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Natochin M Gasimov KG Moussaif M Artemyev NO 《The Journal of biological chemistry》2003,278(39):37574-37581
Three cytoplasmic loops in the G protein-coupled receptor rhodopsin, C2, C3, and C4, have been implicated as key sites for binding and activation of the visual G protein transducin. Non-helical portions of the C2- and C3-loops and the cytoplasmic helix-8 from the C4 loop were targeted for a "gain-of-function" mutagenesis to identify rhodopsin residues critical for transducin activation. Mutant opsins with residues 140-148 (C2-loop), 229-244 (C3-loop), or 310-320 (C4-loop) substituted by poly-Ala sequences of equivalent lengths served as templates for mutagenesis. The template mutants with poly-Ala substitutions in the C2- and C3-loops formed the 500-nm absorbing pigments but failed to activate transducin. Reverse substitutions of the Ala residues by rhodopsin residues have been generated in each of the templates. Significant ( approximately 50%) restoration of the rhodopsin/transducin coupling was achieved with re-introduction of residues Cys140/Lys141 and Arg147/Phe148 into the C2 template. The reverse substitutions of the C3-loop residues Thr229/Val230 and Ser240/Thr242/Thr243/Gln244 produced a pigment with a full capacity for transducin activation. The C4 template mutant was unable to bind 11-cis-retinal, and the presence of Asn310/Lys311 was required for correct folding of the protein. Subsequent mutagenesis of the C4-loop revealed the role of Phe313 and Met317. On the background of Asn310/Lys311, the inclusion of Phe313 and Met317 produced a mutant pigment with the potency of transducin activation equal to that of the wild-type rhodopsin. Overall, our data support the role of the three cytoplasmic loops of rhodopsin and suggest that residues adjacent to the transmembrane helices are most important for transducin activation. 相似文献
23.
Three innovative and complementary morphological approaches were employed to study the T cell/antigen presenting cell (APC) interaction: (i) high resolution three-dimensional confocal microscopy of the T cell-APC contact site; (ii) time lapse video recording in living T cells of [Ca2+]I and changes in distribution of various GFP fusion proteins with TCR/CD3-zeta complex associated- and other signaling components; (iii) measurement of lateral TCR mobility and that of recruited signaling components using techniques based on fluorescence recovery after photo-bleaching. These approaches were combined with biochemical and functional experiments to investigate two principal issues: (A) Recruitment and the three-dimensional arrangement of receptors and signaling components at the contact site between human CD4+ T lymphocytes and APCs, (B) Structure of the immunological synapse formed at the contact site between cytotoxic T lymphocytes (CTLs) and target cells. We discuss evidence indicating that TCR engagement and triggering can occur in the absence of large-scale molecular segregation into the T cell-APC contact site. Taken together our results indicate that although not required for TCR engagement and triggering, formation of the IS is important to reinforce TCR-mediated signal transduction and achieve full T cell activation. 相似文献
24.
Gianni M Kopf E Bastien J Oulad-Abdelghani M Garattini E Chambon P Rochette-Egly C 《The Journal of biological chemistry》2002,277(28):24859-24862
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Hong Zhu Hee Yun Suk Raymond Y. L. Yu Deborah Brancho Opeyemi Olabisi Teddy T. C. Yang XiaoYong Yang Jialin Zhang Mustapha Moussaif Jorge L. Durand Linda A. Jelicks Ja-Young Kim Philipp E. Scherer Philippe G. Frank Michael P. Lisanti John W. Calvert Mark R. Duranski David J. Lefer Elaine Huston George S. Baillie Miles D. Houslay Jeffrey D. Molkentin Jianping Jin Chi-Wing Chow 《Molecular and cellular biology》2010,30(18):4379-4390
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Badiaa Essghaier Mustapha Rouaissi Abdellatif Boudabous Haissam Jijakli Najla Sadfi-Zouaoui 《World journal of microbiology & biotechnology》2010,26(6):977-984
This paper is the first to investigate the production and partial characterization of the chitinase enzyme from a moderately
halophilic bacterium Planococcus rifitoensis strain M2-26, earlier isolated from a shallow salt lake in Tunisia. The impact of salt, salinity concentration, pH, carbon
and nitrogen sources on chitinase production and activity have been determined. This is the first report on a high salt-tolerant
chitinase from P. rifitoensis, since it was active at high salinity (from 5 to 30% NaCl) as well as in the absence of salt. This enzyme showed optimal
activity at 70°C and retained up to 82 and 66% of its original activity at 80 or 90°C, respectively. The activity of the enzyme
was also shown over a wide pH range (from 5 to 11). For characterization of the enzyme activity, the chitinase secreted in
the culture supernatant was partially purified. The preliminary study of the concentrated dialysed supernatant on native PAGE
showed at least three chitinases produced by strain M2-26, with highest activity approximately at 65 kDa. Thus, the thermo-tolerant
and high salt-tolerant chitinases produced by P. rifitoensis strain M2-26 could be useful for application in diverse areas such as biotechnology and agro-industry. 相似文献
28.
Martin K. Rono Miranda M. A. Whitten Mustapha Oulad-Abdelghani Elena A. Levashina Eric Marois 《PLoS biology》2010,8(7)
When taking a blood meal on a person infected with malaria, female Anopheles gambiae mosquitoes, the major vector of human malaria, acquire nutrients that will activate egg development (oogenesis) in their ovaries. Simultaneously, they infect themselves with the malaria parasite. On traversing the mosquito midgut epithelium, invading Plasmodium ookinetes are met with a potent innate immune response predominantly controlled by mosquito blood cells. Whether the concomitant processes of mosquito reproduction and immunity affect each other remains controversial. Here, we show that proteins that deliver nutrients to maturing mosquito oocytes interfere with the antiparasitic response. Lipophorin (Lp) and vitellogenin (Vg), two nutrient transport proteins, reduce the parasite-killing efficiency of the antiparasitic factor TEP1. In the absence of either nutrient transport protein, TEP1 binding to the ookinete surface becomes more efficient. We also show that Lp is required for the normal expression of Vg, and for later Plasmodium development at the oocyst stage. Furthermore, our results uncover an inhibitory role of the Cactus/REL1/REL2 signaling cassette in the expression of Vg, but not of Lp. We reveal molecular links that connect reproduction and immunity at several levels and provide a molecular basis for a long-suspected trade-off between these two processes. 相似文献
29.
Cationic lipids are efficient tools to introduce nucleic acids and proteins into cells. Elucidation of the mechanism and cellular pathways associated with such transport has been relatively tedious, even though significant progress has been made in the characterization of the intracellular trafficking of lipid/DNA complexes. Surprisingly little is known about the effects of these delivery vectors on cell functioning. In this report, we show that both cationic lipids and cationic lipid/DNA complexes mobilize the intracellular calcium. Removal of extracellular calcium did not significantly abolish this effect and preincubating cells with thapsigargin led to a decrease in [Ca2+]i, indicating that calcium was released mainly from internal calcium stores sensitive to thapsigargin. Pretreatment of the cells with the phospholipase C inhibitor U73122, blocked the [Ca2+]i rise, suggesting an inositol dependent mechanism. 相似文献
30.