基因工程中科学家常用细菌.酵母菌等微生物作为受体细胞,原因是() ["结构简单、操作方便","繁殖速度快","遗传物质含量少、简单","性状稳定、变异少"]
区别尿血与血淋的关键是() ["尿色的深浅","尿中有无红细胞","尿时痛与不痛","是否伴有全身症状","是否伴有水肿"]
在肺源性心脏病中,提示重度肺动脉高压的X线征象是() ["右心室重度增大","右心功能不全","肺动脉圆锥隆起","肺动脉干增粗","肺门"残根"征"]
在遗传工程技术中,限制性内切酶主要用于() ["目的基因的提取和导入","目的基因的提取和检测","目的基因与运载体的结合和导入","目的基因的提取和与运载体结合"]
治疗脾胃虚寒所致的便血,宜选用() ["补中益气汤","黄芪建中汤","黄土汤","理中汤","十全大补汤"]
省煤器管泄漏,严重时爆破的原因?