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831.
832.
833.
Jean Grandjean Pierre Laszlo 《Biochemical and biophysical research communications》1982,104(4):1293-1297
Transport of Pr3+ across phosphatidylcholine vesicles, monitored through 31P nmr, is first-order in monensin (), second-order in etheromycin () or in lasalocid A (). When and (or and ) are incorporated in 1:1 ratio into the lipidic phase, transport is faster than with each ionophore alone. For instance, assuming that the complexes .Pr3+., .Pr3+., and .Pr3+ are equiprobable, they effect transport at intrinsic relative rates of 1, 2, and 13.5, a remarkable synergism is set up. 相似文献
834.
What fraction of the proliferative pool cells in epithelial tissues functions as stem cells is still uncertain. Earlier models, based on little or no good evidence, have assumed that this fraction is close to one. Recently there have been developments suggesting that the fraction of stem cells is low, with considerable cell production being attributable to division in short-lived transit proliferative cells. This brings epithelial tissues into line with haematopoiesis and spermatogenesis. This review considers these newer developments and emphasises the similarities between three epithelial regions (skin, tongue and intestine) and bone marrow and testis. Some of the models currently under discussion relate cell position, division polarity, protection of stem genome and hence carcinogenesis. Some of the implications of these models are discussed. 相似文献
835.
Some cytotoxic drugs cause translocation of nucleophosmin/B23 and other nucleolar proteins to the nucleoplasm. The present study shows that these drugs caused a similar translocation of RH-II/Gu, a nucleolar RNA helicase. Other nucleolar proteins including p120, UBF, RNA polymerase I large subunit, fibrillarin, p40, and Ren-1 did not translocate. A 2-h treatment of MCF-7 breast cancer cells with 0.008 or 0.16 μMactinomycin D resulted in translocation of RH-II/Gu to the nucleoplasm; these effects were not reversed by 100 μMguanosine. The effects of 0.008 μMactinomycin D, but not 0.16 μMactinomycin D, on the translocation of RH-II/Gu were reversed when the drug was removed. However, the effects of 0.008 or 0.16 μMactinomycin D on the translocation of nucleophosmin/B23 were not reversible. The translocation effects of 50 μMtoyocamycin on RH-II/Gu were reversed when the drug was replaced with fresh medium. RH-II/Gu mostly relocalized to the nucleoli within 15 min after toyocamycin was withdrawn; only partial relocalization of nucleophosmin/B23 occurred 40 h after removal of the drug. The effects of toyocamycin were not blocked by 100 μMguanosine. Mycophenolic acid (50 μM,2-h treatment) caused partial translocation of RH-II/Gu; this effect was slowly reversed upon drug removal and was inhibited by 100 μMguanosine, in a manner similar to the effects of mycophenolic acid on the localization of nucleophosmin/B23. This study shows similarities and differences in the drug-induced translocation and relocalization of RH-II/Gu and nucleophosmin/B23. Analysis of translocation of specific nucleolar proteins may offer a quantitative approach to assessment of potency and duration of effects of cytotoxic agents. 相似文献
836.
837.
Use of a fluorescent probe for the intravesicular pH shows that synergisms previously observed in Pr3+ transport across phosphatidylcholine vesicles are explained by an increase in the proton counter-transport. 相似文献
838.
Laszlo G. Harsing Jr. Henry Sershen Sylvester E. Vizi Abel Lajtha 《Neurochemical research》1992,17(7):729-734
Mouse striatum was incubated with [3H]dopamine ([3H]DA) and superfused with and the tritium efflux induced by nicotine, electrical stimulation, or simultaneous nicotine and electrical stimulation was measured, to characterize the role of different Ca2+ channels in the transmitter release. Nicotine stimulation and electrical stimulation exerted additive effects on tritium efflux. Separation of the released radioactivity on alumina columns indicated that nicotine or electrical stimulation increases the release of [3H]DA and that the outflow of3H-labeled metabolites was similar with the two different stimulation procedures. Removal of Ca2+ from the superfusate resulted in a marked reduction in the tritium release evoked by nicotine, whereas the electrical stimulation-evoked tritium release was completely dependent on external Ca2+. The L-and N-type calcium channel blockers omega-conotoxin GVIA and Cd2+ inhibited the tritium release from the striatum evoked by either nicotine or electrical stimulation, whereas the L-type and T-type channel blockers diltiazem and Ni2+ did not alter release of [3H]DA. We conclude that N-type voltage-sensitive Ca2+ channels participate in striatal dopamine release, and we speculate that nicotinic receptor-operated ion channels permeable to cations such as Ca2+ and N-type voltage-sensitive calcium channels may simultaneously open up, and they additively increase free intracellular Ca2+ concentration. 相似文献
839.
Laszlo Vadas Harry S. Prihar Balappa K. Pugashetti David Sidney Feingold 《Analytical biochemistry》1981,114(2):294-298
A method has been developed for the quantitative determination of the relative proportions of d-mannuronic and l-guluronic acids in alginic acid. To obtain homogeneous reaction conditions the viscosity of the alginic acid sample was first decreased by limited hydrolysis with mineral acid. The carboxyl groups were then esterified by reaction with 1-ethyl-3-[3-(dimethylamino)propyl]-carbodiimide, and reduced with sodium borohydride. The resulting hexosans were converted by acid hydrolysis to d-mannose and an equilibrium mixture of l-gulose and 1,6-anhydro-l-gulose. These were treated with sodium borohydride; the 1,6-anhydro-l-gulose was not reduced whereas d-mannose and l-gulose were converted to d-mannitol and d-glucitol. The hexitols were estimated by gas-liquid chromatography as the n-butane boronic acid esters, and the relative proportions of the uronic acids in the alginic acid were calculated by taking into account the equilibrium ratio of l-gulose and 1,6-anhydro-l-gulose. The method can be used to analyze as little as 2 mg of alginic acid. 相似文献
840.