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991.
The paper focuses on the microstructural characterisation of secondary phases in an AZ91 magnesium alloy. The orientation
relationship and atomic structure of semi-coherent Mg/Mg17Al12 interfaces are studied by means of selected area diffraction, EDS and high resolution TEM. Besides the common Mg17Al12 semi-coherent platelets of high density and coarser incoherent Mg17Al12 particles, other, less frequent precipitates were found, rich in Al and Mn. The quasicrystalline nature of these precipitates
was detected by means of electron diffraction. 相似文献
992.
Ludvík Beneš Vítězslav Zima Jan Svoboda Klára Melánová 《Journal of inclusion phenomena and macrocyclic chemistry》2005,53(1-2):41-46
The intercalates of 9,10-anthraquinone-2,6-disulfonate, 9,10-anthraquinone-2-sulfonate, and 2-naphthol-3,6-disulfonate anions
were prepared by heating [Zn0.67Al0.33(OH)2](CO3)0.165 · 0.5H2O with a solution of corresponding acid in an open reaction vessel. The intercalates were characterized by chemical and thermal
analysis, X-ray powder diffraction and UV-vis spectroscopy. Thermal behavior of the intercalates prepared was followed by
in situ X-ray diffraction. Dehydration was reversible for all three intercalates. If the samples dehydrated at 400 °C reacted with
water, brucite-like layers of the host were reconstructed.
Received in final form: 14 January 2005 相似文献
993.
Metod Saniga Péter Lévay Michel Planat Petr Pracna 《Letters in Mathematical Physics》2010,91(1):93-104
Having in mind their potential quantum physical applications, we classify all geometric hyperplanes of the near hexagon that is a direct product of a line of size three and the generalized quadrangle of order two. There are eight different kinds of them, totalling to 1,023 = 210 − 1 = |PG(9, 2)|, and they form two distinct families intricately related with the points and lines of the Veldkamp space of the quadrangle in question. 相似文献
994.
Vojtěch Hrouda Martin Polášek Petr Čársky Josef Michl 《Theoretical chemistry accounts》1994,89(5-6):401-413
Summary An analytical formula has been derived for averaging the differential cross section for electron scattering with respect to isotropic target molecule orientation. It may be applied to any type ofT-matrix element k
out|T|k
in in which the plane-wave functionsk
out andk
in are expanded in a set ofs-type Gaussian functions. The formula for averaging was tested against results obtained by Monte-Carlo-type calculations and against experimental data for elastic electron scattering by the H2 molecule. 相似文献
995.
Volodymyr Pauk Vladimír Havlíček Barbora Papoušková Petr Sulovský Karel Lemr 《Journal of mass spectrometry : JMS》2013,48(8):927-930
A new analytical protocol for identification of Prussian blue (PB) and indigo was proposed. Pigments useful for dating of artworks were detected by flow injection analysis/electrospray ionization mass spectrometry after alkalization of their suspensions in water, decomposition of PB to iron (III) hydroxide and hexacyanoferrate (II) and reduction of indigo to soluble leucoindigo using sodium dithionite. Limits of detection (PB 47 pg, indigo 59 pg) complied with requirements for analysis of microsamples of historical paintings. Potential of the developed method was proven in analysis of blue samples of two oil paintings from the 20th century. Further, PB was confirmed in a microsample from a painting of ‘Crucifixion’, St. Sebestian church on St. Hill in Mikulov, Czech Republic. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
996.
Mária Chromčíková Marek Liška Magdaléna Lissová Petr Mošner Ladislav Koudelka 《Journal of Thermal Analysis and Calorimetry》2013,114(3):947-954
The structural relaxation of three compositional series of PbO–WO3–P2O5 glasses with composition (0.5 ? x/2)PbO·xWO3·(0.5 ? x/2)P2O5, x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5; 0.5PbO·xWO3·(0.5 ? x)P2O5, x = 0, 0.1, 0.2, and 0.3; and (0.5 ? x)PbO·xWO3·0.5P2O5, x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5 was studied by thermomechanical analysis. The structural relaxation was studied in the transformation region using the Tool–Narayanaswamy–Moynihan’s and Tool–Narayanaswamy–Mazurin’s models. The relaxation function of Kohlrausch Williams and Watts was used. The parameters of both models were calculated by nonlinear regression analysis of thermodilatometric curves measured by thermomechanical analyzer under the constant load. Both models very well describe the experimental data. It was found that the modulus is increasing with increasing amount of WO3 in all glasses. On the contrary, the width of the spectrum of relaxation times is decreasing with increasing amount of WO3 in all studied glasses. Both models possess the values of metastable melt thermal expansion coefficient equal to their experimental value. 相似文献
997.
Petr Toman Emanuel Makrlík Petr Vaňura 《Monatshefte für Chemie / Chemical Monthly》2011,286(1):779-782
Abstract
From extraction experiments in the two-phase water/nitrobenzene system and γ-activity measurements, the stability constant of the beauvericin·Na+ complex species dissolved in nitrobenzene saturated with water was determined. By using quantum mechanical density functional level of theory (DFT) calculations, the most probable structure of this complex species was derived. 相似文献998.
Multidrug resistance (MDR) is often associated with overexpression of the P-glycoprotein (P-gp, ABCB1). It was demonstrated that the P-gp mediated efflux decreases the drug concentration in cancer cells which results in the failure of chemotherapy. However, the MDR phenotype in cancer cells obviously involves various mechanisms. Therefore, if we want to estimate a contribution of the P-gp expression to the MDR phenotype, a clear quantitative relationship between the intracellular drug level and cell sensitivity must be established. To achieve this goal, a sensitive and non-radioactive assay for precise determination of intracellular levels of imatinib and its main metabolite N-desmethyl imatinib (CGP 74588) has been developed. The assay is based on an optimised extraction of cells with 4% formic acid after their separation from the growth medium by centrifugation through a layer of silicone oil. Cell extracts are subsequently analyzed by LC/MS/MS. Calibration curves were linear from 1 to 500 nmol/l for imatinib and from 2 to 500 nmol/l for CGP 74588, with correlation coefficients (r2) better than 0.998 and 0.996, respectively. The limit of quantitation (LOQ) was 1 nmol/l for imatinib and 2 nmol/l for CGP 74588. Our method has been successfully applied to the determination of intracellular levels of imatinib in sensitive K562 and their resistant variant, K562/Dox cells. 相似文献
999.
Granatier J Lazar P Otyepka M Hobza P 《Journal of chemical theory and computation》2011,7(11):3743-3755
The adsorption of Ag, Au, and Pd atoms on benzene, coronene, and graphene has been studied using post Hartree-Fock wave function theory (CCSD(T), MP2) and density functional theory (M06-2X, DFT-D3, PBE, vdW-DF) methods. The CCSD(T) benchmark binding energies for benzene-M (M = Pd, Au, Ag) complexes are 19.7, 4.2, and 2.3 kcal/mol, respectively. We found that the nature of binding of the three metals is different: While silver binds predominantly through dispersion interactions, the binding of palladium has a covalent character, and the binding of gold involves a subtle combination of charge transfer and dispersion interactions as well as relativistic effects. We demonstrate that the CCSD(T) benchmark binding energies for benzene-M complexes can be reproduced in plane-wave density functional theory calculations by including a fraction of the exact exchange and a nonempirical van der Waals correction (EE+vdW). Applying the EE+vdW method, we obtained binding energies for the graphene-M (M = Pd, Au, Ag) complexes of 17.4, 5.6, and 4.3 kcal/mol, respectively. The trends in binding energies found for the benzene-M complexes correspond to those in coronene and graphene complexes. DFT methods that use empirical corrections to account for the effects of vdW interactions significantly overestimate binding energies in some of the studied systems. 相似文献
1000.
Interaction of octyl-phenyl-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO, the 'classical' rare metal extraction agent) with fully ionized hydrated protons (HP) was studied in acetonitrile-d(3) using (1)H, (13)C, (31)P NMR, PFG NMR and magnetic relaxation. The experimental results were confronted with high-precision ab initio DFT calculations. Relative chemical shifts of NMR signals of CMPO (0.01 mol/L) under the presence of HP in the molar ratio β = 0-2.0 mol/mol show binding between CMPO and HP. Self-diffusion measurements using (1)H PFG NMR demonstrate that larger complexes with higher content of CMPO are generally formed at β < 0.75. Analyzing the collective dependence of (13)C and (31)P NMR chemical shifts on β by the use of program LETAGROP, we obtained very good fitting for the assumed coexistence of two complexes (CMPO)(2)·HP (C(2)) and CMPO.HP (C(1)). The logarithms of the respective stabilization constants log K(i) were found to be 7.518 (C(2)) and 4.581 (C(1)). The system dynamics was studied by measuring the transverse (1)H NMR relaxation using CPMG sequence with varying delays t(p) between the π pulses in the mixtures with β = 0.4-0.8. The following exchange correlation times were obtained: τ(10) = 2.35 × 10(-5), τ(20) = 0.82 × 10(-4), τ(21) = 0.45 × 10(-3) s. The DFT calculations support the conclusion that the complexes C(1) and C(2) are the main species in the mixtures of CMPO with HP. They also agree with the NMR and FTIR observation that the main site to which H(3) O(+) is bound is the P=O group, whereas the amide group does not form a strong bond with the ion when excess water molecules are present. 相似文献