a large of是固定搭配吗

不是固定搭配，例如：

1、A large number of people have applied for the job.许多人申请了这工作。

2、Water covers a large proportion of the earth's surface.水覆盖了地球表面的大部分。

3、There were a large number of candidates for the job.有许多求职者申请这份工作。

4、Somewhere along the line a large amount of money went missing.有一笔巨款在某一环节上不翼而飞。

不是。

large是形容词，后面须有名词。如a large amount of， a large quantity of等。

后面修饰可数名词的有 large numbers of等，后面修饰不可数名词的有 a large/great amount of ，large /great amounts of等。

例句：

A large percentage of population live in big cities.    很大比例的人口住在城市。