【单选题】电流频率不同,电击对人体的伤害程度也不同,通常( )对人体的危害性最大。
【简答题】频率低于______HZ的声音叫做次声波,频率高于______HZ的声音叫做超声波,若这两种声波在水中的传播速度分别为V 次 和V 超 ,则V 次 ______V 超 (填“大于”/“小于”或“等于”).
【单选题】世界上第一台冯.诺依曼结构的电子计算机,也是第一台真正意义上的现代计算机的是_______________。
【单选题】电流对人体的伤害作用中,( )电流危险性最大。
【单选题】电流频率不同,电击对人体的伤害程度也不同,通常( )对人体的危险性最大。
【单选题】世界上第一台冯.诺依曼结构的电子计算机,也是第一台真正意义上的现代计算机的是_______________。
【多选题】叶片泵的叶片数量增多后,双作用式叶片泵输出流量(),单作用式叶片泵输出流量()
【单选题】听力原文:W: Knowledge can change a person's fate. Don't you agree? M: Yes. I can't agree with you more. Q: What does the man think? (14)
A.
The man does not agree with the woman.
B.
He does not believe in fate.
C.
He thinks knowledge can change everything.
D.
He thinks knowledge can change people's fates.
【单选题】What is the man's attitude towards forecasting at the end of the conversation?
A.
He no longer believes short-range forecasts.
B.
He is so fascinated that he decides to study meteorology.
C.
He realizes that there is some value in long-range forecasting.
D.
He decides to change his forecast.
【简答题】10 工频交流电的危害性____直流电,一般认为40~100Hz的交流电对人最危险。电流对人体的伤害主要取决于____受损情况,因此,从手到手或从手到脚是很危险的电流路径。