His research began with fruit flies, but over the last two decades, his focus has been on parasitic protozoa, single-celled organisms that cause major diseases.

VOA: standard.2010.04.05

We've gotten, over the last two decades in particular, very sophisticated about taking pictures inside the body allowing doctors to look inside the body and predict things about our internal physiology that they couldn't predict just by looking at us or putting their hands on us.

特别是在近二十年当中,我们对体内造影已经十分熟悉,它使医生能够看到身体内部,并预测我们体内的生理变化,而仅仅是通过,视诊或者触诊是不能预测这些变化的

耶鲁公开课 - 生物医学工程探索课程节选

Mr.Orban,47,told parliament that he realizes he takes over a country mired in political tensions and struggling to overcome its deepest recession in nearly two decades.

VOA: standard.2010.05.29

Statistics from Australia's National Tidal Center show sea levels have increased by 8.6 millimeters a year off Perth and by 8.1 off the tropical Kimberley region over the past two decades.

VOA: standard.2009.11.09

"We believe that, with the experience of Thailand handling this situation in the past two decades, where at times there were several hundred thousand came over the Thai borders this is,on one hand,serious issue,"

VOA: standard.2009.06.09