全文获取类型
收费全文 | 8384篇 |
免费 | 699篇 |
国内免费 | 2篇 |
专业分类
9085篇 |
出版年
2023年 | 33篇 |
2021年 | 58篇 |
2020年 | 41篇 |
2019年 | 46篇 |
2018年 | 152篇 |
2017年 | 162篇 |
2016年 | 238篇 |
2015年 | 412篇 |
2014年 | 399篇 |
2013年 | 542篇 |
2012年 | 733篇 |
2011年 | 681篇 |
2010年 | 427篇 |
2009年 | 321篇 |
2008年 | 546篇 |
2007年 | 576篇 |
2006年 | 537篇 |
2005年 | 573篇 |
2004年 | 537篇 |
2003年 | 487篇 |
2002年 | 444篇 |
2001年 | 36篇 |
2000年 | 61篇 |
1999年 | 65篇 |
1998年 | 66篇 |
1997年 | 40篇 |
1996年 | 38篇 |
1995年 | 42篇 |
1994年 | 37篇 |
1993年 | 36篇 |
1992年 | 56篇 |
1991年 | 38篇 |
1990年 | 35篇 |
1989年 | 33篇 |
1988年 | 26篇 |
1987年 | 26篇 |
1986年 | 18篇 |
1985年 | 25篇 |
1984年 | 39篇 |
1983年 | 25篇 |
1982年 | 33篇 |
1981年 | 36篇 |
1980年 | 40篇 |
1979年 | 30篇 |
1978年 | 34篇 |
1977年 | 29篇 |
1976年 | 31篇 |
1975年 | 25篇 |
1974年 | 18篇 |
1973年 | 17篇 |
排序方式: 共有9085条查询结果,搜索用时 15 毫秒
1.
François Frappier Andrée Marquet 《Biochemical and biophysical research communications》1981,103(4):1288-1293
[3-14C, 35S]-L-cysteine was tested as precursor of biotin in Achromobacter IVSW. No significant incorporation was observed, in contradiction with the data previously reported. On the other hand, Achromobacter IVSW converts [3H, 14C]-dethiobiotin into biotin. This suggests that biotin is biosynthesized in Achromobacter according to the classical dethiobiotin pathway. 相似文献
2.
Evelyne Decullier Véronique Lhéritier Fran?ois Chapuis 《BMJ (Clinical research ed.)》2005,331(7507):19
Objectives To describe the fate of protocols approved by the French research ethics committees, a national system created by the French 1988 Huriet-Sérusclat Act; to assess publication bias at a national level.Design Retrospective cohort study.Setting Representative sample of 25/48 French research ethics committees in 1994.Protocols 649 research protocols approved by committees, with follow-up information.Main outcome measures Protocols'' initial characteristics (design, study size, investigator) abstracted from committees'' archives; follow-up information (rates of initiation, completion, and publication) obtained from mailed questionnaire to principal investigators.Results Completed questionnaires were available for 649/976 (69%) protocols. Of these, 581 (90%) studies were initiated, 501/581 (86%) were completed, and 190/501 (38%) were published. Studies with confirmatory results were more likely to be published as scientific papers than were studies with inconclusive results (adjusted odds ratio 4.59, 95% confidence interval 2.21 to 9.54). Moreover, studies with confirmatory results were published more quickly than studies with inconclusive results (hazard ratio 2.48, 1.36 to 4.55).Conclusion At a national level, too many research studies are not completed, and among those completed too many are not published. We suggest capitalising on research ethics committees to register and follow all authorised research on human participants on a systematic and prospective basis. 相似文献
3.
RegB is involved in the control of the phage T4 life cycle. It inactivates the phage early mRNAs when their translation is
no more required. We determined its structure and identified residues involved in substrate binding. For this, all backbone
and 90% of side-chain resonance frequencies were assigned. 相似文献
4.
Adolescence is a period marked by the search for sexual identity. How do paraplegic or quadriplegic teenagers develop their sexual identity? How can the nursing team help them in this process? The authors study erection and the quality of sexual relations and then examine the problem of procreation. Early, practical information adapted to the neurological definition of the spinal cord injury is essential, with preservation of sperm prior to the development of urological and infectious complications. The authors report their experience of 24 paraplegic or tetraplegic teenagers at the CMPA in Neufmoutiers and the CECOS at Cochin Hospital in Paris. 相似文献
5.
Antoine Sioufi Françoise Pommier 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1980,181(2):161-168
A method for the determination of benzoic acid down to concentrations of 10 ng/ml in plasma or urine is described. After addition of an internal standard, benzoic acid is extracted at acid pH into diethyl ether. Both compounds are derivatized with pentafluorobenzyl bromide. The derivatives are determined by gas chromatography using a 43Ni electron-capture detector. Hippuric acid is hydrolysed in plasma and urine and total benzoic acid is determined by the same technique. 相似文献
6.
7.
8.
Catherine Bonaïti-Pellié Françoise Clerget-Darpoux Marie-Claude Babron 《Human genetics》1990,86(2):203-208
Summary Although the retinoblastoma gene has been isolated and sequenced, the difference in penetrance and expressivity among families has not yet been fully explained. Balanced chromosomal insertion involving the 13q14 regions has been shown to account for some families with several unaffected carriers. Since there could be cases with karyotypically undetectable insertions, we tested whether this mechanism was general enough to explain the whole difference in expressivity among families. Using 166 pedigrees, reported in nine series available in the literature (including our own), we conclude that balanced insertion cannot entirely explain the familial data, even if we allow for a reduced viability of unbalanced gametes. Other mechanisms are proposed and discussed in this paper. 相似文献
9.
10.
Four main molecular forms of acetylcholinesterase (AChE) can be solubilized from newborn rat superior cervical ganglia (SCG), homogenized in the presence of a high-ionic-strength, detergent-containing medium. These forms, respectively referred to as 16, 10, 6.5, and 4 S, are characterized by their sedimentation coefficients. Their relative proportions in SCG are notably different in vivo during postnatal maturation, and in culture. The 16-S AChE appears to be mainly neuronal in origin, is maintained in culture independently of original presynaptic in vivo elements, and its cellular pool is not depleted in the presence of tetrodotoxin (TTX). 相似文献