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951.
We report on the possibility of Q-switching a continuously pumped CO2 laser using a scanning Michelson interferometer as an end mirror, instead of the habitual well-known strategies. This method, in addition to its simplicity, produces free tail relaxation pulses having duration of about 1.3 μs, which is comparable to what can be obtained when using a saturable absorber. A pulse repetition frequency as high as 90 kHz is obtained. 相似文献
952.
The coherent states (CSs) of the SU(1,1) group can be divided into two broad categories: (a) the Barut-Girardello coherent
states (BGCSs) and (b) the Perelomov coherent states (PCSs). Some definitions for the squeezed displaced Fock states (SDFSs)
are given. The hyperbolic analytic representation in the complex plane is considered. An analytic representation of the SU(1,1)
Lie group is given and the representation in the unit disk based on the SU(1,1) PCSs for SDFSs is considered.
相似文献
953.
M. G. Abd El-Wahed Samy M. El-Megharbel Mohamed Y. El-Sayed Yasmin M. Zahran Moamen S. Refat 《Russian Journal of General Chemistry》2013,83(12):2438-2446
The complexation between lanthanide metal ions like Nd(III), Tb(III), and Er(III) with Glimepiride produces 1: 1 molar ratio (metal: Glimepiride) monodentate complexes of general formula: [M(GMP)(H2O)4]Cl3·xH2O, where: M = Nd, Tb, and Er, x = 1, 10, respectively. The structures of obtained compounds were assigned by IR, 1H NMR and UV/Vis spectra. Themogravimetric analysis and kinetic thermodynamic parameters have proved the thermal stability of Glimepiride complexes. Obtained lanthanide complexes showed significant effect against some bacteria and fungi. 相似文献
954.
955.
Karim Bedjeguelal Laure Joseph Véronique Bolitt Denis Sinou 《Journal of carbohydrate chemistry》2013,32(2):221-232
ABSTRACT The palladium(0)-catalyzed Heck-type cyclization-β-alkoxy elimination reaction leading to enantiopure bicyclic compounds in the case of erythro 2,3-unsaturated glycosides has been successfully extended to the threo stereoisomer by only changing the aglycon moiety from an ethoxy group to an aryloxy moiety. 相似文献
956.
The problem of extracting effective diffusivities of cement pastes on the basis of X-ray microtomography images is considered.
A general computational homogenization framework is developed and applied to a variety of cement pastes whose microstructure
has been digitized to a resolution of 1 μm. At this resolution, important submicron features are not resolved. Consequently,
we propose a methodology whereby the pore space is ascribed a diffusivity less than the free diffusivity. For this purpose,
a simple rule that incorporates microtomography data is proposed and shown to yield satisfactory results. 相似文献
957.
958.
Al-Mahboob A Muller E Karim A Muckerman JT Ciobanu CV Sutter P 《Journal of the American Chemical Society》2012,134(25):10381-10384
Doping catalytically inactive materials with dispersed atoms of an active species is a promising route toward realizing ultradilute binary catalyst systems. Beyond catalysis, strategically placed metal atoms can accelerate a wide range of solid-state reactions, particularly in hydrogen storage processes. Here we analyze the role of atomic Ti catalysts in the hydrogenation of Al-based hydrogen storage materials. We show that Ti atoms near the Al surface activate gas-phase H(2), a key step toward hydrogenation. By controlling the placement of Ti, we have found that the overall reaction, comprising H(2) dissociation and H spillover onto the Al surface, is governed by a pronounced trade-off between lowering of the H(2) dissociation barrier and trapping of the products near the active site, with a sharp maximum in the overall activity for Ti in the subsurface layer. Our findings demonstrate the importance of controlling the placement of the active species in optimizing the activity of dilute binary systems. 相似文献
959.
Marjan Hajy Alimohammadi Soheila Javadian Hussein Gharibi Ali reza Tehrani-Bagha Mohammad Rashidi Alavijeh Karim Kakaei 《The Journal of chemical thermodynamics》2012,44(1):107-115
The aggregation behavior of the cationic Gemini surfactants CmH2m+1N(CH3)2(CH2)S (CH3)2 N CmH2m+1,2Br? with m = 12, 14 and s = 2, 4 were studied by performing surface tension, electrical conductivity, pulsed field gradient nuclear magnetic resonance (PFG-NMR), and cyclic voltammetry (CV) measurements over the temperature range 298 K to 323 K. The critical micelle concentration (CMC), surface excess (Гmax), mean molecular surface area (Amin), degree of counter ion dissociation (α), and the thermodynamic parameters of micellization were determined from the surface tension and conductance data. An enthalpy–entropy compensation effect was observed and all the plots of enthalpy–entropy compensation exhibit excellent linearity. The micellar self-diffusion coefficients (Dm) and intermicellar interaction parameters (kd) were obtained from the PFG-NMR and CV measurements. These results are discussed in terms of the intermicellar interactions, the effects of the chain and spacer lengths on the micellar surface charge density, and the phase transition between spherical and rod geometries. The intermicellar interaction parameters were found to decrease slightly with increasing temperature for 14–4–14, which suggests that the micellar surface charge density decreases with increasing temperature. The mean values of the hydrodynamic radius, Rh, and the aggregation number, Nagg, of the Gemini surfactants’ m–4–m micelles were calculated from the micellar self-diffusion coefficient. Moreover, the Nagg values were calculated theoretically. The experimental values of Nagg increase with increases in the chain length and are in good agreement with both previous results and our theoretical results. 相似文献
960.
Abdel-Rahman El-Sayed Hossnia S. Mohran Hany M. Abd El-Lateef 《Monatshefte für Chemie / Chemical Monthly》2012,13(8):51-64