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1.
Microemulsions (dispersions of water droplets, typical radius about 10 nm, in oil) show a particular percolation pattern, a so-called dynamical percolation. Predictions of scaling theory and Monte Carlo simulations were compared with experimental static and frequency dependent conductivity data. The latter gives evidence of two different time scales of charge transport.Dedicated to Professor Harry Thomas on the occasion of his 60th birthday 相似文献
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Oleinikova A Smolin N Brovchenko I Geiger A Winter R 《The journal of physical chemistry. B》2005,109(5):1988-1998
The formation of spanning hydrogen-bonded water networks on protein surfaces by a percolation transition is closely connected with the onset of their biological activity. To analyze the structure of the hydration water at this important threshold, we performed the first computer simulation study of the percolation transition of water in a model protein powder and on the surface of a single protein molecule. The formation of an infinite water network in the protein powder occurs as a 2D percolation transition at a critical hydration level, which is close to the values observed experimentally. The formation of a spanning 2D water network on a single rigid protein molecule can be described by adapting the cluster analysis of conventional percolation studies to the characterization of the connectivity of the hydration water on the surface of finite objects. Strong fluctuations of the surface water network are observed close to the percolation threshold. Our simulations also furnish a microscopic picture for understanding the specific values of the experimentally observed hydration levels, where different steps of increasing mobility in the hydrated powder are observed. 相似文献
4.
Thomas Geiger Richard Nottenberg Mary-Lou Plaprat Michael Grtzel 《Helvetica chimica acta》1982,65(8):2507-2516
Light-induced interfacial electron transfer from two p-InP electrodes differing in the amount of majority carrier doping to a number of electron relays ( R ) dissolved in aqueous solution was investigated. The material with the lower carrier density (0.71 × 1018 cm?3) exhibited much better wavelength response and quantum yield for electron transfer than the electrode doped with 2.3 × 1018 cm?3 charge carriers. Using cobalt (III) sepulcrate, Co (sep)3+, as an electron relay a polychromatic light to electrical energy conversion efficiency of 18% was obtained. The potential of this relay for use in a regenerative photoelectrochemical cell is briefly discussed. 相似文献
5.
Zirconium can be determination fluorimctrically with morin in 2M hydrochloric acid in the presence of such elements as Al, Be, Ga, Sb, Sn, Th and U, which fluorcsce much less strongly under the conditions, by measuring the fluorescence intensity before and after adding ethylenediaminetetraacetic acid. This substance destroys the fluorescence of zirconium only and the difference in fluorescence intensities corresponds to the concentration of zirconium in solution. The determination of zirconium in the presence of aluminum has especially been studied. Satisfactory accuracy can be obtained even when Al/Zr = 10,000, if the proper morin concentration is used. Iron docs not interfere if reduced to the ferrous state with mercap oacetic acid, Zirconium can be determined in silicate rocks without any separations except those made automatically in tlie sodium carbonate decomposition. Niobium and tantalum should not exceed 0.05%. 相似文献
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Martin Winterwerber Rouzita Geiger Hans-Hartwig Otto 《Monatshefte für Chemie / Chemical Monthly》2006,137(10):1321-1347
Summary. Cyanomethanesulfonyl chloride was reacted with amines yielding cyanomethanesulfonamides which could be transformed into alkoxymethylidene
and aminomethylidene derivatives. The reaction of alkoxymethylidene derivatives with phenylhydrazine resulted in the formation
of 5-aminopyrazol-4-sulfonamides, whereas from cyanomethanesulfonamides via the N-hydroxyamidine derivatives and their reaction with esters 1,2,4-oxadiazol-3-methanesulfonamides became accessible. Nitrosation
of cyanomethanesulfonamides yielded 2-hydroxyimino derivatives which were then transformed into 2-hydroxyimino N-hydroxyamidine derivatives, and finally cyclized into 4-amino-1,2,5-oxadiazol-3-sulfonamides. On the other hand diazotation
of cyanomethanesulfonamides gave the 2-arylhydrazono derivatives, which after transformation into N-hydroxyamidine derivatives gave by reaction with POCl3 5-amino-1,2,3-triazol-4-sulfonamides. Finally, the reaction between cyanomethanesulfonamides and formamidinium acetate opened
an easy access to 4-aminopyrimidine-5-sulfonamides, which could be transformed by trialkyl orthoformiates into substituted
pyrimidino[4,5-e][1,2,4]thiadiazine derivatives. All intermediates as well as transformation products of the heterocyclic systems were isolated
and well characterized. Mechanisms were discussed, and the stereochemistry, when necessary and possible, was elucidated. 相似文献
8.
Proton relaxation time measurements are performed for 6m aqueous solutions of7LiI and6LiI in D2O containing small amounts of H2O. The measurements are done at low temperatures and yield maxima of the relaxation rate plotted against 1/T. From the maxima of the relaxation rates, proteon-I– and proton-Li+ distances in the first coordination sphere of the ions are determined, and from the knowledge of the ion-water oxygen distance it is shown that for iodide a somewhat broadened H-bonded configuration is valid and that for Li+ the electric dipole orientation deviates from the radial direction. In order to test the reliability of the method a proton-127I interaction study is also performed in KI solution in glycerol. The I-H distance obtained is in satisfactory agreement with that found in the aqueous system. 相似文献
9.
J. F. Geiger P. Beckmann K. D. Schierbaum W. Göpel 《Fresenius' Journal of Analytical Chemistry》1991,341(1-2):25-30
Summary We report about interaction processes between palladium (Pd) and tin dioxide (SnO2) studied with various surface spectroscopic techniques. Total sputter yields necessary for absolute depth calibration in SIMS are determined for SnO2. Clustering of palladium occurs at low temperatures. Small changes in the XPS relative core level intensities of Pd and Sn allow to determine cluster sizes. Oxidation of Pd in the presence of oxygen at T470 K is a prerequisite for diffusion of Pd2+ ions into SnO2 layers. The latter process is confirmed and described quantitatively by evaluating the SIMS and SNMS measurements. 相似文献
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