高中英語知識點：Since從句和名詞性從句的用法
Since從句的用法
1. Since從句為非延續性動詞的過去時或現在完成時，時間的起點應該從從句動作完成時刻算起。
例如：
Things have changed a lot since I wrote to you last time.
自我上次給你寫信之后，情況已發生了很大的變化。
She has lived with us since she has come here.
自從她來到這里，就一直和我們住在一起。
2. Since從句為延續性動詞的一般過去時，表示動作或狀態的結束。其含義與動詞的詞義恰好相反，具有否定意味。
例如：
All has changed since he was at home.
自從他離開家以后，這里的一切都變了。
I havent written to her since she lived in London.
自從離開倫敦以來，我還沒有給她寫過信。
He has never been to see me since I was ill.
自從我病愈以來，他一直沒有來看我。
Two years have passed since I last smoked.
我戒煙已經兩年了。
但如果since從句是延續性動詞的現在完成時，則表示動作由開始延續至說話的時候，具有肯定意味。
例如：
He has never been to see me since I have been ill.
自從我生病以來，他一直沒有來看我。
She has talked little since she has stayed at home.
自從她呆在家里以后，就很少講話。
Since we have owned a car， we have gone camping every year.
自從我們有了汽車后，年年都去野營。
3. 在現代英語中，since從句是延續性動詞的一般過去時，有時候也可以表示肯定意味。此時，多半用ever來加強since的語義。
例如：
She has known me ever since she was a child.
她從小就認識我了。
I have live here ever since I was born.
我生下來就住在這里。
4. 在it is+時間+since從句結構中，since從句是非延續性動詞的一般過去時，含有肯定意味。
例如：
It is three years since her husband left her.
她丈夫離開她已經3年了。
It is over sixty years since the Peoples Republic of China was established.
中華人民共和國已經成立60多年了。
5. 在it is+時間+since從句結構中，since從句是延續性動詞的一般過去時，含有否定的意味。
例如：
It is three years since she stayed here.
她離開這里已經3年了。
How long is it since you were a league member?
你退團有多久了?
6. 在it is+時間+since從句結構中，since從句是現在完成時或過去完成時，均含有否定意味。
例如：
It is five years since we have seen her.
我們已經5年沒有見她了。
It was years since I had seen her.
在那之前，我已經有好久沒有見到她了。
Its been a long time since Ive seen you.
我已經很久沒有見到你了。
另外，①根據英語慣用法，since從句不可以否定形式出現。
例如：
It is four years since I have smoked a cigarette. 我已經4年不抽煙了。
不可說：It is four years since I havent smoked a cigarette.
但由于下句中的since不作自從解，所以從句可以用否定形式。
例如：
I havent been out anywhere since I dont know how long.
也不知多久了，我哪兒也沒去過。
②Since從句通常不與非延續性動詞的現在完成時的肯定式連用。
例如：
Her mother died when she was a child.
她小時候母親就去世了。
不可說：Her mother has died since she was a child.
③Since前不可加表示時間的詞語，但可以與ago連用。
例如：
She has lived with us since her mother died three years ago.
自從她母親3年前去世，她就一直和我們住在一起。
不可說：She has lived with us three years since her mother died.
④在It was five years ago since his father died. 一句中的since用錯了，因為在含有ago的時間范疇里，已經有了從過去的一個時間點以來的時間，即已有了since的時間范疇，所以再用since是多余的。
改為：
It was five years ago that his father died.
他父親5年前去世了。
It is five years since his father died.
他父親去世已經5年了。
名詞從句的用法
一.主語從句
主語從句是在復合句中充當主語的從句，通常放在主句謂語動詞之前或由形式主語it代替，而本身放在句子末尾。
1. It 作形式主語和it引導強調句的比較。
It 作形式主語代替主語從句，主要是為了平衡句子結構，主語從句的連接詞沒有變化。而it引導的強調句則是對句子某一部分進行強調，無論強調的是什么成分，都可用連詞that。被強調部分指人是也可用who/whom。
例如：
It is a pity that you didnt go to see the film.
It doesnt interest me whether you succeed or not.
It is in the morning that the murder took place.
It is John that broke the window.
2. 用it 作形式主語的結構。
(1) It is +名詞+從句
It is a fact that 事實是
It is an honor that 非常榮幸
It is common knowledge that 是常識
(2) it is +形容詞+從句
It is natural that 很自然
It is strange that 奇怪的是
(3) it is +不及物動詞+從句
It seems that 似乎
It happened that 碰巧
(4) it +過去分詞+從句
It is reported that 據報道
It has been proved that 已證實
3. 主語從句不可位于句首的五種情況。
(1) if 引導的主語從句不可居于復合句句首。
(2) It is said ， (reported) 結構中的主語從句不可提前。
例如：
It is said that President Jingo will visit our school next week. (right)
That President Jiang will visit our school next week is said. (wrong)
(3) It happens， It occurs 結構中的主語從句不可提前。
例如：
It occurred to him that he failed in the examination. (right)
That he failed in the examination occurred to him. (wrong)
(4) It doesnt matter how/whether 結構中的主語從句不可提前。
例如：
It doesnt matter whether he is wrong or not. (right)
Whether he is wrong or not doesnt matter. (wrong)
(5) 含主語從句的復合句是疑問句時，主語從句不可提前。
例如：
Is it likely that it will rain in the evening? (right)
Is that will rain in the evening likely? (wrong)
4. What 與that 在引導主語從句時的區別。
What 引導主語從句時在句時在從句中充當句子成分，如主語.賓語.表語，而that 則不然。
例如：
1) What you said yesterday is right.
2) That she is still alive is a consolation.
二.賓語從句
賓語從句就是在復合句中作賓語的名詞性從句，通常放在主句謂語動詞(及物動詞)或介詞之后。
1. 作動詞的賓語。
(1) 由that引導的賓語從句(that 通常可以省略)
例如：
I heard that be joined the army.
(2) 由what， whether (if) 引導的賓語從句
例如：
1) She did not know what had happened.
2) I wonder whether you can change this note for me.
(3) 動詞+間接賓語+賓語從句
例如：
She told me that she would accept my invitation.
2. 作介詞的賓語。
例如：
Our success depends upon how well we can cooperate with one another.
3. 作形容詞的賓語。
例如：
I am afraid (that) Ive made a mistake.
That 引導的從句常跟在下列形容詞后作賓語：
Anxious， aware， certain， confident， convinced， determined， glad， proud， surprised， worried， sorry， thankful， ashamed， disappointed， annoyed， pleased， hurt， satisfied， content 等。也可以將此類詞后的that 從句的看作原因狀語從句。
4. It 可以作為形式賓語。
It 不僅可以作為形式主語，還可以作為形式賓語而真正的賓語that 從句則放在句尾，特別是在帶復合賓語的句子中。
例如：
We heard it that she would get married next month..
5. 后邊不能直接跟that 從句的動詞。
這類動詞有Allow， refuse， let， like， cause， force， admire， condemn， celebrate， dislike， love， help， take， forgive等。這類詞后可以用不定式或動名詞作賓語，但不可以用that引導的賓語從句。
例如：
I admire their winning the match. (right)
I admire that they won the match. (wrong)
6. 不可用that從句作直接賓語的動詞。
有些動詞不可用于動詞+間接賓語+that從句結構中，常見的有Envy， order， accuse， refuse， impress， forgive， blame， denounce， advise， congratulate等。
例如：
He impressed the manager as an honest man. (right)
He impressed the manager that he was an honest man. (wrong)
7. 否定的轉移
若主句謂語動詞為Think， consider， wuppose， believe， expect， fancy， guess， imagine等，其后的賓語從句若含有否定意義，一般要把否定詞轉移到主句謂語上，從句謂語用肯定式。
例如：
I dont think this dress fits you well.(我認為這件衣服不適合你穿。) 三.表語從句
表語從句在復合句中作表語的名詞性從句，放在系動詞之后，一般結構是主語+連系動詞+表語從句。可以接表語從句的連系動詞有be， look， remain， seem等。引導表語從句的that常可省略。另外，常用的還有the reason is that 和It is because 等結構。
例如：
1) The question is whether we can make good preparation in such a short time.
2) This is why we cant get the support of the people
3) But the fact remains that we are behind the other classes.
4) The reason he is late for school is that he missed the early bus.
