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151.
Nitrido-Silicates. II. High Temperature Syntheses and Crystal Structures of Sr2Si5N8 and Ba2Si5N8 Pure Sr2Si5N8 and Ba2Si5N8 were obtained by reaction of silicon diimide with metallic strontium and barium, respectively. The reactions have been carried out under nitrogen atmosphere in a specially developed high-frequency furnace at temperatures between 1 550 and 1 650°C. Sr2Si5N8 (Pmn21, a = 571.0(2), b = 682.2(2), c = 934.1(2) pm, Z = 2, R = 0.037, wR = 0.021) and Ba2Si5N8 (Pmn21, a = 578.3(2), b = 695.9(2), c = 939.1(2) pm, Z = 2, R = 0.022, wR = 0.018) are isotypic and contain M2+ ions as well as a three-dimensional covalent network structure of corner-sharing SiN4 tetrahedra. Two sorts of N occur with molar ratio 1 : 1 which are bonded to two and three Si, respectively. Predominantly, the N which are bonded to two Si belong to the coordination spheres of the M2+ ions. 相似文献
152.
153.
Z. M. Khakimov F. T. Umarova N. T. Sulaymonov A. E. Kiv A. A. Levin 《International journal of quantum chemistry》2003,93(5):351-359
New model of Si? H bond dissociation is proposed and tested in the cluster Si10H16 by the simulation approach that combines classic molecular dynamics method and the self‐consistent tight‐binding electronic and total energy calculation one. It is shown that the monohydride Si? H bond is unstable with respect to silicon dangling bond and bend‐bridge Si? H? Si bond formation when this cluster traps the single positive charge and that hydrogen migrates through a path involving rather rotation around the Si? Si bond than the center of this bond (the bond‐centered position). These results can be useful for understanding hydrogen‐related phenomena at surfaces, interfaces, and internal voids of various hydrogenated silicon systems: electronic devices, silicon solar cells, and nanocrystalline and porous silicon. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 93: 351–359, 2003 相似文献
154.
XRF分析铁矿粉的标准选择判据研究和应用 总被引:2,自引:0,他引:2
本文对XRF法分析铁矿的基体校正元素进行了研究,并建立了标准选择判据,编制的计算软件可以自动地从大量标样中选择适合该样品分析的标准。该法可用于粉末压片制样的分析,方法快速,准确度和精密度均符合生产要求。 相似文献
155.
V. V. Semenov N. F. Cherepennikova A. N. Kornev E. V. Naamova N. P. Makarenko S. Ya. Xhorshev G. A. Domrachev O. A. Bochkova 《Russian Chemical Bulletin》1996,45(10):2431-2437
Oligo(phenylcobaltcarbonylsilane) was prepared from oligo(phenylsilane) and dicobalt octacarbonyl. The reaction proceeds with elimination of H2 and CO and insertion of cobalt carbonyl fragments into the silicone backbone of oligosilane. Oligosilane containing cobalt carbonyl groups in side organic substituents was obtained from oligolmethyl(phenylethynyl)Isilane and CO2(CO)8. The reaction of 1,2-bis(phenylethyny1)tetramethyldisilane with Co2(CO)8 proceeds with the sequential attachment of cobalt carbonyl fragments to ethynyl groups to form disilane derivatives [2-CCPhCo2(CO)6] Thermal decomposition of cobalt-containing oligosilanes affords a mixture of paramagnets and ferromagnets.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya. No. 10, pp. 2561–2567, October, 1996. 相似文献
156.
In this contribution we propose a simple model of adsorption of a binary (racemic) mixture on a chiraly templated surface. As an example, the adsorption of a liquid mixture of enantiomers on a chiral stationary phase (CSP) is considered. In particular, we study the effect of the lateral interactions in the adsorbed phase on the kinetic and equilibrium isotherms of the enantiomers. Additionally, we investigate the influence of the composition of the surface on the performance of the CSP in the presence of the lateral interactions. To that end, the adsorption of the mixture is modeled by using Monte Carlo simulations as well as by applying an analytical approach involving rate equations coupled with the Mean Field Approximation (MFA). The predictions of the theory are found to be in good agreement with the results of the simulations. 相似文献
157.
Paul G. Mezey 《Theoretical chemistry accounts》1985,67(1):43-61
The family of all possible reaction mechanisms on a potential surface has an algebraic structure with potential applications in quantum chemical molecular design and synthesis planning.Transformation properties and equivalence relations of reaction paths on potential energy hypersurfaces lead to a topological definition of reaction mechanisms. The family of all fundamental reaction mechanisms on the hypersurface has a group structure,the fundamental group of an appropriately defined topological space. Isomorphism and homomorphism relations between fundamental groups of reaction mechanisms are used to characterize the chemically important topological properties of various subsets of a hypersurface, or those of different excited state hypersurfaces. 相似文献
158.
159.
A sample pretreatment technique for silicon nitride involving digestion and matrix/traces separation was developed by means of radiotracers and applied to analysis of this material by inductively coupled plasma atomic emission spectrometry, inductively coupled plasma mass spectrometry and graphite furnace atomic absorption spectrometry. The results obtained for a high purity silicon nitride material by these methods are compared each with the other and with those obtained by neutron activation analysis. The limits of detection and the capabilities of the methods are compared and discussed. 相似文献
160.