单选题安静时，正常机体能量代谢最为稳定的环境温度为

单选题A．尿比重明显增加B．尿量明显减少C．两者都有D．两者都无 (1996年)

单选题AIDS患者晚期外周血细胞减少最显著的是

单选题哪种是恶性肿瘤

单选题女性，73岁。下楼梯，时不慎摔倒，股骨骨折。行手术内固定术时，突然呼吸困难，发绀，血压下降，全身抽搐，昏迷，抢救无效死亡。尸体解剖，肺血管内最可能的发现是

单选题必要时，能转变为巨噬细胞的神经胶质细胞是

单选题A．活体心血管内血液某些成分形成固体质块B．组织内过多的体液潴留C．大量气体迅速进入血液D．局部组织血流阻断E．下肢静脉血栓脱落

单选题心室肌细胞动作电位平台期是下列哪些离子跨膜流动的综合结果( )(1996年，1997年)

单选题细胞内外正常的Na + 和K + 浓度差的形成和维持是由于

单选题A．四环素B．氯霉素C．链霉素D．嘌呤霉素

单选题In the two decades between 1910 and 1930, over ten percent of the Black population of the United States left the South, where the majority of the Black population had been located, and migrated to northern states, with the largest number moving, it is claimed, between 1916 and 1918. It has been frequently assumed, but not proved, that most of the migrants in what has come to be called the Great Migration came from rural areas and were motivated by two concurrent factors: the collapse of cotton industry following boll weevil infestation, which began in 1898, and increased demand in the North for labor following the cessation of European immigration caused by the outbreak of the First World War in 1914. This assumption has led to the conclusion that the migrants' subsequent lack of economic mobility in the North is tied to rural background, a background that implies unfamiliarity with urban living and a lack of industrial skills. But the question of who actually left the South has never been investigated in detail. Although numerous investigations document a flight from rural southern areas to southern cities prior to the Great Migration, no one has considered whether the same migrants then moved on to northern cities. In 1910 over 600,000 Black workers, or ten percent of the Black work force reported themselves to be engaged in "manufacturing and mechanical pursuits", the federal census category roughly including the entire industrial sector. The Great Migration could easily have been made up entirely of this group and their families. It is perhaps surprising to argue that an employed population could be tempted to move, but an explanation lies in the labor conditions then prevalent in the South. About thirty-five percent of the urban Black population in the South was engaged in skilled trades. Some were from the old artisan class of slavery--blacksmiths, masons, carpenters--which had a monopoly of certain trades, but they were gradually being pushed out by competition, mechanization, and obsolescence. The remaining sixty-five percent, more recently urbanized, worked in newly developed industries--tobacco, lumber, coal and iron manufacture, and railroads. Wages in the South, however, were low, and Black workers were aware, through labor recruiters and the Black press, that they could earn more even as unskilled workers in the North than they could as artisans in the South. After the boll weevil infestation, urban Black workers faced competition from the continuing influx of both Black and White rural workers, who were driven to undercut the wages formerly paid for industrial jobs. Thus, a move north would be seen as advantageous to a group that was already urbanized and steadily employed, and the easy conclusion tying their subsequent economic problems in the North to their rural backgrounds comes into question.

单选题大叶性肺炎的肉质变是由于

单选题有关亚急性感染性心内膜炎的描述，哪项是错误的

单选题分泌突然增加而诱发排卵的激素是

单选题红细胞沉降率加速主要是由于( )(2002年)

单选题急性肝淤血的病理变化有

单选题大肠杆菌DNA指导的RNA聚合酶由数个亚单位组成，其核心酶的组成是

单选题A.心房B.窦房结C.浦肯野纤维D.心室肌E.房室交界区

单选题类风湿关节炎最常累及的关节是

单选题下列不符合心脏淀粉样物质沉积的病变特点是