母线及隔离开关长期允许的工作温度通常不应超过() ["A.50℃","B.60℃","C.70℃","D.80℃"]
大电流接地系统是指中性点直接接地的系统,其接地电阻值应不大于() ["0.4Ω","0.5Ω","1Ω","4Ω"]
治疗呕吐外邪犯胃证的主方是() ["保和丸加减","四七汤加减","藿香正气散加减","麦门冬汤加减","理中汤加减"]
电缆穿越农田时,敷设在农田中的电缆埋设深度不应小于()m。 ["0.5","1","1.5","2"]
下列选项中,不属胃阴不足型呕吐主症的是() ["呕吐反复,时作干呕","似饥而不欲食","嗳气吞酸","口干咽燥","舌红少津脉细"]
液压传动的优点和缺点是什么?