【单选题】出雏总数占入孵蛋总数的百分比是指以下哪项衡量孵化效果的指标?
【单选题】In recent years, there has been a ______ increase in the cost of living.
【判断题】压力容器质量检验是始终贯穿整个压力容器制造过程的。
【单选题】What is the most common type of road rage incidents?
【单选题】In the last paragraph, the author indicates that ______.
A.
nothing can be done about violence in sports
B.
violence in sports is worse now than in ever was
C.
football players are concerned about violence in sports
D.
athletes are confused about what should be permitted in sports
【单选题】一个非隔离式开关稳压电源,其技术指标如下:(1)输入电压50V,(2)输出电压20V~30V(输出电压极性反转),(3)输出纹波峰峰值不大于300mV,(4)输出电流最大2A,最小200mA,(5)电源开关频率100kHz。则此开关电源工作的最大占空比为:
【单选题】研究体育现象和揭示体育规律的知识体系为______。
【单选题】出雏总数占受精蛋总数的百分比是指以下哪项衡量孵化效果的指标?
【简答题】有一个电热水壶,铭牌如表所示.(不计热量的损失)求: 电热水壶 型号:91440 电压:220V 频率:50Hz 功率:1000W 最大水量:1kg (1)将质量为1kg、温度为20℃的一壶冷水,加热到100℃,水吸收的热量是多少?[水的比热容为4.2×10 3 J/(kg?℃)] (2)电热水壶正常工作多长时间才能把这壶水加热到100℃? (3)若在用电高峰期,实际电压只有200V,要把同样的这...