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991.
992.
Michelle C. W. Tang Steve Binos Eng K. Ong Lee H. Wong Jeffrey R. Mann 《Chromosoma》2014,123(6):587-595
Histone variants can incorporate into the nucleosome outside of S-phase. Some are known to play important roles in mammalian germ cell development, this cell lineage being characterized by long phases of quiescence, a protracted meiotic phase, and genome-wide epigenetic reformatting events. The best known example of such an event is the global-scale erasure of DNA methylation in sexually indifferent primordial germ cells, then its re-establishment in fetal prospermatogonia and growing oocytes. Histone H3 and its post-translationally modified forms provide important waypoints in the establishment of epigenetic states. Using mass spectrometry and immunoblotting, we show that the H3.3 replacement variant is present at an unusually high amount in mouse prospermatogonia at the peak stage of global DNA methylation re-establishment. We speculate that H3.3 facilitates this process through achieving a greater level of accessibility of chromatin modifiers to DNA. 相似文献
993.
Michael Dickover Jeffrey M. Hegarty Kim Ly Diana Lopez Hongbo Yang Ruilin Zhang Neil Tedeschi Tzung K. Hsiai Neil C. Chi 《Developmental biology》2014
The vertebrate heart undergoes early complex morphologic events in order to develop key cardiac structures that regulate its overall function (Fahed et al., 2013). Although many genetic factors that participate in patterning the heart have been elucidated (Tu and Chi, 2012), the cellular events that drive cardiac morphogenesis have been less clear. From a chemical genetic screen to identify cellular pathways that control cardiac morphogenesis in zebrafish, we observed that inhibition of the Rho signaling pathways resulted in failure to form the atrioventricular canal and loop the linear heart tube. To identify specific Rho proteins that may regulate this process, we analyzed cardiac expression profiling data and discovered that RhoU was expressed at the atrioventricular canal during the time when it forms. Loss of RhoU function recapitulated the atrioventricular canal and cardiac looping defects observed in the ROCK inhibitor treated zebrafish. Similar to its family member RhoV/Chp (Tay et al., 2010), we discovered that RhoU regulates the cell junctions between cardiomyocytes through the Arhgef7b/Pak kinase pathway in order to guide atrioventricular canal development and cardiac looping. Inhibition of this pathway resulted in similar underlying cardiac defects and conversely, overexpression of a PAK kinase was able to rescue the loss of RhoU cardiac defect. Finally, we found that Wnt signaling, which has been implicated in atrioventricular canal development (Verhoeven et al., 2011), may regulate the expression of RhoU at the atrioventricular canal. Overall, these findings reveal a cardiac developmental pathway involving RhoU/Arhgef7b/Pak signaling, which helps coordinate cell junction formation between atrioventricular cardiomyocytes to promote cell adhesiveness and cell shapes during cardiac morphogenesis. Failure to properly form these cell adhesions during cardiac development may lead to structural heart defects and mechanistically account for the cellular events that occur in certain human congenital heart diseases. 相似文献
994.
Alice R. Wattam Jeffrey T. Foster Shrinivasrao P. Mane Stephen M. Beckstrom-Sternberg James M. Beckstrom-Sternberg Allan W. Dickerman Paul Keim Talima Pearson Maulik Shukla Doyle V. Ward Kelly P. Williams Bruno W. Sobral Renee M. Tsolis Adrian M. Whatmore David O'Callaghan 《Journal of bacteriology》2014,196(5):920-930
Brucella species include important zoonotic pathogens that have a substantial impact on both agriculture and human health throughout the world. Brucellae are thought of as “stealth pathogens” that escape recognition by the host innate immune response, modulate the acquired immune response, and evade intracellular destruction. We analyzed the genome sequences of members of the family Brucellaceae to assess its evolutionary history from likely free-living soil-based progenitors into highly successful intracellular pathogens. Phylogenetic analysis split the genus into two groups: recently identified and early-dividing “atypical” strains and a highly conserved “classical” core clade containing the major pathogenic species. Lateral gene transfer events brought unique genomic regions into Brucella that differentiated them from Ochrobactrum and allowed the stepwise acquisition of virulence factors that include a type IV secretion system, a perosamine-based O antigen, and systems for sequestering metal ions that are absent in progenitors. Subsequent radiation within the core Brucella resulted in lineages that appear to have evolved within their preferred mammalian hosts, restricting their virulence to become stealth pathogens capable of causing long-term chronic infections. 相似文献
995.
Gabriel O. Reznik Prashanth Vishwanath Michelle A. Pynn Joy M. Sitnik Jeffrey J. Todd Jun Wu Yan Jiang Brendan G. Keenan Andrew B. Castle Richard F. Haskell Temple F. Smith Ponisseril Somasundaran Kevin A. Jarrell 《Applied microbiology and biotechnology》2010,86(5):1387-1397
Surfactants find wide commercial use as foaming agents, emulsifiers, and dispersants. Currently, surfactants are produced from petroleum, or from seed oils such as palm or coconut oil. Due to concerns with CO2 emissions and the need to protect rainforests, there is a growing necessity to manufacture these chemicals using sustainable resources In this report, we describe the engineering of a native nonribosomal peptide synthetase pathway (i.e., surfactin synthetase), to generate a Bacillus strain that synthesizes a highly water-soluble acyl amino acid surfactant, rather than the water insoluble lipopeptide surfactin. This novel product has a lower CMC and higher water solubility than myristoyl glutamate, a commercial surfactant. This surfactant is produced by fermentation of cellulosic carbohydrate as feedstock. This method of surfactant production provides an approach to sustainable manufacturing of new surfactants. 相似文献
996.
997.
Internalization of Flax Rust Avirulence Proteins into Flax and Tobacco Cells Can Occur in the Absence of the Pathogen 总被引:1,自引:0,他引:1
Maryam Rafiqi Pamela H.P. Gan Michael Ravensdale Gregory J. Lawrence Jeffrey G. Ellis David A. Jones Adrienne R. Hardham Peter N. Dodds 《The Plant cell》2010,22(6):2017-2032
Translocation of pathogen effector proteins into the host cell cytoplasm is a key determinant for the pathogenicity of many bacterial and oomycete plant pathogens. A number of secreted fungal avirulence (Avr) proteins are also inferred to be delivered into host cells, based on their intracellular recognition by host resistance proteins, including those of flax rust (Melampsora lini). Here, we show by immunolocalization that the flax rust AvrM protein is secreted from haustoria during infection and accumulates in the haustorial wall. Five days after inoculation, the AvrM protein was also detected within the cytoplasm of a proportion of plant cells containing haustoria, confirming its delivery into host cells during infection. Transient expression of secreted AvrL567 and AvrM proteins fused to cerulean fluorescent protein in tobacco (Nicotiana tabacum) and flax cells resulted in intracellular accumulation of the fusion proteins. The rust Avr protein signal peptides were functional in plants and efficiently directed fused cerulean into the secretory pathway. Thus, these secreted effectors are internalized into the plant cell cytosol in the absence of the pathogen, suggesting that they do not require a pathogen-encoded transport mechanism. Uptake of these proteins is dependent on signals in their N-terminal regions, but the primary sequence features of these uptake regions are not conserved between different rust effectors. 相似文献
998.
Sheaff AK Bennett A Hanson ED Kim YS Hsu J Shim JK Edwards ST Hurley BF 《Journal of strength and conditioning research / National Strength & Conditioning Association》2010,24(11):3112-3122
The purpose of this study was to examine the relative importance of physiological characteristics during firefighting performance, as assessed by the Candidate Physical Ability Test (CPAT). Subjects included career and volunteer firefighters aged 18-39 (N = 33). Upper- and lower-body strength, muscle endurance, lower body muscle power, body composition analysis, aerobic capacity, anaerobic fitness, and the heart rate (HR) and blood pressure response to stair climbing were assessed to determine the physiological characteristics of the subjects. To quantify firefighting performance, the CPAT was administered by members of the fire service. Absolute and relative mean power during the Wingate anaerobic cycling test (WAnT), relative peak power during the WAnT, and absolute maximal oxygen uptake (VO2max) were significantly higher in those who passed the CPAT (N = 18), compared to those who failed (N = 15; p < 0.01). Mean power during the WAnT, fatigue index during WAnT, absolute VO2max, upper body strength, grip strength, and the HR response to stair climbing were significantly related to CPAT performance time (p < 0.01). Absolute VO2max and anaerobic fatigue resistance during WAnT best predicted CPAT performance (Adj. R2 = 0.817; p < 0.001). Performance on the ceiling breach and pull was the only CPAT task that was not significantly related to the physiological characteristics assessed. Measures of anaerobic and cardiovascular fitness best predict overall CPAT performance, and individual task performance. Remedial programs aimed at improving firefighting performance should target anaerobic and aerobic fitness qualities. 相似文献
999.
Sosa MS Lopez-Haber C Yang C Wang H Lemmon MA Busillo JM Luo J Benovic JL Klein-Szanto A Yagi H Gutkind JS Parsons RE Kazanietz MG 《Molecular cell》2010,40(6):877-892
While the small GTPase Rac1 and its effectors are well-established mediators of mitogenic and motile signaling by tyrosine kinase receptors and have been implicated in breast tumorigenesis, little is known regarding the exchange factors (Rac-GEFs) that mediate ErbB receptor responses. Here, we identify the PIP(3)-Gβγ-dependent Rac-GEF P-Rex1 as an essential mediator of Rac1 activation, motility, cell growth, and tumorigenesis driven by ErbB receptors in breast cancer cells. Notably, activation of P-Rex1 in breast cancer cells requires the convergence of inputs from ErbB receptors and a Gβγ- and PI3Kγ-dependent pathway. Moreover, we identified the GPCR CXCR4 as a crucial mediator of P-Rex1/Rac1 activation in response to ErbB ligands. P-Rex1 is highly overexpressed in human breast cancers and their derived cell lines, particularly those with high ErbB2 and ER expression. In addition to the prognostic and therapeutic implications, our findings reveal an ErbB effector pathway that is crucial for breast cancer progression. 相似文献
1000.
Ian G. Stiell Catherine M. Clement Jeremy M. Grimshaw Robert J. Brison Brian H. Rowe Jacques S. Lee Amit Shah Jamie Brehaut Brian R. Holroyd Michael J. Schull R. Douglas McKnight Mary A. Eisenhauer Jonathan Dreyer Eric Letovsky Tim Rutledge Iain MacPhail Scott Ross Jeffrey J. Perry Urbain Ip Howard Lesiuk Carol Bennett George A. Wells 《CMAJ》2010,182(14):1527-1532