NO.1 意义

现在完成时有三个意义

1. 过去发生的动作已经完成 eg：My aunt has travelled all over the world.
2. 过去发生的动作对现在有影响
   I have seen the movie Godzilla and Kong, so I don't want to see it now.
3. 过去发生的动作或状态持续到现在(当表示这个意义时，动词用的是延续性动词)
   I have had the dog since three days ago.

NO.2 基本形式

现在完成时的基本形式为have/has done

第三人称单数用has, 第一人称单复数或第二人称单复数、第三人称复数都用have

eg：My aunt has travelled around the world.

我的姑姑已经环游过世界了。(has在此处是第三人称单数的体现)

也因此，现在完成时可以翻译为已经做了...

I have finished my homework. （我已经完成我的作业。）

NO.3 句型转换

现在完成时句型在应用时也会有一般疑问句和否定句的转换情况。

根据以往的学习可以知道，一般疑问句的开头通常是be动词，情态动词或者助动词，因此在现在完成时中，一般疑问句用助动词have/has 提前即可

My aunt has travelled around the world.

→Has your aunt travelled around the world?(提问时把第一人称改为第二人称)

肯定回答: Yes, she has.

否定回答: No, she hasn't.

否定句时在助动词have/has后加not即可

→My aunt has not(hasn't) travelled around the world.

NO.4 搭配成分

现在完成时在使用时，有一些标志性的词

1. 辨析一: already, just, yet
   I have already/just finished my homework.(already/just通常用于肯定句，表示已经的意思) I haven't finished my homework yet.(yet表示还没有的意思时，通常用于否定句中)
2. 辨析二: 次数, ever, neverI have ever been to Beijing before.I have never been to Beijing.I have been to Beijing three times.(一次once, 两次twice, 三次three times, 往上基数词 times)
3. 辨析三: for 一段时间, since 过去时间点I have stayed in Beijing for three days.(for 一段时间) I have stayed in Beijing since three days ago.(since 一段时间 ago) I have stayed in Beijing since yesterday afternoon.(since 过去时间点) I have stayed in Beijing since I was three years old.(since 从句，从句用一般过去时)

NO.6 对比

对比一: 短暂性动词 vs. 延续性动词

由上表可知，be adj. 表示的状态，基本上是属于延续性的意义。

对比二: have gone to/have been to/have been in

have gone to 表示去了没回来(短暂性意义)

have been to 表示去了回来了(短暂性意义)

have been in 表示去了一直待在那里(延续性意义)

eg:

I have gone to Beijing, so there is no one in my room.

I have been to Beijing, and I have had a great time there.

I have been in Beijing for three months, and we have visited lots of places of interest.