题干

回旋加速器是加速带电粒子的装置,其核心部分是分别与高频交流电极相连接的两个D形金属盒,两盒间的狭缝中形成的周期性变化的电场,使粒子在通过狭缝时都能得到加速,两D形金属盒处于垂直于盒底的匀强磁场中,如图4所示,要增大带电粒子射出时的动能,则下列说法中正确的是(   )

A:增大磁场的磁感应强度

B:增大匀强电场间的加速电压

C:减小狭缝间的距离

D:减小D形金属盒的半径

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答案(点此获取答案解析)

A

同类题1

阅读下面的文字,完成下列各题。

用知识产权撬动知识创新

滕朝阳

    ①回溯人类文明史,专利制度促进了创新知识迅速公共化,同时也为技术和市场的结合提供了制度保证。从专利制度诞生早于工业革命发生的时序来看,二者之间应该存在极其重要的因果关联。时至今日,包括专利权在内的知识产权在世界范围内普遍受到法律保护。为树立尊重知识、崇尚科学和保护知识产权的意识,营造鼓励知识创新和保护知识产权的法律环境,世界知识产权组织将每年的4月26日定为“世界知识产权日”。

    ②与西方国家相比,我国的知识产权保护工作起步较晚。知识产权进入人们的观念,被确立为一种制度在经济社会生活中发挥作用,不过是近三十年来的事。我国已经建立了门类比较齐全的知识产权法律体系,取得的知识产权成果也令世界刮目相看。但侵犯知识产权的行为还不少,“山寨产品”还受到不少消费者认可,尊重知识、尊重创造还没有深入人心,保护知识产权就是保护民族创新能力还没有形成广泛共识和自觉行动。

    ③知识创新是充满高风险、需要高投入、具有高难度的智力活动。很多人能熟练应用旧知识,只有极少数人能在知识存量的基础上发展出新知识,而知识创新的成果恰恰是人类福利增进和社会进步的源泉。只有尊重、保护创造性智力成果,才能激发人们的创新热情,并为持续创新奠定基础。相反,如果人人都可以搭便车,从事知识创新的人就无法得到足够的补偿与激励,持续创新就会丧失动力。

    ④漠视知识产权,就将被假冒伪劣包围,在这样的环境中生活,很难有获得感和幸福感。但人们对知识产权的重视,还没有达到应有的广度和深度。事实上,即使是权利人,对知识产权的保护也往往不够重视。作家莫言在一篇文章中,提到几年前一群作家跟一家网站打版权官司:“按说这是一件正大光明的事情,但是很多人说风凉话:有这么多的国家大事,你们不去关心;有这么多的弱势群体,你们不去关怀;你们这帮作家﹣﹣人类灵魂的工程师,就关心自己的版税,还诉诸公堂,占用媒体宝贵的版面和时间。”这是一种非常典型的情境,从一个侧面反映了对知识产权的态度。

    ⑤我们在保护知识产权方面取得了明显进步,但还很不如人意。有的企业负责人坦言“已经不愿意申请专利了”,因为“不申请专利还好,一申请专利反而被剽窃得更快”,于是“核心技术方面绝不再向外透露”。在专利制度建立之前,技术进步都是由技术机密所驱动,而这种传承方式会极大地阻碍了人们之间的知识共享。知识创新成果的产权保护不力,就会回到“机密保护”的状态,这既会抑制自己的创新,也不利于引进最好的技术。

    ⑥在互联网时代,知识产权保护面临更复杂的环境,相关法律制度还有待于进一步完善。在根本上,还是要确立这样一种理念:侵犯知识产权不仅可耻,而且违法!只有保护好创造性智力成果,投身知识创新的人才会越来越多,创新驱动才会变成广阔的现实,社会才能获得不竭的前进动力。

(2016年第8期《半月谈》,有删节)

同类题5

阅读理解。

    Selena Gomez and I are scheduled to meet at a low­key coffee shop in Encino. Not wanting to keep the superstar waiting, I arrived at nine, 20 minutes early. As I was catching up on e­mails, Selena quietly scooted into the seat next to me. No bodyguard. Not even a drop of makeup. She was ten minutes early and no one else in the restaurant looked up so much. Selena was wearing Bebe shorts. She had a baby face and ordered a hot chocolate.

    After making small talk about what she wore for the shoot, she dived into the subject of her career. Selena declared 2012 the year of movies. She filmed three: Spring Breakers, a drama; The Getaway, an action flick; and Hotel Transylvania, a comedy. Each is a marked move away from the teen style that made her a household name.

    Now that her Disney days are behind her, Selena is at that unstable point in a child star's career where she is trying to grow up—both as a person(she turned 20 in July)and as an artist. “Being part of the Disney Channel was such a blessing, and I'm super happy with what my show accomplished, but acting is something I would like to take on more seriously.” She continued, “I don't necessarily feel accomplished. I want to create a whole different person when it comes to acting.”

    Selena has been working fulltime since she was seven years old and scored a role on Barney&Friends. In 2007, when she was offered the lead in Wizards of Waverly Place, Selena, her mother, and her stepfather uprooted from Texas to LA , where they are settling now.