【判断题】装配图中,并不是所有种类零件、部件都要编写序号,该说法是否正确
【单选题】在两级放大电路中,已知各自单级20lg|AVM1| = 40dB,fL1 = 4Hz,fH1 = 20kHz;20lg|AVM2| = 30dB,fL2 = 400Hz,fH2 = 150kHz。则两级放大电路的电压增益为 ,上限截止频率约为 ,下限截止频率约为 。
【单选题】在两级放大电路中,已知各自单级20lg|AVM1| = 40dB,fL1 = 4Hz,fH1 = 20kHz;20lg|AVM2| = 30dB,fL2 = 400Hz,fH2 = 150kHz。则两级放大电路的电压增益为 ,上限截止频率约为 ,下限截止频率约为 。
【判断题】雷电放电发生在两块雷云之间或雷云与大地之间,不存在金属电极,因而与阴极上的r过程和二次电子发射无关。
【单选题】下述哪个选项不是高分子对溶胶聚沉作用的机理?( )
【单选题】建构拉伸特征时出现失败的原因主要有( )
【多选题】如图所示,通过水平绝缘传送带输送完全相同的铜线圈,线圈等距离排列,且与传送带以相同的速度匀速运动.为了检测出个别未闭合的不合格线圈,让传送带通过一固定匀强磁场区域,磁场方向垂直于传送带运动方向,根据穿过磁场后线圈间的距离,就能够检测出不合格线圈.通过观察图形,判断下列说法正确的是【图片】
A.
若线圈闭合,进入磁场时,线圈中感应电流方向从上向下看为逆时针。
B.
若线圈闭合,传送带以较大速度匀速运动时,磁场对线圈的作用力增大。
【判断题】Modems can be classified external ones and internal ones.
【单选题】In which of the following exchanges is there a grammatic mistake?
A.
---Have they removed their furniture? ---They have done the desks, but that's all so far.
B.
---Does granny look after you every day? ---She can't do at weekends, because she has to go to her own house.
C.
---Can lions climb trees? ---No, but leopards can.
D.
---Did the lions seem hungry? ---No, but they did restless.