定语从句中as和which怎么区分

(1) 当先行词前面有so + adj. + a / such + (a) + adj. , the same等词修饰时，引导词只能用as，而不用which。如：

She is so nice a girl as we all like. 她是个我脊亏备们大家都喜欢的如此好的女孩。

It is such an interesting book as we all want to read. 它是本我们大家都想读的有趣的书。

上面两句中的as就不能用which替换。

(2) as 在从句中常作宾语；作主语时，从句的谓语动词常为系动词，即：系表结构或被樱毁动结构。如：

As you expected, he turned up on time. 正如你所愿，他按时到了。

As is said above, he has conquered the difficulty. 正如上面所说，他征服了困难。

(3) 当非限制性定语从句放到主句的前面时，引导词只能用as，而不用which。如：

As is planned, we got there before eight. 正如计划，我们再把店前到达了那儿。

(4) As引导的非限制性定语从句指表示积极的意义，与主句是顺理成章的关系，绝不能与之矛盾。若非限制性定语从句表示一空誉种消极的意义，则只用which。如：

He has succeeded in his career, as / which we all hope. 他在事业中成功了，这正是我们大家所希望的。

Her grandma died last week, which made her very sad. 她的奶奶逝世了，这使得她很悲伤。

(5) 当非限制性定语从句的引导词前面有介词时，只能用which, 而不可用 as

在非限制性定语从句中，which和as引导定语从句时的区别：
a. which引导的从句不能放在主句前，而as引导的从句则既可以放在主句前，也可以放在主句后。
b. 用能启闹做关系代词，as和which都可以指代一个句子，但as有“启哪正如”、“就像”之意，which则没有此含义。
He is a foreigner, as I know from his accent. (as指代一个句子，意为“正如”、“就像”)
He has to work on Sunday, which he doesn’t like. (which指代一个句子，没有“正如”、“就像”)
c. 当从句的谓语动词是be或相当于联系动词悄旁码的seem, become等时，可用as或which作主语。但当从句的谓语是行为动词时，只能用which作主语。