全文获取类型
收费全文 | 4860篇 |
免费 | 397篇 |
国内免费 | 3篇 |
专业分类
5260篇 |
出版年
2024年 | 5篇 |
2023年 | 31篇 |
2022年 | 99篇 |
2021年 | 150篇 |
2020年 | 83篇 |
2019年 | 97篇 |
2018年 | 105篇 |
2017年 | 94篇 |
2016年 | 183篇 |
2015年 | 293篇 |
2014年 | 329篇 |
2013年 | 362篇 |
2012年 | 459篇 |
2011年 | 403篇 |
2010年 | 276篇 |
2009年 | 231篇 |
2008年 | 307篇 |
2007年 | 304篇 |
2006年 | 269篇 |
2005年 | 231篇 |
2004年 | 221篇 |
2003年 | 242篇 |
2002年 | 193篇 |
2001年 | 28篇 |
2000年 | 18篇 |
1999年 | 34篇 |
1998年 | 43篇 |
1997年 | 26篇 |
1996年 | 26篇 |
1995年 | 19篇 |
1994年 | 14篇 |
1993年 | 18篇 |
1992年 | 18篇 |
1991年 | 7篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1987年 | 6篇 |
1983年 | 3篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1975年 | 2篇 |
1958年 | 2篇 |
1945年 | 1篇 |
1944年 | 1篇 |
1934年 | 1篇 |
1932年 | 1篇 |
1931年 | 2篇 |
1929年 | 1篇 |
1928年 | 1篇 |
排序方式: 共有5260条查询结果,搜索用时 0 毫秒
71.
Sheng-Da Zhang Claire-Lise Santini Wei-Jia Zhang Valérie Barbe Sophie Mangenot Charlotte Guyomar Marc Garel Hai-Tao Chen Xue-Gong Li Qun-Jian Yin Yuan Zhao Jean Armengaud Jean-Charles Gaillard Séverine Martini Nathalie Pradel Claude Vidaud François Alberto Claudine Médigue Christian Tamburini Long-Fei Wu 《Extremophiles : life under extreme conditions》2016,20(3):301-310
Bacteria of the genus Photobacterium thrive worldwide in oceans and show substantial eco-physiological diversity including free-living, symbiotic and piezophilic life styles. Genomic characteristics underlying this variability across species are poorly understood. Here we carried out genomic and physiological analysis of Photobacterium phosphoreum strain ANT-2200, the first deep-sea luminous bacterium of which the genome has been sequenced. Using optical mapping we updated the genomic data and reassembled it into two chromosomes and a large plasmid. Genomic analysis revealed a versatile energy metabolic potential and physiological analysis confirmed its growth capacity by deriving energy from fermentation of glucose or maltose, by respiration with formate as electron donor and trimethlyamine N-oxide (TMAO), nitrate or fumarate as electron acceptors, or by chemo-organo-heterotrophic growth in rich media. Despite that it was isolated at a site with saturated dissolved oxygen, the ANT-2200 strain possesses four gene clusters coding for typical anaerobic enzymes, the TMAO reductases. Elevated hydrostatic pressure enhances the TMAO reductase activity, mainly due to the increase of isoenzyme TorA1. The high copy number of the TMAO reductase isoenzymes and pressure-enhanced activity might imply a strategy developed by bacteria to adapt to deep-sea habitats where the instant TMAO availability may increase with depth. 相似文献
72.
Migration (seasonal round-trip movement across relatively large distances) is common within the animal kingdom. This behaviour often incurs extreme costs in terms of time, energy, and/or survival. Climate, food, predation, and breeding are typically suggested as factors favouring the evolution of migration. Although disease regulation has also been considered, few studies consider it as the primary selective pressure for migration. Our aim was to determine, theoretically, under what conditions migration could reduce the long-term disease prevalence within a population, assuming the only benefits of migration are infection-related. We created two mathematical models, one where the population migrates annually and one where the entire population remains on the breeding ground year-round. In each we simulated disease transmission (frequency-dependent and density-dependent) and quantified eventual disease prevalence. In the migration model we varied the time spent migrating, disease-related migration mortality, and the overall migration mortality. When we compared results from the two models, we found that migration generally lowered disease prevalence. We found a population was healthier if it: (1) spent more time migrating (assuming no disease transmission during migration), (2) had higher disease-induced migration mortality, and (3) had an overall higher mortality when migrating (compared to not migrating). These results provide support for two previously proposed mechanisms by which migration can reduce disease prevalence (migratory escape and migratory cull), and also demonstrate that non-selective mortality during migration is a third mechanism. Our findings indicate that migration may be evolutionarily advantageous even if the only migratory benefit is disease control. 相似文献
73.
74.
Philippe Jawinski Sophie Tegelkamp Christian Sander Madlen Häntzsch Jue Huang Nicole Mauche 《Chronobiology international》2016,33(7):893-905
Dopamine has been implicated in the regulation of sleep–wake states and the circadian rhythm. However, there is no consensus on the impact of two established dopaminergic gene variants: the catechol-O-methyltransferase Val158Met (COMT Val158Met; rs4680) and the dopamine D4 receptor Exon III variable-number-of-tandem-repeat polymorphism (DRD4 VNTR). Pursuing a multi-method approach, we examined their potential effects on circadian preferences, arousal regulation and sleep. Subjects underwent a 7-day actigraphy assessment (SenseWear Pro3), a 20-minute resting EEG (analyzed using VIGALL 2.0) and a body mass index (BMI) assessment. Further, they completed the Morningness–Eveningness Questionnaire (MEQ), the Epworth Sleepiness Scale (ESS) and the Pittsburgh Sleep Quality Index (PSQI). The sample comprised 4625 subjects (19–82 years) genotyped for COMT Val158Met, and 689 elderly subjects (64–82 years) genotyped for DRD4 VNTR. The number of subjects varied across phenotypes. Power calculations revealed a minimum required phenotypic variance explained by genotype ranging between 0.5% and 1.5% for COMT Val158Met and between 3.3% and 6.0% for DRD4 VNTR. Analyses did not reveal significant genotype effects on MEQ, ESS, PSQI, BMI, actigraphy and EEG variables. Additionally, we found no compelling evidence in sex- and age-stratified subsamples. Few associations surpassed the threshold of nominal significance (p < .05), providing some indication for a link between DRD4 VNTR and daytime sleepiness. Taken together, in light of the statistical power obtained in the present study, our data particularly suggest no impact of the COMT Val158Met polymorphism on circadian preferences, arousal regulation and sleep. The suggestive link between DRD4 VNTR and daytime sleepiness, on the other hand, might be worth investigation in a sample enriched with younger adults. 相似文献
75.
76.
Johan Decelle Hryhoriy Stryhanyuk Benoit Gallet Giulia Veronesi Matthias Schmidt Sergio Balzano Sophie Marro Clarisse Uwizeye Pierre-Henri Jouneau Josselin Lupette Juliette Jouhet Eric Maréchal Yannick Schwab Nicole L. Schieber Rémi Tucoulou Hans Richnow Giovanni Finazzi Niculina Musat 《Current biology : CB》2019,29(6):968-978.e4
77.
Pierre Ramond Marc Sourisseau Nathalie Simon Sarah Romac Sophie Schmitt Fabienne Rigaut-Jalabert Nicolas Henry Colomban de Vargas Raffaele Siano 《Environmental microbiology》2019,21(2):730-749
The study of protistan functional diversity is crucial to understand the dynamics of oceanic ecological processes. We combined the metabarcoding data of various coastal ecosystems and a newly developed trait-based approach to study the link between taxonomic and functional diversity across marine protistan communities of different size-classes. Environmental DNA was extracted and the V4 18S rDNA genomic region was amplified and sequenced. In parallel, we tried to annotate the operational taxonomic units (OTUs) from our metabarcoding dataset to 30 biological traits using published and accessible information on protists. We then developed a method to study trait correlations across protists (i.e. trade-offs) in order to build the best functional groups. Based on the annotated OTUs and our functional groups, we demonstrated that the functional diversity of marine protist communities varied in parallel with their taxonomic diversity. The coupling between functional and taxonomic diversity was conserved across different protist size classes. However, the smallest size-fraction was characterized by wider taxonomic and functional groups diversity, corroborating the idea that nanoplankton and picoplankton are part of a more stable ecological background on which larger protists and metazoans might develop. 相似文献
78.
79.
Kelly G. Aukema Mian Wang Beatriz de Souza Sophie O'Keane Maia Clipsham Lawrence P. Wackett Alptekin Aksan 《Microbial biotechnology》2022,15(9):2391-2400
Engineered materials to improve the shelf-life of desiccated microbial strains are needed for cost-effective bioaugmentation strategies. High temperatures and humidity of legume-growing regions challenge long-term cell stabilization at the desiccated state. A thermostable xeroprotectant core and hydrophobic water vapour barrier shell encapsulation technique was developed to protect desiccated cells from the environment. A trehalose core matrix increased the stability of desiccated Bradyrhizobium by three orders of magnitude over 20 days at 32°C and 50% relative humidity (RH) compared to buffer alone; however, the improvement was not deemed sufficient for a shelf-stable bioproduct. We tested common additives (skim milk, albumin, gelatin and dextran) to increase the glass transition temperature of the desiccated product to provide further stabilization. Albumin increased the glass transition temperature of the trehalose-based core by 40°C and stabilized desiccated Bradyrhizobium for 4 months during storage at high temperature (32°C) and moderate humidity (50% RH) with only 1 log loss of viability. Although the albumin-trehalose core provided exceptional protection against high temperature, it was ineffective at higher humidity conditions (75%). We therefore incorporated a paraffin shell, which protected desiccated cells against 75% RH providing proof of concept that core and shell encapsulation is an effective strategy to stabilize desiccated cells. 相似文献
80.
Neyton S Lespinasse F Lahaye F Staccini P Paquis-Flucklinger V Santucci-Darmanin S 《Experimental cell research》2007,313(17):3680-3693
MSH4 and MSH5 are members of the MutS homolog family, a conserved group of proteins involved in DNA mismatch correction and homologous recombination. Although several studies have provided compelling evidences suggesting that MSH4 and MSH5 could act together in early and late stages of meiotic recombination, their precise roles are poorly understood and recent findings suggest that the human MSH4 protein may also exert a cytoplasmic function. Here we show that MSH4 is present in the cytoplasm and the nucleus of both testicular cells and transfected somatic cells. Confocal studies on transfected cells provide the first evidence that the subcellular localization of MSH4 is regulated, at least in part, by an active nuclear export pathway dependent on the exportin CRM1. We used deletion mapping and mutagenesis to define two functional nuclear export sequences within the C-terminal part of hMSH4 that mediate nuclear export through the CRM1 pathway. Our results suggest that CRM1 is also involved in MSH5 nuclear export. In addition, we demonstrate that dimerization of MSH4 and MSH5 facilitates their nuclear localization suggesting that dimerization may regulate the intracellular trafficking of these proteins. Our findings suggest that nucleocytoplasmic traffic may constitute a regulatory mechanism for MSH4 and MSH5 functions. 相似文献