雨花区有哪些安置小区:English questions

完成时主要是强调一个动作的发生对于另一时间（A）产生的影响或产生的结果，或者表示一直持续。如果（A）这个时间是现在，则用现在完成时，如果是过去的一点时间，则用过去完成时。
例如：I have learnt Java.（我学过Java语言，学习是过去的事情，对于现在产生影响，即我现在会Java语言）
I had learnt Java before I went to the university.（我上大学以前就学过Java，也就是说上大学这一时间已经是过去了，学习Java是针对该时间而言的，也就是老师常说的过去的过去用过去完成（不过这个解释是不确切的））

现在完成时have done 的时间标志是
in the past few/three years
since + 时间点/ sb dis
副词标志是
already,yet,never,ever
现在完成时可以单独使用

i have finished homework.
但过去完成时不可以单独使用

用在“It is the first/second...time+that”从句中

过去完成时 had done
时间标志
by last year/by the time of

过去完成时一般和过去时一起出现

sb had done sth before sb did
sb did sth after sb had done

用于hardly when, no sooner than的句式中
we had hardly came home when it rained.

用在“It was the first/second...time+that”句型中

1）过去时表示过去某时发生的动作或单纯叙述过去的事情，强调动作；现在完成时为过去发生的，强调过去的事情对现在的影响，强调的是影响。

2）过去时常与具体的时间状语连用，而现在完成时通常与模糊的时间状语连用，或无时间状语。

一般过去时的时间状语:
yesterday, last week，…ago, in1980, in October, just now, 具体的时间状语

共同的时间状语:
this morning, tonight,this April, now, once，before, already, recently，lately

现在完成时的时间状语
for, since, so far, ever, never, just, yet, till / until, up to now, in past years, always,
不确定的时间状语

3）现在完成时可表示持续到现在的动作或状态，动词一般是延续性的，如live, teach, learn, work, study, know.
过去时常用的非持续性动词有come, go, leave, start, die, finish, become, get married等。
举例：
I saw this film yesterday.
（强调看的动作发生过了。）
I have seen this film.
（强调对现在的影响，电影的内容已经知道了。）
Why did you get up so early?
（强调起床的动作已发生过了。）
Who hasn't handed in his paper?
（强调有卷子，可能为不公平竞争。）
She has returned from Paris.
她已从巴黎回来了。
She returned yesterday.
她是昨天回来了。
He has been in the League for three years.
(在团内的状态可延续)
He has been a League member for three years.
(是团员的状态可持续)
He joined the League three years ago.
( 三年前入团，joined为短暂行为。)
I have finished my homework now.

---Will somebody go and get Dr. White?
---He's already been sent for.
句子中如有过去时的时间副词（如 yesterday, last, week, in 1960）时，不能使用现在完成时，要用过去时。
（错）Tom has written a letter to his parents last night.
（对）Tom wrote a letter to his parents last night.