全文获取类型
收费全文 | 1015篇 |
免费 | 197篇 |
国内免费 | 262篇 |
专业分类
航空 | 1003篇 |
航天技术 | 156篇 |
综合类 | 186篇 |
航天 | 129篇 |
出版年
2024年 | 3篇 |
2023年 | 19篇 |
2022年 | 32篇 |
2021年 | 43篇 |
2020年 | 53篇 |
2019年 | 57篇 |
2018年 | 47篇 |
2017年 | 38篇 |
2016年 | 65篇 |
2015年 | 63篇 |
2014年 | 73篇 |
2013年 | 56篇 |
2012年 | 66篇 |
2011年 | 81篇 |
2010年 | 55篇 |
2009年 | 77篇 |
2008年 | 69篇 |
2007年 | 60篇 |
2006年 | 44篇 |
2005年 | 36篇 |
2004年 | 37篇 |
2003年 | 37篇 |
2002年 | 41篇 |
2001年 | 19篇 |
2000年 | 27篇 |
1999年 | 27篇 |
1998年 | 30篇 |
1997年 | 24篇 |
1996年 | 26篇 |
1995年 | 19篇 |
1994年 | 28篇 |
1993年 | 23篇 |
1992年 | 29篇 |
1991年 | 23篇 |
1990年 | 12篇 |
1989年 | 14篇 |
1988年 | 20篇 |
1987年 | 1篇 |
排序方式: 共有1474条查询结果,搜索用时 15 毫秒
651.
ATLAS2K--以信号描述为核心的可扩展的可移植的自动测试语言 总被引:2,自引:0,他引:2
详细介绍了以信号描述为核心的新一代测试语言ATLAS2K的特点及层模型,并提出了ATLAS2K在自动测试设备ATE中的应用。 相似文献
652.
实验研究了端壁孔式附面层抽吸对带间隙的高负荷直列叶栅流动特性和气动性能的影响,通过三种附面层抽吸方案与原型方案的对比分析,探讨了附面层抽吸抑制间隙流动、减小损失的机理。对叶片表面和下端壁进行了墨迹流动显示,并利用五孔探针对叶栅出口气动参数进行了测量,对比分析了叶栅流道内的流场特征和损失分布。结果表明,在间隙内布置抽吸孔能有效降低间隙流动动能,削弱间隙流与主流之间的相互掺混作用,减小因间隙流动引起的端壁区域流动分离,从而达到对三维流动分离的抑制,有效降低损失,且最大降幅达16.7%;间隙流动引起的流动分离和损失在流道中占主导地位,尽管在端壁沿周向合理布置抽吸孔能在一定程度上抑制近端壁的附面层或二次流发展,但这种局部效应仍不能显著改善叶栅的整体性能;端壁上不合理的抽吸控制策略反而可能影响主流的正常流动,导致损失增加,其中方案4损失增加了约3%。 相似文献
653.
654.
655.
656.
《中国航空学报》2021,34(5):504-509
The interaction length induced by Shock Wave/Turbulent Boundary-Layer Interactions (SWTBLIs) in the hypersonic flow was investigated using a scaling analysis, in which the interaction length normalized by the displacement thickness of boundary layer was correlated with a corrected non-dimensional separation criterion across the interaction after accounting for the wall temperature effects. A large number of hypersonic SWTBLIs were compiled to examine the scaling analysis over a wide range of Mach numbers, Reynolds numbers, and wall temperatures. The results indicate that the hypersonic SWTBLIs with low Reynolds numbers collapse on the supersonic SWTBLIs, while the hypersonic cases with high Reynolds numbers show a more rapid growth of the interaction length than that with low Reynolds numbers. Thus, two scaling relationships are identified according to different Reynolds numbers for the hypersonic SWTBLIs. The scaling analysis provides valuable guidelines for engineering prediction of the interaction length, and thus, enriches the knowledge of hypersonic SWTBLIs. 相似文献
657.
Christian Freksa Thomas Barkowsky Zoe Falomir Jasper van de Ven 《Spatial Cognition & Computation》2019,19(1):46-68
Humans solve spatial and abstract problems more easily if these can be visualized and/or physically manipulated. We analyze the domain of geometric problem solving from a cognitive perspective and identify several levels of domain abstraction that interact in the problem solving process. We discuss the roles of physical manifestations of spatial configurations, their manipulation, and their perception for understanding problem solving processes. We propose an extension of the classical problem solving repertoire of constructive geometry to approach certain problems more directly than under the compass-and-straightedge paradigm. Specifically, we introduce strings and pins as helpful metaphors for a generalization of the constructive geometry approach. We present classical problems from spatial problem solving to illustrate the ‘strings and pins’ paradigm. Three case studies are discussed: strings-and-pins solutions to (i) the ellipse construction problem; (ii) the shortest path problem; and (iii) the angle trisection problem. Comparisons to formal solutions are drawn. Differences and similarities between the compass-and-straightedge paradigm and the strings-and-pins paradigm are analyzed. Features and limitations of constructive and depictive geometry as well as implications for computational approaches are discussed. The strings-and-pins domain is shown to be more general and less restrictive than the compass-and-straightedge domain. 相似文献
658.
《中国航空学报》2020,33(12):3460-3468
The YSZ coatings are prepared by the plasma spray-physical vapor deposition (PS-PVD) technology based on a specific experimental design. The structure, thickness and growth angle of YSZ coatings on the entire circumferential surface of the cylindrical sample are studied. The results indicated that the structure, thickness and deflection growth angle of YSZ coatings are related to the orientation of deposition location. The numerical simulation of the multiphase mixed fluid near the substrate is carried out and the deposition regularity and mechanism of YSZ coatings prepared by PS-PVD is deduced. The growth rate is related to the local characteristics of the plasma flow field, and is directly proportional to the field pressure and inversely proportional to the field velocity. The growth angle of the coating is generally affected by the flow direction of the plasma jet. Especially, the normal component of velocity vector, Vnorm, mainly affects the speed at which the coating grows vertically upwards. The tangential component of velocity vector, Vtan, determines the degree that the coating growth direction deviates from the vertical direction. When Vtan ≠ 0, the coating forms a fine column with a certain deflection angle and finally develops into an oblique columnar structure. 相似文献
659.
This paper summarizes the results of the researches on the middle and upper atmosphere obtained by Chinese scientists in 2008-2010. The focuses are specifically placed on the researches being associated with ground-based observation capability development, dynamical processes, the property of atmospheric circulation and the chemistry-climate coupling of the middle atmospheric layers. 相似文献
660.
研究了反作用飞轮的故障诊断问题.针对反作用飞轮的非线性数学模型,分析了其故障模式,建立了其故障的参数化描述方法,并在此基础上提出了一种基于参数自适应投影的反作用飞轮故障诊断方法.该方法通过构造观测器,利用参数自适应投影算法来更新参数信息,保证观测器的误差收敛到零.最后对飞轮的正常模式和3种故障模式进行了物理仿真实验,结果表明提出的方法有效可行. 相似文献