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51.
Gernot Eichmann 《Few-Body Systems》2016,57(7):541-547
We outline a microscopic framework to calculate nucleon Compton scattering from the level of quarks and gluons within the covariant Faddeev approach. We explain the connection with hadronic expansions of the Compton scattering amplitude and discuss the obstacles in maintaining electromagnetic gauge invariance. Finally we give preliminary results for the nucleon polarizabilities. 相似文献
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Gernot Neugebauer 《Journal of Geometry and Physics》2012,62(3):613-630
Based on the solution of a boundary problem for disconnected (Killing) horizons and the resulting violation of characteristic black hole properties, we present a non-existence proof for equilibrium configurations consisting of two aligned rotating black holes. Our discussion is principally aimed at developing the ideas of the proof and summarizing the results of two preceding papers (Neugebauer and Hennig, 2009 [2], Hennig and Neugebauer, 2011 [3]). From a mathematical point of view, this paper is a further example (Meinel et al., (2008) [29]) for the application of the inverse (“scattering”) method to a non-linear elliptic differential equation. 相似文献
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Dr. Xiaodan Chen Dr. Zhongshu Li Prof. Dr. Gernot Frenking Prof. Dr. Israel Fernández Prof. Lili Zhao Prof. Dr. Hansjörg Grützmacher 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(33):7912-7920
Phosphaheteroallenes R−P=C=L, with L = N-heterocyclic carbenes (NHCs), can be viewed to a certain extent as phosphaisonitriles stabilized with NHCs, R−P=C:←L. The suitability of these molecules as ligands for coinage-metal ions was investigated and coordination through the central carbon center was observed in most cases. A combination of experiments, spectroscopic methods, and DFT calculations indicates the presence of a hidden electron pair at the carbon center of R−P=C:←L. Remarkably, this lone pair also inserts intramolecularly in C−H bonds showing the carbene-type reactivity which is expected for phosphaisonitriles. 相似文献
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Polymer-coated cation exchangers in high-performance ion chromatography: preparation and application
Low-capacity cation-exchange stationary phases for ion chromatography were prepared by coating a vinyl-modified silica gel with polystyrene or poly(glycidyl methacrylate). Strong acid ion-exchange groups were formed by sulphonation with concentrated sulphuric acid or by ring opening of the polymer-coated silica gels with sulphite solution. Carbon-sulphur elemental analyses of the polymer-coated cation exchangers (PCCEs) were applied to determine the average polymer film thickness. The pH stability depended on the polymer film thickness. The PCCEs were stable in the pH range 0.5–9. The low-capacity PCCEs (capacities 18–91 μmol/g) were applied to determine alkali and alkaline earth metal ions in tap and mineral waters. 相似文献
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The nature of the chemical bonds in the diatomic molecules E2 (E=N–Bi, F–I), CO and BF has been studied with an energy partitioning analysis using gradient-corrected density functional theory calculations. The results make it possible to estimate quantitatively the strength of covalent and electrostatic attractions and the Pauli repulsion between the atoms. The data suggest that some traditional explanations regarding the strength of the molecules should be modified. The energy partitioning analysis shows that the chemical bonds in the group 15 diatomic molecules have significant electrostatic character, which increases from 30.1% in N2 to 58.3% in Bi2. The contribution of the electrostatic attraction to the binding interactions in Sb2 and Bi2 is larger than the covalent bonding. The strength of the bonding in the triply bonded dinitrogen is less than that of the bonding. The calculations indicate that E is between 32.2% (Bi2) and 40.0% (P2) of the total orbital interaction energy (Eorb). The much stronger bond of N2, as compared with the heavier group 15 E2 homologues, is not caused by a particularly strong contribution by the bonding, but rather by the relatively large interactions. The comparison of N2 with isoelectronic CO shows that the electrostatic character in the heteroatomic molecule is slightly smaller (28.8%) than in the homoatomic molecule. The contribution of the bonding in CO is larger (49.2%) than in N2 (34.3%). The reason why CO has a stronger bond than N2 is the significantly weaker Pauli repulsion in CO. The electrostatic character of the bonding in BF is slightly larger (32.0%) than in CO and N2. BF has much weaker -bonding contributions that provide only 11.2% of the covalent interactions, which is why BF has a much weaker bond than CO and N2. The chemical bonds in the dihalogen molecules have much higher covalent than electrostatic character. The Eorb term contributes between 74.4% (Br2) and 79.7% (F2) to the total attractive interactions. The relatively weak bond in F2 comes from the rather large Pauli repulsion.Contribution to the Jacopo Tomasi Honorary Issue 相似文献
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