she is feeling no better than yesterday里的yesterday是名词还是副词?

问题描述:

she is feeling no better than yesterday里的yesterday是名词还是副词?

she is feeling no better than (she was) yesterday
原句省略了,she was ,通常在as、than 引导比较状语从句的时候,可以有此类省略,即省略从句的主语和be动词,如
he is as smart as (he was) three years ago