mooc标签存档订阅

单元测试1

1、单选题：

‌计算

‍选项：
A:
B:
C:
D:
答案: 【 】点我阅读全文

Scanning

1、单选题：
‏Read the passage "The Discovery of X-rays" quickly and choose the paragraph(s) which contain(s) the answer(s). You may choose more than one answer for question 3. ‎‏‎The Discovery of X-rays‎‏ ‎Par. 1 Except for a brief description of the Compton effect, and a few other remarks, we have postponed the discussion of X-rays until the present chapter because it is particularly convenient to treat X-ray spectra after treating optical spectra. Although this ordering may have given the reader a distorted impression of the historical importance of X-rays, this impression will be corrected shortly as we describe the crucial role played by X-rays in the development of modern physics.‎Par. 2 X-rays were discovered in 1895 by Roentgen while studying the phenomena of gaseous discharge. Using a cathode ray tube with a high voltage of several tens of kilovolts, he noticed that salts of barium would fluoresce when brought near the tube, although nothing visible was emitted by the tube. This effect persisted when the tube was wrapped with a layer of black cardboard. Roentgen soon established that the agency responsible for the fluorescence originated at the point at which the stream of energetic electrons struck the glass wall of the tube. Because of its unknown nature, he gave this agency the name X-rays. He found that X-rays could manifest themselves by darkening wrapped photographic plates, discharging charged electroscopes, as well as by causing fluorescence in a number of different substances. He also found that X-rays can penetrate considerable thicknesses of materials of low atomic number, whereas substances of high atomic number are relatively opaque. Roentgen took the first steps in identifying the nature of X-rays by using a system of slits to show that (1) they travel in straight lines, and that (2) they are uncharged, because they are not deflected by electric or magnetic fields.‎Par. 3 The discovery of X-rays aroused the interest of all physicists, and many joined in the investigation of their properties. In 1899 Haga and Wind performed a single slit diffraction experiment with X-rays which showed that (3) X-rays are a wave motion phenomenon, and, from the size of the diffraction pattern, their wavelength could be estimated to be 10-8 cm. In 1906 Barkla proved that (4) the waves are transverse by showing that they can be polarized by scattering from many materials.‎Par. 4 There is, of course, no longer anything unknown about the nature of X-rays. They are electromagnetic radiation of exactly the same nature as visible light, except that their wavelength is several orders of magnitude shorter. This conclusion follows from comparing properties 1 through 4 with the similar properties of visible light, but it was actually postulated by Thomson several years before all these properties were known. Thomson argued that X-rays are electromagnetic radiation because such radiation would be expected to be emitted from the point at which the electrons strike the wall of a cathode ray tube. At this point, the electrons suffer very violent accelerations in coming to a stop and, according to classical electromagnetic theory, all accelerated charged particles emit electromagnetic radiations. We shall see later that this explanation of the production of X-rays is at least partially correct.‎Par. 5 In common with other electromagnetic radiations, X-rays exhibit particle-like aspects as well as wave-like aspects. The reader will recall that the Compton effect, which is one of the most convincing demonstrations of the existence of quanta, was originally observed with electromagnetic radiation in the X-ray region of wavelengths.‎‏‎‏When were X-rays discovered?‎
选项：
A: Par. 1
B: Par. 2
C: Par. 3
D: Par. 4
E: Par. 5
答案: 【 Par. 2】点我阅读全文

1.1 随堂测验

1、单选题：
‍1.第一台电子数字计算机ENIAC（Electronic Numerical Intergrator and Calculator）是哪一年问世的？‌
选项：
A: 1940年
B: 1945年
C: 1946年
D: 1950年
答案: 【 1946年】点我阅读全文

1.1.1随堂测验

1、单选题：
‌本征半导体中，若掺入的是      价元素，则形成N型半导体。‏
选项：
A: 3
B: 4
C: 5
D: 6
答案: 【 5】点我阅读全文

第一章 单元测试

1、单选题：
建筑工程安全生产管理必须坚持（ ）第一、预防为主的方针，建立健全安全生产的责任制度和群防群治制度。‏
选项：
A: 安全
B: 质量
C: 成本
D: 进度
答案: 【 安全】点我阅读全文

第一周 测验题

1、单选题：
哥德巴赫是哪个国家的数学家？​​‍​
选项：
A:  德国
B:  英国  
C:   法国  
D:  美国
答案: 【  德国】点我阅读全文

第一章单元测验

1、单选题：
‌信息是普遍存在的是指信息的（    ）‏
选项：
A: 无限性
B: 普遍性
C: 动态性
D: 有序性
答案: 【 普遍性】点我阅读全文

第一单元测验

1、单选题：
‍《民法总则》的施行时间为‌
选项：
A: 2017年3月15日
B: 2017年8月1日
C: 2017年10月1日
D: 2017年12月1日
答案: 【 2017年10月1日】点我阅读全文

第三章配套习题

1、单选题：
‍1.在实际业务中，FOB条件下，卖方常接受买方委托代其租船订舱，费用由买方承担。如果船期比较紧张，到期卖方没能完成租船订舱，则（   ）。‎
选项：
A: 卖方不承担责任，风险由买方承担   
B: 卖方承担责任，风险由卖方承担    
C: 买卖双方共同承担责任和风险       
D: 双方均不承担责任和风险，合同终止
答案: 【 卖方不承担责任，风险由买方承担   】点我阅读全文

原电池

1、判断题：
自发进行的化学反应在原电池中进行时，将电能转化为化学能。​
选项：
A: 正确
B: 错误
答案: 【 错误】点我阅读全文