at first “开始”、“最初”、“起初”， 口语用语，相当于initially，其反
意短语是 at last。
1）At first / Initially he opposed the plan， but later he changed her mind
and decided to give them some necessary help.
起初他反对这个计划，但后来他改变了主意，决定给他们一些必要的帮助。
2）At first I thought he was joking but then I realized he meant it.
起初我以为他是在开玩笑，但后来我意识到他是有意的。
3）The drugs work well at first but gradually lose their effectiveness.
这些药的效果起初非常好，但后来逐渐失效
