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981.
Mar'yana Lukachuk Birgit Heying Ute Ch. Rodewald Rainer Pttgen 《Heteroatom Chemistry》2005,16(5):364-368
The ternary indides Sc5 Ni2 In4 and Sc5 Rh2 In4 were synthesized by arc‐melting of the elements and subsequent annealing. A structural investigation by X‐ray powder and single crystal diffraction revealed: Lu5 Ni2 In4 type, Pbam, a = 1716.3(2), b = 755.1(1), c = 335.22(5) pm, wR2 = 0.0721, 844 F2 values for Sc5 Ni2 In4, and a = 1754.3(3), b = 765.0(1), c = 332.97(6) pm, wR2 = 0.0363, 1107 F2 values for Sc5 Rh2 In4 with 36 variables per refinement. Both structures can be described as intergrowths of distorted AlB2‐ and CsCl‐related slabs, where the transition metal (T) atoms have a trigonal prismatic and the indium atoms a distorted square prismatic coordination. The shortest interatomic distances occur for Sc T and T In. The crystal chemistry and chemical bonding in these intermetallics are briefly discussed. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:364–368, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20106 相似文献
982.
Johannis Ch. Simitzis Loukas Th. Zoumpoulakis Spiridon K. Soulis Leonidas N. Mendrinos 《Mikrochimica acta》2001,136(3-4):171-174
Unsaturated polyesters are synthesized by means of polyesterification, often with catalysts like strong acids, metal oxides
and metal-organic salts. Most often, the catalysts used cannot be separated from the bulk of the polyester. Also, some organic
or inorganic additives – called fillers – which are used with the polyester in order to decrease cost, affect the curing of
the polyester. In this work the effect of residual catalyst on the curing of unsaturated polyester is studied. Unsaturated
polyesters were prepared using propylene glycol with a 10% molar excess over stoichiometry and a mixture of dicarboxylic acids,
namely maleic acid (unsaturated) adipic acid (saturated) and phthalic anhydride (saturated) at a molar ratio 1:2:2. Lead dioxide,
p-toluenesulfonic acid and zinc acetate were used as catalysts, at 0.1% w/w. After the polyesterification, the polymers were
diluted with styrene at a proportion of 100:30 w/w. The resins were cured by using MEKP (methylethylketone peroxide) as initiator
and CoNp (cobalt naphthenate) as accelerator. Catalysts affect the final color of the polyester. The kinetics of curing of
the resins was studied by DSC analysis based on the exothermic peak due to the double bonds breaking to give crosslinked macromolecules.
The heat released ΔH is decreased by the presence of catalyst, while activation energy, the frequency factor and the order of reaction are increased. 相似文献
983.
J. Ch. Abbe 《Journal of Radioanalytical and Nuclear Chemistry》2001,249(3):565-567
Analyses of uranium and thorium by delayed neutron counting are described.The experimental system comprises an automatic pneumatic transfer system associatedwith a device made of twelve BF 3 neutron counters. Using homogeneous preparedsolutions of the samples, the analyses were based on a triple cycle each including60-second irradiation followed by 1-second cooling and 60-second counting.In these conditions, the limit of detection of uranium is about 0.3 µgwith a precision of measurement better than 10%. The contributions of possibleperturbations from 17 O(n,p)17 N reactions, followed by simultaneous –disintegration and neutron emission and from (n) reactions, have been studied. 相似文献
984.
Vibrational circular dichroism (VCD) in the past two decades has developed into a powerful new structural tool. A concise
review of the applications of VCD to determine the structures of various biological molecules, namely peptides and proteins,
nucleic acids and carbohydrates, is provided.
Received: 31 August 1999 / Revised: 2 November 1999 / Accepted: 14 November 1999 相似文献
985.
Fractions containing metallothioneins (MT’s), extracted from the liver cytosol of humans, were analysed to determine the complete distribution pattern of the metals copper, cadmium and zinc. Samples of cirrhotic livers which had come from organs removed during transplantation were examined for differences in the trace-element binding pattern. After the extraction of supernatants from the tissue samples, membrane ultrafiltration of the cytosolic solution was carried out to separate all high-molecular proteins with molecular weights >100 kDa. This procedure retains the metal content of the MT’s in its initial form, in contrast to the often-used heat treatment of samples, which changes the copper distribution significantly. The MT’s themself were isolated using size exclusion and anion exchange chromatography. Their metal content was determined simultaneously on-line by combination with an ICP-AES as element detector. Calibration of the procedure was performed by means of a column by-pass-injection of elemental standards into the separation system. The MT content in the samples was calculated using the determined metal concentrations and the generally accepted metal/protein ratios for Cu (12:1), Cd (7:1) and Zn (7:1). These values were compared with values resulting from a 109Cd-saturation-assay. When various liver samples of different pathogenesis were compared, the highest level of Cu-MT was found in primary biliary cirrhosis. 相似文献
986.
M. Kaspar H. Stadler T. Weiß Ch. Ziegler 《Analytical and bioanalytical chemistry》2000,366(6-7):602-610
A short overview of function and experimental set-ups of acoustic wave devices is given which, in contrast to other bioanalysis techniques, are based on a mechanical transduction mechanism. The most frequently used device is the thickness shear mode resonator (TSMR), which in the last few years was intensively employed in biosensor applications. TSMR biosensor studies in the field of nucleic acid interaction, adsorption of proteins to surfaces and immunosensing are reviewed. A main point concerns the interpretation of the sensor response not only in terms of mass loading, which underestimates the capabilities of these devices. 相似文献
987.
In situ reflection high energy electron diffraction (RHEED) has been used to study the time evolution during self-assembled molecular beam epitaxy (MBE) growth of InAs quantum dots on GaAs. Using a special data acquisition technique, two characteristic time constants are determined very precisely: the time tc up to the first appearance of InAs dots and the time tf it takes to complete the 2D–3D transition of all islands. Surprisingly, we find that tc increases with temperature which disagrees with a thermally activated process. In contrast to this, tf behaves Arrhenius-like and an activation energy of Ef0.39 eV is determined. Furthermore, the sum tc+tf does not depend significantly on temperature and corresponds to an InAs coverage of 2.0 monolayers. A second focus of this paper is the study of dissolution of InAs dots after interruption of the As flux. From the experiments, an activation energy of 3.2 eV for desorption of In located on top of the wetting layer is determined, whereas direct desorption from the wetting layer corresponds to an activation energy of 3.4 eV. 相似文献
988.
G.Ch. Pflug A. Świętanowski E. Dockner H. Moritsch 《Annals of Operations Research》2000,99(1-4):189-206
The AURORA financial management system under development at the University of Vienna is a modular decision support tool for portfolio and asset–liability management. It is based on a multivariate Markovian birth-and-death factor model for the economic environment, a pricing model for the financial instruments and an objective function which is flexible enough to express risk aversion.The core of the system is a large scale linear or convex program, which due to its size and structure is well suited for parallel optimization methods.As the system is still at an early stage of development, the results are preliminary in nature. Only a few types of financial instruments are handled and just two types of objectives are considered. The parallel optimization modules are still in the development phase. 相似文献
989.
Micropolar and micromorphic solids are continuum mechanics models, which take into account, in some sense, the microstructure of the considered real material. The characteristic property of such continua is that the state functions depend, besides the classical deformation of the macroscopic material body, also upon the deformation of the microcontinuum modeling the microstructure, and its gradient with respect to the space occupied by the material body. While micropolar plasticity theories, including non-linear isotropic and non-linear kinematic hardening, have been formulated, even for non-linear geometry, few works are known yet about the formulation of (finite deformation) micromorphic plasticity. It is the aim of the three papers (Parts I, II, and III) to demonstrate how micromorphic plasticity theories may be formulated in a thermodynamically consistent way.In the present article we start by outlining the framework of the theory. Especially, we confine attention to the theory of Mindlin on continua with microstructure, which is formulated for small deformations. After precising some conceptual aspects concerning the notion of microcontinuum, we work out a finite deformation version of theory, suitable for our aims. It is examined that resulting basic field equations are the same as in the non-linear theory of Eringen, which deals with a different definition of the microcontinuum. Furthermore, geometrical interpretations of strain and curvature tensors are elaborated. This allows to find out associated rates in a natural manner. Dual stress and double stress tensors, as well as associated rates, are then defined on the basis of the stress powers. This way, it is possible to relate strain tensors (respectively, micromorphic curvature tensors) and stress tensors (respectively, double stress tensors), as well as associated rates, independently of the particular constitutive properties. 相似文献
990.
R. Rojas-Díaz A. Sáez F. García-Sánchez Ch. Zhang 《International Journal of Solids and Structures》2008,45(1):144-158
Two-dimensional (2-D) and three-dimensional (3-D) time-harmonic Green’s functions for linear magnetoelectroelastic solids are derived in this paper by means of Radon-transform. Displacement field and electric and magnetic potentials in a fully anisotropic magnetoelectroelastic infinite solid due to a time-harmonic point force, point charge and magnetic monopole are obtained in form of line integrals over a unit circle in 2-D case and surface integrals over a unit sphere in 3-D case. This dynamic fundamental solution is then split into the sum of regular dynamic plus singular terms. The singular terms coincide with the Green’s functions for the static problem and may be further reduced to closed form expressions. The proposed Green’s functions can be used in the corresponding boundary element method (BEM) formulation. 相似文献