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941.
The focus of the work is meso-scale analysis (scale level of the fabric unit cell) of textile composite deformation and failure. The surface strain measurement is used for: (1) experimental investigation, which includes study of strain distribution at various stages of deformation, plasticity detection, damage initiation; (2) numerical validation of the correspondent finite element (FE) models. Two examples are considered: carbon-epoxy triaxial-braided and glass polypropylene-woven composite. The surface strain measurement (by digital image correlation technique) accompanies the tensile tests, aiming at: (1) elastic anisotropic constants characterisation, (2) study of non-linear material behaviour (for the thermoplastic composite), (3) control of homogeneity of the macro-strain distribution, and (4) analysis of damage initiation in brittle composites. Validation of meso-FE models by strain measurements encounters difficulties arising from (1) resolution of the strain measurements, (2) irregularities of the initial structure such as random layer nesting, ply interaction, and deviation of yarns from their theoretical position, which affects the measured strain fields. The paper discusses these difficulties and demonstrates a qualitative agreement with the FE analysis of idealised composite configurations.  相似文献   
942.
The first representative of copper(II) dithiocarbamate complexes with an unusual type of structural organization is synthesized. According to the X-ray diffraction data, the layers of noncentrosymmetric mononuclear [Cu{S2CN(CH2)6}2] and centrosymmetric binuclear [Cu2?ub;S2CN (CH2)6?ub;4] molecules alternate in the crystalline lattice of copper(II) N,N-cyclo-hexamethylenedithiocarbamate. The mononuclear and binuclear forms of the complex are observed in the 2: 1 ratio. The thermal properties of the synthesized compound are studied by thermogravimetry and differential scanning calorimetry. The final product of the thermal destruction of the complex is CuS.  相似文献   
943.
The chemical composition of humic acids from brown coal (Aldrich) was determined by element analysis, 13C NMR spectroscopy, and potentiometric titration. The adsorption ability of humic acids with different biocides (cyproconasol, propiconasol, tebuconasol, irgarol 1051, and DCOIT) was studied. The adsorption ability of a mixture of biocides in aqueous solutions was higher than that of the individual components. The limiting concentration of humic acids at which adsorption of biocides was maximum was determined. Adsorption constants were calculated by the Freundlich equation for each biocide in aqueous solution.  相似文献   
944.
Densities of dilute solutions of 1,3-dimethyl-2-imiazolidinone in H2O and D2O, with the solute mole-fractions ranging up to 0.01, have been measured with an error of 1.5 · 10−5 g · cm−3 at (278.15, 288.15, 298.15, 308.15, 313.15, and 318.15) K and atmospheric pressure using a vibrating-tube densimeter. The partial molar volumes of the dissolved DMI (down to the infinite dilution) and solvent (H2O or D2O) as well as the excess molar volumes of the isotopically distinguishable solutions have been calculated. The effects of the solvent isotope substitution, solute concentration and temperature on the volume changes caused by DMI hydration have been considered. The obvious relationship between the D2O–H2O solvent isotope effects on the partial molar volume and enthalpy of solution of DMI has been discovered.  相似文献   
945.
Polyaniline films (further, CPANI) were obtained under the conditions of oxygen cathodic reduction in the aniline-containing solution on the electrodes of mixed indium tin oxide (ITO), graphite, and gold. CPANI films are characterized by redox processes in the potential ranges of 0.1–0.2 V and ~0.4 V (SCE). These processes are caused by the polymer chain fragments of different structure and the ratio between the peaks corresponding to these processes varies significantly as dependent on the synthesis conditions (electrode material, stirring, etc). The mechanism of electrode processes on CPANI is studied using the methods of cyclic voltammetry and quartz microgravimetry. It is found that only hydrogen cations and supporting electrolyte anions participate in the electrode process at the potentials of 0.1–0.2 V. The mechanism of redox processes on the obtained polymer films is discussed.  相似文献   
946.
Rhodium hydrido chloride pincer complex RhH(Cl)[2,6-(Bupt b2PO)b2Cb6Hb3] was synthesized and used for the preparation of new complexes with labile two-electron ligands Rh(L)[2,6-(Bupt b2PO)b2Cb6Hb3] (L = MeCN or S(CHb2)b4) and complexes with small molecules, such as CO, Ob2, Hb2, and Nb2.  相似文献   
947.
The complex bis(O,O′-diisobutyl dithiophosphato)platinum(II) (I) was obtained and characterized by solid-state 13C, 31P, and 195Pt CP/MAS NMR spectroscopy. In complex I, the dithiophosphate fragments are structurally equivalent with a predominantly orthorhombic tensor of the 31P chemical shift (η = 0.73). The tensor of the 195Pt chemical shift approximates to an axially symmetric one (for δzz> δxx and δyy), which suggests the existence of square chromophores [PtS4], as in cooperite (natural PtS). The crystal and molecular structures of complex I were determined from X-ray diffraction data. The Pt atom coordinates two Dtph ligands in a S,S′-anisobidentate fashion (the Pt-S bonds are nonequivalent: 2.315 and 2.329 Å) to form two four-membered chelate rings [PtS2P] with platinum as a spiro atom. The P-S bond length (1.997 and 1.986 Å), which is intermediate between the idealized lengths of the single and double phosphorus-sulfur bonds, suggests the delocalization of the π-electron density in the structural fragments PS2. In complex I, the electron shielding of the platinum nucleus in the direction perpendicular to the plane of the chromophore [PtS4] was found to be noticeably higher than that in cooperite. The thermal properties of complex I were examined by combined DSC-TG thermal analysis. The intermediate product of the thermolysis of complex I was platinum(II) dithiometaphosphate [Pt(S2PO)2] and the final thermolysis product was PtS.  相似文献   
948.
Polysalicylideneazomethines containing Ge and Sn atoms in the polymeric chain were prepared by polycondensation of N,N′,N″,N‴-tetrasalicylidene-3,3′,4,4′-tetraaminodiphenyl ether with germanium or tin tetrachloride or tetraethoxide. Spectroscopic examination showed that the polymers exhibit nonclassical polyconjugation and belong to a new class of semiconductor polytransannular-conjugated polymers.  相似文献   
949.
We consider the behavior of bounded solutions of quasilinear elliptic equations on a special class of Riemannian manifolds. We obtain sufficient conditions for the convergence of solutions to zero.  相似文献   
950.
Based on linearized equations of the theory of elastic stability of straight composite bars with a low shear rigidity, which are constructed using the consistent geometrically nonlinear equations of elasticity theory for small deformations and arbitrary displacements and a kinematic model of Timoshenko type, exact analytical solutions of nonclassical stability problems are obtained for a bar subjected to axial compression and torsion for various modes of end fixation. It is shown that the problem of direct determination of the critical parameter of the compressive load at a given torque parameter leads to transcendental characteristic equations that are solvable only if bar ends have cylindrical hinges. At the same time, we succeeded in obtaining solutions to these equations in terms of wave formation parameters of the bar; these parameters, in turn, enabled us to find the parameter of the critical load at any boundary conditions. Also, an algorithm for numerical solution of the problems stated is proposed, which is based on reducing the problems to systems of integroalgebraic equations with Volterra-type operators and on solving these equations by the method of mechanical quadratures (finite sums). It is demonstrated that such numerical solutions exist only for certain ranges of parameters of the bar and of the parameter of torque. In the general case, they can not be obtained by the numerical method used. It is also shown that the well-known solutions of the stability problem for a bar subjected to torsion or to compression with torsion are in correct. Translated from Mekhanika Kompozitnykh Materialov, Vol. 45, No. 2, pp. 167–200, March–April, 2009.  相似文献   
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