全文获取类型
收费全文 | 13349篇 |
免费 | 847篇 |
国内免费 | 346篇 |
出版年
2023年 | 212篇 |
2022年 | 289篇 |
2021年 | 414篇 |
2020年 | 464篇 |
2019年 | 633篇 |
2018年 | 640篇 |
2017年 | 456篇 |
2016年 | 390篇 |
2015年 | 351篇 |
2014年 | 731篇 |
2013年 | 1078篇 |
2012年 | 454篇 |
2011年 | 675篇 |
2010年 | 498篇 |
2009年 | 583篇 |
2008年 | 584篇 |
2007年 | 724篇 |
2006年 | 538篇 |
2005年 | 461篇 |
2004年 | 365篇 |
2003年 | 403篇 |
2002年 | 357篇 |
2001年 | 232篇 |
2000年 | 183篇 |
1999年 | 201篇 |
1998年 | 197篇 |
1997年 | 184篇 |
1996年 | 169篇 |
1995年 | 173篇 |
1994年 | 152篇 |
1993年 | 148篇 |
1992年 | 144篇 |
1991年 | 125篇 |
1990年 | 77篇 |
1989年 | 77篇 |
1988年 | 60篇 |
1987年 | 67篇 |
1986年 | 65篇 |
1985年 | 123篇 |
1984年 | 140篇 |
1983年 | 72篇 |
1982年 | 100篇 |
1981年 | 83篇 |
1980年 | 114篇 |
1979年 | 64篇 |
1978年 | 62篇 |
1977年 | 46篇 |
1976年 | 40篇 |
1975年 | 37篇 |
1974年 | 45篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
M Cohn 《Biochimie》1985,67(1):9-27
Two concepts of the evolution and regulation of expression of the combining site repertoire of the immune system, are compared. One view is based on the Associative Recognition Theory as formulated by the author and the other is based on the Idiotype Network Idea as conceived by Jerne. The two concepts are analyzed from the point of view of their logic, internal consistency and factual support. 相似文献
92.
Immunocytochemical detection of 28000-MW calcium-binding protein in horizontal cells of the rat retina 总被引:1,自引:0,他引:1
Summary Horizontal cells of rat retina were labeled intensely by a specific antibody to cerebellar calcium-binding protein. The amacrine cells stained very weakly. The presence of calcium-binding protein in horizontal cells could be of interest for the understanding of the feedback action of these cells on photoreceptors.Abbreviations used CaBP
calcium-binding protein
- DAB
3,3-diaminobenzidine
- PAP
unlabelled antibody peroxidase-antiperoxidase immunocytochemical complex
On leave from the Department of Physiology, University of British Columbia, Vancouver, Canada 相似文献
93.
Regulation of the loss of frost hardiness in Pinus radiata by photoperiod and temperature 总被引:2,自引:1,他引:1
Abstract. In controlled environments, the interactive effects of warm (16: 8°C, day: night) and cool (12: 4°C, day: night) temperatures and long (13.5 h) and short (10 h) photoperiods on the dehardening of seedlings of Pinus radiata D. Don were investigated. In another experiment, the effect of four photoperiods from 9 to 14 h was examined. In a third, dehardening at constant temperatures from 5 to 17°C was followed. There was no evidence for an interaction between photoperiod and temperature. Dehardening was temporarily delayed by photoperiods below about 10 h, but there was no other quantitative effect of photoperiod. At constant temperatures, the rate of dehardening was initially constant but declined as the minimum summer frost hardiness was reached. In the initial phase the rate of dehardening was a linear function of temperature, increasing from 0.05°C day−1 at 8°C to 0.30 °C day−1 at 17°C. Temperature controlled the loss of frost hardiness by regulating the rate of dehardening. 相似文献
94.
Summary Highly sensitive and specific synthetic substrates were used to quantitate cathepsin B and D activity in peritoneal macrophages in response to stimulation in vivo with mineral oil and thioglycollate. After intraperitoneal instillation of mineral oil the activity of cathepsin B increased significantly (to 15 300 units/mg protein versus 7 340 in saline controls), reaching values approaching those found in alveolar macrophages (18 400 units/mg protein). Significantly greater stimulation of enzyme activity was obtained after intraperitoneal instillation of thioglycollate (23 600 units/mg protein). Cathepsin D activity also increased significantly after both mineral oil and thioglycollate. However, the increase was moderate (from 806 to about 1 200 units/mg protein), remaining still more than six times lower-than in alveolar macrophages. The data are the first to demonstrate that cathepsin B activity can be stimulated in vivo in peritoneal macrophages by instillation of agents that induce acute inflammation. They also point to a differential control of expression of cathepsin B and D activity in both peritoneal and alveolar macrophages in spite of the common lysosomal origin of the two enzymes.Abbreviations Cbz
-N-benxyloxycarbonyl
- 2NA
2-naphthylamine
- EDTA
ethylenediamine tetraacetate
- DMSO
dimethylsulfoxide
- PBS
phosphate-buffered saline
- PM
peritoneal macrophage
- AM
alveolar macrophage 相似文献
95.
96.
从大萼香茶菜叶中又分得一个具有细胞毒活性的新的二萜类化合物,命名为大萼香茶菜丁素(macrocalyxin D)。根据光谱和化学数据鉴定其化学结构为[3]。 相似文献
97.
T Ikehara H Yamaguchi K Hosokawa M Kaku H Miyamoto 《Journal of cellular biochemistry》1985,28(4):273-280
phenazine methosulfate (PMS) stimulates ouabain-sensitive Rb+ uptake by HeLa cells. This stimulation cannot be attributed to the effect of the dye on the intracellular Na+ or ATP content. Respiratory inhibitors, such as 5 mM NaCN and 5 microM rotenone, and anaerobic conditions enhance the stimulation of Rb+ uptake by PMS. Cellular respiration is stimulated, but lactate production is reduced in the presence of PMS, irrespective of the presence of respiratory inhibitors. Cellular NADH is oxidized markedly on addition of PMS plus inhibitors, but it is not affected by addition of the inhibitors only. In the presence of a high concentration of PMS, PMS-stimulated ouabain-sensitive Rb+ uptake is inhibited by addition of ascorbate. From these results it is concluded that Na+K-pump activity is closely related to the cellular redox state. 相似文献
98.
99.
Teresa de Sa E Melo Patrice Morlière Sonia Goldstein René Santus Louis Dubertret Dominique Lagrange 《Biochemical and biophysical research communications》1984,120(2):670-676
5-methoxypsoralen (5-MOP) binds to human serum low density lipoproteins (LDL) according to a two-step process. Scatchard analysis of the first step yields K = 1.4 × 105 M?1 and 4 binding sites. It involves the LDL apoprotein. The second step corresponds to a solubilization, in the lipidic core, of ? 45 molecules of 5MOP per LDL molecule. It is accompanied by a large blue shift of the 5MOP fluorescence. The ability of LDL to bind 5MOP and to carry it into various cells may explain some biological effects sometimes encountered during PUVA therapy. 相似文献
100.