英语语法：当某些副词或状语位于句首时，句子构成部分倒装句

当某些副词或状语位于句首时，句子构成部分倒装
这类副词或状语多表示时间、频率、或者程度，包括有only recently ,always, often, many times 或many a time, particularly, well 等。
Only recently did he have a chance to visit his hometown. 
只是到了最近他才有机会去家乡探望。 
Many a time has he helped me with my English study. 
他曾许多次帮助我学习英语。 
Twice within my lifetime have World Wars taken place. 
在我的一生中发生过两次世界大战。 
Not even once this year have we increased the prices of any goods we sell.
今年我们所出售的商品一次也没有涨过价。
Well do I remember the day when it happened. 
我清楚地记得这件事发生的那一天。