全文获取类型
收费全文 | 3011篇 |
免费 | 178篇 |
国内免费 | 75篇 |
专业分类
3264篇 |
出版年
2023年 | 7篇 |
2022年 | 40篇 |
2021年 | 63篇 |
2020年 | 15篇 |
2018年 | 36篇 |
2017年 | 30篇 |
2016年 | 92篇 |
2015年 | 217篇 |
2014年 | 225篇 |
2013年 | 259篇 |
2012年 | 269篇 |
2011年 | 251篇 |
2010年 | 173篇 |
2009年 | 110篇 |
2008年 | 122篇 |
2007年 | 90篇 |
2006年 | 57篇 |
2005年 | 122篇 |
2004年 | 130篇 |
2003年 | 111篇 |
2002年 | 77篇 |
2001年 | 83篇 |
2000年 | 47篇 |
1999年 | 31篇 |
1998年 | 21篇 |
1997年 | 22篇 |
1996年 | 24篇 |
1995年 | 9篇 |
1994年 | 11篇 |
1993年 | 36篇 |
1992年 | 36篇 |
1991年 | 21篇 |
1990年 | 18篇 |
1989年 | 33篇 |
1988年 | 22篇 |
1987年 | 21篇 |
1986年 | 18篇 |
1985年 | 33篇 |
1984年 | 11篇 |
1983年 | 11篇 |
1982年 | 11篇 |
1973年 | 11篇 |
1972年 | 7篇 |
1968年 | 7篇 |
1957年 | 8篇 |
1955年 | 7篇 |
1954年 | 7篇 |
1951年 | 7篇 |
1933年 | 6篇 |
1926年 | 7篇 |
排序方式: 共有3264条查询结果,搜索用时 0 毫秒
1.
State of aggregation of the (Ca2+ + Mg2+)-ATPase studied using saturation-transfer electron spin resonance 总被引:1,自引:0,他引:1
The state of aggregation of the (Ca2+ + Mg2+)-ATPase in the membrane of sarcoplasmic reticulum and in reconstituted membrane systems has been studied using saturation-transfer electron spin resonance (ST-ESR). Saturation-transfer ESR spectra show that in the sarcoplasmic reticulum, the ATPase is relatively free to rotate, with an effective rotational correlation time of approx. 33 microseconds at 4 degrees C, consistent with a monomeric or dimeric structure. The rate of rotation is observed to decrease with decreasing molar ratio of lipid to protein. In reconstituted systems, rotational motion of the ATPase on the millisecond time scale ceases when the lipids are in the gel phase. Addition of decavanadate, which causes the formation of crystalline arrays in negatively stained electron micrographs, results in only a small reduction in rotation rate for the ATPase in the membrane. The experiments are interpreted in terms of a short-lived (on the millisecond time scale) protein-protein interaction, with the formation of crystalline clusters of ATPase molecules which form and melt rapidly. 相似文献
2.
3.
4.
We have developed a procedure for the reconstitution of Escherichia coli diacylglycerol kinase (DGK) into phospholipid bilayers containing diacylglycerol substrate. When DGK is reconstituted into a series of phosphatidylcholines containing monounsaturated fatty acyl chains, activity against dihexanoylglycerol (DHG) as a substrate was found to be markedly dependent on the fatty acyl chain length with the highest activity in dioleoylphosphatidylcholine [di(C18:1)PC] and a lower activity in bilayers with shorter or longer fatty acyl chains. Low activities in the short chain phospholipid dimyristoleoylphosphatidylcholine [di(C14:1)PC] followed from an increase in the K(m) value for DHG and ATP, with no effect on v(max). In contrast, in the long chain lipid dierucoylphosphatidylcholine [di(C24:1)PC], the low activity followed from a decrease in v(max) with no effect on K(m). In mixtures of two phosphatidylcholines with different chain lengths, the activity corresponded to that expected for the average chain length of the mixture. Cholesterol increased the activity in di(C14:1)PC but slightly decreased it in di(C18:1)PC or di(C24:1)PC, effects that could follow from changes in bilayer thickness caused by cholesterol. 相似文献
5.
6.
7.
W Quinkler M Maasberg S Bernotat-Danielowski N Lüthe H S Sharma W Schaper 《European journal of biochemistry》1989,181(1):67-73
Fresh bovine, porcine and canine hearts were homogenized and mitogens for mesoderm-derived cells were purified in three different steps. Extraction by two different ammonium sulfate precipitations was followed by cation-exchange chromatography and by heparin-Sepharose affinity chromatography. A heparin-Sepharose fraction from heart (eluted at 1.1 M NaCl) increased mitotic activity in serum-deprived cultures of porcine aortic endothelial and smooth muscle cells, and in human fibroblasts. This mitogenic activity is potentiated by heparin and inhibited by gamma-interferon. The heart mitogenic fraction showed one double peak on HPLC at A215 and one polypeptide band on SDS/PAGE. These peaks and bands were identical to those obtained from bovine brain. The heart acidic fibroblast growth factor (aFGF) showed a positive signal in Western blots using antibodies raised against brain aFGF. Gas-phase amino acid sequencing established that the mitogens were identical to aFGF and the N-terminally truncated aFGF. Extraction in the presence of a protease inhibitor (pepstatin A) produced a higher-molecular mass form of aFGF with a blocked amino terminus. Another mitogen, eluted at 1.6 M NaCl from heparin-Sepharose, reacted with polyclonal antiserum against human recombinant basic fibroblast growth factor (bFGF) and showed a 66% (12 from 18 amino acids determined by gas-phase sequencing) similarity with bFGF. This polypeptide increased the mitotic activity of the same cell lines but was more potent than aFGF. 相似文献
8.
E.K. Rooney J.M. East O.T. Jones J. McWhirter A.C. Simmonds A.G. Lee 《生物化学与生物物理学报:生物膜》1983,728(2):159-170
We present a method by which it is possible to describe the binding of fatty acids to phospholipid bilayers. Binding constants for oleic acid and a number of fatty acids used as spectroscopic probes are deduced from electrophoresis measurements. There is a large shift in value for the fatty acids on binding to the phospholipid bilayers, consistent with stronger binding of the uncharged form of the fatty acid. For dansylundecanoic acid, fluorescence titrations are consistent with the binding constants derived from the electrophoresis experiments. For 12-(9-anthroyloxy)stearic acid, fluorescence and electrophoresis data are inconsistent, and we attribute this to quenching of fluorescence at high molar ratios of 12-anthroylstearic acid to phospholipid in the bilayer. 相似文献
9.
10.
寻螨属Zetzellia在中国曾报道了两种:苹果寻螨Z.mail(Ewing)和北京寻螨Z.beijing Wang and Xu1987.本文描述了寻螨属一新种,庐山寻螨Z.lushanensis sp.nov.模式标本保存于江西大学生物系.文内测量单位为μm。 相似文献