it is at this time that students realize how

一、这是一个强调句,这里强调的是时间状语,具体结构为——
强调句式：it is ...that
时间状语：at this time
主语：students
谓语动词：realize
并列宾语从句：how much they need to learn and how little time they have to do it.
二、强调句总的结构是——
It is + 强调词语 + that + 其他部分
三、具体应用还可以分为——
1、强调主语：It is + 主语 + that + 谓语动词 + 其他部分.如：
It is students that realize at this time how much they need to learn.正是学生们在这个时候才意识到他们需要学多少.
2、强调其他成分：It is + 强调部分 + that + 主语 + 谓语动词 + 其他部分,如：
It is how much they need to learn that students realize at this time how much they need to learn and how little 学生们在这个时候意识到的正是他们需要学多少.（强调宾语从句）