全文获取类型
收费全文 | 5556篇 |
免费 | 386篇 |
国内免费 | 242篇 |
专业分类
航空 | 2859篇 |
航天技术 | 1814篇 |
综合类 | 217篇 |
航天 | 1294篇 |
出版年
2022年 | 67篇 |
2021年 | 107篇 |
2020年 | 75篇 |
2019年 | 73篇 |
2018年 | 166篇 |
2017年 | 111篇 |
2016年 | 123篇 |
2015年 | 97篇 |
2014年 | 194篇 |
2013年 | 200篇 |
2012年 | 226篇 |
2011年 | 255篇 |
2010年 | 197篇 |
2009年 | 283篇 |
2008年 | 352篇 |
2007年 | 185篇 |
2006年 | 161篇 |
2005年 | 193篇 |
2004年 | 153篇 |
2003年 | 221篇 |
2002年 | 202篇 |
2001年 | 226篇 |
2000年 | 118篇 |
1999年 | 144篇 |
1998年 | 150篇 |
1997年 | 120篇 |
1996年 | 114篇 |
1995年 | 146篇 |
1994年 | 131篇 |
1993年 | 81篇 |
1992年 | 114篇 |
1991年 | 72篇 |
1990年 | 52篇 |
1989年 | 95篇 |
1988年 | 49篇 |
1987年 | 49篇 |
1986年 | 42篇 |
1985年 | 98篇 |
1984年 | 88篇 |
1983年 | 75篇 |
1982年 | 86篇 |
1981年 | 121篇 |
1980年 | 41篇 |
1979年 | 36篇 |
1978年 | 32篇 |
1977年 | 25篇 |
1976年 | 28篇 |
1974年 | 22篇 |
1973年 | 23篇 |
1972年 | 23篇 |
排序方式: 共有6184条查询结果,搜索用时 31 毫秒
1.
2.
3.
Kugusheva A. D. Kalegaev V. V. Vlasova N. A. Petrov K. A. Bazilevskaya G. A. Makhmutov V. S. 《Cosmic Research》2021,59(6):446-455
Cosmic Research - The results of an analysis of the space–time characteristics and dynamics of precipitations of magnetospheric electrons with energies in the range from 0.1 to 0.7 MeV are... 相似文献
4.
The simplest version of the method of detecting the single molecular scattering field based on the polarization measurements of the twilight sky background by all-sky cameras has been considered. The method can be used during transitive twilight (with solar zenith angles of 94°–98°), when effective single scattering occurs in the upper stratosphere and lower mesosphere. The long-term measurements conducted using this method in the Moscow region and Apatity make it possible to determine the temperature of these atmospheric layers and estimate the contribution and properties of multiple scattering during the transitive twilight. 相似文献
5.
A. V. Bogatyi R. V. El’nikov I. P. Nazarenko G. A. Popov S. A. Semenikhin 《Russian Aeronautics (Iz VUZ)》2018,61(3):445-451
The paper presents the research results of the effect of a capacitor energy storage device configuration on the specific characteristics of advanced modern propulsion systems based on the ablative pulsed plasma thrusters (APPT). These thrusters are designed to perform specific tasks within the small spacecrafts with the onboard power capacity up to 200 W. 相似文献
6.
7.
Minakshi Devi S. Patgiri A.K. Barbara Koh-Ichiro Oyama K. Ryu V. Depuev A. Depueva 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(6):1444-1455
The earthquake (EQ) time coupling processes between equator-low-mid latitude ionosphere are complex due to inherent dynamical status of each latitudinal zone and qualified geomagnetic roles working in the system. In an attempt to identify such process, the paper presents temporal and latitudinal variations of ionization density (foF2) covering 45°N to 35°S, during a number of earthquake events (M?>?5.5). The approaches adopted for extraction of features by the earthquake induced preparatory processes are discussed in the paper through identification of parameters like the ‘EQ time modification in density gradient’ defined by δ?=?(foF2 max???foF2 min)∕τmm, where τmm – time span (in days) between EQ modified density maximum and minimum, and the Earthquake time Equatorial Anomaly, i.e. EEA, one of the most significant phenomenon which develops even during night time irrespective of epicenter position. Based on the observations, the paper presents the seismic time coupling dynamics through anomaly like manifestations between equator, low and mid latitude ionosphere bringing in the global Total Electron Content (TEC) features as supporting indices. 相似文献
8.
针对多臂空间机器人自主目标抓捕任务,首先建立多臂空间机器人的运动模型和其与目标的相对运动模型,采用Kane方法建立多臂空间机器人的动力学模型;其次,研究基于视觉伺服的机械臂在线轨迹规划算法,并引入零反作用机动,消除机械臂运动对平台姿态的扰动;再次,在不使用零反作用机动功能时,分别使用基于角动量前馈补偿的协调控制算法和逆动力学方法设计了协调控制器,在机械臂运动时保持平台姿态和相对目标的位置。最后,开发了基于Matlab的仿真软件MASS(多臂空间机器人仿真),仿真结果校验了上述方法的有效性。 相似文献
9.
10.
The Role and Contributions of Energetic Neutral Atom (ENA) Imaging in Magnetospheric Substorm Research 总被引:2,自引:0,他引:2
Pollock C.J. C:son-Brandt P. Burch J.L. Henderson M.G. Jahn J.-M. McComas D.J. Mende S.B. Mitchell D.G. Reeves G.D. Scime E.E. Skoug R.M. Thomsen M. Valek P. 《Space Science Reviews》2003,109(1-4):155-182
Energetic Neutral Atom (ENA) imaging has contributed substantially to substorm research. This technique has allowed significant advances in areas such as observation and quantification of injected particle drift as a function of energy, observation of dynamics in the tail that are directly related to the effects of imposed (growth phase) and induced (expansion phase) electric fields on the plasma, the prompt extraction of oxygen from the ionosphere during substorms, the relationship between storms and substorms, and the timing of substorm ENA signatures. We present discussion of the advantages and shortcomings of the ENA technique for studying space plasmas. Although the technique is in its infancy, it is yielding results that enrich our understanding of the substorm process and its effects. 相似文献