全文获取类型
收费全文 | 277篇 |
免费 | 116篇 |
国内免费 | 48篇 |
专业分类
航空 | 270篇 |
航天技术 | 101篇 |
综合类 | 11篇 |
航天 | 59篇 |
出版年
2024年 | 1篇 |
2023年 | 22篇 |
2022年 | 29篇 |
2021年 | 33篇 |
2020年 | 22篇 |
2019年 | 20篇 |
2018年 | 6篇 |
2017年 | 22篇 |
2016年 | 23篇 |
2015年 | 8篇 |
2014年 | 20篇 |
2013年 | 12篇 |
2012年 | 13篇 |
2011年 | 16篇 |
2010年 | 14篇 |
2009年 | 7篇 |
2008年 | 8篇 |
2007年 | 13篇 |
2006年 | 15篇 |
2005年 | 4篇 |
2004年 | 11篇 |
2003年 | 9篇 |
2002年 | 5篇 |
2001年 | 11篇 |
2000年 | 13篇 |
1999年 | 12篇 |
1998年 | 12篇 |
1997年 | 12篇 |
1996年 | 5篇 |
1995年 | 8篇 |
1994年 | 3篇 |
1993年 | 7篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1990年 | 9篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 4篇 |
排序方式: 共有441条查询结果,搜索用时 593 毫秒
171.
地地导弹射击精度评估方法 总被引:3,自引:0,他引:3
地地导弹的射击精度是地地导弹主要的战术技术指标之一,它的评定是人们一直关心的问题,本文首次从满足作战使用的要求出发建立了射击精度评定的统计假设检验,应用Bootstrap方法研究了小样本情况下地地导弹射击精度的评定和区间估计方法.最后以某型号导弹为例,对其靶场飞行试验数据进行了计算,说明了本文方法的有效性.本文提出的方法对地地导弹射击精度的评估和其它同类武器射击精度的评估具有重要的实用和参考价值. 相似文献
172.
173.
174.
固体表面温度和热流的直接测量在某些情况下是很困难的。使用“过去的”和“将来的”测量时间 ,引入稳定矩阵的概念 ,抑制了导热反问题的误差放大作用。通过埋设在固体内部的热电偶的温度测量 ,同时对固体表面的温度和热流进行了有效估算 相似文献
175.
用光的角散射分布技术测量工件表面的粗糙度参数是近几年来发展起来的新的测量技术。它具有分辨力高、非接触、区域平均和快速测量等优点,可获得多个表面粗糙度参数。采用该技术测量的实验装置角分辨力为0.1°,测量范围为0.6328μm<λ_s(空间平均波长)<40μm,0.0001<△_a(轮廓的算术平均斜率)<0.0088,2nm相似文献
176.
介绍了一种基于光针法的表面形貌测量装置,它能在线测量加工工件圆周方向的波纹度和轴向表面轮廓形貌,其垂直分辨率为0.02~0.10μm,横向分辨率为30~50μm。切削试验表明,该装置能够在线识别刀具上的积屑瘤、切削过程中的颤振和刀具磨损对加工表面形貌的影响。 相似文献
177.
Michael Angelopoulos David Redman Wayne H. Pollard Timothy W. Haltigin Peter Dietrich 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
Ground-penetrating radar (GPR) is the leading geophysical candidate technology for future lunar missions aimed at mapping shallow stratigraphy (<5 m). The instrument’s exploration depth and resolution capabilities in lunar materials, as well as its small size and lightweight components, make it a very attractive option from both a scientific and engineering perspective. However, the interaction between a GPR signal and the rover body is poorly understood and must be investigated prior to a space mission. In doing so, engineering and survey design strategies should be developed to enhance GPR performance in the context of the scientific question being asked. This paper explores the effects of a rover (simulated with a vertical metal plate) on GPR results for a range of heights above the surface and antenna configurations at two sites: (i) a standard GPR testing site with targets of known position, size, and material properties, and; (ii) a frozen lake for surface reflectivity experiments. Our results demonstrate that the GPR antenna configuration is a key variable dictating instrument design, with the XX polarization considered optimal for minimizing data artifact generation. These findings could thus be used to help guide design requirements for an eventual flight instrument. 相似文献
178.
Georgiana Y. Kramer 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
This paper describes the rationale, methodology, and importance of focusing on the rim and proximal ejecta of small (<5 km in diameter), immature impact craters to explore an underlying crustal lithology. Small Crater Rim and Ejecta Probing (SCREP) describes a methodology and application program that extracts bedrock spectral and compositional information from a remote sensing image. Extracted data can yield the pristine lithologies of a planetary crust that would otherwise be obscured by the products of space weathering processes. SCREP was developed with lunar data, specifically Clementine multispectral image mosaics, therefore the technique is discussed in this context. However, its application to other airless solar system bodies is apparent. Knowledge of the pristine bedrock compositions of a planetary crust provides insight into geological surface processes, which can be used to refine models of planetary interiors and their evolution. 相似文献
179.
《中国航空学报》2020,33(9):2313-2328
Actuator Disks (AD) can provide characterizations of rotor wakes while reducing computational expense associated with modeling the fully resolved blades. This work presents an unsteady actuator disk method based on surface circulation distribution combined with empirical data, blade element theory and rotor momentum theory. The nonuniform circulation distribution accounts for 3D blade load effects, and in particular, tip loses. Numerical simulations were conducted for the isolated pressure sensitive paint model rotor blade in hover and forward flight using the HMB3 CFD solver of Glasgow University. Validation of CFD results in comparison with published numerical data was performed in hover, for a range of blade pitch angles using fully turbulent flow and the k-ω SST model. In forward flight, the vortex structures predicted using the unsteady actuator disk model showed configurations similar to the ones obtained using fully resolved rotor blades. Despite the reduced grid cells number, the CFD results for AD models captured well the main vortical structures around the rotor disk in comparison to the fully resolved cases. 相似文献
180.