一、构成
1.肯定句：have/has+过去分词（done)
主语（I/We/You/They/复数名词）+have+过去分词(done)+其他
主语（He/She/It/单数名词）+has+过去分词（done)+其他
2.否定句：主语+have/has+not +过去分词(done)+其他
3.一般疑问句：Have/Has+主语+过去分词(done)+其他
二、表示过去发生的某一动作对现在造成的结果或影响
E.g. She has already left our city. 她已经离开我们的城市了。
Has anyone told you about it? 有人告诉你这件事吗？
We haven't finished the work yet. 我们还没有完成这项工作了。
常与这些标志词连用：already,yet,ever,just,recently,lately,never,before(adv.)
三、要注意for,since引导的状语时的区别
for与一段时间连用即用来说明动作延续时间长度。
E.g. I have lived here for more than twenty years.
我已经住在这里二十多年了。
He has stayed here for 3 hours.
他已经待在这儿三个小时了。
since表“自从……以来”与具体的过去时间点连用即用来说明动词起始时间。
since+一段时间+ago;since+一个时间点；since+从句
E.g. He has stayed here since 3 hours ago.
He has stayed here since 3 o'clock.
He has taught English since he came here.
注意：短暂性动词或终止性动词leave,arrive,come ,go,return,begin,start,put,stop,die,fall,buy,borrow,see等构成的完成时不能与for或since引导的时间状语连用。因此在使用这些动词时用意义与其相近的延续性动词、be+形容词/副词等来代替他们。如borrow改为keep/have;die改为be dead;leave改为be away等，或将完成时改为一般过去时。
E.g.
1.错 He has died for 3 years.
正 He has been dead for 3 years.
正 He died 3 years ago.
2.错 How long have you borrowed it?
正 How long have you kept it?
四、表示反复发生的经历
E.g.
He has hosted the show eight times.
他已经连续八次主持表演。
Billy Crystal has been in many films and television shows.
贝利·克里斯托已经出演过多部电影和电视剧。
We have been to the Great Wall many times.
我们已去过长城多次。
五、下列句型中常用现在时
1.It is (has been)+一段时间+since+从句
自从……来有多长时间了。
2.This(That/It) is/will be the first(second) time that+完成时
是某人或某事第几次……
3.This(That/It) is the best/finest/most interesting……+that+完成时
E.g.It's/It has been 3 years since they got married.
It's the first time that I have been to the Great Wall.
This is the most interesting film that I have ever seen.
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