全文获取类型
收费全文 | 6237篇 |
免费 | 598篇 |
国内免费 | 3篇 |
出版年
2024年 | 8篇 |
2023年 | 45篇 |
2022年 | 117篇 |
2021年 | 207篇 |
2020年 | 116篇 |
2019年 | 128篇 |
2018年 | 163篇 |
2017年 | 121篇 |
2016年 | 211篇 |
2015年 | 397篇 |
2014年 | 412篇 |
2013年 | 485篇 |
2012年 | 624篇 |
2011年 | 553篇 |
2010年 | 323篇 |
2009年 | 281篇 |
2008年 | 403篇 |
2007年 | 385篇 |
2006年 | 357篇 |
2005年 | 295篇 |
2004年 | 273篇 |
2003年 | 235篇 |
2002年 | 191篇 |
2001年 | 45篇 |
2000年 | 25篇 |
1999年 | 29篇 |
1998年 | 61篇 |
1997年 | 37篇 |
1996年 | 30篇 |
1995年 | 24篇 |
1994年 | 25篇 |
1993年 | 20篇 |
1992年 | 20篇 |
1991年 | 17篇 |
1990年 | 11篇 |
1989年 | 8篇 |
1988年 | 12篇 |
1987年 | 11篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1982年 | 15篇 |
1981年 | 12篇 |
1980年 | 11篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1976年 | 4篇 |
1973年 | 5篇 |
1971年 | 7篇 |
排序方式: 共有6838条查询结果,搜索用时 15 毫秒
991.
992.
David D. Stenehjem Michael Toole Joseph Merriman Kinjal Parikh Stephanie Daignault Sarah Scarlett Peg Esper Katherine Skinner Aaron Udager Srinivas Kiran Tantravahi David Gill Alli M. Straubhar Archana M. Agarwal Kenneth F. Grossmann Wolfram E. Samlowski Bruce Redman Neeraj Agarwal Ajjai Alva 《Cancer immunology, immunotherapy : CII》2016,65(8):941-949
993.
Jara Radeck Susanne Gebhard Peter Shevlin Orchard Marion Kirchner Stephanie Bauer Thorsten Mascher Georg Fritz 《Molecular microbiology》2016,100(4):607-620
Protection against antimicrobial peptides (AMPs) often involves the parallel production of multiple, well‐characterized resistance determinants. So far, little is known about how these resistance modules interact and how they jointly protect the cell. Here, we studied the interdependence between different layers of the envelope stress response of Bacillus subtilis when challenged with the lipid II cycle‐inhibiting AMP bacitracin. The underlying regulatory network orchestrates the production of the ABC transporter BceAB, the UPP phosphatase BcrC and the phage‐shock proteins LiaIH. Our systems‐level analysis reveals a clear hierarchy, allowing us to discriminate between primary (BceAB) and secondary (BcrC and LiaIH) layers of bacitracin resistance. Deleting the primary layer provokes an enhanced induction of the secondary layer to partially compensate for this loss. This study reveals a direct role of LiaIH in bacitracin resistance, provides novel insights into the feedback regulation of the Lia system, and demonstrates a pivotal role of BcrC in maintaining cell wall homeostasis. The compensatory regulation within the bacitracin network can also explain how gene expression noise propagates between resistance layers. We suggest that this active redundancy in the bacitracin resistance network of B. subtilis is a general principle to be found in many bacterial antibiotic resistance networks. 相似文献
994.
Stuart Weston Stephanie Czieso Ian J. White Sarah E. Smith Rachael S. Wash Carmen Diaz‐Soria Paul Kellam Mark Marsh 《Traffic (Copenhagen, Denmark)》2016,17(9):997-1013
Interferon inducible transmembrane proteins (IFITMs) are broad‐spectrum antiviral factors. In cell culture the entry of many enveloped viruses, including orthomyxo‐, flavi‐, and filoviruses, is inhibited by IFITMs, though the mechanism(s) involved remain unclear and may vary between viruses. We demonstrate that Sindbis and Semliki Forest virus (SFV), which both use endocytosis and acid‐induced membrane fusion in early endosomes to infect cells, are restricted by the early endosomal IFITM3. The late endosomal IFITM2 is less restrictive and the plasma membrane IFITM1 does not inhibit normal infection by either virus. IFITM3 inhibits release of the SFV capsid into the cytosol, without inhibiting binding, internalization, trafficking to endosomes or low pH‐induced conformational changes in the envelope glycoprotein. Infection by SFV fusion at the cell surface was inhibited by IFITM1, but was equally inhibited by IFITM3. Furthermore, an IFITM3 mutant (Y20A) that is localized to the plasma membrane inhibited infection by cell surface fusion more potently than IFITM1. Together, these results indicate that IFITMs, in particular IFITM3, can restrict alphavirus infection by inhibiting viral fusion with cellular membranes. That IFITM3 can restrict SFV infection by fusion at the cell surface equivalently to IFITM1 suggests that IFITM3 has greater antiviral potency against SFV. 相似文献
995.
Christie JM Corchnoy SB Swartz TE Hokenson M Han IS Briggs WR Bogomolni RA 《Biochemistry》2007,46(32):9310-9319
Phototropins (phot1 and phot2) are blue light receptor kinases that control a range of photoresponses that serve to optimize the photosynthetic efficiency of plants. Light sensing by the phototropins is mediated by a repeated motif at the N-terminal region of the protein known as the LOV domain. Bacterially expressed LOV domains bind flavin mononucleotide noncovalently and are photochemically active in solution. Irradiation of the LOV domain results in the formation of a flavin-cysteinyl adduct (LOV390) which thermally relaxes back to the ground state in the dark, effectively completing a photocycle that serves as a molecular switch to control receptor kinase activity. We have employed a random mutagenesis approach to identify further amino acid residues involved in LOV-domain photochemistry. Escherichia coli colonies expressing a mutagenized population of LOV2 derived from Avena sativa (oat) phot1 were screened for variants that showed altered photochemical reactivity in response to blue light excitation. One variant showed slower rates of LOV390 formation but exhibited adduct decay times 1 order of magnitude faster than wild type. A single Ile --> Val substitution was responsible for the effects observed, which removes a single methyl group found in van der Waals contact with the cysteine sulfur involved in adduct formation. A kinetic acceleration trend was observed for adduct decay by decreasing the size of the isoleucine side chain. Our findings therefore indicate that the steric nature of this amino acid side chain contributes to stabilization of the C-S cysteinyl adduct. 相似文献
996.
Eric W. Bridgeford Shangsi Wang Zeyi Wang Ting Xu Cameron Craddock Jayanta Dey Gregory Kiar William Gray-Roncal Carlo Colantuoni Christopher Douville Stephanie Noble Carey E. Priebe Brian Caffo Michael Milham Xi-Nian Zuo Consortium for Reliability Reproducibility Joshua T. Vogelstein 《PLoS computational biology》2021,17(9)
Replicability, the ability to replicate scientific findings, is a prerequisite for scientific discovery and clinical utility. Troublingly, we are in the midst of a replicability crisis. A key to replicability is that multiple measurements of the same item (e.g., experimental sample or clinical participant) under fixed experimental constraints are relatively similar to one another. Thus, statistics that quantify the relative contributions of accidental deviations—such as measurement error—as compared to systematic deviations—such as individual differences—are critical. We demonstrate that existing replicability statistics, such as intra-class correlation coefficient and fingerprinting, fail to adequately differentiate between accidental and systematic deviations in very simple settings. We therefore propose a novel statistic, discriminability, which quantifies the degree to which an individual’s samples are relatively similar to one another, without restricting the data to be univariate, Gaussian, or even Euclidean. Using this statistic, we introduce the possibility of optimizing experimental design via increasing discriminability and prove that optimizing discriminability improves performance bounds in subsequent inference tasks. In extensive simulated and real datasets (focusing on brain imaging and demonstrating on genomics), only optimizing data discriminability improves performance on all subsequent inference tasks for each dataset. We therefore suggest that designing experiments and analyses to optimize discriminability may be a crucial step in solving the replicability crisis, and more generally, mitigating accidental measurement error. 相似文献
997.
Astrid Halbach Dagmar Nierwetberg Justus G. Müller Ursula Sauer Thomas Kerkau Nicole Stolte Petra Hofmann Stephanie Czub Volker ter Meulen & Sieghart Sopper 《Journal of medical primatology》1999,29(3-4):148-157
Human immunodeficiency virus (HIV) infection leads to a decline of CD4+ T-cells in blood. Because blood represents only a small proportion of the total lymphocyte pool, it is important to investigate other lymphoid organs. So far, only relative proportions of lymphocyte subsets in single peripheral lymph node (LN) regions of HIV-infected patients and simian immunodeficiency virus (SIV)-infected macaques have been documented. We have therefore quantified the absolute numbers of lymphocyte subsets in blood and six different LN regions of 10 uninfected and 26 SIV-infected macaques. In addition, we have determined the expression of markers of activation and differentiation. Already, in uninfected monkeys, there were significant differences in the cellular composition of different LN regions. Infection with SIV resulted in drastic changes in the proportion as well as absolute numbers of different lymphocyte subsets. Moreover, the relative contribution of the single LN regions to the total lymphocyte pool was also altered. 相似文献
998.
Stephanie Blum Susana Alvarez Dirk Haller Pablo Perez Eduardo J. Schiffrin 《Antonie van Leeuwenhoek》1999,76(1-4):199-205
The intestinal mucosal surface is colonised by the comensal microflora that attains very high numbers of bacterial cells in the distal intestine, more specifically in the colon. At the same time these extensive areas are the interface with the external environment, through which most pathogens initiate infectious processes in mammals. Intestinal mechanisms of defense need to discriminate accurately between comensal, symbiotic microflora, and exogenous pathogens. Today we do not fully understand the essence of the mechanism of discrimination but, probably, innate as well as adaptive immune responses participate in this process. We have explored , in in vitro models, the capacity of mucosal immunocompetent cells to discriminate amongst signals delivered by different types of bacteria. We have found at least two different patterns of innate response to gram-negative and gram-positive bacteria, and within this last group big differences are observed between species. We have only wo rked with non-pathogenic bacteria in what may represent the modulation of the physiological host status. The understanding of these modulatory functions could render a unique possibility for the use of food-borne bacteria to prevent or correct intestinal problems associated with food allergy, inflammatory bowel disease, and autoimmunity. 相似文献
999.
Archana Unnikrishnan Stephanie Matyi Karla Garrett Michelle RanjoBishop David B. Allison Keisuke Ejima Xiwei Chen Stephanie Dickinson Arlan Richardson 《Aging cell》2021,20(11)
Dietary restriction (DR) was reported to either have no effect or reduce the lifespan of the majority of the 41‐recombinant inbred (RI) lines studied by Liao et al. (Aging Cell, 2010, 9, 92). In an appropriately power longevity study (n > 30 mice/group), we measured the lifespan of the four RI lines (115‐RI, 97‐RI, 98‐RI, and 107‐RI) that were reported to have the greatest decrease in lifespan when fed 40% DR. DR increased the median lifespan of female RI‐115, 97‐RI, and 107‐RI mice and male 115‐RI mice. DR had little effect (<4%) on the median lifespan of female and male 98‐RI mice and male 97‐RI mice and reduced the lifespan of male 107‐RI mice over 20%. While our study was unable to replicate the effect of DR on the lifespan of the RI mice (except male 107‐RI mice) reported by Liao et al. (Aging Cell, 2010, 9, 92), we found that the genotype of a mouse had a major impact on the effect of DR on lifespan, with the effect of DR ranging from a 50% increase to a 22% decrease in median lifespan. No correlation was observed between the changes in either body composition or glucose tolerance induced by DR and the changes observed in lifespan of the four RI lines of male and female mice. These four RI lines of mice give the research community a unique resource where investigators for the first time can study the anti‐aging mechanism of DR by comparing mice in which DR increases lifespan to mice where DR has either no effect or reduces lifespan. 相似文献
1000.