现在完成时是英语动词所特有的一个时态，一直是中国学生学习的一个难点。要掌握这一时态，不但要明确其基本特征，更要了解其判别方法。

　　一、现在完成时的"完成用法"和"未完成用法"

　　1.现在完成时的"完成用法"

　　现在完成时的"完成用法"指的是动作发生在过去某时刻并已结束，但该动作影响到现在，与现在情况具有因果关系。例如：

　　He has turned off the light.他已把灯关了。(动作结束于过去，但说明的是现在的情况--灯现在不亮了。)

　　Who has opened the window?谁把窗子打开了？(动作发生在过去，但说明的是现在的情况--现在窗子开着呢。)

　　现在完成时"完成用法"的特点是动作不延续，因此，该时态只能与表示不定的过去时间状语(如：already,yet,before,recently等)、频度时间状语(如：never,ever,once等)、包括现在时刻在内的时间状语(如：this morning／month／year...,today等)连用。例如：

　　Have you found your pen yet?你已找到你的钢笔了吗？

　　I haven't seen him recently.我最近没有见到他。

　　I've been there once or twice.我去过那里一两次。

　　I have written two letters this morning.今天上午我写了两封信。

　　2.现在完成时的"未完成用法"

　　现在完成时的"未完成用法"指的是动作开始于过去某一时刻，一直延续到现在，刚刚结束，或可能还要继续下去。例如：

　　He has lived here since 1978.自从1978年以来，他一直住在这儿。(动作起始于1978年，一直延续到现在，可能还要继续下去。)

　　I have lived here for more than 30years.我在这儿已住了三十多年了。(动作开始于30多年前，一直延续至今，有可能还要继续下去。)

　　此种用法的句中常需一个表示一段时间的状语(由since或for引出)，或表示与现在时刻相连的时间状语(如：up to now,so far等)，或all day之类的状语。例如：

　　I have heard nothing from him up to now.到目前为止我没听到他的任何消息。

　　My mother is ill again.She has been in poor health all her life.我母亲又病了。她这一辈子身体一直不好。

　　注意：因为此种用法的动作是持续的，现在完成时的未完成用法只适用于持续性动词，不可用于终止性动词，即瞬间完成或持续时间很短的动词。如：come,go,arrive,leave,join,become,die等。如果要表达这类动作发生了多长时间，需采用下列表达法：

　　1)状态动词be＋表语＋for短语

　　2)It is /has been＋一段时间＋since从句

　　请看下例：

　　He has been back for three days.或It has been three days since he came back.(取代has come back)他已回来三天了。

　　He has been in the army for three years.或It is three years since he joined the army.(取代has joined)他参军已三年了。

　　They have been away for two hours.或It has been two hours since they left.(取代have left)他们已走了两个小时了。

　　二、现在完成时的判别

　　1.当表示不确定的过去时间副词，如al ready,yet,ever,never,al- ways等作状语说明现在的情况时，多用现在完成时。例如：

　　"Have you ever seen a wolf?""No，I've never seen one.""你见过狼吗？""没有，我从来没见过。"

　　Have you finished reading it yet?你读完了吗？

　　I've already done enough harm to her.我对她的伤害已经够多的了。

　　2.当(ever)since短语、介词for短语、since引起的短语或从句作状语的句子涉及现在的情况时，用现在完成时。例如：

　　She went to Shanghai in 1978and has lived there ever since.她1978年去了上海，此后一直住在那里。

　　He has been in prison for five years.他已被监禁五年了。

　　3.当有一个表示"迄今为止"含义的短语作状语时，一定要用现在完成时。这类短语常见的有：so far,up till now,up to now,up to the present,until now,as yet等。例如：

　　So far I have read only 30pages.到目前为止我才读了30页。

　　As yet we haven't made any plans for our trip to Hangzhou.到目前为止，我们还没有做好去杭州的安排。

　　Up till now,we have planted over 24,000 fruit trees.至今，我们已栽了24000棵果树。

　　4.当表示最近的过去的词语作状语时，多用现在完成时。这类词语常见的有：in the last /past few years /weeks /days...,for the last /past few years /weeks /days...,recently,lately,these few days等。例如：

　　I've only recently begun to learn Chinese.我只是最近才开始学中文。

　　He hasn't had anything to eat for the last twelve hours.在过去的12个小时里他什么都没吃。

　　It is obvious that enemy forces have built up greatly in that area in the last few days.很明显，在过去的几天里，敌人在那个地区集结了很多兵力。

　　5.当用all day,all this year,all one's life,this morning /afternoon /week...这类表示一段时间的短语作状语，而且这段时间还没过去，仍包含现在时间在内时，要用现在完成时。例如：

　　My father has repaired two bicycles this morning.今天上午爸爸修了两台自行车。(说话时仍是上午)

　　My parents has lived in that small town all their lives.我父母一生都住在那个小镇里。(说话时父母仍健在)

　　6.下列句型的从句中要用现在完成时：

　　It(This /That)is the first time(that)...

　　It(This /That)is the only /the first /the

　　best...(that)...

　　例如：

　　It is the third time she has been to Beijing this year.这是她今年第三次去北京了。

　　This is the best beer that I have ever drunk.这是我所喝过的最好的啤酒。

　　This is the only party that I've ever really enjoyed in my life.这是我一生中唯一的一次真正玩得开心的聚会。

　　Exercises：

　　1.So far,she _______ her holiday very much.

　　A.has not enjoyed B.did not enjoy

　　C.doesn't enjoy D.was not enjoying

　　2.John caught a cold on Saturday and _______ in bed ever since.

　　A.was B.has been

　　C.is D.have been

　　3.All of those houses _______ in the last ten years.

　　A.were built B.had been built

　　C.have been built D.have built

　　4.I _______ to speak to you for these days.

　　A.want B.wanted

　　C.had wanted D.have wanted

　　5.This is the first time that I _______ really relaxed for months.

　　A.had felt B.felt

　　C.have felt D.am feeling

　　6.There _______ a lot of changes in our city recently.

　　A.are B.have been

　　C.has been D.were

　　7.It's one of the most interesting books that _______.

　　A.I've ever read B.I read

　　C.I had ever read D.I am reading

　　8."Where is your uncle's home?"" _______ in Boston for the past four years."

　　A.He's lived B.He's living

　　C.He lived D.He lives

　　9.Lead _______ as material for sculpture since the time of the early Greeks.

　　A.has used B.has been used

　　C.are used D.was used

　　10.As yet we _______ any plans for the holiday.

　　A.did not make B.have not made

　　C.don't make D.would not make

　　Key：1.A 2.B 3.C 4.D 5.C

　　6.B 7.A 8.A 9.B 10.B

　　(文/吉林化工学院孙杰；英语通大学英语六级考试版2003年第10期；版权归英语辅导报社所有，独家网络合作伙伴新浪教育，未经许可，不得以任何形式进行转载。)