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排序方式: 共有139条查询结果,搜索用时 31 毫秒
51.
We study theoretically the dynamics of a beam launched inside an amplifying trap potential. Raising the amplification transforms the dynamics from linear tunneling at low amplification to periodic ejection of a sequence of identical solitons (when the amplification rate exceeds the tunneling rate) and, at strong amplification, to nonperiodic multisoliton ejection. 相似文献
52.
Franti?ek?ZapletalEmail authorView authors OrcID profile Martin??míd 《Central European Journal of Operations Research》2016,24(2):435-454
We propose a mean-risk decision model for a steel company facing emission limits and trading with emission allowances. The model is calibrated using data of a real-life steel company and is subsequently solved for five different scenarios of demand and different levels of risk aversion. It is found that while the limits are never reached, permit trading influences the decision to a great extent, especially given extremely low or extremely high demand, i.e., when large amounts of permits need to be traded. We demonstrate that the risk caused by emission trading may increase not only with an increasing demand but also when the demand is low and a great amount of allowances must be sold. 相似文献
53.
Arturo Oró Fernando Romeo-Gella Dr. Josefina Perles Dr. Jesús M. Fernández-García Prof. Dr. Inés Corral Prof. Dr. Nazario Martín 《Angewandte Chemie (International ed. in English)》2023,62(49):e202312314
The bottom-up synthesis of 3D tetrakis(hexa-peri-hexabenzocoronenyl)methane, “tetrahedraphene”, is reported. This molecular nanographene constituted by four hexa-peri-hexabenzocoronene (HBC) units attached to a central sp3 carbon atom, shows a highly symmetric arrangement of the HBC units disposed in the apex of a tetrahedron. The X-ray crystal structure reveals a tetrahedral symmetry of the molecule and the packing in the crystal is achieved mostly by CH⋅⋅⋅π interactions since the interstitial solvent molecules prevent the π⋅⋅⋅π interactions. In solution, tetrahedraphene shows the same electrochemical and photophysical properties as the hexa-tBu-substituted HBC (tBu-HBC) molecule. However, upon water addition, it undergoes a fluorescence change in solution and in the precipitated solid, showing an aggregation induced emission (AIE) process, probably derived from the restriction in the rotation and/or vibration of the HBCs. Time-Dependent Density Functional Theory (TDDFT) calculations reveal that upon aggregation, the high energy region of the emission band decreases in intensity, whereas the intensity of the red edge emission signal increases and presents a smoother decay, compared to the non-aggregated molecule. All in all, the excellent correlation between our simulations and the experimental findings allows explaining the colour change observed in the different solutions upon increasing the water fraction. 相似文献
54.
Jorge AB Oró-Solé J Bea AM Mufti N Palstra TT Rodgers JA Attfield JP Fuertes A 《Journal of the American Chemical Society》2008,130(38):12572-12573
We have explored a new strategy to discover materials with large resistive or capacitive responses to magnetic fields by synthesizing EuMO2N (M = Nb, Ta) perovskites that combine ferromagnetic order of S = 7/2 Eu2+ spins with possible off-center distortions of the d0 M5+ cations enhanced by covalent bonding to N. EuNbO2N shows colossal magnetoresistances at low temperatures and a giant magnetocapacitance. However, the latter response originates from a microstructural effect rather than an intrinsic multiferroism. 相似文献
55.
Or Cohen 《Tetrahedron》2009,65(7):1361-2707
Aldehydes or ketones were reacted with 2-(trimethylsilyl)-1,3-dithiane (1) and the products reduced to the corresponding dithianes using tetrafluoroboric acid and sodium borohydride. These sulfur containing compounds were reacted with bromine trifluoride under mild conditions (1-2 min, 0 °C) with a net result of replacing the carbonyls' oxygen with the desired difluoromethyl moiety. 相似文献
56.
Colloidal interfacial interactions in a capillary channel under different chemical and flow conditions were studied using confocal microscopy. Fluorescent latex microspheres (1.1 microm) were employed as model colloids and the effects of ionic strength and flow conditions on colloidal retention at air-water interface (AWI) and contact line were examined in static and dynamic (flow) experiments. Colloids were preferentially attached to and accumulated at AWI, but their transport with bulk solution was non-negligible. Changing solution ionic strength in the range 1-100 mM had a marginal effect on colloidal accumulation, indicating forces other than electrostatic are involved. Flow through the open channel resembled Poiseuille flow with AWI acting as a non-stress-free boundary, which resulted in near stagnation of AWI and consequently promoted colloid accumulation. Retention on contact line was likely dominated by film-straining and was more significant in flow relative to static experiments due to hydrodynamic driving force. Modeling and dimensionless analysis of the flow behavior in the capillary channel clearly indicate the important role of apparent surface viscosity and surface tension in colloidal interfacial retention at the pore scale, providing insight that could improve understanding of colloid fate and transport in natural unsaturated porous media. 相似文献
57.
In the paper, reference-based nonuniformity correction methods for microbolometer infrared detectors are discussed and tested.
In order to evaluate their effectiveness, a complete readout circuit for amorphous silicon microbolometer focal plane array
has been designed. The tests were carried out on a developed stand including several extended blackbodies. Some modification
of standard two-point correction algorithm incorporating detectors response at external shutter to compensate offset drift
is also proposed. The obtained results are presented. 相似文献
58.
Omar Ayyad David Mu?oz-Rojas Judith Oró-Solé Pedro Gómez-Romero 《Journal of nanoparticle research》2010,12(1):337-345
Direct in situ reduction of silver ions by a biopolymer such as agar, without any other reducing nor capping agent is shown
in this article to lead either to nanoparticles (typically 12(2) nm in an optimized case) or to more complex nanostructures
depending on the reaction conditions used. This approach takes advantage of the porous polymer lattice acting as a template
and leads to hybrid Ag–Agar materials with long-term synergic stability. Silver acts as an antibacterial agent for agar whereas
the biopolymer prevents agglomeration of the inorganic nanoparticles leading to a stable nanocomposite formed by a thermoreversible
biopolymer from which silver nanoparticles can eventually be recovered. 相似文献
59.
We have investigated the adsorption of asymmetric poly(styrene-b-methyl methacrylate) block copolymers (PS-PMMA) from a selective solvent onto alumina (Al(2)O(3)) particles having variable and controllable radii. The solvent used was a bad solvent for the PS block (block A) and a good solvent for the PMMA block (block B), which has a higher affinity of the surface. Such a case represents a new class of adsorption, where both blocks compete for the adsorption sites of the metallic surface. Two theoretical models, the modified drops model and the perforated film model, have been evaluated as appropriate representation of such an adsorption scenario. The experimental results indicated that the adsorption of the PS-PMMA block copolymer generated a patterned surface comprised of a homogeneous melt layer of the PS block perforated with holes having a variable PMMA structure, depending on the distance from the bottom of the hole (alumina surface) and the distance from walls of the hole. The density gradient of the PMMA moiety in the hole reverted to the classical brush morphology at a critical distance from the surface of the hole. 相似文献
60.