用NaOH滴定H2C2O4应选用( )项作指示电极。A．Pt电极 B．氟电极 C．

医师在开处方时所考虑的原则是

A．以正确的剂量，正确的药物，通过正确的途径给予正确的患者

B．在正确的时间，以正确的药物，通过正确的途径给予正确的患者

C．在正确的时间，以正确的药物，给予正确的患者

D．在正确的时间，以正确的剂量，正确的药物，给予正确的患者

E．在正确的时间，以正确的剂量，正确的药物，通过正确的途径给予正确的患者

下列不属于无性生殖的是[ ]

A．利用植物的种子繁殖水稻、小麦    

B．利用植物组织培养技术培育水稻、小麦

C．靠植物的根、茎、叶繁殖新个体    

D．酵母菌的出芽生殖

水的软硬程度会影响茶叶的有效成分的溶解度。（）中含其他溶质少，茶叶有效成分的溶解度高，固茶汤味浓。

A、泉水

B、江河水

C、雪水

D、自来水

设随机变量X的概率密度函数为

以Y表示对X进行三次独立重复观察中事件

出现的次数，则PY=2)=______．

Jan Hendrik Schon’s success seemed too good to be true, and it was. In only four years as a physicist at Bell Laboratories, Schon, 32, had co-authored 90 scientific papers—one every 16 days—detailing new discoveries in superconductivity, lasers, nanotechnology and quantum physics. This output astonished his colleagues, and made them suspicious. When one co-worker noticed that the same table of data appeared in two separate papers—which also happened to appear in the two most prestigious scientific journals in the world, Science and Nature—the jig was up. In October 2002, a Bell Labs investigation found that Schon had falsified and fabricated data. His career as a scientist was finished. Scientific scandals, which are as old as science itself, tend to follow similar patterns of presumption and due reward.

In recent years, of course, the pressure on scientists to publish in the top journals has increased, making the journals much more crucial to career success. The questions are whether Nature and Science have become too powerful as arbiters of what science reaches to the public, and whether the journals are up to their task as gatekeepers.

Each scientific specialty has its own set of journals. Physicists have Physical Review Letters, neuroscientists have Neuron, and so forth. Science and Nature, though, are the only two major journals that cover the gamut of scientific disciplines, from meteorology and zoology to quantum physics and chemistry. As a result, journalists look to them each week for the cream of the crop of new science papers. And scientists look to the journals in part to reach journalists. Why do they care Competition for grants has gotten so fierce that scientists have sought popular renown to gain an edge over their rivals. Publication in specialized journals will win the acclaims from academics and satisfy the publish-or-perish imperative, but Science and Nature come with the added bonus of potentially getting your paper written up in The New York Times and other publications.

Scientists tend to pay more attention to the big two than to other journals. When more scientists know about a particular paper, they’re more apt to cite it in their own papers. Being oft-cited will increase a scientist’s "Impact Factor", a measure of how often papers are cited by peers. Funding agencies use the "Impact Factor" as a rough measure of the influence of scientists they’re considering supporting.

The expression "the cream of the crop" in Paragraph 3 most likely means " () ".

A. the most of all

B. the best of all

C. the recently released

D. the widely spread