一only在句首要倒装的情况
Only in this way, can you learn English well.
Only after being asked three times did he come to the meeting.
二only引导的词组或句子放在句首作状语时，通常要用倒装结构。如:
Only in this way can you solve the problem.
只有通过这种方式你才能解决问题。
Only if you study hard can you pass the exam.
只有努力学习才能通过考试。
Only then did I realize my mistake.
只有那时我才意识到错了。
注意：如果放于句首的only所修饰的不是状语时，该句不用倒装。例如：Only John can save me. 只有约翰能够救我。Only some of the children passed the examination. 只有几个孩子通过了考试。
［考题1］____ by keeping down costs will Power Data hold its advantage over other companies. (2006浙江)
A. Only
B. Just
C. Still
D. Yet
［答案］A
［解析］放于句首的only修饰方式状语by keeping down costs时，全句要进行部分倒装，而just, still, yet都无此用法。
［考题2］Only in this way ____ to make improvements in the operating system. (2003上海春) A. you can hope B. you did hope C. can you hope D. did you hope
［答案］C
［解析］only在题干中放于句首并修饰方式状语in this way，全句应进行部分倒装。又由于该句不是介绍过去的情况而是表述现实的一种状况，所以不应采用一般过去时，本题应选C。
［考题3］____ can you expect to get a rise. (2001北京、安徽春)
A. With hard work
B. Although work hard
C. Only with hard work
D. Now that he works hard ［答案］C
［解析］题干中句子的结构显然为部分倒装语序，四个选项中只有C选项修饰方式状语with hard work的only可以引导倒装句，因此本题应选C。
［考题4］Only when your identity has been checked, ____. (2003上海)
A. you are allowed in
B. you will be allowed in
C. will you allow in
D. will you be allowed in
［答案］D
［解析］放于句首的only修饰when引导的时间状语从句时，主句应进行部分倒装(从句中不进行倒装)。
［考题5］Only then ____ how much damage had been caused. (2006陕西)
A. she realized
B. she had realized
C. had she realized
D. did she realize
［答案］D
［解析］放于句首的only修饰时间状语then时，主句应进行部分倒装，而且主句中“她意识到……”这一过去的动作对应的是“已导致损失”这一发生得更早的动作，所以下划线应与后面宾语从句中的过去完成时相呼应，采用一般过去时的形式，据此可以分别排除选项A、B和C而选出D。
三only 的倒装句.only位于句首修饰状语要倒装
只有到那时我才将会有机会实现我的梦想. Only then will I have a chance of achieving my dream（will 是助动词,如果这个句子正过来说就是I will have a chance of achieving my dream only then ）
四在句首的only如果后面跟了副词、介词短语或从句等状语，则主句用倒装结构。如only 后跟的是主语，就不用倒装结构了。例如：
Only when the war was over in 1918 was he able to get back to work．（倒装）
Only in this way can you learn English well．（倒装）
Only after a bitter struggle was the aim achieved．（倒装）
Only the teachers are allowed to use the room．（不倒装）
Only five men were hurt in the accident．（不倒装）
注意，only和所修饰的状语如果不在句首，则不倒装。
The boy was helped out only when his father arrived in a hurry．
Only then did he realize the importance of English
只有在那时候他才意识到英语的重要性。
only then ,是过一小会儿的意思，一般用在句首，引导倒装句。
