全文获取类型
收费全文 | 6963篇 |
免费 | 14篇 |
国内免费 | 22篇 |
专业分类
航空 | 3515篇 |
航天技术 | 2472篇 |
综合类 | 29篇 |
航天 | 983篇 |
出版年
2019年 | 43篇 |
2018年 | 96篇 |
2017年 | 52篇 |
2016年 | 49篇 |
2014年 | 120篇 |
2013年 | 187篇 |
2012年 | 143篇 |
2011年 | 212篇 |
2010年 | 162篇 |
2009年 | 259篇 |
2008年 | 325篇 |
2007年 | 166篇 |
2006年 | 177篇 |
2005年 | 179篇 |
2004年 | 155篇 |
2003年 | 215篇 |
2002年 | 125篇 |
2001年 | 240篇 |
2000年 | 134篇 |
1999年 | 176篇 |
1998年 | 204篇 |
1997年 | 156篇 |
1996年 | 207篇 |
1995年 | 249篇 |
1994年 | 235篇 |
1993年 | 145篇 |
1992年 | 153篇 |
1991年 | 85篇 |
1990年 | 78篇 |
1989年 | 163篇 |
1988年 | 81篇 |
1987年 | 79篇 |
1986年 | 83篇 |
1985年 | 243篇 |
1984年 | 197篇 |
1983年 | 157篇 |
1982年 | 181篇 |
1981年 | 217篇 |
1980年 | 69篇 |
1979年 | 49篇 |
1978年 | 69篇 |
1977年 | 58篇 |
1976年 | 43篇 |
1975年 | 76篇 |
1974年 | 50篇 |
1973年 | 51篇 |
1972年 | 62篇 |
1971年 | 50篇 |
1970年 | 52篇 |
1969年 | 44篇 |
排序方式: 共有6999条查询结果,搜索用时 15 毫秒
101.
102.
L. G. Blomberg J. A. Cumnock 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2004,33(12):2161-2165
Mercury has a small but intriguing magnetosphere. In this brief review, we discuss some similarities and differences between Mercury’s and Earth’s magnetospheres. In particular, we discuss how electric and magnetic field measurements can be used as a diagnostic tool to improve our understanding of the dynamics of Mercury’s magnetosphere. These points are of interest to the upcoming ESA-JAXA BepiColombo mission to Mercury. 相似文献
103.
A method is discussed for generating Weibull vectors with a desired correlation matrix and specified parameters. Such vectors may represent samples of a correlated clutter signal. The presented method makes use of a suitable nonlinear transformation of random Gaussian vectors with correlated components. Computational aspects of the method are also discussed. 相似文献
104.
Summary The observational features of the arc are fairly well established. At present, the thermal conduction model appears to explain the red arc features most consistently, but it must be noted that a soft electron flux would give very similar results. Ion temperature measurements in the vicinity of an arc, which should be forthcoming in the very near future, can establish conclusively whether transverse electric fields play any important role in the formation of the arcs. Accepting the assumption that the arcs are the result of energy flowing down from the plasmasphere, the major remaining question is: where does the energy come from and how does it get into the plasmasphere? The various proposed mechanisms discussed in the previous chapter appear feasible, but much work needs to be done before this problem is completely resolved.On leave from the Department of Electrical Engineering, The University of Michigan, Ann Arbor.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
105.
Kau S. Kumar K.S.P. Granley G.B. 《IEEE transactions on aerospace and electronic systems》1969,(6):906-911
The theory of nonlinear filtering has been applied to the problem of the attitude determination of a satellite. Two approximation methods have been studied with a view to practical implementation. Computer simulation results are included. 相似文献
106.
The Electric Antennas for the STEREO/WAVES Experiment 总被引:1,自引:0,他引:1
S. D. Bale R. Ullrich K. Goetz N. Alster B. Cecconi M. Dekkali N. R. Lingner W. Macher R. E. Manning J. McCauley S. J. Monson T. H. Oswald M. Pulupa 《Space Science Reviews》2008,136(1-4):529-547
The STEREO/WAVES experiment is designed to measure the electric component of radio emission from interplanetary radio bursts and in situ plasma waves and fluctuations in the solar wind. Interplanetary radio bursts are generated from electron beams at interplanetary shocks and solar flares and are observed from near the Sun to 1 AU, corresponding to frequencies of approximately 16 MHz to 10 kHz. In situ plasma waves occur in a range of wavelengths larger than the Debye length in the solar wind plasma λ D ≈10 m and appear Doppler-shifted into the frequency regime down to a fraction of a Hertz. These phenomena are measured by STEREO/WAVES with a set of three orthogonal electric monopole antennas. This paper describes the electrical and mechanical design of the antenna system and discusses efforts to model the antenna pattern and response and methods for in-flight calibration. 相似文献
107.
将基因方法应用于网格结点位置的优化中。文中首先简单介绍了基因优化方法中基于达尔文进化论和Mendel基因理论的基本原理,其中包括插索空间表达、三个基因作用器(选择、交配和变异)等要点;然后着重阐述了相关偏微分方程的离散误差和三角形网格几何形状的适应度函数的定义、结点位置的二进制基因表达及基因方法的优化进程。离散误差是在二次非连续彭鼓包(bump)函数的空间中近似定义的,并且在点移动过程中相关解的二 相似文献
108.
109.
J. L. Birck 《Space Science Reviews》1991,56(1-2):141-146
According to their chemical composition, rich in volatile compounds, comets are thought to be primitive materials. They may provide prime samples for the study of nucleosynthetic components of the solar system and of the processes occurring during the formation of the outer planets. Their origin is largely a matter of conjecture. Chromium isotopic measurements in carbonaceous chondrites illustrate how the non-volatile part of cometary material can be investigated both for isotopic heterogeneity and for the extinct nuclide 53Mn. Questions like the possible presence of 26Al as a heat source can also be addressed by these measurements. 相似文献
110.
S. Hayakawa J. Kuijpers J. Kleczek Boris Valnicek L. Kresak H. R. De Ruiter 《Space Science Reviews》1991,57(1-2):189-192