单选题下列各酶中，催化UDPGA生成的酶是

单选题三羧酸循环中发生脱羧反应的有机酸是

单选题脑中γ-氨基丁酸是由哪种物质转化产生的

单选题竞争性抑制剂对酶反应速度的影响是

单选题A．FAD B．NAD + C．NADP + D．NADPH+H +

单选题下列哪一物质不是糖异生的原料

单选题A．胰高血糖素B．胰岛素C．甲状腺素D．肾上腺素

单选题下列DNA分子中，解链温度(Tm)最高的是( )(2009年)

单选题下列哪种酶的作用需要GTP

单选题蛋白质溶液的稳定因素是

单选题Lesch-Nyhan综合征是因为缺乏

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.

单选题维生素B 2 的活性形式是

单选题丙酮酸羧化酶的变构激活剂

单选题Leave it to writer Buchwald to bring humor to hospice. Last February, the famed satirist was diagnosed with terminal kidney failure, given three weeks to live, and transferred to a hospice for a quiet goodbye. Then the unexpected happened. His kidneys almost miraculously started working again. The poisons in his blood that were supposed to carry him out in peaceful slumber(死亡) washed out of his system, leaving instead a funny bone stunned and amused by the absurdity of the situation. It's not every day that someone flunks hospice. Seasoned author that he is, Buchwald turned the irony into a book. Only 10 months ago, he was a sad, 80-year-old man with a newly amputated(切除) leg and kidneys on the fritz(发生故障). Despite his family's pleas, he entered a hospice facility, at ease with his Choice to die naturally. Most people don't know much about hospice, the place. It doesn't cure; it cares, relieving physical pain and mental anguish. Most often, cancer or cardiovascular(心血管病) disease carries hospice patients to their end, usually in weeks. But some are put on hold like Buchwald. Buchwald left after five months. In one large study, 6 percent of hospice patients improved enough to be taken off the terminal list and sent home. Buchwald was shocked when the big sleep didn't come. Before Buchwald became the hospice's superstar, he had been the poster boy for depression. But with the help of physicians and medication, he didn't drown. Laugh or cry. Facing natural death, he now offers a message many of his contemporaries need to hear. Older men, particularly those in their 80s, have the highest rate of suicide. Risk factors for them notably include health issues. In fact, suicide often comes soon after they've seen a doctor. On that point, Buchwald notes the medical dearth of smiles and laughter." Look at how often doctors and nurses walk into a patient's room all serious," he says. His prescription? They" need to go to Disney World to be trained." Laughter, of course, is the best medicine, and some studies even show humor is a biological stress reliever. As Buchwald sees it, many humorists use it as therapy to block out periods of hurt or anger. You would not know there were hurts or anger judging by his hospice time. Friends and family smothered Buchwald with love. VIPs beat a path to the hospice door. And they all came bearing food, lots of cheesecake. He thrived. After he planned his funeral, he started up writing again and found he could write wonderfully. Buchwald is now teaching all of us how to live--and to die. Yet he's quick to add," I have had such a good time at the hospice. I am going to miss it./

单选题合成胆固醇的直接原料为

单选题参与酮体氧化的酶是

单选题多食糖类需补充

单选题抑制dUMP转变成dTMP的是

单选题合成血红素的原料是