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261.
The paper deals with a theoretical study of influence of magnetic field on effective viscosity of suspension of non-Brownian magnetizable particles. It is supposed that experimentally observed magnetorheological effects are provided by chain-like aggregates, consisting of the particles. Unlike previous works on this subject, we take into account that the chains cannot be identical and estimate their size distribution. The following power law (η-η0)/η0Mn-Δ, detected in many experiments, is obtained theoretically (η and η0 are the suspension effective viscosity and the carrier liquid viscosity, respectively, Mn is the so-called Mason number, proportional to the shear rate and inversely proportional to the square of magnetic field). The calculated magnitude of the exponent Δ increases with the applied magnetic field from approximately 0.66 to 0.8-0.9 and slowly increases with the volume concentration ? of the particles. These results are in agreement with known experiments.  相似文献   
262.
We report a novel type of electro-optical switching in a tilted smectic phase of bent-shaped mesogens. The switching consists of a continuous stage and two bistable transitions. Detailed optical and electro-optical measurements using high-speed imaging are given and possible interpretations of the experimental results are discussed.  相似文献   
263.
实验研究了双酚A在土壤表面的吸附特征及在土壤悬浮液中的光降解.研究结果表明,双酚A在土壤表面的吸附为单分子的化学吸附,用Langmuir模型或Freundlich模型拟合时相关性较好.在高压汞灯(λ=300nm)照射下,双酚A在土壤悬浮液中能快速降解,降解速度随酸度的增大而加快.在此体系中双酚A光降解动力学遵循Langmuir-Hinshelwood(H-L)方程,在土壤量不超过10g/L的条件下,降解率随土壤量增加而增加,加入腐殖酸可以促进双酚A的光解,同时增大光照强度有利于双酚A的降解.  相似文献   
264.
《Ultrasonics sonochemistry》2014,21(5):1641-1648
Conducting polyaniline (PANI) and cellulose coated PANI (PANI-NC) nanostructures with sizes of about 80–100 nm, doped with hydrochloric acid were synthesized by a sonochemical method. Both type of particles resulted electrically conductive (direct current conductivity of 0.059 and 0.075 S/cm for PANI and PANI-NC structures, respectively) and could be dispersed easily in water, leading to green colored suspensions that remain stable for more than 4 h. The morphology, crystallinity, electrical conductivity (σ) and thermal stability of the obtained PANI based structures were investigated and compared. Furthermore, UV–Vis spectroscopy and rheology of water suspensions were used to explain the measured properties. Although the concentration of cellulose fibers used to synthesize the PANI-NC structures was very low, important differences respect to the neat PANI fibers regarding the microstructure, electrical conductivity and suspension behavior were found.  相似文献   
265.
 Electrorheological behavior of silicone oil suspensions of macroporous poly[(glycidyl methacrylate)-co-(ethylene dimethacrylate)]) (0.60 : 0.40 w) hydrolyzed to various degrees was investigated. Polarizability of particles expressed by the particle dipole coefficient and, consequently, pseudoplasticity of the system at low shear rates after application of an external electric field steeply increased with the hydrolysis degree of the copolymer. As the size and shape of particles remain unchanged during hydrolysis, a series of model suspensions with the same hydrodynamic properties (Newtonian or slightly pseudoplastic when no electric field was applied) but with different intensity of the electrorheological effect could be prepared. Under these conditions, the use of Mason number failed to correlate the apparent viscosity of suspensions of particles with different polarizability in the electric field. On the other hand, when polarizability of particles of a suspension system changes due to a higher temperature, a single curve in the plot of apparent viscosity vs. the Mason number could be obtained. Received: 17 February 1998 Accepted: 8 May 1998  相似文献   
266.
The aggregation of 2D colloidal crystals can be performed by applying an AC field to a colloidal dispersion. This technique is used in this work for assembling multilamellar vesicles in suspension. The dynamics of the aggregation is followed by real-time recording of the pictures of the microsphere assembly through a phase contrast microscope. The influence of both the frequency and the amplitude of the alternating field on the dynamical evolution of the concentration of layered particles is discussed with respect to their size. A phenomenological model of double layer induced trapping of the particles is proposed and an electroconvective instability of the fluid surrounding the particles is suggested from the observation of the local dynamics of the particles, in accordance with a very recent argument of Yeh et al. [#!Yeh:97!#]. Received: 4 December 1997 / Revised: 24 March 1998 / Accepted: 4 May 1998  相似文献   
267.
The correlations between the segments of a semidilute polymer solution are found to induce correlations in the positions of small particles added to the solution. Small means a diameter much less than the polymer's correlation length. In the presence of polymer the particles behave as if they attracted each other. It is shown how the polymer's correlation length may be determined from a scattering experiment performed on the spheres. Received: 7 July 1997 / Received in final form: 12 November 1997 / Accepted: 19 November 1997  相似文献   
268.
A mathematical model of ignition of a coal-particle gas suspension is developed within the framework of mechanics of reacting heterogeneous media. Some qualitative features are studied, which reveal different typical variants of heat dynamics of the mixture: heterogeneous ignition caused by the coke residue ignition reaction, homogeneous ignition induced by volatile oxidation in the gas phase, and hybrid ignition due to the simultaneous effect of surface and volume reactions. Verification of the model is performed using available experimental data on ignition delay times for coal-particle suspensions in air and oxygen behind reflected shock waves. The model is extended to detonation processes in the suspension, verified by experimental data on the relation between the propagation velocity and initial particle concentration. Stationary detonation regimes are studied, and specific features of detonation structures are discussed.This paper was presented at the 18th International Colloquium on the Dynamics of Explosions and Reactive System, Seattle, Washington, USA, August, 2001  相似文献   
269.
The paper presents a passive elasto-magnetic suspension based on rare-earth permanent magnets: the dynamical system is described with theoretical and numerical nonlinear models, whose results are validated through experimental comparison. The goal is to minimize the dependence on mass of the natural frequency of a single degree of freedom system. For a system with variable mass, static configuration and dynamical behaviour are compared for classic linear elastic systems, for purely magnetic suspensions and for a combination of the two. In particular the dynamics of the magneto-mechanic interaction is predicted by use of nonlinear and linearised models and experimentally observed through a suitable single degree of freedom test rig.  相似文献   
270.
This paper is concerned with the development of a semi-active hydropneumatic spring and damper system, comprising of a two state hydropneumatic spring and a two state hydraulic damper. The system was specifically developed to improve the ride comfort and handling of large off-road vehicles. The suspension requirements for good ride comfort and handling for heavy off-road vehicles are discussed with special reference to the advantages of semi-active hydropneumatic springs and semi-active dampers. The layout and functioning of an experimental spring and damper unit used for laboratory tests are discussed. Spring and damper characteristics, as well as valve response times for both the semi-active spring and semi-active damper were determined. A single degree of freedom test rig with a sprung mass of 3 tons was used to perform first order ride comfort tests. Tests include step response and random input response. The test rig was also used to evaluate semi-active control strategies for both spring and damper as well as a control strategy for implementing ride height adjustment without using an external hydraulic pump.  相似文献   
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