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111.
Preferential sorptions and pervaporation selectivities in poly (vinyl chloride) (PVC) membrane for various binary liquid mixtures were investigated. Methanol/n-propanol, benzene/n-hexane, and ethanol/water mixtures were selected as the binary liquid mixture. In the methanol/n-propanol mixture, methanol was preferentially sorbed in the PVC membrane and predominantly permeated. In the benzene/n-hexane mixture, benzene was incorporated and permeated preferentially. In the ethanol/water mixture, ethanol was preferentially sorbed in the PVC membrane and water was preferentially permeated. The preferential sorptions were analyzed according to Mulder's model derived from Flory-Huggins thermodynamics. The pervaporation selectivity in these systems were discussed using a sorption selectivity and diffusion selectivity. © 1995 John Wiley & Sons, Inc. 相似文献
112.
N. Dolmaire F. Mchin E. Espuche J. P. Pascault 《Journal of Polymer Science.Polymer Physics》2006,44(1):48-61
A hydrophilic thermoplastic polyurethane (TPU) was modified by reactive extrusion to obtain in a first step a grafted and soluble material and to finally form by a hydrolysis condensation process a weakly crosslinked network. Different isocyanates were used as grafting agents and a α,ω‐dihydroxypoly(dimethylsiloxane) (PDMS) was used to modify the hydrophilic/hydrophobic balance of the material and the chain length between the crosslinks. The influence of the isocyanate functionality and of the PDMS content were studied on the network formation and on the thermomechanical and water sorption properties. The networks properties were also compared with those of a TPU/PDMS blend. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 48–61, 2006 相似文献
113.
Non‐Fickian sorption kinetics of methanol vapor in a poly(methyl methacrylate) film of 8 μm, at 35 °C, are presented. The behavior of the system was studied in series of interval absorption runs. The relevant diffusion and viscous relaxation processes were studied by kinetic analysis of the sorption kinetic curves, using the relaxation‐dependent solubility model. The sorption isotherm concaves upward at high activities, typical to Florry–Huggins behavior, while it exhibits a convex‐upward curvature at low methanol vapor activities, indicating sorption in the excess free volume of the polymer matrix. Thermodynamic diffusivity presents a complex functional dependence on the concentration, while relaxation rate is found to be a function of concentration as well as of concentration interval. Relaxation rate becomes increasingly concentration‐dependent as the effective glass transition of the system is approached. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3173–3184, 2006 相似文献
114.
One vision of clean energy for the future is to produce hydrogen from coal in an ultra-clean plant. The conventional route
consists of reacting the coal gasification product (after removal of trace impurities) with steam in a water gas shift (WGS)
reactor to convert CO to CO2 and H2, followed by purification of the effluent gas in a pressure swing adsorption (PSA) unit to produce a high purity hydrogen
product. PSA processes can also be designed to produce a CO2 by-product at ambient pressure. This work proposes a novel concept called “Thermal Swing Sorption Enhanced Reaction (TSSER)”
which simultaneously carries out the WGS reaction and the removal of CO2 from the reaction zone by using a CO2 chemisorbent in a single unit operation. The concept directly produces a fuel-cell grade H2 and compressed CO2 as a by-product gas. Removal of CO2 from the reaction zone circumvents the equilibrium limitations of the reversible WGS reaction and enhances its forward rate
of reaction. Recently measured sorption-desorption characteristics of two novel, reversible CO2 chemisorbents (K2CO3 promoted hydrotalcite and Na2O promoted alumina) are reviewed and the simulated performance of the proposed TSSER concept using the promoted hydrotalcite
as the chemisorbent is reported. 相似文献
115.
Giuseppe Mensitieri Domenico Larobina Gaetano Guerra Vincenzo Venditto Maurizio Fermeglia Sabrina Pricl 《Journal of Polymer Science.Polymer Physics》2008,46(1):8-15
The transport of chloroform in films of atactic polystyrene and of semicrystalline syndiotactic polystyrene in its nanoporous form (δ‐form) has been investigated by gravimetric analysis. Experimental tests have been performed at 35, 49, and 56 °C and at several vapor pressures ranging from 0.5 to 100 Torr. Nonequilibrium lattice fluid prediction of the amorphous sorption behavior was used to enucleate the sorption contribution of the crystalline nanoporous phase from semicrystalline samples. Sorption behavior of the crystalline phase has been interpreted on the basis of Langmuir equation. Moreover, the chloroform sorption at low activities in the crystalline nanoporous phase has been predicted by using Grand Canonical Monte Carlo molecular simulations. Isosteric heats of sorption were also experimentally evaluated for the crystalline phase, and compared with the corresponding prediction of molecular simulation. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 8–15, 2008 相似文献
116.
Anna Sopková Michal Šingliar Ján Skoršepa Juraj Matanin Eva Terpáková 《Journal of inclusion phenomena and macrocyclic chemistry》1985,3(3):297-313
The structure and reactivity of one unique molecule may be understood only in relation to its molecular surroundings. The non-stoichiometric forms of the tetracyano complexes M(B)
mM (CN)4·nG (B=nitrogen or oxygen containing base; G=aromatic compound or H2O,m0,n>0) are understood in this respect. Their stoichiometric or non-stoichiometric forms, with voids either completely or more often partially occupied, are responsible for their observed sorptive and resorptive abilities. The effects of the surroundings are correlated with the results of thermal analysis, magnetic measurements and their sorptive abilities.Dedicated to Professor H. M. Powell. 相似文献
117.
B. S. Lim A. S. Nowick Kang-Wook Lee Alfred Viehbeck 《Journal of Polymer Science.Polymer Physics》1993,31(5):545-555
The effect of structure on the sorption kinetics of water and of various organic solutes into polyimide (PMDA-ODA) thin films was studied. The major techniques employed include measurements of sorption kinetics, density, and dielectric relaxation. More solute uptake, lower densities and higher diffusivities were observed for films cured at lower temperatures. By measuring both changes of mass and of density, the volume expansion of the polymer due to each solute was obtained; this was found to be proportional to the molar volume of the solute. The two dielectric relaxation peaks (denoted by γ1 and γ2) due to water (and other solutes) were studied in detail to obtain the relevant activation energies and the separate dipole moments. While water and methylene chloride appear in both γ1 and γ2 configurations, methyl and ethyl alcohol appear mainly as γ2, while acetic acid is primarily γ1. It was concluded that the γ1 configurations are relatively homogeneously distributed throughout the polymer, involving loose bonding to the polymer structure, while the γ2 configurations involve small clusters, probably chains of molecules. © 1993 John Wiley & Sons, Inc. 相似文献
118.
Summary Pronounced base line perturbations were repeatably observed in LC both in alternating recycling and in backflushing experiments when binary eluents and refractometric detectors were used. The perturbations which we call eigenzones appeared immediately after operating the recycling or the backflushing valve, and their size and shape depended on the nature of both the column filling and the mixed mobile phase as well as on the pressure drop across the column.Experimental results presented confirm that the primary causes of the eigenzones were the pressure changes in the columns which influenced the sorption equilibrium of mixed eluent components within the column packing. Some practical consequences of this effect are briefly discussed.Second part of the series discussing the role of pressure in LC. First part: see ref. [1]. 相似文献
119.
K. G. Papadokostaki J. H. Petropoulos 《Journal of Polymer Science.Polymer Physics》1994,32(14):2347-2356
A detailed investigation of the sorption of 4-aminoazobenzene by cellulose acetate films from aqueous solution is reported. Sorption isotherms at 75 and 60°C were linear up to saturation, in agreement with previous findings that have led to the conclusion that cellulose acetate-disperse dye systems are thermodynamically ideal. Thermodynamic analysis of these data also gave results consistent with such previous findings. The isotherms for 45 and 25°C, on the other hand, exhibited increasing curvature, in line with similar recent findings for a variety of hydrophobic polymer-disperse dye systems, and consistent with the presence of some strong absorption sites. However, the situation appears to be more complex than envisaged by simple dual-mode sorption theory. Early time desorption kinetic data were found to be consistent with Fick's law, with no indication of any significant dependence of the diffusion coefficient D on concentration (in the medium- to high-concentration range) or on film thickness. On the other hand, D was affected significantly by the history of film formation, the method of introducing the dye or heat treatment of the film. The origin of these effects was traced by DSC to definite microstructural differences. Late time kinetic data deviated significantly from the theoretical predictions based on the corresponding early time data, indicating a progressive slowdown of the desorption process. The deviations in question were generally more marked at higher temperature or film thickness, or when dyeing had been effected from the vapor phase, and were attributed to slow release of strongly adsorbed dye molecules. © 1994 John Wiley & Sons, Inc. 相似文献
120.