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问题 选择题

下图为卢瑟福和他的同事们做α粒子散射实验的装置示意图,荧光屏和显微镜一起分别放在图中的A､B､C､D四个位置时,关于观察到的现象,下列说法中正确的是(    )

A．相同时间内放在A位置时观察到屏上的闪光次数最多

B．相同时间内放在B位置时观察到屏上的闪光次数只比放在A位置时稍少些

C．放在C､D位置时屏上观察不到闪光

D．放在D位置时屏上仍能观察到一些闪光,但次数极少

答案

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卢瑟福和他的同事们做α粒子散射实验时,得到以下结论:大部分α粒子都能直接穿过金箔,个别的发生偏转,极少数发生大角度的偏转,故A､D正确,B､C错误.

单项选择题

Who won the World Cup 1994 football game What happened at the United Nations How did the critics like the new play (1) an event takes place, newspapers are on the streets (2) the details. Wherever anything happens in the world, reporters are on the spot to (3) the news.
Newspapers have one basic (4) , to get the news as quickly as possible from its source, from those who make it to those who want to (5) it.
Radio, telegraph, television, and (6) inventions brought competition for newspaper. So did the development of magazines and other means of communication. (7) , this competition merely spurred the newspapers on. They quickly made use of the newer and faster means of communication to improve the (8) and thus the efficiency of their own operations. Today more newspapers are (9) and read than ever before. Competition also led newspapers to branch out into many other fields. Besides keeping readers (10) of the latest news, today’s newspapers (11) and influence readers about politics and other important and serious matters. Newspapers influence readers’ economic choices (12) advertising. Most newspapers depend on advertising for very (13) .
Newspapers are sold at a price that (14) even a small fraction of the cost of production. The main (15) of income for most newspapers is commercial advertising. The (16) in selling advertising depends on a newspaper’s value to advertisers. This (17) in terms of circulation. How many people read the newspaper
Circulation depends (18) on the work of the circulation department and on the services or entertainment (19) in a newspaper’s pages. But for the most part, circulation depends on a newspaper’s value to readers as a source of information (20) the community, city, county, state, nation, and world—and even outer space.

[A] however [B] And [C] Therefore[D] Furthermore
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多项选择题

电源技术中，安规是安全规范和安全标准的简称，对于安规设计以下说法正确的是（）

A.安规设计的目的是降低电气产品对人身和财产的各种伤害。

B.安规是电源操作维护人员需要遵守的工作规范。

C.安规是电源生产厂家在电源设计时需满足的标准。

D.为保证可信度，安规的认证采用第三方认证的方式。
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