主动机构全部组装后,由于曲轴上两曲拐方向相差()汽缸勾贝的位置则相差半行程。 ["45°","90°","120°","180°"]
补体结合试验前受检血清需灭活,常用下列哪种方式。() ["37℃孵育30min","45℃孵育30min","56℃加热30min","60℃加热15min","室温下2h"]
对于未装晶体管设备的客车,测量其车体配线的绝缘电阻值,可采用()兆欧表。 ["100V","500V","l000V","2500V"]
五项竞技
热水器的安装高度一般是热水器的()与人眼平齐。 ["顶边","底边","观火孔","底部"]
确立图书馆目录体系的依据有哪些?