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下列关于催化剂的说法不正确的是（　　） A．化学反应前后，催化剂的质量和化学性质都不变 B．催化剂可以提高某些化学反应的速率 C．催化剂可以降低某些化学反应的速率 D．任何化学反应都需要催化剂
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【多选题】关于静电场的高斯定理，下列说法正确的是【图片】
A.
说明静电场是有源场
B.
高斯面上的场强由高斯面内的电荷决定
C.
高斯面上的场强由高斯面内和面外的电荷决定
D.
闭合曲面的电通量由高斯面内的电荷决定
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【简答题】选择方框内的词的适当形式填空，每词只能用一次。 go do help study look have sell be like find 1. I can _____ my watch. 2. They _____ me very much. 3. Mike _____ hard in class. 4. The workers in the shop _____ very friendly. 5...
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【单选题】在静电场中,关于场的对称性、高斯定理、静电力,下列说法正确的是 [ ]
A.
若静电场的分布不具有对称性，则高斯定理不成立
B.
点电荷在电场力作用下，一定沿电场线运动
C.
两个点电荷之间的作用力大小为 F ，当第三个点电荷移近时，两个点电荷之间的作用力大小仍为 F
D.
有限长均匀带电直线的场具有轴对称性，因此可以用高斯定理求出空间各点的场强
查看完整题目与答案
【多选题】关于静电场环路定理，下列哪些说法是正确的
A.
静电场场强沿任意闭合环路的线积分总等于0；
B.
静电场场强沿闭合路径的线积分不一定都等于0，还与场强分布及闭合路径的大小形状有关。
C.
静电场环路定理和静电场高斯定理，是两个彼此独立的定理。
D.
根据静电场环路定理，静电场场强对闭合面的面积分取决于该面所包围的电荷电量。
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【判断题】“狐假虎威”中的“假”读作“jià ”,可以组词:假期。( )
A.
正确
B.
错误
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【单选题】听力原文：M: You look happy. Did you sell lots of things at the store today? W: No. I bought something. It was a great deal. M: So what is it? W: A laptop computer. M: Really? That's great. It's really con...
A.
Sold lots of things.
B.
Sold a computer.
C.
Bought a computer.
D.
Bought new clothes.
查看完整题目与答案
【单选题】听力原文：M: You look happy. Did you sell lots of things at the store today? W: No. I bought something. It was a great deal. M: So what is it? W: A laptop computer. M: Really? That's great. They are really...
A.
She is a software engineer.
B.
She is an after-sale service worker.
C.
She works as a salesclerk.
D.
She is hunting for a job.
查看完整题目与答案
【简答题】Text ysis The text is about the influence of e-commerce. The main idea is that online trade has revolutionized the way we sell or buy things as well as brought us some new problems. The text can b...
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【单选题】稳压管的稳定电压 V Z 是指其 。
A.
反向偏置电压
B.
正向导通电压
C.
死区电压
D.
反向击穿电压
查看完整题目与答案
【简答题】Complete the sentences with the proper forms of the given words. 1. Some top students _____(send) to study in foreign countries once a year. 2.More and more schools ___________(build) here later. 3. W...
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相关题目：
【多选题】关于静电场的高斯定理，下列说法正确的是【图片】
A.
说明静电场是有源场
B.
高斯面上的场强由高斯面内的电荷决定
C.
高斯面上的场强由高斯面内和面外的电荷决定
D.
闭合曲面的电通量由高斯面内的电荷决定
查看完整题目与答案
【简答题】选择方框内的词的适当形式填空，每词只能用一次。 go do help study look have sell be like find 1. I can _____ my watch. 2. They _____ me very much. 3. Mike _____ hard in class. 4. The workers in the shop _____ very friendly. 5...
查看完整题目与答案
【单选题】在静电场中,关于场的对称性、高斯定理、静电力,下列说法正确的是 [ ]
A.
若静电场的分布不具有对称性，则高斯定理不成立
B.
点电荷在电场力作用下，一定沿电场线运动
C.
两个点电荷之间的作用力大小为 F ，当第三个点电荷移近时，两个点电荷之间的作用力大小仍为 F
D.
有限长均匀带电直线的场具有轴对称性，因此可以用高斯定理求出空间各点的场强
查看完整题目与答案
【多选题】关于静电场环路定理，下列哪些说法是正确的
A.
静电场场强沿任意闭合环路的线积分总等于0；
B.
静电场场强沿闭合路径的线积分不一定都等于0，还与场强分布及闭合路径的大小形状有关。
C.
静电场环路定理和静电场高斯定理，是两个彼此独立的定理。
D.
根据静电场环路定理，静电场场强对闭合面的面积分取决于该面所包围的电荷电量。
查看完整题目与答案
【判断题】“狐假虎威”中的“假”读作“jià ”,可以组词:假期。( )
A.
正确
B.
错误
查看完整题目与答案
【单选题】听力原文：M: You look happy. Did you sell lots of things at the store today? W: No. I bought something. It was a great deal. M: So what is it? W: A laptop computer. M: Really? That's great. It's really con...
A.
Sold lots of things.
B.
Sold a computer.
C.
Bought a computer.
D.
Bought new clothes.
查看完整题目与答案
【单选题】听力原文：M: You look happy. Did you sell lots of things at the store today? W: No. I bought something. It was a great deal. M: So what is it? W: A laptop computer. M: Really? That's great. They are really...
A.
She is a software engineer.
B.
She is an after-sale service worker.
C.
She works as a salesclerk.
D.
She is hunting for a job.
查看完整题目与答案
【简答题】Text ysis The text is about the influence of e-commerce. The main idea is that online trade has revolutionized the way we sell or buy things as well as brought us some new problems. The text can b...
查看完整题目与答案
【单选题】稳压管的稳定电压 V Z 是指其 。
A.
反向偏置电压
B.
正向导通电压
C.
死区电压
D.
反向击穿电压
查看完整题目与答案
【简答题】Complete the sentences with the proper forms of the given words. 1. Some top students _____(send) to study in foreign countries once a year. 2.More and more schools ___________(build) here later. 3. W...
查看完整题目与答案
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