现在完成时

现在完成时的构成

现在完成时用于表示现在和过去之间的联系。动作发生在过去，但未指定具体时间点。使用这种时态表达的意思，侧重于事件的结果，而非事件本身。

现在完成时用于以下情况：

• 过去开始并持续到现在的行动或情况。
  I have lived in Nanjin since 1999(我依然住在这)
  They haven’t lived here for years.
  She has worked in the bank for five years.
  We have had the same car for ten years.
  Have you played the piano since you were a child?
• 一件发生在一段尚未结束的时间段内的事情。
  She has been to the cinema twice this week(这周还没结束。)
  I have worked hard this week.
  It has rained a lot this year.
  We haven’t seen her today.
• 从过去一个不确定的时间点开始算，截止到目前，一件事情已经做了很多次。
  We have visited XuanWu lake several times.
  They have seen that film six times
  It has happened several times already.
  She has visited them frequently.
  We have eaten at that restaurant many times.
• 一件刚刚完成的事情，通常用到just。
  I have just finished my homework.
  Have you just finished work?
  I have just eaten.
  We have just seen her.
  Has he just left?
• 一件过去发生的，并对现在产生了影响的事。
  He has read ‘War and Peace.’ (他读过这本书增加了见识.)
  Someone has eaten my soup! (所以我现在没汤喝了)
  Have you seen ‘Gone with the Wind’?
  She has studied Japanese, Russian, and English.

Note：
你只有在描述一件发生的时间不重要或不特别的事情时，才能使用现在完成时。 当你需要具体的给出事件的发生时间时，请使用一般过去时。

现在完成时使用ever，never，already，yet

EVER

副词“ever”和“never”用于表达一个发生于过去某个不确定的时间点的事件。这两个词总是放在主动词之前使用。

疑问句

EXAMPLES
Have you ever been to England?
Has she ever met the Prime Minister?

反问句

EXAMPLES
Haven’t they ever been to Europe?
Haven’t you ever eaten Chinese food?

用NOTHING+EVER或NOBODY+EVER表达否定意义的固定用法

EXAMPLES
Nobody has ever said that to me before.
Nothing like this has ever happened to us.

与’THE FIRST TIME’连用

EXAMPLES
It’s the first time that I’ve ever eaten snails.
This is the first time I’ve ever been to England.

NEVER

Never意味着某件从来没干过的事，它和not…ever意思是一样的。
BE CAREFUL! never和not不能连用。
I haven’t never been to Italy.
I have never been to Italy.

ALREADY

Already用于描述一件此前已经发生过，且不需要在重复做的事。
EXAMPLES
I’ve already drunk three coffees this morning. (= and you’re offering me another one!)
Don’t write to John, I’ve already done it.
这个词也在疑问句中使用:
Have you already written to John?
Has she finished her homework already?
Already可以放在动词的过去分词前使用，也可以放在句子最后使用。
I have already been to Tokyo.
I have been to Tokyo already.

YET

Yet用于表述一件目前为止还没发生的事，它仅用于疑问句和表达否定意味的陈述句。使用时，Yet放在句子末尾。
EXAMPLES
Have you met Judy yet?
I haven’t visited the Tate Gallery yet.
Has he arrived yet?
They haven’t eaten yet.

现在完成时使用for和since

在现在完成时中通过使用for + 一段时间，我们可以描述一件过去发生的事所持续的时间；
通过使用since + 一段时间，我们可以描述一件过去发生的事开始的时间点。
这两个词也可以在过去完成时中使用。
Since只能用于完成时，而for还可以用于一般过去时。

FOR +一段时间

for six years, for a week, for a month, for hours, for two hours.
EXAMPLES

I have worked here for five years.

She has lived here for twenty years.

We have taught at this school for a long time.

Alice has been married for three months.

They have been at the hotel for a week.

SINCE +一段时间

since this morning, since last week, since yesterday, since I was a child, since Wednesday, since 2 o’clock.
EXAMPLES
I have worked here since 1990.

She has lived here since 1980.

We have taught at this school since 1965.

Alice has been married since March 2nd.

They have been at the hotel since last Tuesday.

一般过去时和现在完成时的区别

一般过去时和现在完成时都可以表示过去发生的事，但在具体语境中，二者有一些区别。

• 一般过去时侧重点在陈述过去发生的事情或状态。
  I went to Beijing last month.
  Tom was in China in 2008
• 现在完成时表示截止到说话时，已经发生（不一定结束）的动作或状态。强调造成的结果对现在的影响。
  I have eaten a big apple. 言下之意：我已经饱了，现在不想吃东西了。
• 一般过去时常与表示过去的时间状语连用，如yesterday、last week等。
• 现在完成时与频度副词或表示一段时间的状语连用，如never、this week等。