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991.
A solid-phase extraction (SPE) procedure that fractionates wine samples into 2 sub-samples containing sugars and organic acids (sub-sample 1) and low molecular weight polyphenols (sub-sample 2), respectively, together with rugged LC procedures for their analyses are described. Wine is adjusted to pH 2.5 and loaded on a styrene-divinylbenzene (SDB) cartridge. The organic acids and sugars are eluted with 20 mM sulphuric acid and the monomeric polyphenols with ethyl acetate. Glucose and fructose are analysed by normal phase LC with evaporative light scattering detection and the organic acids by ion exclusion chromatography with UV detection at 210 nm. Analysis of the phenolic fraction is performed by reversed phase LC with diode array detection. Recoveries and repeatabilitys for 27 standard compounds (2 sugars, 7 organic acids and 18 polyphenols) are presented. The method represents an improvement in terms of productivity and robustness compared to currently used procedures. 相似文献
992.
Boundedness in Morrey spaces is studied for singular integral operators with kernels of mixed homogeneity and their commutators with multiplication by a BMO-function. The results are applied in obtaining fine (Morrey and Hölder) regularity of strong solutions to higher-order elliptic and parabolic equations with VMO coefficients. 相似文献
993.
Christophe Lerot Ghislain Blanquet Muriel Lepère 《Journal of Molecular Spectroscopy》2003,217(1):79-86
Using a tunable diode-laser spectrometer, we have measured at room temperature the H2-broadening coefficients of for 36 lines belonging to QP and QR branches in the ν3 parallel band. The recorded lines with J values ranging from 1 to 15 and K from 0 to 9 (K?J) are located between 1196 and 1412 cm−1. The H2-broadening coefficients were determined by fitting each spectral line with Voigt, Rautian, and Galatry profiles. They were also calculated on the basis of a semiclassical model of interacting linear molecules performed by considering in addition to the weak electrostatic contributions the atom-atom Lennard-Jones potential. The theoretical results are in reasonable agreement with the experimental data, except for high J transitions where they are overestimated and for K approaching or equal to J with J?3 where they are underestimated. The latter discrepancy may be caused by the assumption to consider only ΔK=0 collision-induced transitions, associated with |ΔJ| transitions up to 4. 相似文献
994.
A. A. Belov F. Firszt V. S. Gorelik A. L. Karuzskii E. I. Mahov H. Męczyńska A. V. Perestoronin P. P. Sverbil' J. Szatkowski 《Journal of Russian Laser Research》2003,24(1):14-26
Investigations of photoluminescence and Raman scattering in the ternary Zn1-xMgxSe compounds at 4.2 K were performed both in the Stokes and anti-Stokes regions using cw laser excitation with various wavelengths within the transparency band of the crystals. The anti-Stokes luminescence was observed for the first time in the ternary Zn1-xMgxSe compounds. We have found variations in the shape and position of the Stokes and anti-Stokes luminescence bands with an increase in the band gap energy, which depends on magnesium content. We assume that the anti-Stokes emission is generated by two-step excitation via deep-level centers. It is shown that the low-temperature anti-Stokes photoluminescence can probe the spatial distribution profiles of impurities in the bulk of crystals. 相似文献
995.
Two-center nuclear attraction integrals over Slater type orbitals with integer and noninteger principal quantum numbers in nonlined up coordinate systems have been calculated by means of formulas in our previous work (T. Özdoan and M. Orbay, Int. J. Quant. Chem. 87 (2002) 15). The computer results for integer case are in best agreement with the prior literature. On the other hand, the results for noninteger case are not compared with the literature due to the scarcity of the literature, but also compared with the limit of integer case and good agreements are obtained. The proposed algorithm for the calculation of two-center nuclear attraction integrals over Slater type orbitals with noninteger principal quantum numbers in nonlined-up coordinate systems permits to avoid the interpolation procedure used to overcome the difficulty introduced by the presence of noninteger principal quantum numbers. Finally, numerical aspects of the presented formulae are analyzed under wide range of quantum numbers, orbital exponents and internuclear distances. 相似文献
996.
997.
散射参考光法制作真彩色全息图 总被引:2,自引:1,他引:1
本文提出了用散射参考光制作2D真彩色全息图的原理,按本原理制作的全息图比用散射物光法制作的图像清晰得多,并且使记录激光能量得到充分利用,特别适用于记录大幅面彩色全息图。 相似文献
998.
Jerk Influence Coefficients,via Screw Theory,of Closed Chains 总被引:2,自引:0,他引:2
In this paper a novel method for determining the kinematic influence coefficients up to the jerk analysis of closed chains with multiple degrees of freedom by means of screw theory, also known as motor algebra, is introduced. A closed chain is obtained by rigidly attaching the end-effector of a serial chain to the base link. This condition ensures that the velocity, acceleration, and jerk, both angular and of any point fixed to the end-effector are zero. Afterwards, a comparison between the kinematic equations of motion, up to the jerk analysis, obtained by traditional methods with those obtained by means of screw theory reveals the corresponding influence coefficients associated to the generalized coordinates employed to represent the motion of the closed chain. Finally, a numerical example is provided.
Sommario. In questo lavoro viene proposto un nuovo metodo per la determinazione dei coefficienti che consentono di sviluppare l'analisi cinematica (jerk incluso) di catene chiuse a molti gradi di liberta' per mezzo della screw theory o algebra dei moti spaziali. La catena chiusa e' ottenuta attaccando rigidamente l'end-effector di una catena seriale al membro di base. Questa condizione assicura che velocita' accelerazione e jerk, sia nel moto angolare che per ciascun punto solidale con l'end-effector siano nulli. Un confronto tra le equazioni cinematiche del moto, inclusa l'analisi del jerk, ottenute con metodi tradizionali e quelle ottenute dalla screw theory, mostra i corrispondenti coefficienti di influenza associati alle coordinate generalizzate impiegate per descrivere il moto della catena chiusa. Un esempio numerico conclude il lavoro. 相似文献
999.
Paul F. Fewster Vaclav Holy Norman L. Andrew 《Materials Science in Semiconductor Processing》2001,4(6):321
Some of the most important material systems, GaInN alloys and quantum dot structures create interesting and complex challenges for structural analysis. This paper concentrates on the interpretation of the microstructure of both these materials, the former to assess the defect separation and the latter to obtain the shape and composition of the quantum dots. The methods used are based on mapping the X-ray intensity in reciprocal space and simulating proposed models to achieve good agreement with the experimental results. An indication of the reliability of these methods is presented.The simulation of the 0002 reciprocal space map of a 0 0 0 1 orientated InGaN/GaN sample yielded a range of dimensions of the perfect regions between defects of 60 and 220 μm. This comes from careful fitting of the tails of the scattering parallel to the surface plane. The average composition within an InGaAs quantum dot has been determined to a reliability of ±3% and the dimensions of these buried dots evaluated from simulating the reciprocal space maps using the in-plane scattering geometry. 相似文献
1000.
Melting points in mixtures of a crystallizable polymer
with a low-molar-mass diluent depend on both, the diluent
fraction and the crystal thickness. A differentiation of the two
factors can be achieved by temperature-dependent SAXS
experiments. A corresponding study, complemented by DSC,
dilatometry, microscopy and AFM-imaging, was carried out for
mixtures of a poly(ethylene-co-octene) with
n-C16H34,
c-C16H32
and methyl-anthracene, respectively. All diluents lead for a
constant crystal thickness to melting point depressions in
agreement with Raoult's law. On the other hand, the effect of
the diluents on the thickness of the crystals formed at a fixed
crystallization temperature varies. While in the presence of the
two alkanes thicker crystals form, no effect arises for the
methyl-anthracene—as was previously found for the
octene-co-units. We consider these observations as a further
support for our view that polymer crystallization follows a
multi-stage route which includes a passage through an
intermediate mesomorphic phase. Under such conditions crystal
thicknesses would only be affected if the diluent is still
present in the mesomorphic phase and stay invariant if the
diluent molecules are already rejected when this intermediate
phase forms. 相似文献