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111.
Steady-state simulations of fluid flow and temperature field are presented for an equipment that is used to grow Zinc Selenide single crystals from the gaseous phases via physical (PVT) or chemical vapour transport (CVT). Due to the horizontal arrangement of the air-filled furnace pipe calculating the natural convection in the air requires a 3D (three-dimensional) treatment of the problem. The simulations have been done by applying the commercial finite-element package FIDAP. The Navier-Stokes equation is solved with the Boussinesq approximation. The heat transfer analysis comprises also internal radiation wall-to-wall exchange. Due to the presence of the ampoule in the pipe, the development of vortices with higher velocities is restrained, so that the maximum velocity is roughly 1/4 of that in the case without an ampoule. 相似文献
112.
Crystals of the title compound were obtained by annealing a powder of Tl2Te3 in a vertical temperature gradient (230 °C–240 °C, 4 weeks). Tl2Te3 crystallizes in space group C2/c with lattice parameters of a = 13.275(1) Å, b = 6.562(1) Å, c = 7.918(1) Å, and β = 107.14°(2). The tellurium atoms form chains [Te32–], consisting of interconnected linear triatomic · Te–^Te–Te · groups which are isosteric with XeF2. The Te–Te distances of the XeF2-like units are 3.02 Å, the connecting ones 2.83 Å. 相似文献
113.
Coordinatively Unsaturated Diruthenium Complexes: Synthesis and X‐ray Crystal Structures of [Ru2(CO)n(μ‐H)(μ‐PtBu2)(μ‐Ph2PCH2PPh2)] (n = 4; 5) and [Ru2(CO)4(μ‐CH2)(μ‐H)(μ‐PtBu2)(μ‐Ph2PCH2PPh2)] The reaction of [Ru2(μ‐CO)(CO)5(μ‐H)(μ‐PtBu2)(tBu2PH)] ( 2 ) with dppm yields the dinuclear species [Ru2(μ‐CO)(CO)4(μ‐H)(μ‐PtBu2)(μ‐dppm)] ( 3 ) (dppm = Ph2PCH2PPh2). Under thermal or photolytic conditions 3 loses very easily one carbonyl ligand and affords the corresponding electronically and coordinatively unsaturated complex [Ru2(CO)4(μ‐H)(μ‐PtBu2)(μ‐dppm)] ( 4 ). 4 is also obtainable by an one‐pot synthesis from [Ru3(CO)12], an excess of tBu2PH and stoichiometric amounts of dppm via the formation of [Ru2(CO)4(μ‐H)(μ‐PtBu2)(tBu2PH)2] ( 1 ). 4 exhibits a Ru–Ru double bond which could be confirmed by addition of methylene to the dimetallacyclopropane [Ru2(CO)4(μ‐CH2)(μ‐H)(μ‐PtBu2)(μ‐dppm)] ( 5 ). The molecular structures of 3 , 4 and 5 were determined by X‐ray crystal structure analyses. 相似文献
114.
Coordinatively Unsaturated Diiron Complexes: Synthesis and Crystal Structures of [Fe2(CO)4(μ‐H)(μ‐PtBu2)(μ‐Ph2PCH2PPh2)] and [Fe2(CO)4(μ‐CH2)(μ‐H)(μ‐PtBu2)(μ‐Ph2PCH2PPh2)] [Fe2(μ‐CO)(CO)6(μ‐H)(μ‐PtBu2)] ( 1 ) reacts spontaneously with dppm (dppm = Ph2PCH2PPh2) to give [Fe2(μ‐CO)(CO)4(μ‐H)(μ‐PtBu2)(μ‐dppm)] ( 2 c ). By thermolysis or photolysis, 2 c loses very easily one carbonyl ligand and yields the corresponding electronically and coordinatively unsaturated complex [Fe2(CO)4(μ‐H)(μ‐PtBu2)(μ‐dppm)] ( 3 ). 3 exhibits a Fe–Fe double bond which could be confirmed by the addition of methylene to the corresponding dimetallacyclopropane [Fe2(CO)4(μ‐CH2)(μ‐H)(μ‐PtBu2)(μ‐dppm)] ( 4 ). The reaction of 1 with dppe (Ph2PC2H4PPh2) affords [Fe2(μ‐CO)(CO)4(μ‐H)(μ‐PtBu2)(μ‐dppe)] ( 5 ). In contrast to the thermolysis of 2 c , yielding 3 , the heating of 5 in toluene leads rapidly to complete decomposition. The reaction of 1 with PPh3 yields [Fe2(CO)6(H)(μ‐PtBu2)(PPh3)] ( 6 a ), while with tBu2PH the compound [Fe2(μ‐CO)(CO)5(μ‐H)(μ‐PtBu2)(tBu2PH)] ( 6 b ) is formed. The thermolysis of 6 b affords [Fe2(CO)5(μ‐PtBu2)2] and the degradation products [Fe(CO)3(tBu2PH)2] and [Fe(CO)4(tBu2PH)]. The molecular structures of 3 , 4 and 6 b were determined by X‐ray crystal structure analyses. 相似文献
115.
We introduce a model that interprets atmospheric increment statistics as a large scale mixture of subsets of isotropic statistics. When mixing is weak the same statistics as for isotropic turbulence is recovered while for strong mixing robust intermittency is obtained. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
116.
117.
J�rgen‐Hinrich Fuhrhop Christoph Bttcher Christian Draeger Werner Fudickar Andrea Schulz Christian Messerschmidt J�rg Zimmermann 《Macromolecular Symposia》2000,156(1):11-20
β‐Octasubstituted porphyrins form face‐to‐face dimers in solution, which are stabilized by π‐π′ interactions in case of π‐radical formation. Polymerization of viologen substituted zinc porphyrins leads depending on stereochemistry to micelles or wire pairs. Anionic porphyrins were also adsorbed to gold electrodes or colloids and entrapped in membrane gaps. Heterodimerization of these porphyrins adsorbed to solid phase surfaces and entrapped within a 2 nm membrane gap was detectable by fluorescence quenching. Ruthenium complexes with two bipyridyl and one dioctadecyl dipyridyl methylene malonate ligand form head‐to‐head dimers in aqueous solution. The octadecyl substituents of the dimer constituents point to opposite directions and large multilayer micelles are formed upon aggregatetion in water. They survive drying. Dimerization processes are discussed as common basis for the formation of four uncommon supramolecular assemblies. 相似文献
118.
Klaus Burger Christoph B?ttcher Lothar Hennig Samy A. Essawy 《Monatshefte für Chemie / Chemical Monthly》2004,8(2):865-877
A preparatively simple synthesis of N-linked glycopeptoids starting from iminodiacetic acid and glycosylamines, using hexafluoroacetone as protecting and activating reagent is described. 相似文献
119.
120.