爱华网as if 的用法
http://wenku.baidu.com/link?url=c6E047wdHJtcIcI4ChVVbyHEusuIb97Nd-bzlqw6bq3pup4BDvipMsJv7JWkSFmuEfO8D7WB4Wb76zDMlReITyM7my7bD61hCJhj-EHzLi7
http://wenku.baidu.com/link?url=c6E047wdHJtcIcI4ChVVbyHEusuIb97Nd-bzlqw6bq3pup4BDvipMsJv7JWkSFmuEfO8D7WB4Wb76zDMlReITyM7my7bD61hCJhj-EHzLi7
1． as if从句的作用
as if一般可由as though来代替。可在look,seem等系动词后引导表语从句。如：
He looked as if / though he was ill.他看起来似乎生病了。
It seems as if it is going to rain.
看来似乎要下雨了。
它还可引导方式状语从句。如：
I remember the whole thing as if / though ithappened yesterday.
我记得整个事情，就似乎它是发生在昨天一样。
The child talked to us as if he were a grownup.
那个小孩跟我们讲话就像个大人一样。
2． as if 从句的语气及时态
① 当说话者认为句子所述的是真实的或极有可能发生或存在的事实时， asif从句用陈述语气。如：
It sounds as if it is raining.
听起来像在下雨。
He talks as if he is drunk.
从他说话的样子来看他是醉了。
② 当说话人认为句子所述的是不真实的或极少有可能发生或存在的情况时， as if从句用虚拟语气。表示与现在事实相反，谓语动词用一般过去式。如：
You look as if you didn’t care.
He talked as if he knew what had happened?
他说话的样子，似乎他知道发生了什么事情。
表示与过去或与谈话时间为止发生的事实相反，谓语动词用“had 过去分词”。如：
He talked about the Great Wallas if he had been there before.
他说起长城来似乎他以前去过那里。
The girl listened as if she had been turned tostone.
那女孩倾听着，一动也不动，像已经变成了石头。
表示与将来事实相反，谓语动词用“would / could / might动词原形”。如：
He opened his mouth as if hewould say something.
他张开嘴似乎要说什么。
It looks as if it might snow.
看来似乎要下雪了。
3． as if从句中的省略
假如as if 引导的从句是“主语 系动词”结构，可省略主语和系动词等成份，这样as if后就只剩下名词、不定式、 形容词（短语）或动词ing形式等。
He acts as if (he was) a fool.
他做事像个傻子。
He paused as if (he was going) to let the sadmemory pass.
他停了下来，就似乎要把悲伤的记忆抹去。
The girl left the room hurriedly as if (she was)angry.
女孩匆忙离开房间，似乎生气的样子。
From time to time, Jason turned round as if (hewas) searching for someone.
贾森不时地转过身来，好象在找人。
