全文获取类型
收费全文 | 53篇 |
免费 | 8篇 |
国内免费 | 18篇 |
专业分类
力学 | 53篇 |
综合类 | 3篇 |
数学 | 8篇 |
物理学 | 15篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2020年 | 1篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 2篇 |
2015年 | 4篇 |
2014年 | 3篇 |
2013年 | 4篇 |
2012年 | 7篇 |
2011年 | 4篇 |
2010年 | 2篇 |
2009年 | 4篇 |
2008年 | 5篇 |
2007年 | 4篇 |
2006年 | 2篇 |
2005年 | 4篇 |
2004年 | 3篇 |
2003年 | 3篇 |
2002年 | 3篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1991年 | 2篇 |
1987年 | 1篇 |
排序方式: 共有79条查询结果,搜索用时 15 毫秒
21.
为了定量分析空化初始航速的影响因素,首先分析侧斜和负载对螺旋桨无空化和有空化时性能的影响。以NSRDC4381无侧斜桨和4383100%侧斜桨为对象,采用改进Sauer空化模型和修正SST湍流模型,对空化崩溃性能、空化初生性能和无空化时正车、倒车以及紧急倒车敞水性能进行了计算与比较。结果表明,预报两个桨的敞水性能曲线和多空化数下的空化崩溃性能曲线均与实验值吻合较好。在中度负载区间(J=0.5-0.9)内,侧斜对正车和紧急倒车时敞水性能以及空化时推力和力矩崩溃性能均无明显影响,但会使倒车敞水性能显著下降。在重载和轻载条件下,侧斜均能明显改善空化初生性能。侧斜一定时,负载会直接影响尾流湍流速度脉动量和涡核集中区分布,影响轴面速度流管收缩程度,进而影响无空化和有空化条件下的推进性能。 相似文献
22.
This paper describes a method for the automatic identification of acoustic events using a weighted average of sound pressure and sound intensity measured at the vicinity of airports. The classification is based on the combination of different parameters using a technique conceptually similar to the sensor fusion: the indications of different classifiers are merged using the classification uncertainty as a figure of merit. The method uses the results of a training phase for the observation of statistical distributions of sound pressure and sound intensity related parameters. The different parameters’ weights are computed analyzing the overlap of probability distributions of takeoffs and landings, so that more relevance is given to the quantities presenting a low risk of misclassification. The proposed method does not require any arbitrary assumption about the parameter effectiveness, given that the indications of multiple (potentially infinite) classifiers can be merged together with weights that minimize the chance of misclassification. The method has been validated with measurements performed at the Milan Malpensa airport (Italy). Results outlined that the proposed classification criterion correctly identifies approximately 99% of events. 相似文献
23.
T. E. Carter 《Journal of Optimization Theory and Applications》1987,54(3):447-470
Singular solutions of a linearized problem of determining fuel-optimal trajectories of a spacecraft with bounded thrust near a satellite in circular orbit are investigated in detail. Mathematical results are presented which classify and discuss degeneracy of the singular solutions and which show that strictly singular and nonsingular solutions are mutually exclusive for fixed-end conditions. These results are consistent with those found using other approaches for other linear models, but they are not characteristic of the type of results obtained without linearization. 相似文献
24.
S. A. Takovitskii 《Fluid Dynamics》2009,44(1):129-134
The problem of designing supersonic nozzles that provide maximum exhaust thrust is considered. An analytical solution is derived on the basis of a local analysis of the aerodynamic force distribution. It is shown that near-optimal thrust characteristics are realized by nozzles with a power-law dependence of the radius on the longitudinal coordinate with an exponent 2/3. The study is performed within the framework of the Euler model of an inviscid, non-heat-conducting gas. 相似文献
25.
26.
27.
针对大气层内拦截导弹直接侧向力与气动力复合控制系统设计问题, 首先, 根据发动机的配置建立了复合控制系统模型;其次, 提出了复合控制策略, 包括动态分配算法、直接力控制子系统、气动力控制子系统3部分; 然后, 在考虑两套执行机构动态特性差别的情况下,基于预测控制思想给出了过载误差动态分配算法; 在此基础上, 根据直接侧向力的离散特性, 基于预测控制方法设计了直接力控制规律, 考虑到直接力控制作用对弹体产生的扰动, 基于自抗扰方法设计了气动力子系统; 最后, 通过仿真验证了直接力气动力复合控制策略与方法的有效性. 相似文献
28.
主要阐述了如何对锥形穿孔机顶杆小车的位置进行控制.通过对理想控制算法的改进,寻找到了一种既能满足顶杆小车快速性,又同时满足系统稳定性和可靠性的一种现实算法. 相似文献
29.
30.
In this paper, we investigate the role of morphing on flight dynamics of two birds by simulating the flow over rigid and morphing wings that have the characteristics of two different birds, namely the Giant Petrel and Dove Prion. The simulation of a flapping rigid wing shows that the root of the wing should be placed at a specific angle of attack in order to generate enough lift to balance the weight of the bird. However, in this case the generated thrust is either very small, or even negative, depending on the wing shape. Further, results show that morphing of the wing enables a significant increase in the thrust and propulsive efficiency. This indicates that the birds actually utilize some sort of active wing twisting and bending to produce enough thrust. This study should facilitate better guidance for the design of flapping air vehicles. 相似文献