主语从句的用法 主语从句讲解

主语从句的用法主语从句讲解

一个句子在复合句中充当一个主语，那么这个句子就是主语从句。下面小编就给大家介绍主语从句的用法。

主语从句的用法

主语从句定义:在句子中担当主语的是一个从句,这个从句就叫做主语从句。

主语从句是在复合句中充当主语的从句，通常放在主句谓语动词之前或由形式主语it 代替，而本身放在句子末尾。

1. It 作形式主语和it引导强调句的比较

It 作形式主语代替主语从句，主要是为了平衡句子结构，主语从句的连接词没有变化。而it引导的强调句则是对句子某一部分进行强调，无论强调的是什么成分，都可用连词that。被强调部分指人是也可用who/whom。例如：

It is a pity that you didn’t go to see the film.

It is +名词+从句

It is a fact that 事实是

It is good news that 是好消息

It is a question that 是个问题

It is common knowledge that 是常识

类似的名词还有：a pity;a wonder;a good thing; no wonder; surprise等。

例如：It is a mystery to me how it all happened.

这一切是怎么发生的是个谜。

It is common knowledge that the whale is not a fish.

鲸鱼不是鱼，这是常识。

It is no surprise that Bob should have won the game.

鲍勃会赢得这场比赛，这不足为奇。

It is +形容词+从句

It is necessary that 有必要

It is clear that 很清楚

It is likely that 很可能

It is important that 重要的是

类似的形容词还有：strange; natural; obvious; true; good; wonderful; possible; unlikely; quite; unusual; certain; evident; worth-while; surprising; interesting; astonishing, etc.

例如：It is obvious that conductors and insulators are both important in industry.

很明显导体和绝缘体在工业中都很重要。

It is doubtful whether she will be able to come.

她是否能来令人怀疑。

It was really astonishing that he refused to talk to you .

他拒绝和你说话真是令人惊讶。

It is essential that he should be here by the weekend .

周末之前，他应该到这里是必要的。

It seems obvious that we can not go on like this.

很明显我们不能这样下去了。

It is +过去分词+从句[1]

It is said that 据说

It is reported that 据报道

It has been proved that 已证明

It must be proved that 必须指出

类似的过去分词还有：known; estimated; expected; believed; thought; hoped; noted; discussed; required; decided; suggested; demanded; made clear; found out,etc.

例如：It is thought that he is the best player.

大家都认为他是最好的选手。

It is estimated that the vase is 2000 years old.

据估计这个花瓶有2000年的历史。

It is used to be thought that a new star must be due to a collision between two stars. 过去一直认为新星是由于两颗星星之间碰撞产生的。

It has not been made clear when the new road is to be opened to traffic.

还没弄清楚这条路将开始通车。

It +不及物动词+从句

It seems that 好像是

It happened that 碰巧

It follows that 由此可见

It has turned out that 结果是

类似的不及物动词还有：seem, appear, occur, follow, happen, turn out, etc.

例如：It turned out that nobody remembered the address.

结果是无人记得那个地址。

It now appears that they are in urgent need of help.

看起来他们急需帮助。

It does not matter if I missed my train, because there is another later.

没有赶上这趟火车没有关系，稍晚还有一趟。

It happened that I saw him yesterday.

碰巧我昨天看见他了。

当及物动词+ 宾语较短时，也可用这种结构。

例如：It shocked me that Peter did not tell anybody where he was.

让我吃惊的是彼得没有告诉任何人他在哪里。

It does not interest me whether you go or not.

我对你去不去不感兴趣。

It +某些固定结构+ 主语从句。

例如：It doesn’t make too much difference (It doesn’t make any difference / It doesn’t alter the situation)，whether it rains or not . 下不下雨都没有多大关系。