全文获取类型
收费全文 | 5928篇 |
免费 | 573篇 |
国内免费 | 2篇 |
出版年
2022年 | 39篇 |
2021年 | 136篇 |
2020年 | 80篇 |
2019年 | 95篇 |
2018年 | 103篇 |
2017年 | 86篇 |
2016年 | 164篇 |
2015年 | 270篇 |
2014年 | 295篇 |
2013年 | 333篇 |
2012年 | 473篇 |
2011年 | 470篇 |
2010年 | 288篇 |
2009年 | 219篇 |
2008年 | 372篇 |
2007年 | 376篇 |
2006年 | 296篇 |
2005年 | 331篇 |
2004年 | 303篇 |
2003年 | 262篇 |
2002年 | 276篇 |
2001年 | 65篇 |
2000年 | 72篇 |
1999年 | 85篇 |
1998年 | 68篇 |
1997年 | 45篇 |
1996年 | 37篇 |
1995年 | 41篇 |
1994年 | 31篇 |
1993年 | 25篇 |
1992年 | 33篇 |
1991年 | 41篇 |
1990年 | 39篇 |
1989年 | 40篇 |
1988年 | 31篇 |
1987年 | 31篇 |
1986年 | 34篇 |
1985年 | 28篇 |
1984年 | 21篇 |
1983年 | 32篇 |
1982年 | 24篇 |
1980年 | 19篇 |
1979年 | 26篇 |
1977年 | 20篇 |
1974年 | 27篇 |
1973年 | 20篇 |
1971年 | 20篇 |
1969年 | 22篇 |
1967年 | 18篇 |
1966年 | 20篇 |
排序方式: 共有6503条查询结果,搜索用时 15 毫秒
101.
James R. White Heather N. Yeowell 《Biochemical and biophysical research communications》1982,106(2):407-411
The lethal action of streptonigrin on strains of is greatly enhanced by citrate (10?2 M). Desferrioxamine (2×10?4 M), when added with streptonigrin and citrate, eliminates the citrate enhancement. These observations point to a role for iron in the bactericidal mechanism of streptonigrin. Extracellular citrate is known to promote the acquisition of iron by by delivering it as a ferric citrate complex to a specific transport apparatus on the cell envelope. Therefore, it may promote action of streptonigrin by increasing the intracellular concentration of available iron. Desferrioxamine, which forms a much stronger complex with ferric ion than does citrate, would be expected to suppress the ferric citrate effect, and this was observed. 相似文献
102.
103.
Injection of morphine or d-ala-2-met-5-enkephalinamide (DALA) into the paraventricular nucleus of the hypothalamus (PVN) produced a dose dependent increase in feeding in rats. DALA increased feeding within 45 minutes; morphine within 90 minutes. Naloxone injected into the PVN diminished the effect. DALA increased water intake only when food was available, suggesting the primary effect was on feeding. In summary, an enkephalin analogue induced feeding, and an opiate receptor blocker attenuated it; therefore the PVN may contain opiate receptors that facilitate feeding. 相似文献
104.
Cloned aerolysin of Aeromonas hydrophila is exported by a wild-type marine Vibrio strain but remains periplasmic in pleiotropic export mutants. 总被引:2,自引:1,他引:1 下载免费PDF全文
With a wide host range vector, the structural gene aerA for the hole-forming extracellular protein aerolysin of Aeromonas hydrophila was cloned into the marine Vibrio sp. strain 60 and into three pleiotropic export mutants (epr mutants). The parent strain and all of the mutants were able to express the protein with the aerA promoter in the plasmid. The parent strain exported proaerolysin into the medium, while all of the mutants accumulated the protoxin in their periplasms. Two of the mutants also accumulated protease; however, as we have found earlier with A. hydrophila, the periplasmic form of proaerolysin in the Vibrio sp. must somehow be protected from proteolysis because it was not converted to active toxin until the cells were shocked. Conversion could be prevented by adding o-phenanthroline to the solutions used in shocking. These results show that the export pathway in the marine Vibrio sp. is very similar to the pathway in A. hydrophila. 相似文献
105.
Isolation and characterization of the human hepatic lipase gene 总被引:7,自引:0,他引:7
D Ameis G Stahnke J Kobayashi J McLean G Lee M Büscher M C Schotz H Will 《The Journal of biological chemistry》1990,265(12):6552-6555
106.
107.
John S. Hothersall Salmata Zubairu Patricia McLean A. Leslie Greenbaum 《Journal of neurochemistry》1981,37(6):1484-1496
The effect of 6-aminonicotinamide (6AN) treatment on the activities of alternative pathways of glucose metabolism in 20-day-old rat brain was evaluated by measurements of yields of 14CO2 from glucose labeled with 14C on carbons 1, 2, 3 + 4, or 6 and uniformly labeled glucose, and from the incorporation of 14C from specifically labeled glucose into lipids by brain slices from cerebral hemispheres and cerebellum. At the highest dose of 6AN used (35 mg/kg body weight) there was a significant decrease in the 14CO2 yields via the pentose phosphate pathway, the glycolytic route, tricarboxylic acid (TCA) cycle, and via the glutamate-gamma-aminobutyric acid pathway. Giving a graded series of doses (20-35 mg 6AN/kg body weight) revealed a hierarchy of responses in which the pentose phosphate pathway, lactate, glyceride-glycerol, and fatty acid formation were most sensitive, followed, in sequence, by the pyruvate dehydrogenase reaction, the glutamate-gamma-aminobutyrate route and, finally, the TCA cycle. The nature of the blocks in the various pathways was examined by the use of metabolite profiles. 相似文献
108.
Angie Rizzino Victor Terranova David Rohrbach Craig Crowley Heather Rizzino 《Journal of cellular biochemistry》1980,13(2):243-253
In this paper we have examined the growth and differentiation of the embryonal carcinoma cell line, F9, in the defined medium EM-3 at low density. We show that the growth of F9 and their differentiated cells (F9-diff) in EM-3 is strongly density dependent. At low cell densities the growth of both cell types is severely limited and most of the cells do not survive. Although this poses a problem for working with F9 and F9-diff in EM-3, it provides a convenient assay for identifying molecules that support their growth at low density. Using this assay, we have determined that laminin, a newly isolated glycoprotein of basement membranes, significantly improves the growth and short-term survival of both F9 and F9-diff. However, addition of laminin to EM-3 is insufficient to promote the clonal growth of these cell types. Our findings also indicate that laminin promotes the attachment of F9 and F9-diff in defined media. On the basis of our results, we propose an attachment function for laminin during the early stages of mammalian development. 相似文献
109.
Heather Windle 《BMJ (Clinical research ed.)》1980,280(6229):1425-1426
110.
Effect of experimental diabetes on glycolytic intermediates and regulation of phosphofructokinase in rat lens 总被引:1,自引:0,他引:1
A M Gonzalez M Sochor P McLean 《Biochemical and biophysical research communications》1980,95(3):1173-1179
The pattern of glycolytic intermediates in the lens of alloxan-diabetic rats was indicative of regulation at phosphofructokinase. The changes in metabolites influencing phosphofructokinase activity in the diabetic, relative to the normal, rat lens were: glucose 6-phosphate, 182%; fructose 6-phosphate, 107%; fructose diphosphate, 57%. There was also a marked decrease in phosphoenolpyruvate, pyruvate, lactate and ATP but no significant change in other triose phosphates or cyclic AMP. The resuts are considered in relation to the early changes in [Ca2+] known to occur in lens in diabetes and to the coordinating effect of fructose diphosphate on flux through the glycolytic route. 相似文献