【单选题】Mary is a secretary. She usually works _________ the Internet.
【单选题】Mary is a secretary. She often (answers calls) in the office.
【简答题】某种四肽α-COOHpK=2.4,α-N + H 3 pK=9.8,侧链-N + H 3 pK=10.6,侧链-COOHpK=4.2,试计算此种多肽的等电点(pI)是多少?
【简答题】在大气污染中我们可以根据 、 、爬升型、 、漫烟型五种烟羽形状了 解大气稳定状况。
【简答题】Mary wants to be a secretary. She is applying for a job as a secretary.