题干

下图是1949〜2008年中国与外国建交情况曲线图,在下列各项中,建交最高峰出现的主要原因是(     )

A:在万隆会议上赢得了尊重

B:新中国恢复在联合国的合法席位

C:中美关系开始走向正常化

D:文化大革命扩大中国的政治影响

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答案(点此获取答案解析)

C

同类题2

实用类文本阅读。

获得诺贝尔奖的中国女人

    “呦呦鹿鸣,食野之苹。我有嘉宾,鼓瑟吹笙。”这句诗出自《诗经》,其中的“苹”指的是蒿类植物。这就是科学家屠呦呦的名字的由来。或许是巧合,在《诗经》产生近三千年后,这位叫“呦呦”的女科学家和她的研究团队,从青蒿中发现了专门治疗疟疾的药物“青蒿素”,这种药在全球特别是发展中国家挽救了数百万人的生命。

    作为一名生药学专业的学生,屠呦呦考入北大医学院时就和植物等天然药物的研发应用结下不解之缘,她1955年进入卫生部中医研究院(现为中国中医科学院)时,正值中医研究院初创期,条件艰苦,设备奇缺,实验室连基本的通风设施都没有,屠呦呦经常和各种化学溶液打交道,一度患上中毒性肝炎。除了在实验室内“摇瓶子”外,她还常常“一头汗两腿泥”地去野外采集样本,先后解决了中药半边莲及银柴胡的品种混乱问题,为防治血吸虫病作出了贡献。

    1967年5月23日,我国紧急启动“疟疾防治药物研究工作协作”项目,代号为“523”.屠呦呦被任命为“523”项目中医研究院科研组长。项目背后是残酷的现实:由于恶性疟原虫对氯喹为代表的老一代抗疟药产生抗药性,如何发明新药成为世界性的棘手问题。要在设施简陋和信息渠道不畅通的条件下,短时间内对几千种中草药进行筛选,其难度无异于大海捞针。但这些看似难以逾越的阻碍反而激发了她的斗志,通过翻阅历代本草医籍,四处走访老中医,甚至连群众来信都不放过,屠呦呦终于在2 000多种中草药中整理出一张含有640多种草药、包括青蒿在内的《抗疟单验访集》。可在最初的动物实验中,青蒿的效果并不出彩,屠呦呦的寻找也一度陷入僵局。

    到底是哪个环节出了问题呢?在查阅了大量文献后,屠呦呦在东晋葛洪的《肘后备急方》中发现了对青蒿治疗方法的描述:“青蒿一握,以水二升渍,绞取汁,尽服之。”为何古人将青蒿“绞取汁”,而不用传统的水煎熬煮中药之法呢?,屠呦呦意识到可能是煮沸和高温提取破坏了青蒿中的活性成分,于是她改变原来的提取方法。1971年,屠呦呦课题组终于在第19l次低沸点实验中发现,以低沸点溶剂乙醚来提取有效成分,明显提高了青蒿防治疟疾的效果,也大大降低了其毒性。这种编号为19l的青蒿萃取液,在治疗被P.berghei疟原虫感染的小鼠和被P.cynomolgi疟原虫感染的猴子时,有效率达到了100%。

    青蒿萃取液作用于人类身上是否安全有效呢?为了尽快确定这一点,屠呦呦和她的同事们勇敢地充当了首批志愿者——在自己身上进行实验。在当时没有关于药物安全性和临床效果评估程序的情况下,这是他们获得信心的唯一办法。在自己身上实验获得成功之后,屠呦呦和她的课题组深入到海南地区,进行实地考察。在2l位感染了Plasmodium vivax和P.falciparum这两种疟原虫的患者身上试用之后,发现青蒿萃取液治疗疟疾的临床效果出奇之好,使用青蒿萃取液治疗的病人很快退烧,血液中的疟原虫也很快消失。

    屠呦呦下一步要做的就是提取青蒿中的有效成分,确定这种有效成分的化学结构。1972年,屠呦呦和她的同事们在青蒿中提取到了一种分子式为C15H22O5的无色结晶体,一种熔点为156℃一157℃的活性成分,他们将这种无色的结晶体物质命名为青蒿素。

    他们终于找到了一种抗疟疾的有效药物。屠呦呦说:“青蒿素能够在疟原虫生命周期中任何一个阶段将其杀灭。”屠呦呦研究小组最初进行临床测试的药物形式是片剂,但结果并不太理想,后来改成一种新的形式——青蒿素提纯物的胶囊,由此开辟了发明一种抗疟疾新药的道路。1973年,屠呦呦合成出了双氢青蒿素,但当时她却不知道自己合成出来的这种化学物质以后被证明比天然青蒿素的效果还要好得多。

    生物学家和医学家、诺贝尔医学奖得主约瑟夫·戈尔斯坦曾说,生物医学的发展主要通过两种途径,一是发现,二是发明创造。而屠呦呦作为一位植物化学家,特别是在20世纪60年代至80年代期间,却有幸同时通过这两种途径发现了青蒿素及其抗疟功效,开创了人类抗疟之路上一个新的里程碑。

    2011年9月,青蒿素研究成果获得被看做诺贝尔奖“风向标”、有“美国的诺贝尔奖”之称的大奖——拉斯克临床医学奖,这是中国生物医学界迄今为止获得的最高的世界级大奖。

    青蒿,南北方都很常见的一种植物,郁郁葱葱地长在山野,外表朴实无华,却内蕴治病救人的魔力。屠呦呦说,她只是一个普通的植物化学研究人员,但作为一个在中国医药学宝库中有所发现,并为国际科学界所认可的中国科学家,她为获奖感到自豪。

同类题4

阅读理解

    George Gershwin, born in 1898, was one of America's greatest composers. He published his first song when he was eighteen years old. During the next twenty years he wrote more than five hundred songs.

    Many of Gershwin's songs were first written for musical plays performed in theatres in New York City. These plays were a popular form of entertainment in the 1920s and 1930s. Many of his songs have remained popular as ever. Over the years they have been sung and played in every possible way — from jazz to country.

    In the 1920s there was a debate in the United States about jazz music. Could jazz, some people asked, be considered serious music? In 1924 jazz musician and orchestra leader Paul Whiteman decided to organize a special concert to show that jazz was serious music. Gershwin agreed to compose something for the concert before he realized he had just a few weeks to do it. And in that short time, he composed a piece for piano and orchestra which he called Rhapsody in Blue. Gershwin himself played the piano at the concert. The audience were thrilled when they heard his music. It made him world-famous and showed that jazz music could be both serious and popular.

    In 1928, Gershwin went to Paris. He applied to study composition (作曲)with the well-known musician Nadia Boulanger, but she rejected him. She was afraid that classical study would ruin his jazz-influenced style. While there, Gershwin wrote An American in Paris. When it was first performed, critics (评论家)were divided over the music. Some called it happy and full of life, to others it was silly and boring. But it quickly became popular in Europe and the United States. It still remains one of his most famous works.

    George Gershwin died in 1937, just days after doctors learned he had brain cancer. He was only thirty-nine years old. Newspapers all over the world reported his death on their front pages. People mourned the loss of the man and all the music he might have still written.