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121.
Haiss W van Zalinge H Higgins SJ Bethell D Höbenreich H Schiffrin DJ Nichols RJ 《Journal of the American Chemical Society》2003,125(50):15294-15295
Spontaneous formation of stable molecular wires between a gold scanning tunneling microscopy (STM) tip and substrate is observed when the sample has a low coverage of alpha,omega-dithiol molecules and the tunneling resistance is made sufficiently small. Current-distance curves taken under these conditions exhibit characteristic current plateaux at large tip-substrate separations from which the conductivity of a single molecule can be obtained. The versatility of this technique is demonstrated using redox-active molecules under potential control, where substantial reversible conductivity changes from 0.5 to 2.8 nS were observed when the molecule was electrochemically switched from the oxidized to the reduced state. 相似文献
122.
D.J. Schiffrin 《Journal of Electroanalytical Chemistry》1975,63(3):283-286
The meaning of the “red limit” potential in photoemission experiments is discussed. For mercury in contact with aqueous electrolytes, the energy of a photoemitted electron at the “red limit” is 0.6 eV higher than the solvation energy of eaq?. This difference is attributed to the solvent reorganization energy contribution to the hydration energy of eaq?. 相似文献
123.
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125.
Esther Domínguez Esther Lete María-Jesús Villa Amaia Igartua Nuria Sotomayor Juan M. Arrieta Agustin Berisa Luis Labeaga Aurelio Orjales Gabriel Germain Vassilios Nastopoulos 《Journal of heterocyclic chemistry》1991,28(8):1885-1889
7 The8,3′,4′-tetramethoxyisoflavone 2 was synthesized and its structure confirmed by X-ray crystallographic analysis. Pharmacological screening was carried out with this compound in order to assess its pharmacological profile. Isoflavone 2 possessed antiinflamatory activity in the carrageenan oedema test, with a dose-effect relationship comparable to that of hydroxylated flavonoids. It is noteworthy that 2 is one of the few isoflavones efficient as antiinflammatory with complete alkylation of hydroxyl groups. 相似文献
126.
A. N. Nesmeyanov T. P. Tolstaya A. V. Grib Khose Agustin Kazanova 《Russian Chemical Bulletin》1973,22(5):1052-1056
Conclusions The salt of a new completely aromatic ammonium cation, namely 4, 4-diphenyl-7-oxodibenzo-1, 4-dihydrodiazepinium iodide, was obtained, the structure of which was confirmed by qualitative tests with silver hydroxide, aqueous NaOH solution, and nitrosylsulfuric acid.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1096–1101, May, 1973. 相似文献
127.
The bimolecular rate constant for the direct reaction of chlorine atoms with methane was measured at 25°C by using the very-low-pressure-pyrolysis technique. The rate constant was found to be In addition, the ratio k1/k?1 was observed with about 25% accuracy: K1(298) = 1.3 ± 0.3. This gives a heat of formation of the methyl radical ΔH° f 298(CH3) = 35.1 ± 0.15 kcal/mol. A bond dissociation energy BDE (CH3 ? H) = 105.1 ± 0.15 kcal/mol in good agreement with literature values was obtained. 相似文献
128.
Syntheses of the (divalent group 14 species)dicarbonyl(cyclopentadienyl)manganese (Salen)M=Mn(CO)2(eta 5-C5H5) [M = Ge (1), Sn (2), Pb (3)] and [(Salen)tin(II)]tetracarbonyliron (Salen)Sn=Fe(CO)4 (4) are reported. The structures of 2 and 4 were determined by X-ray crystallography. The observed Sn-Mn bond length, 2.4428(7) A, is the shortest distance observed for this type of bond and corresponds to considerable multiple bonding between these atoms. In complex 4, the iron atom has a slightly distorted trigonal-bipyramidal coordination sphere; the (Salen)tin(II) ligand occupies an axial site, indicating that it functions in this complex as a strong sigma-donor and weak pi-acceptor ligand. Crystal data for 2: orthorhombic, P2(1)2(1)2(1), a = 6.972(1) A, b = 15.678(2) A, c = 19.032(2) A, alpha = beta = gamma = 90 degrees, V = 2080.3(5) A3, T = 173(2) K, Z = 4. Crystal data for 4: triclinic, P1, a = 8.465(2) A, b = 9.795(3) A, c = 13.213(4) A, alpha = 105.55(3) degrees, beta = 105.15(3) degrees, gamma = 100.84(3) degrees, V = 978.7(5) A3, T = 173(2) K, Z = 2. 相似文献
129.
A confirmatory and sensitive procedure has been developed for the determination of 40 currently used pesticides (CUPs) in airborne particulate matter (PM 10) at trace level. The proposed method includes extraction of PM 10-bound pesticides by microwave-assisted extraction (MAE) followed by a gel permeation chromatography (GPC) clean-up and determination by GC-MS/MS. The injection mode and the main parameters in MS/MS were optimized. The matrix effect was also evaluated. Recoveries ranged from 70 to 120% except for pyrimethanil and pirimicarb. The limit of quantification (LOQ) ranged from 1.32 to 39.47 pg m(-3), when air volumes of 760 m(3) were collected. The method was applied to 38 samples collected from a rural station belonging to the atmospheric monitoring network of the Regional Valencia Government (Spain) during April-June 2010. Eighteen out of 40 pesticides investigated were found in at least one sample (bifenthrin, chlorothalonil, chlorpyriphos-e, chlorpyriphos-m, clorpropham, diazinon, dicofol, diphenylamine, fipronil, fludioxonil, folpet, malathion, metalaxyl, penconazole, quinoxyfen, triadimefon, trifluralin, and vinclozoline), with concentrations ranging from 1.32 to 625.80 pg m(-3). 相似文献
130.
A survey of the parallel performance and accuracy of Poisson solvers for electronic structure calculations
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Pablo García‐Risueño Joseba Alberdi‐Rodriguez Micael J. T. Oliveira Xavier Andrade Michael Pippig Javier Muguerza Agustin Arruabarrena Angel Rubio 《Journal of computational chemistry》2014,35(6):427-444
We present an analysis of different methods to calculate the classical electrostatic Hartree potential created by charge distributions. Our goal is to provide the reader with an estimation on the performance—in terms of both numerical complexity and accuracy—of popular Poisson solvers, and to give an intuitive idea on the way these solvers operate. Highly parallelizable routines have been implemented in a first‐principle simulation code (Octopus ) to be used in our tests, so that reliable conclusions about the capability of methods to tackle large systems in cluster computing can be obtained from our work. © 2013 Wiley Periodicals, Inc. 相似文献