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71.
Iron requirement of Rhizobium leguminosarum and secretion of anthranilic acid during growth on an iron-deficient medium 总被引:6,自引:0,他引:6
Rhizobium leguminosarum GF160 required iron for growth under aerobic conditions in a chemically defined medium. Maximal growth of bacteria previously depleted in iron was obtained with approximately 50 microM unchelated ferric iron and with glucose as the only carbon source. Growth under iron deficiency did not result in the production of detectable levels of siderophores of either the catechol or hydroxamate types. Growing cells released a Fe3+-reducing agent that was identified as anthranilic acid by paper and thin-layer chromatography, ultraviolet and nuclear magnetic resonance spectroscopy, and mass spectrometry. The amount of anthranilic acid secreted per unit of cell growth was inversely related to the iron concentration in the culture medium and reached concentrations up to 1 mM. Ferric but not ferrous ions were solubilized in the growth medium by anthranilic acid. 相似文献
72.
Jacob L. Jordan Joseph W. Arndt Karl Hanf Guohui Li Janine Hall Stephen Demarest Flora Huang Xiufeng Wu Brian Miller Scott Glaser Erik J. Fernandez Deping Wang Alexey Lugovskoy 《Proteins》2009,77(4):832-841
Bispecific immunoglobulin‐like antibodies capable of engaging multiple antigens represent a promising new class of therapeutic agents. Engineering of these molecules requires optimization of the molecular properties of one of the domain components. Here, we present a detailed crystallographic and computational characterization of the stabilization patterns in the lymphotoxin‐beta receptor (LTβR) binding Fv domain of an anti‐LTβR/anti‐TNF‐related apoptosis inducing ligand receptor‐2 (TRAIL‐R2) bispecific immunoglobulin‐like antibody. We further describe a new hierarchical structure‐guided approach toward engineering of antibody‐like molecules to enhance their thermal and chemical stability. Proteins 2009. © 2009 Wiley‐Liss, Inc. 相似文献
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Kimberly R. Jordan Rodabe N. Amaria Oscar Ramirez Eryn B. Callihan Dexiang Gao Michelle Borakove Elizabeth Manthey Virginia F. Borges Martin D. McCarter 《Cancer immunology, immunotherapy : CII》2013,62(11):1711-1722
Myeloid-derived suppressor cells are increased in the peripheral blood of advanced-stage cancer patients; however, no studies have shown a correlation of these immunosuppressive cells with clinical outcomes in melanoma patients. We characterized the frequency and suppressive function of multiple subsets of myeloid-derived suppressor cells in the peripheral blood of 34 patients with Stage IV melanoma, 20 patients with Stage I melanoma, and 15 healthy donors. The frequency of CD14+ MDSCs (Lin? CD11b+ HLA-DR? CD14+ CD33+) and CD14? MDSCs (Lin? CD11b+ HLA-DR? CD14? CD33+) was increased in the peripheral blood of Stage IV melanoma patients relative to healthy donors. The frequency of CD14+ and CD14? MDSCs correlated with each other and with the increased frequency of regulatory T cells, but not with classically defined monocytes. CD14? MDSCs isolated from the peripheral blood of Stage IV melanoma patients suppressed T cell activation more than those isolated from healthy donors, and the frequency of these cells correlated with disease progression and decreased overall survival. Our study provides the first evidence that the frequency of CD14? MDSCs negatively correlates with clinical outcomes in advanced-stage melanoma patients. These data indicate that suppressive MDSCs should be considered as targets for future immunotherapies. 相似文献
75.
Permafrost thaw resulting from climate warming may dramatically change the succession and carbon dynamics of northern ecosystems.
To examine the joint effects of regional temperature and local species changes on peat accumulation following thaw, we studied
peat accumulation across a regional gradient of mean annual temperature (MAT). We measured aboveground net primary production
(AGNPP) and decomposition over 2 years for major functional groups and used these data to calculate a simple index of net
annual aboveground peat accumulation. In addition, we collected cores from six adjacent frozen and thawed bog sites to document
peat accumulation changes following thaw over the past 200 years. Aboveground biomass and decomposition were more strongly
controlled by local succession than regional climate. AGNPP for some species differed between collapse scars and associated
permafrost plateaus and was influenced by regional MAT. A few species, such as Picea mariana trees on frozen bogs and Sphagnum mosses in thawed bogs, sequestered a disproportionate amount of peat; in addition, changes in their abundance following thaw
changed peat accumulation. 210Pb-dated cores indicated that peat accumulation doubles following thaw and that the accumulation rate is affected by historical
changes in species during succession. Peat accumulation in boreal peatlands following thaw was controlled by a complex mix
of local vegetation changes, regional climate, and history. These results suggest that northern ecosystems may show responses
more complex than large releases of carbon during transient warming.
Received 8 August 2000; accepted 12 January 2001. 相似文献
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The present investigation was made to evaluate biologically relevant quinones as possible catalysts in the generation of hydroxyl radicals from hydrogen peroxide and superoxide radicals. ESR spectra demonstrated that menadione, plastoquinone, and ubiquinone derivatives could all be reduced to their semiquinone forms by electron transfer from superoxide radicals. Reductive homolytic cleavage of H2O2 was observed to be dependent upon the presence of semiquinones in the reaction medium. Our data strongly support the concept that quinones normally involved in physiological processes may also play a role as catalysts of the Haber-Weiss reaction in the biological generation of hydroxyl radicals. 相似文献
78.
Lewis D. Pennington Douglas A. Whittington Michael D. Bartberger Steven R. Jordan Holger Monenschein Thomas T. Nguyen Bryant H. Yang Qiufen M. Xue Filisaty Vounatsos Robert C. Wahl Kui Chen Stephen Wood Martin Citron Vinod F. Patel Stephen A. Hitchcock Wenge Zhong 《Bioorganic & medicinal chemistry letters》2013,23(15):4459-4464
We describe a systematic study of how macrocyclization in the P1–P3 region of hydroxyethylamine-based inhibitors of β-site amyloid precursor protein (APP)-cleaving enzyme (BACE1) modulates in vitro activity. This study reveals that in a number of instances macrocyclization of bis-terminal dienes leads to improved potency toward BACE1 and selectivity against cathepsin D (CatD), as well as greater amyloid β-peptide (Aβ)-lowering activity in HEK293T cells stably expressing APPSW. However, for several closely related analogs the benefits of macrocyclization are attenuated by the effects of other structural features in different regions of the molecules. X-ray crystal structures of three of these novel macrocyclic inhibitors bound to BACE1 revealed their binding conformations and interactions with the enzyme. 相似文献
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