全文获取类型
收费全文 | 321129篇 |
免费 | 26771篇 |
国内免费 | 263篇 |
专业分类
348163篇 |
出版年
2021年 | 2719篇 |
2018年 | 4707篇 |
2017年 | 4421篇 |
2016年 | 5888篇 |
2015年 | 6905篇 |
2014年 | 7930篇 |
2013年 | 10963篇 |
2012年 | 12349篇 |
2011年 | 12409篇 |
2010年 | 8345篇 |
2009年 | 6964篇 |
2008年 | 10506篇 |
2007年 | 10497篇 |
2006年 | 10135篇 |
2005年 | 9253篇 |
2004年 | 9136篇 |
2003年 | 8688篇 |
2002年 | 8311篇 |
2001年 | 13845篇 |
2000年 | 13689篇 |
1999年 | 10457篇 |
1998年 | 3268篇 |
1997年 | 3161篇 |
1996年 | 3172篇 |
1995年 | 2900篇 |
1994年 | 2823篇 |
1992年 | 8026篇 |
1991年 | 7738篇 |
1990年 | 7804篇 |
1989年 | 7670篇 |
1988年 | 7028篇 |
1987年 | 6702篇 |
1986年 | 5997篇 |
1985年 | 6372篇 |
1984年 | 5044篇 |
1983年 | 4362篇 |
1982年 | 3102篇 |
1981年 | 2884篇 |
1979年 | 4735篇 |
1978年 | 3583篇 |
1977年 | 3351篇 |
1976年 | 3234篇 |
1975年 | 3813篇 |
1974年 | 4090篇 |
1973年 | 4086篇 |
1972年 | 3581篇 |
1971年 | 3310篇 |
1970年 | 3037篇 |
1969年 | 2893篇 |
1968年 | 2787篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
S Sayama R V Iozzo G S Lazarus N M Schechter 《The Journal of biological chemistry》1987,262(14):6808-6815
The subcellular localization of human skin chymase to mast cell granules was established by immunoelectron microscopy, and binding of chymase to the area of the dermo-epidermal junction, a basement membrane, was demonstrated immunocytochemically in cryosections incubated with purified proteinase prior to immunolabeling. Because heparin and heparan sulfate proteoglycans are major constituents of mast cell granules and basement membranes, respectively, the ability of chymase to bind to glycosaminoglycans (GAG) was investigated. Among a variety of GAGs, only binding of chymase to heparin and heparan sulfate appears physiologically significant. Binding was ionic strength-dependent, involved amino groups on the proteinase, and correlated with increasing GAG sulfate content, indicating a predominantly electrostatic association. Interaction with heparin was observed in solutions containing up to 0.5 M NaCl, and interaction with heparan sulfate was observed in solutions containing up to 0.3 M NaCl. Binding of heparin did not detectably affect catalysis of peptide substrates, but may reduce accessibility of proteinase to protein substrates. Measurements among a series of serine class proteinases indicated that heparin binding was a more common property of mast cell proteinases than proteinases stored in other secretory granules. Binding of chymase to heparin is likely to have a storage as well as a structural role within the mast cell granule, whereas binding of chymase to heparan sulfate may have physiological significance after degranulation. 相似文献
92.
93.
Comparative tissue ascorbic acid studies in fishes 总被引:1,自引:0,他引:1
Comparative tissue ascorbic acid levels in four species of major carp viz., Labeo rohila, L. calbasu, Cirrhina tnrigala and Catla catla , were investigated. The ascorbic acid level was found to be the highest in the spleen in the four species studied (range 430–380 μg/g) followed by the anterior (adrenal) kidney, gonads, liver, renal kidney, brain and/or eye. Heart and blood had the lowest levels (range 26–18 μg/ml) amongst the tissues studied. Overall tissue ascorbic acid levels were the highest in L. rohita and the lowest in C. mrigala . Investigation on seasonal variations in blood and kidney ascorbic acid levels of Notopterus notopterus revealed peak levels in spring (February-April) and the lowest levels in the postspawning period (August-September). 相似文献
94.
E. Molina Grima J. A. Sánchez Pérez F. García Camacho F. G. Acién Fernández J. M. Fernández Sevilla F. Valdés Sanz 《Biotechnology letters》1994,16(10):1035-1040
Summary Eicosapentaenoic acid (EPA) volumetric productivity from an outdoor chemostat culture ofPhaeodactylum tricornutum UTEX 640 in a 50-l tubular photobioreactor varies with dilution rate, reaching a maximum of 47.8 mg l–1 d–1 at D=0.36 d–1. Continuous culture at high dilution rates' is proposed as the most adequate operating mode to maximize polyunsaturated fatty acid production. 相似文献
95.
96.
97.
Ia I Serkiz A I Lipskaia L B Pinchuk V V Trishin Iu F Kataevski? G N Koval' 《Radiobiologiia》1991,31(5):629-634
Irradiation conditions in which laboratory animals were kept in experimental laboratories of Chernobyl and Kiev after the accident at the Chernobyl A.P.S. are described. The data are presented on the spectral structural and activity of radionuclides in the diet as well as in the organs and tissues of the animals. The radiation loads have been estimated with regard to an external gamma component and the internal one contributed by the incorporated radionuclides. It has been shown that radiation doses received by the animals during their lifetime due to these contributions do not exceed units of cGy. 相似文献
98.
99.
100.
N B Terenina 《Parazitologiia》1988,22(6):476-480
Identification of serotonin and dopamine in M. salmonis was conducted by means of some fluorometric methods. The presence of negligible amount of a serotonin-like component and substance close in its spectral characteristics to dopamine was shown. 相似文献