as…as结构的几点用法说明：
1.基本用法
该结构的基本意思是“与……一样”，其中接形容词或副词的原级，在否定句中，第一个as也可换成so.如：
He doesn't study as [so] hard as his brother. 他学习不如他弟弟努力。
2.涉及数量或程度的用法
若涉及数量或程度，可用“as much+不可数名词+as”和“asmany+可数名词复数+as”。如：
He doesn‘t pay as much tax as we do / as us. 他没我们交的税款多。
There are not as many restaurants as there were. 现在餐馆没有过去多了。
3.有关词序的一点说明
其间接形容词时，有时该形容词还可修饰另一名词，但这个名词应带有不定冠词(注意词序)。如：
I have as good a voice as you. 我的声音和你一样好。
4.该结构的修饰语
根据情况可用(not) nearly, almost, just, nothing like, exactly, not quite, half, one-ten, twice, threetimes, 30 per cent等修饰，并且这些修饰语必须置于第一个as之前，而不能置于其后。如：
This room is twice as large as that one. 这个房间是那个房间的两个大。
You‘re not half as clever us you think you are. 你远不是自己想像的那么聪明。
It took three times as long as I had expected. 这件事比我预料的多花了两倍的时间。
（编辑：赵宁）
From:https://www.zgghmh.com/CET-4/20000791.asp