同义词是at the beginning of，例如：

1、We're going to Japan at the beginning of July.我们七月初要去日本。

2、At the beginning of the war things were looking very doubtful.战争刚开始时，形势看上去很不明朗。

3、At the beginning of the 20th century almost a third of the population lived off the land.20世纪初几乎有三分之一的人口依靠种地为生。