由as soon as, 等引导的时间状语从句。

这些连词都表示“一……就”。例如：

I will go there directly I have finished my breakfast. 吃完早饭，我立即到那里去。

The moment I heard the news, I hastened to the spot.我一听到消息，马上赶到了出事地点。

As soon as I reach Canada, I will ring you up. 我一到加拿大，就给你来电话。

注意：hardly(scarcely, rarely)…when / before, no sooner…than相当于as soon as之意。主句用过去完成时，从句用一般过去时。当hardly, scarcely, rarely和no sooner位于句首时，主句应用倒装语序。例如：

He had no sooner arrived home than he was asked to start on another journey. 他刚到家，就被邀请开始另一旅程。

No sooner had the sun shown itself above the horizon than he got out of bed to commence work.太阳刚从地平线上升起，他就起床劳动去了。

Hardly had I sat down when he stepped in.我刚坐下，他就进来了。

He had hardly fallen asleep when he felt a soft touch on his shoulder.这个阿拉伯人刚要入睡就感到肩膀上被轻轻一触。