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991.
Classical composition algebras, with a unit element, are well-known and can be obtained by means of the Cayley-Dickson doubling
process. If the condition on the existence of unit element is dropped, many new algebras arise. However, it is shown in this
paper that if such a weak condition as the associativity of third powers of any element is imposed, only the known flexible
composition algebras appear.
Partially supported by the DGICYT (PS 90-0129) and by the DGA (PCB-6/91)
Supported by a grant from the ‘Plan de Formación del Personal Investigador’ (DGICYT, Spain)
This article was processed by the authors using the Springer-Verlag TEX P Jour1g macro package 1991. 相似文献
992.
The present work deals with the numerical calculation of the incompressible turbulent flow around aerofoils. An orthogonal curvilinear grid of ‘C’ type is used for the solution of the time averaged equations and Reynolds stresses are modelled according to the κ-ε turbulence model. PISO and SIMPLE algorithms are used to solve the strongly coupled system of the derived finite volume equations and convergence is improved by applying the method of variable local underrelaxation factors. Comparisons between the calculated and measured pressure distributions are presented for NACA 0012 and NACA 4412 wing sections. The formation of separation bubbles according to calculations is also shown. 相似文献
993.
José María Mínguez 《Experimental Mechanics》1986,26(3):238-244
How accurate, simply supported boundary conditions can be obtained experimentally in the testing of rectangular panels subjected
to uniaxial compression has been investigated. Experimental buckling loads are obtained using the Southwell method and are
compared with theoretical predictions. Several support arrangements are examined and compared to the idealized support conditions. 相似文献
994.
José L. Fernández 《Mathematische Zeitschrift》1986,193(3):393-396
995.
Igor E. Shparlinski José Felipe Voloch 《Bulletin of the Brazilian Mathematical Society》2008,39(3):417-425
We view an algebraic curve over ℚ as providing a one-parameter family of number fields and obtain bounds for the average value
of some standard prime ideal counting functions over these families which are better than averaging the standard estimates
for these functions.
相似文献
996.
The macroscopic dynamics of a kinetic equation involving a model wave-particle collision operator of plasma physics is investigated.
The Chapman-Enskog asymptotics is first considered in the framework of a hydrodynamic scaling. The obtained macroscopic model
still involves a kinetic variable, the particle energy in the rest frame of the fluid, but shares similarities with the compressible
Navier-Stokes equation of gas dynamics. Then a diffusive scaling is examined under the hypothesis of small perturbations of
a global equilibrium. In this case, the macroscopic model couples the usual incompressible Navier-Stokes with a diffusion
equation for the energy distribution function of the particles, constrained by an extended version of the Boussinesq relation.
In both cases, the effect of a Lorentz force term is developed, in the perspective of plasma physical modelling.
Received June 16, 1997 相似文献
997.
José María Mínguez 《Experimental Mechanics》1988,28(4):336-339
The influence of torsional ridigity of the stiffeners on the buckling of reinforced aluminum-alloy panels has been investigated. Experimental results reveal that stiffener torsional rigidity must be introduced in the analysis of compressed panels, for, if the stiffener has a closed cross section, the stiffener shape may change the buckling mode shape essentially and increase the critical load considerably.José María Mínguez was Postgraduate Student in Engineering, Metallic Structures Group, University of Bath, United Kingdom 相似文献
998.
Jos Derksen 《Flow, Turbulence and Combustion》2002,69(1):3-33
Turbulent, swirling flows are encountered frequently in chemical engineering practice. In this article, experiments and simulations
on two classes of swirling flows, viz. agitated flows (stirred tanks), and confined swirling flows are discussed. Results
of large-eddy simulations of stirred tank flow are compared with experimental data, mainly phase-resolved LDA data of the
flow in the vicinity of the impeller. Next to the average velocity field, also the turbulent kinetic energy, and the anisotropy
of the Reynolds stress tensor have been assessed. An important application of confined swirling flow is the cyclone separator
(hydrocyclones for the separation of liquids, gas cyclones for gas-solid separation). The flow in a swirl tube geometry exhibiting
many of the typical features of swirl flows (e.g. vortex breakdown) is discussed. Furthermore, a large-eddy simulation of
the gas flow in a high-efficiency Stairmand cyclone separator is presented. Two examples of process modeling based on flow
simulations are briefly treated: orthokinetic agglomeration of crystals in a stirred tank, and particle separation in a cyclone.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
999.
Prof. Ibon Alkorta Dr. Christophe Dardonville Prof. José Elguero 《Angewandte Chemie (International ed. in English)》2015,54(13):3997-4000
The first example in the literature of a compound showing anisochronous 15N atoms resulting from diastereotopicity is described. Racemic 1,3‐dimethyl‐2‐phenyloctahydro‐1H‐benzimidazole was prepared and studied by 1H, 13C and 15N NMR spectroscopy. If convenient conditions were used (monitored by theoretical calculations of 2JN‐H spin–spin coupling constants), two 15N NMR signals were observed and corresponded to the diastereotopic atoms. GIAO/density‐functional calculations of chemical shifts were not only in good agreement with the experimental values but also served as prediction tools. This study suggests that 15N NMR spectroscopy could be used to probe chirality. 相似文献
1000.
Carboxylic‐Acid‐Passivated Metal Oxide Nanocrystals: Ligand Exchange Characteristics of a New Binding Motif 下载免费PDF全文
Jonathan De Roo Dr. Yolanda Justo Katrien De Keukeleere Freya Van den Broeck Prof. Dr. José C. Martins Prof. Dr. Isabel Van Driessche Prof. Dr. Zeger Hens 《Angewandte Chemie (International ed. in English)》2015,54(22):6488-6491
Ligand exchange is central in the processing of inorganic nanocrystals (NCs) and requires understanding of surface chemistry. Studying sterically stabilized HfO2 and ZrO2 NCs using 1H solution NMR and IR spectroscopy as well as elemental analysis, this paper demonstrates the reversible exchange of initial oleic acid ligands for octylamine and self‐adsorption of oleic acid at NC surfaces. Both processes are incompatible with an X‐type binding motif of carboxylic acids as reported for sulfide and selenide NCs. We argue that this behavior stems from the dissociative adsorption of carboxylic acids at the oxide surface. Both proton and carboxylate moieties must be regarded as X‐type ligands yielding a combined X2 binding motif that allows for self‐adsorption and exchange for L‐type ligands. 相似文献