由“have/has+过去分词”构成，主要有两个含义： ①表示动作发生在过去，但与现在的情况有联系，有时无时间状语，有时和一些表示不确定的过去时间状语连用，如：many times，just，yet，ever，never，already，before，so far, by now等连用。 ②表示从过去某一时间开始一直延续到现在并还可能继续延续下去的动作，用于延续性动词，且句中常带有表示一段时间的时间状语，如：for two months, so far等。
①表示动作发生在过去，对现在有影响，有时无时间状语，有时和一些表示不确定的过去时间状语连用，如：many times，just，yet，ever，never，already，before，so far, by now等连用。
②表示从过去某一时间开始一直延续到现在并还可能继续延续下去的动作，用于延续性动词，且句中常带有表示一段时间的时间状语，如：since + 时间点/从句，for two months, so far等。
在“it is the first/second...time that...。”或在“it/this/that is the +最高级+名词+that...。”结构中，that从句中的动词常用现在完成时；表示到说话时为止动作发生过几次。在“it + be...+since从句”这一结构中，be可用一般现在时或现在完成时，since从句一般用过去时。have/has/had +been +动词的现在进行时。
yesterday, last week，…ago, in1980, just now, 具体的时间状语
this morning, tonight, this April, now, once，before, already, recently，lately
for, since, so far, ever, never, just, yet, till / until, up to now, in past years, always,
3）现在完成时可表示持续到现在的动作或状态，动词一般是延续性，如live, teach, learn, work, study, know.
过去时常用的非持续性动词有come, go, leave, start, die, finish, become, get married等。
I saw this film yesterday.
I have seen this film.
Why did you get up so early?
Who hasn't handed in his paper?
She has returned from Paris.
She returned yesterday.
He has been in the League for three years.
He has been a League member for three years.
He joined the League three years ago.
I have finished my homework now.
---Will somebody go and get Dr. White?
---He's already been sent for.
句子中如有过去时的时间副词（如 yesterday, last, week, in 1960）时，不能使用现在完成时，要用过去时。
（错）Tom has written a letter to his parents last night.
（对）Tom wrote a letter to his parents last night.
1）It is the first / second time…. that…结构中的从句部分，用现在完成时。
It is the first time that I have visited the city.
It was the third time that the boy had been late.
2）This is the… that…结构，that从句要用现在完成时.
This is the best film that I've (ever) seen.
This is the first time (that) I've heard him sing.这是我第一次听他唱歌。
---No, this is the first time I ___ here.
was B. have been C. came D. am coming
答案B. This is the first time 后面所加从句应为现在完成时，故选B。
---No, it's the first time I ___ here.
even, come B. even, have come C. ever, come D. ever, have come
答案D. ever意为曾经或无论何时，反意词为never，此两词常用于完成时。 This is the largest fish I have ever seen. It is / was the first time +that-clause 的句型中，从句要用完成时。
（错）I have received his letter for a month.
（对）I haven't received his letter for almost a month.
I have lived here for more than twenty years.
I have lived here since I was born..
My aunt has worked in a clinic since 1949.
Some new oilfields have been opened up since 1976.
I have known Xiao Li since she was a little girl.
My brother has been in the Youth League for two years.
I have not heard from my uncle for a long time.
I worked here for more than twenty years.
I have worked here for many years.
(对) Tom has studied Russian for three years.
= Tom began to study Russian three years ago, and is still studying it now.
(错) Harry has got married for six years.
= Harry began to get married six years ago, and is still getting married now.
显然，第二句不对，它应改为 Harry got married six years ago.或 Harry has been married for six years.