完成时态的时间状语怎么加??

since 后通常接过去的某个具体开始时间，for则通常表示持续时间长短。如：

I've worked here for 5 years since I joined in Nov, 2002.
自从2002年11月加入以来，我已经在这儿工作5年了！

更多说明，详见：
http://www.hongen.com/eng/pub/yufac/1112.htm

可以加for,since,by等

for后面跟时间段，如I have learned English for 3 years.

since后面加时间点，如：I have learned English since I went to school.
I have learned English since 1999.

两者一般来说可以转换;
例:
He has studied English for 3 years.
=He has studied English since 3 years ago.
for 后面跟的是一段时间词(3 days).
而since后面跟的是过去时间短语(3 days ago).