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   529篇
  免费   28篇
  国内免费   19篇
航空   266篇
航天技术   224篇
综合类   25篇
航天   61篇
  2023年   20篇
  2021年   3篇
  2020年   16篇
  2019年   15篇
  2018年   8篇
  2017年   2篇
  2016年   2篇
  2015年   3篇
  2014年   41篇
  2013年   11篇
  2012年   14篇
  2011年   20篇
  2010年   12篇
  2009年   24篇
  2008年   53篇
  2007年   52篇
  2006年   31篇
  2005年   29篇
  2004年   10篇
  2003年   13篇
  2002年   6篇
  2001年   40篇
  2000年   8篇
  1999年   8篇
  1998年   19篇
  1997年   2篇
  1996年   14篇
  1995年   14篇
  1994年   62篇
  1993年   15篇
  1992年   1篇
  1990年   2篇
  1989年   2篇
  1984年   4篇
排序方式: 共有576条查询结果,搜索用时 15 毫秒
31.
介绍了用于对微机测控系统输入接口板、输出接口板测试硬件系统的构成,设计了接口卡电路.针对两块电路板,提出了对数字电路板的测试和故障诊断分四个层次,即整板级、功能模块级、单片级和功能输出点级的思想,采取了对功能输出点进行编码的方法建立数字电路板测试的标准知识库,提出了使用功能标志矩阵的方法对各个层次的测试结果进行存储的方法,并根据各个层次测试的关系及相应功能标志矩阵的关系建立了智能化故障诊断程序.  相似文献   
32.
喷管流场和羽流场的N-S数值模拟   总被引:2,自引:0,他引:2       下载免费PDF全文
利用时间推进的方法,通过求解可压缩的、雷诺平均的N-S方程,并利用Baldwin-Lomax两层代数滴流模型和Prandtl混合长度模型,数值模拟了飞机和火箭发动机喷管的内流和羽流,获得了喷管内流场和羽流场的参数分布,计算结果与试验结果及国外研究成果一致。网格划分采和了自适应网格技术。  相似文献   
33.
Studies of nanoindentation were performed on nc-Si:H films to evaluate the effects of the fabrication processes on their mechani-cal properties. It is observed that with the decrease of the SiH4 contents, the grain size of the films increases gradually, and as does the crystalline volume fraction. The smaller the grains become, the more homogeneous the films, and the more even the hardness as well as the modulus will be. The hardness and the modulus will increase with the substrate’s temperature rising. The hardness and the modulus of the nc-Si:H films on the Si substrate prove to be higher than those on the glass substrate given the same technology parameters. How-ever, the films on the glass substrate appear to be more homogeneous.  相似文献   
34.
We will discuss the observed, heavily damped transversal oscillations of coronal loops. These oscillations are often modeled as transversal kink oscillations in a cylinder. Several features are added to the classical cylindrical model. In our models we include loop curvature, longitudinal density stratification, and highly inhomogeneous radial density profiles. In this paper, we will first give an overview of recently obtained results, both analytically and numerically. After that, we shed a light on the computational aspects of the modeling process. In particular, we will focus on the parallellization of the numerical codes.  相似文献   
35.
This paper presents an application of the recent relativistic HLLC approximate Riemann solver by Mignone & Bodo to magnetized flows with vanishing normal component of the magnetic field. The numerical scheme is validated in two dimensions by investigating the propagation of axisymmetric jets with toroidal magnetic fields. The selected jet models show that the HLLC solver yields sharper resolution of contact and shear waves and better convergence properties over the traditional HLL approach.  相似文献   
36.
可拓学及其研究动态   总被引:2,自引:0,他引:2  
文章对可拓学进行了简要的综述和介绍,阐述了可拓学的发展与当前的研究状况,提出了该领域研究中存在的问题,介绍了新的研究进展情况。  相似文献   
37.
Examination of the spatial distribution of CO intensity of Comet Halley indicates that a large fraction of CO originates from the refractory organic component in the coma, rather than directly from the volatiles in the nucleus. Based on the fluffy aggregate interstellar dust comet model, we have estimated the upper limits of the total amount of CO provided by coma dust. The implications from the comparison of the predicted results with the observed value have been discussed. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   
38.
本文介绍了图式理论在阅读理解中的作用。实践表明,图式或背景知识在阅读理解中起着极大的作用。因此,在英语阅读中,教师应该把扩展学生的背景知识放在首位,从而可调动学生的阅读积极性,最终提高学生的阅读理解能力。  相似文献   
39.
Analysis of the Genesis samples is underway. Preliminary elemental abundances based on Genesis sample analyses are in good agreement with in situ-measured elemental abundances made by ACE/SWICS during the Genesis collection period. Comparison of these abundances with those of earlier solar cycles indicates that the solar wind composition is relatively stable between cycles for a given type of flow. ACE/SWICS measurements for the Genesis collection period also show a continuum in compositional variation as a function of velocity for the quasi-stationary flow that defies the simple binning of samples into their sources of coronal hole (CH) and interstream (IS).  相似文献   
40.
Analysis of UV spectra obtained with the HST, FUSE and other satellites provides a new understanding of the deuterium abundance in the local region of the galactic disk. The wide range of gas-phase D/H measurements obtained outside of the Local Bubble can now be explained as due to different amounts of deuterium depletion on carbonaceous grains. The total D/H ratio including deuterium in the gas and dust phases is at least 23 parts per million of hydrogen, which is providing a challenge to models of galactic chemical evolution. Analysis of HST and ground-based spectra of many lines of sight to stars within the Local Bubble have identified interstellar velocity components that are consistent with more than 15 velocity vectors. We have identified the structures of 15 nearby warm interstellar clouds on the basis of these velocity vectors and common temperatures and depletions. We estimate the distances and masses of these clouds and compare their locations with cold interstellar clouds.  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