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101.
In a vibrational analysis of allyl compounds, which was made difficult because of autoassociation and conformational equilibrium, we have used the matr 相似文献
102.
Dr. Zhiyu Zou Dr. Alessandro Sala Dr. Mirco Panighel Dr. Ezequiel Tosi Dr. Paolo Lacovig Dr. Silvano Lizzit Dr. Mattia Scardamaglia Dr. Esko Kokkonen Dr. Cinzia Cepek Dr. Cristina Africh Prof. Giovanni Comelli Prof. Dr. Sebastian Günther Prof. Dr. Laerte L. Patera 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2023,135(1):e202213295
The synthesis of high-value fuels and plastics starting from small hydrocarbon molecules plays a central role in the current transition towards renewable energy. However, the detailed mechanisms driving the growth of hydrocarbon chains remain to a large extent unknown. Here we investigated the formation of hydrocarbon chains resulting from acetylene polymerization on a Ni(111) model catalyst surface. Exploiting X-ray photoelectron spectroscopy up to near-ambient pressures, the intermediate species and reaction products have been identified. Complementary in situ scanning tunneling microscopy observations shed light onto the C−C coupling mechanism. While the step edges of the metal catalyst are commonly assumed to be the active sites for the C−C coupling, we showed that the polymerization occurs instead on the flat terraces of the metallic surface. 相似文献
103.
Dr. Mattia Forchetta Valerio Baia Dr. Federica Sabuzi Prof. Valeria Conte Prof. Pierluca Galloni 《European journal of organic chemistry》2023,26(35):e202300523
Evaluation of quinacridone (QA) derivatives as homogeneous metal-free photocatalysts is here presented. QA derivatives were synthetized and systematically characterized, measuring their ground state and excited state redox potentials in dichloromethane (DCM) and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), in order to understand how structural modifications influenced their photocatalytic properties. In particular, the effect of dicyanomethylene and nitro EWG groups was investigated, in order to develop a photocatalyst capable of promoting oxidative processes in the presence of molecular oxygen. Among the analyzed derivatives, 2,9-dinitro-N,N′-dibutylquinacridone (DNDBQA) was the one with the highest excited state reduction potential (Ered*=1.60 V in HFIP vs SCE), while N,N’-dibutylquinacridone (DBQA) showed valuable excited state redox potentials (Ered*=1.29 V; Eox*=−1.28 V in HFIP vs SCE), making it suitable for bimodal applications in oxidative and reductive photocatalytic processes. Afterwards, the synthetized QA derivatives were examined as photocatalysts to promote the selective aerobic oxidation of thioether to sulfoxide. Promising results in thioanisole oxidation were achieved with all the QA derivatives tested as photocatalysts, in terms of yield and selectivity. Remarkably, DBQA showed the best performances, catalyzing the reaction in only 20 minutes, using 0.5 % of the photocatalyst, and showing excellent performances in the oxidation of several thioether derivatives. 相似文献
104.
Bitupon Borthakur Bernard Silvi Rian D. Dewhurst Ashwini K. Phukan 《Journal of computational chemistry》2016,37(16):1484-1490
Theoretical investigations predict that the singlet states of ylide‐substituted remote carbenes are significantly stable and comparable to those of experimentally known NHCs. They are also found to be strongly σ‐donating in nature as evident from an evaluation of the carbonyl stretching frequencies (νCO) of their complexes with the [Rh(CO)2Cl] fragment. NICS and QTAIM based bond magnetizability calculations indicate the presence of cyclic electron delocalization in majority of the molecules. © 2016 Wiley Periodicals, Inc. 相似文献
105.
106.
Saha S Flood AH Stoddart JF Impellizzeri S Silvi S Venturi M Credi A 《Journal of the American Chemical Society》2007,129(40):12159-12171
A multicomponent [2]rotaxane designed to operate as a molecular shuttle driven by light energy has been constructed, and its properties have been investigated. The system is composed of (1) a light-fueled power station, capable of using the photon energy to create a charge-separated state, and (2) a mechanical switch, capable of utilizing such a photochemically generated driving force to bring about controllable molecular shuttling motions. The light-fueled power station is, in turn, a dyad comprising (i) a pi-electron-accepting fullerene (C60) component and (ii) a light-harvesting porphyrin (P) unit which acts as an electron donor in the excited state. The mechanical switch is a redox-active bistable [2]rotaxane moiety that consists of (i) a tetrathiafulvalene (TTF) unit as an efficient pi-electron-donor station, (ii) a dioxynaphthalene (DNP) unit as a second pi-electron-rich station, and (iii) a tetracationic cyclobis(paraquat-p-phenylene) (CBPQT4+) pi-electron-acceptor cyclophane, which encapsulates the better pi-electron-donating TTF station. Diethylene glycol spacers were conveniently introduced between the electroactive components in the dumbbell-shaped thread to facilitate the template-directed synthesis of the [2]rotaxane. A modular synthetic approach was undertaken for the overall synthesis of this multicomponent bistable [2]rotaxane, beginning with the syntheses of the P-C60 dyad unit and the two-station TTF-DNP-based [2]rotaxane separately, using conventional synthetic methodologies. These two components were finally stitched together by an esterification to afford the target rotaxane. Its structure was characterized by 1H NMR spectroscopy and mass spectrometry as well as by UV-vis-NIR absorption spectroscopy and voltammetry. The observations reflect remarkable electronic interactions between the various units, pointing to the existence of folded conformations in solution. The redox-driven shuttling process of the CBPQT4+ ring between the two competitive electron-rich recognition units, namely, TTF and DNP, was investigated by electrochemistry and spectroelectrochemistry as a means to verify its operational behavior prior to the photophysical studies related to light-driven operation. The oxidation process of the TTF unit is dramatically hampered in the rotaxane, thereby reducing the efficiency of the shuttling motion. These results confirm that, as the structural complexity increases, the overall function of the system no longer depends simply on its "primary" structure but also on higher-level effects which are reminiscent of the secondary and tertiary structures of biomolecules. 相似文献
107.
This work describes studies of the electron-promoted Cope cyclization of 2,5-phenyl-1,5-hexadiene radical anions in a flowing afterglow triple quadrupole mass spectrometer. The electronic properties of the hexadienes have been systematically modified by using aromatic substituents at the 2- and 5-positions of the hexedienes, including those with nitro, trifluoromethyl, fluoro, chloro, and acetyl groups. Ions were formed by the thermal attachment of electrons in the gas phase. Structures of the molecular radical anions were probed to determine whether they undergo cyclization to a cyclohexane-1,4-diyl anion structure by examining chemical reactivity with neutral reagents including carbon dioxide, carbon disulfide, and nitric oxide. First-order rate constants for the reactions of ions were measured, and the reaction efficiencies were determined. Based on the reactivity results, a thermochemical model has been developed, which predicts the reaction thermochemistry by using thermochemical properties of model systems. The observed reactivity from ion-molecule reactions and the study of reaction rates show that the ion of 2,5-dicyanohexadiene and 2,5-di(4,4'-trifluoromethyl phenyl)-1,5-hexadiene undergo Cope cyclization, whereas the radical anions having substituents such as the fluoro, nitro, chloro, and acetyl groups do not. 相似文献
108.
Benedetta Morini Valeria Simoncini Mattia Tani 《Computational Optimization and Applications》2017,66(1):1-37
This paper addresses the solution of a cardinality Boolean quadratic programming problem using three different approaches. The first transforms the original problem into six mixed-integer linear programming (MILP) formulations. The second approach takes one of the MILP formulations and relies on the specific features of an MILP solver, namely using starting incumbents, polishing, and callbacks. The last involves the direct solution of the original problem by solvers that can accomodate the nonlinear combinatorial problem. Particular emphasis is placed on the definition of the MILP reformulations and their comparison with the other approaches. The results indicate that the data of the problem has a strong influence on the performance of the different approaches, and that there are clear-cut approaches that are better for some instances of the data. A detailed analysis of the results is made to identify the most effective approaches for specific instances of the data. 相似文献
109.
Bisio A Pagano B Romussi A Bruno O De Tommasi N Romussi G Mattia CA 《Molecules (Basel, Switzerland)》2007,12(10):2279-2287
The relative stereochemistry of 3,4-secoisopimara-4(18),7,15-triene-3-oic acid, a diterpenoid with antispasmodic, hypotensive and antibacterial activities isolated from Salvia cinnabarina, was determined by an X-ray diffraction analysis of a single crystal of a suitable crystalline derivative. 相似文献
110.
The HIV-1 nucleocapsid protein (NCp7) is an emerging target for antiretroviral therapy. Five hits have been reported to inhibit the NCp7-viral nucleic acids interaction at micromolar concentrations. We used two computationally refined structures of NCp7 as receptors to propose a reliable binding pose for these compounds, by means of computational methods. Theoretical binding modes are in agreement with available experimental data. Results lay the foundations for a rationale development of more effective NCp7 inhibitors. 相似文献