泵的抽气速率与气体的性质有关.Lashing velocity of pump is concerned with nature of air.现在已经采用了低温吸附技术和吸气离子泵的近代电子抽气设备.Recent electronic means of pumping using low temperature sorption techniques and getter - ion pumps have been introduce...
她成了一名专业的女中音歌手。She became a professional mezzo-soprano.女歌手分为女高音 、 女低音和女中音.Female singers are classified as sopranos, mezzo - sopranos and contraltos.她可是很优秀的 女中音 哦!She is an excellent mezzo - soprano ....