参考：无忧英语51talk梁颖老师的超实用语法20讲在线课程第6课
lesson 6时态：现在完成时
形式：have/has +done(过去分词）
用法：
1.总结持续到目前的动作或事情。到目前已经--
--how many years have you learnt English?
--I have learnt English for more than 10 years.
完成时态标志：
so far, since, before, in/during the past years, just, already, yet
he has lived in Kunming since 2006.
in the past 30 years, China's economy has developed dramatically.
I have been to London before.
2.表示经历或重复
D：have you traveled a lot, Jane?
J:yes, I've been to lots of places.
D:Really? Have you ever been to China?
J:Yes, I've been to China twice.
D:What about India?
J:No, I have not been to India.
I have watched/seem the film many times. it's wonderful.
She has been to Australia.去过
She has gone to Australia.去了
James is on holiday. he's gone to Italy.
Hello! I've just been to the shops. I've bought lots of things.
Alice isn't here at the moment. She's gone to the shop to get a newspaper.
Tom has been out. he'll be back in about an hour.
are you going to the bank? No, I've already been to the bank.
3.已经完成的动作对现在有影响subtext
oh! I have lost my keys!
I have cut my finger.
we still haven't found what we're looking for.
--would you like something to eat?
--No, thanks. I have just had lunch.
Collecting dolls as a hobby has became increasingly popular during the past fifty years.
I have not attended any parties since I came here.
I went to a party at Sally's apartment last Saturday night.
Jack really needs to get in touch with you. since this morning, he has called here four times trying to reach you.
he called at 9:00,10:00,11:00 and 12:00
we have not met our new neighbours yet, so we don't know their names.
现在完成时VS一般过去时
现在完成时：动作或影响与现在有关
一般过去时：发生在过去，与现在完全无关
she has lived in London since 2013.
She lived in London in 2013.
They have lost their key and they they can't open the door.
They lost the key last Sunday.
She has gone to Italy. (not back)
She has been to Italy three times.
She went to Italy 5 years ago.
完成时常用句型
句型1: it is the first time that I have done something.
it is the first time that I have been to Hongkong.
it is the second time that I have read this book.
句型2:it is/was 最--的事情that I have done
it is the best movie that I have ever seen.
it is the most fantastic movie that I have ever watched.