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The reaction of α,β-unsaturated acylsilanes with allenylsilanes can be directed to produce either five or six-membered carbocyclic compounds. 相似文献
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C. Meier M. Volkmer J. Lieschke M. Fink N. Böwering 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1994,30(2):183-187
Relative elastic differential cross sections for scattering of 1 keV electrons from CF3H, CF4, CF3Cl, CH3F and CH3Cl molecules were measured for momentum transfer from 3 Å?1 to 29 Å?1. The oscillatory residuals remaining after substraction of the atomic scattering and the molecular interference contributions calculated in the independent atom model are ascribed to the influence of intramolecular multiple scattering. The data reflect the dominant contributions of the CF3-group and show larger oscillations than obtained from triple scattering calculations according to the method of Liu and Bonham using the second Born approximation. 相似文献
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William H. Fink 《International journal of quantum chemistry》1973,7(6):1045-1050
The general problem of the transfer of the representation of a set of orthonormal functions from one basis to a different, nonequivalent one is considered and specialized to a matrix formulation convenient for use in molecular electronic structure calculations. A procedure is suggested for treating problems where the transfer of representation breaks into a subset of most interest and one of less interest as for example the occupied and virtual orbitals of a Hartree-Fock SCF calculation. These techniques are then applied to obtain a representation of a methyl group from an SCF wave function for methane. 相似文献
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The relative energies of one-, two-, and three-dimensional Bravais lattice Lennard-Jones particles can be calculated by lattice sums. The expression of lattice sums over a Lennard-Jones potential can be manipulated into a form that converges rapidly. A formalism capable of calculating the lattice potential at arbitrary points of a completely general lattice has been developed. This method provides an alternative way to calculate the relative energies from the surface and the interior bulk sites of many chemical systems. The method is illustrated with application to hcp and fcc Lennard-Jonesium, both for the relative binding energy and for calculating the potential along the geometric diffusion pathway between tetrahedral and octahedral interstitial sites. Diffusion from the tetrahedral site to the octahedral site experiences a barrier of 752.600 in units of 4 epsilon. The reverse pathway experiences a barrier of 1035.614 in units of 4 epsilon. 相似文献
29.
Iron(II) complexes were synthesized with bisiminepyridine ligands of different steric demand. Activation with modified MAO
(25 mol% isobutyl groups) generated very active catalysts for propylene oligomerization. These oligomerizations were carried
out in liquid propylene in a heat flow calorimeter. The oligomers were separated by preparative gas chromatography and the
dimers and trimers analyzed using analytical gas chromatography, 1H-NMR-, and 13C NMR-spectroskopy. By means of the knowledge of the dimer and trimer structure, we were able to establish a mechanistic pathway
for propylene insertion and obtained knowledge about the iron alkyl species involved. Analysis of the various dimers formed
allowed us to determine the percentage of 1,2-versus 2,1-propylene insertions. Considering the same iron alkyl species with
ligands of different steric demand, a change in the probabilities for 1,2-versus 2,1-propylene insertions can be observed.
With this knowledge, the catalyst behaviour for ligands of varying steric demand can be predicted. The question of how to
produce oligomers versus polymers is one of knowing how to control the ratio of the 1.2-and 2.1-insertion. One method is to
alter the steric demand in the ortho position of the ligand. The more bulky the ligand, the more often a 2,1-propylene insertion
happens and, therefore, the higher the molecular mass of the oligomers, i.e., polymer is formed. Another important observation
is that the formation of α-olefines is favored with a higher steric demand of the catalyst.
The text was submitted by the authors in English. 相似文献
30.
Summary The paper concerns solution manifolds of nonlinear parameterdependent equations (1)F(u, )=y0 involving a Fredholm operatorF between (infinite-dimensional) Banach spacesX=Z× andY, and a finitedimensional parameter space . Differntial-geometric ideas are used to discuss the connection between augmented equations and certain onedimensional submanifolds produced by numerical path-tracing procedures. Then, for arbitrary (finite) dimension of , estimates of the error between the solution manifold of (1) and its discretizations are developed. These estimates are shown to be applicable to rather general nonlinear boundaryvalue problems for partial differential equations.This work was in part supported by the U.S. Air Force Office of Scientific Research under Grant 80-0176, the National Science Foundation under Grant MCS-78-05299, and the Office of Naval Research under Contract N-00014-80-C-0455 相似文献