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141.
German Urbina-Villalba Leonardo J. Rodriguez German R. Castro Fernando Ruette 《Journal of computational chemistry》1992,13(7):867-873
The electronic structure of cobalt silicide clusters Co7Si7 and Si7Co7 was studied in comparison to that of Co19 and Si17 clusters under the scope of the MINDO/SR method. Clusters Co7Si7 and Si7Co7 represent the environment of a cobalt atom and that of a silicon atom in the cobalt monosilicide bulk, respectively. It is found that the Co? Si bond is essentially sp in character with an indirect participation (by electrostatic interaction) of the cobalt d orbitals. Our calculations show a charge transfer from silicon to the d orbitals of cobalt via sp–sp interaction with an internal sp–d hybridization. The theoretical density of states for cobalt silicide clusters are reported and compared with experimental results of surface spectroscopies. © 1992 by John Wiley & Sons, Inc. 相似文献
142.
Fernando de Felice 《General Relativity and Gravitation》1991,23(2):135-149
In this paper we deduce the general pattern of the potential surfaces for time-like geodesics in the Curzon metric. We find that for fairly small energies and orbital angular momenta, the time-like geodesics group into two sets; the geodesics of one set tend to thez-axis asR=(r2+z2)1/2 0,R=0 being a directional singularity, the others tend to ther-axis. At low energies these two sets are detached but they merge together as the energy increases. Stable circular motion is confined to thez = 0-plane and an energy threshold for stationary motion exists and is equal (per unit of rest-mass energy) to 0.945, a value almost indistinguishable from that in the Schwarzschild space-time. 相似文献
143.
Yogiro Hama Fernando Silveira Navarra 《Zeitschrift fur Physik C Particles and Fields》1992,53(3):501-506
Transverse-momentum distributions of andK have been analyzed within a framework of the hydrodynamical model to obtain the
dependence of the collective transverse flow and the dissociation temperatureT
d inpp- and
-induced multiparticle production reactions. The main outcomes are the steadily increasing transverse flow and a slowly decreasingT
d as the incident energy increases. This behavior is in excellent agreement with early Landau's estimate. An extension of this to nucleus-nucleus collisions correctly gives account of the very soft component which has been observed in heavyion experiments. 相似文献
144.
145.
We consider the zero-temperature behavior of a disordered array of quantum rotators given by the finite-volume Hamiltonian: $$H_\Lambda = - \mathop \Sigma \limits_{x \in \Lambda } \frac{{h(x)}}{2}\frac{{\partial ^2 }}{{\partial \varphi (x)^2 }} - J\mathop \Sigma \limits_{\left\langle {x,y} \right\rangle \in \Lambda } \cos (\varphi (x) - \varphi (y))$$ , wherex,y∈Z d , 〈,〉 denotes nearest neighbors inZ d ;J>0 andh={h(x)>0,x∈Z d } are independent identically distributed random variables with common distributiondμ(h), satisfying ∫h ?δ dμ(h)<∞ for some δ>0. We prove that for anym>0 it is possible to chooseJ(m) sufficiently small such that, if 0<J<J(m), for almost every choice ofh and everyx∈Z d the ground state correlation function satisfies $$\left\langle {\cos (\varphi (x) - \varphi (y))} \right\rangle \leqq C_{x,h,J} e^{ - m\left| {x - y} \right|} $$ for ally∈Z d withC x,h,J <∞. 相似文献
146.
147.
Larry I. Shoer Kerrie I. Gell Jeffrey Schwartz 《Journal of organometallic chemistry》1977,136(2):c19-c22
Dialkylaluminum hydrides and Cp2ZrX2 (Cp = π5-C5H5; X = Cl, H, alkyl) were found to react by aggregation to give mixed ZrAl trihydride complexes containing ZrHAl bridges. Reactions of these mixed-metal hydrides are discussed and structural parallels between them and known aluminum hydride complexes are drawn. 相似文献
148.
Schwartz E. M. Grundstein V. V. Ievins A. F. 《Journal of Thermal Analysis and Calorimetry》1975,8(3):461-467
The possibility of detecting the direction of reaction of boric acid with polyol and its intermediate stages by means of the data obtained with a Derivatograph is shown. An equation is given for determining the average monomer number in polymers with terminal H and OH groups from weight loss data. In the interaction of boric acid with hexitols and pentitols, polymeric esters are formed. It is found that formation of complex polyolboric acid is the intermediate stage of each interaction.
相似文献149.
Potential distribution and coupling parameter theories are combined to interrelate previous solvation thermodynamic results and derive several new expressions for the solvent reorganization energy at both constant volume and constant pressure. We further demonstrate that the usual decomposition of the chemical potential into noncompensating energetic and entropic contributions may be extended to obtain a Gaussian fluctuation approximation for the chemical potential plus an exact cumulant expansion for the remainder. These exact expressions are further related to approximate first-order thermodynamic perturbation theory predictions and used to obtain a coupling-parameter integral expression for the sum of all higher-order terms in the perturbation series. The results are compared with the experimental global solvation thermodynamic functions for xenon dissolved in n-hexane and water (under ambient conditions). These comparisons imply that the constant-volume solvent reorganization energy has a magnitude of at most approximately kT in both experimental solutions. The results are used to extract numerical values of the solute-solvent mean interaction energy and associated fluctuation entropy directly from experimental solvation thermodynamic measurements. 相似文献
150.
Jiménez JC Chavarría B López-Macià A Royo M Giralt E Albericio F 《Organic letters》2003,5(12):2115-2118
[reaction: see text] A solid-phase method for the synthesis of tentoxin has been developed. Two key steps-dehydration and N-alkylation-are carried out while the peptide is anchored to the resin. The method, which has been validated by the preparation of a library of tentoxin analogues, should be applicable to the generation of further libraries that have the tentoxin scaffold structure, as well as other structures containing N-alkylated didehydroamino acids. 相似文献