介绍:
现在完成时
1. 构成 have / has +动词的过去分词
Eg： He has been to shanghai .
否定：He hasn’t been to shanghai yet. 他还没有去过上海。
疑问句：Has he been to Shanghai？
2. 基本用法
(1)表示一个过去发生或已完成的动作对现在影响或结果，强调的是现在的状况（表示“已完成”）。如：
I've had two letters from him. 我已收到他的两封信。
Someone has broken the window. 有人把窗户打破了。（结果：这窗户破了 猜测影响：房间更冷了）
Lily has finished her homework. Lily做完作业了 (结果：她可以做别的事情了)
* He has left the city. 翻译：他已离开这个城市。
(2) 表示的动作开始于过去，持续到现在，也可能还会持续下去（表示“未完成”）。如：
He has been busy since last week.自上个星期以来他一直很忙。
They have been friends ever since they were in grade school. 他们从小学起就一直是好朋友。
How long have you been here? 你来多久了？
I’ve finished half so far. 到目前为止我只完成一半。
*We haven't seen each other for ages. 我们好久没见面了。
We __ __ (seen) each other for ages.
注：非延续性动词不能与表示一般时间的状语连用。如：
误：He has died for two years. 他死了两年了。
正：He has been dead for two years.
正：He died two years ago.
误：The film has begun for ten minutes. 电影开演十分钟了。
正：The film has been on for ten minutes.
正：The film began ten minutes ago.
延伸： 英语中，按动词延续的时间长短，可将动词分为延续性动词和短暂性动词。延续性动词如learn, study, work, play, wait等。短暂性动词是非延续性动词，即动作一开始便结束的动词，又可称结束性动词，瞬间动词，如come, go, begin, start, become, join, end, die, buy, arrive, reach, borrow, lend, get to know等。
**** have been to 和have gone to的区别
两者均可后接地点，have been to表示去过某地，现在不在某地；have gone to表示到某地去了，现在不在此地。比较：
She has gone to Pairs. 她去了巴黎。（现在不在这儿）
She has been to Paris (three times). 她去过巴黎(三次)。(现不在巴黎)
Have you ever been to American? 你曾经去过美国吗？
He has gone to the post office. 他已经去邮局了。（反正现在人是不在这里的）
(3)现在完成时还可表示过去的重复动作。如：
He has always gone to work by bike. 他总是骑自行车上班。
作业：私信老师完成以下填空
1.I __ __ (see) you before, but I can't remember where. 我以前见过你，但是不记得在哪里了。
2.We__ __ (have) any trouble so far. 到目前为止，我们还没有遇到任何麻烦。
3. Great changes __ __ (take )place in the last three years 最近三年我们学校发生很大变化。
4.Up to now, the work _ _(is)easy. 到现在为止这工作还算容易。
5.It is the second time I __ __ (meet) him here today. 这是我今天第二次见到他了。
答案：1.have seen 2.haven't had 3.have taken 4.has been 5.have met
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