使用现在完成时重在说明现在的情况，表示过去与现在的关系，强调结果；一般过去时则只涉及过去的行为或状况本身。有时候，说话意图不同，要用不同的时态。比较下列句子：
你讲完了吗?
Have you finished?（如你已讲完，我想接着讲）
Did you finish?（不知我刚才发言时你是否讲完话了）
你听到他那样说了吗?
Have you ever heard him say that?（是否知道）
Did you ever hear him say that?（什么时候听说的）
你听说过这样的事吗?
Have you ever heard of such a thing?（认真提问，希望回答）
Did you ever hear of such a thing?（修辞问句，不要求回答）
我外出时谁来过这里?
Who's been here while I was out?（发现有人来过：东西被人动过）
Who was here while I was out?（一般提问）
我做了什么使他这么生气?
What have I done to make him so angry?（认真提出问题，且对方仍在生气）
What did I do to make him so angry?（过去生气，现在则不一定）
我的主要目的就是找到真正的解决方法。
My chief purpose has been to find out a real solution.（一直在努力）
My chief purpose was to find out a real solution.（过去的努力）
She has lived in Paris for twenty years.她已在巴黎住了20年。（她仍活着，住在巴黎或刚离开）
She lived in Paris for twenty years.她在巴黎住了20年。（她已故去）
I've chosen some novels for you.我为你选了几本小说。（你有小说读了）
I chose some novels and bought them.我挑选了几本小说买下了。
We've learnt a lot from you.我们从你那里学了很多东西。（深表感激）
We learnt a lot during our stay there.我们在那里时学了很多东西。（只谈当时的情况）
Has she got up?她起床了吗?（着重现在）
Did she get up early this morning?她今天早上起床早吗?
We've got no news from her.我们没有得到她的消息。（不知情况如何）
We got news from her last night.我们昨天夜里得到她的消息的。（有确切时间状语，单纯指过去）
Have you invited him?你邀请他了吗?（活动尚未举行）
Did you invite him?你邀请他了吗?（活动已举行过）
Who has taken the pen away?谁把钢笔拿走了?（强调找不着了）
Who took the pen away?谁把钢笔拿走了?（只问是谁拿走了钢笔）
I've lost the ring.我把戒指丢了。（仍在找）
I lost the ring.我把戒指丢了。（也许已找回，也许没有找回）
I haven't seen him this afternoon.我今天下午没有见到他。（现在仍是下午）
I didn't see him this afternoon.我今天下午没有见到他。（现在已不是下午）
We haven't gone anywhere this autumn.今年秋天我们哪儿也没去。（现在仍是秋天）
We didn't go anywhere this autumn.今年秋天我们哪儿也没去。（现在已不是秋天）
I've just seen Professor Grant.He told me the marks.我刚刚见过格兰特教授，他告诉了我的分数。
I have seen him this May.我5月见到他了。（未出5月）
I saw him this May.我今年5月见到他了。（5月过后当年内）
I have lived in the country for the summer.我整个夏天一直住在乡下。（持续到现在）
I lived in the country through/for the summer.整个夏天我都住在乡下。（过去一段时间）
He has never been in love before.他从没恋爱过。
You can put it that it was arranged before.你可以说这是事先安排好的。
他父亲一生残疾。
His father has been an invalid all his life.（现在还活着）
His father was an invalid all his life.（现在已经去世）
【提示】
①have done常可用于祈使句表示命令，但如同所有的祈使句一样，仍然表示将来的意义，相当于stop，get rid of等。例如：
Have done with your tricks.不要再耍手腕了。
You are grown up now and have done with the bad habit.你现在已经长大了，改掉那个坏习惯吧。
②有时可用be代替have，后跟的过去分词起形容词作用，表示一种状态。例如：
She is just arrived.她刚到。（=here）
He is come.他来了。（=here）
He is returned.他回来了。（=back）
She is gone there two weeks.她在那里两周了。（=She is there two weeks.）
The sun is risen.太阳升起了。（=up）
The leaves are fallen.树叶落了。
He is got into bed.他上床睡了。
They are prepared to fight against the flood.他们已准备好同洪水战斗。
③have been后可接不定式。例如：
I have been to see the exhibition.我去看过展览了。
④these days，nowadays，just now一般不用于现在完成时。
Children are much healthier these days.如今，儿童的健康状况更好了。
Trains are comfortable nowadays.而今，坐火车很舒适。
I saw her just now.我刚刚见到她的。
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