既能改变执行元件运动速度又能保证速度稳定的是()。 ["节流阀","溢流阀","三位四通换向阀","调速阀"]
低钾血症可表现为() ["心肌兴奋性增高","神经肌肉系统兴奋性降低","消化系统表现为厌食,腹胀","尿浓缩功能障碍","高血糖,正氮平衡"]
人造石的混水率通常为()。 ["0.15~0.25","0.25~0.35","0.35~0.45","0.5","0.65~0.75"]
饱和脂肪酸与冠心病的发病密切相关。胆固醇摄入量全天应()。 ["A.<1000mg","<800mg","=500mg",">300mg","<300mg"]
下列哪项是肥胖治疗最根本的措施()。 ["服用减肥药物","增加体力活动","吸脂手术","控制饮食","长期地控制能量摄入和增加能量消耗"]
铸造合金分为哪三个收缩阶段?