【时态】现在完成时

概念:过去发生或完成的动作对现在造成的影响。

一般用法

I have finished my homework.

我已经写完作业了。

影响是: 不用再写了，可以玩了，不用管我了

一般过去时

I finished my homework yesterday.

昨天我完成了家庭作业。(仅表示昨天发生的一件事)

现在完成时的时间标志

already(已经)  用于肯定句

yet(还，已经) 用于否定句、疑问句 出现在句尾

just(刚好)、so far (目前)、ever(曾经)、never(从来不)、in the past ten years(在过去的十年)

eg

I have not finished my homework yet.

Have  you finished your homework yet? 

Yes, I have  / No, I haven't.

用法

① 表示过去发生或完成的动作对现在的影响

同上

②表示从过去某一个时间开始，并持续到现在而且可能继续下去的动作或状态。

时间标志：for + 时间段，since + 时间点/从句(一般过去时)

1、He has lived here for five years.

2、He has lived here since five years ago.

3、He has lived here since he was a little boy.

表示一段时间的状态，动词要用延续性动词，而不能用短暂性动词。

1、I have bought the interesting book.

      I have had this book for half year.

2、He has come back.

      He has been back for one hour.

3、have gone to  去了(没回来)

      have been to  去过(已回来) + 几次 

      have been in  待在... （时间段）

短暂性动词 → 延续性动词

become → be、begin → be on、come back →be back、come/arrive → be in/here、leave → be away/ out、close → be closed、open → be open、join → be in、sit down→be seated、marry→be married、fall ill →be ill、fall sleep → be sleep、finish→be over、get up→be up、buy→have、borrow→keep、put on→wear、move to→live in、catch a cold → have a cold