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681.
A surface integral equation together with the multilevel fast multipole algorithm is successfully applied to fast and accurate resolution of plasmonic problems involving a large number of unknowns. The absorption, scattering, and extinction efficiencies of several plasmonic gold spheres of increasing size are efficiently obtained solving the electric and magnetic current combined-field integral equation. The numerical predictions are compared with reference analytic results to demonstrate the accuracy, suitability, and capabilities of this approach when dealing with large-scale plasmonic problems. 相似文献
682.
Jesús Antonio Luque-Urrutia Dr. Albert Poater Prof. Dr. Miquel Solà 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(4):804-808
From the analysis of the polarizability of carbon nano-onions (CNOs), it was concluded that CNOs behave as near perfect nanoscopic Faraday cages. If CNOs behave as ideal Faraday cages, the reactivity of the C240 cage should be the same in Li+@C240 and Li+@C60@C240. In this work, the Diels–Alder reaction of cyclopentadiene to the free C240 cage and the C60@C240 CNO together with their Li+-doped counterparts were analyzed using DFT. It was found that in all cases the preferred cycloaddition is on bond [6,6] of type B of C240. Encapsulation of Li+ results in lower enthalpy barriers due to the decrease of the energy of the LUMO orbital of the C240 cage. When the Li+ is placed inside the CNO C60@C240, the decrease in enthalpy barrier is similar to that of Li+@C240. However, the location of Li+ in Li+@C240 (off-centered) and Li+@C60@C240 (centered) is quite different. When Li+ was placed in the center of the C240 cage in Li+@C240, the barriers increased significantly. Taking into account this effect, the barriers in Li+@C240 and Li+@C60@C240 differ by about 4 kcal mol−1. This result can be attributed to the shielding effect of C60 in Li+@C60@C240. As a result, we conclude that this CNO does not act as a perfect Faraday cage. 相似文献
683.
Yajing Hu Albert Solé-Daura Dr. Yang-Rong Yao Xuechen Liu Dr. Sijie Liu Ao Yu Dr. Ping Peng Prof. Josep M. Poblet Dr. Antonio Rodríguez-Fortea Prof. Luis Echegoyen Prof. Fang-Fang Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(8):1748-1753
The chemistry of cationic forms of clusterfullerenes remain less explored than that of the corresponding neutral or anionic species. In the present work, M3N@Ih-C80 (M=Sc or Lu) cations were generated by both electrochemical and chemical oxidation methods. The as-obtained cations successfully underwent the typical Bingel–Hirsch reaction that fails with neutral Sc3N@Ih-C80. Two isomeric Sc3N@Ih-C80 cation derivatives, [5,6]-open and [6,6]-open adducts, were synthesized, and the former has never been prepared by means of a Bingel–Hirsch reaction with neutral clusterfullerenes. In the case of the Lu3N@Ih-C80 cation, however, only a [6,6]-open adduct was obtained. Density functional theory (DFT) calculations indicated that the oxidized M3N@Ih-C80 was much more reactive than the neutral compound upon addition of the diethyl bromomalonate anion. The Bingel–Hirsch reaction of M3N@Ih-C80 cations occurred by means of an unusual outer-sphere single-electron transfer (SET) process from the diethyl bromomalonate anion to the stable intermediate [M3N@C80(C2H5COO)2CBr].. Remarkably, the diethyl bromomalonate anion was found to act as both a nucleophile and an electron donor. 相似文献
684.
Prof. Dr. Daniel Solé Arianna Amenta Prof. Dr. M.-Lluïsa Bennasar Prof. Dr. Israel Fernández 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(43):10239-10245
A synthetic method to prepare tetrahydroquinoline-4-carboxylic acid esters has been developed through the transition-metal-catalyzed intramolecular aromatic C−H functionalization of α-diazoesters. Both [{Pd(IMes)(NQ)}2] (IMes=1,3-dimesitylimidazol-2-ylidene, NQ=1,4-naphthoquinone) and the first-generation Grubbs catalyst proved effective for this purpose. The ruthenium catalyst was found to be the most versatile, although in a few cases the palladium complex afforded better yields or selectivities. According to DFT calculations, Pd0- and RuII-catalyzed sp2-CAr−H functionalization proceeds through different reaction mechanisms. Thus, the Pd0-catalyzed reaction involves a Pd-mediated 1,6-H migration from the sp2-CAr−H bond to the carbene carbon atom, followed by a reductive elimination process. In contrast, electrophilic addition of the ruthenacarbene intermediate to the aromatic ring and subsequent 1,2-proton migration are operative in the Grubbs catalyst promoted reaction. 相似文献