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721.
We present evidence that one of the elementary one-dimensional cellular automata in the sense of Wolfram (rule 22 in Wolfram's notation) involves very complex long-range effects, similar to a critical phenomenon. This is in contrast to superficial evidence that would suggest that this rule leads to fairly simple behavior. 相似文献
722.
Adsorption microcalorimetry was applied to determine heats of adsorption of ammonia on zeolites Y, mordenite, ZSM-5, heteropolyacid
H3PW12O40, as well as silica gel and amorphous aluminosilicates. The plots of differential heats against coverage served to construct
the acidity spectra and, in this way, to determine the number of acid sites with different acidity strengths. The behavior
of these materials in acid-catalyzed reactions, primarily, in the transformations of hydrocarbons is discussed. Evidence is
presented that heats of adsorption of ammonia can be used to obtain correlation plots that describe relations between acidic
and catalytic properties of zeolite catalysts. 相似文献
723.
Joachim Degen Hans -Herbert Schmidtke C. A. Chatzidimitriou-Dreismann 《Theoretical chemistry accounts》1985,67(1):37-42
A frequency-selective photon correlation experiment is carried out using the 10 K emission of microcrystalline Cs2TeBr6 as an example. The recording of dynamically inducedD-fluctuations allows to resolve the vibrational fine structure of an electronic transition which is not obtained by usual emission spectroscopy at this temperature. The experimental findings support the physical relevance of Prigogine's star-unitary transformations.Dedicated to Professor Dr. Hermann Hartmann on the occasion of his seventieth birthday 相似文献
724.
Howard Haubenstock 《Tetrahedron》2005,61(35):8358-8365
Density functional computations were carried out whose objectives were to quantify the interactions of chlorine and bromine with neighboring cationic centers in a series of 1-aryl-2-haloethyl cations. Analysis of structural changes and bonding interactions gave rise to linear correlations with σ+ values of the aryl substituents. Electron-donating groups diminished bridging and electron-withdrawing groups gave rise to stronger bridging. 相似文献
725.
The Dyson states as orbitals and geminals describing one- and two-electron detachment processes in molecules are treated within a spin-free formulation of the full configuration interaction (CI) theory. The ensuing computational scheme is presented and some semiempirical calculations on π-shells are given for unsaturated hydrocarbons such as medium-sized polyenes and aromatics. It is shown that in these systems the correlation effects turn out to be more important than the relaxation effects, leading to a marked reduction in the calculated full-CI photoionization crosss ections relative to the Hartree-Fock ones. 相似文献
726.
Mohamed El-Sayed Hardy Müller Gerd Rheinwald Heinrich Lang Stefan Spange 《Monatshefte für Chemie / Chemical Monthly》2003,134(3):361-370
Summary. N-(2′-Hydroxy-4′-N,N-dimethylaminobenzylidene)-4-nitroaniline [HDBN] has been used as a model for investigating intra- and intermolecular D–A (donor–acceptor) interactions in various environments
by means of UV/Vis spectroscopy. UV/Vis spectra of HDBN have been measured in various solvents, ethanolic solutions of different pH, adsorbed on silica, and in the solid state. A bathochromic shift of νmax is observed with increasing the dipolarity/polarizability and HBD (hydrogen bond donor) capacity of the solvent, which is
described by means of a multiple LSE (linear solvation energy) relationship in terms of the empirical Kamlet-Taft solvent polarity parameters. The adsorption of HDBN on Aerosil? 300-silica particles in non-HBA (hydrogen bond acceptor) solvents is explained in the same sense. Mobile protons and sol–gel
entrapping cause a hypsochromic shift due to protonation of the lone electron pair of the 4′-N,N-dimethylamino group. Hydroxide ions attack the 2′-hydroxy group which causes a bathochromic shift. A strong intramolecular
hydrogen bond between the 2′-hydroxyl hydrogen and the imine nitrogen atom is present in the solid-state structure causing
an unprecedented bathochromic shift.
Corresponding author. E-mail: stefan.spange@chemie.tu-chemnitz.de
Received July 8, 2002; accepted (revised) September 30, 2002 相似文献
727.
Roberto Markarian 《Journal of statistical physics》1995,80(5-6):1207-1239
We prove statistical properties of two-dimensional hyperbolic dynamical systems with singularities. Bunimovich, Sinai, and Chernov proved a theorem on the subexponential decay of correlations and a central limit theorem for billiard systems. In this paper we use their techniques to prove the same results for abstract systems. 相似文献
728.
We consider the density fluctuations of an ideal Brownian gas of particles performing Lévy flìghts characterized by the indexf. We find that the fluctuations scale as N(t) tH, where the Hurst exponentH locks onto the universal value 1/4 for Lévy flights with a finite root-mean-square range (f>2). For Lévy flights with a finite mean range but infinite root-mean-square range (1相似文献
729.
We study the approach to equilibrium of a classical gas. The initial condition corresponds to a Maxwell velocity distribution, but to a nonequilibrium binary correlation. We consider two cases. In the first, there are initially no spatial correlations, while in the second, initial correlations correspond to long-range spatial order. We show that the gas leaves the Maxwell velocity distribution function in the process of building up equilibrium correlations. The spatial correlations in the equilibrium state are seen to emerge from a self-organization process in the gas. Non-Markovian effects play an essential role in this process by coupling the velocity distribution and the binary correlations. For the case of initial long-range correlations we obtain anti-Boltzmann behavior in the evolution of the velocity distribution as the Boltzmann entropy decreases from the nonequilibrium to the equilibrium state. For this case we also have nontrivial behavior on a short time scale due to the non-Markovian effects. The approach used here is based on the theory of subdynamics as developed in previous publications. The results obtained show the interplay between irreversible processes leading to disorder and to order in a classical gas. 相似文献
730.
We investigate the zero-temperature quantum phase transition of the randombond Ising chain in a transverse magnetic field. Its critical properties are identical to those of the McCoy-Wu model, which is a classical Ising model in two dimensions with layered disorder. The latter is studied via Monte Carlo simulations and transfer matrix calculations and the critical exponents are determined with a finite-size scaling analysis. The magnetization and susceptibility obey conventional rather than activated scaling. We observe that the order parameter and correlation function probability distribution show a nontrivial scaling near the critical point, which implies a hierarchy of critical exponents associated with the critical behavior of the generalized correlation lengths. 相似文献