第1个回答 2012-06-30
1.现在完成时不能单独与准确时间连用，（如表示过去的时间状语）
如yesterday(morning、afternoon),last(morning、afternoon）等，除非与for,since连用.
2.现在完成时往往同表示不确定的过去时间状语连用
如already（肯定），yet（否定，疑问），just,before,recently,still,lately,never等：
He has already obtained a scholarship.
I haven't seen much of him recently (lately).
We have seen that film before.
Have they found the missing child yet
3. 现在完成时常常与表示频度的时间状语连用，
如often,sometimes,ever,never,twice,on several occasion等：
Have you ever been to Beijing
I have never heard Bunny say anything against her.
I have used this pen only three times. It is still good.
George has met that gentleman on several occasions.
4. 现在完成时还往往可以同包括现在时间在内的时间状语连用，
如now,up to these few days/weeks/months/years,this morning/week/month/year,just,today,up to present,so far等：
Peter has written six papers so far.
Man has now learned to release energy from the nucleus of the atom.
There has been too much rain in San Francisco this year.
The friendly relations and cooperation between our two countries have been enhanced in the past few years.
Up to the present everything has been successful.
5. 现在完成时还可以用来表示过去的一个时间到现在这段时间内重复发生的动作. We have had four texts this semester.
6.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一时刻并已结束，但该动作对现在产生了影响，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。）
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？
7.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，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，一直住到现在，可能还要继续住下去。）
I have been in the army for more than 5 years.我在部队已经呆了五年多了。（动作开始于5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引导），或表示与现在时刻相连的时间状语（如：up to now，so far）等。
例如：I have heard nothing from him up to now.到目前为止我没有他的任何消息。
注意：（1）现在完成时的未完成用法只适用于延续性动词，不可用于终止性动词，即瞬间完成或延续时间很短的动词。如：come，go，arrive，leave，join，become，die等。
8.一段时间+has passed+since从句
9. 现在完成时常和短语 "up to now /till now","so far" （意思是从过去某一确定的时间一直延续到现在)连用。
Up to/till now he's read many story books. 至今他已读过好多故事书。
I've been to New York three times so far. 至今我已到纽约去过三次。
10 has gone (to),has been (to),has been (in) 的区别
gone：去了没回
been to ：去过
been in：呆了很久
10.不能与when连用
11.不可以与一般过去时的定义混淆
主谓一致：
在英语句子里，谓语受主语支配，其动词必须和主语在人称和数上保持一致，这就叫主谓一致。寻其规律，大致可归纳为三个原则，即语法一致、逻辑意义一致和就近一致原则。
一、语法一致原则
语法上一致就是谓语动词和主语在单、复数形式上保持一致。
1. 以单数名词或代词、动词不定式短语、动名词短语或从句作主语时，谓语动词一般用单数形式；主语为复数时，谓语动词用复数形式。如：His father is working on the farm. / To study English well is not easy. / What he said is very important for us all. / The children were in the classroom two hours ago. / Reading in the sun is bad for your eyes.
注意：由what引导的主语从句，后面的谓语动词多数情况用单数形式，但若表语是复数或what从句是一个带有复数意义的并列结构时，主句的谓语动词用复数形式。如：What I bought were three English books. / What I say and do is （are） helpful to you.
2. 由连接词and或both …… and连接起来的合成主语后面，要用复数形式的谓语动词。如：Lucy and Lily are twins. / She and I are classmates. / The boy and the girl were surprised when they heard the news. / Both she and he are Young Pioneers.
注意：（1）若and所连接的两个词是指同一个人或物时，它后面的谓语动词就应用单数形式。如：The writer and artist has come. （2）由and连接的并列单数主语前如果分别有no， each， every more than a （an） ， many a （an）修饰时，其谓语动词要用单数形式。如：Every student and every teacher was in the room. / No boy and no girl likes it.
3. 主语为单数名词或代词，尽管后面跟有with， together with， except， but， like， as well as， rather than， more than， no less than， besides， including等引起的短语，谓语动词仍用单数形式；若主语为复数，谓语用复数形式。如：Mr. Green， together with his wife and children， has come to China. / Nobody but Jim and Mike was on the playground. / She， like you and Tom， is very tall.
4. either， neither， each， every 或no +单数名词和由some， any， no， every构成的复合不定代词，都作单数看待。如：Each of us has a new book. / Everything around us is matter.
注意：（1）在口语中当either或neither后跟有“of+复数名词（或代词）”作主语时，其谓语动词也可用复数。如：Neither of the texts is （are） interesting. （2）若none of后面的名词是不可数名词，它的谓语动词就要用单数；若它后面的名词是复数，它的谓语动词用单数或复数都可以。如：None of us has （have） been to America.
5. 在定语从句时，关系代词that， who， which等作主语时，其谓语动词的数应与句中先行词的数一致。如：He is one of my friends who are working hard. / He is the only one of my friends who is working hard.
6. 如果集体名词指的是整个集体，它的谓语动词用单数；如果它指集体的成员，其谓语动词就用复数形式。这些词有family， class， crowd， committee， population， audience等。如：Class Four is on the third floor. / Class Four are unable to agree upon a monitor.
注意：people， police， cattle等名词一般都用作复数。如：The police are looking for the lost child.
7. 由“a lot of， lots of， plenty of， the rest of， the majority of + 名词”构成的短语以及由“分数或百分数+名词”构成的短语作主语，其谓语动词的数要根据短语中后面名词的数而定。如：There are a lot of people in the classroom. / The rest of the lecture is wonderful. / 50% of the students in our class are girls.
注意：a number of“许多”，作定语修饰复数名词，谓语用复数；the number of“……的数量”，主语是number，谓语用单数。
8. 在倒装句中，谓语动词的数应与其后的主语一致。如：There comes the bus. / On the wall are many pictures. / Such is the result. / Such are the facts.
二、逻辑意义一致原则
逻辑意义一致就是谓语动词的数必须和主语的意义一致（因有时主语形式为单数，但意义为复数；有时形式为复数，但意义为单数）。
1. what， who， which， any， more， all等代词可以是单数，也可是复数，主要靠意思来决定。如：Which is your bag？ / Which are your bags？ / All is going well. / All have gone to Beijing.
2. 表示“时间、重量、长度、价值”等的名词的复数作主语时，谓语动词通常用单数形式，这是由于作主语的名词在概念上是一个整体，如：Thirty minutes is enough for the work.
3. 若英语是书名、片名、格言、剧名、报名、国名等的复数形式，其谓语动词通常用单数形式。如：“The Arabian Nights” is an interesting story-book.
4. 表数量的短语“one and a half”后接复数名词作主语时，其谓语动词可用单数形式（也可用复数。如：One and a half apples is （are） left on the table.
5. 算式中表示数目（字）的主语通常作单数看待，其谓语动词采用单数形式。如：Twelve plus eight is twenty. / Fifty-six divided by eight is seven.
6. 一些学科名词是以 –ics 结尾，如：mathematics， politics， physics 以及news， works等，都属于形式上是复数的名词，实际意义为单数名词，它们作主语时，其谓语动词要用单数形式。如：The paper works was built in 1990. / I think physics isn‘t easy to study.
7. trousers， glasses， clothes， shoes， 等词作主语时，谓语用复数，但如果这些名词前有a （the） pair of等量词修饰时，谓语动词用单数。如：My glasses are broken. / The pair of shoes under the bed is his.
8. “定冠词the + 形容词或分词”，表示某一类人时，动词用复数。
三、就近一致原则
在英语句子中，有时谓语动词的人称和数与最近的主语保持一致。
1. 当两个主语由either …… or， neither …… nor， whether …… or ……， not only …… but also连接时，谓语动词和邻近的主语一致。如：Either the teacher or the students are our friends. / Neither they nor he is wholly right. / Is neither he nor they wholly right？
2. there be句型be动词单复数取决于其后的主语。如果其后是由and连接的两个主语，则应与靠近的那个主语保持一致。如：There are two chairs and a desk in the room.
注意：Here引导的句子用法同上。