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61.
62.
Frija LM Reva ID Gómez-Zavaglia A Cristiano ML Fausto R 《The journal of physical chemistry. A》2007,111(15):2879-2888
A combined matrix isolation FT-IR and theoretical DFT(B3LYP)/6-311++G(d,p) study of the molecular structure and photochemistry of 5-ethoxy-1-phenyl-1H-tetrazole (5EPT) was performed. A new method of synthesis of the compound is described. Calculations show three minima, very close in energy and separated by low-energy barriers (less than 4 kJ mol-1), in the ground-state potential energy profile of the molecule. The method of matrix isolation enabled the reduction of the number of populated conformational states in the experiment at low temperature due to the effect known as conformational cooling. As a result, the spectrum of the as-deposited matrix of 5EPT closely matches that of the most stable conformer predicted theoretically, pointing to the existence of only this conformer in the low-temperature matrixes. In this structure, the dihedral angle between the two rings, phenyl and tetrazole, is ca. 30 degrees, whereas the ethyl group stays nearly in the plane of the tetrazole ring and is as far as possible from the phenyl group. In situ UV irradiation (lambda > 235 nm) of the matrix-isolated 5EPT induced unimolecular decomposition, which led mainly to production of ethylcyanate and phenylazide, this later compound further reacting to yield, as final product, 1-aza-1,2,4,6-cycloheptatetraene. Anti-aromatic 3-ethoxy-1-phenyl-1H-diazirene was also observed experimentally as minor photoproduct, resulting from direct extrusion of molecular nitrogen from 5EPT. This species has not been described before and is now characterized by infrared spectroscopy for the first time. 相似文献
63.
Bryzgunov M. I. Bubley A. V. Denisov A. P. Parkhomchuk V. V. Panasyuk V. M. Reva V. B. Putmakov A. A. 《Physics of Particles and Nuclei Letters》2020,17(4):429-433
Physics of Particles and Nuclei Letters - Electron-beam energy recuperation is usually used in electron-cooling systems (ECSs). The operation stability, vacuum conditions, and radiation background... 相似文献
64.
Rostkowska H Lapinski L Reva I Almeida BJ Nowak MJ Fausto R 《The journal of physical chemistry. A》2011,115(44):12142-12149
Monomeric 3,6-dithiopyridazine (3-mercapto- 6(1H)-pyridazinethione) was studied using the matrix-isolation method combined with quantum chemical calculations. The monomers of 3,6-dithiopyridazine, trapped from the gas phase into a low-temperature Ar matrix, were found to adopt the thione-thiol structure. In agreement with this experimental observation, the thione-thiol form was predicted (at the QCISD level) to be more stable by 13.5 kJ mol(-1) and by 39.6 kJ mol(-1) than the dithiol and the dithione tautomers, respectively. Monomers of 3,6-dithiopyridazine isolated in Ar matrixes were then irradiated with broadband UV (λ > 335 nm) light. Upon such irradiation, the thione-thiol form of the compound converted into the dithiol tautomer. The same phototransformation was observed when monochromatic λ = 385 nm laser light was used for irradiation. This allowed a first observation and spectral characterization of the dithiol form of 3,6-dithiopyridazine. Subsequent irradiation of the UV-generated dithiol tautomer with shorter-wavelength UV (λ > 275 nm) light led to partial repopulation of the thione-thiol form. Spectral signatures of the analogous photoreversibility were also found for the phototautomeric transformation in the model compound 3-thiopyridazine. The reliability of the QCISD predictions of relative energies of thiol and thione tautomeric forms was tested on the archetype example of 2-thiopyridine. For this compound, the comparison of the computed relative energy 10.9 kJ mol(-1) with the experimental estimate 10.0 ± 1.5 kJ mol(-1) (both in favor of the thiol form) was more than satisfactory. 相似文献
65.
Marzec KM Reva I Fausto R Proniewicz LM 《The journal of physical chemistry. A》2011,115(17):4342-4353
In the present work, γ-terpinene (a 1,4-diene derivative) and α-phellandrene (1,3-diene derivative) were isolated in cryogenic argon matrices and their structures, vibrational spectra, and photochemistries were characterized with the aid of FTIR spectroscopy and quantum chemical calculations performed at the DFT/B3LYP/6-311++G(d,p) level of approximation. The molecules bear one conformationally relevant internal rotation axis, corresponding to the rotation of the isopropyl group. The calculations provide evidence of three minima on the potential energy surfaces of the studied molecules, where the isopropyl group assumes the trans, gauche+, and gauche- conformations (T, G+, G-). The signatures of all these conformers were identified in the experimental matrix infrared spectra, with the T forms dominating, in agreement with the theoretical predicted abundances in gas phase at room temperature. In situ UV (λ > 200 nm) irradiation of matrix-isolated α-phellandrene led to its isomerization into an open-ring species. The photoproduct was found to exhibit the ZE configuration of its backbone, which to be formed from the reactant molecule does not require extensive structural rearrangements of both the reagent and matrix. γ-Terpinene was photostable when subjected to irradiation under the same experimental conditions. In addition, the liquid compounds at room temperature were also investigated by FTIR-ATR and FT-Raman spectroscopies. 相似文献
66.
S. V. Kuzin S. A. Bogachev A. A. Pertsov S. V. Shestov A. A. Reva A. S. Ulyanov 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(1):87-90
Observing the Sun’s hot corona with sub-second spatial resolution is important in solving a number of basic solar physics
problems. The new ARCA satellite observatory under development at the Lebedev Physical Institute, Russian Academy of Sciences,
will be first to provide images of the hot solar corona with a spatial resolution of about 0.18 arcsec. Scientific and technical
features of the observatory are discussed. 相似文献
67.
The spectral sensitivity of Sn(II) complexes in acid and alkaline solutions of SnCl2 in photostimulated oxidation with oxygen was studied. The reaction mechanism was revealed. A spectrophotometric method for prompt monitoring of the composition of SnCl2 solutions was proposed. 相似文献
68.
G. M. Mikhailov V. G. Mikhailov L. S. Reva G. V. Ryabchuk 《Russian Journal of Applied Chemistry》2005,78(7):1067-1072
An equation for precision fitting of the temperature dependence of density of any substance in the entire temperature range of its liquid state and an equation for the prediction of the coefficient of thermal expansion, derived from this dependence, was considered. Constants of the equation for 50 liquids were tabulated. 相似文献
69.
70.
Mikhailov G. M. Mikhailov V. G. Reva L. S. Ryabchuk G. V. 《Russian Journal of Applied Chemistry》2004,77(4):670-672
An equation for predicting the normal temperature depression in boiling of complex aqueous solutions of nonvolatile substances is considered. The constants of the equation are tabulated. The equation is compared with experimental data for a binary solution of caustic soda and sodium chloride. 相似文献