单选题下列对于环核苷酸的叙述，哪一项是错误的?______

单选题丙酮酸羧化酶催化丙酮酸羧化的产物是

单选题化学毒气路易士气对酶的抑制作用属于

单选题关于乳糜微粒的叙述，错误的是

单选题在重组 DNA 技术中，不常用的酶是

单选题糖代谢中间产物中含有高能磷酸键的是（）。

单选题转录起始生成RNA的第一个核苷酸最常见的是

单选题电子传递链中生成ATP的三个部位是

单选题离体肝线粒体中加入氰化物和丙酮酸，其P／O比值是

单选题以下哪种情况不宜做桩冠修复

单选题下列哪项不属于蛋白质分子的二级结构

单选题转录延长中，RNA聚合酶与DNA模板的结合是

单选题People don't want to buy information online. Why? Because they don't have to. No more than that because they're used to not paying for it. That's the conventional wisdom. Slate, Microsoft's online politics-and-culture magazine, is an oft-cited example of the failed attempts to charge a fee for access to content. So far, for most publishers, it hasn't worked. But nothing on the Web is a done deal. In September graphics-soft-ware powerhouse Adobe announced new applications that integrate commerce into downloading books and articles online, with Simon Schuster, Barnes and Noble, and Salon. corn among its high-profile partners. Some analysts put the market for digitized publishing at more than $100 billion. Of course, if the Internet can generate that kind of money—some might say almost any kind of money—people want in. And this couldn't come at a better time. Newspaper and magazine writers in particular are increasingly frustrated by their publishers, which post their writings online but frequently don't pay them extra. So here's the good news: Fathrain. com, the third biggest book-seller on the Net—after Amazon. com and Barnesandnoble. corn—is now doing just what the publishing industry that made it a success fears., it's offering a secure way to pay for downloadable manuscripts online. Fatbrain calls it offshoot eMatter. With it, the company's executives have the radical notion of ousting publishers from the book-selling business altogether by giving writers 50% of each and every sale (To reel in authors, eMatter is running a 100% royalty promotion until the end of the year. ) Suggested prices to consumers range from a minimum $ 2 to $ 20, depending on the size of the book to download. "This will change publishing forever!" Chris MaeAskill, co-founder and chief executive of Fatbrain, declares with the bravado of an interior decorator. "With eBay, anybody could sell antiques. Now anybody can be published. " There's been no shortage of authors wanting in. Within a few weeks, according to the company, some 2,000 writers signed on to publish their works. Some of this is technical stuff—Fatbrain got where it is by specializing in technical books—but there are some well-known writers like Catherine Lanigan, author of Romancing the Stone, who has put her out-of-print books and a new novella on the site. Another popular draw is Richard Bach, who agreed to post a 23-page short story to the site. Not everyone thinks downloadable documents are the biggest thing in publishing since Oprah's Book Club. "I think it will appeal to sellers more than buyers," says Michael May, a digitalcommerce analyst at Jupiter Communications, which released a report that cast doubt on the market's potential. "A lot of people are going to publish gibberish. The challenge is to ensure the quality of the work. " Blaine Mathieu, an analyst at Gartner Group's Dataquest, says, "Most people who want digital content want it immediately, I don't know if this model would satisfy their immediate need. Even authors may not find that Web distribution of their works is going to bring them a pot of gold. For one thing, it could undermine sales rather than enhance them. For another, anybody could e-mail downloaded copies of manuscripts around town or around the world over the Net without the writer's ever seeing a proverbial dime. " Softlock. com, Authentica and Fatbrain are trying to head this problem off by developing encryption padlocks that would allow only one hard drive to receive and print the manuscripts. For now, the problem persists.

单选题下述有关生物转化作用的论述恰当的是

单选题下列哪种碱基只见于RNA而不见于DNA

单选题下列哪条途径与核酸合成密切相关

单选题维持蛋白质一级结构的主要化学键是

单选题DNA复制时不需要以下哪种酶

单选题关于原核生物DNA聚合酶的叙述，下列哪项是错误的

单选题胰岛素分子由两条肽链组成，其A链和B链的连接靠