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101.
Physics of Atomic Nuclei - The results of fundamental studies of dynamic destruction and dispersion of metals in the pulsed volumetric heating mode under the effect of penetrating radiation allowed... 相似文献
102.
Selçuk Kayacan 《代数通讯》2018,46(4):1492-1505
The intersection graph of a group G is an undirected graph without loops and multiple edges defined as follows: the vertex set is the set of all proper non-trivial subgroups of G, and there is an edge between two distinct vertices H and K if and only if H∩K≠1 where 1 denotes the trivial subgroup of G. In this paper, we classify finite solvable groups whose intersection graphs are not 2-connected and finite nilpotent groups whose intersection graphs are not 3-connected. Our methods are elementary. 相似文献
103.
104.
Na3[BN2] and Na2K[BN2] were obtained as white polycrystalline powders from the reaction of the respective binary mixtures NaNH2:NaBH4 and NaNH2:KBH4 in molar ratio 2:1 at 873 K and 683 K, respectively, in an argon stream. According to the results of thermal analysis measurements, both compounds are thermally stable only up to 954 K (Na3[BN2]) and 712 K (Na2K[BN2]), respectively, decomposing under evolution of alkali metal and nitrogen to yield hexagonal BN as final residue, which was identified from powder patterns. The crystal structure of Na3[BN2] {β‐Li3[BN2] type; P21/c (No. 14); Z = 4} was confirmed and the unit cell parameters redetermined: a = 5.724(1) Å, b = 7.944(1) Å, c = 7.893(1) Å, β = 111.31(1)°. According to X‐ray powder data, Na2K[BN2] crystallizes isotypic to Na2KCuO2 in the tetragonal space group I4/mmm (No. 139) with a = 4.2359(1) Å, c = 10.3014(2) Å and Z = 2. The crystal structure of Na2K[BN2] is composed of linear [N–B–N]3– anions centering elongated M14 rhombic dodecahedra, which are formed by 8 sodium and 6 potassium atoms. The [BN2]@Na8/4K6/6 polyhedra are stacked along [001] and condensed via common tetragonal faces to generate a space‐filling 3D arrangement. The B–N bond lengths for the strictly linear [N–B–N]3– units are 1.357(4) Å. Vibrational spectra of the title compounds were measured and analyzed based on D∞h symmetry of the relevant [N–B–N]3– groups taking into account the site symmetry effects for Na3[BN2]. Both the wavenumbers, as well as the calculated valence force constants f(B–N) = 7.29 N · cm–1 (Na3[BN2]) and 7.33 N · cm–1 (Na2K[BN2]), respectively, are in good agreement with those of the known alkali and alkaline earth dinitridoborates. 相似文献
105.
X-ray diffraction studies of diamond films obtained by chemical transport reactions at the concentrations of 2% methane and 98% hydrogen under pressures of 10.7 and 21.3 kPa showed that they are textured. The character of the texture depends on the substrate temperature. The films have {110}, {311}, or double {110} + {311} textures. It is established that the dependence of the growth rate of diamond films on the substrate temperature has maxima. The diamond films are finely dispersed and are characterized by pronounced micro-deformations and high dislocation densities. The temperature dependence of the growth rate correlates with the parameters of the real structure of the films. 相似文献
106.
Preparation of a large Mesoporous CeO2 with crystalline walls using PMMA colloidal crystal templates
Inverse opals of crystalline CeO2 were synthesized by using close-packed poly(methyl methacrylate) (PMMA) latex spheres of various sizes as templates, resulting in pore sizes, which could be scaled down even to the mesopore region (30–40 nm). The latex spheres were synthesized by emulsion polymerization, and the PMMA particle size could be substantially decreased by addition of sodium dodecyl sulfate (SDS) as surfactant. Owing to the larger pore wall thickness, the CeO2 with large mesopores preserves an intact porosity to higher temperatures than previously reported mesoporous CeO2 obtained from surfactant templates. The porosity and crystallinity were studied by microscopic techniques, wide angle X-ray diffraction (XRD), N2 sorption, and Hg porosimetry. The evolution of crystallinity (crystallite size and lattice parameters) was determined for different annealing temperatures by means of Rietveld refinements of the XRD data. Thereby, our study allowed getting general insights into the crystallization behavior of sol–gel derived porous CeO2 frameworks. 相似文献
107.
J. Agrisuelas D. Ferrús C. Gabrielli J. J. García-Jareño H. Perrot O. Sel F. Vicente 《Russian Journal of Electrochemistry》2016,52(12):1137-1149
Poly(Neutral Red) (PNR) has been electrogenerated on a passivated Ni surface. PNR was chosen due to the fact that its electroactivity region overlaps with the Ni dissolution/deposition process. Therefore, both electrochemical processes can compete and by this way, there are evidences about the formation of a Ni(OH)2/PNR composite. It was investigated by classical EQCM and the instantaneous mass/charge ratio (F(dm/dQ)) analysis shed light on the active/passive transition and nickel trans-passive dissolution mechanisms. 相似文献
108.
Zeitschrift für Physik A Hadrons and nuclei - Erregt man den Luftraum der Vakuumanordnung mittels Teslaströmen zum Leuchten und läßt man von außen, durch die... 相似文献
109.
As a result of design, manufacturing and assembly processes or a wear effect, clearances are inevitable at the joints of mechanisms. In this study, dynamic response of mechanism having revolute joints with clearance is investigated. A four-bar mechanism having two joints with clearance is considered as a model mechanism. A neural network was used to model several characteristics of joint clearance. Kinematic and dynamic analyses were achieved using continuous contact mode between journal and bearing. A genetic algorithm was also used to determine the appropriate values of design variables for reducing the additional vibration effect due primarily to the joint clearance. The results show that the optimal adjusting of suitable design variables gives a certain decrease in shaking forces and their moments on the mechanism frame. 相似文献
110.
T. A. Ukleev N. N. Shevchenko D. I. Iurasova A. V. Sel’kin 《Physics of the Solid State》2018,60(5):916-920
The optical spectra of Bragg reflection from opal-like photonic crystals under conditions of the resonant enhancement of the multiple diffraction of light have been studied experimentally and theoretically using the photonic crystal structures prepared of monodisperse polystyrene globules. It is shown that the reflection signal registered in mutually orthogonal configurations of the polarizer and analyzer is related to the intrinsic optical anisotropy of the crystals and is a specific manifestation of the multiple Bragg diffraction in three-dimensional photonic crystals. 相似文献