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111.
Marco Alpegiani Angelo Bedeschi Ettore Perrone Giovanni Franceschi 《Tetrahedron letters》1984,25(37):4171-4174
A straightforward conversion of penam methyl esters into penem acetonyl esters entailing incorporation of all the elements of the former into the latter is described. 相似文献
112.
113.
Ana Maria Rocco Daniel Perrone Moreira Robson Pacheco Pereira 《European Polymer Journal》2003,39(9):1925-1934
Blends of poly(ethylene oxide) (PEO) of high molecular weight with poly(bisphenol A-co-epichlorohydrin) (PBE) with high epoxy equivalent were studied spectroscopically, thermally and morphologically. As similar systems of low molecular weight, a single Tg was observed for all blends, indicating miscibility. A progressive decrease in the degree of crystallinity and in the size of the PEO spherulites as the PBE is added is also observed. Quantitative analysis from FTIR spectra provided determination of specific interactions between the constituents and their variation with PEO content. Simulations were performed utilising the spectra of the pure polymers to confirm that the observed changes in the experimental spectra of the blends were due to interaction between the polymers. 相似文献
114.
Pierluigi Nordio Maria V. Pavan Giovanni Giacometti 《Theoretical chemistry accounts》1963,1(4):302-307
Hyperconjugated models are used for a m.o. calculation of proton h.f.s. constants in Ethyl and Cyclohexadienyl radicals. A slightly modified Pariser-Parr-Pople SCF method is employed including extensive configuration interaction. The calculated spin densities for the hyperconjugated protons are in good agreement with experiment.
We thank the Italian National Research Council (Chemistry Committee, Research Group IV) for financial support. One of us (P.L.N.) thanks Sicedison S.p.A. for a grant. 相似文献
Zusammenfassung Zur Berechnung von Protonenhyperfeinstrukturkonstanten von Äthyl- und Cyclohexadienyl-Radikalen werden Modelle mit Hyperkonjugation verwendet. Die Rechnung gründet sich auf eine leicht modifizierte Pariser-Parr-Pople-Methode einschließlich ausgedehnter Konfigurationswechselwirkung. Die berechneten Spin-Dichten für die hyperkonjugierten Protonen stimmen mit experimentell ermittelten Werten gut überein.
Résumé Des modèles tenant compte à la hyperconjugaison sont usés pour le calcul des constantes de structure hyperfine protonique des radicaux éthyl et Cyclohexadiényl. Le calcul se base sur une méthode Pariser-Parr-Pople un peu modifiée et comprenant une interaction de configurations extensive. Les densités de spin calculées pour les protons hyperconjugués sont en bon accord avec des valeurs expérimentales.
We thank the Italian National Research Council (Chemistry Committee, Research Group IV) for financial support. One of us (P.L.N.) thanks Sicedison S.p.A. for a grant. 相似文献
115.
Polese Pierluigi Tolazzi Marilena Melchior Andrea 《Journal of Thermal Analysis and Calorimetry》2018,132(2):1317-1323
Journal of Thermal Analysis and Calorimetry - The pyrolysis characteristics and kinetics of lignocellulosic biomass (cotton stalk) and seaweed (Gracilaria lemaneiformis) were studied comparatively.... 相似文献
116.
Guido Viscardi Piero Savarino Pierluigi Quagliotto Ermanno Barni Mauro Botta 《Journal of heterocyclic chemistry》1996,33(4):1195-1200
Heterocyclic azodyes of the pyridylazonaphthol and pyridylazoresorcinol series containing tuned hydrophobic chains have been prepared. Due to their chelating properties, the dyes are suitable candidates for preconcentration and selective separation of transition metal ions. After a discussion on the choice of the best synthetic pathway, physical and spectral uv/visible properties are presented and correlated with the structural features. A detailed analysis of nmr spectra allowed the clarification of currently unresolved signal assignments. 相似文献
117.
Pierluigi Barbieri Gianpiero Adami Andrea Favretto E. Reisenhofer 《Fresenius' Journal of Analytical Chemistry》1998,361(4):349-352
Within research on the quality of the waters of the Gulf of Trieste, this study on patterns of trace metal contents in the
inner part of the gulf (Muggia Bay) discusses data of Cu, Pb, Cd and Zn, determined voltammetrically (DPASV), and collected
in three sites with a 10-day frequency over the period of one year. Two of the sites lie inside the dam system which protects
the harbour of Trieste, while the third one is situated outside for comparison purposes. Principal component analysis pointed
out different metal patterns inside and outside the dam system; PC scores were related to meteorological information: rain
plays a major role in conditioning the estuarine inner site: wind stirring action was detectable for the outer site. Both
univariate graphics and canonical correlation analysis suggest a diffuse source for Pb, probably atmospheric deposition.
Received: 1 August 1997 / Revised: 20 November 1997 / Accepted: 23 November 1997 相似文献
118.
Beringhelli T D'Alfonso G Panigati M Mercandelli P Sironi A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(23):5340-5350
The quantitative addition of pyrazole (Hpz) to the 44 valence-electron, triangular cluster anion [Re3(mu 3-H)-(mu-H)3(CO)9]- gives the novel unsaturated anion [Re3(mu-H)4(CO)9(Hpz)]- (1, 46 valence electrons), which contains a pyrazole molecule that is terminally coordinated on a cluster vertex. Solidstate X-ray and IR analyses reveal a rather weak hydrogen-bonding interaction between the NH proton and one of the hydrides bridging the opposite triangular cluster edge (delta H degree = -3.1 kcal mol-1 from the Iogansen equation). Both IR and NMR data indicate that such a proton-hydride interaction is maintained in the major conformer present in CD2Cl2, but also provide evidence of the presence of minor conformers of 1 in which the NH proton is involved in an intermolecular hydrogen bond with the solvent. The mu-H...HN bond length evaluated in solution through the T1 minimum value (2.07 A) and that determined in the solid state by X-ray diffraction (2.05 A) are in good agreement. NMR experiments show that, in acetone, intermolecular N-H...solvent interactions replace the intramolecular dihydrogen bond. At room temperature in CH2Cl2, the pyrazole ligand in 1 is labile and 1 slowly "disproportionates" to [Re3(mu 3-H)-(mu-H)3(CO)9]- and [Re3(mu-H)3(CO)9-(mu-eta 2-pz)(Hpz)]-, with H2 evolution. Slow H2 evolution also leads to the formation of the anion [Re3(mu-H)3-(CO)9(pz)]- (5), in which the pyrazolate anion adopts a novel mu 3-eta 2-coordination mode, as revealed by a single-crystal X-ray analysis. The analysis of the bond lengths indicates that the pyrazolate anion in 5 acts as a six-electron donor, with loss of the aromaticity. The formation of 5 from 1 is much faster in solvents with a high dielectric constant, such as acetone or DMF. Anion 5 was also obtained from the reaction of pyrazole with [Re3(mu-H)3(CO)9(mu 3-CH3)]- through the intermediate formation of two isomeric addition derivatives and following CH4 evolution. 相似文献
119.
Quagliotto P Viscardi G Barolo C Barni E Bellinvia S Fisicaro E Compari C 《The Journal of organic chemistry》2003,68(20):7651-7660
A new series of pyridinium cationic gemini surfactants was prepared by quaternization of the 2,2'-(alpha,omega-alkanediyl)bispyridines with N-alkylating agents, whose reactivity is briefly discussed. Particularly useful was the use of long-chain alkyl triflates (trifluoromethanesulfonates) for both overcoming the sterical hindrance in the pyridines and obtaining higher synthetic yields. Well-known 4,4'-(alpha,omega-alkanediyl)bis(1-alkylpyridinium) structures showed narrow temperature ranges for practical applications, due to their high Krafft points, while the new 2,2'-(alpha,omega-alkanediyl)bis(1-alkylpyridinium) series, accounted for good surface active properties. Due to the Krafft points below 0 degrees C, they could be exploited as solutions in water at any temperature. The characterization of the behavior of the series was performed by conductivity measurements. Some of the proposed structures exhibited unusual surface active behavior, which was interpreted in terms of particular conformational arrangements. 相似文献
120.
Giuliana Gervasio Domenica Marabello Claudia Barolo Pierluigi Quagliotto Guido Viscardi 《Journal of heterocyclic chemistry》2003,40(1):129-133
The X‐ray analyses of some neutral and cationic derivatives of 2‐(4‐methylpyridin‐2‐yl)‐1H‐benzimida‐zole are reported and the structural data tentatively correlated to relative UV‐visible properties. A rotation of the γ‐picoline ring with respect to the benzimidazole moiety may be responsible of the spectral behavior. 相似文献