市面上关于这个问题的论述花里胡哨，不得要点。其本质就是only在修饰状语或状语从句放在句首时，句子（或主句）要采用倒装语序。两个条件要点，一是only位于句首；二是only修饰的是状语或状语从句；此时句子或主句才倒装。具体是：only+状语（状语从句）位于句首时，把句子（主句）中be, have, should, would, can ,could, may, might等助动词提到主语之前，如果没有这些词，需要添加do（does. did）这个助动词来实现部分倒装。请看经典例句：
Only in his dreams does he give expression to his fears.
他只有在梦中表现出恐惧。
Only in this way can the experiment succeed.
惟有这样做，试验才能成功。
Only in this way can the critical mass of participation be reached.
只有这样才能凑足参与人数。
Only then did she realize the stress he was under.
直到那时她才意识到他所承受的压力。
Only now does he see the good of taking exercise.
他这才知道锻炼身体的好处。
Only now have doctors, and allied medical professionals, come to appreciate this.
直到现在医生和相关医学人士才开始对此有所认识。
Only on special occasions would they take it out and let us hold it in our hands, Adeline says ．
阿德琳说,只有在特殊情况下他们才会把它拿出来,让我们拿在手里。高考真题- 2019 浙江
Only then should you set your goals ．
只有这样你才能设定你的目标。高考真题- 2019 全国2
Only then did I learn the unpalatable truth.
直到那时我才得知令人难以接受的真相。
Only by writing things down could I bring some sort of order to the confusion.
只有把东西记下来，我才能从混乱中理出些头绪来。
Only by fully experiencing the depth of our pain can we be healed from it and be done with it.
只有充分感受了深切的痛苦，我们才能从中走出，并将它抛诸脑后。
Only by being him can you hope to outguess him.
只有化作他肚子里的蛔虫才有可能猜出他在想什么。
Only by reasoning can we convince people completely.
只有以理服人，才能使人心悦诚服。
Only by presenting facts and reasoning things out can we convince people.
摆事实、讲道理，才能让人服气。
Only by working hard can you succeed.
只有努力工作你才能成功。
Only by taking part in practice can the young people be toughened and hardened into steel.
年轻人只有通过实际锻炼才能百炼成钢。
Only by shouting was he able to make himself heard.
他只有叫喊才能让别人听到他。
Only under the influence of great ideas, can the young generations have great dreams.
只有在伟大思想的影响下，年轻一代才能有伟大的梦想。
Only with mass direct action will we obtain such change.
只有采取大规模直接行动，我们才会取得这样的改变。
Only with a few people could she be her real self.
只有和几个人在一起时，她才能表现出真实的自我。
Only at dinnertime are we eating together anymore, 74 percent, according to statistics from the report ．
根据这份报告的统计,人们在晚餐时间一起吃饭的几率比较大,达到74%。
高考真题- 2019 全国
Only when the telescope is inclined at an angle of thirty degrees can you see that star.
只有当这架望远镜以30度角倾斜时，你才能看到那颗星星。
Only when each logical step has been checked by other mathematicians will the proof be accepted.
只有每一逻辑步骤都被其他数学家验证之后，证明才能成立。
Only when agriculture is fully developed can industry have sufficient materials and markets.
只有农业发展了，工业才有足够的原料和市场。
Only when a reservoir is built here can we solve our irrigation problem.
除非在这里修个水库，才能解决灌溉问题。
Only when the rain stops can we go outside.
只有当雨停了，我们才能出去。
Only when food and clothing are enough can one behave properly.
衣食足而知礼仪
Only when our theory combines with practice can the former become areliable knowledge.
只有当理论与实践相结合时，它才变成经得住考验的知识。
Only when they got to a safe place, could we regard ourselves as having done our duty.
只有当他们到达安全地方的时候，我们才能认为自己尽到了责任。
Only after countless rewrites did John consider the script ready.
只有经过了无数次修改后，约翰才认为剧本写好了。
Only after she died was I able to appreciate her.
只有到她死后我才认识到她的价值。
Only after he had spoken out the word did he realize he had made a big mistake.
只有当他已经说出那个字后才意识到自己犯了个大错误。
Only after much persuasion from Ellis had she agreed to hold a show at all.
埃利斯劝了她半天后她才同意办一场展览。
Only after he apologized did she forgive him.
（只有在他道歉之后，她才原谅他。
Only after a year of friendly discussion did Ms ． Garza finally say yes ．
经过一年的友好讨论,加尔扎女士终于答应了。
高考真题- 2016 全国1
Only if you study hard will you pass the exam.
只有你努力学习，你才会通过考试。
Only if the red light comes on is there any danger to employees.
只有红灯闪亮时才有危及职工的险情。
Only because he was ill did he not come to school.
只因为他有病了才没有来上学。