同学你好，该知识点来自沪江网校《新概念英语2、3、4册连读【双旦特惠班】》的课程，想要更系统的学习，欢迎进入课程学习。不仅可以和更多的同学一起学习，而且还有老师、助教随时的学习指导和知识点解答哦。

同学你好~
no sooner…than…结构中的 no sooner置于句首时，其后引出部分倒装。
No sooner had we left the house than it began to rain. 我们刚离开家就开始下雨了。
No sooner had we reached the airport than the plane took off. 我们刚到机场，飞机就起飞了。

在正式文体中，never, seldom, rarely, little, hardly, scarcely, no sooner, no longer, nowhere 等含有否定意义的副词若位于句首，则其后要用部分倒装：
I shall never forgive him. / Never shall I forgive him. 我永远不会宽恕他。
He seldom goes out for dinner. / Seldom does he go out for dinner. 他很少出去吃饭。

祝同学学习进步~