if的用法總結
if的用法:表示條件,意思是如果;表示虛擬,意思是假如;表示是否的含義,和whether相同用法,連線賓語從句。
1.(表示條件)如果 ,主句用將來時,if從句用現在時表示將來
He will come if you invite him.
如果你請他,他會來的.
2.(表示虛擬)假如,要是
時態:可以表示過去,現在和將來的情況.它的基本特點是時態退後.
a.同現在事實相反的假設.
句型 :條件從句 主句
一般過去時 should( would) +動詞原形
If they were here,they would help you.
b.表示於過去事實相反的假設.
句型:條件從句 主句
過去完成時 should(would) have+ 過去分詞
If she had worked harder,she would have succeeded.
The rice would not have been burnt if you had been more careful.
If my lawyer had been here last Saturday,he would have prevented me from going.
If he had come yesterday,I should / would have told him about it.
含義:He did not come yesterday,so I did not tell him about it.
If he had not been ill and missed many classes,he would have made greater progress.
含義:He was ill and missed many lessons,so he did not make greater progress.
c.表示對將來的假想
句型:條件從句 主句
一般過去時 should+ 動詞原形
were+ 不定式 would + 動詞原形
should+ 動詞原形
If you succeeded,everything would be all right.
If you should succeed,everything would be all right.
If you were to succeed,everything would be all right.
3.是否 = whether 連線賓語從句
I wonder if she is ill.
不知她是否病了.
-
什麼是北海、中海、南海
位於北京城內故宮和景山的西側,合稱三海。明、清時期稱為西苑。它是中國現存歷史悠久、規模巨集大、佈置精美的宮苑之一。沿革三海的歷史可溯源到10世紀的遼代,當時稱為瑤嶼。它是遼南京城北郊的遊樂之地。金代1153年,金代以遼南京城為都城,稱中都。金大定十九年(117...
-
什麼是手少陽三焦經
十二經脈之一。首載於長沙出土的馬王堆漢墓醫書。其中《帛書·經脈》甲種本,即《足臂十一脈灸經》稱為“臂少陽癬(脈)”;乙種本,即《陰陽十一脈灸經》稱為“耳脈(脈)”。《靈樞·經脈》稱為“三焦手少陽之脈”。現通稱為手少陽三焦經,簡稱三焦經。循行《帛書·經脈...
-
什麼是禁忌
為確保安全有效地用藥而規定在用藥期間須禁止和注意的事項。包括配伍禁忌、證候禁忌、妊娠禁忌和飲食禁忌。配伍禁忌即在配伍用藥時應避免有些藥物一起使用,以免降低、破壞藥效或產生劇烈的毒副作用。十八反和十九畏所包括的藥物即屬配伍禁忌的藥物。證候禁忌指...
-
什麼是運動系統功能檢查
運動系統的主要功能為保護內部器官及活動身體,其活動功能表現最為明顯。其功能的完成除要求運動系統的健康完整外,與神經系統、體內水電解質平衡等均有密切關係。因此運動系統的功能異常可反映運動系統器官、神經精神系統、體液以及其他器官系統的情況。運動系統...