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1.
Novel mixed valence states have been obtained by the treatment of cobaltous ferrocyanides (Co+2FeII) and ferricyanides (Co+2FeIII) in an ozone flow. The CN stretching bands occur at 2085 cm–1 for Co+2FeII and at 2160 cm–1 for Co+2FeIII. After the ozonization process of Co+2FeII, an intense band approximately at 2125 cm–1 is detected. This intermediate band must correspond to a mixed valence state of the type: FeII–CN–Co2+–NC–FeIII Mössbauer spectra recorded in situ during the ozonization of Co+2FeII show the presence of two components: a doublet with isomer shift and quadrupole splitting values close to the cobalti ferricyanide and a very broad line for the mixed valence state. From the Mössbauer and infrared spectra of the aged samples of the Co+2FeII after ozonization, a relaxation process to the initial state of the samples is observed but the mixed valence state is stable.  相似文献   
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Binding of steroid hormones is inhibited by protease inhibitors and substrates. The protease inhibitors phenylmethyl sulphonylfluoride, tosyl-lysine chloromethyl ketone, and tosylamide-phenylethyl-chloromethyl ketone and the protease substrates tosyl arginine methyl ester and tryptophan methyl ester eliminate specific binding of aldosterone, dexamethasone, dihydrotestosterone, estrogen, and progesterone to their respective receptors. These protease inhibitors and substrates also inhibit binding of progesterone to the 20,000 molecular weight mero-receptor formed from the progesterone receptor in chick oviduct. The binding of estradiol to rat alpha-fetoprotein is inhibited by the protease inhibitors and substrates but not by tryptophan or tryptophan amide, indicating the importance of an ester structure in the inhibition of steroid binding. Our results suggest that all steroid hormone receptors have a site with both common structural features and a role in the regulation of steroid hormone binding.  相似文献   
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Production of the end products of polygalacturonic acid degradation on a large scale was done by reacting free galacturonic acid with Bacillus pumilus polygalacturonic acid transeliminase (PATE, EC 4.2.2.2) to obtain a mixture of the barium salts of several oligouronides. Small amounts of the unsaturated oligouronides were separated by paper chromatography. Large quantities of unsaturated oligouronides were separated on a AG-1-X8 (formate) column by applying a sample of mixed oligouronides and stepwise elution was carried out with sodium formate buffer (pH 4.7). The unsaturated oligouronides were identified on the basis of chromatographic mobilities, Sephadex gel filtration data, COOH/CHO ratio, thiobarbituric acid-reacting material, bromine uptake, and chemical and enzymatic degradation data as unsaturated tri-, tetra-, and hexagalacturonic acids. The chemical degradation of these unsaturated oligouronides, done with 6 N HCl by heating at 100 degrees for 30 min, gave qualitatively identical products of hydrolysis. These products compared with authentic standards, were identified as galacturonic acid, formic acid, 5-formyl-2-furancarboxylic acid, and 2-furancarboxylic acid. Analysis of the enzymatic breakdown products of the higher unsaturated uronides showed that a minimum of four galacturonic acid units was required for the action of purified endo-PATE from B. pumilus. The unsaturated trimer was not attacked, thus accounting for its accumulation as the major end product of polygalacturonate degradation by this enzyme.  相似文献   
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The effect of surface tension on the lipid bilayer membrane is a question that has drawn considerable research effort. This interest has been driven both by the desire to determine the surface tension effects on the lipid bilayer and from the suggestion that adding finite surface tension to a small membrane system may provide more realistic lipid properties in molecular dynamics simulations. Here, the effect of surface tension on a palmitololelylphosphatidylcholine (POPC) bilayer membrane containing a four-helix transmembrane alamethicin peptide bundle is investigated. Simulations of 10 ns were undertaken for two different ensembles, NPT and NP(z)gammaT with a surface tension, gamma, of 20 mN m(-1) per interface, which is near the pore-forming region. The significance of differences between the tension-free and surface tension simulations was determined using nonparametric statistical analysis on replicate simulations with different initial conditions. The results suggest that, when the membrane is under surface tension, the peptide helical structure is perturbed from that in the tension-free state but that the bundle conformation is more stable than that in the tension-free state, with hydrogen bonding playing an important stabilizing role. Surface tension counteracts the influence of the transmembrane helix bundle on nearby lipid order, making the lipid order more uniform throughout the membrane in the tension state. Conversely, the lipid mobility was less uniform in the tension state, with lipids far from the bundle being significantly more mobile than those near the bundle. One general implication of the results is that surface tension can affect the membrane nonuniformly, in that the properties of lipids near the peptide are different from those further away.  相似文献   
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A system for measuring atomic fluorescence of atoms produced via an electrically-heated graphite filament in a flame (acetylene/air or acetylene/nitrous oxide) and excited with a 300-W Eimac xenon are lamp is described. The experimental system also included wavelength modulation for background emission/fluorescence/scatter correction and an optically-triggered electronic integrator for efficient monitoring of the analyte fluorescence signal. Copper, aluminum and molybdenum were determined in jet engine lubricating oil samples (1 μl) with no pretreatment. The determinations are evaluated with respect to the accuracy and repeatability criteria of the U.S. Joint Oil Analysis Program.  相似文献   
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