全文获取类型
收费全文 | 802682篇 |
免费 | 81543篇 |
国内免费 | 363篇 |
出版年
2018年 | 8393篇 |
2017年 | 8131篇 |
2016年 | 12167篇 |
2015年 | 17968篇 |
2014年 | 19577篇 |
2013年 | 25937篇 |
2012年 | 28724篇 |
2011年 | 26797篇 |
2010年 | 18117篇 |
2009年 | 16400篇 |
2008年 | 22699篇 |
2007年 | 22995篇 |
2006年 | 22045篇 |
2005年 | 26101篇 |
2004年 | 24513篇 |
2003年 | 22315篇 |
2002年 | 19477篇 |
2001年 | 34830篇 |
2000年 | 34677篇 |
1999年 | 28202篇 |
1998年 | 9424篇 |
1997年 | 9734篇 |
1996年 | 9102篇 |
1995年 | 8411篇 |
1994年 | 8473篇 |
1993年 | 8359篇 |
1992年 | 23507篇 |
1991年 | 22914篇 |
1990年 | 22356篇 |
1989年 | 22109篇 |
1988年 | 20417篇 |
1987年 | 19206篇 |
1986年 | 17768篇 |
1985年 | 17849篇 |
1984年 | 14134篇 |
1983年 | 12259篇 |
1982年 | 9046篇 |
1981年 | 8076篇 |
1980年 | 7675篇 |
1979年 | 13539篇 |
1978年 | 10430篇 |
1977年 | 9380篇 |
1976年 | 8751篇 |
1975年 | 9808篇 |
1974年 | 10396篇 |
1973年 | 10266篇 |
1972年 | 9226篇 |
1971年 | 8384篇 |
1970年 | 7475篇 |
1969年 | 7097篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
53.
54.
55.
T. B. Lapirova V. R. Mikryakova A. S. Mavrin G. A. Yinogradova 《Journal of Evolutionary Biochemistry and Physiology》2000,36(1):47-51
The paper presents data on a change in lysozyme content in tissues of spleen, liver and heart in fry of the Lena River sturgeon
exposed to the presence of sublethal concentrations of Hg2+, Cd2+, and Cu2+ under conditions of chronic experiment. It has been shown that the lysozyme content in fish tissues varies and has a phasic
character. The amplitude of fluctuations of this parameter depends on the moment of sampling, nature of the toxicant, and
structural-functional organization of the studied organs. 相似文献
56.
Staphylococcal gamma-hemolysin and leukocidin are bi-component cytolysins, consisting of LukF (or Hlg1)/Hlg2 and LukF/LukS, respectively. Here, we purified serum inhibitors of gamma-hemolysin and leukocidin from human plasma. Protein sequencing showed that the purified inhibitors of 62, 57, 50 and 38 kDa were the vitronectin fragments with truncation(s) of the C-terminal or both N- and C-terminal regions. The purified vitronectin fragments specifically bound to the Hlg2 component of gamma-hemolysin and the LukS component of leukocidin to form high-molecular-weight complexes with them, leading to inhibition of the toxin-induced lysis of human erythrocytes and human polymorphonuclear leukocytes, respectively. Intact vitronectin also showed inhibitory activity to the toxins. The ability of gamma-hemolysin and leukocidin to bind vitronectin and its fragments is a novel function of the pore-forming cytolysins. 相似文献
57.
58.
(Z)- and (E)-4-amino-2-(trifluoromethyl)-2-butenoic acid (4 and 5, respectively) were synthesized and investigated as potential mechanism-based inactivators of gamma-aminobutyric acid aminotransferase (GABA-AT) in a continuing effort to map the active site of this enzyme. The core alpha-trifluoromethyl-alpha,beta-unsaturated ester moiety was prepared via a Reformatsky/reductive elimination coupling of the key intermediates tert-butyl 2,2-dichloro-3,3,3-trifluoropropionate and N,N-bis(tert-butoxy-carbonyl)glycinal. Both 4 and 5 inhibited GABA-AT in a time-dependent manner, but displayed non-pseudo-first-order inactivation kinetics; initially, the inactivation rate increased with time. Further investigation demonstrated that the actual inactivator is generated enzymatically from 4 or 5. This inactivating species is released from the active site prior to inactivation, and as a result, 4 and 5 cannot be defined as mechanism-based inactivators. Furthermore, 4 and 5 are alternate substrates for GABA-AT, transaminated by the enzyme with Km values of 0.74 and 20.5 mM, respectively. Transamination occurs approximately 276 and 305 times per inactivation event for 4 and 5, respectively. The enzyme also catalyzes the elimination of the fluoride ion from 4 and 5. A mechanism to account for these observations is proposed. 相似文献
59.
60.