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41.
Odobel F Suresh S Blart E Nicolas Y Quintard JP Janvier P Le Questel JY Illien B Rondeau D Richomme P Häupl T Wallin S Hammarström L 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(13):3027-3046
A set of twelve porphyrin dimers has been prepared to give information on how the type of connectivity between a porphyrin core and a bridge can influence the interporphyrin electronic interaction. The new porphyrin systems are substituted directly at the meso position with an oligothiophene chain tethered either with a single C-C sigma bond, a trans ethylenyl group, or a acetylenyl group. The compounds are easily obtained by palladium-catalyzed cross-coupling reactions (Stille, Heck, and Sonogashira) between 5-iodo-10,15,20-(3,5-ditert-butylphenyl)porphyrin and the appropriate oligothiophene derivative. This synthetic approach is straightforward and very effective for preparing oligothiophene-based prophyrin systems. The absorption spectra and the fluorescence properties of the dimers demonstrated the crucial importance of the characteristics of the chemical bond used to connect the bridge to the porphyrin unit. The magnitude of the electronic communication can thus be significantly modulated by altering the type of bond connectivity used to link the chromophore to the bridge. The present work shows that an oligothiophene spacer is a viable class of linker for connecting porphyrins, and that a quaterthiophene appended with ethynyl linkages affords a high electronic interaction over a distance as large as 28 A. A detailed computational study of these dimers has clarified the conditions needed for a conjugated system to behave as a molecular wire. These conditions are full planarity of the molecule and proper energy matching between the frontier orbitals of the bridge and the porphyrin. Intermolecular energy transfer in asymmetrical dyads composed of a zinc porphyrin and a freebase porphyrin has been studied by fluorescence spectroscopy. In all systems, this process is more than 98% efficient, and its rate constant decreases steadily in the order 4ZH > 1ZH > 3ZH approximately 2ZH. Thus, the largest rate (kEnT = 1.2 x 10(11) s-1) was found in the dyad linked with bisethynyl quaterthiophene, which represents the longest bridge within the series. These results clearly demonstrate that strong communication and also efficient photoinduced processes can be promoted over a large distance if the electronic structure of the molecular connector is appropriately chosen. 相似文献
42.
Gunter Karig Andreas Fuchs Arne Büsing Tilmann Brandstetter Stefan Scherer JanW. Bats Albert Eschenmoser Gerhard Quinkert 《Helvetica chimica acta》2000,83(6):1049-1078
Cyclic nucleo‐δ‐amino acids that constitute monomers of a conformationally constrained nucleo‐δ‐peptide base‐pairing system have been prepared. Their synthesis starts with an enantioselectively catalyzed chirogenic Diels‐Alder reaction, proceeds via a regioselective ε‐iodolactamization process, and ends with a regio‐ as well as diastereoselective introduction of nucleobases through SN2‐type opening of a transiently formed N‐acylaziridine ring. Extensive use of X‐ray crystal‐structure analysis has been made to support structure assignments. 相似文献
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Tilmann B. Walk Axel W. Trautwein Hartmut Richter Günther Jung 《Angewandte Chemie (International ed. in English)》1999,38(12):1763-1765
The direct determination of the elemental compositions of the components of compound collections from combinatorial chemistry is achieved by ESI-FT-ICR mass spectrometry. Coupling with HPLC opens up a new dimension in high-resolution, informative analysis. The improved resolution of ESI-FT-ICR mass spectrometry in comparison to quadrupole mass spectrometry in the measurement of a compound obtained by solid-phase synthesis is illustrated. 相似文献
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Stephan Denifl Dr. Fabio Zappa Dr. Ingo Mähr Filipe Ferreira da Silva Abid Aleem Andreas Mauracher Dr. Michael Probst Prof. Dr. Jan Urban Prof. Dr. Pavel Mach Prof. Dr. Arntraud Bacher Dr. Olof Echt Prof. Dr. Tilmann D. Märk Paul Scheier Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(47):8940-8943
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Tilmann Würfel 《Mathematische Zeitschrift》1980,172(1):81-88
Ohne Zusammenfassung 相似文献
50.
Stefan Barthel Kolja Schuh Oliver Marquardt Tilmann Hickel Jörg Neugebauer Frank Jahnke Gerd Czycholl 《The European Physical Journal B - Condensed Matter and Complex Systems》2013,86(11):1-11
In this paper we systematically analyze the electronic structures of polar and nonpolar wurtzite-InN/GaN quantum dots and their modification due to the quantum-confined Stark effect caused by intrinsic fields. This is achieved by combining continuum elasticity theory with an effective-bond orbital model to describe the elastic and single-particle electronic properties in these nitride systems. Based on these results, a many-body treatment is used to determine optical absorption spectra. The efficiency of optical transitions depends on the interplay between the Coulomb interaction and the quantum-confined Stark effect. We introduce an effective confinement potential which represents the electronic structure under the influence of the intrinsic polarization fields and calculate the needed strength of Coulomb interaction to diminish the separation of electrons and holes. 相似文献