现在完成时是初中英语中难度较大却又十分重要的语法项目，中考英语试题中也常常涉及这一时态。下 面分三步来深入地剖析现在完成时。 第一步：看“标志”，定时态
一般情况下，句子的时态可以根据句中的一些标志性的词或词组来确定，现在完成时也不例外。根据以下词或短语，可以确定句子要用现在完成时。
1. 常出现在句首的“标志”
so far（到目前为止）
如：
So far we have learned more than 2000 words.
到目前为止，我们已经学了两千多个单词了。
2. 常出现在句中的“标志”
①ever（曾经）
常用于疑问句中。如：
Have you ever been there before?
你以前去过那儿吗？
②never（从来没有）
一般用于否定句中。如：
I have never seen such beautiful flowers.
我从来没见过这么漂亮的花。
③already（已经）
用于肯定句中。如：
I have already finished my work.
我已经完成了我的工作。
already有时也出现在句末。如：
He has seen that film twice already.
那部电影他已经看过两遍了。
already还可用在疑问句中，表示感到惊讶或意外。如：
Have you eaten your dinner already?
你已经吃过饭了？（比想象的要早）
④just（刚刚）
如：
She has just left the classroom.
她刚刚离开教室。
3. 常出现在句末的“标志”
①ever since（自从那时起）
如：
They have worked in that hospital ever since.
自从那时起，他们一直在那家医院工作。
②before（以前）
如：
I’ve never seen such an interesting book before.
以前我从未看过如此有趣的书。
③yet（已经；还，尚）
yet用于疑问句中，表示“已经”；用于否定句中，表示“还，尚”。如：
Have you found my wallet yet?
你已经找到我的钱包了吗？
He has not come yet.
他还没来。
④these days（这些天）
如：
They have been surfing these days.
这些天他们一直在冲浪。
4．since + 时间点
如：
I have known him since 20 years ago.
我自从二十年前就认识他。
for + 时间段
如：
We have worked here for 6 years.
我们已经在这里工作六年了。
现在完成时属于现在时态，所以也可以和now, today, this morning, by now, up to now, recently, lately等表示现在的时间状语连用。如：
We have had three lessons this morning.
今天上午我们已经上了三节课了。
第二步：明确时态构成
现在完成时的基本构成是：主语 + have / has + 过去分词。在使用这一时态时，要特别注意以下两点。
（1）主语的人称和数决定助动词have / has的人称和数。
当主语是he, she, it, my brother, Lucy等第三人称单数形式时，助动词用has；当主语是其他形式时，助动词用have。如：
The man with a dog has gone.
带着一条狗的那个人已经走了。
Nobody has been there before.
以前从没有人去过那里。
My brothers have gone to that village.
我的兄弟们已经去那个村子了。
（2）现在完成时变为否定式和疑问式的变化规律。
否定式的一般构成方式为：主语+ have / has + not + 过去分词+ ... .
一般疑问式的构成方式为：Have / Has +主语+过去分词+ ...？
特殊疑问式的构成方式为：疑问词+ have / has +过去分词+ ...？
如：
They have not finished their work yet.
他们还没完成他们的工作呢。
Has his parent told him not to be late for school?
他的家长告诉过他上学不要迟到吗？
Who has borrowed 3 books from the school library?
谁已经从学校图书馆借过三本书了？
第三步：难点解析
现在完成时可以表达三种意思。
（1）已经做完了某事。
如：
He has killed hundreds of dogs.
他已经杀了数百条狗了。
We have finished our homework on time.
我们已经按时完成了家庭作业。
（2）过去发生的动作对现在造成的影响或产生的结果。
如：
I have had breakfast.
我已经吃过早饭了。（我现在不饿）
―Where is Tom?
―He has gone to No.1 Middle School.
――汤姆在哪儿？
――他已经去一中了。 （他现在不在这里）
（3）动作开始于过去并一直持续到现在。
表达此含意的句子必须满足以下两个条件。
①谓语动词是延续性动词或系表结构。
②句子中有一个由for, since或ever since引导的时间状语。
如：
We have known each other for two years.
我们俩已经认识两年了。
We have known each other since he moved here.
自从他搬到这儿来，我们俩就认识了。
They have been good friends ever since.
从那时起，他们就是好朋友了。
表达这种意思的时候，现在完成时的用法与现在完成进行时的用法非常接近。如：
He has worked in that hospital since he came here last year.
= He has been working in that hospital since he came here last year.
自从他去年到这儿，他就一直在那家医院工作。（他现在仍在那里工作）
They have sat there for half an hour.
= They have been sitting there for half an hour.
他们已经在那儿坐了半小时了。（他们现在仍坐在那里）
类似用法的动词还有study， teach等。
如果用非延续性动词作现在完成时的谓语，则句中不可以有由for或since引导的时间状语。另外，非延续性动词也不可以用于以how long开头的特殊疑问句中。如：
He has died. （ √）
He has died for 1 year. （ ×）
How long has he been here?（ √）
How long has he lived here? （ ×）
若句子中有由for或since引导的时间状语，可以通过转换的方法来正确地进行表达，一般情况下，可以采取以下三种方法。
方法一：换词
用意思相同的延续性动词替代非延续性动词。如：
方法二：换结构
用表示状态的系表结构（be + adj. / adv.）替代非延续性动词。如：
方法三：换句式
用句式“It is +一段时间+ since + 从句”来表示动作的延续状态。如：
It’s about two weeks since I came back from Beijing.
我从北京回来已经有大约两周的时间了。
[过关验收]
1. ―How long have you ____ China?
―For three years.
A. come back B. returned
C. left D. been away from
2. ―Have you mended your shoes， Bob?
―Yes，I ____ them twenty minutes ago.
A. have mended B. mend
C. had mended D. mended
3. Thestudentsaresorrytohearthatthefamous singer ____ for half an hour.
A. has left B. has gone
C. has been away D. has gone away
4. ―What are you going to do this weekend?
―I ____ yet.
A. haven’t decided B. won’t decide
C. have decided D. didn’t decide
5. ―How long ____ you ____ here?
―For about two years so far.
A. have; studied B. did; live
C. do; stay D. were; swimming
6. ―Have you ever been anywhere for a trip？
―A trip? I ____ away from my hometown even once.
A. went B. have gone
C. have never been D. have been
7. ― ____ you ____ the football match yesterday?
―Yes, I did. It was great.
A. Did; seeB. Have; seen
C. Will; see D. Were; seen
8. ―Did you notice him come in?
―No. I ____ a football game.
A. have watched B. had watched
C. am watching D. was watching
9. How time flies, ten years ____ passed.
A. have B. hasC. is D. are
答案：
1. D 2. D 3. C 4. A 5. A 6. C 7. A8. D9. B
（责任编辑 李爱京）