全文获取类型
收费全文 | 11567篇 |
免费 | 1059篇 |
国内免费 | 3篇 |
出版年
2023年 | 75篇 |
2022年 | 126篇 |
2021年 | 364篇 |
2020年 | 174篇 |
2019年 | 220篇 |
2018年 | 301篇 |
2017年 | 252篇 |
2016年 | 418篇 |
2015年 | 674篇 |
2014年 | 702篇 |
2013年 | 867篇 |
2012年 | 985篇 |
2011年 | 1040篇 |
2010年 | 629篇 |
2009年 | 484篇 |
2008年 | 735篇 |
2007年 | 724篇 |
2006年 | 601篇 |
2005年 | 539篇 |
2004年 | 510篇 |
2003年 | 406篇 |
2002年 | 385篇 |
2001年 | 108篇 |
2000年 | 98篇 |
1999年 | 96篇 |
1998年 | 83篇 |
1997年 | 58篇 |
1996年 | 57篇 |
1995年 | 69篇 |
1994年 | 55篇 |
1993年 | 44篇 |
1992年 | 43篇 |
1991年 | 47篇 |
1990年 | 50篇 |
1989年 | 38篇 |
1988年 | 38篇 |
1987年 | 34篇 |
1986年 | 32篇 |
1985年 | 28篇 |
1984年 | 44篇 |
1983年 | 27篇 |
1982年 | 19篇 |
1981年 | 25篇 |
1980年 | 18篇 |
1978年 | 26篇 |
1977年 | 22篇 |
1976年 | 18篇 |
1975年 | 24篇 |
1974年 | 18篇 |
1973年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
111.
112.
Gracjana Klein Robert Walczak Ewa Krasnowska Adam Blaszczak Barbara Lipiska 《Molecular microbiology》1995,16(4):801-811
We have investigated heat-shock response in a marine bacterium Vibrio harveyi. We have found that 39 C was the highest tempature at which V. harveyi was able to grow steadily. A shift from 30° C to 39° C caused increased synthesis of at least 10 proteins, as judged by SDS-PAGE, with molecular masses of 90, 70, 58, 41, 31, 27, 22, 15, 14.5 and 14kDa. The 70, 58, 41 and 14.5 kDa proteins were immunologically homologous to DnaK, GroEL, DnaJ and GroES heat-shock proteins of Escherichia coli, respectively. V. harveyi GroES protein had a lower molecular mass (14.5 kDa) than E. coli GroES, migrating in SDS-PAGE as 15 kDa protein. We showed that a protein of ~43 kDa, immunologically reactive with antiserum against E. coli sigma 32 subunit (σ32) of RNA polymerase, was induced by heat-shock and co-purified with V. harveyi RNA polymerase. These results suggest that the 43 kDa protein is a heat-shock sigma protein of V. harveyi. Preparation containing the V. harveyi sigma 32 homologue, supplemented with core RNA polymerase of E. coli, was able to transcribe heat-shock promoters of E. coli in vitro. 相似文献
113.
114.
115.
Cross-correlation histograms (CCH) were computed for discharge sequences of pairs of motoneurones which were excited by sinusoidal muscle stretches. These CCH's were compared before and after opening of the recurrent inhibitory loop by Renshaw cell blocking agents. Periodic patterns in the CCH's indicative of specifically timed phase relations between discharges of different motoneurones were enhanced after Renshaw cell blockage. This was confirmed by power spectra computed for the CCH's. They contained power peaks about 50Hz which tended to increase after depression of recurrent inhibition. The correlation was thus due predominantly to line current interference which seemed to act as a common entrainment input at the spinal level. It is concluded that Renshaw cells de-correlate discharge patterns of different motoneurones of the same pool by injecting uncorrelated signals into them. This de-correlation is an important prerequisite for distortion suppression of signal transmission in a multi-channel system, like that of stretch reflex, and for its linearization. 相似文献
116.
In order to determine the significance of the C-6 carboxyl group for the biological activity gibberellin A3, 6-epigibberellin A3, 7-norgibberellin A3, 6-methyl-7-norgibberellin A3, and 7-homogibberellin A3 were studied using dwarf pea, dwarf maize, dwarf rice, dwarf barley and -amylase bioassays. All gibberellin A3(GA3)derivatives tested were considerably less active than GA3. In all biossays, 6-epi-GA3 showed a low activity of the same order, whereas 6-methyl-7-nor-GA3 was inactive. Surprisingly, 7-nor-GA3 had some activity in the dwarf rice (root application), dwarf barley, and -amylase bioassay, in contrary to its low potency in the dwarf pea, dwarf maize, and dwarf rice (micro drop) bioassay. 7-Homo-GA3 was primarily active in the dwarf maize, dwarf barley and dwarf rice bioassay. It also caused antigibberellin effects in dwarf rice. The results demonstrate that the C-6 carboxyl group is not absolutely essential for biological activity of gibberellins. The different activities of 7-nor-GA3 observed in the various test systems may indicate that the C-6 carboxyl group is a structural requirement more for uptake and/or transport processes than for receptor affinity.Abbreviation GA3
gibberellic acid 相似文献
117.
High biological activity of the synthetic replicates of somatostatin-28 and somatostatin-25 总被引:4,自引:0,他引:4
Paul Brazeau Nicholas Ling Frederick Esch Peter Böhlen Robert Benoit Roger Guillemin 《Regulatory peptides》1981,1(4):255-264
We have isolated form extracts of ovine hypothalami two molecules characterized as somatostatin-28 and somatostatin-4-28 (referred to as somatostatin-25). They were reproduced by solid hase synthesis. In equimolar ratio and depending upon the experimental conditions, synthetic somatostatin-28 ans somatostatin-25 are 3-14 times more potent than somatostatin-14 to inhibit the basal in vitro secretion of growth hormone or as stimulated by prostaglandin (PGE2). In early studies in vivo, somatostatin-28 and somatostatin-25 are also more potent than somatostatin-14 in inhibiting the secretion of growth hormone acutely stimulated in the rat by injection of morphine; somatostatin-28 is also longer-acting than somatostatin-14. These results suggest that somatostatin-14, as originally isolated, is a biologically active fragment of a larger molecule of greater specific activity; it should be considered as another form of somatostatin with high biological activity present in some tissues and likely secreted y the tissues along with somatostatin-14 and possibly other somatostatin-peptides of diverse sizes. 相似文献
118.
119.
120.