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71.
Oskar Nuyken Gerhard Maier Michael Leitner Dazhong Yang Martin Wolf 《Macromolecular Symposia》1995,98(1):269-283
Cationic polymerisation of 1, 4-diisopropenyl benzene, 1, 4-(2-chloro-isopropyl)benzene and related compounds yields soluble polymers with repeating units of indan. High performance polymers with indan units are available via nucleophilic substitution of halogenated aromatic monomers containing a central indan element, which are synthesized from 1, 1, 3-trimethyl-3-phenylindan via Friedel-Crafts-reaction with corresponding halogenated acyl- and sulfonyl chlorides. 相似文献
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75.
I. G. Klimov U. N. Kondratiev A. V. Vlasov E. O. Koval’ E. A. Maier 《Russian Journal of Applied Chemistry》2010,83(6):1109-1114
The comparative analysis of the molecular mass distribution, temperatures and heat effect of phase transitions, degree of
crystallinity of defect materials and matrix polyethylene film were carried out. Possible reasons of deterioration of the
quality of polyethylene on stages of its synthesis, transportation, storage, and processing were determined. 相似文献
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Scatter observed in the fatigue response of a nickel-based superalloy, U720, is linked to the variability in the microstructure. Our approach is to model the energy of a persistent slip band (PSB) structure and use its stability with respect to dislocation motion as our failure criterion for fatigue crack initiation. The components that contribute to the energy of the PSB are identified, namely, the stress field resulting from the applied external forces, dislocation pile-ups, and work-hardening of the material is calculated at the continuum scale. Further, energies for dislocations creating slip in the matrix/precipitates, interacting with the GBs, and nucleating/agglomerating within the PSB are computed via molecular dynamics simulations. Through this methodology, fatigue life is predicted based on the energy of the PSB, which inherently accounts for the microstructure of the material. The present approach circumvents the introduction of uncertainty principles in material properties. It builds a framework based on mechanics of microstructure, and from this framework, we construct simulated microstructures based on the measured distributions of grain size, orientation, neighbor information, and grain boundary character, which allows us to calculate fatigue scatter using a deterministic approach. The uniqueness of the approach is that it avoids the large number of parameters prevalent in previous fatigue models. The predicted lives are in excellent agreement with the experimental data validating the model capabilities. 相似文献
78.
Several Diels-Alder adducts between benzoquinones and cyclopentadiene were reduced to the corresponding diols 7a-c and 11. Treatment of these diols with strong acid triggered a skeletal rearrangement reaction resulting in compounds 8a-c and 12 that contain a 4,8-methanoazulene substructure. In addition, a dyotropic-like rearrangement of the tetracyclic lactone 13 to the spiro-lactone 18 was observed. Five of the structures were supported by X-ray analysis. 相似文献
79.
We study the two-dimensional Hubbard model with nonmagnetic Zn impurities modeled by binary diagonal disorder using quantum Monte Carlo within the dynamical cluster approximation. With increasing Zn content we find a strong suppression of d-wave superconductivity and an enhancement of antiferromagnetic spin correlations. T(c) vanishes linearly with Zn impurity concentration. The spin susceptibility changes from pseudogap to Curie-Weiss-like behavior indicating the existence of free magnetic moments in the Zn doped system. We interpret these results within the resonating-valence-bond picture. 相似文献
80.
Zang L Macyk W Lange C Maier WF Antonius C Meissner D Kisch H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(2):379-384
Amorphous microporous metal oxides of titanium (AMM-Ti) modified with chlorides of PtIV, IrIV, RhIII, AuIII, PdII, CoII, and NiII have been prepared by the sol-gel method and characterized by various surface analytical methods. These hybrid AMM-Ti powders are catalysts for the photodegradation of 4-chlorophenol (4-CP) in aqueous solution when illuminated with visible (lambda > or = 400 or 455 nm) or UV (lambda > or = 335 nm) light. The initial rate depends on the dopant level and is highest at 3.0% Pt in the case of PtIV/AMM-Ti. When employed in a photoelectrochemical cell, the activity spectrum of the photocurrent extends downward to about 600 nm, as does the photodegradation of 4-CP. It is suggested that the metal salt acts as a redox-active chromophore, transmitting the photogenerated charges to the amorphous matrix. 相似文献