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941.
Ab initio molecular orbital calculations with a double-ζ basis have been carrried out on five models of beryllocene, Cp2Be, with fixed geometries. The lowest energies are obtained for the π-Cp, σ-Cp and D5d models.
The He(I) photoelectron spectrum of Cp2Be was recorded and the ionization potentials of the first bands were compared with the orbital energies obtained from the molecular orbital calculations. A satisfactory fit between experiment and calculations was obtained for a slip sandwich model of Cs symmetry. A model of C5v symmetry is only compatible with the PE spectrum if the Jahn—Teller splitting of the lowest 2E1 state of the molecular ion is exceptionally large, 1.0 eV. 相似文献
942.
Model compounds have been used in studies at 60° in connection with transfer to polymer during the copolymerization of vinyl acetate with esters of fumaric acid. Succinate esters were used to simulate the fumarate ester units and ethyl acetate the vinyl acetate units in the copolymers. The succinate esters are much more reactive than ethyl acetate in transfer reactions with polyvinyl acetate radicals. Methyl isobutyrate and methyl propionate were also examined to assess the difference in reactivity in transfer of tertiary and secondary hydrogen atoms. It is concluded that branching is a very important reaction in the preparation of high conversion copolymers of fumarate esters with vinyl acetate. 相似文献
943.
N-methylaminoalkoxides of titanium of the type Ti(OR)4?n(O · CHR′ · CH2 · NR″R?)n where R = Et and Pr1; n = 1–4; and R′ = R″ = H, R? = Me; R′ = H, R″ = R? = Me; R′ = R″ = R? = Me, synthesized by the reactions of titanium alkoxides with aminoalcohols, show interesting variations in their properties like physical state, volatility and molecular complexity. I.r. and p.m.r. spectra of these derivatives have been recorded. A few interchange reactions with methanol and tert-butanol have also been carried out. These aminoalkoxides get cleaved with acetyl chloride and undergo insertion reactions with phenylisocyanate, thus providing the first examples of insertion reactions in such derivatives. 相似文献
944.
Professor J. R. Sabin R. E. Harris T. W. Archibald P. A. Kollman L. C. Allen 《Theoretical chemistry accounts》1970,18(3):235-238
Ab initio calculations are carried out on the planar hexamer model of anomalous water using a variety of basis sets. The results are compared to results of similar calculations on free water and water in the ice I-like puckered ring configurations.
Zusammenfassung Es werden ab initio-Rechnungen für das planare Hexamer-Modell von anomalem Wasser unter Verwendung mehrerer BasissÄtze durchgeführt. Die Ergebnisse werden mit Resultaten Ähnlicher Rechnungen über freies Wasser und Wasser in der I-Eis Ähnlichen Konfiguration verzerrter Ringe verglichen.
Résumé Calculs ab initio sur le modèle hexamérique plan de l'eau anormale en utilisant différentes bases. Les résultats sont comparés à ceux de calculs similaires sur l'eau libre et sur l'eau dans une configuration cyclique compacte analogue à celle de la glace I.相似文献
945.
The vertical ionization potentials of bis(-allyl)nickel (see (1) in Fig. 1) are calculated by means of the Green's function approach within a semiempirical INDO extension to the first transition metal series. The computed ionization potentials are in good agreement with an experimentally deduced assignment. In contrast to earlier theoretical and experimental studies, the 7a
u
() level is predicted on top of the levels corresponding to the Ni 3d orbitals. Our approach leads to a complete assignment of the PE spectrum of (1) in the outer valence region. 相似文献
946.
The major product from 2,3-naphthoquinodimethane formed by cyclisation of -dipropadienylbenzene was found to be the dimer 5 containing an eight-membered ring, for which the inversion barrier was determined by dynamic 1H NMR spectrometry, ΔG3 = 18 kcal/mole. 相似文献
947.
C. Chr. Heuck und G. Middelhoff 《Fresenius' Journal of Analytical Chemistry》1978,290(2):127-128
948.
F. Ruttens R. oedeweeck F. Lopez-Arbeloa F. C. De Schryver 《Photochemistry and photobiology》1985,42(4):341-346
Abstract— The synthesis, absorption and emission properties of erythro (e) and threo (t) Na-acetyl-1-pyrenylalanyl-1-methyltryptophan methylester (APTE) are reported. From the dependency of the exciplex emission maximum on the solvent polarity, the exciplex dipole moment of erythro and threo APTE were calculated. The evolution of the ratio of the quantum yield of exciplex emission and the quantum yield of emission from the locally excited state is correlated with solvent polarity and with the tendency of the solvent to interact with the peptide chain through hydrogen bonding. It is shown that solvents, inert towards the peptide function, shift the equilibrium between the two ground state conformations towards C7 , in which an exciplex geometry can be reached. Hydrogen accepting solvents shift the conformational equilibrium towards C5 , which cannot form an exciplex directly within the lifetime of excited pyrene. 相似文献
949.
950.
The photoelectron asymmetry parameter, β, is reported for individual vibrational levels of H2+(X2Σg+) formed by photoionization of H2(X1Σg+) at wavelengths of 736, 584, 461 and 304 Å. At 584 Å, β, exhibits a monotonic increase with vibrational quantum number (decreasing photoelectron kinetic energy) confirming the trend predicted by Itikawa. 相似文献