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   855篇
  免费   87篇
  国内免费   51篇
航空   433篇
航天技术   123篇
综合类   90篇
航天   347篇
  2024年   5篇
  2023年   8篇
  2022年   21篇
  2021年   18篇
  2020年   17篇
  2019年   18篇
  2018年   25篇
  2017年   16篇
  2016年   16篇
  2015年   11篇
  2014年   36篇
  2013年   28篇
  2012年   24篇
  2011年   26篇
  2010年   28篇
  2009年   43篇
  2008年   54篇
  2007年   40篇
  2006年   37篇
  2005年   37篇
  2004年   30篇
  2003年   28篇
  2002年   29篇
  2001年   31篇
  2000年   33篇
  1999年   34篇
  1998年   33篇
  1997年   26篇
  1996年   16篇
  1995年   30篇
  1994年   28篇
  1993年   17篇
  1992年   25篇
  1991年   27篇
  1990年   10篇
  1989年   7篇
  1988年   9篇
  1987年   15篇
  1986年   6篇
  1985年   17篇
  1984年   7篇
  1983年   11篇
  1982年   4篇
  1981年   5篇
  1980年   4篇
  1979年   1篇
  1978年   1篇
  1975年   1篇
排序方式: 共有993条查询结果,搜索用时 78 毫秒
901.
本文介绍了一种新型的VLSI单片处理机,并通过实例讨论了用Transputer构成的多处理机系统在连续系统并行仿真中的应用。  相似文献   
902.
随着固体火箭尺寸的增大及推进剂能量的提高,使用连续混合工艺制造推进剂有可能降低由混合机尺寸所引起的危险,同时提高了生产率。另一方面,连续混合工艺亦象其它连续化学工艺一样可以节省开支。由于固体推进剂是结构材料和弹道的产物,其机械性能和弹道性能的重现性是很重要的。本文论述了如下问题:  相似文献   
903.
MW  Barclay  NK  Williams  罗先志 《空载雷达》2005,(4):25-30
海上监视对高分辨率雷达成像模式特别感兴趣。在海上监视应用中,可以使用高分辨率雷达成像模式来支持对已经用传统搜索功能和跟踪功能检测到的海面目标的分类和可能的识别。  相似文献   
904.
抖动式激光陀螺零速率点误差分析   总被引:5,自引:1,他引:5  
杜建邦 《宇航学报》2000,21(3):58-63
分析了抖动式激光陀螺经过零速率点引起的误差特征。根据此误差特征,系统地推导出该误差与陀螺参数的关系并进行了必要的讨论。  相似文献   
905.
本文对洛克达因公司在研究可重复使用火箭的鉴定试验期间,航天飞机主发动机偏离额定工况工作的分析和论证进行了描述。航天飞机主发动机(SSME)额定推力的范围是:设计推力的65%到109%,扩大论证的范围是:设计推力的17%、22%、27%、40%、45%和50%。在低推力工作期间,额外的收获包括:高压氧化剂涡轮泵(HPOTP)使用液体静压轴承,高压燃料涡轮泵(HPFTP)在第一临界转速下运转,在低工况工作的燃烧稳定性以及喷管流动分离热负荷的改善。  相似文献   
906.
Coupled radiative-convective/photochemical modeling was performed for Earth-like planets orbiting different types of stars (the Sun as a G2V, an F2V, and a K2V star). O(2) concentrations between 1 and 10(-5) times the present atmospheric level (PAL) were simulated. The results were used to calculate visible/near-IR and thermal-IR spectra, along with surface UV fluxes and relative dose rates for erythema and DNA damage. For the spectral resolution and sensitivity currently planned for the first generation of terrestrial planet detection and characterization missions, we find that O(2) should be observable remotely in the visible for atmospheres containing at least 10(-2) PAL of O(2). O(3) should be visible in the thermal-IR for atmospheres containing at least 10(-3) PAL of O(2). CH(4) is not expected to be observable in 1 PAL O(2) atmospheres like that of modern Earth, but it might be observable at thermal-IR wavelengths in "mid-Proterozoic-type" atmospheres containing approximately 10(-1) PAL of O(2). Thus, the simultaneous detection of both O(3) and CH(4) - considered to be a reliable indication of life - is within the realm of possibility. High-O(2) planets orbiting K2V and F2V stars are both better protected from surface UV radiation than is modern Earth. For the F2V case the high intrinsic UV luminosity of the star is more than offset by the much thicker ozone layer. At O(2) levels below approximately 10(-2) PAL, planets around all three types of stars are subject to high surface UV fluxes, with the F2V planet exhibiting the most biologically dangerous radiation environment. Thus, while advanced life is theoretically possible on high-O(2) planets around F stars, it is not obvious that it would evolve as it did on Earth.  相似文献   
907.
本文提出了软件接收机中调频信号解调的一种算法,文章最后给出了一个具体实例的仿真结果。  相似文献   
908.
The volume of regulating hormones (renin, aldosterone, arginine vasopressin and atrial natriuretic factor), electrolytes and creatinine concentrations, and blood pressure were measured in two different four-week experimental protocols: respectively -6 degrees head-down bed-rest (5 subjects) and confinement (6 subjects). We observed a significant increase (P < 0.01 at D2 vs D-5) of systolic blood pressure during confinement and a different level of response for some hormones, especially for arginine vasopressin (300% increase during confinement instead of 50% during bed-rest). The renin-angiotensin-aldosterone system was enhanced during confinement and head-down bed-rest. In both conditions, we obtained a similar pattern of response for blood volume regulating hormones. During confinement, two main factors were inactivity and stress activation of the sympathetic nervous system. In the bed-rest study the response is principally due to the fluid shift and blood volume adaptation but it is not possible to exclude the role of inactivity and stress.  相似文献   
909.
Thermoluminescent (TL) detectors were used for dosimetric investigations on the outer surface as well as inside Soviet spacecrafts of the "Cosmos" series. At the outer surface, ultrathin TL detectors, based on CaF2-PTFE and LiF, were arranged in special stacks and exposed to unshielded cosmic radiation. The strong decrease of dose within a few mg/cm2 demonstrates that weakly penetrating radiation is dominating in the radiation field under investigation. On the basis of glow curve analysis of LiF thermoluminescent detectors it could be shown, that the high doses are caused by electrons.  相似文献   
910.
Recognizing the importance of the telescience technology for the efficient and improved space environment utilization in JEM, we have undertaken telescience technology development since 1987. The purpose of this paper is to introduce the recent status of our telescience activity, the results of the testbed experiments in these years, and the new activities for the initial JEM operation and its future utilization.  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