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501.
[reaction: see text]. A new coupling procedure for the construction of the challenging beta-mannosidic bond is described. Dehydrative mannosylation using 4,6-O-benzylidene mannopyranoses allows for the formation of beta-mannosides in excellent yield. The stereoselectivity is generally good but influenced by the exact nature of the glycosylating agent and the nucleophile. 相似文献
502.
503.
Temperature‐Responsive Luminescent Solar Concentrators: Tuning Energy Transfer in a Liquid Crystalline Matrix
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Jeroen A. H. P. Sol Dr. Volker Dehm Reinhard Hecht Prof. Dr. Frank Würthner Prof. Dr. Albertus P. H. J. Schenning Dr. Michael G. Debije 《Angewandte Chemie (International ed. in English)》2018,57(4):1030-1033
Temperature‐responsive luminescent solar concentrators (LSCs) have been fabricated in which the Förster resonance energy transfer (FRET) between a donor–acceptor pair in a liquid crystalline solvent can be tuned. At room temperatures, the perylene bisimide (PBI) acceptor is aggregated and FRET is inactive; while after heating to a temperature above the isotropic phase of the liquid crystal solvent, the acceptor PBI completely dissolves and FRET is activated. This unusual temperature control over FRET was used to design a color‐tunable LSC. The device has been shown to be highly stable towards consecutive heating and cooling cycles, making it an appealing device for harvesting otherwise unused solar energy. 相似文献
504.
Exploiting the Synthetic Potential of Sesquiterpene Cyclases for Generating Unnatural Terpenoids
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Clara Oberhauser Vanessa Harms Dr. Katja Seidel Dr. Benjamin Schröder Kimia Ekramzadeh Dr. Sascha Beutel Sven Winkler Lukas Lauterbach Prof. Dr. Jeroen S. Dickschat Prof. Dr. Andreas Kirschning 《Angewandte Chemie (International ed. in English)》2018,57(36):11802-11806
The substrate flexibility of eight purified sesquiterpene cyclases was evaluated using six new heteroatom‐modified farnesyl pyrophosphates, and the formation of six new heteroatom‐modified macrocyclic and tricyclic sesquiterpenoids is described. GC‐O analysis revealed that tricyclic tetrahydrofuran exhibits an ethereal, peppery, and camphor‐like olfactoric scent. 相似文献
505.
Adduct-ion formation in trapped ion mobility spectrometry as a potential tool for studying molecular structures and conformations 总被引:1,自引:0,他引:1
Barbara M. Zietek Ynze Mengerink Jan Jordens Govert W. Somsen Jeroen Kool Maarten Honing 《International Journal for Ion Mobility Spectrometry》2018,21(1-2):19-32
Recent developments in the field of ion mobility spectrometry provide new possibilities to explore and understand gas-phase ion chemistry. In this study, hyphenated trapped ion mobility spectrometry-mass spectrometry (TIMS-MS) was applied to investigate analyte ion mobility as function of adduct ion formation for twelve pharmaceutically relevant molecules, and for tetrahydrocannabinol (THC) and its isomer cannabidiol (CBD). Samples were introduced by direct infusion and ions were generated with positive electrospray ionization (ESI+) observing protonated and sodiated ions. Measurements were performed with and without addition of cesium-, lithium-, silver- and sodium ions to the samples. For the tested compounds, metal adduct ions with the same m/z but with different mobility and collision cross section (CCSs) were observed, indicating different molecular conformations. Formation of analyte dimers was also observed, which could be associated with molecular geometry of the compounds. By optimizing the range and speed of the electric field gradient and ramp, respectively, the separation of THC and CBD was achieved by employing the adduct formation. This study demonstrates that the favorable resolution of TIMS combined with the ability to detect weakly bound counter ions is a valuable means for rapid detection, separation and structural assignment of molecular isomers and analyte conformations. 相似文献
506.
The Effect of the Active‐Site Structure on the Activity of Copper Mordenite in the Aerobic and Anaerobic Conversion of Methane into Methanol
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Dr. Vitaly L. Sushkevich Dr. Dennis Palagin Prof. Dr. Jeroen A. van Bokhoven 《Angewandte Chemie (International ed. in English)》2018,57(29):8906-8910
Samples of the zeolite mordenite with different Si/Al ratios were used to synthesize materials with monomeric and oligomeric copper sites that are active in the direct conversion of methane into methanol. A comparison of two reactivation protocols with oxygen (aerobic oxidation) and water (anaerobic oxidation), respectively, revealed that such copper–oxo species possess different reactivity towards methane and water. We show for the first time that oligomeric copper species exhibit high activity under both aerobic and anaerobic activation conditions, whereas monomeric copper sites produce methanol only in aerobic processes. 相似文献
507.
Dirks AJ van Berkel SS Hatzakis NS Opsteen JA van Delft FL Cornelissen JJ Rowan AE van Hest JC Rutjes FP Nolte RJ 《Chemical communications (Cambridge, England)》2005,(33):4172-4174
Biohybrid amphiphiles have been prepared from terminal azide functionalised polystyrene and an alkyne functionalised peptide or protein via a Cu(I) catalysed Huisgen [3 + 2] dipolar cycloaddition reaction. 相似文献
508.
Schenning AP V Herrikhuyzen J Jonkheijm P Chen Z Würthner F Meijer EW 《Journal of the American Chemical Society》2002,124(35):10252-10253
Well-defined chiral fibers incorporating hydrogen-bonded oligo(p-phenylene vinylene) donor and perylene bisimide acceptor chromophores have been realized by self-assembly. Upon photoillumination of these fibers electron-transfer takes place, leading to charge separation within the aggregated dyes. 相似文献
509.
Saudan C Ceroni P Vicinelli V Maestri M Balzani V Gorka M Lee SK van Heyst J Vögtle F 《Dalton transactions (Cambridge, England : 2003)》2004,(10):1597-1600
We have investigated the complexation of lanthanide ions (Nd3+, Eu3+, Gd3+, Tb3+, Dy3+) with three cyclam-based ligands (cyclam = 1,4,8,11-tetraazacyclotetradecane), namely 1,4,8,11-tetrakis(naphthylmethyl)cyclam (1), and two dendrimers consisting of a cyclam core appended with four dimethoxybenzene and eight naphthyl units (2) and twelve dimethoxybenzene and sixteen naphthyl units (3). In the free ligands the fluorescence of the naphthyl units is strongly quenched by exciplex formation with the cyclam nitrogens. Complexation with the metal ions prevents exciplex formation and revives the intense naphthyl fluorescence. Fluorescence and NMR titration experiments have revealed the formation of complexes with different metal/ligand stoichiometries in the case of 1, 2 and 3. Surprisingly, the large dendrimer 3 gives rise to a stable [M(3)3]3+ species. Energy transfer from the lowest singlet and triplet excited states of the peripheral naphthyl units to the lower lying excited states of Nd3+, Eu3+, Tb3+, Dy3+ coordinated to the cyclam core does not take place. 相似文献
510.
Chiral phosphoramidites have been identified as excellent ligands for various metal-catalyzed enantioselective transformations. Taking advantage of their easy preparation and modular nature, we designed a fully automated protocol for the parallel preparation of a library of 32 phosphoramidites and its screening in asymmetric hydrogenation of amino acid precursors. This initial study led to the discovery of a new ligand for the preparation of an enantiopure beta(3)-homoalanine precursor. [structure--see text] 相似文献