简述起重机有哪些保护电器?
参考答案:
过电流继电器、保护柜中主接触器、各机构行程限位器、紧急开关、超载限制器、熔断器。
阅读短文,判断下列句子是否与短文的内容相符,如相符,请在括号内写“T”,否则写“F”。
Betty and Kate are sisters. They're from the USA. They're in Beijing. Now they're looking at a map of
Beijing. They're going to visit the Great Wall first. And then they're going to visit the Summer Palace (颐和园)
and the Beijing Zoo. They're going to visit many places (地方) in Beijing. They say China is a great country and
the Chinese people are friendly.
( ) 1. Betty and Kate are in the USA now.
( ) 2. They're in China now.
( ) 3. They have a map of Beijing.
( ) 4. They are visiting the Great Wall.
( ) 5. They are going to visit many places in China.
( ) 6. They like China.
梁启超在《中国历史研究法》中写道:“夫成绩者,今所现之果也,然必有昔之成绩以为因;而今之成绩又自为因,以孕产将来之果;因果相续,如环无端,必寻出因果关系,然后活动之继续性可得而悬解也。”下列没有因果关系的历史现象是
A.铁器和牛耕——井田制瓦解
B.明清资本主义萌芽——近代民族工业产生
C.工业革命——鸦片战争
D.民族工业短暂发展——无产阶级队伍壮大