全文获取类型
收费全文 | 131550篇 |
免费 | 4400篇 |
国内免费 | 821篇 |
出版年
2022年 | 309篇 |
2021年 | 670篇 |
2020年 | 486篇 |
2019年 | 567篇 |
2018年 | 12365篇 |
2017年 | 11164篇 |
2016年 | 8389篇 |
2015年 | 2301篇 |
2014年 | 2149篇 |
2013年 | 2606篇 |
2012年 | 6999篇 |
2011年 | 15435篇 |
2010年 | 13640篇 |
2009年 | 9721篇 |
2008年 | 11826篇 |
2007年 | 13383篇 |
2006年 | 2364篇 |
2005年 | 2384篇 |
2004年 | 2832篇 |
2003年 | 2679篇 |
2002年 | 2410篇 |
2001年 | 901篇 |
2000年 | 761篇 |
1999年 | 643篇 |
1998年 | 439篇 |
1997年 | 373篇 |
1996年 | 348篇 |
1995年 | 350篇 |
1994年 | 314篇 |
1993年 | 334篇 |
1992年 | 434篇 |
1991年 | 392篇 |
1990年 | 357篇 |
1989年 | 370篇 |
1988年 | 381篇 |
1987年 | 347篇 |
1986年 | 268篇 |
1985年 | 298篇 |
1984年 | 310篇 |
1983年 | 286篇 |
1982年 | 259篇 |
1981年 | 231篇 |
1980年 | 210篇 |
1979年 | 215篇 |
1978年 | 181篇 |
1977年 | 183篇 |
1976年 | 182篇 |
1975年 | 203篇 |
1972年 | 386篇 |
1971年 | 398篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
781.
Caroline D. Perkins A.Michael Davidson Martin J. Day John C. Fry 《FEMS microbiology ecology》1994,15(1-2):33-44
Abstract The kinetics of conjugation, retrotransfer and mobilisation were studied at 5–15 min intervals between strains of Pseudomonas putida using plasmid pQKH6, isolated from river epilithon, and R300B. Transconjugants from the direct conjugation of pQKH6 and mobilisation of R300B by pQKH6 appeared rapidly, reaching maximum densities within 30–60 min of the start of both filter and liquid mating experiments. However, retrotransconjugants only appeared after a delay. This delay was short (approx. 45–60 min) in filter mating and much longer (2–5 h) for liquid mating experiments. Attempts at predicting the time course of retrotransconjugant development from (1) numbers of transconjugants from the conjugation and mobilisation experiments and (ii) mathematical models based on a mass action approach, both failed to reproduce the observed delay. It was concluded that retrotransfer did not proceed by either a one-step mechanism occuring early in conjugation or two separate conjugation and mobilisation steps. The clear demonstration of a delay in retrotransconjugant formation implies that a new mechanism must be sought. The likely importance of retrotransfer in the environment is discussed. 相似文献
782.
783.
A Mef2 gene that generates a muscle-specific isoform via alternative mRNA splicing. 总被引:26,自引:11,他引:15
下载免费PDF全文
![点击此处可从《Molecular and cellular biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
J F Martin J M Miano C M Hustad N G Copeland N A Jenkins E N Olson 《Molecular and cellular biology》1994,14(3):1647-1656
784.
785.
J M Flaman T Frebourg V Moreau F Charbonnier C Martin C Ishioka S H Friend R Iggo 《Nucleic acids research》1994,22(15):3259-3260
786.
787.
Tova Rahn Martin Ridderstrle Hans Tornqvist Vincent Manganiello Gudrun Fredrikson Per Belfrage Eva Degerman 《FEBS letters》1994,350(2-3):314-318
Incubation of rat adipocytes with wortmannin, a potent and selective phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor, completely blocked the antilipolytic action of insulin (IC50≈ 100 nM), the insulin-induced activation and phosphorylation of cGMP-inhibited cAMP phosphodiesterase (cGI-PDE) as well as the activation of the insulin-stimulated cGI-PDE kinase (IC50≈ 10–30 nM). No direct effects of the inhibitor on the insulin-stimulated cGI-PDE kinase, the cGI-PDE and the hormone-sensitive lipase were observed. These data suggest that activation of PI 3-kinase upstream of the insulin-stimulated cGI-PDE kinase in the antilipolytic insulin signalchain has an essential role for insulin-induced cGI-PDE activation/ phosphorylation and anti-lipolysis. 相似文献
788.
The effect of algae on the production of musty-smelling compounds by actinomycetes was studied. Streptomyces spp., causing intensive musty odor, were isolated from hypertrophic Lake Kasumigaura and cultured in association with algae from the same lake. Isolate E and I effectively utilized the cyanobacteria, Microcystis aeruginosa and Anabaena spiroides, and the diatom, Synedra acus, as a carbon source and produced a musty-smelling 2-methylisoborneol in the shaken sediment cultures. High populations of algae and actinomycetes, and aerobic condition in the sediment seem responsible for the occurrence of musty odor in Lake Kasumigaura. 相似文献
789.
Martin T. Dokulil 《Hydrobiologia》1994,289(1-3):65-72
Factors affecting phytoplankton productivity are analysed in turbid systems, such as shallow lakes and rivers. When resuspension from the sediment or loading from the catchment significantly increases inorganic (non-algal) turbidity and hence light attenuation potentials for high production are not realised. Energy available for phytoplankton growth is strongly regulated by underwater light availability which depends on the critical mixing depth, fluctuating light intensities and algal circulation patterns. Higher production rates in shallow waters are often compensated by greater algal respiration due to higher water temperatures when compared to deeper lakes.Total daily integral production of turbulent, turbid environments can be predicted from a combination of easily measured variables such as maximum photosynthetic rates, algal biomass, surface irradiance and some measure of underwater light attenuation. 相似文献
790.
Snow Finches and Mountain-steppe Sparrows differ in habitat selection, feeding, social and vocal behaviour. For these reasons, separation of the genusMontifringilla intoMontifringilla andPyrgilauda is recommended. 相似文献