二尖瓣轻度狭窄时瓣口面积减至() ["1.5cm2以下","2.0cm2以下","4.0cm2以下","4~6cm2","6~8cm2"]
下列描述不属于H2S物理性质的是()。 ["A、无色","B、密度比空气大","C、有臭鸡蛋味","D、能燃烧"]
具有抗肿瘤的药物是() ["A.天麻","B.羚羊角","C.钩藤","D.地龙","E.白蒺藜"]
直流电动机与同一容量的三相异步电动机相比,效率()。 ["一样","低2%~3%","高2%~3%","高3%~5%"]
含有天麻素的药物是() ["天麻","蜈蚣","僵蚕","钩藤","牛黄"]
影响珊瑚礁生长的因素有哪些?