一、基本用法
as ... as
用于比较句型,中间插入的是形容词或副词的原级。意思是"达到与什么相同的程度"。如：He is as strong as a horse. 他力大如牛。
二、习惯用法
1. as soon as
意思是"一......就......",引导一个时间状语从句。如：I'll call you as soon as I finish my homework. 我一完成我的作业,就给你打电话。
2. as long as
意思是"长达......之久;只要......"。如：She has searched the information about dinosaurs on the Internet as long as three hours. 她在因特网上搜索有关恐龙的信息已经长达三个小时。
3. as much as
意思是"高达......;与......一样多"。是用来表达极其多的语气。如：Some of the stones weigh as much as fifteen tons.有些石头重达15吨。
★as...as用法：
as...as意为"和……一样"，表示同级的比较。使用时要注意第一个as为副词，第二个as为连词。其基本结构为：as+ adj./ adv. +as。
例如：
(1)This film is as interesting as that one.这部电影和那部电影一样有趣。
其否定式为not as/so +adj./ adv. +as。例如：
This dictionary is not as/so useful as you think.这本字典不如你想象的那样有用。
若有修饰成分，如twice, three times, half, a quarter等，则须置于第一个as之前。
例如：
Your bag is twice as expensive as mine.你的袋子比我的贵一倍。
几个关于as...as的常见句型：
(1)as...as possible
Please answer my question as soon as possible.请尽快回答我的问题。
(2)as...as usual/before
She looks as pretty as before.她看起来和以前一样漂亮。
(3)as long as... (引导条件状语从句)
It took us as long as three years to carry out the plan.我们花了长达三年的时间才完成这项计划。
(4)as far as
He walked as far as the railway station yesterday evening.昨天傍晚，他一直散步到火车站。
(5)as well as
She cooks as well as her mother does.她烧菜烧得跟她母亲一样好。
★as...as的结构：
as + 形容词或副词原级 + as
1)在否定句或疑问句中可用so… as。
He cannot run so/as fast as you.
2)当as… as 中间有名词时采用以下格式。
as +形容词+ a +单数名词
as + many/much +名词
This is as good an example as the other is.
I can carry as much paper as you can..
3)用表示倍数的词或其他程度副词做修饰语时，放在as的前面。
This room is twice as big as that one.
Your room is the same size as mine.
4) 倍数+ as + adj. + as <=> 倍数+ then + of
This bridge is three times as long as that one.
This bridge is three times the length of that one.
Your room is twice as large as mine.
Your room is twice the size of mine.
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