全文获取类型
收费全文 | 3236篇 |
免费 | 189篇 |
出版年
2022年 | 10篇 |
2021年 | 21篇 |
2020年 | 15篇 |
2019年 | 8篇 |
2018年 | 14篇 |
2017年 | 19篇 |
2016年 | 54篇 |
2015年 | 72篇 |
2014年 | 104篇 |
2013年 | 150篇 |
2012年 | 172篇 |
2011年 | 191篇 |
2010年 | 127篇 |
2009年 | 131篇 |
2008年 | 204篇 |
2007年 | 225篇 |
2006年 | 198篇 |
2005年 | 202篇 |
2004年 | 202篇 |
2003年 | 210篇 |
2002年 | 215篇 |
2001年 | 43篇 |
2000年 | 30篇 |
1999年 | 50篇 |
1998年 | 72篇 |
1997年 | 58篇 |
1996年 | 41篇 |
1995年 | 49篇 |
1994年 | 40篇 |
1993年 | 37篇 |
1992年 | 43篇 |
1991年 | 25篇 |
1990年 | 25篇 |
1989年 | 22篇 |
1988年 | 27篇 |
1987年 | 18篇 |
1986年 | 21篇 |
1985年 | 27篇 |
1984年 | 29篇 |
1983年 | 23篇 |
1982年 | 30篇 |
1981年 | 19篇 |
1980年 | 18篇 |
1979年 | 12篇 |
1978年 | 18篇 |
1977年 | 20篇 |
1976年 | 20篇 |
1975年 | 16篇 |
1974年 | 10篇 |
1973年 | 14篇 |
排序方式: 共有3425条查询结果,搜索用时 15 毫秒
901.
Kuznetsov AV Kunz WS Saks V Usson Y Mazat JP Letellier T Gellerich FN Margreiter R 《Analytical biochemistry》2003,319(2):296-303
Long-term preservation of muscle mitochondria for consequent functional analysis is an important and still unresolved challenge in the clinical study of metabolic diseases and in the basic research of mitochondrial physiology. We here present a method for cryopreservation of mitochondria in various muscle types including human biopsies. Mitochondrial function was analyzed after freeze-thawing permeabilized muscle fibers using glycerol and dimethyl sulfoxide as cryoprotectant. Using optimal freeze-thawing conditions, high rates of adenosine 5(')-diphosphate-stimulated respiration and high respiratory control were observed, showing intactness of mitochondrial respiratory function after cryopreservation. Measurement of adenosine 5(')-triphosphate (ATP) formation showed normal rates of ATP synthesis and ATP/O ratios. Intactness of the outer mitochondrial membrane and functional coupling between mitochondrial creatine kinase and oxidative phosphorylation were verified by respiratory cytochrome c and creatine tests. Simultaneous confocal imaging of mitochondrial flavoproteins and nicotinamide adenine dinucleotide revealed normal intracellular arrangement and metabolic responses of mitochondria after freeze-thawing. The method therefore permits, after freezing and long-term storage of muscle samples, mitochondrial function to be estimated and energy metabolism to be monitored in situ. This will significantly expand the scope for screening and exchange of human biopsy samples between research centers, thus providing a new basis for functional analysis of mitochondrial defects in various diseases. 相似文献
902.
Setterdahl AT Chivers PT Hirasawa M Lemaire SD Keryer E Miginiac-Maslow M Kim SK Mason J Jacquot JP Longbine CC de Lamotte-Guery F Knaff DB 《Biochemistry》2003,42(50):14877-14884
Oxidation-reduction midpoint potential (E(m)) versus pH profiles were measured for wild-type thioredoxins from Escherichia coli and from the green alga Chlamydomonas reinhardtii and for a number of site-directed mutants of these two thioredoxins. These profiles all exhibit slopes of approximately -59 mV per pH unit, characteristic of the uptake of two protons per reduction of an active-site thioredoxin disulfide, at acidic, neutral, and moderately alkaline pH values. At higher pH values, these profiles exhibit slopes of either -29.5 mV per pH unit, characteristic of the uptake of one proton per disulfide reduced, or are pH-independent, indicating that neither proton uptake nor proton release is associated with reduction of the active-site disulfide. Reduction of the two wild-type thioredoxins is accompanied by the uptake of two protons even at pH values where the more acidic cysteine thiol group of the reduced proteins would be expected to be completely unprotonated. The effect of site-directed mutagenesis of two highly conserved aspartate residues that play important structural and/or catalytic roles in both thioredoxins, and which could in principle play a role in proton transfer, on the pK(a) values of redox-linked acid dissociations (deduced from changes in slope of the E(m) versus pH profiles) has also been determined for both E. coli thioredoxin and C. reinhardtii thioredoxin h. 相似文献
903.
A globin in the nucleus! 总被引:15,自引:0,他引:15
Geuens E Brouns I Flamez D Dewilde S Timmermans JP Moens L 《The Journal of biological chemistry》2003,278(33):30417-30420
904.
Unusual multiple recoding events leading to alternative forms of hepatitis C virus core protein from genotype 1b 总被引:11,自引:0,他引:11
Boulant S Becchi M Penin F Lavergne JP 《The Journal of biological chemistry》2003,278(46):45785-45792
905.
906.
907.
Amiard V Morvan-Bertrand A Billard JP Huault C Prud'homme MP 《Journal of experimental botany》2003,54(385):1231-1243
The role of fructans from leaf sheaths for the refoliation of Lolium perenne after severe defoliation was assessed by following the fate of (13)C-fructose supplied to leaf sheaths at the time of defoliation. At the end of the 4 h labelling period on defoliated plants, 77% of the (13)C incorporated was still located in leaf sheaths. Only 4% and 0.9% were, respectively, allocated to stem and roots, while 18% was imported by the growing leaves where (13)C was allocated first to the proximal part of the leaf growth zone (0-10 mm). In all tissues, the most highly (13)C-labelled carbohydrates was not fructose but sucrose. In leaf sheaths, (13)C-loliose was produced. In the leaf growth zone (0-20 mm), fructans were simultanously synthesized from (13)C entering the leaves and degraded. The export of (13)C from leaf sheaths continued during the first day of regrowth but stopped afterwards. There was no net loss of C from (13)C-fructose over the first 2 d of regrowth. The role of fructans and loliose is discussed as well as the physiological mechanisms contributing to defoliation tolerance in L. perenne. 相似文献
908.
Differential control of cell cycle,proliferation, and survival of primary T lymphocytes by purine and pyrimidine nucleotides 总被引:8,自引:0,他引:8
Quéméneur L Gerland LM Flacher M Ffrench M Revillard JP Genestier L 《Journal of immunology (Baltimore, Md. : 1950)》2003,170(10):4986-4995
Purine and pyrimidine nucleotides play critical roles in DNA and RNA synthesis as well as in membrane lipid biosynthesis and protein glycosylation. They are necessary for the development and survival of mature T lymphocytes. Activation of T lymphocytes is associated with an increase of purine and pyrimidine pools. However, the question of how purine vs pyrimidine nucleotides regulate proliferation, cell cycle, and survival of primary T lymphocytes following activation has not yet been specifically addressed. This was investigated in the present study by using well-known purine (mycophenolic acid, 6-mercaptopurine) and pyrimidine (methotrexate, 5-fluorouracil) inhibitors, which are used in neoplastic diseases or as immunosuppressive agents. The effect of these inhibitors was analyzed according to their time of addition with respect to the initiation of mitogenic activation. We showed that synthesis of both purine and pyrimidine nucleotides is required for T cell proliferation. However, purine and pyrimidine nucleotides differentially regulate the cell cycle since purines control both G(1) to S phase transition and progression through the S phase, whereas pyrimidines only control progression from early to intermediate S phase. Furthermore, inhibition of pyrimidine synthesis induces apoptosis whatever the time of inhibitor addition whereas inhibition of purine nucleotides induces apoptosis only when applied to already cycling T cells, suggesting that both purine and pyrimidine nucleotides are required for survival of cells committed into S phase. These findings reveal a hitherto unknown role of purine and pyrimidine de novo synthesis in regulating cell cycle progression and maintaining survival of activated T lymphocytes. 相似文献
909.
This study tests the effect on the laying rhythm of a light cycle reaching directly the encephala via a diode in Japanese quail maintained in constant darkness. In DD, all the birds expressed their free-running laying rhythm (period close to 25 h). When the diode is switched on 14 h per 24 h cycle, females showed the same organization as in LD with the same laying time. Thus, a photoperiodic cycle, where light was only perceived through the skull of the female quail, could synchronize its laying rhythm. This device with a LED is an interesting alternative solution to eye-patching or blinding of birds. 相似文献
910.
Death and the retrovirus 总被引:3,自引:0,他引:3