如图所示,在x轴上方存在着垂直于纸面向里、磁感应强度为B的匀强磁场,一个不计重力

题型:选择题

问题:

如图所示,在x轴上方存在着垂直于纸面向里、磁感应强度为B的匀强磁场,一个不计重力的带电粒子从坐标原点O处以速度v进入磁场,粒子进人磁场时的速度方向垂直于磁场且与x轴正方向成120°角,若粒子穿过y轴正半轴后在磁场中到x轴的最大距离为a,则该粒子的比荷和所带电荷的正负是(  )

A.,正电荷

B.,正电荷

C.,负电荷

D.,负电荷

考点:带电粒子在匀强磁场中的运动
题型:选择题

当建设项目有多个单项工程时,应采用()预算编制形式。

A.一级

B.三级

C.二级

D.四级

题型:选择题

There are two websites I think you should know about. Do you find it difficult to say a word correctly? Do you want to hear the correct pronunciation(发音)? If so, what you’ve been looking for is cooldictionary.com. This site is designed to pronounce words and phrases in precise(严谨的) manner. All you have to do is to go to the Pronunciation Help and type in a word. You can also practice your spoken English and improve your communication skill.

Another useful site is www.nutsandboltsguide.com. It has been specifically designed to help you with every step of writing. This site is a must-visit for all those who want to become a writer. It not only talks about different kinds of writing but also discusses a lot about grammar. I’m sure that this site will help you with your writing skills and different writing styles with its sound tips. So get connected and log in to play. Happy surfing!

小题1:We can know from passage that the cooldictionary.com is _______.

A.a website on the Internet

B.an electronic dictionary that can pronounce words

C.a website teaches you how to write

D.a part of the Pronunciation Help小题2:What is not offered on the website www.nutsandboltsguide.com?

A.Sound tips on how to write

B.Guide to different stages(步骤) of writing

C.Advice on grammar learning.

D.The pronunciation of each word in your article.小题3:This passage is probably from ________.

A.a magazine about computer

B.a novel

C.a newspaper

D.a comic book

题型:选择题

对于原发性肝癌的转移,下列哪项提法不正确()

A.肝内血行转移发生最早,也最常见

B.容易侵犯门静脉分支形成癌栓

C.肝外血行转移中,转移至肺的几达半数

D.经淋巴转移至肝门淋巴结的最多

E.种植转移常见

题型:选择题

装置冷循环进油时,要关闭各低点放空,防止跑油,尽量将设备内存水退至退油罐。

题型:选择题

在距离接触网带电部分()m的导线、支柱、房顶及其他建筑物上施工时,接触网可不停电,但须有接触网工或经专门训练的人员在场监护。

A、1~2

B、2~4

C、3~4

D、4~5

更多题库