站长

139204

站长 的帖子

1 创新创业与财商素养概论

创新创业与财商素养概论单元测试

1、单选题：
（      ）是一个发现和捕获机会并由此创造出新颖的产品、服务或实现其潜在价值的过程。​
选项：
A: 创新
B: 创业
C: 创造
D:  创作
答案: 【 创业】点我阅读全文

本文共有 186 人阅读

Lesson2

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 96 人阅读

第1周导论初识国际结算

何谓国际结算？

1、单选题：
‍国际结算制度的核心是（    ）。​
选项：
A: 信用制度
B: 贸易制度
C: 银行制度  
D: 外汇管理制度
答案: 【 信用制度】点我阅读全文

本文共有 92 人阅读

第2章选频网络-2

随堂测验

1、判断题：
‎线性元件具有频率变换作用‎
选项：
A: 正确
B: 错误
答案: 【 错误】点我阅读全文

本文共有 99 人阅读

第一周教学内容

1.1解剖学绪论

1、单选题：
‍关于解剖学姿势的描述，错误的是‍
选项：
A: 人体直立
B: 两眼向前方平视
C: 上肢下垂，掌心紧贴躯体
D: 双足并立，足尖朝前
答案: 【 上肢下垂，掌心紧贴躯体】点我阅读全文

本文共有 103 人阅读

Week 1-2

Lecture 1 你会“搭讪”吗？

1、单选题：
In the following four items, which is NOT a favorable way to start a small talk with a stranger?
选项：
A: Ask people where they grow up in
B: Commenting on the weather
C: Ask people why they are not married
D: Chatting about what you are both doing
答案: 【 Ask people why they are not married】点我阅读全文

本文共有 91 人阅读

第1章电力电子变换和控制技术导论

第一章单元测验

1、单选题：
‍固定通态时间Ton，改变开关频率或周期Ts，从而改变导通比D实现输出电压控制的方法，被称为   ‍‍‌‍
选项：
A: 脉冲宽度调制PWM
B: 脉冲频率调制PFM
C: 脉冲幅度调制PAM
D: 脉冲编码调制PCM
答案: 【 脉冲频率调制PFM】点我阅读全文

本文共有 106 人阅读

第一章消费者行为研究方法一

第一周小测试

1、单选题：
​1. 面对面访谈又分为一对一的深度访谈和（      ）​
选项：
A: 民族志研究
B: 线上采访
C: 一对多的焦点团体
D: 电话访谈
答案: 【 一对多的焦点团体】点我阅读全文

本文共有 130 人阅读

第一讲微观经济学导论稀缺性与微观经济学

1.10微观经济学要研究什么

1、单选题：
‏以下哪个问题不是微观经济学的研究内容‍
选项：
A: 厂商生产商品的产量和价格
B: 失业率的上升和下降
C: 政府宏观经济研究部门的雇佣情况
D: 税收对某一商品价格的影响
答案: 【 失业率的上升和下降】点我阅读全文

本文共有 105 人阅读