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151.
J. Grant Hill 《International journal of quantum chemistry》2013,113(1):21-34
The choice of basis set in quantum chemical calculations can have a huge impact on the quality of the results, especially for correlated ab initio methods. This article provides an overview of the development of Gaussian basis sets for molecular calculations, with a focus on four popular families of modern atom‐centered, energy‐optimized bases: atomic natural orbital, correlation consistent, polarization consistent, and def2. The terminology used for describing basis sets is briefly covered, along with an overview of the auxiliary basis sets used in a number of integral approximation techniques and an outlook on possible future directions of basis set design. © 2012 Wiley Periodicals, Inc. 相似文献
152.
Alexander V. Mitin 《Journal of computational chemistry》2013,34(23):2014-2019
The 2df polarization functions for the modified m6‐31G basis sets of the third‐row atoms Ga through Kr (Int J Quantum Chem, 2007, 107, 3028; Int J. Quantum Chem, 2009, 109, 1158) are proposed. The performances of the m6‐31G, m6‐31G(d,p), and m6‐31G(2df,p) basis sets were examined in molecular calculations carried out by the density functional theory (DFT) method with B3LYP hybrid functional, Møller‐Plesset perturbation theory of the second order (MP2), quadratic configuration interaction method with single and double substitutions and were compared with those for the known 6‐31G basis sets as well as with the other similar 641 and 6‐311G basis sets with and without polarization functions. Obtained results have shown that the performances of the m6‐31G, m6‐31G(d,p), and m6‐31G(2df,p) basis sets are better in comparison with the performances of the known 6‐31G, 6‐31G(d,p) and 6‐31G(2df,p) basis sets. These improvements are mainly reached due to better approximations of different electrons belonging to the different atomic shells in the modified basis sets. Applicability of the modified basis sets in thermochemical calculations is also discussed. © 2013 Wiley Periodicals, Inc. 相似文献
153.
Xiaogang Yang Bin Li Haizeng Wang Baorong Hou 《Journal of Dispersion Science and Technology》2013,34(5):672-676
The inhibition effect of cetyl trimethyl ammonium bromide (CTAB) on the corrosion of mild steel in 1.0 mol L?1 hydrochloric acid (HCl) has been studied at different temperatures (25–60°C) by weight loss and potentiodynamic polarization methods. The results reveal that CTAB behaves as an effective inhibitor in 1.0 mol L?1 HCl, and the inhibition efficiency increases with the inhibitor concentration. Polarization curves show that CTAB is a mixed-type inhibitor in hydrochloric acid. The results obtained from weight loss and polarizations are in good agreement. The effect of immersion time on corrosion inhibition has also been examined and is discussed. The adsorption of inhibitor on mild steel surface obeys the Langmuir adsorption isotherm equation. Thermodynamic parameters have been obtained by adsorption theory. The inhibition effect is satisfactorily explained by the parameters. 相似文献
154.
Muhammad A. Khosa Syed Sakhawaat Shah 《Journal of Dispersion Science and Technology》2013,34(7):1002-1007
Reactive black 5 (RB-5) dye was removed from a water stream using two cationic surfactants, cetyltrimethylammonium bromide (CTAB) and cetylpyridinium chloride (CPC), via micellar enhanced ultrafiltration. Three membranes with different pore size were used for the determination of rejection coefficient and permeate flux of the solution at 1.5 bar trans-membrane pressure (TMP). The two surfactants (CPC and CTAB) played an almost negligible role in rejection efficiency with 5000 and 10,000 molecular weight cut-off membrane (MWCO), respectively. In this case, high rejection and low permeate flux was the result of a larger molecular size of RB-5 DYE being retained by comparatively smaller sized pores of membrane via ultrafiltration. However, CPC and CTAB surfactants showed 83% and 98% rejection coefficient, respectively, at a concentration greater than their CMC values against 30,000 MWCO. Permeate flux remained low and constant in presence of 5000 and 10,000 MWCO with a small variation against 30,000 MWCO for the two surfactants, thereby no appreciable effect on both surfactant concentrations on concentration polarization was estimated. Thus, RB-5 dye alone was determined to be responsible for membrane plugging or concentration polarization and ultimately for low permeate flux. The effect of trans-membrane pressure was also investigated during this study. 相似文献
155.
Formation of supermolecular structures in petroleum disperse systems is determined by interactions of asphaltenes. Petroleum systems are lyophilic oleocolloids with low polar dispersive media which is in dynamic balance with elements of disperse structure. Supermolecular scale of organization is most important for determining the macroscopic parameters. Levshin-Perrin equation for depolarization of fluorescence was modified for polydispersed systems. Interfacial tension coefficient of model asphaltene solution was calculated in a case of Volmer's function. For technogenic mixtures the temperature dependences of the sizes near the point of phase transition are presented. Enthalpy of asphaltene association per one molecule was calculated. Polarization degree together with macroscopic parameters correlates with appearance of asphaltene dispersed phase in system. 相似文献
156.
Hyeonbae Kang Hyundae Lee Mikyoung Lim 《Mathematical Methods in the Applied Sciences》2015,38(9):1847-1854
We present a new systematic method to compute the Riemann mapping from the outside of the unit disc to the outside of a simply connected domain. We derive explicit relations between the coefficients of the Riemann mapping and the generalized polarization tensors associated with the domain. Because the generalized polarization tensors can be computed numerically, we are able to compute the coefficients of the Riemann mapping using these relations. Effectiveness of the method is validated by numerical examples. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
157.
As a kind of ammonia‐oxidizing bacteria, Nitrosomonas europaea (N. europaea) was chosen as a research model to study the alteration of cell membrane in the presence of tourmaline and biodegradation of acetochlor. atomic force microscopy images reveal that the presence of tourmaline substantially changes the structure of the outer membrane of the cell responsible for the cell permeability. SEM images show that the introduction of tourmaline makes the cell lose its ability to resist lysozyme owing to the damages. The fluorescence polarization has shown a significant decrease in membrane fluidity and the increase of permeability of cell membrane. Ca2+ and Mg2+ was measured using inductively coupled plasma mass spectrometry and was found in the supernatant from the cells treated by tourmaline. Tourmaline can improve the efficiency of biodegradation of acetochlor for N. europaea. It is proposed that the cell permeability is slightly increased, and the absorbability of nutrition from the medium becomes easier. As a result, N. europaea grows faster in the presence of tourmaline than the native cells. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
158.
The passive film of iron showed n‐type semiconductor characteristic in borate buffer solution, and its donor concentration increased slightly after tensile strain in the present study. However, comparing with solution‐annealed sample, the anodic passive film formed on tensile‐strained one was highly protective. The more dislocations on tensile‐strained sample promoted the diffusion of iron and oxygen vacancy. Moreover, more donor density (mainly oxygen vacancies) promoted the diffusion of oxygen. They all facilitated tensile‐strained sample to form Fe2O3 and thicker passive film on the surface. More Fe2O3 and thicker passive film on the surface of tensile‐strained iron could improve corrosion resistance. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
159.
A polarizable empirical force field for molecular dynamics simulation of liquid hydrocarbons
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Oliwia M. Szklarczyk Stephan J. Bachmann Wilfred F. van Gunsteren 《Journal of computational chemistry》2014,35(10):789-801
Electronic polarizability is usually treated implicitly in molecular simulations, which may lead to imprecise or even erroneous molecular behavior in spatially electronically inhomogeneous regions of systems such as proteins, membranes, interfaces between compounds, or mixtures of solvents. The majority of available molecular force fields and molecular dynamics simulation software packages does not account explicitly for electronic polarization. Even the simplest charge‐on‐spring (COS) models have only been developed for few types of molecules. In this work, we report a polarizable COS model for cyclohexane, as this molecule is a widely used solvent, and for linear alkanes, which are also used as solvents, and are the precursors of lipids, amino acid side chains, carbohydrates, or nucleic acid backbones. The model is an extension of a nonpolarizable united‐atom model for alkanes that had been calibrated against experimental values of the density, the heat of vaporization and the Gibbs free energy of hydration for each alkane. The latter quantity was used to calibrate the parameters governing the interaction of the polarizable alkanes with water. Subsequently, the model was tested for other structural, thermodynamic, dielectric, and dynamic properties such as trans/gauche ratios, excess free energy, static dielectric permittivity, and self‐diffusion. A good agreement with the experimental data for a large set of properties for each considered system was obtained, resulting in a transferable set of polarizable force‐field parameters for CH2, CH3, and CH4 moieties. © 2014 Wiley Periodicals, Inc. 相似文献
160.
The adsorption and corrosion inhibition behavior of synthesized Schiff base-based cationic gemini surfactant bis[p-(N,N,N-tetradecyldimethylammonium bromide)benzylidene]thiourea (14-S-14) on mild steel in 20% formic acid in the temperature range of 30°C to 60°C was evaluated using weight loss measurements, solvent analysis of iron ions and potentiodynamic polarization measurements. The synthesized inhibitor was characterized using Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), and thin layer chromatography (TLC). The surface morphology of the corroded mild steel specimen was evaluated using scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDAX), and atomic force microscopy (AFM). Thermodynamic/kinetic parameters were calculated to elaborate the adsorption and corrosion inhibition mechanism of the inhibitor. The inhibition efficiency of the compound was found to vary with inhibitor concentration, immersion time, and temperature. The adsorption of the compound on the steel surface was found to obey Langmuir adsorption isotherm. 相似文献