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91.
Verma MK Ganneboyina SR R VR Ghatak A 《Langmuir : the ACS journal of surfaces and colloids》2008,24(5):2248-2251
Rapid mixing of liquids is important for most microfluidic applications. However, mixing is slow in conventional micromixers, because, in the absence of turbulence, mixing here occurs by molecular diffusion. Recent experiments show that mixing can be enhanced by generating transient flow resulting in chaotic advection. While these are planar microchannels, here we show that three-dimensional orientations of fluidic vessels and channels can enhance significantly mixing of liquids. In particular, we present a novel, multihelical microchannel system built in soft gels, for which the helix angle, helix radius, axial length, and even the asymmetry of the channel cross section are easily tailored to achieve the desired mixing. Mixing efficiency increases with helix angle and asymmetry of channel cross section, which leads to orders of magnitude reduction in mixing length over conventional mixers. This new scheme of generating 3D microchannels will help in miniaturization of devices, process intensification, and generation of multifunctional process units for microfluidic applications. 相似文献
92.
In this paper, we present two approximations for the fundamental mode of graded-index fibres. The first is a one-parameter analysis which involves computational effort comparable to that involved in the Gaussian approximation and yet gives much better results. The second is a two-parameter analysis which gives much better results than other existing approximations for all values ofV for most graded-index fibres.Visiting from Physics Department, Ravenshaw College, Cuttack 753003, India. 相似文献
93.
94.
Patil S Malasi A Majumder A Ghatak A Sharma A 《Langmuir : the ACS journal of surfaces and colloids》2012,28(1):42-46
Although the viscoelasticity or tackiness of a pressure-sensitive adhesive gives it strength owing to energy dissipation during peeling, it also renders it nonreusable because of structural changes such as the formation of fibrils, cohesive failure, and fouling. However, an elastic layer has good structural integrity and cohesive strength but low adhesive energy. We demonstrate an effective composite adhesive in which a soft viscoelastic bulk layer is imbedded in a largely elastic thin skin layer. The composite layer is able to meet the conflicting demands of the high peel strength comparable to the viscoelastic core and the structural integrity, reusability, and antifouling properties of the elastic skin. Our model adhesive is made of poly(dimethylsiloxane), where its core and skin are created by varying the cross-linking percentage from 2 to 10%. 相似文献
95.
Saheli Ganguly Kausik Dana Sankar Ghatak 《Journal of Thermal Analysis and Calorimetry》2010,100(1):71-78
Three n-alkylammonium salts of varying alkyl chain length were ion exchanged with montmorillonites (MMT) of different cation exchange
capacity (CEC). The intercalated MMTs were characterized by thermogravimetry (TG), XRD, FTIR to acquire an insight into the
intergallery structural arrangement of the organic alkylammonium cations (AAC). The increment in the intergallery spacing
from XRD pattern was correlated with chain length and interlayer arrangement of AAC. Multiple organic mass-loss stages in
thermogravimetric analysis indicate two types of anchorage of AAC in intercalated clay. CEC of MMT was found to influence
the intergallery confinement and excess adsorption of AAC. 相似文献
96.
An expeditious total synthesis of (±)-sempervirol (7) (±)-sugiol (8), and (±)-xanthopherol methyl ether (9) by extension of a simple general route is described. The stereochemical results of the cyclialkylation of 2-(2-p) and (2-m-isopropylphenylethyl)-1,3,3-trimethylcyclohexanols (1e) and (1f) follow the general pattern observed earlier. 相似文献
97.
A number of total syntheses of (±) - podocarpic acid (i) have been described1 King, King and Topliss2 first identified one of the products from nonstereo-selective cyclization of (4) with polyphosphoric acid as (±)- ethyl-O-methylpodocarpate (2) and correlated that with the corresponding acid (3), prepared in an extremly poor yield (ca 0.4%)3 by Bhattacharyya3, and Haworth and Moore4 by cyclization of (5) with a mixture of sulfuric acid and acetic acid. More recently Mancini, Fringuelli and Taticchi5 prepared (3) (in 4.8% yield) by repeating Howorth1 s cyclization of (4). In continuation of our studies on cyclialky- 相似文献
98.
Summary We have studied the Einstein relation of the diffusivity-mobility ratio of the carriers in Bi in accordance with the McClure
and Choi, the hybrid, the Cohen, the Lax and the ellipsoidal parabolic energy band models under magnetic quantization, cross-field
configuration, quantum wells, electric-field-aided quantum wells, quantum wells under cross-field configuration, quantumwell
wires, electrifield-aided quantum well wires and quantum well wires under cross-field configurations, respectively. The Einstein
relation varies with various physical variables in different manners which are totally band structure dependent. We have also
suggested an experimental method of determining the diffusivity-to-mobility ratio in degenerate materials having arbitrary
dispersion laws. 相似文献
99.
S. BhattacharyaD. De S.M. AdhikariS. Saha K.M. ChatterjeeS. Choudhury K.P. Ghatak 《Superlattices and Microstructures》2011,50(6):609-627
We present a simplified theoretical formulation of the Fowler-Nordheim field emission (FNFE) under magnetic quantization and also in quantum wires of optoelectronic materials on the basis of a newly formulated electron dispersion law in the presence of strong electric field within the framework of k.p formalism taking InAs, InSb, GaAs, Hg1−xCdxTe and In1−xGax AsyP1−y lattice matched to InP as examples. The FNFE exhibits oscillations with inverse quantizing magnetic field and electron concentration due to SdH effect and increases with increasing electric field. For quantum wires the FNFE increases with increasing film thickness due to the existence van-Hove singularity and the magnitude of the quantum jumps are not of same height indicating the signature of the band structure of the material concerned. The appearance of the humps of the respective curves is due to the redistribution of the electrons among the quantized energy levels when the quantum numbers corresponding to the highest occupied level changes from one fixed value to the others. Although the field current varies in various manners with all the variables in all the limiting cases as evident from all the curves, the rates of variations are totally band-structure dependent. Under certain limiting conditions, all the results as derived in this paper get transformed in to well known Fowler-Nordheim formula. 相似文献
100.
We complexify a 1-d potential V(x)=V0cosh2μ{tanh[(x−μd)/d]+tanh(μ)}2 which exhibits bound, reflecting and free states to study various properties of a non-Hermitian system. This potential turns out a PT-symmetric non-Hermitian potential when one of the parameters (μ,d) becomes imaginary. For the case of μ→iμ, we have an entire real bound state spectrum. Explicit scattering states are constructed to show reciprocity at certain discrete values of energy even though the potential is not parity symmetric. Coexistence of deep energy minima of transmissivity with the multiple spectral singularities (MSS) is observed. We further show that this potential becomes invisible from the left (or right) at certain discrete energies. The penetrating states in the other case (d→id) are always reciprocal even though it is PT-invariant and no spectral singularity (SS) is present in this case. The presence of MSS and reflectionlessness is also discussed for the free states in the later case. 相似文献