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91.
Fuat Güzel Önder Aksoy Gülbahar Akkaya 《Journal of Dispersion Science and Technology》2014,35(4):482-493
Pomegranate pulp has been used as novel adsorbent for removing Cu(II) ions from aqueous solution. The optimum conditions for removal of Cu(II) ions were found to be pH 5.32, biosorbent dose 0.1 g, contact time 120 minutes, initial concentration 50 mg/L, and temperature 30°C. The kinetic data were well fitted to the pseudo-second-order model. The biosorption process agreed with the Langmuir isotherm model. Maximum monolayer biosorption capacity was 7.30 mg/g. Thermodynamic parameters suggest that the biosorption process is spontaneous and exothermic. Desorption studies were carried out with different desorbing agents. 相似文献
92.
Syed Mustafa Muhammad Waseem Abdul Naeem Khizar Hussain Shah Tauqeer Ahmad Muhammad Safdar 《中国化学》2010,28(11):2204-2208
The current study focuses on the synthesis and sorption properties of two mixed oxides of iron and silicon prepared by physical mixing (M1) and sequential precipitation methods (M2). Both the mixed oxides were synthesized from equimolar ratios of Fe(OH)3 and SiO2 and characterized for surface area, EDX, XRD and PZC. The surface area, micropore volume and average pore width of the oxide M1 were higher as compared to the oxide M2. However, potentiometric titrations revealed that mixed oxide synthesized by this method had a very high capacity towards Cd2+ ions as compared to the mixed oxide M1. Sorption of Cd2+ ions at pH 5 on mixed oxide, M2 was found to increase with temperature in the range 288 to 318 K. Langmuir equation was found applicable to the sorption data with R2>0.99. Entropy (ΔS?), enthalpy (ΔH?) and free energy changes (ΔG?) were calculated which revealed the process to be endothermic and spontaneous in nature. 相似文献
93.
Yanping Cao Jingtao Chen Prof. Dr. Youying Di Donghua He Wenyan Dan Yupu Liu 《中国化学》2010,28(11):2308-2314
The tetrachlorocuprate(II) ethylenediammonium and tetrachlorocadmate(II) ethylenediammonium were synthesized. Chemical analysis, elemental analysis, and X‐ray crystallography were applied to characterize the compositions and crystal structures of the two complexes. The lattice potential energies and the radiuses of the anions of two complexes were calculated to be UPOT[(C2H10N2)CuCl4]=1810.19 kJ·mol?1, UPOT[(C2H10N2)CdCl4]=1784.39 kJ·mol?1, r[(CuCl4)2?]=0.308 nm, and r[(CdCl4)2?]=0.321 nm from the data of the crystal structure, respectively. Low‐temperature heat capacities of the two complexes were measured by a precision automatic adiabatic calorimeter with the small sample over the temperature range from 78 to 400 K, respectively. Two polynomial equations of heat capacities against the temperatures were fitted by least square method: Cp,m[(C2H10N2)CuCl4, s] =213.553+118.578X?5.816X2+4.392X3+0.276X4 and Cp,m[(C2H10N2)CdCl4, s] =190.927+98.501X?7.931X2+0.657X3+3.834X4, in which X= (T?239)/161. Based on the fitted polynomial equations, the smoothed heat capacities and thermodynamic functions of the two complexes relative to the standard reference temperature 298.15 K were calculated at intervals of 5 K. 相似文献
94.
The inclusion complexes formation of dipfluzine(DF)with hydroxpropy -β-cyclodextrin(HP-β-CD)in aqueous solution was investigated by the phase-solubility method.With the increase of HP-β-CD concentration in aqueous sloutions,the solubility of DF increased linearly,which showed typical AL-type phase solubility diagram.The molar ratio of the DF-HP-β-CD complex was 1: 1.The effect of temperature on the reaction was studied through thermodynamics.The apparent stability constants of inclusion reation were determined.Thermodynamic parameters during the inclusion process were as follows: △_rH=30.58 kJ·mol~(-1),△_rS=158.8 J·mol~(-1)·K~(-1),△_rG<0.The complex process was endothermic and spontaneous.With the increase of temperature,the tendency of spontaneous reaction increased. 相似文献
95.
随着核能事业的发展,高放废物的处理和处置问题日益突出.其中,研究高放废物在环境介质中的吸附、扩散和迁移行为是获取放射性核素对周围环境和人群健康影响的基础参数的最重要和最直接的途径.近年来,人们利用已有的实验数据及核素的基础热力学和动力学数据,附以相应的数学模型,建立了一些地球化学模拟软件,用于分析核素在地质介质中可能发生的连续性和长期性变化.目前,国内外常用的地球化学模拟软件有十多种.本文从热力学平衡计算原理、种态分布计算方法和表面配位模型假设等几个方面对地球化学模拟软件进行了简要介绍,对近年来地球化学模拟软件在核素种态分布计算和表面配位模型模拟两方面的应用进行了举例分析,并以Ca-U-CO3配合物为例,说明完备的热力学数据对地球化学模拟软件发展的重要性,以期促进我国地球化学模型的应用和发展. 相似文献
96.
《Physics and Chemistry of Liquids》2012,50(5):578-586
ABSTRACTThe solubilities of bosentan (BST) in binary aqueous mixtures of 2-propanol at temperatures ranging from 293.15 to 313.15 K were determined using a shake-flask method. The produced data were modelled with the Jouyban-Acree-van’t Hoff model and difference between the predicted data and experimental ones were illustrated by percent average relative deviations (%ARD). Moreover, the thermodynamic functions of dissolution for BST in the aqueous 2-propanol solutions were computed which suggest that the dissolution process is endothermic and not spontaneous. 相似文献
97.
Herbert Hommer Gabriel Cuevas Barbara Gordillo 《Phosphorus, sulfur, and silicon and the related elements》2013,188(10):2421-2437
By following a previously reported method,1 the synthesis of r-2-alkoxy-cis-4-cis-5-dimethyl-1,3,2-λ3-dioxaphospholanes ligands (1 and 3) was carried out. The purpose of this work is the kinetic study of the inversion barrier at phosphorus for 1 and 3 and the comparison with the already informed dioxaphospholane 2. The kinetic measurements of the thermal isomerization cis-to-trans were performed by 31P NMR spectroscopy, observing a first order kinetics for both compounds. The energy of activation (Ea) for the epimerization of compounds cis-1 and cis-3 was calculated to be 16.0 ± 0.6 and 11.8 ± 0.8 kcal/mol, respectively. The values of the thermodynamic parameters of the transition state (Δ H≠, Δ S≠, Δ G≠) suggest that the inversion at phosphorus not only depends on the spatial requirements of the alkoxy substituent but also on entropic effects. The thermodynamic parameters Δ H°, Δ S°, and Δ G° were also evaluated and they show that the cis isomers are preferred from enthalpic point of view, but entropic effects dominate the equilibrium trans ? cis leading to the entropically favored trans isomers. Furthermore, the results are supported by density functional theory calculations of 1–4 at the B3LYP/6-31G** level. 相似文献
98.
Ping Yin Yucai Hu Chunhua Wang Yuan Tian Qinghua Tang Chongrong Bao 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):514-522
Theoretical studies on the thermodynamic and kinetic properties of the reactions of Ti+ with sulfur transfer reagent SCO via the C═S bond activation pathway have been carried on using DFT/B3LYP method, general statistical thermodynamics, and Eyring transition state theory with Wigner correction. The relevant reactions include reaction 1 4 Ti++1SCO → 4 IM 1 → 4 TS 1 → 4 IM 2 → 4 TiS++ 1 CO, and reaction 2 4Ti++1SCO →4IM1→ CP →2IM2→2TiS++1CO in which the spin multiplicity changes from the quartet state to the doublet state in the crossing region. It is concluded that the increase of the temperature is favored to the reaction 1 process, since the equilibrium constants (K) rises from 0.566 × 10[P]-9 at 200 K to 0.109 × 100 at 1200 K, and the reaction rate constant (k) from 0.222 × 100 s[P]-1 at 200 K to 0.540 × 10 11 s[P]-1 at 1200 K. Moreover, reaction 1 is endothermic, and non-spontaneous in the way the entropy increases, while reaction 2 is exothermic and spontaneous in the way their entropy decreases. The reaction path 2 is the energetically favorable channel, and its thermodynamic data change not largely with the rise of temperature. 相似文献
99.
A. Bialski R. J. St. Manley M. R. Wertheimer H. P. Schreiber 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(3):609-618
A Large-volume Microwave Plasma (LMP) generator has been used to irradiate mica and ground-wood fibers in inert and active gas environments. Irradiated fillers were subsequently incorporated in a polypropylene matrix at solids levels of 10 and 20%. Calorimetrically measured heats of immersion showed that substantial changes in surface properties of fillers were effected by irradiation in ethylene, ammonia, and similar active gases. These surface changes are reflected In ultimate tensile and elongation properties of composites which show marked improvement over controls based on unirradiated fillers. Although no appreciable response in melt viscosity has been observed, surface treatment of fillers does seem to increase significantly melt elasticity of filled composites. The implications of improved performance motivate a more detailed study of the use potential of LMP in the fomulation of polymer composites. 相似文献
100.
Sergio F. Sousa 《Journal of computational chemistry》2013,34(15):1354-1362
The determination of differences in solvation free energies between related drug molecules remains an important challenge in computational drug optimization, when fast and accurate calculation of differences in binding free energy are required. In this study, we have evaluated the performance of five commonly used polarized continuum model (PCM) methodologies in the determination of solvation free energies for 53 typical alcohol and alkane small molecules. In addition, the performance of these PCM methods, of a thermodynamic integration (TI) protocol and of the Poisson–Boltzmann (PB) and generalized Born (GB) methods, were tested in the determination of solvation free energies changes for 28 common alkane‐alcohol transformations, by the substitution of an hydrogen atom for a hydroxyl substituent. The results show that the solvation model D (SMD) performs better among the PCM‐based approaches in estimating solvation free energies for alcohol molecules, and solvation free energy changes for alkane‐alcohol transformations, with an average error below 1 kcal/mol for both quantities. However, for the determination of solvation free energy changes on alkane‐alcohol transformation, PB and TI yielded better results. TI was particularly accurate in the treatment of hydroxyl groups additions to aromatic rings (0.53 kcal/mol), a common transformation when optimizing drug‐binding in computer‐aided drug design. © 2013 Wiley Periodicals, Inc. 相似文献