全文获取类型
收费全文 | 7532篇 |
免费 | 677篇 |
国内免费 | 2篇 |
出版年
2024年 | 11篇 |
2023年 | 35篇 |
2022年 | 97篇 |
2021年 | 223篇 |
2020年 | 98篇 |
2019年 | 125篇 |
2018年 | 167篇 |
2017年 | 139篇 |
2016年 | 246篇 |
2015年 | 476篇 |
2014年 | 497篇 |
2013年 | 489篇 |
2012年 | 692篇 |
2011年 | 663篇 |
2010年 | 372篇 |
2009年 | 312篇 |
2008年 | 493篇 |
2007年 | 476篇 |
2006年 | 417篇 |
2005年 | 402篇 |
2004年 | 353篇 |
2003年 | 368篇 |
2002年 | 310篇 |
2001年 | 69篇 |
2000年 | 51篇 |
1999年 | 86篇 |
1998年 | 68篇 |
1997年 | 51篇 |
1996年 | 44篇 |
1995年 | 38篇 |
1994年 | 29篇 |
1993年 | 35篇 |
1992年 | 38篇 |
1991年 | 21篇 |
1990年 | 27篇 |
1989年 | 17篇 |
1988年 | 16篇 |
1987年 | 17篇 |
1986年 | 10篇 |
1985年 | 14篇 |
1984年 | 13篇 |
1982年 | 6篇 |
1981年 | 11篇 |
1980年 | 9篇 |
1979年 | 5篇 |
1977年 | 5篇 |
1975年 | 5篇 |
1974年 | 7篇 |
1970年 | 8篇 |
1913年 | 8篇 |
排序方式: 共有8211条查询结果,搜索用时 532 毫秒
881.
Spatial structure is thought to be an important factor influencing the emergence and maintenance of genetic diversity. Previous studies have demonstrated that environmental heterogeneity, provided by spatial structure, leads to adaptive radiation of populations. In the present study, we investigate not only the impact of environmental heterogeneity on adaptive radiation, but also of population fragmentation and niche construction. Replicate populations founded by a single genotype of Escherichia coli were allowed to evolve for 900 generations by serial transfer in either a homogeneous environment, or a spatially structured environment that was either kept intact or destroyed with each daily transfer. Only populations evolving in the structured environment with intact population structure diversified: clones are significantly divergent in sugar catabolism, and show frequency-dependent fitness interactions indicative of stable coexistence. These findings demonstrate an important role for population fragmentation, a consequence of population structure in spatially structured environments, on the diversification of populations. 相似文献
882.
883.
Phospholipase D (PLD) hydrolyzes the phosphodiester bond of the predominant membrane phospholipid, phosphatidylcholine producing phosphatidic acid and free choline. This activity can participate in signal transduction pathways and impact on vesicle trafficking for secretion and endocytosis, as well as receptor signalling. Phospholipids can regulate PLD activity directly, through specific intermolecular interactions, or indirectly, through their effect on the localization or activity of PLD's protein effectors. This short review highlights these various phospholipid inputs into the regulation of PLD activity and also reviews potential roles for PLD-generated phosphatidic acid, particularly a mechanism by which the phospholipid may participate in the process of vesicular trafficking. 相似文献
884.
885.
Tucker TJ Abrams MT Buser CA Davide JP Ellis-Hutchings M Fernandes C Gibbs JB Graham SL Hartman GD Huber HE Liu D Lobell RB Lumma WC Robinson RG Sisko JT Smith AM 《Bioorganic & medicinal chemistry letters》2002,12(15):2027-2030
We have prepared a series of potent, dual inhibitors of the prenyl transferases farnesyl protein transferase (FPTase) and geranyl-geranyl protein transferase I (GGPTase). The compounds were shown to possess potent activity against both enzymes in cell culture. Mechanistic analysis has shown that the compounds are CAAX competitive for FPTase inhibition but geranyl-geranyl pyrophosphate (GGPP) competitive for GGPTase inhibiton. 相似文献
886.
Monteiro RC Moura IC Launay P Tsuge T Haddad E Benhamou M Cooper MD Arcos-Fajardo M 《Trends in molecular medicine》2002,8(10):464-468
IgA nephropathy (IgAN), the most common primary glomerulonephritis worldwide, frequently progresses to renal failure. The pathogenesis of this disease involves the deposition of undergalactosylated IgA1 complexes in the glomerular mesangium. How the IgA1 complexes are generated and why they are deposited in the mesangium remains unclear. We propose a model wherein two types of IgA receptors participate in sequential steps to promote the development of IgAN, with FcalphaRI (CD89) being initially involved in the formation of circulating IgA-containing complexes and, subsequently, transferrin receptor (CD71) in mediating mesangial deposition of IgA1 complexes. 相似文献
887.
888.
889.
Ammerman ML Downey KM Hashimi H Fisk JC Tomasello DL Faktorová D Kafková L King T Lukes J Read LK 《Nucleic acids research》2012,40(12):5637-5650
Trypanosoma brucei undergoes an essential process of mitochondrial uridine insertion and deletion RNA editing catalyzed by a 20S editosome. The multiprotein mitochondrial RNA-binding complex 1 (MRB1) is emerging as an equally essential component of the trypanosome RNA editing machinery, with additional functions in gRNA and mRNA stabilization. The distinct and overlapping protein compositions of reported MRB1 complexes and diverse MRB1 functions suggest that the complex is composed of subcomplexes with RNA-dependent and independent interactions. To determine the architecture of the MRB1 complex, we performed a comprehensive yeast two-hybrid analysis of 31 reported MRB1 proteins. We also used in vivo analyses of tagged MRB1 components to confirm direct and RNA-mediated interactions. Here, we show that MRB1 contains a core complex comprised of six proteins and maintained by numerous direct interactions. The MRB1 core associates with multiple subcomplexes and proteins through RNA-enhanced or RNA-dependent interactions. These findings provide a framework for interpretation of previous functional studies and suggest that MRB1 is a dynamic complex that coordinates various aspects of mitochondrial gene regulation. 相似文献
890.
A Bilitou N De Marco AM Bello L Garzia P Carotenuto M Kim C Campanella S Ohnuma M Zollo 《Gene》2012,509(1):93-103
The development of stratified retinal cell architecture is highly conserved in all vertebrates, implying that a common fundamental molecular mechanism is involved in the generation of the organized retina. However, the detailed molecular mechanisms of retinal development are not fully understood. Here we have identified the Xenopus ortholog of prune and show that it is expressed in both differentiating and differentiated retinal domains during development. Interestingly, these spatial and temporal expression patterns coincide with the expression of prune binding partners, the NM23 family members. Overexpression of prune in retinal precursor cells significantly increases the ratio of Müller glial cells as observed by modulation of NM23 activity (Mochizuki et al., 2009). However, a mutated form of prune that has replacement of four aspartate (D) residues (D'Angelo et al., 2004), essential for phosphodiesterase activity, does not exhibit gliogenic activity. Our observations suggest that Xenopus prune may regulate Müller gliogenesis through phosphodiesterase-mediated regulation of NM23 family members. 相似文献