全文获取类型
收费全文 | 6056篇 |
免费 | 30篇 |
国内免费 | 9篇 |
专业分类
航空 | 2727篇 |
航天技术 | 2013篇 |
综合类 | 29篇 |
航天 | 1326篇 |
出版年
2021年 | 59篇 |
2019年 | 39篇 |
2018年 | 161篇 |
2017年 | 127篇 |
2016年 | 133篇 |
2015年 | 57篇 |
2014年 | 152篇 |
2013年 | 189篇 |
2012年 | 179篇 |
2011年 | 244篇 |
2010年 | 199篇 |
2009年 | 290篇 |
2008年 | 321篇 |
2007年 | 185篇 |
2006年 | 135篇 |
2005年 | 175篇 |
2004年 | 162篇 |
2003年 | 199篇 |
2002年 | 139篇 |
2001年 | 217篇 |
2000年 | 103篇 |
1999年 | 120篇 |
1998年 | 152篇 |
1997年 | 105篇 |
1996年 | 131篇 |
1995年 | 195篇 |
1994年 | 155篇 |
1993年 | 84篇 |
1992年 | 122篇 |
1991年 | 42篇 |
1990年 | 57篇 |
1989年 | 121篇 |
1988年 | 50篇 |
1987年 | 48篇 |
1986年 | 48篇 |
1985年 | 159篇 |
1984年 | 141篇 |
1983年 | 123篇 |
1982年 | 117篇 |
1981年 | 158篇 |
1980年 | 47篇 |
1979年 | 43篇 |
1978年 | 41篇 |
1977年 | 40篇 |
1976年 | 30篇 |
1975年 | 47篇 |
1974年 | 33篇 |
1973年 | 23篇 |
1972年 | 43篇 |
1971年 | 28篇 |
排序方式: 共有6095条查询结果,搜索用时 15 毫秒
341.
Ramachandra K.V. Division R.C. 《IEEE transactions on aerospace and electronic systems》1987,(5):705-708
A one-dimensional tracking filter based on the Kalman filtering techniques for tracking of a dynamic target such as an aircraft is discussed. The target is assumed to be moving with constant acceleration and is acted upon by a plant noise which perturbs its constant acceleration motion. The plant noise accounts for maneuvers and/or other random factors. Analytical results for estimating optimum steady state position, velocity, and acceleration of the target are obtained. 相似文献
342.
This paper presents a theoretically and practically grounded architecture of design methods combination. A possibility and completeness of developing integral design solutions and intensifying the design process are provided by redistribution of emphases of numerical and natural experiments. 相似文献
343.
344.
Computerized Model Demonstrating Magnetic Submarine Localization 总被引:1,自引:0,他引:1
A modet is described which consists of an aircraft with flux gate magnetometers mounted on the wing tips and a submarine containing a magnet to simulate the induced and permanent fields of an actual submarine. Equations are developed which enable a minicomputer sampling the magnetometers to calculate the location, depth, and heading of the submarine as the aircraft travels towards it. The real time plotted results are presented. 相似文献
345.
A technique of optimizing the electrode system of the differential recorder for the aircraft time-of-flight ion-marking airspeed and aircraft angle of attack sensor by the criterion of ion-marking recording error variance minimum is considered. The technique is based on analyzing the function of spatial distribution for the ion-marking and recorder electrode interaction field potential and determining a point for which this function reaches the maximum slope. The relations making it possible to synthesize the sensor electrode system by the complex criterion as a ratio of error variance to transformation channel response are obtained. 相似文献
346.
We present our measurements of the deuterium to hydrogen ratio (D/H) in QSO absorption systems, which give D/H = 3.40 ± 0.25 × 10-5 based on analysis of four independent systems. We discuss the properties of two systems which provide the strongest constraints on D/H. We outline the systematic effects involved in measurements of D/H and introduce a sophisticated method of analysis which properly accounts for these effects. 相似文献
347.
V. A. Ovchinnikov 《Russian Aeronautics (Iz VUZ)》2007,50(2):146-149
We analyze the effect of injection both of uniformly distributed over the entire cylinder surface and of the optimal one on the velocity distribution at the outer border of the boundary layer and, as a result, on friction. 相似文献
348.
A. I. Belousov S. V. Falaleev A. S. Vinogradov P. V. Bondarchuk 《Russian Aeronautics (Iz VUZ)》2007,50(4):390-394
Problems arising in introduction of gasodynamic seals in aircraft engines are considered. The operation of a face gasodynamic seal as part of a natural gas pump is analyzed and its efficiency in the presence of oil is shown. 相似文献
349.
This paper considers the axisymmetric transverse vibrations of aircraft nonuniform structural elements that are introduced by a thermal shock. Analytical solutions have been obtained and their numerical analysis has been performed. 相似文献
350.
Examples of solar microwave precursors and estimates of their energetic characteristics are discussed based on spectral investigations of the preflare activity. 相似文献