单选题聚合酶链反应(PCR)不需要

单选题DNA甲基化是基因表达调控的重要方式之一，甲基化的位点是______。 A．CpG岛上的C的3位 B．CpG岛上的G的3位 C．CpG岛上的C的5位D．CpG岛上的G的7位

单选题肠道内胆汁酸主要的重吸收方式是

单选题It used to be so straightforward. A team of researchers working together in the laboratory would submit the results of their research to a journal. A journal editor would then remove the authors' names and affiliations from the paper and send it to their peers for review. Depending on the comments received, the editor would accept the paper for publication or decline it. Copyright rested with the journal publisher, and researchers seeking knowledge of the results would have to subscribe to the journal. No longer. The Internet—and pressure from funding agencies, who are questioning why commercial publishers are making money from government-funded research by restricting access to it—is making access to scientific results a reality. The Organization for Economic Co-operation and Development (OECD) has just issued a report describing the far-reaching consequences of this. The report, by John Houghton of Victoria University in Australia and Graham Vickery of the OECD, makes heavy reading for publishers who have, so far, made handsome profits. But it goes further than that. It signals a change in what has, until now, been a key element of scientific endeavor. The value of knowledge and the return on the public investment in research depends, in part, upon wide distribution and ready access. It is big business. In America, the core scientific publishing market is estimated at between $ 7 billion and $ 11 billion. The International Association of Scientific, Technical and Medical Publishers says that there are more than 2 000 publishers worldwide specializing in these subjects. They publish more than 1.2 million articles each year in some 16 000 journals. This is now changing. According to the OECD report, some 75% of scholarly journals are now online. Entirely new business models are emerging; three main ones were identified by the report's authors. There is the so-called big deal, where institutional subscribers pay for access to a collection of online journal titles through site-licensing agreements. There is open-access publishing, typically sup- ported by asking the author (or his employer) to pay for the paper to be published: Finally, there are open-access archives, where organizations such as universities or international laboratories support institutional repositories. Other models exist that are hybrids of these three, such as delayed open-access, where. journals allow only subscribers to read a paper for the first six months, before making it freely available to everyone who wishes to see it. All this could change the traditional form of the peer- review process, at least for the publication of papers.

单选题在转录延长中，RNA聚合酶与DNA模板的结合是

单选题参与酮体氧化的酶是

单选题下列有关类脂中错误的叙述是

单选题多食糖类需补充

单选题关于遗传信息的储存和表达的叙述，正确的是

单选题与mRNA中密码子5′-GAC-3′酉己又寸识别的tRNA反密码子是

单选题下列关于PTEN的叙述，正确的是

单选题蛋白质含氮量平均约为

单选题下列机制中，最主要参与解氨毒作用的是（ ）

单选题 关于嘧啶二聚体形成下列说法错误的是 A、属于DNA链内交联 B、形式有TT、CT、CC C、属于DNA链间交联 D、可由光复活酶修复 E、紫外线照射可引起此种损伤

单选题线粒体氧化磷酸化解偶联意味着

单选题嘌呤环的合成中向嘌呤环只提供一个碳原子的化合物是

单选题关于脆性X综合征的叙述，不正确的是

单选题血液中结合胆红素的蛋内质是（ ）

单选题下列辅酶中的哪个不是来自于B族维生素

单选题酶与一般催化剂的区别是