慢性支气管炎早期X线表现为() ["A．肺纹理改变","B．肺气肿征象","C．肺动脉高压征象","D．肺部炎症","E．气管剑鞘状改变"]
试述室性期前收缩的心电图特征?
动力型肺动脉高压和梗阻型肺动脉高压病理有何不同?
我国正常成年男性的血量约占体重() ["A．10％","B．9％","C．8％","D．7％","E．6％"]
先天性支气管囊肿的主要并发症为() ["A．继发感染","B．癌变","C．肺大泡","D．胸膜炎","E．支气管扩张"]
正常胎儿血液循环如图，简述正常胎儿血液循环途径?
