慕课标签存档

第一章计划职能

单元测验

1、单选题：
SO策略是指：‏A.利用优势，把握机会   B.利用优势，克服威胁‏C.减少劣势，把握机会   D.减少劣势，克服威胁‏‎‏
选项：
A: A
B: B
C: C
D: D
答案: 【 A】点我阅读全文

本文共有 113 人阅读

Lesson 2

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

本文共有 94 人阅读

第一讲半导体导论

01-02杂质半导体

1、单选题：
‏N型半导体中的多子是（）。‍
选项：
A: 电子
B:  空穴
C: 正离子
D:  负离子
答案: 【 电子】点我阅读全文

本文共有 105 人阅读

第1周 绪论

1.1 魔鬼还是天使-王者农药随堂测验

1、单选题：
‏杀虫剂、杀菌剂、除草剂是按照农药的        来分类的。‎
选项：
A: 作用对象
B: 原料来源
C: 作用机理
D: 组成成分
答案: 【 作用对象】点我阅读全文

本文共有 112 人阅读

第2周计算

小测验

1、填空题：
写出以下代码执行后，t1和t2的值，以空格隔开：‏int a=14;‏int t1 = a++;‏int t2 = ++a;‏
答案: 【 14 16】点我阅读全文

本文共有 115 人阅读

第一章绪论

随堂测试

1、单选题：
‏机械工程自动控制系统的基本要求是稳定性、准确性和（  ）​
选项：
A: 美观性 
B: 实用性
C: 快速性 
D: 以上都不对
答案: 【 快速性 】点我阅读全文

本文共有 103 人阅读

第十章碱金属和碱土金属元素

第九章、第十章单元测试

1、单选题：
 在下列各种酸中酸性最强的是______。‌​‌
选项：
A: H2SO4  
B: H3PO4  
C: HClO4    
D: H3AsO4
答案: 【 HClO4    】点我阅读全文

本文共有 115 人阅读

第一周绪论

第一周单元测试

1、单选题：
‎医用瓶塞属于哪一种医用橡胶制品？‏
选项：
A: 不直接接触生物组织
B: 接触皮肤和粘膜
C: 暂时接触生物组织
D: 长期植入人体内
答案: 【 不直接接触生物组织】点我阅读全文

本文共有 107 人阅读

第二章 财务管理价值观念

第二章单元测验

1、单选题：
‍将100元钱存入银行，利息率为10%，计算5年后的终值应用 （   ）来计算。‏
选项：
A: 复利终值系数
B: 复利现值系数
C: 年金终值系数
D: 年金现值系数
答案: 【 复利终值系数】点我阅读全文

本文共有 138 人阅读

第二单元RFID标准化

标准化组织

1、多选题：
‍物联网标准化组织主要包括（     ）。​
选项：
A: UID泛在识别中心标准体系
B: EPCglobal标准体系
C: ISO/IEC标准体系
D: IEEE 标准体系
答案: 【 UID泛在识别中心标准体系;
EPCglobal标准体系;
ISO/IEC标准体系;
IEEE 标准体系】点我阅读全文

本文共有 113 人阅读