for the past few years用什么时态

　　Medicine marketing has aroused wide interests in various social fields for the past few years.

　　医药市场营销近年来引起了社会各届的广泛关注，医药营销上的种种矛盾日益凸现。

　　Expectations for the past few years were of higher demand, and commodity prices increasing.

　　过去几年的市场预期是，需求不断增长，大宗商品价格也随之上涨。

　　The cross layer design is one of the hot research issues in the field of communication network for the past few years.

　　跨层设计是最近几年通信网络领域研究的热点之一。

　　Yet that's not the theme that's been coming out of science for the past few years.

　　但是这个理论在过去的几年中并没有科学依据。