一些关于定语从句的问题

as.. as表示比较，这里固定用法后面一个as引导定语从句修饰man，as引导非限制性定语从句的位置比which灵活，可以放在句首，如As is known to all，这种情况不能用which 来换。
这样后面两句也就解释了为什么这样用。

希望这一回答对你有所帮助，如满意请点击下面的“选为满意答案”按钮，谢谢您！

as引导非限制性定语从句，指代整个主句内容，从句可置于句首，句中或句尾

which引导非限制性定语从句，指代整个主句内容，从句只能置于主句之后, 且与主句之间用逗号隔开.

当as引导非限制性定语从句，指代整个主句内容，且从句置于句尾时, 有些情况可同which互换,
如: He saw the girl, as /which he had hoped.

但有些情况不能.如:Tom works hard and is willing to help others, as we all know.中的
as we all know就不要换成which we all know.

因为在句法上，as常用作一些实意动词(如see, know, hear, watch, remember, say, tell, show, expect, guess等)的宾语，这类动词与as几乎成了一种固定搭配。又如：

Einstein, as we know(=as is well known), is a famous scientist.
众所周知，爱因斯坦是一位著名的科学家。

There was a net bar around here, as I remember.
我记得这儿附近有一家网吧。

As everyone knows ,China is a beautiful country with a long history中的
as不能换成which, 因为从句置于句首必定用as.

as we had expected 这句话的主句哪去了？？
这只是一个从句,主句没有写出来. 不过这句话可以单独使用.

She will marry as healthy a man as she can find中第二个as引导定语从句修饰man.
as healthy a man as she can find一个她能找到的健康的人.

healthy不是"有钱的",而是"健康的". wealthy才是"有钱的".