Specimen可与sample换用，但常指人或物中选出的有代表性部分，或指供科研、化验或检验用的标本。 主要内容如下:分 析介绍了几种常见抽油泵的工作原理、构造 、 适用范围及分类. Huge garbage dumps and sprawling landfills represent one of several extra awkward impacts that human beings have on wildlife. My very own investigate for the Stanford Heart on Adolescence employs in-depth interviews with m... https://www.diigo.com/profile/gurgaonhomesale