单选题6一巯基嘌呤和别嘌呤醇能够抑制尿素合成的主要原因是其结构相似于

单选题下列反应中属于酶化学修饰的是( )(2012年)

单选题有关Rb基因的描述，不正确的是

单选题DNA受热变性时，出现的现象是( )(2005年)

单选题糖有氧氧化抑制糖酵解的作用称为

单选题A．非竞争性抑制B．反竞争性抑制C．二者都是D．二者均否

单选题下列何种物质与苹果酸穿梭过程无关

单选题磺胺类药物能竞争抑制二氢叶酸还原酶是因为其结构相似于( )(2004年)

单选题在下列代谢反应中，哪个反应是错误的

单选题关于抑癌基因的叙述，下列哪一项是正确的

单选题下列哪种激素能同时促进糖原、脂肪、蛋白质合成

单选题蛋白质变性后的主要表现是( )(2009年)

单选题A．拓扑异构酶B．DNA、解旋酶C．DNA聚合酶ⅠD．DNA聚合酶ⅢE．DNA连接酶

单选题甲状腺功能亢进患者基础代谢率增高的原因是

单选题框移突变与密码子的哪项特性有关

单选题下面哪种酶在糖酵解和糖异生中都起作用

单选题Several years ago, at the height of the dotcom boom, it was widely assumed that a publishing revolution, in which the printed word would be supplanted by the computer screen, was just around the corner. It wasn't: for many, there is still little to match the joy of reading a printed book and settling down for one hour. But recently some big technology companies, including Google, Amazon, Microsoft and Yahoo, contend that the dream of bringing books online is still very much alive. The digitizing of thousands of volumes of print is not without controversy. On Thursday, Google, the world' s most popular search engine, posted a first installment of books on Google Print. This collaborative effort between Google and several world's leading research libraries aims to make books available to be searched and read online free of charge. Although the books included so far are not covered by copyright, the plan has attracted the rage of publishers. Five large book firms are suing Google for violating copyright on material that it has scanned and, although out of print, is still protected by law. Google has said that it will only publish short extracts from material under copyright unless given express permission to publish more, but publishers are unconvinced. Ironically, many publishers are collaborating with Google Print Publisher, which aims to give readers an online taste of books that are commercially available. The searchable collection of extracts and book information is intended to tempt readers to buy the complete books online or in print form. Amazon, the world's largest online retailer, has made plans to enter the mass e-book market by selling a vast array of goods. Given that Google should impinge upon its central territory, Amazon revealed that it would introduce two new services. Amazon Pages will allow customers to search for key terms in selected books and then buy and read online whatever part they wish. Amazon Upgrade will give customers online access to books they have already purchased as hard copies. Customers are likely to have to pay five cents a page, with the bulk going to the publisher. Microsoft has also joined the online-book trend. In October, the software giant said it would spend around $ 200 million to digitize texts, starting with I50,000 that are in the public domain, to avoid legal problems. It will do so in collaboration with the Open Content Alliance. And on Thursday, coincidentally the same day as Google and Amazon announced their initiatives, Microsoft released details of a deal with the British Library, the country's main reference library, to digitize some 25 million pages ; these will be made available through MSN Book Search, which will be launched next year.

单选题A．胞质B．线粒体和胞质C．微粒体D．细胞核E．溶酶体

单选题DNA理化性质中的“T m ”值所表达的含义是

单选题丙氨酸-葡萄糖循环的作用除转运氨外还可