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951.
952.
Isotherms of surface pressure against surface area for a polyvinylacetate (PVAc) film at the air-water interface were determined at 20.52°C. Measurements of surface moment, hysteresis, and pressure relaxation in a constant area were subsequently conducted at appropriate area regions for elucidation of the correlation of properties and conformations of PVAc film. It is concluded that the film is stable and exhibits a perfectly reversible compression in the areas larger than 13 Å2/repeat-unit but assumes three different conformations for three regions (70-42), (42-25), and (25-13) Å2/repeat-unit, respectively. Finally, a twisting chain loop model is proposed for the interpretation of hysteresis and pressure relaxation occurring in the areas near and in the collapse region. 相似文献
953.
The effect of interaction between solvent and three different kinds of printed wastepaper has been studied. The solubility parameter of the solvent was found to be among the most important in order to obtain an optimum ink-fiber interfacial swelling, necessary for de-inking wastepaper. The degree of ink-fiber interfacial swelling was qualitatively estimated by examining the dispersity of ink particles using an optical microscope. FT-IR analyses were carried out to correlate the degree of dispersion and the ink composition in the printed wastepapers studied. The effect of a selective swelling solvent on the de-inking characteristics of a mixture of old wastepapers was investigated. The solvent treatment of these wastepapers prior to flotation de-inking failed to add any positive effect on the brightness of the de-inked pulp. On the other hand, the incorporation of a custom-designed polymer additive improved the pulp brightness without any solvent treatment. The same additive played a negative role in the presence of a swelling solvent. The function of the polymer additive in the flotation de-inking process is also described. 相似文献
954.
Yasumichi Matsumoto Noriyuki Tanaka Hideki Kato 《Journal of solid state chemistry》2004,177(11):4205-4212
Photoelectrochemical measurements of TiO2, NaTaO3, and Cr or Sb doped TiO2 and SrTiO3 photocatalysts were carried out in H2 and O2 saturated electrolytes in order to evaluate the reverse reactions during water photolysis. The poor activity of TiO2 as a result of reverse photoreactions of O2 reduction and H2 oxidation was revealed with the respective high cathodic and anodic photocurrents. The rise in the photocurrents at NaTaO3 after La doping was in harmony with the doping-induced increase in the photocatalytic activity. NiO loading suppresses the O2 photoreverse reactions, which declines photocatalytic activity, and/or promotes the photo-oxidation of water, because the O2 photo-reduction current was scarcely observed near the flatband potential. Photocurrents of O2 reduction and H2 oxidation were observed under visible light for the Cr and Sb doped SrTiO3 and TiO2, respectively. These phenomena are in harmony with the previous reports on the photocatalysts examined with sacrificial reagents. 相似文献
955.
T. Kolarov R. Yankov N. E. Esipova D. Exerowa Z. M. Zorin 《Colloid and polymer science》1993,271(5):519-520
Experiments are reported with foam films from aqueous solutions with increasing concentration of a cationic surfactant. A correlation is established between the foam film thickness and the possible variation of diffuse electric layer potential at the air/water interface from a negative value in absence of surfactant to positive values at higher surfactant concentrations. It is concluded that a charge reversal at the air/water interface is expected to occur under increasing concentration of cationic surfactants in aqueous solutions. 相似文献
956.
957.
Christiane Bonnelle 《Mikrochimica acta》2002,138(3-4):275-282
The possibilities presented by low-energy electron-induced X-ray emission spectroscopy to study chemical interactions in
solids are discussed. Examples of change observed for the emissions between core levels as a function of the chemical environment
of the emitting atoms are given. By comparing the partial densities of the valence states associated to each type of atoms
in the compound, it is shown that the strength of the metal-ligand interactions can be obtained. Information on the charge
densities around each type of atoms can be deduced. Application to the study of the interactions at the atomic scale to solid–solid
interfaces is presented. 相似文献
958.
We propose a graphical method to treat dilution shift in NMR spectra to determine the monomer shift, dimer shift and dimerization constant simultaneously and consistently for the system of monomer/dimer equilibrium. The salient features include avoiding error-prone manual extrapolation to zero concentration to obtain a monomer shift, and providing consistent assessment and error estimation for the determination. The dilution shifts of 2-isopropyl phenol in C6D12 serve to demonstrate this graphical method. The enthalpy and entropy of dimerization are determined via a van't Hoff plot from the temperature variation of the dimerization constant. 相似文献
959.
We have simulated the two- and three-dimensional Ising models at their respective critical points with a conventional Monte Carlo algorithm. From the power spectrum of the magnetization autocorrelations we have determined the dynamic critical exponents and obtained the valuesz = 2.16–2.19 andz = 2.05, in agreement with the results quoted in the literature. We have also studied the power spectrum for the Kardar-Parisi-Zhang and Sun-Guo-Grant equations describing interface dynamics. Arguments similar to what was recently used to conclude thatz = 4 - for model B in critical dynamics were applied to the Sun-Guo-Grant growth model and the known exact values for the roughening and dynamic exponents were obtained. From an analysis of the corresponding power spectrum in self-organized critical sand models one obtains a recently proposed hyperscaling relation. 相似文献
960.
M. B. Urquiola E. D. Sudol V. L. Dimonie M. S. El-Aasser 《Journal of polymer science. Part A, Polymer chemistry》1993,31(6):1403-1415
A mathematical model was developed to aid in the further understanding of the growth of latex particles in the emulsion polymerization of vinyl acctate using a polymerizable surfactant, sodium dodecyl allyl sulfosuccinate (TREM LF-40). The model incorporates the main features of the system observed experimentally: copolymerization in the aqueous phase, at the particle surface, and chain transfer to TREM LF-40. The reactions at the particle/water interface and, more specifically, the chain transfer to TREM LF-40 leading to a decrease in the average number of radicals per particle, was found to be the most significant mechanism for explaining the difference in kinetic results found for TREM LF-40 and its nonpolymerizable counterpart. The copolymerization of vinyl acetate with TREM LF-40 was also shown to slow the overall polymerization rate. However, the copolymerization alone was not sufficient to account for the decreased polymerization rates observed experimentally. A combination of copolymerization and chain transfer to TREM LF-40 was found to provide a good fit of the experimental results. © 1993 John Wiley & Sons, Inc. 相似文献