全文获取类型
收费全文 | 83篇 |
免费 | 11篇 |
国内免费 | 15篇 |
专业分类
航空 | 39篇 |
航天技术 | 30篇 |
综合类 | 8篇 |
航天 | 32篇 |
出版年
2023年 | 2篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 8篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2016年 | 6篇 |
2015年 | 3篇 |
2014年 | 5篇 |
2013年 | 3篇 |
2012年 | 7篇 |
2011年 | 12篇 |
2010年 | 11篇 |
2009年 | 7篇 |
2008年 | 3篇 |
2007年 | 5篇 |
2006年 | 3篇 |
2005年 | 3篇 |
2004年 | 1篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2001年 | 6篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
排序方式: 共有109条查询结果,搜索用时 31 毫秒
91.
箭上直角棱镜误差对方位瞄准精度的影响 总被引:4,自引:0,他引:4
给出了直角棱镜反射光矢量的完整表达式,在此基础上讨论了棱镜放置误差和角度误差对方位瞄准精度的影响。 相似文献
92.
93.
Jiang Zhihong Huang Fukan Wan Jianwei Cheng Zhu 《中国航空学报》2007,20(4):339-345
This paper presents a modified frequency scaling algorithm for frequency modulated continuous wave synthetic aperture radar (FMCW SAR) data processing. The relative motion between radar and target in FMCW SAR during reception and between transmission and reception will introduce serious dilation in the received signal. The dilation can cause serious distortions in the reconstructed images using conventional signal processing methods. The received signal is derived and the received signal in range-Doppler domain is given. The relation between the phase resulting from antenna motion and the azimuth frequency is analyzed. The modified frequency scaling algorithm is proposed to process the received signal with serious dilation. The algorithm can effectively eliminate the impact of the dilation. The algorithm performances are shown by the simulation results. 相似文献
94.
湍流标度律的变化情况显示了湍流边界层内的流动状况。利用高分辨率、高帧率的粒子图像测速技术(PIV)对平板湍流边界层进行了实验研究。研究结果显示,当脉动速度增量结构函数的阶数为正整数且逐渐增大时,由实验所得的脉动速度增量结构函数的标度指数逐渐偏离K41和SL标度指数,出现奇异标度律;而当结构函数的阶数为正分数时,实验所得的标度指数和K41及SL标度指数较为接近;当结构函数的阶数由0趋向于-1时,实验的标度指数明显偏离K41和SL标度指数,出现奇异标度律。这也说明了用低阶结构函数的标度指数也能说明标度律的奇异性及边界层内存在间歇性。对于法向速度增量和涡量分量来说,不管结构函数的高阶或低阶的标度指数都不随壁面位置的不同而改变,具有普适性。 相似文献
95.
径厚比对锥柱形金属膜片屈曲和后屈曲状态的影响 总被引:2,自引:1,他引:2
通过有限元方法研究了半径及径厚比对锥柱形金属膜片翻转过程的影响,并选取典型的半径及径厚比样本点对分析结论进行了数值验证.研究结果表明:膜片半径太小或太大均表现出一定的尺寸效应,小半径膜片的尺寸效应更显著;半径为203~403mm的膜片其屈曲和后屈曲状态表现出明显的一致性;对于确定半径的膜片,径厚比太大,膜片承载能力太小而导致翻转效率较低,径厚比太小,膜片屈曲载荷呈指数级显著增加而不易翻转,径厚比为160~400的膜片其翻转效率较好,并且后屈曲状态表现出一致性;选取典型的样本点对结论进行了数值验证,一致性较好. 相似文献
96.
97.
K.D. Moloto N.E. Engelbrecht R.D. Strauss D.M. Moeketsi J.P. van den Berg 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(1):626-639
Three-dimensional studies of the transport and modulation of cosmic ray particles in turbulent astrospheres require large-scale simulations using specialized scientific codes. Essentially, a multi-dimensional Fokker-Planck type equation (a parabolic diffusion equation) must be integrated numerically. One such approach is to convert the relevant transport equation into a set of stochastic differential equations (SDEs), with the latter much easier to handle numerically. Due to the growing demand for high performance computing resources, research into the application of effective and suitable numerical algorithms to solve such equations is needed. We present a case study of the performance of a custom-written FORTRAN SDE numerical solver on the CHPC (Centre for High Performance Computing) Lengau cluster in South Africa for a realistic test problem with different set-ups. It is shown that SDE codes can scale very well on large parallel computing platforms. Finally, we consider an extremely computationally expensive application of the SDE approach to cosmic ray modulation, studying the behaviour of galactic cosmic ray proton latitude gradients and relative amplitudes in a physics-first manner. This is done using a modulation code that employs diffusion coefficients derived from first principles, which in turn are functions of turbulence quantities in reasonable agreement with spacecraft observations and modelled using a two-component turbulence transport model (TTM). We show that this approach leads to reduced latitude gradients qualitatively in line with spacecraft observations of the same, without making ad hoc assumptions as to anisotropic perpendicular diffusion coefficients as are often made in many cosmic ray modulation studies. 相似文献
98.
99.
100.