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931.
The reaction of [Sb(2)W(22)O(74)(OH)(2)](12-) and [Fe(4)(H(2)O)(10)(β-TeW(9)O(33))(2)](4-) with (NH(4))(2)[RuCl(6)] in aqueous solution resulted in the novel ruthenium(IV)-containing polyanions [{Ru(IV)(4)O(6)(H(2)O)(9)}(2)Sb(2)W(20)O(68)(OH)(2)](4-) and [{Ru(IV)(4)O(6)(H(2)O)(9)}(2){Fe(H(2)O)(2)}(2){β-TeW(9)O(33)}(2)H](-), exhibiting two cationic, adamantane-like, tetraruthenium(IV) units {Ru(4)O(6)(H(2)O)(9)}(4+) bound to the respective polyanion in an external, highly accessible fashion. 相似文献
932.
Durá J Grün A Bates PK Teichmann SM Ergler T Senftleben A Pflüger T Schröter CD Moshammer R Ullrich J Jaroń-Becker A Becker A Biegert J 《The journal of physical chemistry. A》2012,116(11):2662-2668
We study ionization of molecules by an intense laser field over a broad wavelength regime, ranging from 0.8 to 1.5 μm experimentally and from 0.6 to 10 μm theoretically. A reaction microscope is combined with an optical parametric amplifier to achieve ionization yields in the near-infrared wavelength regime. Calculations are done using the strong-field S-matrix theory and agreement is found between experiment and theory, showing that ionization of many molecules is suppressed compared to the ionization of atoms with identical ionization potentials at near-infrared wavelengths at around 0.8 μm, but not at longest wavelengths (10 μm). This is due to interference effects in the electron emission that are effective at low photoelectron energies but tend to average out at higher energies. We observe the transition between suppression and nonsuppression of molecular ionization in the near-infrared wavelength regime (1-5 μm). 相似文献
933.
Katja Schladitz Claudia Redenbach Tetyana Sych Michael Godehardt 《Methodology and Computing in Applied Probability》2012,14(4):1011-1032
Open cell foams are a class of modern materials which is interesting for a wide variety of applications and which is not accessible to classical materialography based on 2d images. 3d imaging by micro computed tomography is a practicable alternative. Analysis of the resulting volume images is either based on a simple binarisation of the image or on so-called cell reconstruction by image processing. The first approach allows to estimate mean characteristics like the mean cell volume using the typical cell of a random spatial tessellation as model for the cell shape. The cell reconstruction allows estimation of empirical distributions of cell characteristics. This paper summarises the theoretical background for the first method, in particular estimation of the intrinsic volumes and their densities from discretized data and models for random spatial tessellations. The accuracy of the estimation method is assessed using the dilated edge systems of simulated random spatial tessellations. 相似文献
934.
The main goal of the present work is to provide an add-on scheme for the formulation of multibody dynamics, based on natural coordinates, in regard to ideally balanced rigid bodies with high rotational spin, e.g. gyroscopes. The underlying aim of this approach is to achieve higher numerical accuracy whenever the preferred axis of rotation coincides with the balanced main axis of the body. This will be achieved by seperating the spin of the balanced rigid body along the denoted axis as an additional angular coordinate, whereas the other rotations will be covered by a carried frame, parameterized via natural coordinates. At the same time the carried frame provides a link to the existing modelling framework in terms of natural coordinates, enabling a straightforward implementation into existing multibody systems (e.g. rotary crane [2]). (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
935.
The aim of this work is to develop a continuum multiphase model to describe infiltration processes for cohesionless soils. For this purpose, a Representative Volume Element (RVE) is considered and described by the continuum mixture theory extended by the concept of volume fractions (Theory of Porous Media – TPM). The thermodynamically consistent TPM is a macroscopical multiphase modeling approach, extended from classical single-phase continuum mechanics. Futhermore a 1-dim example for an infiltration problem is presented. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
936.
Katja Lappalainen Mikko Manninen Ville Alopaeus Juhani Aittamaa John Dodds 《Transport in Porous Media》2009,77(1):17-40
Capillary pressure is considered in packed-beds of spherical particles. In the case of gas–liquid flows in packed-bed reactors,
capillary pressure gradients can have a significant influence on liquid distribution and, consequently, on the overall reactor
performance. In particular, capillary pressure is important for non-uniform liquid distribution, causing liquid spreading
as it flows down the packing. An analytical model for capillary pressure–saturation relation is developed for the pendular
and funicular regions and the factors affecting capillary pressure in the capillary region are discussed. The present model
is compared to the capillary pressure models of Grosser et al. (AIChE J., 34:1850–1860, 1988) and Attou and Ferschneider (Chem.
Eng. Sci., 55:491–511, 2000) and to the experiments of Dodds and Srivastava (Part Part Syst. Charact., 23:29–39, 2006) and
Dullien et al. (J. Colloid Interface Sci., 127:362–372, 1989). The non-homogeneity of real packings is considered through
particle size and porosity distributions. The model is based on the assumption that the particles are covered with a liquid
film, which provides hydrodynamic continuity. This makes the model more suitable for porous or rough particles than for non-porous
smooth particles. The main improvements of the present model are found in the pendular region, where the liquid dispersion
due to capillary pressure gradients is most significant. The model can be used to improve the hydrodynamic models (e.g., CFD
and cellular automata models) for packed-bed reactors, such as trickle-bed reactors, where gas, liquid, and solid phases are
present. Models for such reactors have become quite common lately (Sáez and Carbonell, AIChE J., 31:52–62, 1985; Holub et al.,
Chem. Eng. Sci, 47, 2343–2348, 1992; Attou et al., Chem. Eng. Sci., 54:785–802, 1999; Iliuta and Larachi, Chem. Eng. Sci.,
54:5039–5045, 1999, IJCRE 3:R4, 2005; Narasimhan et al., AIChE J., 48:2459–2474, 2002), but they still lack proper terms causing
liquid dispersion. 相似文献
937.
A perturbation theory model that describes splitting of the spectra in highly symmetrical molecular species in electrostatic field is proposed. An anahrmonic model of a two-dimensional oscillator having Kratzer potential energy functionis used to model the molecular species and to represent the unperturbed system. A selection rule for the radial quantum number of the oscillator is derived. The eigenfunctions of a two-dimensional anharmonic oscillator in cylindrical coordinates are used for the matrix elements representing the probability for energy transitions in dipole approximation to be calculated. Several forms of perturbation operators are proposed to model the interactionbetween the polyatomic molecular species and an electrostatic field. It is found that the degeneracy is removed in the presence of the electric field and spectral splitting occurs. Anharmonic approximation for the unperturbed system is more accurate and reliable representation of a real polyatomic molecular species. 相似文献
938.
C. Becker J. Gspann R. Krämer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):301-304
Reactive accelerated cluster erosion (RACE) of single crystal artificial diamond has been used to fabricate various nano-
and microstructures. Carbondioxide clusters of about 1000 molecules are accelerated to 100 keV to act as the eroding agent.
Using movable shadow masks, the accelerated cluster beam may erode staircase structures acting as an optical grating. A cycloid
gear has been generated via a stationary nickel mask. Non-reactive accelerated cluster erosion using argon clusters will be considered for comparison.
Received 30 November 2000 相似文献
939.
Black gold layers, prepared by an evaporation process in an inert atmosphere, are an efficient absorber in the far infrared spectral region. Experimental results are presented for their reflectance in the wavelength range between λ=15 μm and 1000 μm, corresponding to a wave number k=1/λ between 10 cm−1 and 650 cm−1. The black gold layers may electrically be either metallic or semiconducting, the metallic ones exhibiting higher absorbance. The layers have a percolated structure whose dielectric properties are described by the Bergman formalism for an effective medium. On the basis of this model, the deviation of the optical properties of the layers from bulk gold are accounted for solely by the topology of the percolated structure. The values derived for the electron collision time in the gold particles and for the percolation factor agree with those derived from the electrical conductivity of the layers and its temperature dependence. 相似文献
940.
The plane problem of an elliptically reinforced circular hole in an anisotropic plate or laminate 总被引:11,自引:0,他引:11
Summary Within the scope of linear elasticity, the in-plane problem of an anisotropic plate or laminate with a circular hole and
an elliptical hole reinforcement is considered. Arbitrary anisotropic elastic stiffnesses are allowed for the base plate and
the reinforcement material, and for the reinforcement there is no restriction for its elliptical shape and size. The analysis
of the problem is performed by the complex potential method with appropriately chosen series representations inside and outside
the reinforcement region. The derived closed-form solution provides all resultant in-plane stresses and deformations within
and around the hole reinforcement with little computational effort and at high accuracy. The determined solution allows a
proper and effective assessment of hole reinforcements for many technical applications.
Received 26 June 2000; accepted for publication 26 September 2000 相似文献