全文获取类型
收费全文 | 5273篇 |
免费 | 9篇 |
国内免费 | 11篇 |
专业分类
航空 | 2257篇 |
航天技术 | 1864篇 |
综合类 | 23篇 |
航天 | 1149篇 |
出版年
2022年 | 17篇 |
2021年 | 47篇 |
2019年 | 28篇 |
2018年 | 150篇 |
2017年 | 120篇 |
2016年 | 127篇 |
2015年 | 50篇 |
2014年 | 148篇 |
2013年 | 176篇 |
2012年 | 157篇 |
2011年 | 225篇 |
2010年 | 175篇 |
2009年 | 281篇 |
2008年 | 300篇 |
2007年 | 169篇 |
2006年 | 110篇 |
2005年 | 144篇 |
2004年 | 147篇 |
2003年 | 184篇 |
2002年 | 119篇 |
2001年 | 202篇 |
2000年 | 80篇 |
1999年 | 134篇 |
1998年 | 137篇 |
1997年 | 94篇 |
1996年 | 101篇 |
1995年 | 158篇 |
1994年 | 151篇 |
1993年 | 69篇 |
1992年 | 94篇 |
1991年 | 30篇 |
1990年 | 45篇 |
1989年 | 90篇 |
1988年 | 31篇 |
1987年 | 52篇 |
1986年 | 33篇 |
1985年 | 132篇 |
1984年 | 92篇 |
1983年 | 86篇 |
1982年 | 92篇 |
1981年 | 145篇 |
1980年 | 49篇 |
1979年 | 39篇 |
1978年 | 35篇 |
1977年 | 32篇 |
1976年 | 28篇 |
1975年 | 31篇 |
1974年 | 23篇 |
1972年 | 29篇 |
1969年 | 18篇 |
排序方式: 共有5293条查询结果,搜索用时 140 毫秒
951.
V.V. Kalegaev I.I. Alexeev I.S. Nazarkov V. Angelopoulos A. Runov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
The magnetic field structure and the spatial characteristics of the large-scale currents in the magnetospheric tail were studied during quiet and moderately disturbed geomagnetic conditions in 2009. The magnetic field of the currents other than the tail current was calculated in terms of a paraboloid model of the Earth’s magnetosphere, A2000, and was subtracted from measurements. It was found on the base of obtained tail current magnetic field radial distribution that the inner edge of the tail current sheet is located in the night side magnetosphere, at distances of about 10 RE and of about 7 RE during quiet and disturbed periods respectively. During the disturbance of February 14, 2009 (Dstmin ∼ −35 nT), the Bx and the Bz component of the tail current magnetic field near its inner edge were about 60 nT, and −60 nT that means that strong cross-tail current have been developed. The tail current parameters at different time moments during February 14, 2009 have been estimated. Solar wind conditions during this event were consistent with those during moderate magnetic storms with minimum Dst of about −100 nT. However, the magnetospheric current systems (magnetopause and cross-tail currents) were located at larger geocentric distances than typical during the 2009 extremely quiet epoch and did not provide the expected Dst magnitude. Very small disturbance on the Earth’s surface was detected consistent with an “inflated” magnetosphere. 相似文献
952.
Zama T. Katamzi John Bosco Habarulema 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
This paper presents traveling ionospheric disturbances (TIDs) observations from GPS measurements over the South African region during the geomagnetically disturbed period of 29–31 October 2003. Two receiver arrays, which were along two distinct longitudinal sectors of about 18°-20° and 27°-28° were used in order to investigate the amplitude, periods and virtual propagation characteristics of the storm induced ionospheric disturbances. The study revealed a large sudden TEC increase on 28 October 2003, the day before the first of the two major storms studied here, that was recorded simultaneously by all the receivers used. This pre-storm enhancement was linked to an X-class solar flare, auroral/magnetospheric activities and vertical plasma drift, based on the behaviour of the geomagnetic storm and auroral indices as well as strong equatorial electrojet. Diurnal trends of the TEC and foF2 measurements revealed that the geomagnetic storm caused a negative ionospheric storm; these parameters were depleted between 29 and 31 October 2003. Large scale traveling ionospheric disturbances were observed on the days of the geomagnetic storms (29 and 31 October 2003), using line-of-sight vertical TEC (vTEC) measurements from individual satellites. Amplitude and dominant periods of these structures varied between 0.08–2.16 TECU, and 1.07–2.13 h respectively. The wave structures were observed to propagate towards the equator with velocities between 587.04 and 1635.09 m/s. 相似文献
953.
I.L. Babich V.F. BoretskijA.N. Veklich R.V. Semenyshyn 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
Optical emission and linear laser absorption spectroscopy techniques were used in investigation of plasma with copper and silver admixture. The method of selection of spectral lines and spectroscopic data with the aim of diagnostics of multicomponent air plasma with two metal vapors admixture was developed. Energy level populations behavior on the Boltzmann plot were used for Cu I and Ag I spectroscopic data selection. In this way the selection of spectroscopic data for some of Cu I and Ag I lines was realized. Stark broadening parameters of Cu I and Ag I were examined. Experimentally obtained temperature and electron density radial distributions were used in the calculation of plasma composition in the assumption of local thermodynamic equilibrium. Linear laser absorption spectroscopy was used to examine the state of plasma. 相似文献
954.
F.J.T. Salazar E.E.N. Macau O.C. Winter 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
Lagrangian points L4 and L5 lie at 60° ahead of and behind the Moon in its orbit with respect to the Earth. Each one of them is a third point of an equilateral triangle with the base of the line defined by those two bodies. These Lagrangian points are stable for the Earth–Moon mass ratio. As so, these Lagrangian points represent remarkable positions to host astronomical observatories or space stations. However, this same distance characteristic may be a challenge for periodic servicing mission. This paper studies elliptic trajectories from an Earth circular parking orbit to reach the Moon’s sphere of influence and apply a swing-by maneuver in order to re-direct the path of a spacecraft to a vicinity of the Lagrangian points L4 and L5. Once the geocentric transfer orbit and the initial impulsive thrust have been determined, the goal is to establish the angle at which the geocentric trajectory crosses the lunar sphere of influence in such a way that when the spacecraft leaves the Moon’s gravitational field, its trajectory and velocity with respect to the Earth change in order to the spacecraft arrives at L4 and L5. In this work, the planar Circular Restricted Three Body Problem approximation is used and in order to avoid solving a two boundary problem, the patched-conic approximation is considered. 相似文献
955.
Chae Kyung Sim Huynh Anh Nguyen Le Soojong Pak Hye-In Lee Wonseok Kang Moo-Young Chun Ueejeong Jeong In-Soo Yuk Kang-Min Kim Chan Park Michael D. Pavel Daniel T. Jaffe 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
We present a Python-based data reduction pipeline package (PLP) for the Immersion GRating INfrared Spectrograph (IGRINS), an instrument that covers the complete H- and K-bands in one exposure with a spectral resolving power of 40,000. The reduction steps carried out by the PLP include flat-fielding, background removal, order extraction, distortion correction, wavelength calibration, and telluric correction using spectra of A type standard stars. As the spectrograph has no moving parts, the PLP automatically reduces the data using predefined functions for the processes of order extraction, distortion correction, and wavelength calibration. Before the telluric correction of the target spectra, the intrinsic hydrogen absorption features of the standard A star are removed with a Gaussian fitting algorithm. The final result is the flux of the target as a function of wavelength. Users can customize the predefined functions for the extraction of the spectrum from the echellogram and adjust the parameters for the fitting functions for the spectra of celestial objects, using “fine-tuning” options, as necessary. Presently, the PLP produces the best results for point-source targets. 相似文献
956.
以2004年9月28日02:53:20 UT的亚暴为例, 通过TC-1在磁尾约12.5 Re 和Geotail卫星在近地磁尾等离子体片约8~9 Re的联合观测, 研究亚暴触发过程中近地磁尾等离子体片中等离子体波动特征. 结果表明, 亚暴触发区是近地磁尾中心等离子体片中较小的一个区域, 在亚暴触发区中低混杂不稳定性在近地磁尾等离子体片中存在, 准垂直传播的低混杂波发生在亚暴触发过程中, 而亚暴触发过程中近地磁尾等离子体片外边界区内的磁场偶极化信号和扰动都非常微弱. 在亚暴触发和亚暴膨胀相过程中出现了多次具有不同特征的磁场偶极化现象. 相似文献
957.
V. A. Komkov V. V. Vasilevskii V. F. Korolev Yu. V. Mozgovoi 《Russian Aeronautics (Iz VUZ)》2012,55(2):217-222
In this paper, a research and development version of the computer-aided system of mass tensometry (SMT) for conduction of aircraft and rocket-space equipment vibration tests is considered. A technique of the system design and development that combines the advantages of the system and process approaches when using the modern element base around the high-performance integral microcircuits is a distinctive feature in this research and development problem solution. We describe the architecture and structure of the advanced computer-aided SMTs and present data on its basic components desigtn. Also determined are the list and functional parameters of ratio-measuring network modules as well as the scheme of their connection to the test object and the local computer network of the enterprise. 相似文献
958.
An urgent problem of organizing the on-line monitoring of large territories using the information unmanned aerial systems (UAS) is considered. We determine the UAS placement and their necessary number by solving a two-criteria problem on rational covering of the territory by these systems. A man-machine algorithm and an example of the problem solution are presented. 相似文献
959.
960.
S. A. Mikhailov T. A. Mukhametshin D. V. Nedel’ko A. V. Dvoryankin 《Russian Aeronautics (Iz VUZ)》2012,55(4):353-356
The methodical grounds for helicopter operation with respect to the technical condition for the state of the art of aeronautical engineering are analyzed and generalized. The most essential engineering solutions on developing the systems for monitoring the helicopter operating conditions are considered. The promising lines for further development of these systems are designated. 相似文献