全文获取类型
收费全文 | 49912篇 |
免费 | 4551篇 |
国内免费 | 31篇 |
专业分类
54494篇 |
出版年
2022年 | 361篇 |
2021年 | 758篇 |
2020年 | 452篇 |
2019年 | 567篇 |
2018年 | 701篇 |
2017年 | 647篇 |
2016年 | 1039篇 |
2015年 | 1751篇 |
2014年 | 1934篇 |
2013年 | 2542篇 |
2012年 | 3217篇 |
2011年 | 3279篇 |
2010年 | 2126篇 |
2009年 | 1902篇 |
2008年 | 2705篇 |
2007年 | 2813篇 |
2006年 | 2744篇 |
2005年 | 2627篇 |
2004年 | 2527篇 |
2003年 | 2398篇 |
2002年 | 2297篇 |
2001年 | 538篇 |
2000年 | 444篇 |
1999年 | 607篇 |
1998年 | 729篇 |
1997年 | 547篇 |
1996年 | 470篇 |
1995年 | 427篇 |
1994年 | 411篇 |
1993年 | 440篇 |
1992年 | 475篇 |
1991年 | 412篇 |
1990年 | 403篇 |
1989年 | 390篇 |
1988年 | 364篇 |
1987年 | 326篇 |
1986年 | 350篇 |
1985年 | 375篇 |
1984年 | 453篇 |
1983年 | 372篇 |
1982年 | 477篇 |
1981年 | 492篇 |
1980年 | 389篇 |
1979年 | 320篇 |
1978年 | 334篇 |
1977年 | 293篇 |
1976年 | 328篇 |
1975年 | 220篇 |
1974年 | 275篇 |
1973年 | 271篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
C5L2, a nonsignaling C5A binding protein 总被引:11,自引:0,他引:11
Okinaga S Slattery D Humbles A Zsengeller Z Morteau O Kinrade MB Brodbeck RM Krause JE Choe HR Gerard NP Gerard C 《Biochemistry》2003,42(31):9406-9415
982.
983.
984.
G. L. Collingridge G. G. S. Collins J. Davies T. A. James M. J. Neal P. Tongroach 《Journal of neurochemistry》1980,34(3):540-547
Abstract: The effect of tetanus toxin on the uptake and release of radiolabelled transmitters from slices prepared from substantia nigra (SN) and striatum of rats has been investigated. Tetanus toxin-500–750 mouse lethal doses (MLD)-injected into the SN 6 h before preparing the slices significantly reduced the calcium-dependent, potassium-evoked release of [3 H]GABA. Endogenous GABA levels in the SN and [3 H]GABA uptake by nigral slices were unaffected by pretreatment with the toxin. Injections of tetanus toxin (1000–2000 MLD) into the striatum significantly reduced the calcium-dependent, potassium-evoked release of [14 C]GABA and also [3 H]dopamine, but had no effect on the K+ -evoked release of [3 H]5-hydroxytryptamine or [14 C]acetylcholine. It is concluded that tetanus toxin inhibits GABA release directly and not by interference with synthesis or inactivation processes. 相似文献
985.
986.
Terry I. Korotzer James A. Clagett William P. Kolb Roy C. Page 《Journal of cellular physiology》1980,105(3):503-512
The effects of fresh human serum (FHS) and heat-inactivated human serum (HHS) on the DNA synthesis and proliferation of human diploid fibroblasts were assessed. FHS activated significantly more quiescent fibroblasts to undergo DNA synthesis and proliferation than did HHS. The stimulatory effect occurred consistently over a serum concentration range of 0.1–10%. Using bromodeoxyuridine selective killing techniques, it was shown that this FHS stimulatory effect was on a specific subpopulation of fibroblasts unresponsive to HHS. The involvement of the complement system, and specifically of C1, was shown by the inability of Clq-depleted FHS to support enhanced DNA synthesis whereas Clq-depleted serum reconstituted with purified Clq was effective. Purified Clq did not restore activity when added to heated serum, nor was it mitogenic when tested in basal medium without serum. The addition of purified Clq to fresh serum inhibited the enhancement of DNA synthesis, and at Clq concentrations of 4γ/ml and greater, the fresh serum effects were abrogated. Thus, it appears that binding of the assembled C1 complex to the fibroblast surface was required for FHS-mediated enhancement of fibroblast proliferation, with Clq subcomponent serving as the recognition site. The results from several experiments indicated that antibody was not required for the complement-dependent fibroblast activation. FHS was not cytotoxic, and autologous serum was as effective as allogeneic sera. A 20-fold molar excess of Fab' from pooled human IgG did not alter the FHS effects. FHS from which IgG was more than 99% depleted was still effective. These results suggested an antibody-independent role for complement in the activation of a subpopulation of human diploid fibroblasts. 相似文献
987.
Monte Carlo study of the effect of β2-microglobulin on the binding cleft of the HLA-A2 complex 下载免费PDF全文
Djamal Bouzida Jean Garnier Richard Brower James Cornette Charles Delisi 《Protein science : a publication of the Protein Society》1994,3(6):911-919
Peptide recognition by class I products of the major histocompatibility complex requires association of the class I heavy chain with β2-microglobulin. We present results of Monte Carlo simulations of the β-pleated sheet floor of the human class I MHC molecule, HLA-A2, with and without β2-microglobulin. We find a significant effect of β2-microglobulin on the side chains of residues near a region that would accommodate the C-terminus of a bound peptide. By modeling simultaneously each loop and its neighboring strand at either end of the class I cleft, we find that β2-microglobulin restricts the conformational space of residues that are central to binding peptides. The effect is most pronounced for R97 and H114 and somewhat less important for Y99 and Y116, the latter forming strong hydrogen bonds with neighboring residues in the heavy chain itself. 相似文献
988.
989.
Roland Greinwald Ricardo Reyes-Chilpa James H. Ross Ludger Witte Franz-Christian Czygan 《Biochemical Systematics and Ecology》1996,24(7-8):749-755
The presence of alkaloids in six species of Brongniartia and three species of Harpalyce is reported. This survey revealed remarkable qualitative differences in the alkaloid profiles of these two genera. B. discolor, B. lupinoides, B. sousae and B. intermedia showed a typical -pyridone pattern, with cytisine, anagyrine and baptifoline as major alkaloids. In leaves of the first three species ormosanine-type alkaloids occurred additionally. B. flava and B. vazquezii are devoid of -pyridones, but accumulate lupanine, hydroxylated lupanines and ester alkaloids. All three species of Harpalyce were similar in accumulating -pyridones, but H. formosa differed from H. brasiliana and H. pringlei in the presence of epilupinine. In general the alkaloid profiles of Brongniartia and Harpalyce show similarities to those of the Australian genera Hovea, Lamprolobium, Plagiocarpus and Templetonia and support therefore the actual concept of the enlarged tribe Brongniartieae. 相似文献
990.