附加遗产水千丞补肉:现在完成时是什么?怎么用?举些例子.

现在完成时表一个动作已经做完.
和一般现在时比较起来更侧重对现在造成的影响.
一般是. have done sth.

Eg;
Mum,can I go out to play basketball.?I have finished my homework.
妈,我可以出去打篮球了吗.作业已经做完啦.

Eg:
I saw this film yesterday.
我昨天看过这电影.(强调性没那么强.只是单纯的陈述.)

Have you saw the film KINGKONG.?
-I have saw this film yesterday.
我昨天已经看过这电影了.(强调对现在造成的影响.已经看过了.)

现在完成时：过去发生的动作对现在的影响或后果。
如：He has seen the film.( 他看过这部电影，所以他知道电影的内容。）（影响）
He hasn't finished his homewrok, so he can't go out to play.
（他没有完成作业， 所以不能出去玩。）（结果）

过去的事情影响到了现在就用现在完成时

如： I have done my homework and I can play football now.
We haven't seen each other for three years.

现在完成时表示过去的行为对现在的影响或过去的动作一直持续到现在(现在完成时表示现在的过去,并且不可以与确切时间连用,若有确切时间应用一般过去时.)
结构-主语+have(has)+done
例:1表示过去的行为对现在的影响
I have had lunch .
Have you ever been to Paris?
She has gone to Shanghai.
2过去的动作一直持续到现在
I have learnt English for about 2 years.
He has been here since 5 years ago.
错误的表达方法
We have eaten breakfast at 9 o\'clock.
应用一般过去时-We ate breakfast at 9 o\'clock.

现在完成时表示现在已经做完某事，一般用于刚做完或回答是否做完。
have（has）+动词过去分词。
例如：
Do you know how to drive trucks？
Yes，I do。I have driven trucks for many years。
或：
Have you done your homework？
Yes，I have。I did my homework a little while ago。

现在完成时表达至今的结果;影响
如: I have finished my homework, ( so I can play outside now.)