only置于句首时一定要用倒装语序吗

1.“only+状语（副词、介词短语、从句等）”放在句首时，句子要用倒装语序。如：

Only here were the police visible in any strength at all

只有在这里才能看到廖廖几个警察。(摘录自《柯林斯高阶英汉双解学习词典》)

Only in this way can we learn English. 只有这样才能学会英语。

Only then did I understand what she meant. 只有到那时我才明白她的意思。

Only when he is selfless can a man be fearless. 只有无私，才能无畏。

Only if a teacher has given permission is a student allowed to enter this room. 只有得到教师的允许，学生才可以进这间屋。

Only by shouting was he able to make himself heard. 他只有叫喊才能让别人听到他。

注意1，在only后作状语的是从句即使位于句首时，从句始终不要用倒装，要部分倒装的是主句。如：

Only when it rains do you feel cool. 只有下雨时才觉得凉爽一点。

Only when he returned home did he realize what had happened. 当他回到家里时，才知道出了什么事。

Only when we landed did we see how badly the plane had been damaged. 我们只是在着陆之后才看到飞机损坏的严重程度。

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。

注意2，only和所修饰的状语如果不在句首，则不倒装。

如：

The boy was helped out only when his father arrived in a hurry．

那男孩只有在父亲匆忙赶到时才得到帮助。（不要倒装）

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。（要倒装）

2.即使所处位置在句首，若only后接的不是状语，而是主语或宾语，则通常无需倒装。如：

Only the teachers are allowed to use the room．

只有老师们才可以用那个房间。

Only five men were hurt in the accident． Only those who had booked in advance were allowed in. 只有那些预先订票的人可以进去。

Only part of his story is true. 他说的事只有部分是真的。

Only his sister he saw there. 他在那儿只看到他妹妹。

Only a policeman the children saw in the street.

孩子们在街上只看到一个警察。

Only the President could authorize the use of the atomic bomb

只有总统才能授权使用原子弹。(摘录自《柯林斯高阶英汉双解学习词典》)

Only a minority of the people supported the Revolution.

只有少数人支持这场革命。

(摘录自《柯林斯高阶英汉双解学习词典》)