英語中虛擬語氣的用法很多。在英語教學(xué)的過程中，我們常常發(fā)現(xiàn)有些學(xué)生對(duì)各種虛擬語氣結(jié)構(gòu)中的動(dòng)詞是用現(xiàn)在虛擬式還是過去虛擬式分辨不清，下面我就這個(gè)問題作一一說明?！?BR> 1．表示有可能實(shí)現(xiàn)的意愿的虛擬結(jié)構(gòu)中，動(dòng)詞常用現(xiàn)在虛擬式：
（1）it is + adj + that +sb + do/be + sth
該結(jié)構(gòu)中的主語從句表示說話人的意愿或主觀態(tài)度，結(jié)構(gòu)中的形容詞用來表現(xiàn)說者的意愿趨向, 從句中的動(dòng)詞應(yīng)用現(xiàn)在虛擬式?？捎糜谠摻Y(jié)構(gòu)中的形容詞包括 advisable, appropriate, crucial, desirable, essential, fitting, imperative（必要的）, important, impossible, natural, necessary, obligatory（必須）, preferable（更好的）, proper, sad, strange, surprising, vital（至關(guān)重要的）等。
如：it is necessary that the car be checked thoroughly.
it was important that she have confidence in herself.
（2） s1 + v + that s2 + do sth
在帶有賓語從句的英語句子中，如主句中的謂語動(dòng)詞表示以下有可能實(shí)現(xiàn)的意愿時(shí)，從句中的動(dòng)詞應(yīng)用現(xiàn)在虛擬式：
<1> 要求: ask, beg, demand, insist, request, require,
<2> 建議: advise, advocate, propose, recommend, suggest
<3> 命令: command, direct（命令, decree（裁決）instruct, move, order, urge, stipulate。
<4> 愿望: desire, expect, prefer（寧愿）。
<5> 決定：decide。
如：he insisted that you be on time.
it is desired that we get everything ready by tonight.
the commanding officer decided that no one be admitted without a special pass.
（3）n+(…) that +sb +do sth
表示要求、建議、命令、愿望、決定等意義的名詞后如有其同位語從句或表語從句時(shí)，這類從句中的動(dòng)詞應(yīng)用現(xiàn)在虛擬式。適用于該句型的名詞有advice, conviction, decision, decree, demand, idea, motion, necessity, order, plan, preference, proposal, recommendation, requirement, resolution (決議), suggestion, wish。
如：my idea is that we go right now.
the resolution that women be allowed to vote was carried.
（4）fear/be afraid/worried lest sb do sth 表示害怕(擔(dān)心)某種可能出現(xiàn)的情況，從句中的動(dòng)詞應(yīng)用現(xiàn)在虛擬式。
如: i fear lest he arrive too late.
we were afraid lest it be stolen.
he was at once worried lest she leave him.
2．在用來表示不太可能實(shí)現(xiàn)的意愿或假設(shè)的虛擬結(jié)構(gòu)中，動(dòng)詞常用過去虛擬式：
（1）would that sb did sth/ had done sth
該結(jié)構(gòu)表示與現(xiàn)實(shí)相反的愿望（would充當(dāng)及物動(dòng)詞），that從句中的動(dòng)詞應(yīng)用過去虛擬式。
如：would that i were a student again.
would that you didn’t refuse my proposal of marriage（求婚）.
would that i had told him the change last friday.
（2）if only
if only有兩種主要用法:
① 表示目前較難實(shí)現(xiàn)的愿望或與過去事實(shí)相反的愿望。表示目前較難實(shí)現(xiàn)的愿望時(shí)使
if only sb+ did/were sth 或 if only sb could/would do/be sth的結(jié)構(gòu)；表示與過去事實(shí)相反的愿望時(shí)使用if only sb had done/been sth 或 if only sb could have done sth的結(jié)構(gòu)。
如：oh, if he could only come
if only you would listen to reason.
if only i could have gone to the movies.
if only you hadn’t told linda what i said.
② if only 還可帶一個(gè)條件狀語從句，該條件句表示一種較難兌現(xiàn)的條件。
如：if only you would help me type my paper this afternoon, i would not have to burn the midnight oil.
if only they were here now, we would be able to discuss the issue together.
（3）but for和except for（若非）
but for 和except for均需置于句首，其后均可接名詞短語，表示與事實(shí)相反的假設(shè)或條件，其后句子中的謂語要用should/would/could (not)do/be…來表示對(duì)現(xiàn)在的虛擬；而用should/would (not) have done/been… 來表示對(duì)過去的虛擬。
如：but/except for air and water, nothing could live in the earth.
（1）it is + adj + that +sb + do/be + sth
該結(jié)構(gòu)中的主語從句表示說話人的意愿或主觀態(tài)度，結(jié)構(gòu)中的形容詞用來表現(xiàn)說者的意愿趨向, 從句中的動(dòng)詞應(yīng)用現(xiàn)在虛擬式?？捎糜谠摻Y(jié)構(gòu)中的形容詞包括 advisable, appropriate, crucial, desirable, essential, fitting, imperative（必要的）, important, impossible, natural, necessary, obligatory（必須）, preferable（更好的）, proper, sad, strange, surprising, vital（至關(guān)重要的）等。
如：it is necessary that the car be checked thoroughly.
it was important that she have confidence in herself.
（2） s1 + v + that s2 + do sth
在帶有賓語從句的英語句子中，如主句中的謂語動(dòng)詞表示以下有可能實(shí)現(xiàn)的意愿時(shí)，從句中的動(dòng)詞應(yīng)用現(xiàn)在虛擬式：
<1> 要求: ask, beg, demand, insist, request, require,
<2> 建議: advise, advocate, propose, recommend, suggest
<3> 命令: command, direct（命令, decree（裁決）instruct, move, order, urge, stipulate。
<4> 愿望: desire, expect, prefer（寧愿）。
<5> 決定：decide。
如：he insisted that you be on time.
it is desired that we get everything ready by tonight.
the commanding officer decided that no one be admitted without a special pass.
（3）n+(…) that +sb +do sth
表示要求、建議、命令、愿望、決定等意義的名詞后如有其同位語從句或表語從句時(shí)，這類從句中的動(dòng)詞應(yīng)用現(xiàn)在虛擬式。適用于該句型的名詞有advice, conviction, decision, decree, demand, idea, motion, necessity, order, plan, preference, proposal, recommendation, requirement, resolution (決議), suggestion, wish。
如：my idea is that we go right now.
the resolution that women be allowed to vote was carried.
（4）fear/be afraid/worried lest sb do sth 表示害怕(擔(dān)心)某種可能出現(xiàn)的情況，從句中的動(dòng)詞應(yīng)用現(xiàn)在虛擬式。
如: i fear lest he arrive too late.
we were afraid lest it be stolen.
he was at once worried lest she leave him.
2．在用來表示不太可能實(shí)現(xiàn)的意愿或假設(shè)的虛擬結(jié)構(gòu)中，動(dòng)詞常用過去虛擬式：
（1）would that sb did sth/ had done sth
該結(jié)構(gòu)表示與現(xiàn)實(shí)相反的愿望（would充當(dāng)及物動(dòng)詞），that從句中的動(dòng)詞應(yīng)用過去虛擬式。
如：would that i were a student again.
would that you didn’t refuse my proposal of marriage（求婚）.
would that i had told him the change last friday.
（2）if only
if only有兩種主要用法:
① 表示目前較難實(shí)現(xiàn)的愿望或與過去事實(shí)相反的愿望。表示目前較難實(shí)現(xiàn)的愿望時(shí)使
if only sb+ did/were sth 或 if only sb could/would do/be sth的結(jié)構(gòu)；表示與過去事實(shí)相反的愿望時(shí)使用if only sb had done/been sth 或 if only sb could have done sth的結(jié)構(gòu)。
如：oh, if he could only come
if only you would listen to reason.
if only i could have gone to the movies.
if only you hadn’t told linda what i said.
② if only 還可帶一個(gè)條件狀語從句，該條件句表示一種較難兌現(xiàn)的條件。
如：if only you would help me type my paper this afternoon, i would not have to burn the midnight oil.
if only they were here now, we would be able to discuss the issue together.
（3）but for和except for（若非）
but for 和except for均需置于句首，其后均可接名詞短語，表示與事實(shí)相反的假設(shè)或條件，其后句子中的謂語要用should/would/could (not)do/be…來表示對(duì)現(xiàn)在的虛擬；而用should/would (not) have done/been… 來表示對(duì)過去的虛擬。
如：but/except for air and water, nothing could live in the earth.