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  • 水分临界期是农作物各不同生育期中对水分缺乏_____的时期。
  • 下列各项中,属于生物产量的是
  • 工作在放大区的某三极管,当ib从10微安增加到40微安,ic从1mA增加到4mA,则β为( )。
  • 为了使高阻输出的放大电路与低阻负载很好地配合,可以在放大电路与负载之间插入。( )
  • 利用适当电容把起反馈作用的电路隔开,是为了保证反馈
  • We'd better not eat meat only and know that milk and fruit _____ good for our health.
  • To lose weight, you should not only eat less, _____ do more exercise.
  • Tom stays at home today. I see him _____ his car in the garden.
  • _____ is a good habit to go to bed early and get up early every day.
  • Stephenson has become the _____ railway engineer in the world.
  • Nowadays, it's convenient and cheap for us _____ a shared-bicycle.
  • Chinese _____ to return home to be with their families in the Spring Festival.
  • — Is Mrs. Green in? — I'm afraid se isn't. Would you like to _____ a message?
  • 在铸锻件毛坯表面上进行划线时,可使用( )涂色;在表面已加工过的工件是划线时,可使用( )涂色。①品紫②硫酸铜溶液③白灰水正确答案是( )
  • 关于N型半导体的下列说法,错误的是( )。
  • 将PN结P区接电源负极,N区接电源正极,此时PN结处于( )偏置。
  • 一对中等精度等级,正常啮合的齿轮,它的接触斑点在轮齿高度上应不少于( )。
  • 车削时,主轴转速升高后,( )也随之增加。①切削速度②进给速度③进给量④切削深度正确答案是( )
  • 划线时,应尽量使( )与设计基准一致。
  • 轴类零件以V形块定位时,其定位基准面是( )。