it seems that 和 as if 有什么不同?

it seems that 和 as if 的意思相同，但用法不同。
it seems that 用于句首。
as if 1． 在look, seem 等系动词后引导表语从句
2． 引导方式状语从句
还可用于省略句中 如果as if 引导的从句是“主语＋系动词”结构

it seems that 加句子 用在句首。
as if 加to do、doing、句子 用在句中。

意思类似,但是用法不同
it seems that + 从句
as if 不能单独引导句子,一般跟在另一个句子后面,as if 后可加从句、ing形式、不定式等.如：
It seems that it is going to rain. = It looks as if it is going to rain.
He stood up as if to say something. 他站起来好像要说什么.
He stood there as if saying something. 他站在那儿好像在说什么.
He talked as if he were a teacher . 他说话的样子好像他是老师似的.（虚拟语气）
as if后面的句子是否是虚拟语气要取决于句子的意思.
【英语牛人团】

It seems that是看起来像,后跟陈述语气的句子，表示事实
as if 好象...似的，表示可能，后大多跟虚拟语气的句子