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61.
Subrata?Kundu Anjali?Pal Sujit?Kumar?Ghosh Sudip?Nath Sudipa?Panigrahi Snigdhamayee?Praharaj Soumen?Basu Tarasankar?PalEmail author 《Journal of nanoparticle research》2005,7(6):641-650
Chelating ligands with β-diketone skeleton have been employed for the first time as reductant to produce ligand stabilized
gold nanoparticles of different shapes out of aqueous HAuCl4 solutions. Evolution of stable gold nanoparticles happens to be first order with respect to gold particles having rate constants
∼
∼10−2 min−1 and subsequent chlorine insertion in the β-diketone skeleton is reported as a general feature. Spherical or triangular or
hexagonal particle evolution goes selectively under the influence of different β-diketones in terms of capping and reducing
capabilities of the reductants. 相似文献
62.
Letp be any odd prime number. Letk be any positive integer such that
. LetS = (a
1,a
2,...,a
2p−k
) be any sequence in ℤp such that there is no subsequence of lengthp of S whose sum is zero in ℤp. Then we prove that we can arrange the sequence S as follows:
whereu ≥v,u +v ≥ 2p - 2k + 2 anda -b generates ℤp. This extends a result in [13] to all primesp andk satisfying (p + 1)/4 + 3 ≤k ≤ (p + 1)/3 + 1. Also, we prove that ifg denotes the number of distinct residue classes modulop appearing in the sequenceS in ℤp of length 2p -k (2≤k ≤ [(p + 1)/4]+1), and
, then there exists a subsequence of S of lengthp whose sum is zero in ℤp. 相似文献
(1) |
63.
The kinetics of oxidation of dimethyl, dipropyl, and diphenyl sulfides by pyridinium chloro chromate in chlorobenzene–nitrobenzene mixtures are reported. The rate data show Michaelis–Menten behavior. The oxidation process is catalyzed by the organic acids like dichloro and trichloro acetic acids. The rate-determining step appears to be a unimolecular decomposition of a complex of the reactants. 相似文献
64.
Schlieren measurements of the gradients of the concentration field around a KDP crystal growing from its aqueous solution are reported. The measurement of the concentration gradient field is important for crystal growth because it controls the rate of solute transport from the bulk of the solution to the crystal surface. In the crystal vicinity, the concentration gradients have a three dimensional distribution. The concentration gradient field has been imaged using monochrome schlieren technique. Four view angles, namely 0, 45, 90 and 135° have been utilized. By interpreting the schlieren images as projection data of solute concentration gradient, the three‐dimensional concentration gradient field around the crystal has been determined using an algebraic reconstruction technique. At low supersaturation levels, the growth process is accompanied by weak fluid movement during which diffusion effects are significant. At higher levels of supersaturation and large crystal size, a well‐defined convective plume around the growing crystal is observed. Reconstruction of concentration gradients around the crystal explains the preferential growth rates of various faces of the crystal. The non‐circular shape of the crystal is seen to affect the symmetry of the distribution of concentration gradients in its vicinity. The effect of crystal morphology on the orientation of convection currents rising from the crystal surface has also been brought out on the basis of the reconstructed concentration gradients distribution in the growth chamber. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
65.
66.
67.
68.
In the present paper, the authors introduce a new subclass of p-valent analytic functions with complex order defined on the open unit disk U={z:z∈C and |z|1} and obtain coefficient inequalities for the functions in these class. Application of these results for the functions defined by the convolution are also obtained. 相似文献
69.
Wakes behind heated cylinders, circular, and square have been experimentally investigated at low-Reynolds numbers. The electrically
heated cylinder is mounted in a vertical airflow facility such that buoyancy aids the inertia of main flow. The operating
parameters, i.e., Reynolds number and Richardson number are varied to examine flow behavior over a range of experimental conditions
from forced to mixed convection regime. Laser schlieren-interferometry has been used for visualization and analysis of flow
structures. Complete vortex shedding sequence has been recorded using a high-speed camera. The results on detailed dynamical
characteristics of vortical structures, i.e., their size, shape and phase, Strouhal number, power spectra, convection velocity,
phase shift, vortex inception length, and fluctuations are reported. On heating, alteration of organized (coherent) structures
with respect to shape, size and their movement is readily perceived from instantaneous Schlieren images before they reduce
to a steady plume. For both cylinders, Strouhal number shows a slow increase with an increase in Richardson number. At a critical
value, there is complete disappearance of vortex shedding and a drop in Strouhal number to zero. The corresponding spectra
evolve from being highly peaked at the vortex shedding frequency to a broadband appearance when vortex shedding is suppressed.
The geometry of vortex structures transforms to a slender shape before shedding is suppressed. At this heating level, absence
of multiple peaks in power spectra at cylinder centerline indicates absence of interaction between opposite shear layers.
The convection velocity of vortices increases in stream wise direction to an asymptotic value and its variation is a function
of Richardson number. The convection speed abruptly falls to zero at critical Richardson number. The phase difference of shed
vortices between upstream and downstream location increases with an increase in Richardson number. Velocity profiles show
an increase in fluid speed and beyond the critical point, buoyancy forces add enough momentum to cancel momentum deficit due
to the cylinder. Overall, the combined effect of temperature gradient on the separating shear layer velocity profile in near
field and vortical structures interaction in far field influences wake instability of a heated cylinder.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
70.
PIV investigation of flow behind surface mounted permeable ribs 总被引:2,自引:0,他引:2
The flow behind surface mounted permeable rib geometries, i.e. solid, slit, split-slit and inclined split-slit ribs have been
studied using flow visualization and PIV (2-C and 3-C) technique in streamwise and cross-stream measurement planes. The objective
behind this study is to understand the flow structures responsible for heat transfer/mixing enhancement with simultaneous
pressure penalty reduction by permeable rib geometries. The Reynolds number based on the rib height has been set equal to
5,538 and the open area ratio of permeable ribs is equal to 20%. The permeable rib geometries have shorter reattachment length
in comparison to the solid rib. The maximum 41% reduction in reattachment length is observed for the inclined split-slit rib.
The splitter mounted inside the slit leads to two corner vortices behind it. The corner vortices drag the flow from the primary
recirculation bubble region towards the rib resulting in drop of the reattachment length. Two horseshoe vortices are present
in the flow through the slit at both sides of the splitter due to the upstream flow separation. The slit inclination moves
these horseshoe vortices closer to the bottom wall. A film like flow through the slit is present near the downstream corner
of the inclined split-slit rib. The spanwise velocity gradient due to the splitter leads to vorticity and turbulence enhancement
by vortex stretching. The inclination of the slit and the use of a splitter inside the slit are two important design parameters
responsible in generation of near-wall longitudinal vortices. The flow field behind permeable ribs is dominated by vortical
structures with definable critical flow patterns, i.e. node, saddle and foci. These predominant swirling flow motions contribute
to the mixing enhancement behind permeable rib geometries.
On leave from Mechanical Engineering Department, IIT Kanpur, U.P. 208016, India 相似文献