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221.
The classical Jung theorem gives an optimal upper estimate for the radius of a bounded subset of R
n in terms of its diameter and the dimension. In this note we present an analogue of this result for metric spaces of curvature bounded above in the sense of Alexandrov. 相似文献
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224.
Urs Würgler 《Commentarii Mathematici Helvetici》1971,46(1):414-424
Ohne Zusammenfassung 相似文献
225.
226.
Strong and weak coupling expansions for the SU(2), mixed action lattice gauge theories are given. Nonperturbative configurations are identified and their contribution is also estimated. A comparison with Monte Carlo data is presented. 相似文献
227.
Hans Peter Hrter Heinz Lichti Urs Stauss Othmar Schindler 《Helvetica chimica acta》1976,59(4):1203-1212
Comparison of reaction products afforded by phenylguanidine derivatives with β-ketoesters or propiolic esters, respectively (synthesis of pyrimidones). 2-Anilino-imidazolines, when treated with either β-ketoesters or propiolic esters, yield two isomeric groups of pyrimidones. The isomerism is based on different positions of the carbonyl group in the pyrimidone ring. The mass spectra permit an unequivocal assignment of constitution I to the product formed with β-ketoesters and of constitution V to that formed with propiolic esters. Additionally, 2-(2-amino-anilino)-2-imidazoline (XII) when treated with methyl phenylpropiolate yields IX; while treatment with ethyl benzoylacetate yields XIII as an intermediate, which eliminates spontaneously one molecule of water to give the benzimidazole derivative XIV. Phenylguanidines (XV) add propiolic esters in the same way as do imidazoline derivatives. Photochemical cleavage of two carbon atoms with their adherent hydrogen atoms from the imidazole ring of the pyrimidones (V) leads to aminopyrimidine derivatives, e.g. XVI. 相似文献
228.
Felix Splinder György Bor Urs K. Dietler Piero Pino 《Journal of organometallic chemistry》1981,213(1):303-312
The formation of a new compound, the most characteristic IR absorption bands of which appear at 2007 cm-1 and 1956 cm-1, has been in the reaction between Co2(CO)8 and Rh4(CO)12 under carbon monoxide pressure in a hydrocarbon medium. The same compound is also formed either by the reaction of Co2(CO)8 with [Rh(CO)2Cl]2 or by the reaction of Co3Rh(CO)12 with carbon monoxide. The new complex has not been isolated in a pure state, but the formula CoRh(CO)7 is proposed on the basis of the stoichiometry of its formation and its physico-chemical properties. Equilibrium constants and thermo-dynamic parameters for the reaction 2 Co2(CO)8 + Rh4(CO)12 4 CoRh(CO)7 have been estimated. Possible structures for the new complex are discussed on the basis of its IR spectrum. 相似文献
229.
Graham Smith Urs D. Wermuth Jonathan M. White 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(3):o180-o183
The structures of the 1:1 proton‐transfer compounds of 4,5‐dichlorophthalic acid with 8‐hydroxyquinoline, 8‐aminoquinoline and quinoline‐2‐carboxylic acid (quinaldic acid), namely anhydrous 8‐hydroxyquinolinium 2‐carboxy‐4,5‐dichlorobenzoate, C9H8NO+·C8H3Cl2O4−, (I), 8‐aminoquinolinium 2‐carboxy‐4,5‐dichlorobenzoate, C9H9N2+·C8H3Cl2O4−, (II), and the adduct hydrate 2‐carboxyquinolinium 2‐carboxy‐4,5‐dichlorobenzoate quinolinium‐2‐carboxylate monohydrate, C10H8NO2+·C8H3Cl2O4−·C10H7NO2·H2O, (III), have been determined at 130 K. Compounds (I) and (II) are isomorphous and all three compounds have one‐dimensional hydrogen‐bonded chain structures, formed in (I) through O—H...Ocarboxyl extensions and in (II) through N+—H...Ocarboxyl extensions of cation–anion pairs. In (III), a hydrogen‐bonded cyclic R22(10) pseudo‐dimer unit comprising a protonated quinaldic acid cation and a zwitterionic quinaldic acid adduct molecule is found and is propagated through carboxylic acid O—H...Ocarboxyl and water O—H...Ocarboxyl interactions. In both (I) and (II), there are also cation–anion aromatic ring π–π associations. This work further illustrates the utility of both hydrogen phthalate anions and interactive‐group‐substituted quinoline cations in the formation of low‐dimensional hydrogen‐bonded structures. 相似文献
230.
A real Liouville domain is a Liouville domain with an exact anti-symplectic involution. The authors call a real Liouville domain uniruled if there exists an invariant finite energy plane through every real point. Asymptotically, an invariant finite energy plane converges to a symmetric periodic orbit. In this note, they work out a criterion which guarantees uniruledness for real Liouville domains. 相似文献