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宋朝医书中明确记载了通过银针遇砒霜是否变黑判断食物是否有毒的案例。砒霜是一种砷(As)的氧化物,传统方法生产的砒霜中含有少量硫化物。银虽然化学性质稳定,但容易与硫化物发生化学反应生成黑色的Ag2S,这就是通过银针变黑验毒的原理。
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同类题1

中国近代史是一部屈辱的历史,列强的侵略使中国一步步陷入半殖民地半封建社会的深渊。阅读下列材料,回答后面的问题。

材料一:中国是经历了深重苦难的国家,在工业革命发生前的几千年时间里,中国经济、科技、文化一直走在世界的第一方阵之中。近代以后,中国的封建统治者夜郎自大,闭关锁国,导致中国落后于时代发展步伐,鸦片战争则成为中国历史的一块界碑。

——***2014年4月1日在比利时布鲁日欧洲学院的演讲

材料二:在距“1894年中日事件”120年后的2014年4月21日,日本首相安倍晋三向靖国神社供奉祭品。靖国神社是日本军国主义对外侵略的精神支柱,其中供奉着近代以来历次战争中战死的日军亡灵,包括二战时对中国和周边国家犯下滔天罪行的战犯

——新华网

材料三:清政府赔偿白银4.5亿两,以海关等税收作担保;清政府保证严禁人民参加反帝活动;…划定北京东交民巷为使馆界,允许各国驻兵保护,不准中国人居住

——摘自北师大版教材八年级上册《历史》

材料四面对侵略,中国的近代化运动,走过了自强、变法、革命的历程……中国走向近代化的历史路程清晰在目,但留下的脚步并非一条直线。从器物层面到制度层面,再到观念层面,国人每向前迈进一步都异常艰难,但却是一个不断提高的过程。

同类题5

阅读理解

    Does the future of filmmaking lie in virtual reality (VR) films?

   An ambitious team led by Yale senior Celine Tien might hold the answer to that question.

    Tien produced,directed and acted in Pippa's Pan,which she says is “one of the world's first live-action VR films.”The film,which was completed in April,mixes live action with VR sections.Some of the characters were created via animation(动画)and other techniques that distinguish the film from 360° VR videos like the ones frequently seen on YouTube.

    “360° VR videos are stagnant,which means you don't move with them and see a 360° view of whatever they're filming.”Tien explained.“What we're doing is immersive(沉浸式的)VR.When you put on the goggles (a kind of special glasses) you can physic.ally walk around in the space,pick up objects and engage with the environment.It's a huge difference.”

    The immersive VR film experience is different for everyone who interacts with the medium,but that doesn't mean the film's ending will change for each viewer.

    The film stars two Chinese-speaking actors."It's a love story about a woman suffering from Alzheimer's disease who is trying to bring back memories of her husband,"Tien said.

    The film has already been recognized by the VR industry.After handing in a short demo to the AT&T Developer Summit Conference,Tien and her team were invited to Las Vegas in January,where they came in third place.

    If you're dying to see the film already,your choices area bit limited: Pippa's Pan can't be seen in movie theaters unless they happen to have VR goggles available.According to Tien,many theaters in China will soon have the ability,which makes sense considering China is the film's target market.

    Pippa's Pan will be released in three languages: Chinese,English and Korean.“It can get spread in different ways: at film festivals with VR set ups and through HTC or Oculus headset stores,”Tien says.“If you have VR goggles you can download it and experience it yourself.We will also cooperate with movie theaters that have VR set ups.”