慕课标签存档订阅

第6章单元测验——尺寸标注

1、单选题：
​线性尺寸的尺寸数字通常写在尺寸线的：‎
选项：
A: 下方 
B: 上方
C: 左边
D: 中断处
答案: 【 上方】点我阅读全文

第二周单元测试

1、单选题：
‌摄像机镜头焦距的单位是（  ）。‏‌‏
选项：
A: 毫米
B: 厘米
C: 分米
D: 微米
答案: 【 毫米】点我阅读全文

法人一节测试

1、单选题：
‍代表法人的自然人称为（      ）。​
选项：
A: 法人代表
B: 法定代表人
C: 法人
D: 代理人
答案: 【 法定代表人】点我阅读全文

第二章单元测试

1、单选题：
 计算机网络系统的基本组成是（   ）。‎
选项：
A: 局域网和广域网
B: 本地计算机网络和通信网
C: 通信子网和资源子网
D: 服务站和工作站
答案: 【 通信子网和资源子网】点我阅读全文

第一讲 单元测验

1、单选题：
‍陀思妥耶夫斯基作为世界一流艺术家的地位由_____________确立。‍
选项：
A: 《罪与罚》
B: 《白痴》
C: 《卡拉马佐夫兄弟》
D: 《被侮辱与被损害的》
答案: 【 《罪与罚》】点我阅读全文

第11章 测验

1、单选题：
1920年代末巴金发表了第一部小说_________。
选项：
A: 《新生》
B: 《家》.
C: 《灭亡》
D: 《萌芽》
答案: 【 《灭亡》】点我阅读全文

PN结的形成

1、单选题：
‌自建电场会‍
选项：
A: 阻止漂移
B: 阻止扩散
C: 增强扩散
D: 同时增强扩散和漂移
答案: 【 阻止扩散】点我阅读全文

ZGSOS[2]第二章进程管理单元测试A

1、单选题：
‏程序在独占处理器的情况下运行时：只要程序执行时的环境和初始条件相同，程序重复执行的结果相同，这称之为（      ）。​
选项：
A: 顺序性
B: 封闭性
C: 可再现性
D: 开放性
答案: 【 可再现性】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

三重积分的概念和性质测试

1、单选题：

‍

​选项：
A:
B:
C:
D:
答案: 【 】点我阅读全文