全文获取类型
收费全文 | 6738篇 |
免费 | 9篇 |
国内免费 | 16篇 |
专业分类
航空 | 3189篇 |
航天技术 | 2274篇 |
综合类 | 24篇 |
航天 | 1276篇 |
出版年
2021年 | 45篇 |
2019年 | 41篇 |
2018年 | 205篇 |
2017年 | 158篇 |
2016年 | 95篇 |
2015年 | 48篇 |
2014年 | 114篇 |
2013年 | 159篇 |
2012年 | 174篇 |
2011年 | 318篇 |
2010年 | 253篇 |
2009年 | 340篇 |
2008年 | 389篇 |
2007年 | 266篇 |
2006年 | 138篇 |
2005年 | 200篇 |
2004年 | 175篇 |
2003年 | 195篇 |
2002年 | 120篇 |
2001年 | 184篇 |
2000年 | 94篇 |
1999年 | 138篇 |
1998年 | 165篇 |
1997年 | 120篇 |
1996年 | 121篇 |
1995年 | 171篇 |
1994年 | 199篇 |
1993年 | 107篇 |
1992年 | 130篇 |
1991年 | 64篇 |
1990年 | 69篇 |
1989年 | 127篇 |
1988年 | 49篇 |
1987年 | 52篇 |
1986年 | 60篇 |
1985年 | 205篇 |
1984年 | 164篇 |
1983年 | 142篇 |
1982年 | 139篇 |
1981年 | 215篇 |
1980年 | 58篇 |
1979年 | 68篇 |
1978年 | 58篇 |
1977年 | 49篇 |
1976年 | 38篇 |
1975年 | 45篇 |
1974年 | 40篇 |
1973年 | 44篇 |
1972年 | 51篇 |
1970年 | 32篇 |
排序方式: 共有6763条查询结果,搜索用时 421 毫秒
501.
502.
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
503.
Ali G. Hafez Essam Ghamry 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
One of global processes in ionosphere–thermosphere–magnetosphere system is the geomagnetic storms. It is of great importance to develop an algorithm that auto-detects sudden commencement because it could be an indicator of onset of the geomagnetic storm. Automatic detection of geomagnetic sudden commencement is based on time–frequency clusters generated by spectrogram. Proposed algorithm is tested on data set collected from stations belong to the international real-time magnetic observatory network (INTERMAGNET). Maximum standard deviation of algorithm detection times is observed to be one minute of the corresponding arrival times published by National Geophysical Data Center (NGDC). 相似文献
504.
K. Patel Ashutosh K. Singh P. Subrahmanyam A.K. Singh 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
The presence and movement of plasma density fluctuations in the F-region of the ionosphere are studied by monitoring phase and amplitude of radio waves propagating through the region. In this paper, we have used weak scattering theory and assumed the plasma density fluctuations to behave like phase changing diffraction screen. Appropriate relations for scintillation index S4, and phase variance δ? are derived and computed for different parameters of the plasma density irregularities of the ionosphere. SROSS-C2 satellite in situ measurements of plasma density fluctuations, which provide direct information about the structure and morphology of irregularities that are responsible for scintillation of radio waves, were used first time to develop a scintillation model for low latitude. It is observed that the scintillation index S4 and phase variance δ? depends on the strength of the plasma turbulence. Finally, the results obtained from modeling are compared and discussed with the available recent results. 相似文献
505.
Pooja Dutt R.K. Sharma 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
A study of the evolution of the periodic and the quasi-periodic orbits near the Lagrangian point L2, which is located to the right of the smaller primary on the line joining the primaries and whose distance from the more massive primary is greater than the distance between the primaries, in the framework of restricted three-body problem for the Sun–Jupiter, Earth–Moon (relatively large mass ratio) and Saturn–Titan (relatively small mass ratio) systems is made. Two families of periodic orbits around the smaller primary are identified using the Poincaré surface of section method – family I (initially elliptical, gradually becomes egg-shaped with the increase in the Jacobi constant C and elongated towards the more massive primary) and family II (initially egg-shaped orbits elongated towards L2 and gradually becomes elliptical with the increase in C). The family I in the Sun–Jupiter and Saturn–Titan systems contains two separatrix caused by third-order and fourth-order resonances, while the Earth–Moon system has only one separatrix which is caused by third-order resonances. Also in the Sun–Jupiter and the Saturn–Titan systems, family I merge with family II, around Jacobian constant 3.0393 and 3.0163, respectively, while in the Earth–Moon system, family II evolves separately from two different branches. The two branches merge at C = 3.184515. In the Earth–Moon system, the family II contains a separatrix due to third-order resonances which is absent in the other two systems. 相似文献
506.
S. O. Karpenko N. V. Kupriyanova M. Yu. Ovchinnikov V. I. Penkov A. S. Selivanov O. E. Khromov 《Cosmic Research》2010,48(6):517-525
The results of designing the attitude control system of the first Russian nanosatellite TNS-0 no. 1 providing orientation of its longitudinal axis along the local geomagnetic field induction vector are presented. The system
consists of a permanent magnet and two sets of hysteresis rods. The magnetic and geometric parameters of the magnet and rods
are calculated. The influence of the permanent magnet field on the hysteresis rods and mutual influence of the rods in the
case of compact satellite packaging are analyzed. Examples of calculations of transient processes and steady-state angular
satellite motion are presented. 相似文献
507.
The problem of determining the “potential” number of integration steps by explicit difference schemes is solved within the framework of the prediction model for chemically non-equilibrium processes. 相似文献
508.
The Juno Waves Investigation 总被引:1,自引:0,他引:1
W. S. Kurth G. B. Hospodarsky D. L. Kirchner B. T. Mokrzycki T. F. Averkamp W. T. Robison C. W. Piker M. Sampl P. Zarka 《Space Science Reviews》2017,213(1-4):347-392
Jupiter is the source of the strongest planetary radio emissions in the solar system. Variations in these emissions are symptomatic of the dynamics of Jupiter’s magnetosphere and some have been directly associated with Jupiter’s auroras. The strongest radio emissions are associated with Io’s interaction with Jupiter’s magnetic field. In addition, plasma waves are thought to play important roles in the acceleration of energetic particles in the magnetosphere, some of which impact Jupiter’s upper atmosphere generating the auroras. Since the exploration of Jupiter’s polar magnetosphere is a major objective of the Juno mission, it is appropriate that a radio and plasma wave investigation is included in Juno’s payload. This paper describes the Waves instrument and the science it is to pursue as part of the Juno mission. 相似文献
509.
The paper discusses a method of designing the neural controller for two-channel control of a technical object by an example of the roll and yaw control depending on deviations, velocities and accelerations of their variation. 相似文献
510.
The methodology is proposed and the mathematical model is developed for the purpose of numerical simulation of the power circuit of the gas-hydraulic actuator with displacing power source for the gimbaled nozzle control. It provides the highest power efficiency factor of the actuator as a part of aircraft by means of pulling together the profiles of available and required power. 相似文献