首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   349篇
  免费   51篇
  国内免费   105篇
航空   284篇
航天技术   96篇
综合类   33篇
航天   92篇
  2023年   6篇
  2022年   8篇
  2021年   12篇
  2020年   18篇
  2019年   14篇
  2018年   16篇
  2017年   15篇
  2016年   18篇
  2015年   31篇
  2014年   19篇
  2013年   16篇
  2012年   29篇
  2011年   35篇
  2010年   28篇
  2009年   26篇
  2008年   42篇
  2007年   20篇
  2006年   22篇
  2005年   19篇
  2004年   6篇
  2003年   17篇
  2002年   12篇
  2001年   10篇
  2000年   11篇
  1999年   13篇
  1998年   8篇
  1997年   2篇
  1996年   5篇
  1995年   6篇
  1994年   6篇
  1993年   3篇
  1992年   4篇
  1991年   4篇
  1990年   1篇
  1989年   2篇
  1988年   1篇
排序方式: 共有505条查询结果,搜索用时 15 毫秒
111.
针对高速弹载平台加速度大相参积累效果变差需进行加速度补偿的问题,研究了信号波长和积累时间与加速度之间的关系,推导了利用多普勒谱宽计算加速度的公式,提出短时间积累使用弹载惯导设备输出加速度值进行补偿、长时间积累使用惯导数据与多普勒谱宽测量加速度相结合的加速度补偿方法。仿真验证了该方法的有效性。  相似文献   
112.
针对如何获取运动平台的实时加速度和在精确跟踪加速度的同时限制位移,建立了系统动力学模型以计算加速度,使用虚拟弹簧法限制位移。在Matlab环境下,搭建了整个伺服控制系统。仿真结果表明,控制系统在保证平台位移不脱离限制区域的基础上,实现了加速度的精确跟踪。  相似文献   
113.
We calculate the maximum energy that a particle can obtain at perpendicular interplanetary shock waves by the mechanism of diffusive shock acceleration. The influence of the energy range spectral index of the two-dimensional modes of the interplanetary turbulence is explored. We show that changes in this parameter lead to energies that differ in at least one order of magnitude. Therefore, the large scale structure of the turbulence is a key input if the maximum particle energy is calculated.  相似文献   
114.
介绍了在冲击加速度校准中,为了抑制电、机械等干扰和噪声对冲击加速度测量结果的影响,采用二阶巴特沃斯型低通滤波器,通过时间序列翻转、二次滤波等方式,实现零相移的低通滤波效果。并比较不同截止频率下,低通滤波器对衰减程度不同的冲击加速度波形产生的峰值偏差,给出不同加速度波形下,低通滤波器截止频率选择应注意的问题。  相似文献   
115.
An effect of the Coriolis forces on the process of gas expansion in the turbine stage is considered. Expressions for efficiency with regard for the radial flow passage are derived. The calculation results and statistical data on the geometric parameters of diagonal stages are presented.  相似文献   
116.
By the data on intensity-time profiles of the neutron capture line of 2.223 MeV we have studied some characteristics of two solar flares, 28 October 2003 and 20 January 2005 (INTEGRAL and CORONAS-F observations, respectively). The SINP code was applied making allowance for the main processes of neutron interactions and deceleration in the solar plasma, character of neutron source, losses of neutrons and density model of the solar atmosphere. Comparison of the computed time profiles of 2.223 MeV line with observed ones for the flare of 28 October 2003 confirms the results obtained earlier for three other flares. Namely, the effect of density enhancement (EDE) in the sub-flare region, as well as the variations (hardening) of accelerated particle spectrum in the course of the event have been confirmed. The usual modeling procedure by the SINP code, however, seems to be inapplicable to the event of 20 January 2005. Possible causes of density enhancements during some flares and peculiarities of the 20 January 2005 flare are discussed.  相似文献   
117.
The interaction between electromagnetic waves and matter is the working principle of a photon-propelled spacecraft, which extracts momentum from the solar radiation to obtain a propulsive acceleration. An example is offered by solar sails, which use a thin membrane to reflect the impinging photons. The solar radiation momentum may actually be transferred to matter by means of various optical phenomena, such as absorption, emission, or refraction. This paper deals with the novel concept of a refractive sail, through which the Sun’s light is refracted by crossing a film made of polymeric micro-prisms. The main feature of a refractive sail is to give a large transverse component of thrust even when the sail nominal plane is orthogonal to the Sun-spacecraft line. Starting from the recent literature results, this paper proposes a semi-analytical thrust model that estimates the characteristics of the propulsive acceleration vector as a function of the sail attitude angles. Such a mathematical model is then used to analyze a simplified Earth-Mars and Earth-Venus interplanetary transfer within an optimal framework.  相似文献   
118.
Radio tracking of interplanetary probes is an important tool for navigation purposes as well as for testing the laws of physics or exploring planetary environments. The addition of an accelerometer on board a spacecraft provides orbit determination specialists and physicists with an additional observable of great interest: it measures the value of the non-gravitational acceleration acting on the spacecraft, i.e. the departure of the probe from geodesic motion.  相似文献   
119.
张立彬 《飞行力学》1998,16(2):74-77
在分析飞机的纵向阻尼力矩时,除考虑俯仰角速度引起的俯仰阻尼力矩外,还应估算出迎角变化率引起的洗流时差阻尼力矩。根据洗流时差阻尼力矩产生的原理,推导并给出了它的计算方法。介绍了各种阻尼导数的表示方法及相互关系。最后较详细地分析了水平尾翼、马赫数、迎角变化率和下洗角随迎角的变化率诸因素对洗流时差阻尼力矩及阻尼导数的影响。  相似文献   
120.
Based upon the most efficient electron acceleration near the midplane of 3D non-neutral driven reconnecting current sheet (RCS) and the electrostatic wave excitation by the drift Maxwellian distribution of electrons in Vlasov simulation, we assume that the electrostatic waves mainly propagate opposite to the reconnecting electric field and investigated how these waves affect the electron acceleration. The main results are: (1) when the electron’s velocity equals to the phase speed of the waves, they will be trapped and have the different accelerating characteristics from the untrapped electrons through solving the momentum equations of electrons analytically; (2) the test particle simulations further prove that the number of the energetic electrons decreases with the increasing intensity of unstable waves, and the distribution of the energetic electrons takes on the double power-law.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号