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as引导的定语从句

as的用法

一、as引导限制性定语从句

as引导限制性定语从句主要出现在一些固定的结构中。as在限制性定语从句中可用作主语、宾语和表语。

a. such...as结构

这种结构中的such即可用作形容词,作先行词的定语,既构成“such + 名词+ as”的结构; 也可用作代词,充当as的先行词,即构成such as的结构。例如:

She is not such a careless student as you think she is.

The instrument is not such as I saw on the exhibition.

b. the same...as 结构

这种结构中的same 即可用作形容词,作先行词的定语,即构成“the same + 名词+ as”的结构; 也可用作代词,充当as的先行词,既构成the same as结构。例如:

He is not the same man as he was before.

He is not the same as he was before.

另请注意:当先行词受same 修饰时,关系代词亦可用that,但必须注意它们的区别:用that 一般表示从句的内容与主句所表示的内容是“同一的”;用as则通常表示“与...相似的”的意义,从句表示的内容与主句的内容相似。例如:

This is the same bag that I lost yesterday.

This is the same bag as I lost yesterday.

(This bag is like the one that I lost yesterday.)

c. as many...as 和as much...as结构

在这种结构中,第一个as是副词,修饰many或much, many或much分别接复数可数名词和不可数名词,第二个as 是关系代词。例如:

There are many books as are needed.

Take as much paper as you need, but not more than is necessary.

这种结构中的many 和much 也可以作代词,充当as 的先行词。

There is plenty of water here, you may take as much as you want.

d. as...as 和so...as结构

在这种结构中,第一个as或so均是副词,其后紧跟形容词,形容词后通常再跟带不定冠词a(n)的单数名词。例如:

It was as pleasant a day as I have ever spent.

We witnessed(亲眼见到) so great a parade(游行) as nobody ever dreamt of in pre-liberation days.

二、as引导非限制性定语从句

在as引导的非限制性定语从句中,as 常用以代替整个句子或者句子的一部分,as在从句中可用作作主语、宾语和表语等,从句的位置比较灵活,可以位于句首、句中或句末。

As is known to all, Taiwan is part of China.众所周知,台湾是中国的一部分。

As everyone knows, China is a beautiful country with a long history.

每个人都知道,中国是一个有着悠久历史的美丽国家。

The earth, as we know, moves round the sun.我们都知道地球围着太阳转。

Tom works hard and is willing to help others, as we all know.

汤姆工作努力,并且乐于助人,这一点我们都知道。

as引导的定语从句

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