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   2783篇
  免费   346篇
  国内免费   457篇
航空   1555篇
航天技术   756篇
综合类   546篇
航天   729篇
  2024年   2篇
  2023年   8篇
  2022年   29篇
  2021年   51篇
  2020年   40篇
  2019年   26篇
  2018年   27篇
  2017年   23篇
  2016年   51篇
  2015年   74篇
  2014年   110篇
  2013年   134篇
  2012年   135篇
  2011年   197篇
  2010年   191篇
  2009年   155篇
  2008年   200篇
  2007年   185篇
  2006年   133篇
  2005年   137篇
  2004年   88篇
  2003年   110篇
  2002年   92篇
  2001年   116篇
  2000年   108篇
  1999年   147篇
  1998年   151篇
  1997年   123篇
  1996年   114篇
  1995年   88篇
  1994年   101篇
  1993年   91篇
  1992年   70篇
  1991年   68篇
  1990年   54篇
  1989年   39篇
  1988年   28篇
  1987年   35篇
  1986年   12篇
  1985年   10篇
  1984年   9篇
  1983年   5篇
  1982年   13篇
  1981年   3篇
  1980年   1篇
  1965年   2篇
排序方式: 共有3586条查询结果,搜索用时 220 毫秒
531.
简要说明了资源卫星数据收集系统(DCS)的原理、组成和特点,在对分布范围广、参数缓变和传输速率低的数据进行采集方面,资源卫星DCS具有很大的优势和很高的利用价值。结合环保监测应用的需求,对资源卫星DCS应用系统方案进行了详细设计。  相似文献   
532.
叙述了某型直升机主减滑油冷却风扇性能测试试验情况,并对进口风扇和国产风扇的性能作了分析比较,为该型直升机国产化风扇性能作出了结论,同时为直升机用风扇性能试验总结了经验。  相似文献   
533.
Wu  C.C. 《Space Science Reviews》2003,107(1-2):219-226
The magnetopause is in continuous motion and shock waves and impulsive acceleration events can occur. As an example, we show that the interaction of an interplanetary shock with the bow shock can generate a shock wave that after passing through the magnetosheath can interact with the magnetopause. In fluid dynamics, when a shock wave encounters a fluid discontinuity, the interface may become unstable and form bubbles and spikes. We consider this Richtmyer-Meshkov instability in magnetohydrodynamics. At the dayside magnetopause, the instability tends to be stabilized by the magnetic field. However, the shock wave interaction can initiate magnetic field reconnection for the southward IMF, which may be important in strong interplanetary shock events. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   
534.
Chang  Tom  Tam  Sunny W.Y.  Wu  Cheng-Chin  Consolini  Giuseppe 《Space Science Reviews》2003,107(1-2):425-445
The first definitive observation that provided convincing evidence indicating certain turbulent space plasma processes are in states of ‘complexity’ was the discovery of the apparent power-law probability distribution of solar flare intensities. Recent statistical studies of complexity in space plasmas came from the AE index, UVI auroral imagery, and in-situ measurements related to the dynamics of the plasma sheet in the Earth's magnetotail and the auroral zone. In this review, we describe a theory of dynamical ‘complexity’ for space plasma systems far from equilibrium. We demonstrate that the sporadic and localized interactions of magnetic coherent structures are the origin of ‘complexity’ in space plasmas. Such interactions generate the anomalous diffusion, transport, acceleration, and evolution of the macroscopic states of the overall dynamical systems. Several illustrative examples are considered. These include: the dynamical multi- and cross-scale interactions of the macro-and kinetic coherent structures in a sheared magnetic field geometry, the preferential acceleration of the bursty bulk flows in the plasma sheet, and the onset of ‘fluctuation induced nonlinear instabilities’ that can lead to magnetic reconfigurations. The technique of dynamical renormalization group is introduced and applied to the study of two-dimensional intermittent MHD fluctuations and an analogous modified forest-fire model exhibiting forced and/or self-organized criticality [FSOC] and other types of topological phase transitions. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   
535.
Feng  Xueshang  Wu  S.T.  Wei  Fengsi  Fan  Quanlin 《Space Science Reviews》2003,107(1-2):43-53
It has been believed that three-dimensional, numerical, magnetohydrodynamic (MHD) modelling must play a crucial role in a seamless forecasting system. This system refers to space weather originating on the sun; propagation of disturbances through the solar wind and interplanetary magnetic field (IMF), and thence, transmission into the magnetosphere, ionosphere, and thermosphere. This role comes as no surprise to numerical modelers that participate in the numerical modelling of atmospheric environments as well as the meteorological conditions at Earth. Space scientists have paid great attention to operational numerical space weather prediction models. To this purpose practical progress has been made in the past years. Here first is reviewed the progress of the numerical methods in solar wind modelling. Then, based on our discussion, a new numerical scheme of total variation diminishing (TVD) type for magnetohydrodynamic equations in spherical coordinates is proposed by taking into account convergence, stability and resolution. This new MHD model is established by solving the fluid equations of MHD system with a modified Lax-Friedrichs scheme and the magnetic induction equations with MacCormack II scheme for the purpose of developing a combined scheme of quick convergence as well as of TVD property. To verify the validation of the scheme, the propagation of one-dimensional MHD fast and slow shock problem is discussed with the numerical results conforming to the existing results obtained by the piece-wise parabolic method (PPM). Finally, some conclusions are made. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   
536.
本文提出了如何解决机械式拉力试验机存在的问题的方法,介绍了单片机数据采集,处理系统的软硬件,对一些关键问题给出了比较详细的介绍。  相似文献   
537.
本文提出了研究Transition区谱分布的静电模型,并按等离子体弱耦强湍理论对其重正化得到了谱方程.对谱方程作适当近似后,证明了该近似谱方程存在扰动密度谱为k~(-5),扰动电场谱为k~(-3)分布的解,从而定量解释了Transition区的实验谱分布结果.  相似文献   
538.
539.
在研制飞行模拟器时,飞行模拟器的设计和性能数据是必需的。这些数据不仅是形成满足飞行模拟器各种规范和标准要求的基础,而且也是构成模拟器逼真度要求的基础。根据国际航空运输协会的要求,初步讨论了编制飞行模拟器设计和性能数据要求所考虑的因素。  相似文献   
540.
试论高等数学教学与 CAI   总被引:2,自引:0,他引:2  
阐述了CAI在数学教学中的重要作用,以实例说明了在CAI实验课教学中应注意的几个方面,并对目前数学CAI教学所面临的问题进行了探讨  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