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931.
K. E. Uhrich D. R. Larrier C. T. Laurencin R. Langer 《Journal of polymer science. Part A, Polymer chemistry》1996,34(7):1261-1269
The in vitro degradation characteristics of poly(anhydride-imides) containing pyromellitylimidoalanine, with either 1,6-bis(carboxyphenoxy)hexane (CPH) or sebacic acid (SA) were assessed. The copolymers contained up to 50 mol % of the imide monomer, pyromellitylimidoalanine (PMA-ala). Degradation was pH sensitive, being enhanced under basic conditions. Control of degradation times from 2 days to 2 months was achieved by the selection of appropriate monomer units in the polymer backbone. Monomers were chosen based on their solubility in aqueous media, as well as how they influenced the hydrophobicity and crystallinity of the polymer matrices. Polymer degradation was followed by ultraviolet spectroscopy and high-pressure liquid chromatography. Increasing the amount of imide monomer, PMA-ala, and the use of SA (rather than CPH) as the comonomer increased the degradation rate of the polymer matrices. © 1996 John Wiley & Sons, Inc. 相似文献
932.
The crystal structure of Na3TaF8 is redetermined at 153 K and well determined bond distances and angles are provided. 相似文献
933.
Julian Kund Jan-Hendrik Kruse Andreas Gruber Dr. Ivan Trentin Marcel Langer Dr. Clarissa Read Dr. Gregor Neusser Dominik Blaimer Dr. Ulrich Rupp Prof. Dr. Carsten Streb Prof. Dr. Kerstin Leopold Prof. Dr. Felix H. Schacher Prof. Dr. Christine Kranz 《Angewandte Chemie (International ed. in English)》2023,62(22):e202217196
Heterogeneous light-driven catalysis is a cornerstone of sustainable energy conversion. Most catalytic studies focus on bulk analyses of the hydrogen and oxygen evolved, which impede the correlation of matrix heterogeneities, molecular features, and bulk reactivity. Here, we report studies of a heterogenized catalyst/photosensitizer system using a polyoxometalate water oxidation catalyst and a model, molecular photosensitizer that were co-immobilized within a nanoporous block copolymer membrane. Via operando scanning electrochemical microscopy (SECM), light-induced oxygen evolution was determined using sodium peroxodisulfate (Na2S2O8) as sacrificial electron acceptor. Ex situ element analyses provided spatially resolved information on the local concentration and distribution of the molecular components. Infrared attenuated total reflection (IR-ATR) studies of the modified membranes showed no degradation of the water oxidation catalyst under the reported light-driven conditions. 相似文献
934.
935.
Frederik Rummel Frerk Wehmeyer Dr. Matthias Vogt Prof. Dr. Robert Langer 《欧洲无机化学杂志》2023,26(28):e202300313
The thioether-group-containing SNS-type pincer complex [({EtSCH2CH2}2NH)RuCl(H)(PPh3)] ( 2 ) exists in three different diastereomers ( 2 a – c ). The molecular structures obtained from single crystal X-Ray diffraction studies of all three isomers reveal a difference in the relative orientation of the respective EtS-groups, while other commonly observed diastereomers as the result of cis-/trans- or fac-/mer-isomerism are not observed. Chemical exchange between the three diastereomers 2 a – c was discovered by phase-sensitive 1H and 31P NOESY NMR spectroscopy, and further quantified by line shape analysis of 1H NMR spectra. The experimentally derived averaged Gibbs energies of activation for the interconversion of the isomers (65–70 kJ/mol) are in good agreement with the results obtained from DFT calculations, which suggest an inversion of the ligating sulfur atoms, although a dissociative pathway for the configurational inversion can be competitive. 相似文献
936.
Christian Knüpfer Dr. Christian Färber Dr. Jens Langer Prof. Dr. Sjoerd Harder 《Angewandte Chemie (International ed. in English)》2023,62(18):e202219016
Alkenes that normally do not react with LiAlH4 (3-hexene, cyclohexene, 1-Me-cyclohexene), can be reduced to the corresponding alkanes by a mixture of LiAlH4 and Fe0 (the iron was activated by Metal-Vapour-Synthesis). This alkene-to-alkane conversion with a stoichiometric quantity of LiAlH4/Fe0 does not need quenching with water or acids, implying that both H's originate from LiAlH4. The LiAlH4/Fe0 combination is also a remarkably potent cooperative catalyst for hydrogenation of multi-substituted alkenes and benzene or toluene. An induction period of circa two hours and the minimally required temperature of 120 °C, suggests that the actual catalyst is a combination of Fe0 and the decomposition product of LiAlH4 (LiH and Al0). A thermally pre-activated LiAlH4/Fe0 catalyst did not need an induction time and is also active at room temperature and 1 bar H2. A combination of AliBu3 and Fe0 is an even more active hydrogenation catalyst. Without pre-activation, tetra-substituted alkenes like Me2C=CMe2 and toluene could be fully hydrogenated. 相似文献