关系代词as与which的用法区别

(6)  当关系代词代替主句中的宾语从句或复合结构(如：宾+补；不定式短语；动词-ing形式短语等) 时，一般只能用which, 而不用 as。如：

She told us that there was something wrong with her bike, which was true。她告诉我们说她的单车出了毛病，这话是真的。

He asked her to help him with his English, which she did. 他请她教他学英语，她的确帮了。

(7)  关系代词仅代表主句中的谓语部分时，从句中谓语部分被省略而只保留情态动词的否定式或助动词否定式，引导词一般只用which, 而不用as。如：

He speaks English very fluently, which I can’t. 他的英语说得非常流利，这我可不行。

(8) 关系代词作定语修饰后面的名词时，一般只用which, 而不用as。如：

He suggested going swimming in the river, which idea we agreed with. 他提议去河里游泳，我们就同意了他的想法。

(9) 当关系代词仅代表主句中单个的名词时，一般只用which, 而不用as。如：

He sent me a beautiful present, which I valued very much. 他给寄来了一件精美的礼物，我对它非常珍视。

(10) as 在非限制性定语从句中，还常跟such连用。如：

There was a look of love in the teacher’s eyes, such as mothers have for their children. 老师眼里流露出对他喜爱的神情，就好像母亲对孩子的喜爱。

(11) as常用于一些固定结构中。如：

as is well known / as we all know 众所周知；             as is said above 正如上面所说；

as might be imagined 正像所想象的那样；                  as is reported 如报道所说；

as has been pointed 如所指出的那样；                        as is expected 正如所料。