全文获取类型
收费全文 | 7391篇 |
免费 | 649篇 |
国内免费 | 1篇 |
出版年
2024年 | 11篇 |
2023年 | 33篇 |
2022年 | 91篇 |
2021年 | 208篇 |
2020年 | 97篇 |
2019年 | 121篇 |
2018年 | 160篇 |
2017年 | 134篇 |
2016年 | 239篇 |
2015年 | 463篇 |
2014年 | 493篇 |
2013年 | 479篇 |
2012年 | 681篇 |
2011年 | 652篇 |
2010年 | 365篇 |
2009年 | 309篇 |
2008年 | 485篇 |
2007年 | 471篇 |
2006年 | 418篇 |
2005年 | 392篇 |
2004年 | 349篇 |
2003年 | 359篇 |
2002年 | 302篇 |
2001年 | 69篇 |
2000年 | 44篇 |
1999年 | 84篇 |
1998年 | 70篇 |
1997年 | 45篇 |
1996年 | 45篇 |
1995年 | 40篇 |
1994年 | 26篇 |
1993年 | 33篇 |
1992年 | 31篇 |
1991年 | 22篇 |
1990年 | 19篇 |
1989年 | 15篇 |
1988年 | 14篇 |
1987年 | 17篇 |
1986年 | 9篇 |
1985年 | 14篇 |
1984年 | 14篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1981年 | 11篇 |
1980年 | 10篇 |
1979年 | 6篇 |
1978年 | 9篇 |
1977年 | 11篇 |
1976年 | 7篇 |
1974年 | 6篇 |
排序方式: 共有8041条查询结果,搜索用时 15 毫秒
81.
The TEL-Syk fusion protein was isolated from a patient with myelodysplasia with megakaryocyte blasts. Expression of TEL-Syk transforms interleukin-3 (IL-3)-dependent Ba/F3 cells in vitro by deregulating STAT5-mediated signal transduction pathways. In vivo, TEL-Syk expression in pre-B cells blocks B cell differentiation, leading to lymphoid leukemia. Here, we demonstrate that TEL-Syk introduced into fetal liver hematopoietic cells, which are then adoptively transferred into lethally irradiated recipients, leads to an aggressive myelodysplasia with myelofibrosis that is lethal in mice by 60–75 days. Expression of TEL-Syk induces a short-lived myeloexpansion that is rapidly followed by bone marrow failure and extreme splenic/hepatic fibrosis accompanied by extensive apoptosis. The disease is dependent on Syk kinase activity. Analysis of serum from TEL-Syk mice reveals an inflammatory cytokine signature reminiscent of that found in the sera from patients and mouse models of myeloproliferative neoplasms. TEL-Syk expressing cells showed constitutive STAT5 phosphorylation, which was resistant to JAK inhibition, consistent with deregulated cytokine signaling. These data indicate that expression of TEL-Syk in fetal liver hematopoietic cells results in JAK-independent STAT5 phosphorylation ultimately leading to a uniquely aggressive and lethal form of myelofibrosis. 相似文献
82.
83.
Laura Noël-Romas Michelle Perner Refilwe Molatlhegi Christina Farr Zuend Amanda Mabhula Sarah Hoger Alana Lamont Kenzie Birse Alicia Berard Stuart McCorrister Garett Westmacott Al Leslie Vanessa Poliquin Renee Heffron Lyle R. McKinnon Adam D. Burgener 《PLoS pathogens》2020,16(12)
Alterations to the mucosal environment of the female genital tract, such as genital inflammation, have been associated with increased HIV acquisition in women. As the microbiome and hormonal contraceptives can affect vaginal mucosal immunity, we hypothesized these components may interact in the context of HIV susceptibility. Using previously published microbiome data from 685 women in the CAPRISA-004 trial, we compared relative risk of HIV acquisition in this cohort who were using injectable depot medroxyprogesterone acetate (DMPA), norethisterone enanthate (NET-EN), and combined oral contraceptives (COC). In women who were Lactobacillus-dominant, HIV acquisition was 3-fold higher in women using DMPA relative to women using NET-EN or COC (OR: 3.27; 95% CI: 1.24–11.24, P = 0.0305). This was not observed in non-Lactobacillus-dominant women (OR: 0.95, 95% CI: 0.44–2.15, P = 0.895) (interaction P = 0.0686). Higher serum MPA levels associated with increased molecular pathways of inflammation in the vaginal mucosal fluid of Lactobacillus-dominant women, but no differences were seen in non-Lactobacillus dominant women. This study provides data suggesting an interaction between the microbiome, hormonal contraceptives, and HIV susceptibility. 相似文献
84.
Mauricio Isaacs 《Inorganica chimica acta》2006,359(12):3847-3854
A series of new heteroleptic, tris(polypyridyl)chromium(III) complexes, [Cr(phen)2L]3+ (L = substituted phenanthrolines or bipyridines), has been prepared and characterized, and their photophyical properties in a number of solvents have been investigated. X-ray crystallography measurements confirmed that the cationic (3+) units contain only one ligand L plus two phenanthroline ligands. Electrochemical and photophysical data showed that both ground state potentials and lifetime decays are sensitive to ligand structure and the nature of the solvent with the exception of compounds containing L = 5-amino-1,10-phenanthroline (aphen) and 2,2′-bipyrimidine (bpm). Addition of electron-donating groups in the ligand structure shifts redox potentials to more negative values than those observed for the parent compound, [Cr(phen)3]3+. Emission decays show a complex dependence with the solvent. The longest lifetime was observed for [Cr(phen)2(dip)]3+ (dip = 4,7-diphenylphenanthroline) in air-free aqueous solutions, τ = 273 μs. Solvent effects are explained in terms of the affinity of hydrophobic complexes for non-polar solvent molecules and the solvent microstructure surrounding chromium units. 相似文献
85.
86.
87.
88.
Matthias Albrecht David Kleijn Neal M. Williams Matthias Tschumi Brett R. Blaauw Riccardo Bommarco Alistair J. Campbell Matteo Dainese Francis A. Drummond Martin H. Entling Dominik Ganser G. Arjen de Groot Dave Goulson Heather Grab Hannah Hamilton Felix Herzog Rufus Isaacs Katja Jacot Philippe Jeanneret Mattias Jonsson Eva Knop Claire Kremen Douglas A. Landis Gregory M. Loeb Lorenzo Marini Megan McKerchar Lora Morandin Sonja C. Pfister Simon G. Potts Maj Rundlf Hillary Sardias Amber Sciligo Carsten Thies Teja Tscharntke Eric Venturini Eve Veromann Ines M.G. Vollhardt Felix Wckers Kimiora Ward Andrew Wilby Megan Woltz Steve Wratten Louis Sutter 《Ecology letters》2020,23(10):1488-1498
Floral plantings are promoted to foster ecological intensification of agriculture through provisioning of ecosystem services. However, a comprehensive assessment of the effectiveness of different floral plantings, their characteristics and consequences for crop yield is lacking. Here we quantified the impacts of flower strips and hedgerows on pest control (18 studies) and pollination services (17 studies) in adjacent crops in North America, Europe and New Zealand. Flower strips, but not hedgerows, enhanced pest control services in adjacent fields by 16% on average. However, effects on crop pollination and yield were more variable. Our synthesis identifies several important drivers of variability in effectiveness of plantings: pollination services declined exponentially with distance from plantings, and perennial and older flower strips with higher flowering plant diversity enhanced pollination more effectively. These findings provide promising pathways to optimise floral plantings to more effectively contribute to ecosystem service delivery and ecological intensification of agriculture in the future. 相似文献
89.
Amy E. Zanne Kessy Abarenkov Michelle E. Afkhami Carlos A. Aguilar‐Trigueros Scott Bates Jennifer M. Bhatnagar Posy E. Busby Natalie Christian William K. Cornwell Thomas W. Crowther Habacuc Flores‐Moreno Dimitrios Floudas Romina Gazis David Hibbett Peter Kennedy Daniel L. Lindner Daniel S. Maynard Amy M. Milo Rolf Henrik Nilsson Jeff Powell Mark Schildhauer Jonathan Schilling Kathleen K. Treseder 《Biological reviews of the Cambridge Philosophical Society》2020,95(2):409-433
Fungi play many essential roles in ecosystems. They facilitate plant access to nutrients and water, serve as decay agents that cycle carbon and nutrients through the soil, water and atmosphere, and are major regulators of macro‐organismal populations. Although technological advances are improving the detection and identification of fungi, there still exist key gaps in our ecological knowledge of this kingdom, especially related to function . Trait‐based approaches have been instrumental in strengthening our understanding of plant functional ecology and, as such, provide excellent models for deepening our understanding of fungal functional ecology in ways that complement insights gained from traditional and ‐omics‐based techniques. In this review, we synthesize current knowledge of fungal functional ecology, taxonomy and systematics and introduce a novel database of fungal functional traits (FunFun). FunFun is built to interface with other databases to explore and predict how fungal functional diversity varies by taxonomy, guild, and other evolutionary or ecological grouping variables. To highlight how a quantitative trait‐based approach can provide new insights, we describe multiple targeted examples and end by suggesting next steps in the rapidly growing field of fungal functional ecology. 相似文献
90.
Fatemeh Adelnia Ceereena Ubaida‐Mohien Ruin Moaddel Michelle Shardell Alexey Lyashkov Kenneth W. Fishbein Miguel A. Aon Richard G. Spencer Luigi Ferrucci 《Aging cell》2020,19(4)
Adequate support of energy for biological activities and during fluctuation of energetic demand is crucial for healthy aging; however, mechanisms for energy decline as well as compensatory mechanisms that counteract such decline remain unclear. We conducted a discovery proteomic study of skeletal muscle in 57 healthy adults (22 women and 35 men; aged 23–87 years) to identify proteins overrepresented and underrepresented with better muscle oxidative capacity, a robust measure of in vivo mitochondrial function, independent of age, sex, and physical activity. Muscle oxidative capacity was assessed by 31P magnetic resonance spectroscopy postexercise phosphocreatine (PCr) recovery time (τPCr) in the vastus lateralis muscle, with smaller τPCr values reflecting better oxidative capacity. Of the 4,300 proteins quantified by LC‐MS in muscle biopsies, 253 were significantly overrepresented with better muscle oxidative capacity. Enrichment analysis revealed three major protein clusters: (a) proteins involved in key energetic mitochondrial functions especially complex I of the electron transport chain, tricarboxylic acid (TCA) cycle, fatty acid oxidation, and mitochondrial ABC transporters; (b) spliceosome proteins that regulate mRNA alternative splicing machinery, and (c) proteins involved in translation within mitochondria. Our findings suggest that alternative splicing and mechanisms that modulate mitochondrial protein synthesis are central features of the molecular mechanisms aimed at maintaining mitochondrial function in the face of impairment. Whether these mechanisms are compensatory attempt to counteract the effect of aging on mitochondrial function should be further tested in longitudinal studies. 相似文献