全文获取类型
收费全文 | 6519篇 |
免费 | 9篇 |
国内免费 | 18篇 |
专业分类
航空 | 3486篇 |
航天技术 | 1928篇 |
综合类 | 23篇 |
航天 | 1109篇 |
出版年
2018年 | 200篇 |
2017年 | 157篇 |
2016年 | 64篇 |
2015年 | 39篇 |
2014年 | 84篇 |
2013年 | 135篇 |
2012年 | 149篇 |
2011年 | 293篇 |
2010年 | 240篇 |
2009年 | 308篇 |
2008年 | 339篇 |
2007年 | 274篇 |
2006年 | 143篇 |
2005年 | 197篇 |
2004年 | 130篇 |
2003年 | 172篇 |
2002年 | 103篇 |
2001年 | 181篇 |
2000年 | 110篇 |
1999年 | 140篇 |
1998年 | 164篇 |
1997年 | 123篇 |
1996年 | 171篇 |
1995年 | 215篇 |
1994年 | 183篇 |
1993年 | 124篇 |
1992年 | 128篇 |
1991年 | 76篇 |
1990年 | 62篇 |
1989年 | 139篇 |
1988年 | 62篇 |
1987年 | 66篇 |
1986年 | 60篇 |
1985年 | 196篇 |
1984年 | 152篇 |
1983年 | 130篇 |
1982年 | 134篇 |
1981年 | 176篇 |
1980年 | 58篇 |
1979年 | 42篇 |
1978年 | 50篇 |
1977年 | 53篇 |
1976年 | 38篇 |
1975年 | 58篇 |
1974年 | 38篇 |
1973年 | 42篇 |
1972年 | 51篇 |
1971年 | 42篇 |
1970年 | 44篇 |
1969年 | 37篇 |
排序方式: 共有6546条查询结果,搜索用时 15 毫秒
301.
In this paper, we consider an example of estimating and comparing the efficiency of different concepts for a high-altitude unmanned aerial vehicle (UAV) under diversity of efficiency criteria. 相似文献
302.
B. A. Antuf’ev 《Russian Aeronautics (Iz VUZ)》2016,59(3):303-307
This study proposes an approximate solution to a contact problem of dynamic deformation of a cyclically symmetrical discretely ring-stiffened cylindrical shell, the side surface of which is subjected to an evenly distributed inertia live load. The solution of the problem assumes the quasistatic mode of deformation of the structure. Several critical velocities of the live load have been found. A number of examples are presented. 相似文献
303.
A novel modular multistep algorithm is proposed for multi-criteria analysis of fracture of aircraft structures with complex geometries. In order to evaluate the algorithm, the crack growth analysis is realized by the following three criteria, namely, the stress intensity factor, the strain energy release rate, and the J-integral. The algorithm implementation by the finite element method is considered and prospects of alternative implementation based on the meshfree methods are assigned. 相似文献
304.
The vortical mixing concept in the ramjet channel is analyzed. The results of simulating the gasodynamic scheme permit the concept of increasing efficiency for ramjet operation to be substantiated. 相似文献
305.
Drag reducing and increasing mechanism on riblet surface has been studied through computational fluid dynamics(CFD).Drag reduction is achieved through the optimization of riblet geometry which would affect flow structure inside riblet grooves.Force and flow structure on riblet surface are analyzed and compared with those of smooth surface based on the k-εturbulence model.Drag reducing and increasing mechanism is proved to be related to microvortexes induced inside riblets which lead to Reynolds shear stress reduction significantly and is considered to be the dominant factor resulting in wall friction reduction.Simulation results also show that the pressure drag generating from the deviation of static pressure on the front and rear ends of riblets occurs and grows exponentially with Mach number,which can cause drag increasing.Furthermore,near-wall vortical structures,Reynolds shear stress and static pressure on riblet surfaces are also analyzed in detail. 相似文献
306.
Very Long Baseline Interferometry (VLBI) is a differential technique observing radiation of compact extra-galactic radio sources with pairs of radio telescopes. For these observations, the frequency standards at the telescopes need to have very high stability. In this article we discuss why this is, and we investigate exactly how precise the frequency standards need to be. Four areas where good clock performance is needed are considered: coherence, geodetic parameter estimation, correlator synchronization, and UT1 determination. We show that in order to ensure the highest accuracy of VLBI, stability similar to that of a hydrogen maser is needed for time-scales up to a few hours. In the article, we are considering both traditional VLBI where extra-galactic radio sources are observed, as well as observation of man-made artificial radio sources emitted by satellites or spacecrafts. 相似文献
307.
P. V. Bulat M. P. Bulat I. A. Volobuev A. A. Levikhin 《Russian Aeronautics (Iz VUZ)》2018,61(3):420-424
The bearing capacity of hybrid segmented bearings with different groove systems is compared. The research establishes that the system with a crescent groove has the best characteristics. 相似文献
308.
The DB-8 detectors of the ISS radiation monitoring system (RMS) have operated almost continuously onboard the ISS service module since August 2001 till December 2014. The RMS data obtained were used for the daily monitoring of the radiation environment aboard the station. This paper considers the technique of RMS data analysis that allows one to distinguish the contributions of galactic cosmic rays and the Earth’s inner radiation belt to the daily dose based on the dosimetry data obtained as a result of the station’s passage in areas of the highest geomagnetic latitudes. The paper presents the results of an analysis of the dosimetry data based on this technique for 2005–2011, as well as a comparison with similar results the authors obtained previously using the technique based on an analysis of the dosimetry data obtained during station passages in the area of the South Atlantic Anomaly. 相似文献
309.
310.