当already位于句首时能用主谓倒装吗？

no.

否定副词在句首,可引起倒装
当主语在谓语前出现时叫顺序（the natural order）。在某些情况下，我们可以把谓语成分放在主语前面，这种词序叫做倒装（ the inverted order）。

　　倒装分两种：配合语法条例的倒装，叫“grammatical inversion”；配合强调语势的叫“emphatic inversion”。

　　语法上的倒装句是强制性的，包括下列 7 种：
疑问句，如：

　　● Can you do it?

　　● How old are you?

　　● When did you know him?

　　● Why did you elect him as captain?

　　● Which of these apples do you prefer?

　　但疑问代词做主语时，不必倒置，如：

　　● Who is your English teacher?

　　● What happened last night?

　　⒉表示“愿望”的句子，如：

　　● May God bless you.

　　● Long live the king!

　　⒊“There”引导的句子，如：

　　● There are many cars on the road.

　　● There stand some big trees near the river.

　　● There is a security guard outside the bank.

　　⒋感叹句，如：

　　● How beautiful the flower is!

　　● What a smart boy you are!

　　⒌有连接词“so, neither, nor”的句子，如：

　　● Tom can ride a bicycle; so can I.

　　● She can't sing; neither can he.

　　● John has never been late; nor have I.

　　⒍省略连词“if”的条件副词分句，如：

　　● Were I you, I would not do such a thing.

　　● Should the machine break down again, send it back to us.

　　● Had you worked harder, you would have passed.

　　⒎“as, however”连接的让步副词分句，如：

　　● Small as the pen is, it is a powerful weapon.

　　● However busy you are, you should spend some time reading Zaobao weekly.

　　谈过了语法上的倒装句，现在谈强调的倒装句。

　　● Never have I seen such a wicked man.

　　● On no account must this employee be removed.

　　● Not until he told me had I heard anything of it.

　　● No sooner had I left than the rain came.

　　● Up jumped the puppy.

　　● In came John.

　　● Down fell the rotten branches from the tree.

　　● Out came a woman and her maid.
　全部倒装是只将句子中的谓语动词全部置于主语之前。此结构通常只用与一般现在时和　一般过去时。常见的结构有：
　1) here, there, now, then, thus等副词置于句首, 谓语动词常用be, come, go, lie, run。
　　There goes the bell.
　　Then came the chairman.
　　Here is your letter.
　2) 表示运动方向的副词或地点状语置于句首，谓语表示运动的动词。
　　Out rushed a missile from under the bomber.
　　Ahead sat an old woman.
　注意：上述全部倒装的句型结构的主语必须是名词，如果主语是人称代词则不能完全倒装。
　　 Here he comes.　　　　Away they went.



倒装句之部分倒装

　 部分倒装是指将谓语的一部分如助动词或情态倒装至主语之前。如果句中的谓语没有助动词或情态动词，则需添加助动词do, does或did，并将其置于主语之前。

　1)　句首为否定或半否定的词语，如no, not, never, seldom, little, hardly, at no time, in no way, not until… 等。
　　Never have I seen such a performance.
　　Nowhere will you find the answer to this question.
　　Not until the child fell asleep did the mother leave the room.
　当Not until引出主从复合句，主句倒装，从句不倒装。

注意： 如否定词不在句首不倒装。
　　 I have never seen such a performance.
　　 The mother didn't leave the room until the child fell asleep.

典型例题　　

1)　Why can't I smoke here?
　　At no time___ in the meeting-room
A. is smoking permitted　　B.　smoking is permitted
C. smoking is it permitted　D.　does smoking permit
答案A. 这是一个倒装问题。当否定词语置于句首以表示强调时，其句中的主谓须用倒装结构。 这些否定词包括no, little, hardly, seldom, never, not only, not until等。本题的正常语序是 Smoking is permitted in the meeting-room at no time.

2） Not until the early years of the 19th century ___ what heat is.
　　A. man did know　 B. man know　 C. didn't man know　 D. did man know
　答案D.　 看到Not until…的句型，我们知道为一倒装句，答案在C，D 中选一个。
　改写为正常语序为，Man did not know what heat is until the early years of the 19th. 现在将not提前，后面就不能再用否定了,否则意思就变了。




以否定词开头作部分倒装

　 如 Not only…but also, Hardly/Scarcely…when, No sooner… than
　 Not only did he refuse the gift, he also severely criticized the sender.
　 Hardly had she gone out when a student came to visit her.
　 No sooner had she gone out than a student came to visit her.

典型例题
No sooner___ than it began to rain heavily.
A. the game began　　　　　 B.　has the game begun
C. did the game begin　　　 D.　had the game begun
答案D. 以具有否定意义的副词放在句首时，一般采用倒装句(谓语前置)。这类表示否定意义的词有never, seldom, scarcely, little, few, not, hardly, 以及not only…but (also), no sooner…than, hardly… when scarcely… when　等等。

注意：只有当Not only… but also连接两个分句时，才在第一个分句用倒装结构。如果置于句首的Not only… but also仅连接两个并列词语，不可用倒装结构。
　 Not only you but also I am fond of music.