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1.
人体单臂间歇运动对发汗调定点的影响 总被引:2,自引:0,他引:2
本工作系在微小气候相对恒定条件下,对10名健康男青年每人进行四项实验。实验 Ⅰ 为测定双侧腿足浸入43℃水中,诱发左前臂屈侧显现定量汗点时的口腔温度(舌下)阈值,作为发汗调定点参考值(ToSSP);实验 Ⅱ 为 Ⅰ 附加右臂间歇轻负荷运动(77W)时测定 ToSSP,部分对象还记录了皮肤电反应;实验 Ⅲ、Ⅳ 为 Ⅰ、Ⅱ 均附加4.5m/s 气流(22—25℃)直吹头面部,再分别测定 ToSSP。实验 Ⅰ 与 Ⅱ 同体对照22人次,Ⅲ 与 Ⅳ 同体对照24人次。结果表明,实验 Ⅱ、Ⅳ 的 ToSSP 均值及其潜伏期均值分别较 Ⅰ、Ⅲ 者降低(P<0.01)或缩短(P<0.001);Ⅰ、Ⅱ间的 ToSSP 均值差、潜伏期均值差,分别与 Ⅲ、Ⅳ 之间者无显著差异(P>0.2);Ⅱ、Ⅳ 的ToSSP 均值各与其实验开始前的口温均值亦无明显差异(P>0.5)。此结果支持运动时体温调定点下降的论点,并提示在研究体温调定点活动时,以 ToSSP 为指标较用发汗速率为优越,因 ToSSP 不为许多干扰因素所影响。 相似文献
2.
N-terminal half of CheB is involved in methylesterase response to negative chemotactic stimuli in Escherichia coli. 总被引:3,自引:1,他引:2
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The chemotactic receptor-transducer proteins of Escherichia coli are responsible for directing the swimming behavior of cells by signaling for either straight swimming or tumbling in response to chemostimuli. The signaling states of these proteins are affected not only by the concentrations of various stimuli but also by the extent to which they have been methylated at specific glutamyl residues. The activities of a chemotaxis-specific methyltransferase (CheR) and a chemotaxis-specific methylesterase (CheB) are regulated in response to chemotactic stimuli to enable sensory adaptation to unchanging levels of stimuli by appropriately shifting the signaling states of the transducer proteins. For CheB this regulation involves a feedback loop that requires some of the components making up the chemotactic signal transduction machinery of the cell. This feedback loop causes the methylesterase activity of CheB to decrease transiently in response to attractant stimuli and to increase transiently in response to negative stimuli (repellent addition or attractant removal). In this report we demonstrate that the methylesterase response to negative stimuli involves the N-terminal half of the CheB protein, whereas the response to positive stimuli does not require this segment of the protein. Both aspects of the methylesterase response to positive stimuli does not require this segment of the protein. Both aspects of the methylesterase response require CheA. In addition, we demonstrate that mutant forms of CheB lacking methylesterase activity can adversely affect the swimming behavior and chemotactic ability of cells and can markedly diminish modulation of the wild-type methylesterase activity in response to negative stimuli. The significance of these results is discussed in relation to the recent demonstration of phosphoryl transfer from CheA to CheB (J. F. Hess, K. Oosawa, N. Kaplan, and M. I. Simon, Cell 53:79-87, 1988) and the discovery of sequence homology between the N-terminal half of CheB and CheY (A. Stock, D. E. Koshland, Jr., and J. Stock, Proc. Natl. Acad. Sci. USA 82:7989-7993, 1985). 相似文献
3.
Nuclear magnetic resonance observation and dynamics of specific amide protons in T4 lysozyme 总被引:2,自引:0,他引:2
We have produced T4 lysozyme using a bacterial expression system which allows efficient incorporation of isotopically labeled amino acids in lysozyme. By using conditions that repress the expression of various transaminases, we have incorporated 15N-labeled amino acid into the five phenylalanine residues of the protein. The relatively large spin--spin coupling (87 +/- 3 Hz) between the 15N nucleus and the phenylalanine amide protons may then be exploited in a variety of ways to selectively observe the five phenylalanine amide proton resonances. These include a simple "echo difference" technique which displays the amide proton resonances in one dimension and a "forbidden echo" technique [Bax, A., Griffey, R. H., & Hawkins, B.L. (1983) J. Magn. Reson. 55, 301-335] which gives two-dimensional information allowing the proton and 15N chemical shifts of each amide to be determined. With these approaches, all five phenylalanine amide protons give resolved resonances. Deuterium exchange experiments demonstrate that three of the five resonances are slow to exchange (half-times of about 1 week at pH 5.5 and 4 degrees C) while the other two are rapid with complete exchange in hours or less. These observations correlate well with the secondary structure of the protein which shows three residues in alpha-helical regions and two residues in surface-exposed environments. This approach of isotopic substitution on nitrogen or carbon atoms is of general utility and should allow virtually any proton on a protein of molecular weight 20 000 or thereabout to be selectively observed. 相似文献
4.
Two conformational states of the coat protein of the filamentous bacteriophage M13 have been detected in detergent solution by using magnetic resonance techniques. When 3-fluorotyrosine is incorporated in place of the two tyrosine residues in the protein, four 19F nuclear magnetic resonance signals are observed, two for each conformer of the protein. The equilibrium between the two forms can be modulated by pH, temperature, and detergent structure. The rate of interconversion of the isomers is rapid on the minutes time scale but is slow relative to the T1 relaxation time of the fluorine resonances of approximately 50 ms. The conformational change between the conformers results in the perturbation of a basic residue in the protein such that this group has a pKa of approximately 9.5 in one state which shifts to 10.5 or more in the other conformational state. The temperature dependence of the equilibrium suggests an enthalpy difference of about 10 kcal/mol which is offset by entropy to give nearly zero free energy difference between the states at pH 8.3 in deoxycholate solution at room temperature. This suggests a substantial reorganization of the noncovalent interactions defining the two conformational states. The conformational equilibrium is strongly dependent on detergent structure and the presence of phospholipid in the detergent micelle. The results are not consistent with a strong, specific lipid binding to the protein but appear to be consistent with a more general effect of the overall micelle structure on the conformational state of the protein. 相似文献
5.
R. Christen R.W. Schackmann F.W. Dahlquist B.M. Shapiro 《Experimental cell research》1983,149(1):289-294
31P-NMR has been used to estimate the internal pH (pHi) of sperm from the sea urchin Strongylocentrotus purpuratus. The values for pHi obtained from the chemical shift of inorganic phosphate agree well with those obtained from amine accumulation. At low pHi, when sperm are quiescent (immotile and non-respiring), they accumulate phosphocreatine (PCr), but have a low level of inorganic phosphate (Pi). Conversely, when the pHi is elevated, sperm respiration and motility are activated, PCr is decreased and Pi is increased. This change is reversible upon decrease of the pHi, whereupon respiration and motility are arrested, Pi disappears and PCr increases. We conclude that the overall balance of energy metabolism, and thus the phosphate potential, of sea urchin sperm are under the control of the pHi. 相似文献
6.
7.
从假菠萝麻叶汁中用乙醇分部沉淀法得到一种蛋白酶,对酪蛋白有强烈的水解活性,经Sephadex G-100柱层析和SP-Sephadex C-50离子交换柱层析等步骤纯化,可得到六角形结晶。结晶酶液经PAGE圆盘电泳,每条胶柱上只显示一条蛋白带,其活性在pH4。5-10、55℃范围内较稳定,最适pH8.5最适温度50℃,Km(酪蛋白)值为0.185%(W/V)。用SDS-PAGE和Sephadex 相似文献
8.
本研究旨在建立一种简便、快捷、可直观检测小反刍兽疫病毒(peste des petits ruminants virus,PPRV)抗体的检测方法。将pET-32a-N重组质粒转化至大肠杆菌(Escherichia coli) Rosetta(DE3)感受态细胞中进行诱导表达,以纯化的PPRVN蛋白免疫8周龄BALB/c小鼠,取其脾细胞与SP2/0骨髓瘤细胞进行融合,间接酶联免疫吸附试验(enzyme-linked immunosorbent assays, ELISA)筛选及亚克隆,获得了抗PPRV N蛋白的单克隆抗体。将PPRV N蛋白分别作为金标抗原及检测线(T线)包被抗原、单克隆抗体作为质控线(C线)包被抗体,组装成检测PPRVN蛋白抗体的胶体金免疫层析试纸条。结果显示:成功获得1株能稳定分泌抗N蛋白抗体的杂交瘤细胞株,命名为1F1;间接ELISA检测1F1腹水效价为1:128000;亚类鉴定结果为IgG1,轻链为kappa链。Westernblotting结果显示,1F1能与PPRV N蛋白特异性结合;间接免疫荧光(indirect immunofluorescent ass... 相似文献
9.
目的 鼻咽癌是一种来源于鼻咽上皮的恶性肿瘤,其临床特征之一是易发生淋巴转移,但是目前鼻咽癌转移的分子机制尚未阐明。circPVT1是由PVT1基因2号外显子反向拼接形成的环状RNA (circRNA),在多种肿瘤中表达上调,本文探讨了circPVT1在鼻咽癌侵袭迁移中的作用和分子机制。方法 通过RT-qPCR检测circPVT1及其下游miRNA和FSCN1在鼻咽癌细胞的表达情况,Transwell和划痕愈合实验检测circPVT1对鼻咽癌细胞侵袭迁移的影响,RNA pull-down实验检测circPVT1结合的miRNA,双荧光素酶报告实验检测miR-24-3p和let-7a-5p靶向抑制FSCN1 mRNA表达。结果 在鼻咽癌细胞中过表达circPVT1可以促进鼻咽癌细胞侵袭迁移,而敲低circPVT1则可以抑制鼻咽癌细胞的侵袭迁移。进一步研究发现,circPVT1可以通过竞争性吸附miR-24-3p和let-7a-5p,上调FSCN1的表达,从而促进鼻咽癌细胞的侵袭迁移。结论 circPVT1通过miR-24-3p/let-7a-5p/FSCN1轴促进鼻咽癌细胞侵袭迁移,证实c... 相似文献
10.
Interactions between protein components of the chemotaxis mechanism in Escherichia coli were investigated by using the cleavable cross-linking reagent, dithiobis(succinimidyl propionate). Two methods were used to allow detection of chemotaxis-specific proteins in intact cells. The first method was to program their synthesis in the presence of [35S]methionine using lambda E. coli hybrid phages which carry the chemotaxis genes. The second method was to label endogenous methyl-accepting chemotaxis proteins (MCP's), with the methyl donor S-adenosyl-L-[methyl-3H]methionine, after permeabilizing the cells with EGTA. Physical associations between proteins were analyzed, after cross-linking, by two dimensional NaDodSO4-polyacrylamide gel electrophoresis. Both labeling methods demonstrate that MCP I and MCP II exist as functional tetramers. Other proteins involved with chemotaxis were found to form dimers and higher polymers. Phage-directed products of cheW, cheX, motA, and cheA formed dimers. CheB and hag products formed multimers. A number of apparent interactions between different gene products were detected as well. Products of cheB, cheW, cheZ, motA, and motB were found to form complexes with other gene products. Included are results consistent with interactions between the products of cheB and cheZ. 相似文献