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871.
Changes in density and surface tension of water in silica pores 总被引:3,自引:0,他引:3
T. Takei K. Mukasa M. Kofuji M. Fuji T. Watanabe M. Chikazawa T. Kanazawa 《Colloid and polymer science》2000,278(5):475-480
The density and surface tension of water in small pores of silicas have been investigated. These physical properties of water
in the pores were calculated from a comparison of pore volumes and pore radii which were estimated from adsorption and desorption
isotherms of nitrogen and water. Below a pore radius of about 5 nm both the density and the surface tension of water in the
pores were smaller than those of the bulk liquid and decreased with a decrease in pore size. The density of water in the pores
decreased with an increase in the concentration of surface hydroxyl groups. Similarly the surface tension of water in the
pores is influenced by the surface hydroxyl groups. Anomalous changes in the density and surface tension of the water in the
pores are attributed to the interaction of water molecules with surface hydroxyl groups and hydrogen-bond formation among
water molecules.
Received: 20 April 1999 Accepted in revised form: 17 November 1999 相似文献
872.
Douglas M. Ruthven 《Adsorption》2000,6(4):287-291
The transient uptake response of an adsorbent particle, subjected to a step change in surface concentration, is considered. It is shown that, when the isotherm is highly favorable, the theoretical curves derived for a Langmuirian system reduce asymptotically to the much simpler form for a rectangular isotherm. The simple rectangular model provides a useful approximation even when the form of the actual isotherm is quite far from the rectangular limit. 相似文献
873.
874.
875.
Moonis R. Ally 《Monatshefte für Chemie / Chemical Monthly》2000,131(4):341-344
Summary. The Stokes-Robinson modification of the Brunauer-Emmett-Teller (BET) adsorption isotherm is used to calculate the liquidus curve of NaNO3(aq) including the eutectic point and metastable phases. The method described here represents a simplified approach to predict
the liquidus curves with sparse information.
Received August 9, 1999. Accepted November 4, 1999 相似文献
876.
I. Felh
si R. kes P. Baradlai G. Plinks K. Varga E. Klmn 《Journal of Electroanalytical Chemistry》2000,480(1-2)
Coupled application of a version of the in-situ radiotracer ‘foil’ method and voltammetry provided information on the time-, potential-, concentration- and pH-dependent adsorption of 1-hydroxy-ethane-1,1-diphosphonic acid (HEDP) on a polycrystalline gold electrode, and on the effect of Zn2+ ions on the adsorption phenomena. Adsorption processes on the oxide-free surface of gold were observed to be potential-dependent in the potential range 0.05–1.00 V (versus RHE), while formation and irreversible accumulation of oxidation products of HEDP could be detected at E>1.00 V. The relative adsorption strength of HEDP (its dissociation and/or oxidation products) was found to be higher on an oxide-free gold surface than on an oxide-covered one. The surface excess of HEDP increased with increasing pH. Addition of Zn2+ ions to the solution exerted a substantial effect on the HEDP accumulation. Namely, significant differences in the surface coverage, as well as in the kinetics and mechanism of HEDP adsorption could be detected in the potential regions below and above E=0.2 V. Reduction of Zn(II) species at E≤0.1 V is probably coupled with the induced adsorption of HEDP on an Au electrode, leading to the formation of a polymolecular HEDP–Zn surface complex layer. 相似文献
877.
用insituFTIR法研究了H2、CO及CO/H2在ZrO2表面的吸附行为.结果表明,H2在ZrO2表面吸附存在两种形态的羟基(即ZrOH和ZrOHZr),吸附温度增加,羟基数量增加.CO在200℃易与ZrO2表面羟基作用形成甲酸盐物种,吸附温度升高时,该物种逐渐分解生成CO和ZrOH.当CO和H2共存时,表面甲酸盐的量明显增加,并随温度增加,逐渐加氢形成甲氧基,最后生成甲烷.甲氧基的加氢过程较慢,所需反应温度也较高,被认为是CO加氢合成醇的速控步骤. 相似文献
878.
研究了不同pH值介质中酪氨酸在活性炭上的吸附行为.结果表明,pH值4.2~6.1时吸附量较大,在酪氨酸的等电点时吸附量最大;酪氨酸被吸附的主要形式是兼性离子;酪氨酸离子靠VanderWaals力吸附在活性炭/水界面上.用介质pH值对酪氨酸溶解度的影响和活性炭的表面性质解释了实验结果 相似文献
879.
Compression behavior and structure of dense helium at high temperatures by molecular dynamics simulation 总被引:1,自引:0,他引:1
In this work,the isotherm and energy distribution at T=304 K of dense helium are studied by molecular dynamic (MD) simulations with exp-6 potential r*=2.9673 ? (the position of the well minimum) and ε/kB=10.8 K (ε is the well-depth and kB is the Boltzmann constant) given by Peter et al.,and different values of stiffness parameter α.The optimized value of α=12.7 is deduced that can describe the atomic interactions for dense helium satisfactorily.This optimized α in exp-6 potential is used to conduct MD simulations of two isotherms of dense helium at T=300 K and T=298K.The calculations are in good agreement with the experimental.We further employed this method to investigate the equation-of-state and structure of dense helium at higher temperatures and found that when the density remained 1.6 g/cm3,the second peak of the radial distribution function would disappear in the temperature range from 2000 to 3040 K,demonstrating that a solid-liquid transition or decrystallization had occurred. 相似文献
880.
Summary: The adsorbance of ranitidine hydrochloride – drug selective H2 histamine receptor inhibitor used In the treatment of gastric and duodenal ulcer was investigated in the presence of croscarmellose, a cross- linked polymer of polysaccharide character used as a swelling additive in oral pharmaceutical formulations – capsules, tablets and granules. The evaluation of adsorbance capability was carried out by means of a statistical method in in vitro conditions, taking into account environmental pH, concentration of the investigated drug as well as the properties of the polymer. Obtained results prove that the analyzed active agent is adsorbed on polymer at all the investigated pH ranges and the capability of polymer binding depends on environmental pH. The highest binding capability was revealed in samples with pH of 7.6, (adsorbance capacity k = 0.6958) while the lowest binding capability was observed at pH 1.5 (adsorbance capacity k = 0.0005) in the presence of croscarmellose sodium. Level of adsorption depends on the analyzed drug concentration and adsorption on polymer in increasing concentration and pH environment. 相似文献