全文获取类型
收费全文 | 48009篇 |
免费 | 4589篇 |
国内免费 | 33篇 |
出版年
2021年 | 642篇 |
2020年 | 365篇 |
2019年 | 450篇 |
2018年 | 600篇 |
2017年 | 545篇 |
2016年 | 985篇 |
2015年 | 1691篇 |
2014年 | 1861篇 |
2013年 | 2347篇 |
2012年 | 2924篇 |
2011年 | 3005篇 |
2010年 | 1959篇 |
2009年 | 1873篇 |
2008年 | 2762篇 |
2007年 | 2764篇 |
2006年 | 2677篇 |
2005年 | 2644篇 |
2004年 | 2569篇 |
2003年 | 2523篇 |
2002年 | 2491篇 |
2001年 | 612篇 |
2000年 | 530篇 |
1999年 | 680篇 |
1998年 | 729篇 |
1997年 | 524篇 |
1996年 | 483篇 |
1995年 | 463篇 |
1994年 | 443篇 |
1993年 | 445篇 |
1992年 | 417篇 |
1991年 | 393篇 |
1990年 | 419篇 |
1989年 | 338篇 |
1988年 | 370篇 |
1987年 | 359篇 |
1986年 | 338篇 |
1985年 | 414篇 |
1984年 | 437篇 |
1983年 | 387篇 |
1982年 | 482篇 |
1981年 | 476篇 |
1980年 | 441篇 |
1979年 | 322篇 |
1978年 | 348篇 |
1977年 | 308篇 |
1976年 | 318篇 |
1975年 | 266篇 |
1974年 | 317篇 |
1973年 | 305篇 |
1972年 | 223篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
71.
Sandra Danner Christiane Kirchhoff Richard Ivell 《Reproductive biology and endocrinology : RB&E》2009,7(1):67-14
Background
Post-meiotically expressed genes in the testis are essential for the proper progression of spermatogenesis, and yet, aside from the construction of individual transgenic mice using specific promoters to drive reporter plasmids, there are only very limited possibilities for relevant and quantitative analysis of gene promoters. This is due to the special nature of post-meiotic haploid cells, which to date are not represented in any appropriate cell-lines. This article reports the development of novel methodology using isolated and cultured rat seminiferous tubules in a multiwell format, into which promoter-reporter constructs can be introduced by a combination of microinjection and electroporation. 相似文献72.
An olfactometer is described that presents temporally-discretepulses of stimuli to individual chemosensory structures. Thedevice is based on standard pressure injection techniques inwhich pulses of compressed air eject nanoliter volumes of upto six stimulants from small diameter glass micropipettes. Thedevice should be readily adaptable to different chemoreceptorpreparations. 相似文献
73.
74.
Richard Barwel 《BMJ (Clinical research ed.)》1882,2(1130):362-364
75.
76.
Alicia P. Higueruelo Adrian Schreyer G. Richard J Bickerton Tom L. Blundell Will R. Pitt 《PloS one》2012,7(12)
Efforts to increase affinity in the design of new therapeutic molecules have tended to lead to greater lipophilicity, a factor that is generally agreed to be contributing to the low success rate of new drug candidates. Our aim is to provide a structural perspective to the study of lipophilic efficiency and to compare molecular interactions created over evolutionary time with those designed by humans. We show that natural complexes typically engage in more polar contacts than synthetic molecules bound to proteins. The synthetic molecules also have a higher proportion of unmatched heteroatoms at the interface than the natural sets. These observations suggest that there are lessons to be learnt from Nature, which could help us to improve the characteristics of man-made molecules. In particular, it is possible to increase the density of polar contacts without increasing lipophilicity and this is best achieved early in discovery while molecules remain relatively small. 相似文献
77.
78.
79.
80.