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The focus of this study lies on turbulent incompressible swirling flows with high swirl intensity. A systematic parameter study is conducted to examine the sensitivity of the mean velocity field in a swirl chamber to changes in the Reynolds number, swirl intensity and channel outlet geometry. The investigated parameter range reflects the typical kinematic flow conditions found in heat transfer applications, such as the cooling of the turbine blade known as cyclone cooling. These applications require a swirl intensity, which is typically much higher than necessary for vortex breakdown. The resulting flows are known as flow regime II and III. In comparison to flow regime I, which denotes a swirling flow without vortex breakdown, these flow regimes are characterized by a subcritical behavior. In this context, subcritical means that the flow is affected by the downstream channel section. Based on mean velocity field measurements in various swirl chamber configurations, it is shown that flow regime III is particularly sensitive to these effects. The channel outlet geometry becomes a determining parameter and, therefore, small changes at the outlet can produce entirely different flow patterns in the swirl chamber. In contrast, flow regime II, as well as flow regime I and axial channel flows, are much less sensitive to changes at the channel outlet. The knowledge about the sensitivity of the flow in different flow regimes is highly relevant for the design of a cyclone cooling system. Cooling systems employing flow regime III can result in a weakly robust flow system that may change completely over the operating range. As a remedy, the swirl intensity needs to be decreased so that flow regime III cannot be reached, which, however, reduces the maximum achievable heat transfer in the cooling system. Alternatively, the flow has to transition back from flow regime III to flow regime II or I before the flow leaves the swirl chamber. Two practical methods are presented. These findings can be directly applied in the design processes of future cyclone cooling systems, and other applications of swirling flow. 相似文献
33.
Alexander John Finch 《Pramana》2007,69(5):703-706
The results presented at this conference in the γγ technology group are described.
相似文献
34.
D S Narayan 《Pramana》1979,12(4):391-395
The production of prompt neutrinos in the beam dump experiment is explained in a cluster model, by postulating the emission
of strange clusters in hadron collisions, besides the usual non-strange clusters. The low mass strange clusters can decay
only by the weak interaction. The leptonic and semi-leptonic decay modes of these clusters give rise to prompt neutrinos.
A prediction of the model is that the ratios <v
e>/π
+ at PS energies would be the same as SPS energies. 相似文献
35.
The paper presents large eddy simulations of co-annular swirling jets into an open domain. In each of the annuli a passive
scalar is introduced and its transport is computed. If the exit of the pilot jet is retracted strong coherent flow structures
are generated which substantially impact on the transport and mixing of the scalars. Average and instantaneous fields are
discussed to address this issue. A conditional averaging technique is devised and applied to velocity and scalars. This allows
to quantify the impact of the coherent structures on the mixing process. 相似文献
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为了探索液体碳氢燃料参与旋转爆轰所产生的不完全燃烧现象,采用守恒元与求解元方法,开展柱坐标系下的汽油/空气两相旋转爆轰燃烧室三维数值模拟研究,针对燃料喷注压力和反应物当量比对旋转爆轰流场结构及燃烧室性能的影响进行分析。分析结果表明:保持总当量比为1.00,随着燃料喷注压力的上升,燃烧室内燃料不均匀分布增强,产生局部富燃区,燃料在燃烧室未能完全反应,导致燃烧室燃料比冲下降;保持喷注压力不变,减小当量比,在贫燃工况下依然存在局部富燃区,导致燃烧室内出现不完全燃烧现象,降低燃烧室比冲性能。由此可知,反应物喷注方案对气液两相旋转爆轰的不完全燃烧有显著影响。 相似文献
40.
A presumed probability density function (PDF) model for temperature fluctuation is proposed and formulated in this paper. It incorporates the four-step reaction mechanism of methane combustion. A set of analytical expressions is derived for the time-averaged four-step reaction rates. The model is employed to numerically simulate methane turbulent swirling flame in the TECFLAM combustor. The calculated gas axial, radial and tangential velocities, species mass fractions, temperature, and temperature fluctuation are compared with the measured test data. Agreement is achieved between the calculation and the measurement. 相似文献