是定语从句。when引导的定语从句和状语从句的区别在于是否有修饰关系,也就是能否在主句中能否找到先行词,若能则是定语从句。when引导的状语从句一般意为:当.....的时候,......样。例如本题的先行词是the year,翻译是我开始与北京工作是在(新中国成立的)那一年。New China was founded修饰the year,所以本题是定语从句。 I feel very happy when you come to see me. 是状语从句,无先行词,意为【当】你(们)来看我【的时候】,我感到很高兴。
定语从句这句话当中,when New China was founded是用来修饰前面的名词year的,所以相当于一个定语的作用,所以是定语从句啊。当该部分独立做为一个时间状语出现,就是状语从句啦。如,When New China was founded, He was only three years old.