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第一章测试

1、单选题：

‎如果矩阵满足AB=BA，则m,n,s,t应满足的条件为__________

‍选项：
A: n=t
B: m=s
C: m=n=s=t
D:
答案: 【 m=n=s=t】点我阅读全文

绪论单元测验

1、单选题：
‍昆虫占动物界种类的比例为多少？‏
选项：
A: 35%
B: 55%
C: 75%
D: 85%
答案: 【 75%】点我阅读全文

学习本课程的目的

1、多选题：
‏机械原理课程使学生掌握  ( ) 和 (  ) 的基本理论知识和基本技能，学会各种常用 (  )的分析和综合方法，并具有按照机械的使用要求进行机械传动系统方案设计的能力。‎‏‎
选项：
A: 机构学
B: 机器动力学
C: 机构
D: 机器
答案: 【 机构学;
机器动力学;
机构】点我阅读全文

判断题

1、判断题：
‏组织具有明确的目标导向、精心设计的结构与有意识协调的活动系统，同时又和外部环境保持密切的联系。‏
选项：
A: 正确
B: 错误
答案: 【 正确】点我阅读全文

单元测试单元一

1、单选题：
‍统计学是一门(    )‍
选项：
A: 自然科学
B: 新兴科学
C: 方法论科学
D: 实质性科学
答案: 【 方法论科学】点我阅读全文

第一章单元测验

1、单选题：
‍在下述四种表述中，使用了经济学家的货币定义的是‎‍‎
选项：
A: “上周你挣了多少钱？”
B: “我到商店里去时总是确信带足了钱。”
C: “爱财是万恶之源。”
D: “那位歌星确实很富，他的钱多得不得了。”
答案: 【 “我到商店里去时总是确信带足了钱。”】点我阅读全文

第一单元测试题

1、单选题：
​首次提出“经济地理学”这一科学名词的是‍
选项：
A: （德）戈策
B: （中）司马迁
C: （俄）罗蒙诺索夫
D: （古罗马）斯特拉波
答案: 【 （俄）罗蒙诺索夫】点我阅读全文

第1课时随堂测验

1、单选题：
‏在国际商法中，从事国际商事交易的主体不包括‎
选项：
A: 公司
B: 个人企业
C: 合伙
D: 国家
答案: 【 国家】点我阅读全文

阶段测试

1、单选题：
​若气相反应2A+B®P+S，则膨胀因子dA等于（）。​
选项：
A: 1/2
B: -1/2
C: 2
D: -2
答案: 【 -1/2】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