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91.
H. Schwenk K. Neumaier K. Andres F. Wudl E. Aharon-Shalom 《Molecular Crystals and Liquid Crystals》2013,570(1):633-638
Both the Meissner-signal (flux expulsion on cooling through Tc) and the shielding signal (obtained by turning on a field in the superconducting state) have been observed in deuterated single crystals for fields oriented both along and normal to the chain axis. A possible isotope effect on Tc is discussed. We find complete diamagnetism in normal fields and incomplete (~ 40 %) diamagnetism in parallel fields. A dramatic drop of the Meissner-effect in parallel fields well below Hc1 is observed and not yet well explained. 相似文献
92.
Wagner J Andres H Rohrbach S Wagner D Oberer L France J 《The Journal of organic chemistry》2005,70(23):9588-9590
[Reaction: see text]. Sanglifehrin A is a novel complex natural product showing strong immunosuppressive activity and remarkably high affinity for cyclophilin A. To assess its pharmacokinetic properties in vivo, an efficient synthetic route was developed to introduce a tritium label in position C35 of sangliferin A via an oxidation/reduction strategy. The synthetic approach is particularly attractive, because the C35-oxo intermediate 7 is available in good yield on large scale and the reducing agent, lithium tri-sec-butylborotritide, is readily available. An attempt to apply a similar strategy to the alcohol in position C31 led primarily to C31-epi-hydroxy sanglifehrin A under a variety of conditions. 相似文献
93.
94.
95.
Jan Andres 《Proceedings of the American Mathematical Society》2008,136(4):1385-1395
We formulate an abstract scheme for the randomization of Shar- kovskii-type theorems via transformation to the deterministic case. In particular, Sharkovskii-type theorems for scalar differential equations can be randomized in this way. A random version of the standard Sharkovskii theorem is presented explicitly. Many remarks, comments and illustrating examples are supplied.
96.
97.
Hanspeter Kraft 《Commentarii Mathematici Helvetici》1970,45(1):110-118
Ohne Zusammenfassung 相似文献
98.
Summary We study closures of conjugacy classes in the Lie algebras of the orthogonal and symplectic groups and determine which ones
are normal varieties. Furthermore we give a complete classification of the minimal singularities which arise in this context,
i.e. the singularities which occur in the open classes in the boundary of a given conjugacy class. In contrast to the results
for the general linear group ([KP1], [KP2]) there are classes with non normal closure; they are branched in a class of codimension
two and give rise to normal minimal singularities. The methods used are (classical) invariant theory and algebraic geometry.
Supported in part by the SFB Theoretische Mathematik, University of Bonn, and by the University of Hamburg 相似文献
99.
We present a novel approach to calculating Low-Energy Electron Diffraction (LEED) intensities for ordered molecular adsorbates. First, the intra-molecular multiple scattering is computed to obtain a non-diagonal molecular T-matrix. This is then used to represent the entire molecule as a single scattering object in a conventional LEED calculation, where the Layer Doubling technique is applied to assemble the different layers, including the molecular ones. A detailed comparison with conventional layer-type LEED calculations is provided to ascertain the accuracy of this scheme of calculation. Advantages of this scheme for problems involving ordered arrays of molecules adsorbed on surfaces are discussed. 相似文献
100.
Hans Fritz Paul Hug Hanspeter Sauter Tammo Winkler Sven-Olov Lawesson Bjarne Skindhoj Pedersen Sten Scheibye 《Magnetic resonance in chemistry : MRC》1981,16(1):36-43
N,N-diisopropylamides and -thioamides show hindered rotation around the N? CH bonds, and the presence of mixtures of conformational isomers can be demonstrated at temperatures below 273 K in solution. 1H and 13C NMR spectra of these conformers are measured and assigned. The 13C data serve to study through-space effects on 13C chemical shifts, which strongly depend on the conformations of the isopropyl groups. For amides, a through-space shielding of the N-methine carbons is found to exist only for conformers in which the methine hydrogen atom is spatially close to the oxygen atom. Chemical shift differences between amides and thioamides can be rationalized in terms of through-bond and through-space contributions, and serve for a better understanding of the shift differences in N,N-dialkylamides and -thioamides. 相似文献