as是实词还是虚词

　　She used her family's history as a base for her novel.

　　她以她的家族史作为小说的素材。

　　My new job is much the same as the old one.

　　我的新工作和旧工作差不多。

　　Take as much time as you like.

　　你想花多少时间就花多少时间。

　　Research will be needed as a preliminary to taking a decision.

　　作出决定之前需要进行研究。