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81.
The diffuse vibrational bands, observed in the ultraviolet photodissociation spectrum of nitrous oxide by exciting the molecule in the first (1)A' state, have recently been attributed to resonances localized mainly in the NN stretch and bend degrees of freedom. To further investigate the origin of this localization, fundamental families of periodic orbits emanating from several stationary points of the (1)A' potential energy surface and bifurcations of them are computed. We demonstrate that center-saddle bifurcations of periodic orbits are the main mechanism for creating stable regions in phase space that can support the partial trapping of the wave packet, and thus they explain the observed spectra. A non-linear mechanical methodology, which involves the calculation of equilibria, periodic orbits, and transition states in normal form coordinates, is applied for an in detail exploration of phase space. The fingerprints of the phase space structures in the quantum world are identified by solving the time dependent Schro?dinger equation and calculating autocorrelation functions. This demonstrates that different reaction channels could be controlled if exact knowledge of the phase space structure is available to guide the initial excitation of the molecule. 相似文献
82.
Alkynyl indoles undergo a novel sequence of Pd-catalysed indole C-H activation/alkyne carbopalladation/arylation, with diaryliodonium salts providing the aryl components. An array of functionalised indole alkenes have been prepared in good to excellent yield, with the reaction being selective for the Z-alkene. 相似文献
83.
This work shows for the first time the potential of cobalt oxide silica (CoO(x)Si) membranes for desalination of brackish (1 wt.% NaCl), seawater (3.5 wt.% NaCl) and brine (7.5-15 wt.% NaCl) concentrations at feed temperatures between 25 and 75 °C. CoO(x)Si xerogels were synthesised via a sol-gel method including TEOS, cobalt nitrate hydrate and peroxide. Initial hydrothermal exposure (<2 days) of xerogels prepared with various pH (3-6) resulted in densification of the xerogel via condensation reactions within the silica matrix, with the xerogel synthesised at pH 5 the most resistant. Subsequent exposure was not found to significantly alter the pore structure of the xerogels, suggesting they were hydrostable and that the pore sizes remained at molecular sieving dimensions. Membranes were then synthesised using identical sol-gel conditions to the xerogel samples and testing showed that elevated feed temperatures resulted in increased water fluxes, whilst increasing the saline feed concentration resulted in decreased water fluxes. The maximum flux observed was 1.8 kg m(-2) h(-1) at 75 °C for a 1 wt.% NaCl feed concentration. The salt rejection was consistently in excess of 99%, independent of either the testing temperature or salt feed concentration. 相似文献
84.
Zuaznabar-Gardona JC Cao R Cao R Suarez M 《Chemical communications (Cambridge, England)》2012,48(13):1910-1912
Multiwalled carbon nanotubes modified with 2-aminoethanethiol (MWNT-AET) were vertically self-assembled on gold electrodes with the assistance of chitosan and Tween. According to AFM and cyclic voltammetric determinations the best results were achieved using chitosan. 相似文献
85.
It is interesting to make a comparison of important intensity parameters, such as the Franck-Condon factors1, against experimental values. This is the scope of this work, where we present a comparison of FC factors with our measurements of relative intensity of the P(15) lines of seven bands (43-0, 43-1, 43-2, 43-9, 43-10, 43-11, 43-18, 43-19 and 43-20) of iodine. As laser induced fluorescence has became an important tool in the study of collision dynamics a contribution to the picture of energy release in relaxation processes of a molecule in a high lying vibrational level is of some benefit. 相似文献
86.
Sebastin Suarez Fabio Doctorovich Ricardo Baggio 《Acta Crystallographica. Section C, Structural Chemistry》2012,68(10):o417-o420
The title compound, C21H21NO7S3, consists of an SO2ON(SO2)2 central fragment and three terminal 4‐methylphenyl groups each attached at a sulfonyl S atom. The most obvious characteristic is the presence of two nearly face‐to‐face benzene rings, with their centroids separated by a rather short distance [3.7808 (18) Å], but with a rather slanted relative orientation [dihedral angle = 20.63 (13)°] so as to preclude a strong intramolecular π–π interaction. The third benzene ring is nearly perpendicular to the other two [dihedral angles = 71.62 (14) and 70.4 (13)°]. The packing of the structure is directed by two C—H...O hydrogen bonds involving aromatic H atoms (methyl H atoms are strictly non‐interacting), which define chains running in the [100] direction. These one‐dimensional chains evolve parallel to each other and exhibit no significant lateral interactions. 相似文献
87.
O.J. Suarez P. Vargas E.E. Vogel 《Journal of magnetism and magnetic materials》2009,321(22):3658-3664
The interaction energy and force between two parallel thin magnetic nanotubes is calculated using four different approaches. Although they agree for separation distances over 10 times the radius of any tube, some differences appear for shorter distances. Two exact methods giving identical results face handling difficulties in comparison with an approximate method based on a truncated expansion which produces fair enough results for distances to be found in the range of interest. Numerical calculations are done for cobalt particles of dimensions corresponding to nanotubes already manufactured and with properties reported in the literature. The force between two identical and parallel Co nanotubes , separated by a distance of 300 nm is of the order of few microdynes. 相似文献
88.
E. Soudah M. Bordone A. Álvarez J. Cobo F. De Carlos B. Suarez 《Revista Internacional de Métodos Numéricos para Cálculo y Dise?o en Ingeniería》2012,28(4):237-242
Obstructive sleep apnea syndrome (OSAS) consists in the occurrence of recurrent episodes of airflow limitation during sleep, with undesirable consequences for the health. The phenomenon is well known from a medical point of view (prognosis, diagnosis and treatment), but there is not a methodology or analysis tools for the quantification of the clinical response using Mandibular Advancement Devices (MAD). This paper shows how combining image processing, fluid dynamics and engineering design criteria, imported from other fields, allow to establish a simple analysis method clinically useful to decide the more convenient positioning of the MAD based on the pressure or mechanical movement of the jaw. This methodology is applied to a patient suffering OSAS which the objective to evaluate the changes provoked in the upper-airways due to an innovative mandibular device. 相似文献
89.
90.
Cristian Paz Robles Viviana Burgos Sebastin Suarez Ricardo Baggio 《Acta Crystallographica. Section C, Structural Chemistry》2014,70(11):1007-1010
The natural compound dendocarbin A, C15H22O3, is a sesquiterpene lactone isolated for the first time from Drimys winteri for var chilensis. The compound crystallizes in the orthorhombic space group P212121 and its X‐ray crystal structure confirmed the S/R character of the chiral centres at C‐5/C‐10 and C‐9/C‐11, respectively. The α‐OH group at C‐11 was found to be involved in intermolecular hydrogen bonding, defining chains along the <100> 21 screw axis. 相似文献