全文获取类型
收费全文 | 10549篇 |
免费 | 255篇 |
国内免费 | 389篇 |
出版年
2024年 | 13篇 |
2023年 | 251篇 |
2022年 | 122篇 |
2021年 | 204篇 |
2020年 | 235篇 |
2019年 | 440篇 |
2018年 | 374篇 |
2017年 | 289篇 |
2016年 | 261篇 |
2015年 | 297篇 |
2014年 | 639篇 |
2013年 | 1069篇 |
2012年 | 644篇 |
2011年 | 572篇 |
2010年 | 347篇 |
2009年 | 532篇 |
2008年 | 557篇 |
2007年 | 570篇 |
2006年 | 395篇 |
2005年 | 390篇 |
2004年 | 343篇 |
2003年 | 300篇 |
2002年 | 229篇 |
2001年 | 191篇 |
2000年 | 174篇 |
1999年 | 204篇 |
1998年 | 188篇 |
1997年 | 165篇 |
1996年 | 184篇 |
1995年 | 147篇 |
1994年 | 119篇 |
1993年 | 71篇 |
1992年 | 78篇 |
1991年 | 74篇 |
1990年 | 75篇 |
1989年 | 56篇 |
1988年 | 39篇 |
1987年 | 49篇 |
1986年 | 27篇 |
1985年 | 44篇 |
1984年 | 35篇 |
1983年 | 29篇 |
1982年 | 40篇 |
1981年 | 26篇 |
1980年 | 15篇 |
1979年 | 29篇 |
1978年 | 18篇 |
1977年 | 8篇 |
1976年 | 12篇 |
1975年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Flexibility in reproductive timing in human females: integrating ultimate and proximate explanations
Nettle D 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2011,366(1563):357-365
From an ultimate perspective, the age of onset of female reproduction should be sensitive to variation in mortality rates, and variation in the productivity of non-reproductive activities. In accordance with this prediction, most of the cross-national variation in women's age at first birth can be explained by differences in female life expectancies and incomes. The within-country variation in England shows a similar pattern: women have children younger in neighbourhoods where the expectation of healthy life is shorter and incomes are lower. I consider the proximate mechanisms likely to be involved in producing locally appropriate reproductive decisions. There is evidence suggesting that developmental induction, social learning and contextual evocation may all play a role. 相似文献
992.
993.
Li B Cardinale SC Butler MM Pai R Nuss JE Peet NP Bavari S Bowlin TL 《Bioorganic & medicinal chemistry》2011,19(24):7338-7348
Botulinum neurotoxins (BoNTs) are the most lethal of biological substances, and are categorized as class A biothreat agents by the Centers for Disease Control and Prevention. There are currently no drugs to treat the deadly flaccid paralysis resulting from BoNT intoxication. Among the seven BoNT serotypes, the development of therapeutics to counter BoNT/A is a priority (due to its long half-life in the neuronal cytosol and its ease of production). In this regard, the BoNT/A enzyme light chain (LC) component, a zinc metalloprotease responsible for the intracellular cleavage of synaptosomal-associated protein of 25 kDa, is a desirable target for developing post-BoNT/A intoxication rescue therapeutics. In an earlier study, we reported the high throughput screening of a library containing 70,000 compounds, and uncovered a novel class of benzimidazole acrylonitrile-based BoNT/A LC inhibitors. Herein, we present both structure–activity relationships and a proposed mechanism of action for this novel inhibitor chemotype. 相似文献
994.
N. Sathyanarayana M. Leelambika S. Mahesh Mahammad Jaheer 《Physiology and Molecular Biology of Plants》2011,17(2):171-180
Amplified fragment length polymorphism (AFLP) marker was used to assess diversity in germplasm collection of Mucuna species which has gained tremendous attention in the recent past due to its promising nutritional, agronomic and medicinal attributes. Twenty five accessions comprising five species, collected from seven states of India were evaluated with twelve AFLP primer combinations that generated a total of 1,612 fragments with an average of 134 fragments per primer combination. The values of polymorphic information content (PIC), marker index (MI) and the resolving power (Rp) demonstrated the utility of the primer combinations used in the present study for discriminating the Mucuna accessions. UPGMA and Principal coordinate analysis (PCoA) of the genotypic data revealed clustering of accessions as per phenetic and genetic relationships. The Jaccard’s similarity coefficient values suggested good variability among the M. pruriens accessions indicating their utility in breeding programs. Molecular diversity presented in this study combined with the datasets on other morphological/agronomic traits will be highly useful for selecting appropriate accessions for plant improvement through conventional as well as molecular breeding approaches and for evolving suitable conservation strategies. 相似文献
995.
996.
The functional sites were predicted for Nudix enzymes from pathogenic microorganisms such as Streprococcus pneumonia (2B06) and Enterococcus faecalis (2AZW). Their structures are already determined, however, no data is reported about their functional sites, substrates and inhibitors. Therefore, we report prediction of functional sites in these Nudix enzymes via Geometric Invariant (GI) technique (Construct different geometries of peptides which remain unchanged). The GI method enumerated 2B06: RA57, EA58, EA61, EA62 and 2AZW: RA62, EA63, EA66, EA67 as putative functional sites in these Nudix enzymes. In addition, the substrate was predicted via Molecular docking (Docking of substrates against whole structure of Nudix enzymes). The substrate ADP-Ribose was docked with the Nudix enzymes, 2B06 (Docking energy -15.68 Kcal/mol) and 2AZW (Docking energy -10.86 Kcal/mol) with the higher affinity and the lower docking energy as compared to other substrates. The residues EA62 in 2B06 and RA62 in 2AZW make hydrogen bonds with the ADP-ribose. Furthermore, we screened 51 inhibitor compounds against structures of 2B06 and 2AZW. The inhibitor compounds AMPCPR and CID14258187 were docked well as compared to other compounds. The compound CID14258187 was also in agreement with Lipinski rule of 5 for drug likeness properties. Therefore, our findings of functional sites, substrates and inhibitors for these Nudix enzymes may help in structure based drug designing against Streprococcus pneumonia and Enterococcus faecalis. 相似文献
997.
Advanced personalized dosimetry for molecular nuclear therapy has been shown to be feasible in clinical practice. At the same time instrumentation and dosimetric software are still evolving at a high pace. Procedures developed so far differ in approach and sophistication, and standard operating procedures necessary for accurate patient specific dosimetry do not yet exist. For this reason we restricted ourselves to reviewing the literature and highlighting relevant developments. 相似文献
998.
Analytical ultracentrifugation combined with X-ray and neutron scattering: Experiment and modelling 总被引:1,自引:0,他引:1
Analytical ultracentrifugation and solution scattering provide different multi-parameter structural and compositional information on proteins. The joint application of the two methods supplements high resolution structural studies by crystallography and NMR. We summarise the procedures required to obtain equivalent ultracentrifugation and X-ray and neutron scattering data. The constrained modelling of ultracentrifugation and scattering data is important to confirm the experimental data analysis and yields families of best-fit molecular models for comparison with crystallography and NMR structures. This modelling of ultracentrifugation and scattering data is described in terms of starting models, their conformational randomisation in trial-and-error fits, and the identification of the final best-fit models. Seven applications of these methods are described to illustrate the current state-of-the-art. These include the determination of antibody solution structures (the human IgG4 subclass, and oligomeric forms of human IgA and its secretory component), the solution structures of the complement proteins of innate immunity (Factor H and C3/C3u) and their interactions with macromolecular ligands (C-reactive protein), and anionic polysaccharides (heparin). Complementary features of joint ultracentrifugation and scattering experiments facilitate an improved understanding of crystal structures (illustrated for C3/C3u, C-reactive protein and heparin). If a large protein or its complex cannot be crystallised, the joint ultracentrifugation-scattering approach provides a means to obtain an overall macromolecular structure. 相似文献
999.
1000.