全文获取类型
收费全文 | 2047篇 |
免费 | 152篇 |
国内免费 | 1篇 |
出版年
2021年 | 22篇 |
2020年 | 13篇 |
2019年 | 27篇 |
2018年 | 18篇 |
2016年 | 41篇 |
2015年 | 43篇 |
2014年 | 73篇 |
2013年 | 90篇 |
2012年 | 102篇 |
2011年 | 100篇 |
2010年 | 63篇 |
2009年 | 66篇 |
2008年 | 84篇 |
2007年 | 70篇 |
2006年 | 72篇 |
2005年 | 69篇 |
2004年 | 82篇 |
2003年 | 75篇 |
2002年 | 80篇 |
2001年 | 50篇 |
2000年 | 59篇 |
1999年 | 45篇 |
1998年 | 19篇 |
1997年 | 24篇 |
1996年 | 14篇 |
1995年 | 15篇 |
1994年 | 18篇 |
1993年 | 17篇 |
1992年 | 35篇 |
1991年 | 29篇 |
1990年 | 19篇 |
1989年 | 27篇 |
1988年 | 17篇 |
1987年 | 16篇 |
1986年 | 24篇 |
1985年 | 21篇 |
1984年 | 22篇 |
1982年 | 14篇 |
1979年 | 26篇 |
1978年 | 18篇 |
1977年 | 19篇 |
1976年 | 13篇 |
1975年 | 23篇 |
1974年 | 17篇 |
1973年 | 25篇 |
1972年 | 19篇 |
1971年 | 24篇 |
1970年 | 29篇 |
1968年 | 13篇 |
1967年 | 21篇 |
排序方式: 共有2200条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
6.
Extracellular ATP and adenosine modulate tumor necrosis factor-induced lysis of L929 cells in the presence of actinomycin D 总被引:1,自引:0,他引:1
Extracellular ATP in concentrations of 0.5 to 2.5 mM modulates TNF-induced cytolysis of L929 cells in the presence of actinomycin D. When present throughout the entire assay period, it inhibits the TNF-induced cytolysis. ADP was less active whereas AMP and GTP were nonreactive. However, inhibition was also achieved by adenosine that was nearly as active as ATP. Yet, the inhibitory effect of ATP was not due to hydrolysis by ectoenzymes to form adenosine. Thus, the nonhydrolyzable ATP analogue adenyl(beta-gamma-methylendiphosphate) was equally effective in inhibiting TNF-induced cytolysis. Moreover, no conversion of ATP into adenosine was observed during the entire assay period. However, inhibition no longer occurred when the TNF and ATP containing medium was removed after 5 h and replaced by a fresh medium containing TNF and no ATP. We now observed substantial enhancement of the TNF-induced cytolysis by ATP. Finally, treatment with N6-(R-phenylisopropyl)adenosine or with aminophylline, which are thought to downregulate adenosine receptors and to prevent binding of ligands to adenosine receptors, respectively, abolishes adenosine and ATP-mediated inhibition. Again, substantial enhancement of the TNF-induced cytolysis was observed by ATP and only a minor effect by adenosine. The results together suggest that ATP interacts with purinoceptors on the plasma membrane and is capable to enhance and inhibit TNF-induced cytolysis under appropriate conditions. The outcome of the ATP-induced modulation may be influenced by adenosine receptors. 相似文献
7.
E Weidekamm E Bamberg D Brdiczka G Wildermuth F Macco W Lehmann R Weber 《Biochimica et biophysica acta》1977,464(2):442-447
The interaction of gramicidin A with dipalmitoyl phosphatidylcholine liposomes is investigated by Laser-Raman spectroscopy. As revealed by the methylene C-H stretching mode the phase transition of the hydrocarbon chains near 40 degree C is eliminated in the presence of gramicidin A. Liposomes prepared from a mixture of lecithin and cholesterol seem to be unaffected by gramicidin A and show only the normal broadened phase transition. 相似文献
8.
9.
10.
Solid-phase synthesis of oligoribonucleotides using 9-fluorenylmethoxycarbonyl (Fmoc) for 5''-hydroxyl protection. 总被引:7,自引:6,他引:1 下载免费PDF全文
Efficient solid-phase synthesis of a series of oligoribonucleotides of up to 20 residues is described that utilises the 9-fluorenylmethoxycarbonyl group (Fmoc) for 5'-protection and 4-methoxytetrahydropyran-4-yl (Mthp) for 2'-protection of ribonucleotide monomers and a phosphoramidite coupling procedure. The Fmoc group is removed after each coupling step by treatment with 0.1M DBU in acetonitrile. Oligoribonucleotides are isolated in 2'-protected form in good yield and shown to be readily and efficiently deprotected by mild acidic treatment. 相似文献