【单选题】( )采用三相交流电源或单相交流电源,由三相异步电动机或单相异步电动机作为动力。
【单选题】速度继电器的文字符号为( ),位置开关的文字符号为( )。
【简答题】夹具的组成部分中, 装置的作用是使工件在加工过程中不改变占据的正确加工位置。
【单选题】饲料中钙、磷测定时试样干法分解所用的酸为( )。
【单选题】实验室的下列药品橱柜里,可见到一些常见的药品和试剂(如下表所列): 药品 橱柜 甲 乙 丙 丁 戊 常见 药品 木炭粉、硫磺、 红磷 铜片、锌粒、 镁带 NaOH溶液、 石灰水 H 2 SO 4 溶液(20%) 浓盐酸 NaHCO 3 、 CuSO 4 溶液 硝酸(HNO 3 )是化学实验室里的常用试剂,初中化学学习中不常见,若实验需要硝酸,应在实验室里的下列橱柜中寻找的是( )
【单选题】What happens when human beings are deprived of sleep for long periods of time? To answer this question, a New Yorker, Peter Tripp, offered to stay awake 200 hours. During that time Tripp was observed ...
A.
There is little danger of serious after-effects when human beings are deprived of sleep for long periods of time.
B.
Going without sleep for a long period will cause bad shortlivede ffects, but apparently no serious after-effects.
C.
After 200 hours without sleep Tripp was suffering from 'mental ill ness'.
D.
The doctors predicted Tripp would sleep for twenty or thirty hours.