量),(Y X 的概率分布若事件}2},{max{=Y X 与事件}1},{min{=Y X 相互独立，则=),(Y X Cov （）（A）6.0-（B）36.0-（C）0（D）0.48Y X0121-0.10.1b 1a0.10.1二、填空题：11-16小题，每小题5分，共30分（11）cot 01e lim()2x xx →+=_______.（12）2224d 24x x x x -=++⎰_______.（13）已知函数sin sin ()e e x x f x -=+，则=''')2(πf _______.（14）已知函数e ,01()0,x x f x ⎧≤≤=⎨⎩其他，则d ()()d x f x f y x y +∞+∞-∞-∞-=⎰⎰_______.（15）设A 为3阶矩阵，交换A 的第2行和第3行，再将第2列的1-倍加到第1列，得到矩阵⎪⎪⎪⎭⎫⎝⎛----001011112，则1-A 的迹1()tr -=A _______.（16）设,,A B C 为随机事件，且A 与B 互不相容，A 与C 互不相容，B 与C 相互独立，31)()()(===C P B P A P ，则=)|(C B A C B P _______.三、解答题：17-22小题，共70分.解答应写出文字说明、证明过程或演算步骤（17）（本题满分10分）设函数)(x y 是微分方程x y xy +=+'221满足条件3)1(=y 的解，求曲线)(x y y =的渐近线.（18）（本题满分12分）设某产品的产量Q 由资本投入量x 和劳动投入量y 决定，生产函数为612112y x Q =，该产品的销售单价P 与Q 的关系为 1.5Q 1160-=P ，若单位资本投入和单位劳动投入的价格分别为6和8,求利润最大时的产量.（19）（本题满分12分）已知平面区域}20,42|),{(2≤≤-≤≤-=y y x y y x D ，计算y x y x y x I Dd d )(222⎰⎰+-=.（20）（本题满分12分）求幂级数nn nn x n 20)12(41)4(∑∞=++-的收敛域及和函数)(x S .（21）已知二次型312322213212343),,(x x x x x x x x f +++=（i）求正交变换=x Qy 将),,(321x x x f 化为标准形；（ii）证明T()min2x f x ≠=x x.（22）设n X X X ,,,21 为来自均值为θ的指数分布总体的简单随机样本，求m Y Y Y ,,,21 为来自均值为θ2的指数分布总体的简单随机样本，且两样本相互独立，其中)0(>θθ是未知参数.利用样本m n Y Y Y X X X ,,,,,,,2121 ，求θ的最大似然估计量θˆ，并求)ˆ(θD .一、选择题：1～10小题，每小题5分，共50分，下列每小题给出的四个选项中，只有一项符合题目要求的，请将所选项前的字母填在答题纸．．．指定位置上. （1）当0x →时，()(),x x αβ是非零无穷小量，给出以下四个命题 ①若()()~x x αβ，则()()22~x x αβ②若()()22~x x αβ，则()()~x x αβ③若()()~x x αβ，则()()()()x x o x αβα-= ④若()()()()x x o x αβα-=，则()()~x x αβ 其中正确的序号是（）（A ）①②（B ）①④ （C ）①③④（D ）②③④【答案】C【解析】当0x →时，()()x x αβ:，则222000()()()lim1,lim lim 1()()()x x x x x x x x x αααβββ→→→⎡⎤===⎢⎥⎣⎦，则： 0()()lim0()x x x x αβα→-=，所以()()(())x x o x αβα-=，故①③正确；当0x →时，22()()x x αβ:，则220()lim 1()x x x αβ→=，则0()lim1()x x x αβ→=±，当0()lim 1()x x x αβ→=-时， ()x α与()x β不是等价无穷小，所以②不正确；当()()(())x x o x αβα-=时，000()()()limlim lim 1()()(())()x x x x x x x x o x x αααβααα→→→===-，④正确.（2）已知()()11,2,nna n n-==L ，则{}n a （）（A ）有最大值，有最小值（B ）有最大值，没有最小值（C ）没有最大值，有最小值（D ）没有最大值，没有最小值【答案】（A ）2022年研究生考试数学三真题及详解【解析】()1lim lim 1nn n n a n →∞→∞⎤-=-=⎥⎥⎣⎦,12121,12a a =>=<，则{}n a 有最大值，有最小值（3）设函数()f t 连续，令()()()0,x yF x y x y t f t dt -=--⎰，则（）（A ）2222,F F F Fx y x y ∂∂∂∂==∂∂∂∂（B ）2222,F F F Fx y x y ∂∂∂∂==-∂∂∂∂（C ）2222,F F F F x y x y∂∂∂∂=-=∂∂∂∂（D ）2222,F F F F x y x y∂∂∂∂=-=-∂∂∂∂【答案】C【解析】原式0()()()x yx yx y f t dt tf t dt --=--⎰⎰则：00()()()()()()x y x y Ff t dt x y f x y x y f x y f t dt x--∂=+-----=∂⎰⎰，22()Ff x y x∂=-∂ 同理：00()()()()()()x y x y Ff t dt x y f x y x y f x y f t dt y--∂=----+--=-∂⎰⎰22()Ff x y y∂=-∂ 综上所述：2222,F F F Fx y x y∂∂∂∂=-=∂∂∂∂.（4）已知1102(1cos )x I dx x =+⎰，120ln(1)1cos x I dx x+=+⎰，13021sin xI dx x =+⎰，则（）（A ）123I I I << （B ）213I I I << （C ）132I I I <<（D ）321I I I <<【答案】A【解析】令()ln(1)2x h x x =+-，11()012h x x '=->+，()0, 1x ∈，于是()h x 单调递增，又由(0)0h =可知()ln(1)02xh x x =+->，其中()0, 1x ∈，故ln(1)2(1cos )1cos x x x x +<++，故12I I <. 当()0, 1x ∈时，，则，故23I I <.（5）设A 为3阶矩阵，100010000⎡⎤⎢⎥Λ=-⎢⎥⎢⎥⎣⎦，则A 特征值为1,1,0-的充分必要条件是（）（A ）存在可逆矩阵,P Q ，使得A P Q =Λ （B ）存在可逆矩阵P ，使得1A P P -=Λ （C ）存在正交矩阵Q ，使得1A Q Q -=Λ （D ）存在可逆矩阵P ，使得T A P P =Λ 【答案】（B ）【解析】若（B ）成立，则矩阵A Λ与相似，特征值相等，可推出A 特征值为1,1,0- 若A 特征值为1,1,0-，则矩阵A 可以相似对角化，矩阵A Λ与相似，所以（B ）为充要条件（6）设矩阵2211111,214A a a b b b ⎡⎤⎡⎤⎢⎥⎢⎥==⎢⎥⎢⎥⎢⎥⎢⎥⎣⎦⎣⎦，则线性方程组Ax b =的解的情况为（）（A ）无解（B ）有解（C ）有无穷多解或无解（D ）有唯一解或无解【答案】（D ）【解析】()()()11A a b b a =---，当1,1,a b a b ≠≠≠时，方程有唯一解，当1a b ==时，()1111,00010000A b ⎡⎤⎢⎥→⎢⎥⎢⎥⎣⎦，方程无解，故选（D ）（7）设1=11λα⎛⎫ ⎪ ⎪ ⎪⎝⎭，21=1αλ⎛⎫ ⎪ ⎪ ⎪⎝⎭，31=1αλ⎛⎫ ⎪ ⎪ ⎪⎝⎭，421=αλλ⎛⎫⎪⎪ ⎪⎝⎭，若向量组123,,ααα与124,,ααα等价，则λ的取值范围是（）)cos 1(22)sin 1()1ln()sin 1(x x x x x x +<<+<++xxx x sin 12cos 1)1ln(+<++（A ）{}01，（B ）{},2R λλλ∈≠-（C ）{},12R λλλλ∈≠-≠-，（D ）{},1R λλλ∈≠-【答案】C【解析】由()()()212311,,=111211λαααλλλλ=-+，()()()22124211,,=11+111λαααλλλλλ=-，当1,λ≠-2,λ≠-时满足题意，故选C.（8）设随机变量()~0,4X N ,随机变量1~3,3Y B ⎛⎫ ⎪⎝⎭，且X Y 与不相关，则()3+1D X Y -=（）（A ）2 （B ）4 （C ）6（D ）10【答案】（D ）【解析】()()113+1+96,4+93101033D X Y DX DY COV X Y ⎛⎫-=-=--= ⎪⎝⎭gg （9）设随机变量序列12,,,,n X X X L L 独立同分布，且1X 的概率密度为()1,10,x x f x ⎧-<⎪=⎨⎪⎩其他，则当n →∞时，211n i i X n =∑依概率收敛于（）（A ）18（B ）16（C ）13（D ）12【答案】（B ）【解析】()()()112222101111216n i i i E X E X x x dx x x dx n -=⎛⎫==-=-= ⎪⎝⎭∑⎰⎰（10）设二维随机变量(),X Y 的概率分布若事件{}{}max ,2X Y =与事件{}{}min ,1X Y =相互独立，则(),COV X Y =（）（A ）0.6- （B ）0.36- （C ）0（D ）0.48【答案】（B ）【解析】{}{}max ,20.1+P X Y b ==；{}{}min ,10.2P X Y =={}{}{}max ,2,min ,10.1P X Y X Y ===， ()0.10.20.1+0.40.2b b a =⇒=⇒=()()()0.6,0.2, 1.2E XY E X E Y =-=-=()()()(),0.36COV X Y E XY E X E Y =-=-二、填空题：11-16小题，每小题5分，共30分，请将答案写在答题纸指定位置上.(11) cot 01lim 2xx x e →⎛⎫+= ⎪⎝⎭【答案】12e【解析】001cot 11lim cot lim22tan 21lim 2x x x x e xe xx In x x e e ee →→⎛⎫+-⋅⎪ ⎪⎝⎭→⎛⎫+=== ⎪⎝⎭(12)22024+2+4x dx x x -=⎰【答案】ln 3- 【解析】()()2222200220242+26+2+4+2+4+1+3ln +2+4ln 3x x dx dx x x x x x x x -=-⎡=⎢⎣=⎰⎰ (13) 已知函数sin sin ()x x f x e e -=+，则(2)f π'''= . 【答案】0【解析】由sin sin ()()x x f x e e f x --=+=，(2)()f x f x π+=，可知()f x 是以2π为周期的偶函数，那么()f x '''是以2π为周期的奇函数，故(2)(0)0f f π''''''==.(14) 已知函数,01()0,x e x f x ⎧≤≤=⎨⎩其他，则()()dx f x f y x dy +∞+∞-∞-∞-=⎰⎰ .【答案】2(1)e -【解析】记{(,)01,01}D x y x y x =≤≤≤-≤，则11120()()(1)(1)x x y x x xdx f x f y x dy dx e e dy e e dx e +∞+∞+--∞-∞-=⋅=-=-⎰⎰⎰⎰⎰.（15）设A 为3阶矩阵，交换A 的第2行和第3行，再将第2列的-1倍加到第一列，得到矩阵211110100--⎛⎫ ⎪- ⎪ ⎪-⎝⎭，则1A -的迹1()tr A -= .【答案】1-【解析】符合左行右列原则由题意可得：2312211(1)110100E AE --⎛⎫⎪-=- ⎪ ⎪-⎝⎭，则：2312211111110(1)100100010A E E ----⎛⎫⎛⎫⎪ ⎪=-=- ⎪ ⎪ ⎪ ⎪--⎝⎭⎝⎭，所以211110(1)(1)001E A λλλλλλ+--==++=，解得1231,,i i λλλ=-==-所以1A -的特征值为1231,,i i λλλ=-==-，所以1()1tr A -=-.（16）设A,B,C 为随机事件，且A 与B 互不相容，A 与C 互不相容，B 与C 相互独立，1()()()3P A P B P C ===，则()P B C A B C =U U U ___________.【答案】58【解析】()()()()()()()()()()P B C P B P C P BC P B C A B C P A B C P A P B P C P BC +-==++-U U U U U U()()()()()()()()()215391819P B P C P B P C P A P B P C P B P C -+-===++--. 三、解答题：17—22小题，共70分.请将解答写在答题纸指定位置上.解答应写出文字说明、证明过程或演算步骤.（17）（本题满分10分）设函数()y x是微分方程2y y '=满足()1=3y 的解，求曲线()y y x =的渐近线. 【答案】2y x =【解析】根据题意，求解微分方程2y y '=+有，()((()2=2y x e dx C eC e -⎛⎫=++ ⎪ ⎪⎝⎭⎰⎰求解(()22+222t t t e tdt t e ⋅==⎰，进而有，()2y x x Ce =+()1=3y ，知=C e ，故而()12y x x e =+进一步，()12limlim 2x x y x x e k x x→+∞→+∞+===，()()1lim lim 0x x b y x kx e →+∞→+∞=-==，故而，曲线()y y x =的渐近线为2y x =. （18）（本题满分10分）设某产品的产量Q 由资本投入量x 和劳动投入量y 决定，生产函数为116212Q x y =，该产品的销售单价P 与Q 的关系为1160 1.5P Q =-，若单位资本投入和单位劳动投入的价格分别为6和8，求利润最大时的产量.【答案】384【解析】利润()111166221160 1.5121268L PQ C x y x y x y ⎛⎫=-=-⨯⨯-+ ⎪⎝⎭，即1116321392021668L x y xy x y =---，令11163252163269602166023207280x yL x y y L x y xy ---⎧'=--=⎪⎨⎪'=--=⎩得驻点()256,64，此时11621225664384Q =⨯⨯=，由于驻点唯一，故利润L 在384Q =时取到最大值.（19）（本题满分12分）已知平面区域(){},22D x y y x y =-≤≤≤≤，计算()222Dx y I dxdy x y -=+⎰⎰【答案】22π- 【解析】方法一：()()()()()1222222222222sin cos 0002222+=cos sin cos sin 122cos sin 2sin cos 22D D x y x y I dxdy dxdyx yx yd rdr d rdr d ππθθπππθθθθθθπθθθθθπ---=++-⋅+-⋅⎛⎫=-+-⋅ ⎪-⎝⎭=-⎰⎰⎰⎰⎰⎰⎰⎰⎰方法二：()1212222222220sin cos 22021=S 22222sin cos 424sin cos sin cos =22D D D D D xy I dxdy x y xydxdy x y xydxdy x yd rdrd πθθπππθθθπθθθθθπ⋃+⎛⎫=- ⎪+⎝⎭-+=+-+=+-⋅⎡⎤=+--⎢⎥+⎢⎥⎣⎦-⎰⎰⎰⎰⎰⎰⎰⎰⎰（20）（本题满分10分）求幂级数20(4)14(21)n nnn x n ∞=-++∑的收敛域及和函数()S x . 【答案】收敛域[1,1]-，12arctan ln ,[1,1]0()22,0x x x x S x x x x ⎧+⎛⎫+∈-≠⎪ ⎪=-⎝⎭⎨⎪=⎩且【解析】11111(4)14(21)(4)14(21)1(4)1lim lim lim4(23)(4)14(23)(4)14(4)1n n n n n n n n n n n n n n n n n +++++→∞→∞→∞-++-++-+⋅=⋅=+-++-+-+ 111(4)1(4)1lim141(4)1(4)n n n n n ++→∞⎡⎤-+⎢⎥-⎣⎦==⎡⎤-+⎢⎥-⎣⎦，进而可得收敛半径为1. 当1x =±时，原级数为000(4)1(1)14(21)214(21)n n n n n n n n n n ∞∞∞===-+-=++++∑∑∑，其中0(1)21nn n ∞=-+∑为交错级数，k 可知其收敛；014(21)nn n ∞=+∑为正项级数，可知其收敛.222000(4)1(1)()4(21)214(21)n n nn n n nn n n x S x x x n n n ∞∞∞===-+-==++++∑∑∑，[1,1]x ∈-. 令2110(1)()21n n n S x x n ∞+=-=+∑，21201()(1)1n n n S x x x ∞='=-=+∑，12()arctan 1dx S x x C x ==++⎰，又1(0)0S =，得0C =.令2120()4(21)n n n x S x n +∞='=+∑，2222004()444nn n n n x x S x x ∞∞==⎛⎫'=== ⎪-⎝⎭∑∑，2242()ln 42xS x dx C x x +==+--⎰，又2(0)0S =，得0C =. 当0x ≠时，arctan 12()ln2x xS x x x x+=+-；又(0)2S =. 综上，12arctan ln ,[1,1]0()22,0x x x x S x x x x ⎧+⎛⎫+∈-≠⎪ ⎪=-⎝⎭⎨⎪=⎩且. （21）（本题满分15分）已知二次型22212312313(,,)3432f x x x x x x x x =+++，（1）求正交变换x Qy =将123(,,)f x x x 化为标准形；（2）证明：()min2T f x x x=. 【答案】（1）00100Q ⎛= ⎪ ⎪ ⎝，（2）见解析. 【解析】（1）301040103A ⎛⎫⎪= ⎪ ⎪⎝⎭，2301040(2)(4)0103A E λλλλλλ--=-=--=-，得特征值12λ=，234λλ==.当12λ=时，1012020000A E ⎛⎫⎪- ⎪ ⎪⎝⎭:，解得特征向量1(1,0,1)T α=-；当234λλ==时，1014000000A E -⎛⎫⎪- ⎪ ⎪⎝⎭:，解得特征向量2(0,1,0)T α=，3(1,0,1)T α=；单位化1(T β=，2(0,1,0)T β=，3T β=得正交矩阵00100Q ⎛= ⎪ ⎪ ⎝，故二次型经过正交变换x Q y =得到的标准形为222123123(,,)244f y y y y y y =++.（2）()TTTx x Qy Qy y y ==，222222123123222222123123244222()()2T T y y y y y y f x f y x x y y y y y y y y ++++==≥=++++，故()min2T f x x x=. （22）（本题满分15分）设12,,,n X X X ⋅⋅⋅为来自均值为θ的指数分布总体的简单随机样本，12,,,m Y Y Y ⋅⋅⋅为来自均值为2θ的指数分布总体的简单随机样本，且两样本相互独立，其中(0)θθ>是未知参数.利用样本1212,,,,,,,n m X X X Y Y Y ⋅⋅⋅⋅⋅⋅，求θ的最大似然估计量$θ，并求$()D θ. 【答案】$2mnX Y n mθ+=+，$2()D n m θθ=+【解析】由题意可知10()0xex f x θθ-⎧>⎪=⎨⎪⎩其他，210()20y ey f y θθ-⎧>⎪=⎨⎪⎩其他，且X 与Y 相互独立，故(,)()()f x y f x f y =.构造似然函数1111211()(2)mnjij i y x nmL e eθθθθθ==--∑∑=⋅⋅⋅，取对数1111ln ()ln ln(2)2nmi ji j L n x m yθθθθθ===----∑∑，求导2211ln ()112nmiji j d L n mx yd θθθθθθ===-+-+∑∑，令ln ()0d L d θθ=，得$2m nX Y n mθ+=+. $22222222111()(2)()4()4()4m m m D n DX DY nDX DY n n m n m n m n m θθθθ⎡⎤⎡⎤⎡⎤=+=+=+=⎢⎥⎢⎥⎢⎥++++⎣⎦⎣⎦⎣⎦。

考研测试试题及答案

考研测试试题及答案一、选择题（每题2分，共20分）1. 下列关于考研的描述，错误的是：A. 考研是全国硕士研究生入学考试的简称B. 考研是选拔研究生的主要方式C. 考研是高中毕业生参加的考试D. 考研通常在每年的12月份举行答案：C2. 考研英语的考试时长为：A. 120分钟B. 150分钟C. 180分钟D. 200分钟答案：B3. 考研数学分为几个科目？A. 1B. 2C. 3D. 4答案：C4. 下列哪项不是考研政治的考试内容？A. 马克思主义哲学B. 毛泽东思想C. 邓小平理论D. 计算机科学答案：D5. 考研复试通常包括哪些环节？A. 笔试B. 面试C. 体检D. 以上都是答案：D6. 考研初试成绩通常在何时公布？A. 考试结束后一个月B. 考试结束后两个月C. 考试结束后三个月D. 考试结束后四个月答案：B7. 考研报名通常在每年的什么时间？A. 6月份B. 9月份C. 12月份D. 次年1月份答案：B8. 考研英语阅读理解部分的题型包括：A. 选择题B. 填空题C. 判断题D. 以上都是答案：D9. 考研数学中，高等数学的分值占比通常为：A. 40%B. 50%C. 60%D. 70%答案：B10. 考研复试中，面试环节主要考察考生的哪些能力？A. 专业基础知识B. 英语听说能力C. 逻辑思维能力D. 以上都是答案：D二、填空题（每题2分，共10分）1. 考研初试通常包括______、______、______三个科目。

答案：政治、英语、专业课2. 考研复试中，考生需要携带的材料通常包括______、______、______等。

答案：身份证、准考证、成绩单3. 考研英语的阅读理解部分，考生需要在______分钟内完成四篇文章的阅读和题目回答。

答案：604. 考研数学的线性代数部分，主要考察考生对______、______、______等概念的理解和应用。

答案：矩阵、向量、线性空间5. 考研政治的考试内容包括______、______、______、______等。

2024考研数学三真题及参考答案

2024年全国硕士研究生入学统一考试数学（三）试题考试时间：180分钟，满分：150分一、选择题：1～10小题，每小题5分，共50分，下列每题给出的四个选项中，只有一个选项符合题目要求，请将所选项前的字母填在答题纸指定位置上.（1）已知函数f (x) = lim ，则( )【答案】D（2）积分+k πsin x dx ( )【答案】Bπ（3）交换积分次序∫π2dx i1n x f (x, y)dy 则( )6【答案】A（4）已知ln(2 + x) = a n x n ,则na2n = ( )（A）−（B）−（C）（D）【答案】A（5）设二次型在正交变换下的标准型为f (x1, x2, x3 ) = y12−2y22+ 3y32，则( )【答案】C（行列式为-6，迹为2）（6）【答案】C（7）【答案】C(a = 0, a = )（8）E[(X −Ex)3 ] = ( )【答案】0（9）【答案】B (p2 > p1> )（10）设随机变量X, Y 相互独立，且均服从参数为λ的指数分布，令Z = X −Y ,则下列随机变量与Z 同分布的是( )（A）X + Y （B）（C）2X （D）X【答案】D二、填空题：11～16小题，每小题5分，共30分，请将答案写在答题纸指定位置上.（11）【答案】3（12）=【答案】ln 3 −n→∞1 + nx n（13）函数f (x , y ) = 2x 3 − 9x 2 − 6y 4 +12x + 24y 的极值点是【答案】 (1,1) （14）【答案】（15）【答案】（16）【答案】50162 3三、解答题：17～22 小题，共 70 分.请将解答写在答题纸指定的位置上.解答应写出文字说明、证明过程或演算步骤.（17）（本题满分 10 分）1 1 已知区域D 是第一象限内的有界区域，它由xy = , xy = 3, y = x , y = 3x 围成， 3 3计算(1+ x − y )dxdy D【答案】 ln 3（18）（本题满分 12 分）∂2 z ∂ 2 z 已知z = z (x , y ) 由方程z + e x + y ln(1+ z 2 ) = 0确定，求 ∂ 2x + ∂ 2 y (0,0)【答案】 −1− 2ln 2（19）（本题满分 12 分）已知t > 0 ，曲线 y = xe −2x 与x = t , x = 2t 及x 轴所围的面积为S (t ) ，求S (t ) 的最大值ln 2 3【答案】 + 16 64（20）（本题满分 12 分）设函数f (x ) 有 2 阶导数，f ′(0) = f ′(1) ， f ′′(x ) ≤ 1（1）当x ∈ (0,1) 时，f (x ) − f (0)(1− x ) − f (1)x ≤ （2） ∫01f (x )dx − ≤【答案】（1）泰勒公式展开（2）分部积分或泰勒公式（21）（本题满分 12 分）【答案】（1） Ax = α 是Bx = β的解（2） a = 1（22）（本题满分 12 分）设总体X 服从[0,θ] 上的均匀分布，X 1, X 2, , X n 为总体的简单随机样本，记X(n) = max{X1, X2, , Xn} ，Tc= cX(n)（1）求c ，使得E(Tc) = θ（2）记h(c) = E(Tc−θ)2 = θ,求c ，使得h(c) 最小【答案】（1）c = （2）c =参考答案一、选择题：1-10小题，每小题5分，共50分.下列每题给出的四个选项中，只有一个选项是最符合题目要求的，请将所选项前的字母填在答题纸指定位置上。

2023年全国研究生入学考试政治真题答案及解析(完整版)

2023年全国研究生入学考试政治真题答案及解析(完整版)2023年全国硕士研究生招生考试思想政治理论试题及解析一、单项选择题：共16题，每小题1分，共16分。

下列每题给出的四个选项中，只有一个选项是符合题目要求的。

1、习近平总书记在为《复兴文库》所写的序言中指出：“修史立典，存史启智，以文化人，这是中华民族延续几千年的一个传统。

”“编纂出版《复兴文库》大型历史文献丛书，就是要对近代以来重要思想文献的选编，述录先人的开拓，启迪来者的奋斗。

”“历史是最好的教科书，一切向前走都不忘记走过的路;走的再远，走到再辉煌的未来，也不能忘记走过的过去。

”这表明：A.历史、现实、未来是相通的B.一切历史都是当代史C.历史过程不包含任何偶然的因素D.历史事件往往可以完整重复和再现【答案】A2、社会形态是关于社会运动的具体形式、发展阶段和不同质态的范畴。

是同生产力发展一定阶段相适应的经济基础同上层建筑的统一体。

人类社会历史划分为原始社会、奴隶社会、封建社会、资本主义社会和共产主义社会(社会主义社会是其第一阶段)五种社会形态，其依据是()A.生产工具的质量和数量B.统治集团的阶级和政治属性C.经济基础特别是生产关系的性质D.人们的社会交往和分工的范围和水平【答案】C3、马克思在《资本论》中指出：“不管生产力发生了什么变化，同一劳动在同样的时间内提供的价值量总是相同的。

但它在同样的时间内提供的使用价值量会是不同的：生产力提高时就多些，生产力降低时就少些。

”这段话表明，生产力的变化A.不影响同一劳动在同样的时间内生产的商品数量B.不改变同一劳动在同样的时间内的效率C.影响同一劳动在同样的时间内生产的单个商品价值量D.改变同一劳动在同样时间内提供的价值总量【答案】C4、垄断组织通过制定垄断价格来获得垄断利润。

在市场交易过程中，垄断组织获利高低实际上受到很多因素的影响。

为了避免遭受净亏损，垄断组织所能接受的而最低价格是() A成本价格B生产价格C垄断低价D垄断高价【答案】B5、什么是社会主义，怎样建设社会主义，是邓小平在领导改革开放和现代化建设过程中，不断提出和反复思考的首要的基本理论问题。

2023 年全国硕士研究生入学统一考试考研英语(一)真题

2023Section I Use of EnglishDirections:Read thefollowing text.Choose the best word(s)for each numbered blank and mark A,B,C or D on the ANSWER SHEET.(10 points)It’s not difficult to set targets for staff. It is much harder, 1 ,to understand their negative consequences.Most work-related behaviors have multiple components. 2 one and the others become distorted.Travel on a London bus and you’ll 3 see how this works with drivers.Watch people get on and show their tickets.Are they carefully inspected? Never. Do people get on without paying? Of course! Are there inspectors to 4 that people have paid? Possibly, but very few. And people who run for the bus? They are 5 . How about jumping lights? Buses do so almost as frequently as cyclists.Why? Because the target is 6 . People complained that buses were late and infrequent. 7 , the number of buses and bus lanes were increased, and drivers were 8 or punished according to the time they took. And drivers hit these targets. But they 9 hit cyclists. If the target was changed to 10 , you would have more inspectors and moresensitive pricing.If the criterion changed to safety,you would get more 11 drivers who obeyed traffic laws. But both these criteria would be at the expense of time.There is another 12 : people became immensely inventive in hitting targets. Have you 13 that you can leave on a flight an hour late but still arrive on time? Tailwinds? Of course not! Airlines have simply changed the time a 14 is meant to take. A one-hour flight is now ballad as a two-hour flight.The 15 of the story is simple. Most jobs are multidimensional, with multiple criteria. Choose one criterion and you may well 16 others.Everything Can be done faster and made cheaper,but there is a 17 Setting targets can and does have unforeseen negative consequences.This is not an argument against target-setting.But it is an argument for exploring consequences first.All good targets should have multiple criteria 18 critical factors such as time, money, quality and customer feedback. The trick is not only to 19 just one or even two dimensions of the objective, but also to understand how to help people better 20 the objective.1. [A] Some [B] Most [C] Few [D] All2 ．[A] put [B] take [C] run [D] come3 ．[A] Since [B] If [C] Though [D] Until4 ．[A] formally [B] relatively [C] gradually [D] literally5 ．[A] back [B] next [C] around [D] away6 ．[A] onto [B] off [C] across [D] alone7 ．[A] unattractive [B] uncrowded [C] unchanged [D] unfamiliar8 ．[A] site9 ．[A] So 10．[A] immediately 11．[A] surprised 12．[A] problem 13．[A] Above all 14．[A] bridge 15．[A] form 16．[A] posts17 ．[A] artificial 18．[A] Finally 19．[A] memories 20．[A] restrict [B] point[B] Yet[B] intentionally[B] annoyed[B]option[B] In contrast[B] avoid[B] through[B] links[B] mysterious[B] Consequently[B] marks[B] adopt[C] way[C] Instead[C]unexpectedly[C] frightened[C] view[C] On average[C] spot[C] beyond[C] shades[C] hidden[C]incidentally[C] notes[C] lead[D] place[D] Besides[D] eventually[D] confused[D] result[D] For example[D] separate[D] under[D] breaks[D] limited[D] Generally[D] belongings[D] exposeSection II Reading ComprehensionPart ADirections:Read thefollowingfour texts.Answer the questions below each text by choosing A,B,C or D.Mark your answers on the ANSWER SHEET.(40points)Text2Communities throughout New England have been attemptingto regulate short-term rentals since sites like Airbnb took off in the2010s. Now with record-high home prices and historically low inventory,there’s an increased urgency in such regulation,particularly among those whoworry that developers will come in and buy up swaths of housing to flip for a fortune on the short-term rental market.In New Hampshire,where the rental vacancy rate has dropped below 1percent,housing advocates fear unchecked short-term rentals will put further pressure on an already strained market. The State Legislature recently voted against a bill that would’ve made it illegal for towns to create legislation restricting short-term rentals.“We are at a crisis level on the supply of rental housing,”said Nick Taylor, executive director of the Workforce Housing Coalition of the Greater Seacoast. Without enough affordable housing in southern New Hampshire towns,“ employers are having a hard time attracting employees, and workers are having a hard time finding a place to live,” Taylor said.However, short-term rentals also provide housing for tourists, pointed out Ryan Castle,CEO of a local association of realter.“A lot of workers are servicing the tourist industry,and the tourism industry is serviced by those people coming in short term,”Castle said,“and so it’s a cyclical effect.”Short-term rentals themselves are not the crux of the issue, said Keren Horn,an expert on affordable housing policy.“I think individuals being able to rent out their second home is a good thing.If it’s their vacation home anyway,and it’s just empty,why can’t you make money off it?”Horn said. Issues arise, however, when developers attempt to create large-scale short-term rental facilities— de facto hotels — to bypass taxesand regulations. “I think the question is, shouldn’t a developer who’s really building a hotel,but disguising it as not a hotel,be treated and taxed and regulated like a hotel?” Horn said.At the end of 2018, governor Charlie Baker of Massachusetts signed a bill to rein in those potential investor-buyers. The bill requires every rental host to register with the state mandates they carry insurance, and opens the potential for local taxes on top of a new state levy. Boston took things even further,requiring renters to register with the city’s Inspectional Services Department.Horn said similar registration requirements could benefit struggling cities and towns, but “if we want to make a change in the housing market, the main one is we have to build a lot more.”26. Which of the following is true of New England?A. Its housing supply is at a very low level.B. Its communities are in need of funding.C. Its rental vacancy rate is going up slowlyD. Its home prices are under strict control.27. The bill mentioned in Paragraph 2 was intended toA. curb short-term rental speculation.B. ensure the supply of cheap housing.C. punish illegal dealings in housing.D. allow a free short-term rental market.28. Compared with Castle, Taylor is more likely to supportA. further investment in local tourism.B. an increase in affordable housing.C. strict management of real estate agents.D. a favorable policy for short-term workers.29. What does Horn emphasize in Paragraph 5?A. The urgency to upgrade short-term rental facilities.B. The efficient operation of the local housing market.C. The necessity to stop developers from evading taxes.D. The proper procedures for renting out spare houses.30. Horn holds that imposing registration requirements isA. an irrational decision.B. an unfeasible proposal.C. an unnecessary measure.D. an inadequate solution.Text3If you’re heading for your nearest branch of Waterstones,the biggest book retailer in the UK, in search of the Duchess of Sussex’s new children’s book The Bench, you might have to be prepared to hunt around a bit, the same may be true of The President’s Daughter, the new thriller by Bill Clinton and James Patterson.Both of these books are published next week by Penguin Random House(PRH), a company currently involved in a stand-offwith Waterstones.The problem began late last year,when PRH confirmed that it had introduced a credit limit with Waterstones “at a very significant level”. The trade magazine The Bookseller reported that Waterstones branch managers were being told to remove PRH books from prominent areas such as tables, display spaces and windows, and were“ quietly retiring them to their relevant sections” .PRH declined to comment on the issue, but a spokesperson for Waterstones told me:“Waterstones are currently operating with reduced credit terms from PRH, the only publisher in the UK to place any limitations on our ability to trade. We are not boycotting PRH titles but we are doing our utmost to ensure that availability for customers remains good despite the lower overall levels of stock.We are hopeful with our shops now open again that normality will return and that we will be allowed to buy appropriately.Certainly,our shops are exceptionally busy.The sales for our May Books of the Month surpassed any month since 2018.”In the meantime,PRH authors have been the losers.Big-name PRH authors may suffer a bit, but it’s those mid-list authors, who normally rely on Waterstones staff’s passion for promoting books by lesser-known writers, who will be praying for an end to the dispute.It comes at a time when authors are already worried about the consequences of the proposed merger between PRH and another big publisher,Simon &Schuster—the reduction in the number of unaligned UK publishers is likely to lead to fewer bidding wars, lower advances, and more conformity in terms of what is published.“This is all part of a wider change towards concentration of power,”says literary agent Andrew Lownie.“The publishing industry talks about diversity in terms of authors and staff but it also needs a plurality of ways of delivering intellectual contact, choice and different voices. After all, many of the most interesting books in recent years have come from small publishers.”We shall see whether that plurality is a casualty of the current need among publishers to be big enough to take on all-comers.31. The author mentions two books in Paragraph 1 to presentA. an ongoing conflict.B. an intellectual concept.C. a prevailing sentiment.D. a literary phenomenon.32. Why did Waterstones shops retire PRH books to their relevant sections?A. To make them easily noticeable.B. To comply with PRH’s requirement.C. To respond to PRH’s business move.D. To arrange them in a systematic way.33. What message does the spokesperson for Waterstones seem to convey?A. Their customers remain loyal.B. The credit limit will be removed.C. Their stock is underestimated.D. The book market is rather slack.34.What can be one consequence of the current dispute?A. Sales of books by mid-list PRH writers fall off considerably.B. Lesser-known PRH writers become the target of criticism.C. Waterstones staff hesitate to promote big-name authors’ books.D. Waterstones branches suffer a severe reduction in revenue.35. Which of the following statements best represents Lownie’s view?A. Small publishers ought to stick together.B. Big publishers will lose their dominance.C. The publishing industry is having a hard time.D. The merger of publishers is a worrying trend.Text4Scientific papers are the recordkeepers of progress in research.Each year researchers publish millions of papers in more than 30,000journals. The scientific community measures the quality of those papers in a number of ways,including the perceived quality of the journal (as reflected by the title’s impact factor) andthe number of citations a specific paper accumulates. The careers of scientists and the reputation of their institutions depend on the number and prestige of the papers they produce,but even more so on the citations attracted by these papers.Citation cartels,where journals,authors,and institutions conspire to inflate citation numbers, have existed for a long time. In 2016, researchers developed an algorithm to recognize suspicious citation patterns,including groups of authors that disproportionately cite one another and groups of journals that cite each other frequently to increase the impact factors of their publications.Recently,another expression of this predatory behavior has emerged:so-called support service consultancies that provide languageand other editorial support to individual authors and to journals sometimes advise contributors to add a number of citations to their articles.The advent of electronic publishing and authors’need to find outlets for their papers resulted in thousands of new journals. The birth of predatory journals wasn’t far behind.These journals can act as milk cows where every single article in an issue may cite a specific paper or a series of papers.In some instances,there is absolutely no relationship between the content of the article and the citations.The peculiar part is that the journal that the editor is supposedly working for is not profiting at all — it is just providing citations to other journals.Such practices can lead an article to accrue more than 150 citations in the same year that it was published.How insidious is this type of citation manipulation?In one example, an individual - acting as author, editor, and consultant - was able to use at least 15 journals as citation providers to articles published by five scientists at three universities. The problem is rampant in Scopus, a citation database, which includes a high number of the new “international” journals. In fact, a listing in Scopus seems to be a criterion to be targeted in this type of citation manipulation.Scopus itself has all the data necessary to detect this malpractice. Red flags include a large number of citations to an article within the first year. And for authors who wish to steer clear of citation cartel activities:whenan editor, a reviewer,or a support service asks you to add inappropriate references, do not oblige and do report the request to the journal.36.According to Paragraph 1,the careers of scientists can be determined by________.[A] how many citations their works contain.[B] how many times their papers are cited.[C] the prestige of the people they work with.[D] the status they have in scientific circles.37. The support service consultancies tend to________.[A] recommend journals to their clients.[B] list citation patterns their clients.[C] ask authors to include extra citations.[D] advise contributors to cite each other.38. The Function of the “milk cow” journals is to________.[A] boost citation counts for certain authors.[B] help scholars publish articles at low cost.[C] instruct First-time contributors in citation.[D] increase the readership of new journals.39. What can be learned about Scopus from the last two paragraphs?[A] It Fosters competition among citation providers.[B] It has the capability to identify suspicious citations.[C] It hinders the growth of “international” journals.[D] It is established to prevent citation manipulation.40. What should an author do to deal with citation manipulators?[A] Take legal action.[B] Demand an apology.[C] Seek professional advice[D] Reveal their misconduct.Part CDirections:Read the following text carefully and then translate the underlined segments into Chinese.Write your answers on the ANSWER SHEET.(10points)46.AI can also be used to identify the lifestyles choices of customers regarding their hobbies, favorite celebrities, and fashions to provide unique content in marketing messages put out through social media.47.Some believe that AI is negatively impacting on the marketer's roleby reducing creativity and removing jobs,but they are aware that it is a way of reducing costs and creating new information.48.Algorithms used to simulate human interactions are creating many of those concerns,especially as no-one is quite sure what the outcomes of using AI to interact with customers will be.49.If customers are not willing to share data,AI will be starved of essential information and will not be able to function effectively or employ machine learning to improve its marketing content and communication.50.The non-intrusive delivery of the marketing message in a way that is sensitive to the needs of target customers is one of the critical challenges to the digital marketer.Section III WritingPart A51.Write a notice to recruit a student for Prof. Smith’s research project on campus sports activities. Specify the duties and requirements of the job.Write your answer about 100 words on the ANSWER SHEET.Do not use your own name in the notice; use “Li Ming”instead.(10 points)Part B52.Directions:Write an essay of 160-200 words based on the picture below. In your essay you should1) describe the picture briefly,2) interpret the implied meaning, and3) give your comments.You should write neatly on the ANSWER SHEET. (20 points)。

全国硕士研究生入学考试政治试卷

全国硕士研究生入学考试政治试卷全国硕士研究生入学考试政治试卷通常包括两个部分：政治理论知识和政治实践问题。

下面是一个关于政治理论知识方面的示例参考内容：一、马克思主义基本原理1. 马克思主义的三个组成部分：唯物史观、政治经济学和科学社会主义理论。

分别解释这三个组成部分的基本观点和理论内容。

2. 马克思主义的历史地位和基本特征。

包括马克思主义的创新性理论、实践性和革命性，以及对人类社会历史发展规律的科学把握。

3. 马克思主义与中国特色社会主义思想的关系。

强调中国特色社会主义是中国共产党集体智慧的结晶，是马克思主义在中国的运用和发展。

二、中国特色社会主义理论体系1. 中国特色社会主义的基本内涵和总任务。

强调实现社会主义现代化，建设富强民主文明和谐美丽的社会主义现代化强国。

2. 中国特色社会主义道路的形成和基本经验。

分析中国特色社会主义道路的基本起点、指导思想和核心要义。

3. 中国特色社会主义制度的优越性和巩固性。

重点包括中国共产党的核心领导地位、人民当家作主和依法治国，以及中国特色社会主义事业总体布局和稳定发展。

三、中国共产党的基本理论和指导思想1. 马克思主义中国化的理论成果和指导思想。

包括毛泽东思想、邓小平理论、三个代表重要思想、科学发展观和习近平新时代中国特色社会主义思想的形成及其重要内容。

2. 中国共产党的基本任务和历史使命。

强调中国共产党的性质、宗旨、纲领和组织建设，以及党的建设的重要性和基本要求。

3. 党的领导作用的历史经验和根本要求。

包括党的领导地位和核心作用，以及党的群众路线和党风政风建设。

四、党的建设和党风廉政建设问题1. 党的建设的总体布局和基本要求。

包括党的十八大以来的党内政治文化建设、党的群众路线教育实践活动、打虎拍蝇反腐败斗争等。

2. 党风廉政建设的重要内容和任务。

强调党风廉政建设的重要性和严肃性，以及党风廉政建设的总体要求和具体举措。

3. 党风廉政建设和党的执政能力建设的关系。

2022 年全国硕士研究生入学统一考试英语(一)试题及答案

2022年全国硕士研究生入学统一考试英语（一）试题SectionⅠUse of EnglishDirections:Read the following text.Choose the best word(s)for each numbered blank and mark A,B,C or D on the ANSWER SHEET.(10points)The idea that plants have some degree of consciousness first took root in the early2000s;the term“plant neurobiology”was1around the notion that some aspects of plant behavior could be2to intelligence in animals.3plants lack brains,the firing of electrical signals in their stems and leaves nonetheless triggered responses that4consciousness,researchers previously reported.But such an idea is untrue,according to a new opinion article.Plant biology is complex and fascinating,but it 5so greatly from that of animals that so-called6of plants’intelligence is inconclusive,the authors wrote.Beginning in2006,some scientists have7that plants possess neuron-like cells that interact with hormones and neurotransmitters,8“a plant nervous system,9to that in animals,”said lead study author Lincoln Taiz,“They10claimed that plants have‘brain-like command centers’at their root tips.”This11makes sense if you simplify the workings of a complex brain,12it to an array of electrical pulses;cells in plants also communicate through electrical signals.13,the signaling in a plant is only14 similar to the firing in a complex animal brain,which is more than“a mass of cells that communicate by electricity,”Taiz said.“For consciousness to evolve,a brain with a threshold15of complexity and capacity is required,”he 16.“Since plants don’t have nervous systems,the17that they have consciousness are effectively zero.”And what’s so great about consciousness,anyway?Plants can’t run away from18,so investing energy in a body system which19a threat and can feel pain would be a very20evolutionary strategy,according to the article.1.[A]coined[B]discovered[C]collected[D]issued2.[A]attributed[B]directed[C]compared[D]confined3.[A]Unless[B]When[C]Once[D]Though4.[A]cope with[B]consisted of[C]hinted at[D]extended in5.[A]suffers[B]benefits[C]develops[D]differs6.[A]acceptance[B]evidence[C]cultivation[D]creation7.[A]doubted[B]denied[C]argued[D]requested8.[A]adapting[B]forming[C]repairing[D]testing9.[A]analogous[B]essential[C]suitable[D]sensitive10.[A]just[B]ever[C]still[D]even11.[A]restriction[B]experiment[C]perspective[D]demand12.[A]attaching[B]reducing[C]returning[D]exposing13.[A]However[B]Moreover[C]Therefore[D]Otherwise14.[A]temporarily[B]literally[C]superficially[D]imaginarily15.[A]list[B]level[C]label[D]local16.[A]recalled[B]agreed[C]questioned[D]added17.[A]chances[B]risks[C]excuses[D]assumptions18.[A]danger[B]failure[C]warning[D]control19.[A]represents[B]includes[C]reveals[D]recognizes20.[A]humble[B]poor[C]practical[D]easySectionⅡReading ComprehensionPart ADirections:Read the following four texts.Answer the questions below each text by choosing A,B,C or D.Mark your answers on the ANSWER SHEET.(40points)Text1People often complain that plastics are too durable.Water bottles,shopping bags,and other trash litter the planet,from Mount Everest to the Mariana Trench,because plastics are everywhere and don't break down easily. But some plastic materials change over time.They crack and frizzle.They“weep”out additives.They melt into sludge.All of which creates huge headaches for institutions,such as museums,trying to preserve culturally important objects.The variety of plastic objects at risk is dizzying:early radios,avant-garde sculptures,celluloid animation stills from Disney films,the first artificial heart.Certain artifacts are especially vulnerable because some pioneers in plastic art didn't always know how to mix ingredients properly,says Thea van Oosten,a polymer chemist who,until retiring a few years ago,worked for decades at the Cultural Heritage Agency of the Netherlands.“It s like baking a cake:If you don’t have exact amounts,it goes wrong.”she says.“The object you make is already a time bomb.”And sometimes,it's not the artist's fault.In the1960s,the Italian artist Picro Gilardi began to create hundreds of bright,colorful foam pieces.Those pieces included small beds of roses and other items as well as a few dozen “nature carpets”—large rectangles decorated with foam pumpkins,cabbages,and watermelons.He wanted viewers to walk around on the carpets—which meant they had to be durable.Unfortunately,the polyurethane foam he used is inherently unstable.It's especially vulnerable to light damage,and by the mid-1990s,Gilardi’s pumpkins,roses,and other figures were splitting and crumbling.Museums locked some of them away in the dark.So van Oosten and her colleagues worked to preserve Gilardi’s sculptures.They infused some with stabilizing and consolidating chemicals.Van Oosten calls those chemicals“sunscreens”because their goal was to prevent further light damage and rebuild worn polymer fibers.She is proud that several sculptures have even gone on display again,albeit sometimes beneath protective cases.Despite success stories like van Oosten’s,preservation of plastics will likely get harder.Old objects continue to deteriorate.Worse,biodegradable plastics designed to disintegrate,are increasingly common.And more is at stake here than individual objects.Joana Lia Ferreira,an assistant professor of conservation and restoration at the nova School of Science and Technology,notes that archaeologists first defined the great material ages of human history Stone Age,Iron Age,and so on after examining artifacts in museums.We now live in an age of plastic,she says,“and what we decide to collect today,what we decide to preserve.…will have a strong impact on how in the future we'll be seen.”21.According to Paragraph1,museums are faced with difficulties in______.[A]maintaining their plastic items[B]obtaining durable plastic artifacts[C]handling outdated plastic exhibits[D]classifying their plastic collections22.Van Oosten believes that certain plastic objects are______.[A]immune to decay[B]improperly shaped[C]inherently flawed[D]complex in structure23.Museums stopped exhibiting some of Gilardi's artworks to______.[A]keep them from hurting visitors[B]duplicate them for future display[C]have their ingredients analyzed[D]prevent them from further damage24.The author thinks that preservation of plastics is______.[A]costly[B]unworthy[C]unpopular[D]challenging25.In Ferreira’s opinion,preservation of plastic artifacts_______.[A]will inspire future scientific research[B]has profound historical significance[C]will help us separate the material ages[D]has an impact on today’s cultural lifeText2As the latest crop of students pen their undergraduate application form and weigh up their options,it may be worth considering just how the point,purpose and value of a degree has changed and what Generation Z need to consider as they start the third stage of their educational journey. Millennials were told that if you did well in school,got a decent degree,you would be set up for life.But that promise has been found wanting.As degrees became universal,they became cation was no longer a secure route of social mobility.Today,28per cent of graduates in the UK are in non-graduate roles,a percentage which is double the average among OECD countries. This is not to say that there is no point in getting a degree,but rather stress that a degree is not for everyone, that the switch from classroom to lecture hall is not an inevitable one and that other options are available. Thankfully,there are signs that this is already happening,with Generation Z seeking to learn from their millennial predecessors,even if parents and teachers tend to be still set in the degree mindset.Employers have long seen the advantages of hiring school leavers who often prove themselves to be more committed and loyal employees than graduates.Many too are seeing the advantages of scrapping a degree requirement for certain roles. For those for whom a degree is the desired route,consider that this may well be the first of many.In this age of generalists,it pays to have specific knowledge or skills.Postgraduates now earn40per cent more than graduates.When more and more of us have a degree,it makes sense to have two. It is unlikely that Generation Z will be done with education at18or21;they will need to be constantly up-skilling throughout their career to stay employable.It has been estimated that this generation,due to the pressures of technology,the wish for personal fulfilment and desire for diversity,will work for17different employers over the course of their working life and have five different cation,and not just knowledge gained on campus,will be a core part of Generation Z’s career trajectory. Older generations often talk about their degree in the present and personal tense:‘I am a geographer.’or‘I am a classist.’Their sons or daughters would never say such a thing;it’s as if they already know that their degree won’t define them in the same way.26.the author suggests that Generation Z should____[A]be careful in choosing a college[B]be diligent at each educational stage[C]reassess the necessity of college education[D]postpone their undergraduate application27.The percentage of UK graduates in non-graduate roles reflect_______.[A]Millennial's opinions about work[B]the shrinking value of a degree[C]public discontent with education[D]the desired route of social mobility28.The author considers it a good sign that____.[A]Generation Z are seeking to earn a decent degree.[B]School leavers are willing to be skilled workers.[C]Employers are taking a realistic attitude to degrees.[D]Parents are changing their minds about education.29.It is advised in Paragraph5that those with one degree should______.[A]make an early decision on their career[B]attend on the job training programs[C]team up with high-paid postgraduates[D]further their studies in a specific field30.What can be concluded about Generation Z from the last two paragraphs?[A]Lifelong learning will define them.[B]They will make qualified educators.[C]Degrees will no longer appeal them.[D]They will have a limited choice of jobs.Text3Enlightening,challenging,stimulating,fun.These were some of the words that Nature readers used to describe their experience of art-science collaborations in a series of articles on partnerships between artists and researchers.Nearly40%of the roughly350people who responded to an accompanying poll said,they had collaborated with artists,and almost all said they would consider doing so in future.Such an encouraging results is not surprising.Scientists are increasingly seeking out visual artists to help them communicate their work to new audiences.“Artists help scientists reach a broader audience and make emotional connections that enhance learning.”One respondent said.One example of how artists and scientists have together rocked the scenes came last month when the Sydney Symphony Orchestra performed a reworked version of Antonio Vivaldi’s The Four Seasons.They reimagined the 300-year-old score by injecting the latest climate prediction data for each season-provided by Monash University's Climate Change Communication Research Hub.The performance was a creative call to action ahead of November's United Nations Climate Change Conference in Glasgow,UK.But a genuine partnership must be a two-way street.Fewer artist than scientists responded to the Nature poll, however,several respondents noted that artists do not simply assist scientists with their communication requirements.Nor should their work be considered only as an object of study.The alliances are most valuable when scientists and artists have a shared stake in a project,are able to jointly design it and can critique each other’s work.Such an approach can both prompt new research as well as result in powerful art.More than half a century ago,the Massachusetts Institute of Technology opened its Center for Advanced Visual Studies(CAVS)to explore the role of technology in culture.The founders deliberately focused theirprojects around light-hance the“visual studies”in the name.Light was a something that both artists and scientists had an interest in and therefore could form the basis of collaboration.As science and technology progressed,and divided into more sub-disciplines,the centre was simultaneously looking to a time when leading researchers could also be artists,writers and poets,and vice versa.Nature’s poll findings suggest that this trend is as strong as ever,but,to make a collaboration work both sides need to invest time and embrace surprise and challenge.The reach of art-science tie-ups needs to go beyond the necessary purpose of research communication,and participants.Artists and scientists alike are immersed in discovery and invention,and challenge and critique are core to both,too.31.According to paragraph1,art-science collaborations have____[A]caught the attention of critics[B]received favorable responses[C]promoted academic publishing[D]sparked heated public disputes32.The reworked version of The Four Seasons is mentioned to show that____[A]art can offer audiences easy access to science[B]science can help with the expression of emotions[C]public participation in science has a promising future[D]art is effective in facilitating scientific innovations33.Some artists seem to worry about in the art-science partnership___.[A]their role may be underestimated[B]their reputation may be impaired[C]their creativity may be inhibited[D]their work may be misguided34.What does the author say about CAVS?[A]It was headed alternately by artists and scientists[B]It exemplified valuable art-science alliances[C]Its projects aimed at advancing visual studies[D1Its founders sought to raise the status of artists35.In the last paragraph,the author holds that art-science collaborations_____[Al are likely to go beyond public expectations[B]will intensify interdisciplinary competition[C]should do more than communicating science[D]are becoming more popular than beforeText4The personal grievance provisions of New Zealand’s Employment Relations Act2000(ERA)prevent an employer from firing an employee without good cause.Instead,dismissals must be justified.Employers must bothshow cause and act in a procedurally fair way.Personal grievance procedures were designed to guard the jobs of ordinary workers from“unjustified dismissals”The premise was that the common law of contract lacked sufficient safeguards for workers against arbitrary conduct by management.Long gone are the days when a boss could simply give an employee contractual notice.But these provisions create difficulties for businesses when applied to highly paid managers and executives. As countless boards and business owners will attest,constraining firms from firing poorly performing, high-earning managers is a handbrake on boosting productivity and overall performance.The difference between C-grade and A-grade managers may very well be the difference between business success or failure.Between preserving the jobs of ordinary workers or losing them.Yet mediocrity is no longer enough to justify a dismissal. Consequently-and paradoxically-laws introduced to protect the jobs of ordinary workers may be placing those jobs at risk.If not placing jobs at risk,to the extent employment protection laws constrain business owners from dismissing under-performing managers,those laws act as a constraint on firm productivity and therefore on workers’wages.Indeed,in“An International Perspective on New Zealand’s Productivity Paradox”(2014),the Productivity Commission singled out the low quality of managerial capabilities as a cause of the country's poor productivity growth record.Nor are highly paid managers themselves immune from the harm caused by the ERA's unjustified dismissal procedures.Because employment protection laws make it costlier to fire an employee,employers are more cautious about hiring new staff.This makes it harder for the marginal manager to gain employment.And firms pay staff less because firms carry the burden of the employment arrangement going wrong.Society also suffers from excessive employment protections.Stringent job dismissal regulations adversely affect productivity growth and hamper both prosperity and overall well-being.Across the Tasman Sea,Australia deals with the unjustified dismissal paradox by excluding employees earning above a specified“high-income threshold”from the protection of its unfair dismissal laws.In New Zealand,a206private members’Bill tried to permit firms and high-income employees to contract out of the unjustified dismissal regime.However,the mechanisms proposed were unwieldy and the Bill was voted down following the change in government later that year.36.The personal grievance provisions of the ERA are intended to____.[A]punish dubious corporate practices[B]improve traditional hiring procedures[C]exempt employers from certain duties[D]protect the rights of ordinary workers37.It can be learned from paragraph3that the provisions may____.[A]hinder business development[B]undermine managers authority[C]affect the public image of the firms[D]worsen labor-management relations38.Which of the following measures would the Productivity Commission support?[A]Imposing reasonable wage restraints.[B]Enforcing employment protection laws.[C]Limiting the powers of business owners.[D]Dismissing poorly performing managers.39.What might be an effect of ERA's unjustified dismissal procedures?[A]Highly paid managers lose their jobs[B]Employees suffer from salary cuts.[C]Society sees a rise in overall well-being.[D]Employers need to hire new staff.40.It can be inferred that the“high-income threshold”in Australia[A]has secured managers’earnings[B]has produced undesired results[C]is beneficial to business owners[D]is difficult to put into practicePart BDirections:Read the following text and answer the questions by choosing the most suitable subheading from the list A-G for each numbered paragraphs(41-45).There are two extra subheadings which you do not need to use. Mark your answers on ANSWER SHEET.(10points)(41)Teri ByrdI was a zoo and wildlife park employee for years.Both the wildlife park and zoo claimed to be operating for the benefit of the animals and for conservation purposes.This claim was false.Neither one of them actually participated in any contributions whose bottom line is much more important than the condition of the animals. Animals despise being captives in zoos.No matter how you enhance enclosures,they do not allow for freedom,a natural diet or adequate time for transparency with these institutions,and it's past time to eliminate zoos from our culture.(42)Karen R.SimeAs a zoology professor,I agree with Emma Marris that zoo displays can be sad and cruel.But she underestimates the educational value of zoos.The zoology program at my university attracts students for whom zoo visits were the crucial formative experience that led them to major in biological sciences.These are mostly students who had no opportunity as children to travel to wilderness areas,wildlife refuges or national parks.Although good TV shows can help stir children's interest in conservation,they cannot replace the excitement of a zoo visit as an intense,immersive and interactive experience.Surely there must be some middle ground that balances zoos treatment of animals with their educational potential.(43)Reg NewberryEmma Marris's article is an insult and a disservice to the thousands of passionate who work tirelessly to improve the lives of animals and protect our planet.She uses outdated research and decades-old examples to undermine the noble mission of organization committed to connecting children to a world beyond their own.Zoos are at the forefront of conservation and constantly evolving to improve how thy care for animals and protect each species in its natural habitat.Are there tragedies?Of course.But they are the exception not the norm that Ms Marris implies A distressed animal in a zoo will get as good or better treatment than most of us at our local hospital.(44)Dean GalleaAs a fellow environmentalist animal-protection advocate and longtime vegetarian.I could properly be in the same camp as Emma Marris on the issue of zoos.But I believe that well-run zoos and the heroic animals that suffer their captivity so serve a higher purpose.Were it not for opportunities to observe these beautiful wild creatures close to home many more people would be driven by their fascination to travel to wild areas to seek out disturb and even hunt them down.Zoos are in that sense similar to natural history and archeology museums serving to satisfy our need for contact with these living creatures while leaving the vast majority undisturbed in their natural environments(45)John FraserEmma Marris selectively describes and misrepresents the findings of our research.Our studies focused on the impact of zoo experiences on how people think about themselves and nature and the data points extracted from our studies.Zoos are tools for thinking.Our research provides strong support for the value of zoos in connecting people with animals and with nature.Zoos provide a critical voice for conservation and environmental protection. They afford an opportunity for people from all backgrounds to encounter a range of animals from drone bees to springbok or salmon to better understand the natural world we live in.[A]Zoos,which spare no effort to take of animals,should not be subjected to unfair criticism.[B]To pressure zoos to spend less on their animals would lead to inhumane outcomes for the precious creatures in their care.[C]While animals in captivity deserve sympathy,zoos play a significant role in starting young people down the path of related sciences.[D]Zoos save people trips to wilderness areas and thus contribute to wildlife conservation.[E]For wild animals that cannot be returned to their natural habitats,zoos offer the best alternative.[F]Zoos should have been closed down as they prioritize money making over animals’wellbeing.[G]Marris distorts our findings which actually prove that zoos serve as an indispensable link between man andnature.Part CDirections:Read the following text carefully and then translate the underlined segments into Chinese.Your translation should be written neatly on ANSWER SHEET.(10points)The Man Who Broke Napoleon’s Codes-Mark UrbanBetween1807and1814the Iberian Peninsula(comprising Spain and Portugal)was the scene of a titanic and merciless struggle.It took place on many different planes:between Napoleon’s French army and the angry inhabitants;between the British,ever keen to exacerbate the emperor’s difficulties,and the marshals sent from Paris to try to keep them in check;between new forces of science and meritocracy and old ones of conservatism and birth.(46)It was also,and this is unknown even to many people well read about the period,a battle between those who made codes and those who broke them.I first discovered the Napoleonic cryptographic battle a few years ago when I was reading Sir Charles Oman’s epic History of the Peninsular War.In volume V he had attached an appendix,The Scovell Ciphers.(47)It listed many documents in code that had been captured from the French army of Spain,and whose secrets had been revealed by the work of one George Scovell,an officer in British headquarters.Oman rated Scovell’s significance highly,but at the same time,the general nature of his History meant that(48)he could not analyze carefully what this obscure officer may or may not have contributed to that great struggle between nations or indeed tell us anything much about the man himself.I was keen to read more,but was surprised to find that Oman’s appendix, published in1914,was the only considered thing that had been written about this secret war.I became convinced that this story was every bit as exciting and significant as that of Enigma and the breaking of German codes in the Second World War.The question was,could it be told?Studying Scovell’s papers at the Public Record Office,London,I found that he had left an extensive journal and copious notes about his work in the Peninsula.What was more,many original French dispatches had been preserved in this collection,which I realized was priceless.(49)There may have been many spies and intelligence officers during the Napoleonic Wars,but it is usually extremely difficult to find the material they actually provided or worked on.Furthermore,Scovell’s story involved much more than just intelligence work.His status in Lord Wellington’s headquarters and the recognition given to him for his work were all bound up with the class politics of the army at the time.His tale of self-improvement and hard work would make a fascinating biography in its own right,but represents something more than that.(50)Just as the code breaking has its wider relevance in the struggle for Spain,so his attempts to make his way up the promotion ladder speak volumes about British society.The story of Wellington himself also gripped me.Half a century ago his campaigns were considered a central part of the British historical mythology and spoon-fed to schoolboys.More recently this has not been the case, which is a great shame.A generation has grown up.SectionⅢWritingPart AWrite an email to a professor at a British university,inviting him/her to organize a team for the international innovation contest to be held at your university.You should write about100words on the ANSWER SHEET.Do not use your own name in the e“Li Ming”instead.(10points)Part BWrite an essay of160-200words based on the following picture below.In your essay,you should1)describe the picture briefly,2)explain its intended meaning and3)give your comments.You should write neatly on the ANSWER SHEET.(20points)2022年全国硕士研究生入学统一考试英语（一）试题参考答案完形填空1.[A]coined2.[C]compared3.[D]though4.[C]hinted at5.[D]differs6.[B]evidence7.[C]argued8.[B]forming9.[A]analogous10.[D]even11.[C]perspective12.[B]reducing13.[A]However14.[C]superficially15.[B]level16.[D]added17.[A]chances18.[A]danger19.[D]recognizes20.[B]poor阅读理解Text121.[A]maintaining their plastic items22.[B]improperly shaped23.[D]prevent them from further damage24.[D]challenging25.[B]has profound historical significanceText226.[C]reassess the necessity of college education27.[B]the shrinking value of a degree28.[C]Employers are taking a realistic attitude to degrees。

2024年全国硕士研究生招生考试英语一真题考研英语一

2024年全国硕士研究生入学统一考试英语(一)试题Section I Use of EnglishDirections:Read the following text.Choose the best word(s) for each numbered blank and mark A,B,C or D on the ANSWER SHEET.(10 points)There's nothing more welcoming than a door opening for you. 1 the need to be touched to open or close, automatic doors are essential in 2disabled access to buildings and helping provide general3to commercial buildings.Self-sliding doors began to emerge as a commercial product in 1960 after being invented six years4by Americans Dee Horton and Lew Hewitl. They5as a novelty feature, but as their use has grown, their 6 have extended within our technologically advanced world.Particularly7in busy locations or during times of emergency, the doors8crowdmanagement by reducing the obstacles put in people's way.9 making access both in and out of buildings easier for people, the difference in the way many of these doors open helps reduce the total area10 by them. Automatic doors often open to the side, with the panels sliding across one another. Replacing swing doors, these 11 smaller buildings to maximise the usable space inside without having to12 the way for a large, sticking-out door. There are many different types of automatic door, with each13 specific signals to tell them when to open.14 these methods differ, the main15 remain the same.Each automatic door system 16 the light, sound weight or movement in their vicinity as a signal to open. Sensor types are chosen to 17 the different environments they are needed in.18,a busy street might not19 a motion-sensored door, as it would constantly be opening for passers-by. A pressure sensitive mat would be more20 to limit the surveyed area.1.[A]Through [B]Despite [C]Besides [D]Without2.[A]revealing [B]demanding [C]improving[D]tracing3.[A]experience [B]convenience[C]guidance [D]reference4.[A]previously[B]temporarily [C]successively [D]eventually5.[A]held on [B]started out[C]settled down [D]went by6.[A]relations [B]volumes [C]benefits[D]sources7.[A]useful[B]simple [C]flexible [D]stable8.[A]call for [B]yield to [C]insist on [D]act as9.[A]As well as[B]In terms of [C]Thanks to [D]Rather than10.[A]connected[B]shared [C]represented [D]occupied11.[A]allow[B]expect [C]require [D]direct12.[A]adopt [B]lead [C]clear[D]change13.[A]adapting te [B]deriving from [C]relying on[D]pointing at14.[A]Once [B]Since [C]Unless [D]Although15.[A]records [B]positions [C]principles[D]reasons16.[A]controls [B]analyses[C]produces [D]mixes17.[A]decorate [B]compare [C]protect [D]complement18.[A]In conclusion [B]By contrast [C]For example[D]Above all19.[A]identify [B]suit[C]secure [D]include20.[A]appropriate[B]obvious [C]impressive [D]delicateSection II Reading ComprehensionPart ADirections:Read the following four texts. Answer the questions below each text by choosing A,B,C or D. Mark your answers on the ANSWER SHEET.(40 points)Text 1Nearly 2000 years ago, as the Romans began to pull out of Scotland, they left behind a curious treasure:10 tons of nails, nearly a million of the things. The nail hoard was discovered in 1960 in a four-metre-deep pit covered by two metres of gravel.Why had the Romans bunied a million nails? The likely explanation is that the withdrawal was rushed, and they didn't want the local Caledonians getting their hands on 10 tons of weapon-grade iron. The Romans buried the nails so deep that they would not be discovered for almost two millennia.Later civilisations would value the skilled blacksmith's labour in a nail even more than the raw material. As Roma Agrawal explains in her new delightful book Nuts and Bolts, early 17th-century Virginians would sometimes bum down their homes if they were planning to relocate. This was an attempt to recover the valuable nails, which could be reused after sifting the ashes. The idea that one might bum down an entire house just to reclaim the nails underlines how scarce, costly and valuable the simple-seeming technology was.The price of nails fell by 90%between the late 1700s and mid-1900s,as economist Daniel Sichel points out in a research paper. According to Sichel, although the falling price of nails was driven partly by cheaper iron and cheaper energy, most of the credit goes to nail manufactures who simply found more efficient ways to turn steel into nails.Nails themselves have changed over the years, but Sichel studied them because they haven't changed much. Roman lamps and Roman chariots are very different from LED strips and sports cars,but Roman nails are still clearly nails. It would be absurd to try to track the changing price of sports cars since 1695,but to ask the same question of nails makes perfect sense.I make no apology for being obsessed by a particular feature of these objects: their price. I am an economist, after all. After writing two books about the history of inventions, one thing Ive leamt is that while it is the enchantingly sophisticated technologies that get all the hype, it's thecheap technologies that change the world.The Gutenberg printing press transformed civilisation not by changing the nature of writing but by changing its cost-and it would have achieved little without a parallel collapse in the price of surfaces to write on, thanks to an often-overlooked technology called paper. Solar panels had few niche uses until they became cheap; now they are transforming the global energy system.21.The Romans buried the nails probably for the sake of[A]saving them for future use[B]keeping them from rusting[C]letting them grow in value[D]hiding them from the locals22.The example of early 17th-century Virginians is used to[A]highlight the thriftiness of early American colonists[B]illustrate the high status of blacksmiths in that period[C]contrast the attitudes of different civilisations toward nails[D]show the preciousness of nail-making technology at that time23.What played the major role in lowering the price of nails after the late 1700s?[A]Increased productivity.[B]Wider use of new energies.[C]Fiercer market competition.[D]Reduced cost of raw materials.24.It can be leamed from Paragraph 5 that nails[A]have undergone many technological improvements[B]have remained basically the same since Roman times[C]are less studied than other everyday products[D]are one of the world's most significant inventions25.Which of the following best summarises the last two paragraphs?[A]Cheap technologies bring about revolutionary change.[B]Technological innovation is integral to economic success.[C]Technology defines people's understanding of the world.[D]Sophisticated technologies develop from small inventions.Text 2Parenting tips obtained from hunter-gatherers in Africa may be the key to bringing up more contented children, researchers have suggested. The idea is based on studies of communities such as the Kung of Botswana, where each child is cared for by many adults. Kung children as young as four will help to look after younger ones and baby-wearing", in which infants are carried in slings, is considered the norm.According to Dr Nikhil Chaudhary, an evolutionary anthropologist at Cambridge University, these practices, Known as all oparenting, could lead to less anxiety for children and parents.Dr Annie Swanepoel, a child psychiatrist, believes that there are ways to incorporate them into western life. In Germany, one scheme has paired an old people's home with a nursery. The residents help to look after the children, an arrangement akin to alloparenting. Another measure could be encouraging friendships between children indifferent school years to miror the unsupervised mixed-age playgroups in hunter-gatherer communities.In a paper published in the Journal of Child Psychology and Psychiatry, researchers said that the western nuclear family was a recent invention which family broke with evolutionary history. This abrupt shift to an "intensive mothering narrative", which suggests that mothers should manage childcare alone, was likely to have been harmful. "Such narratives can lead to maternal exhaustion and have dangerous consequences, "they wrote.By contrast, in hunter-gatherer societies adults other than the parents can provide almost half of a child's care. One previous study looked at the Efe people of the Democratic Republic of Congo. It found that infants had an average of 14 alloparents a day by the time they were 18 weeks old and were passed between caregivers eight times an hour.Chaudhary said that parents now had less childcare support from family and social networks than during most of humans'evolutionary history,but introducing additional caregivers could reduce stress and maternal depression,which could have a“knock-on"benefit to a child's wellbeing.An infant bom to a hunter-gatherer society could have more than ten caregivers-this contrasts starkly to nursery settings in the UK where regulations call for a ratio of one carer to four children aged two to three.While hunter-gatherer children leamt from observation and imitation in mixed-age playgroups,researchers said that western"instructive teaching",where pupils are asked to sit still,may contribute to conditions such as attention deficit hyperactivity disorder.Chaudhary said that Britain should explore the possibility that older siblings helping their parents“might also enhance their own social development”26.According to the first two paragraph,alloparenting refers to the practice of[A]sharing child care among community members[B]assigning babies to specific adult caregivers[C]teaching parenting details to older children[D]carrying infants around by their parent27.The scheme in Germany is mentioned to illustrate[A]an attempt to facilitate intergenerational communication[B]an approach to integrating alloparenting into western culture[C]the conventional parenting style in western culture[D]the differences between western African ways ofliving28.According to Paragraph 4,the"intensive mothering narrative"_[A]alleviate parenting pressure[B]considerate family relationships[C]results in the child-centered family[D]departs from the course of evolution29.According to paragraph 6,what can we lean about nursery in the UK?[A]They tend to fall short of official requirements.[B]They have difficulty finding enough caregivers.[C]They ought to improve their carer-to-child ratio.[D]They should try to prevent parental depression.30.Which of the following would be the best title?[A]Instructive teaching:a dilemma for anxious parents[B]For a happier family,learn from the hunter-gatherers[C]Mix-aged playgroup,a better choice for lonely children[D]Tracing the history of parenting:from Africa to EuropeText 3Rutkowski is a Polish digital artist who uses classical painting styles to create dreamy fantasy landscapes.He has made illustrations for games such as Sony's Horizon Forbidden West,Ubisoft's Anno,Dungeons&Dragons,and Magic:The Gathering.And he's become a sudden hit in the new world of text-to-image AI generation.His distinctive style is now one of the most commonly used prompts in the new open-source AI art generator Stable Diffusion,which was launched late last month.The tool,along with other popular image-generation AI models,allows anyone to create impressive images based on text prompts.For example,type in"Wizard with sword and a glowing orb of magic fire fights a fierce dragon GregRutkowski,"and the system will produce something that looks not a milion miles away from works in Rutkowski's style.But these open-source programs are built by scraping images from the Internet,often without permission and proper attribution to artists.As a result,they are raising tricky questions about ethics and copyright.And artists like Rutkowski have had enough.According to the website Lexica,which tracks over 10 million images and prompts generated by Stable Diffusion,Rutkowski's name has been used as a prompt around 93,000 times.Some of the world's most famous artists,such as Michelangelo,Pablo Picasso,and Leonardo da Vinci,brought up around 2,000 prompts each or less.Rutkowski's name also features as a prompt thousands of times in the Discord of another text-to-image generator,Midjourney.Rutkowski was initially surprised but thought it might be a good way to reach new audiences.Then he tried searching for his name to see if a piece he had worked on had been published.The online search brought back work that had his name attached to it but wasn't his.“It's been just a month.What about in a year?I probably won't be able to find my work out there because[the internet]will be flooded with AI art,"Rutkowski says."That's concerning."“There is a coalition growing within artist industries to figure out how to tackle or mitigate this,"says Ortiz.The group is in its early days of mobilization,which could involve pushing for new policies or regulation.One suggestion is that AI models could be trained on images in the public domain,and AI companies could forge partnerships with museums and artists,Ortiz says.31.What can be leamed about Rutkowski from the first two paragraphs?[A]He is enthusiastic about AI generation painting.[B]He is popular with the users of an Al art generator.[C]He attracts admiration from other illustrators.[D]He specializes in classical painting digitalization.32.The problem with open-source AI art generators is that they[A]lack flexibility in responding to prompts[B]produce artworks in unpredictable styles[C]make unauthorized use of online images[D]collect user information without consent33.After searching online,Rutkowski found[A]a unique way to reach audiences[B]a new method to identify Al images[C]AI-generated work bearing his name[D]heated disputes regarding his copyright34.According to Ortiz,AI companies are advised to[A]campaign for new policies or regulations[B]offer their services to public institutions[C]strengthen their relationships with AI users[D]adopt a different strategy for Al model training35.What is the text mainly about?[A]Artists'responses to Al art generation.[B]AI's expanded role in artistic creation.[C]Privacy issues in the application of Al.[D]Opposing views on AI development.Text 4The miracle of the Chesapeake Bay lies not in its depths,but in the complexity of its natural construction,the interaction of fresh and saline water and the mix of land and water.The shallows provide homes for hundreds of species while storing floodwaters,filtering pollutants from water,and protecting nearby communities from potentially destructive storm surges.All this was put at great risk late last month,when the US Supreme Court issued a ruling in an Idaho case that provides the EPA far less authority to regulate wetlands and waterways.Specifically,a 5-4 majority decided that wetlands protected by the EPA under it Clean Water Act authority must have a“continuous surface connection”to bodies of water.This narrowing of the regulatory scope was a victory for builders,mining operators and other commercial interests often at odds with environmental rules.And it carries"significant repercussions for water quality and flood control throughout the US,"as Justice Brett Kavanaugh observed.In Maryland,the good news is that there are many state laws in place that provide wetlands protections.But that's a very shortsighted view,particularly when it comes to the Chesapeake Bay.The reality is that water and the pollutants that so often come with it,don't respect state boundaries.The Chesapeake draws from a 64000-square-mile watershed that extends to Virginia,Pennsylvania,New York,West Virginia,the District of Columbia and Delaware.Will thosejurisdictions extend the same protections now denied under Sackett V.EPA?Perhaps some,but all?That seems unlikely.It is too easy,and misleading,to see such court rulings as merely standing up for the rights of land owners when the consequences can be so dire for their neighbors.And it's reminder that they EPA's involvement in the Chesapeake Bay program has long been crucial as the means to transcend the influence of deep-pocketed special interests in neighboring states.Pennsylvania farmers,to use one telling example,aren't thinking about next year's blue crab harvest in Maryland when they decide whether to spread animal waste on their fields,yet the runoff into nearby creeks can have enormous impacts downstream.And so we would also call on state lawmakers from Richmond to Albany to consider reviewing their own wetlands protections and see for themselves the enormous stakes involved.We can't offer them a trip to the Chesapeake Bay model.It's been gone since the 1980s but perhaps a visit to Blackwater National Wildlife Refuge in Dorchester County where American bald eagles fly over tidal marshes so shallow you could not paddle a boat across them but teaming with aquatic life.It's worth the scenic drive.36.The Chesapeake Bay is described in Paragraph 1 as[A]a value natural environment[B]a controversial conservation area[C]a place with commercial potential[D]a headache for nearby communities37.The U.S.Supreme Court's ruling in the Idaho case[A]reinforces water pollution control[B]weakens the EPA's regulatory power[C]will end conflicts among local residents[D]may face opposition from mining operators38.How does the author feel about the future of the Chesapeake Bay?[A]Worried.[B]Puzzled.[C]Relieved[D]Encouraged.39.What can be inferred about the EPA's involvement in the Chesapeake BayProgram?[A]It has restored the balance among neighboring jurisdictions.[B]It has triggered a radical reform in commercial fisheries.[C]It has set a fine example of respecting state authorities.[D]It has ensured the coordination of protection efforts.40.The author holds that the state lawmakers should[A]be cautious about the influence of landowners[B]attach due importance to wetlands protections[C]recognize the need to expand wildlife refugesPart BDirections:Read the following comments on a report about American museums returning artifacts to their countries of origin and a list of statements summarizing the comments.Choose the best statement from the list A-G for each numbered name(41—45).There are two extra choices which you do not need to use.Mark your answers on the ANSWER SHEET.(10 points)(41)HannabSimply,there are people in Nigeria who cannot travel to the Smithsonian Institution to see that part of their history and culture represented by the Benin Bronzes.These should be available to them as part of their cultural heritage and history and as a source of national pride.There is no good reason that these artifacts should be beyond the ordinary reach of the educational objectives or inspiration of the generations to which they were left.They serve no purpose in a museum in the United States or elsewhere except as curious objects.They cannot be compared to works of art produced for sale which can be passed from hand to hand and place to place by purchase.(42)BuckWe know very exact reproductions of artwork can be and are regularly produced.Perhaps museums and governments might explore some role for the use of nearly exact reproductions as a means of resolving issues relating to returning works of art and antiquities.The context of any exhibit is more important to me than whether the object being displayed is 2,000 years old or 2 months old.In many cases the experts have a hard time agreeing on what is the real object and what is a forgery.Again,the story an exhibit is trying to tell is what matters.The monetary value of the objects on display is a distant second place in importance.(43)SaraWhen visiting the Baltimore Museum of Art,I came across a magnificentlSth-century Chinese sculpture.It inspired me to learm more about the culture that it represented.Artifacts in museums have the power to inspire,and perhaps spark that need to learn and understand the nature of their creators.Having said that,I do feel that whatever artifacts find their way to public museums should,in fact,be sanctioned as having been obtained on loan,legally purchased,or obtained by treaty.Stealing artifacts from other peoples'cultures is obscene;it robs not only the physical objects,but the dignity and spirit of their creators.(44)VictorAncient art that is displaced in foreign countries should be returned.…(缺失)(45)JuliaTo those of you in the comments section,by all means,who are having strong feeling about artifacts being removed from cities in the US and Britain,I would ask you to consider…(缺失)[A]It is clear that countries of origin have never been compensated for stolen artifacts.[B]It is a flawed line of reasoning to argue against returning artifacts to their countries of origin.[C]Museum visitor can still learn as much from artifacts copies after the originals are returmed.[D]Reproductions,even if perfectly made,cannot take the place of the authentic objects.[E]The real value of artifacts can only be recognized in their countries of origin rather than anywhere else[F]Ways to get artifacts from other countries must be decent and lawful.[G]Concern over security is no excuse for refusing to return artifacts to their countries of origin. 参考答案：41.E 42.C 43.F 44.G 45.BPart CDirections:Read the following text carefully and then translate the underlined segments into Chinese.Your translation should be written clearly on the ANSWER SHEET.(10 points)“Elephants never forget”—or so they say—and that piece of folklore seems to have some foundation.The African savanna elephant also known as the African bush elephant,is distributed across 37 African countries.(46)They sometimes travel more than sixty miles to find food or water,anc are very good at working out where other elephants are—even when they are out of ing tracking devices,researchers have shown that they have"remarkable spatial acuity",when finding their way to waterholes,they headed off in exactly the right direction,on one occasion from a distance of roughly thirty miles.What is more,they almost always seem to choose the nearest water hole.(47)The researchers are convinced that the elephants always know precisely where they are in relation to all the resources they need,and can therefore take shortcuts,as well as following familiar routes.Although the cues used by African elephants for long-distance navigation are not yet understood,smell may well play a part.Elephants are very choosy eaters,but until recently litle was known about how they selected their food.(48)One possibility was that they merely used their eyes and tried out the plants they found,but that would probably result in a lot of wasted time and energy,not least because their eyesight is actually not very good.(49)The volatile chemicals produced by plants can be carried a long way,and they are very characteristic:Each plant or tree has its own particular odor signature.What is more,they can be detected even when they are not actually visible.New research suggests that smell is a crucial factor in guiding elephants—and probably other herbivores—to the best food resources.The researchers first established what kinds of plant the elephants preferred either to eat or avoid when foraging freely.They then set up a“food station”experiment,in which they gave elephants a series of choices based only on smell.(50)The experiment showed that elephants may well use smell to identify patches of trees that are good to eat,and secondly to assess the quality ofthe trees within each patch.Free-ranging elephants presumably also use this information to locate their preferred food.参考译文：(46)它们有时跋涉六十多英里寻找食物或水，并且非常善于寻找其他大象的位置——即使它们不在视线范围内。

全国硕士研究生入学考试政治试卷及答案

全国研究生入学考试政治试题参考答案一、单项选择题：1.世界上惟一不变的是变。

这一论断的含义是A.变是世界的本原B.世界上只有变，没有不变C.变是绝对的，不变是相对的D.变与不变是绝对对立的答案 C【分析】这道单项选择题，考查的知识点是对唯物辩证法关于发展、变化的理解和确认。

世界上没有永恒存在着的事物。

一切事物都是运动、变化和发展的。

一切事物都有其产生、发展和转化为其他事物的历史。

一切事物都有它的过去、现在和未来。

因此，在辩证法看来，一切事物都处在发生、发展和灭亡的过程中，凡是在历史上产生的都要在历史上灭亡，任何事物都不可能永恒地存在。

整个物质世界就是永恒发展变化着的世界。

换句话说，世界上唯一不变的是变化，即“变是绝对的，不变是相对的”(C项)。

据此分析题中给出的四个选项：A项(变是世界的本原)明显是错误的，因为世界的本质是物质的，变化是世界存在的状态，而不是世界的本质；B项和D项谈的是对变化的理解，但是都犯了形而上学的错误，这样将A、B、D三项排除，只有C项才是正确选项。

该题是考生应该掌握的最基本的原理，难度不大，是必得之分。

如果有的考生丢分，会是误选B项。

2.“只有音乐才能激起人的音乐感；对于没有音乐感的耳朵说来，最美的音乐也毫无意义”。

这表明A.人的认识是主体与客体相互作用的过程和结果B.人的感觉能力决定认识的产生和发展C.人的认识能力是由人的生理结构决定的D.事物因人的感觉而存在答案 A【分析】这是一道事实辨析选择题，考查的知识点是对认识的本质、主体在认识中的作用的理解和把握。

认识是主体对客体的反映，任何认识都是主体在与客体的相互作用中对客体的反映。

而主体对客体的反映是一个能动的创造性的过程。

认识是主体和客体相互作用的过程和结果，既有客体对主体的作用，更有主体对客体的作用。

主体人是具有复杂结构和进行活动的社会性的人，它在反映客体的过程中，必然会动用其内部结构的所有功能，对所反映对象的内容进行选择、整理、改造、解释、猜想等等，因此，不仅能对客观对象进行直观的摹写，而且能对客观对象作出抽象和概括的反映；不仅能反映事物当下的样子，而且能反映它由于人的改造活动而可能成为的样子。

2023年研究生考试英语一真题

2023年全国硕士研究生招生考试英语（一）试题Section Ⅰ Use of EnglishDirections：Read the following text. Choose the best word(s) for each numbered blank and mark A, B, C or D on the ANSWER SHEET.(10 points)Caravanserais were roadside inns that were built along the Silk Road in areas including China, North Africa and the Middle East. They were typically 1 outside the walls of a city or village and were usually funded by local governments of 2 .The word ‘Caravanserai’ is a 3 of the Persian words ‘karvan’, which means a group of travellers or a caravan, and seray, a palace or enclosed building. The term caravan was usedto 4 groups of people who travelled together across the ancient network for safety reasons, 5 merchants, travellers or pilgrims. From the 10th century onwards, as merchant and travel routes became more developed, the 6 of Caravanserais increased and they served as a safe place for people to rest at night. Travellers on the Silk Road 7 the possibility of being attacked by thieves or being 8 to extreme weather conditions. For thisreason, Caravanserais were strategically placed 9 they could be reached in a day’s travel time.Caravanserais served as an informal 10 point for thevarious people who travelled the Silk Road. 11 , those structures became important centres for cultural 12 and interaction with travellers sharing their cultures, ideas and beliefs, 13 talking knowledge with them, greatly 14 the development of several civilisations.Caravanserais were also an important marketplace for commodities and 15 in the trade of goods along the Silk Road. 16 , it was frequently the first stop for merchants looking to sell their wares and 17 supplies for their own journeys. It is 18 that around 12,000 to 15,000 caravanserais were built along the Silk Road, 19 only about 3,000 are known to remain today, many of which are in 20 .1. A. displayed B. occupied C. located D. equipped2. A. privately B. regularly C. respectively D. permanently3. A. definition B. transition C. substitution D. combination4. A. classify B. record C. describe D. connect5. A. apart from B. instead of C. such as D. along with6. A. construction B. restoration C. impression D. evaluation7. A. doubted B. faced C. accepted D. reduced8. A. assigned B. subjected C. accustomed D. opposed9. A. so that B. even if C. now that D. in case10. A. talking B. starting C. breaking D. meeting11. A. By the way B. On occasion C. In comparison D. As a result12. A. heritage B. revival C. exchange D. status13. A. with regard to B. in spite of C. as well as D. in line with14. A. completing B. influencing C. resuming D. pioneering15. A. aided B. invested C. failed D. competed16. A. Rather B. Indeed C. Otherwise D. However17. A. go in for B. stand up for C. close in on D. stock up on18. A. believed B. predicted C. recalled D. implied19. A. until B. because C. unless D. although20. A. ruins B. debt C. fashion D. seriesSection Ⅱ Reading ComprehensionPart ADirections：Read the following four texts. Answer the questions after each text by choosing A, B, C or D. Mark your answers on the ANSWER SHEET. (40 points)Text 1The weather in Texas may have cooled since the recent extreme heat, but the temperature will be high at the State Board of Education meeting in Austin this month as officials debate how climate change is taught in Texas schools.Pat Hardy, who sympathized with views of the energy sector, is resisting the proposed change to science standards for pre-teen pupils. These would emphasize the primacy of human activity in recent climate change and encourage discussion of mitigation measures.Most scientists and experts sharply dispute Hardy’s views. "They casually dismiss the career work of scholars and scientists as just another misguided opinion." says Dan Quinn, senior communications strategist at the Texas Freedom Network, anon-profit group that monitors public education, "What millions of Texas kids learn in their public schools is determined too often by the political ideology of partisan board members, rather than facts and sound scholarship."Such debate reflects fierce discussions across the US and around the world, as researchers, policymakers, teachers and students step up demands for a greater focus on teaching about the facts of climate change in schools.A study last year by the National Center for Science Education, a non-profit group of scientists and teachers, looking at how state public schools across the country address climate change in science classes, gave barely half of US states a grade B+ or higher. Among the 10 worst performers were some of the most populous states, including Texas, which was given the lowest grade (F) and has a disproportionate influence because its textbooks are widely sold elsewhere.Glenn Branch, the centre's deputy director, cautions that setting state-level science standards is only one limited benchmark in a country that decentralises decisions to local school boards. Even if a state is considered a high performer in its science standards, "that does not mean it will be taught”, he says.Another issue is that while climate change is well integrated into some subjects and at some ages--such as earth and space sciences in high schools it is not as well represented in curricula for younger children and in subjects that are more widely taught, such as biology and chemistry. It is also less prominent in many social studies courses.Branch points out that, even if a growing number of official guidelines and textbooks reflect scientific consensus on climate change, unofficial educational materials that convey more slanted perspectives are being distributed to teachers. They include materials sponsored by libertarian think-tanks and energy industry associations.21. In paragraph 1, the weather in Texas is mentioned toA. forecast a policy shift in Texas schools.B. stress the consequences of climate change.C. indicate the atmosphere at the board meeting.D. draw the public's attention to energy shortages.22. What does Quinn think of Hardy?A. She exaggerates the existing panic.B. She denies the value of scientific work.C. She shows no concern for pre-teens.D. She expresses self-contradictory views.23. The study mentioned in Paragraph 5A. climate education is insufficient at state public schools.B. policy makers have little drive for science education.C. Texas is reluctant to rewrite its science textbooks.D. environmental teaching in some states lacks supervision.24. According to Branch, state-level science standards in the USA. call for regular revision.B. require urgent application.C. have limited influence.D. cater to local needs.25. It is implied in the last paragraph that climate change teaching in some schoolsA. agree to major public demands.B. reflects teachers' personal biases.C. may misrepresent the energy sector.D. can be swayed by external forces.Text 2Communities throughout New England have been attemptingto regulate short-term rentals since sites like Airbnb took off in the 2010s. Now with record-high home prices and historically low inventory, there’s an increased urgency in such regulation, particularly among those who worry that developers will come in and buy up swaths of housing to flip for a fortune on the short-term rental market.In New Hampshire, where the rental vacancy rate has dropped below 1 percent, housing advocates fear unchecked short-term rentals will put further pressure on an already strained market. The State Legislature recently voted against a bill that would’ve made it illegal for towns to create legislation restricting short-term rentals.“We are at a crisis level on the supply of rental housing,” saidNick Taylor, executive director of the Workforce Housing Coalition of the Greater Seacoast. Without enough affordable housing in southern New Hampshire towns, “employers are having a hard time attracting employees, and workers are having a hard time finding a place to live,” Taylor said.However, short-term rentals also provide housing for tourists, pointed out Ryan Castle, CEO of a local association of realter. “Alot of workers are servicing the tourist industry, and the tourism industry is serviced by those people coming in short term,” Castle said, “and so it’s a cyclical effect.”Short-term rentals themselves are not the crux of the issue, said Keren Horn, an expert on affordable housing policy. “I think individuals being able to rent out their second home is a good thing. If it’s their vacation h ome anyway, and it’s just empty, why can’t you make money off it?” Horn said. Issues arise, however, when developers attempt to create large-scale short-term rental facilities—de facto hotels—to bypass taxes and regulations. “I think the question is, shoul dn’t a developer who’s really building a hotel, but disguising it as not a hotel, be treated and taxed and regulated like a hotel?” Horn said.At the end of 2018, governor Charlie Baker of Massachusetts signed a bill to rein in those potential investor-buyers. The bill requires every rental host to register with the state mandates they carry insurance, and opens the potential for local taxes on top of a new state levy. Boston took things even further, requiring renters to register with the city’s Inspection al Services Department.Horn said similar registration requirements could benefit struggling cities and towns, but “if we want to make a change in the housing market, the main one is we have to build a lot more.”26. Which of the following is true of New England?A. Its housing supply is at a very low level.B. Its communities are in need of funding.C. Its rental vacancy rate is going up slowly.D. Its home prices are under strict control.27. The bill mentioned in Paragraph 2 was intended toA. curb short-term rental speculation.B. ensure the supply of cheap housing.C. punish illegal dealings in housing.D. allow a free short-term rental market.28. Compared with Castle, Taylor is more likely to supportA. further investment in local tourism.B. an increase in affordable housing.C. strict management of real estate agents.D. a favorable policy for short-term workers.29. What does Horn emphasize in Paragraph 5?A. The urgency to upgrade short-term rental facilities.B. The efficient operation of the local housing market.C. The necessity to stop developers from evading taxes.D. The proper procedures for renting out spare houses.30. Horn holds that imposing registration requirements isA. an irrational decision.B. an unfeasible proposal.C. an unnecessary measure.D. an inadequate solution.Text 331. The author mentions two books in paragraph to presentA. An ongoing conflictB. An intellectual conceptC. A prevailing sentimentD. A literary phenomenon32. why did Waterstones shops retire PRH books to their relevant sections?A. To make them easily noticeableB. To comply with PRH’s requirementC. To respond to PRH’s business moveD. To arrange them in systematic way33. what message does the spokesperson for Waterstones seem to convey?A. Their customers remain loyalB. The credit limit will be removed.C. Their stock is underestimated.D. The book market is rather slack【33】A. Their customers remain loyal34. what can be one consequence of the current dispute?A. Sales of books by mid-list PRH writers fall off considerably.B. Lesser-known PRH writers become the target of criticismC. Waterstones staff hesitate to promote big-name author’s books.D. Waterstones branches suffer a severe reduction in revenue.35. Which of the following statem ents best represents Lownie’s view?A. Small publishers ought to stick together.B. Big publishers will lose their dominance.C. The publishing industry is having a hard time.D. The merger of publishers is a worrying trend.36. According Paragraph 1, the careers of scientists can be determined byA. how many citations their works contain.B. how many times their papers are cited.C. the prestige of the people they work with.D. the status they have in scientific circles.37. The support service consultancies tend toA. recommend journals to their clients.B. list citation patterns for their clients.C. ask authors to include extra citations.D. advise contributors to cite each other.38. The function of the “milk cow” journals is toA. boost citation counts for certain authors.B. help scholars publish articles at low cost.C. instruct first-time contributors in citation.D. increase the readership of new journals.39. What can be learned about Scopus from the last two paragraphs?A. It fosters competition among citation providers.B. It has the capability to identify suspicious citations.C. It hinders the growth of “international” journals.D. It is established to prevent citation manipulation.40. What should an author do to deal with citation manipulators?A. Take legal action.B. Demand an apology.C. Seek professional advice.D. Reveal their misconduct.Part B[A] This year marks the 150th anniversary of a series of Yellowstone photographs by the renowned landscape photographer William Henry Jackson. He captured the first-ever shots of iconic landmarks such as the Tetons, Old Faithful and the Colorado Rockies. Jackson snapped them on a late 19th-century expedition through the Yellowstone Basin that was conducted by the head of the U.S. Geological and Geographical Survey of the Territories, Ferdinand V. Hayden. The team included a meteorologist, a zoologist, a mineralogist, and an agricultural statistician.[B] Two centuries ago, the idea of preserving nature, rather than exploiting it, was a novel one to many U.S. settlers. One of the turning points in public support for land conservation efforts — and recognizing the magnificence of the Yellowstone region in particular — came in the form of vivid photographs.[C] As an effective Washington operator, Hayden sensed that he could capitalize on the expedition’s stunning visuals. He asked Jackson to print out large copies and distributed them, along with reproductions of Moran’s paintings, to each member of Congress. “The visualization, particularly those photo graphs, really hit homethat this is something that has to be protected,” says Murphy.[D] Throughout the trip, Jackson juggled multiple cameras and plate sizes using the collision process that involved coating the plates with a chemical mixture, exposing them and developing the resulting images with a portable darkrooms. The crude technique required educated guesses on exposures times, and involved heavy, awkward equipment--several men had to assist in its transportation. Despite these challenges, Jackson captured dozens of striking photos, ranging from majestic images like his now-famous snapshot of old faithful, to casual portraits of expedition members that the camp. While veterans of previous expeditions had written at length about stunning sights, these vivid photographs were another thing entirely.[E] The well-documented Yellowstone journey officially began in Ogden, Utah on June 8, 1871. Over nearly four months, dozens of men made their way on horseback into Montana and traversed along the Yellowstone River and around Yellowstone Lake. That fall, they concluded the survey in Fort Bridger, Wyoming.[F] Though Native Americans (and later miners and fur trappers) had long recognized the area’s riches, most Americans did not. That’s why Hayden’s expeditio n aimed to produce a fuller understanding of the Yellowstone River region, from its hot springsand waterfalls to its variety of flora and fauna. In addition to the entourage of scientists, the team also included artists: Painter Thomas Moran and photographer William Henry Jackson were charged with capturing this astounding natural beauty and sharing it with the world.[G] The bill proved largely popular and sailed through Congress with large majorities in favor. In quick succession, the Senate and House passed legislation protecting Yellowstone in early 1872. [H] Perhaps most importantly, these images provided documentary evidence of the park’s sights that later made its way to government officials. Weeks after completing the expedition, Hayden collected hi s team’s observations into an extensive report aimed at convincing senators and representatives, along with colleagues at government agencies like the Department of the Interior, that Yellowstone ought to be preserved (and that his department deserved additional funds).41 A 42 E 43 H 44 45【41】B首先排除AEH选项，其次，C、D中出现了Jackson 非全名，所以排除，F中出现Hayden 非全名排除，G the bill 表示前面出现过，排除，H perhaps most importantly, these images 可知前面出现过images，可排除，答案只能是B。

2023年全国硕士研究生入学考试真题

2023年全国硕士研究生入学考试真题第一部分：语言知识运用（共两节，共40分）第一节：语法和词汇知识（共20小题；每小题1分，共20分）从A、B、C、D四个选项中，选出可以填入空白处的最佳选项，并在答题卡上将该项涂黑。

1. --Did you send an invitation to John?--Yes, I ________ him to join us for dinner tomorrow.A. have askedB. askC. askedD. am asking2. The naughty boy was caught when he _______ into the neighbor's garden.A. sneakedB. had sneakedC. sneaksD. was sneaking3. It was my first time to see the sea, and I was totally _________ by its beauty.A. fascinatedB. markedC. postedD. startled4. --Michael, you've been working on this for hours. Why not take a break?--I can't stop now. I ______ this research report by tomorrow morning.A. must finishB. must have finishedC. had to finishD. would finish5. The book I bought online arrived yesterday, but ______ of the pages were torn.A. bothB. manyC. fewD. some6. Mary said she _______ to the party, but she hasn't shown up yet.A. will comeB. would comeC. had comeD. came7. --Do you need any help with your luggage?--No, thanks. I ________ it myself.A. carryB. will carryC. carriedD. am carrying8. I'm sorry, the restaurant is quite crowded at the moment. We________ a table for you.A. are reservingB. were reservingC. have reservedD. had reserved9. She didn't feel like ________ out in such hot weather, so she stayed at home.A. goB. to goC. goesD. going10. --Can I join the club now?--According to the rules, you ________ be a student of this university for at least six months.A. mustB. mayC. needD. shall11. _______ to the party this Saturday, remember to bring some snacks along.A. GoingB. When goingC. GoD. If you go12. The old couple ________ different views on how to spend their retirement.A. holdB. heldC. are holdingD. are held13. I can't find my keys anywhere. They ________ have been stolen.A. wouldB. mustC. shouldD. might14. --Why didn't Jack attend the meeting this morning?--He ________ to reflect on his recent mistakes.A. is askedB. was askedC. has askedD. had been asked15. In many cultures, it is considered ________ to express your emotions loudly in public.A. rudeB. politerC. rudestD. the rude16. There were no empty seats left, so we ___________ to stand during the entire concert.A. hadB. couldC. mustD. were able17. --I really appreciate what you've done for me.--__________.A. Don't mention itB. You're welcomeC. It doesn't matterD. I'm all right18. The newly-built theater is said to be the _______ in the city.A. largeB. largerC. largestD. more large19. --John, can you help me find my phone?--Of course. ________ you see it last time?A. Where willB. Where hadC. Where didD. Where have20. --Do you know Dr. Smith?--Oh, yes. He's the professor ________ lecture I attended last week.A. whoseB. whichC. whomD. that第二节：完形填空（共20小题；每小题1.5分，共30分）阅读下面短文，从短文后各题所给的四个选项（A、B、C和D）中，选出可以填入空白处的最佳选项，并在答题卡上将该项涂黑。

年全国硕士研究生统一入学考试自命题试题

一个周末的下午，亨利和他的朋友及同事迪安一起打高尔夫球。他了解到他所在的部门新雇了一位刚从大学毕业的程序编制分析员。尽管亨利是个好脾气的人，但他听说这新来者的起薪仅比他现在的工资少美元时，不禁发火了。
亨利找到了人事部主任爱德华，爱德华说，确有这么回事。但他试图解释公司的处境；“亨利，编程分析员的市场相当紧俏。为使公பைடு நூலகம்能吸引合格的人员，我们不得不提供较高的起薪。我们非常需要增加一名编程分析员，因此，我们只能这么做。”
年全国硕士研究生统一入学考试自命题试卷********************************************************************************************
学科、专业名称：工业工程
研究方向：所有方向
考试科目名称：管理学卷
考生注意：所有答案必须写在答题纸（卷）上，写在本试卷上一律不给分。
问题：
．保罗作为一位领导者的权力来源是什么？（分）
．这个案例更好地说明了领导的行为理论，还是领导的权变理论？为什么？（分）
．保罗在纽约取得成功的策略，为什么在达拉斯没能成功？其影响因素有哪些？（分）
案例二亨利的困惑
亨利已经在数据系统公司工作了年。他从普通编程员升到了资深的程序编制分析员。他对自己所服务的这家公司相当满意，很快被工作中的创造性要求所激励。
保罗在年初被提升为达拉斯的经营合伙人。他采取了帮助他在纽约工作时取得显著成效的同种富有进取心的管理方式。他马上更换了几乎全部的名专业人员，并制定了短期的和长期的客户开发计划。职员人数增加的相当快，为的是确保有足够数量的员工来处理预期扩增的业务。很快，办事处有了约名专业人员。
但在纽约成功的管理方式并没有在达拉斯取得成效。办事处在一年时间内就丢掉了最好的两个客户。保罗马上认识到办事处的人员过多了，因此决定解雇前一年刚招进来的名员工，以减少开支。

大学硕士研究生入学考试试题(样卷)

大学硕士研究生入学考试试题（样卷）招生专业：翻译学科目名称：英汉互译（笔译）（考试时间3小时，满分150分，全部写在答题纸上，答在试题页上无效）I.Translate the following passage into Chinese and write yourtranslation on the answer sheet. (50 points)Between Demond’s excursions he like s to accompany me to the Chinese Theatre, of which I had become a fervent votary. Peking is as much the home of the Chinese Theatre as Hollywood is of the films. I had invited many friends to performances that I thought wonderful, but after a very short time they pleaded earache, headache or frank boredom and beat a hasty retreat. Desmond was one of the rare exceptions: he understood instinctively the Chinese drama was the most vital of the traditional arts.A Pekingese enthusiast is mainly concerned with the vocal side of the drama: he goes to the theater to enjoy sustained and difficult flights of falsetto (假声) singing in a sociable atmosphere. The plot, which always drives home a sound moral, is a subsidiary attraction, and the same plays are performed year in year out to packed houses of listeners as critical as the audience of an opera in Italy. As for me, I was first struck by parallels with the Elizabethan stage.The Chinese Theatre provided that ideal synthesis of the arts which I had always been seeking, a synthesis which only the Russian Ballet had approached in Europe. It was a harmonious combination of dialogue, singing, dancing and acrobatics. The beauty of costume, make-up and movement, the subtlety of the pantomime（哑剧）, were thrilling even when one was ignorant of the plot and indifferent to the music. The technique of Chinese actors made scenery superfluous. Everything on this stage was simplified and intensified.The stage itself projected squarely into the audience without a drop curtain, though an embroidered curtain might hang at the back between the two doors for actors’ entrances and exits, and the few stage properties were symbolic. On this bare jutting platform only the comedians were allowed to be clumsy; all the others, who specialized in a certain type of role from which they never deviated, had to move with dignity, elegance and grace. In the popular drama, which had been perfected in Peking since the eighteen century, I preferred the ‘military’ or chronicle plays reviving remote periods of Chinese history in a shrill, vivid, stylized succession of tableaux（舞台造型）, teeming with characters in sumptuous costumes who performed dazzling feats in mimic battle, prodigies of swift, supple and precise sword-play, to the staid and sentimental ‘civil’ plays, with their demure her oines, so correctly Confucian and tantalizingly deliberate, and their righteous elders warbling into the most improbableof beards.The rhythmic beauty of the battle-scenes was intoxicating; they heightened one’s blood pressure. And the technical resources of the actors seemed infinite. Being peaceable by nature, the Chinese reserved their few bellicose（好战的）strains for the theatre, where they became sublimated and polished by art. Sipping tea and nibbling melon seeds, they blandly watched the evolution of generals more ferocious than anything outside the jungle. To the clash of gongs, each carrying his favourite weapon, as decorative as it could be dangerous, the generals in gorgeous coats of mail（盔甲）strutted up like giant fighting cocks with vast plumes in their helmets, showing the thick white soles of buskin-like boots as they advanced in perfect tempo; then they juggled with their weapons to exhibit their skills. No two were alike in costume or make-up. The generals formed ranks while the supreme commander swaggered into their midst. In voices of thunder they proclaimed that they were wolves, tigers and leopards eager for the fray. The supreme commander boasted that his army of heroes would sweep his enemies off the face of the earth. (598)II.Translate the following passage into English and write your translation on the answer sheet. (50 points).大宛之迹*，见*自张骞。

2023全国硕士研究生招生考试数学试题(数学二)真题解析

2023 考研数学二真题及解析一、选择题：1~10 小题，每小题 5 分，共 50 分.在每小题给出的四个选项中，只有一个选项是最符合题目要求的，请将所选项前的字母填在答题纸指定位置上.1．曲线1ln e 1y x x=+ −的斜渐近线方程为（）. （A ）ey x =+（B ）1ey x =+（C ）yx = （D ）1ey x =−【答案】（B ）【解析】方法1. 1ln e 11limlim x x y k x x →∞→∞=+==− ()()11lim lim ln e 1lim ln e ln 111e 1x x x b y x x x x x →∞→∞→∞=−=+−=++− −−()11lim e 1ex xx →∞=−故曲线的斜渐近线方程为1ey x =+．故选（B ）方法2. ()()11ln e 11ln 1e 1e 1y x x x x=+=++−−()11ln 1e 1e x x x x α =++=++ −，其中lim 0x α→∞=，故1e y x =+为曲线的斜渐近线. 【评注】由()11lim ln 1e 1e x x x →∞+= − ，知()11ln 1e 1ex x α +=+ − 【评注】1.由()11lim ln 1e 1e x x x →∞ += − ，知()11ln 1e 1e x x α +=+ −2.本题属于常规题：《基础班》《强化班》的例子不再对应列举，《答题模版班》思维定势19【例13】2.函数() 0,()1cos ,0.x f x x x x ≤=+>的一个原函数是( )(A) ), 0,()(1)cos sin ,0.x x F x x x x x −≤= +−>(B))1, 0,()(1)cos sin ,0.x x F x x x x x +≤= +−>(C) ), 0,()(1)sin cos ,0.x x F x x x x x −≤= ++>(D))1, 0,()(1)sin cos ,0.x x F x x x x x +≤= ++>【答案】 (D) .【分析】本题主要考查原函数的概念,分段函数不定积分的求法以及函数可导与连续的关系.【详解】由于当0x <时，)1()lnF xx x C ==++∫当0x >时，()()2()1cos d 1sin cos F x x x x x x x C =+=+++∫ 由于()F x 在0x =处可导性，故()F x 在0x =处必连续因此，有00lim ()lim ()x x F x F x −+→→=，即 121C C =+.取20C =得)1, 0,()(1)sin cos ,0.x x F x x x x x −+≤= ++> 应选(D) .【评注】此题考查分段函数的不定积分，属于常规题，与2016年真题的完全类似，在《真题精讲班》系统讲解过. 原题为已知函数2(1),1,()ln ,1.x x f x x x −< = ≥ 则()f x 的一个原函数是( )(A) 2(1),1,()(ln 1), 1.x x F x x x x −<=−≥ (B) 2(1),1,()(ln 1)1, 1.x x F x x x x −<= +−≥ (C) 2(1),1,()(ln 1)1, 1.x x F x x x x −<=++≥ (D) 2(1),1,()(ln 1)1, 1.x x F x x x x −<= −+≥3.设数列{}{},n n x y 满足211111,sin ,2n n n n x y x x y y ++====()1,2,n = ，则当n →∞时（）（A ）n x 是n y 的高阶无穷小（B ）n y 是n x 的高阶无穷小（C ）n x 是n y 的等阶无穷小（D ）n x 是n y 的同阶但不等价无穷小【答案】（B ）【解析】由2111,,2n n y y y +==知2112nn y + =，则有112n n y y +< 利用12sin n n n x x x π+=>，则1112n nx x π+<故21111111224444n n nn nn n n n n y y y y y x x x x x πππππ+−+− ≤=≤≤≤= 于是1110lim lim 04nn n n n y x +→∞→∞+ ≤≤= ，由夹逼准则lim 0nn ny x →∞=，选（B ）【评注】本题属于今年难度较大的题，涉及到两个递推数列确定的无穷小的比较，涉及到不等式的放缩，有一定的综合性.4．若微分方程0y ay by ′′′++=的解在(,)−∞+∞上有界，则（）（A ）00a b <>，（B ）00a b >>，（C ）00a b =>，（D ）00a b =<，【答案】（C ）【解析】特征方程为20r ar b ++=，解得1,2r =．记24a b ∆=−当0∆>时，方程的通解为1212()e e r x r x yx c c ⋅⋅=+，当12,c c 不全为零时()y x 在(,)−∞+∞上无界.当12,c c 不全为零时()y x 在(,)−∞+∞上无界.当0∆=时，1202ar r −=<=，方程的通解为1112()e e r x r x yx c c x =+，当12,c c 不全为零时()y x 在(,)−∞+∞上无界.当0∆<时，1,22a r i β=−±,方程的通解为()212()e cos sin ax y x c x c x ββ−=+．只有当0a =，且240a b ∆=−<，即0b >时，lim ()lim ()0x x y x y x →+∞→−∞==，此时方程的解在(,)−∞+∞上有界. 故选（C ）【评注】此题关于x →+∞方向的讨论，在《基础班》习题课上讲解过，见《基础班》习题课第八讲《常微分方程》第15题.5.设()y f x =由2,sin ,x t t y t t =+=确定，则（）（A ）()f x 连续，(0)f ′不存在（B ）(0)f ′存在，()f x ′在0x =不连续（C ）()f x ′连续，(0)f ′′不存在（D ）(0)f ′′存在，()f x ′′在0x =不连续【答案】（C ）【解析】0t ≥时3,sin ,x t y t t == ，即有sin 33x xy =.0t <时,sin ,x t y t t = =−，即有sin y x x =−.sin ,033sin ,0x x x y x x x ≥= −< ,显然有()f x 在0x =不连续，且(0)0f = 0x >时，sin cos 33(3)9x x x xf x =+′；0x <时，sin ()cos x f x x x ′=−−，利用导数定义可得()0sin 0330lim 0x x xf x ++→−′==，()0sin 0lim 0x x x f x+−→−′==，即得(0)0f ′= 易验证()0lim ()lim ()00x x f x f x f +−→→′′===，即()f x ′在0x =连续()01sin cos 233930lim 9x x x xf x ++→+′′=，()0sin cos 0lim 2x x x x f x+−→−−′′==−，故(0)f ′′不存在，选（C ）【评注】此题考查参数方程确定的分段函数，只要在参数方程中去掉绝对值的过程，就成了我们常规的分段函数求导的问题，无论是《基础班》第二讲例24，《强化班》第二讲例17. 6.若函数()()121d ln f x x x αα+∞+=∫在0αα=处取得最小值，则0α=（）（A ）()1ln ln 2−（B ）()ln ln 2−（C ）1ln 2−（D ）ln 2【答案】（A ）【解析】反常积分的判别规律知11α+>，即0α>时反常积分()121d ln x x x α+∞+∫收敛此时()()()212111d ln ln f x x x x αααα+∞+∞+==−∫()11ln 2αα=令()()()2111ln ln 2ln 2ln 2f ααααα′=−−()2111ln ln 20ln 2ααα =−+= 得唯一驻点()1ln ln 2α=−，故选（A ）【评注】此题是属于由反常积分确定的函数求最值的问题，积分本身不难，积分结果再求导，找驻点得结果.难度不大，只要基本计算能力过关，可轻松应对.《基础班》《强化班》相应问题得组合而已. 7.设函数()()2e xf x xa =+，若()f x 没有极值点，但曲线()f x 有拐点，则a 的取值范围是（）（A ）[)0,1（B ）[)1,+∞ （C ）[)1,2 （D ）[)2,+∞【答案】（C ）【解析】()()2e xf x xa =+，()()22e x f x xa x ′=++，()()242e x f x xa x ′′=+++由()()211e x f x x a ′=++−，知10a −≥时，()0f x ′≥，此时()f x 无极值点.由()()222e x f x x a ′′=++−，知20a −<时，()f x ′′在2x =±的左右两侧变号，依题意有[)1,2a ∈，选（C ）【评注】本题考查了极值点、拐点的必要条件与判定，题目本身是常规的，分开对这两个考点出题，在《基础班》和《强化班》都讲过，但这种问法有些学生可能会觉得很别扭.8．设A,B 分别为n 阶可逆矩阵，E 是n 阶单位矩阵，*M 为M 的伴随矩阵，则AE OB 为（）（A ）*****−A B B A O A B （B ）****− A B A B O B A（C ）****−B A B A O A B （D ）**** −B A A B O A B 【答案】（D ）【解析】由分块矩阵求逆与行列式的公式，结合1∗−=A A A 得11111∗−−−−− − ==A E A E A E E A A AB B O B O B O B O B ∗∗∗∗−=B O A A A B B ，选（D ）【评注】这钟类型的题在02年，09年均考过完全类似的题，《基础班》第二讲也讲过，原题为【例1】设,A B ∗∗分别为n 阶可逆矩阵,A B 对应的伴随矩阵，∗∗=A O C O B9.二次型()()()222123121323(,,)4f x x x x x x x x x =+++−−的规范形为（）. （A ）2212y y +（B ）2212y y −（C ）222123y y y −−（D ）222123y y y +−【答案】（B ）【详解】因为123(,,)f x x x 222123121323233228x x x x x x x x x =−−+++方法1.二次型的矩阵为 211134143=− −A , 由()()211134730143λλλλλλλ−−−−=−+−=+−=−−+E A ，得特征值为0,7,3−，故选（B ）方法2.()222123123121323,,233228f x x x x x x x x x x x x =−−+++()()()22232322211232323233842x x x x x x x x x x x x ++=+++−−−+222222322332323126616222x x x x x x x x x x x +++++−=+− ()22231237222x x x x x + =+−− 故所求规范形为()2212312,,f x x x y y =−，故选（B ）【评注】本题考查二次型的规范形，与考查正负惯性指数是同一类题，在《基础班》《强化班》均讲过. 《解题模板班》类似例题为【11】设123123(,,),(,,)T T a a a b b b αβ==，,αβ线性无关，则二次型 123112233112233(,,)()()f x x x a x a x a x b x b x b x =++++的规范型为( )． (A)21y (B)2212y y + (C) 2212y y − (D) 222123y y y ++10．已知向量12121,,1222150390,1====ααββ，若γ既可由12,αα表示，也由与12,ββ表示，则=γ（）.（A ）334k （B ）3510k（C ）112k − （D ）158k【答案】（D ）【解析】由题意可设11212212x y x y +==+γααββ，只需求出21,x x 即可即解方程组112112220x y y x +−−=ααββ()121212211003,,2150010131910011,−−−−=−→− −−ααββ 得()()2211,,1,3,,1,1TTx k x y y =−−，k 为任意常数11221212133215318x k k k k k x+=−+=−+=−=γαααα，故选（D ）【评注】1.此题与《强化班》讲义第三讲练习第12题完全类似，原题为【12】(1)设21,αα，21,ββ均是三维列向量，且21,αα线性无关, 21,ββ线性无关，证明存在非零向量ξ，使得ξ既可由21,αα线性表出，又可由21,ββ线性表出．(2)当 =4311α，=5522α：1231β = − ，2343β−=−时，求所有既可由21,αα线性表出，又可21,ββ线性表出的向量。

硕士研究生学位考试练习题参考答案

硕士研究生学位考试练习题参考答案Test FivePart I Listening Comprehension1-20 ABCAB AABAC CCCCB ACCBCPart II Cloze Test21-35 ADBAA CADDA DDBCBPart III Reading Comprehension36-55 DBADC CDDCB ABCDC BBDBCPart IV Translation汽车、电视以及不断扩充的办公室工作，可能已经造就了人类社会有史以来最名副其实的“久坐一族”。

另一方面，富含蛋白质和卡路里的饮食日趋普遍，其中的蛋白质和卡路里含量足够一名伐木工人或一位职业拳击手每天所需。

在世界各处，巨额的肉类消费增大了对食粮牲畜的需求。

与此同时，我们自己通过吃面包所摄入的少得可怜的粮食，其营养价值和促进肠道蠕动的糙粮微乎其微，因为这些都在面粉精制过程中被去掉了。

这样一来，人的胃肠就失去了正常运转所需的纤维质。

同样可以提供必要纤维的新鲜蔬菜，其食用量在过去50 年间减少了三分之一，取而代之的是经过加工、去掉纤维的食物。

结果有目共睹：在所有发达国家，肥胖症及与饮食有关的疾病已经成为医学的一大难题。

现在许多医学专家一致认为，由于脂肪、糖、胆固醇、细粮、食物添加剂的大量食用，加上总体上促进肠道蠕动的糙粮的缺乏，现代公民们在吃吃喝喝中患上心脏病或癌症，直至将自己送进坟墓。

Test SixPart I Listening Comprehension1-20 BBADA DDACA DCCCB ACCDDPart II Cloze Test21-35 AABDD CABAD CCBDAPart III Reading Comprehension36-55 DACBA ABDDB AACBC BBCDBPart IV Translation政府发挥作用最重要的方面之一就是节约能源，但它也许是财政拨款，研究经费分配最少的部门。

全国硕士研究生入学考试政治试题及答案

A12万元 B9万元 C8万元 D7万元
13、2003年9月通过全民公决否决了加入欧元区议案的欧盟国家是
A瑞典 B丹麦 C英国 D希腊
14、2003年6月22日至27日，印度总理瓦杰帕伊对我国进行正式访问，这是印度总理10年来首次访华，访问取得了成功，两国签署了
A《中印关系原则和全面合作宣言》 B《中印联合新闻公报》
17、有一幅广告幽默画，画的是几个行人在看一家饭店外贴的告示，上写：“快进来吃饭吧，否则你我都得挨饿。”这幅广告画的寓意有
A生产者和消费者是相互依存的 B生产和消费具有直接的同一性
C利己是人的一切活动的出发点 D商品交换活动背后隐藏着人与人的关系
E生产关系本质上是人与人之间的物质利益关系
30、中共十六届三中全会强调，完善社会主义市场经济体制的主要任务是
A完善公有制为主体、多种所有制经济共同发展的基本经济制度
B建立有利于逐步改变城乡二元经济结构的体制，形成促进区域经济协调发展的机制
C建设统一开放竞争有序的现代市场体系，完善宏观调控体系、行政管理体制和经济法律制度
D健全就业、收入分配和社会保障制度
C《中印联合声明》 D《关于中国西藏地方和印度之间的通商和交通协定》
15、2003年中国与欧盟关系有了进一步发展，其突出表现是
A中国与欧盟领导人年度会晤机制起步
B中国与欧盟建立全面伙伴关系
C中国首次制定和发表《中国对欧盟政策文件》
D欧盟首次制订和发表《中国欧盟关系长期政策》
根据材料辨析：有必要限制市场机制的作用，让拥有强制力的政府来干预。
33、在新民主主义革命时期，只有当民族资产阶级拥护革命时，才要保护民族资本主义。
四、分析题

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北京工业大学硕士研究生考试试题
课程名称:数字信号处理
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u(n)
系统是不稳定的。
(c) 因为系统是非因果的，则它的ROC为 z 0.5, 所以有
h(n)
[(
1 2
)n
2(3)n
]u(n
1)
系统是不稳定的。
5. 已知一个有限长序列 x(n) (n) 2 (n 5)
求 x(n) 的10点DFT X (k) 。
1) 已知序列 m(n) 的10点DFT为 M (k) X (k)Y (k)，求序列m(n) 。
F1 1kHz, F2 3kHz, F3 6kHz
这样，最大频率 Fmax 6kHz，由取样定理，可得
Fs 2Fmax 12kHz
于是，奈奎斯特率为 FN 12kHz 。
(b) 方法一
由于Fs 5kHz，所以折叠频率为 Fs 2 2.5kHz
x(n) xa (nT ) xa (n / Fs )
x(n) 13cos 2 (1/ 5)n 5sin 2 (2 / 5)n
ya (t) 13cos 2000 t 5sin 4000 t
2. 考虑二阶差分方程描述的系统
y(n) 3y(n 1) 4y(n 2) x(n) 2x(n 1) (1)
若输入序列为 x(n) 4n u(n) 那么，系统响应 y(n)(n 0)是什么?
(a) 系统稳定的；(b) 系统因果的；(c) 系统反因果的
解：
系统的极点为z 1 2和z 3。
(a) 因为系统稳定，它的ROC必须包含单位圆，所以有 1 z 3, 2
因此，h(n)是非因果的，可以表示为
h(n)
(
1 2
)n
u(n)
2(3)n
u
(n
1)
(b) 因为系统是因果的，则它的ROC为 z 3, 此时
假定特解形式是同一样形式的指数序列，一般地，我们可以假定解的形式为
yp (n) K(4)n u(n)
然而，yp (n)已经包含在齐次解中，这样，特解就是多余的。而选择的特解和齐次解中的各个项是线性无关的。实际上，要像处理特征方程出现重根一样处理这种情况。于是，假定
yp (n) Kn(4)n u(n)
3cos 2 (1/ 5)n 5sin 2 (3 / 5)n 10cos 2 (6 / 5)n 3cos 2 (1/ 5)n 5sin 2 (1 2 / 5)n 10cos 2 (11/ 5)n 3cos 2 (1/ 5)n 5sin 2 (2 / 5)n 10cos 2 (1/ 5)n