全文获取类型
收费全文 | 4272篇 |
免费 | 13篇 |
国内免费 | 16篇 |
专业分类
航空 | 1860篇 |
航天技术 | 1476篇 |
综合类 | 17篇 |
航天 | 948篇 |
出版年
2021年 | 39篇 |
2019年 | 17篇 |
2018年 | 147篇 |
2017年 | 99篇 |
2016年 | 73篇 |
2015年 | 29篇 |
2014年 | 110篇 |
2013年 | 117篇 |
2012年 | 106篇 |
2011年 | 197篇 |
2010年 | 136篇 |
2009年 | 206篇 |
2008年 | 230篇 |
2007年 | 130篇 |
2006年 | 85篇 |
2005年 | 121篇 |
2004年 | 133篇 |
2003年 | 148篇 |
2002年 | 82篇 |
2001年 | 142篇 |
2000年 | 72篇 |
1999年 | 81篇 |
1998年 | 101篇 |
1997年 | 73篇 |
1996年 | 108篇 |
1995年 | 117篇 |
1994年 | 85篇 |
1993年 | 67篇 |
1992年 | 95篇 |
1991年 | 36篇 |
1990年 | 30篇 |
1989年 | 79篇 |
1988年 | 35篇 |
1987年 | 38篇 |
1986年 | 40篇 |
1985年 | 136篇 |
1984年 | 87篇 |
1983年 | 75篇 |
1982年 | 93篇 |
1981年 | 130篇 |
1980年 | 34篇 |
1979年 | 31篇 |
1978年 | 32篇 |
1977年 | 37篇 |
1976年 | 27篇 |
1975年 | 32篇 |
1974年 | 34篇 |
1973年 | 19篇 |
1970年 | 22篇 |
1969年 | 21篇 |
排序方式: 共有4301条查询结果,搜索用时 15 毫秒
451.
452.
V. A. Sadovnichiy A. M. Amelyushkin V. Angelopoulos V. V. Bengin V. V. Bogomolov G. K. Garipov E. S. Gorbovskoy B. Grossan P. A. Klimov B. A. Khrenov J. Lee V. M. Lipunov G. W. Na M. I. Panasyuk I. H. Park V. L. Petrov C. T. Russell S. I. Svertilov E. A. Sigaeva G. F. Smoot Yu. Shprits N. N. Vedenkin I. V. Yashin 《Cosmic Research》2013,51(6):427-433
At present, the Institute of Nuclear Physics of Moscow State University, in cooperation with other organizations, is preparing space experiments onboard the Lomonosov satellite. The main goal of this mission is to study extreme astrophysical phenomena such as cosmic gamma-ray bursts and ultra-high-energy cosmic rays. These phenomena are associated with the processes occurring in the early universe in very distant astrophysical objects, therefore, they can provide information on the first stages of the evolution of the universe. This paper considers the main characteristics of the scientific equipment aboard the Lomonosov satellite. 相似文献
453.
454.
A. I. Efimov L. A. Lukanina V. K. Rudash L. N. Samoznaev I. V. Chashei M. K. Bird M. Pätzold 《Cosmic Research》2013,51(1):13-22
We have performed spectral processing of the data of experiments on radio sounding of circumsolar plasma by coherent S- and X-band signals from the spacecraft Ulysses, Mars Express, Rosetta, and Venus Express carried out from 1991 to 2009. The experiments were realized in the mode of coherent response, when a signal stabilized by the hydrogen standard is transmitted from the ground station to a spacecraft, received by the onboard systems, and retransmitted to the Earth with conserved coherence. Thus, the signal sounding the coronal plasma passes twice through the medium: on the propagation path ground station — spacecraft and on the same path in the opposite direction. The spectra of frequency fluctuations in both the bands are obtained and, using them, the radial dependences of fluctuation intensities are found, which can be approximated by a power law. It is shown that the ratio of intensities of frequency fluctuations in the S- and X-bands is comparable with the theoretical value and characterizes the degree of correlation of irregularities of the electron density along the propagation path ground station — spacecraft and back. Analysis of the correlation of frequency fluctuations on the two paths allows one to get a lower estimate of the outer scale of the circumsolar plasma turbulence. For heliocentric distances R = 10 solar radii (R S ) the outer scale is larger than 0.25R S . 相似文献
455.
Dynamics of a satellite-stabilizer system is studied. It is supposed that there is a viscous friction in a hinge connecting
two bodies, but there is no elasticity. The attitude motion in a plane of circular orbit is considered, and parameters are
determined, at which natural oscillations near a stable equilibrium position in the orbital coordinate system are damped out
most rapidly. The rate of transient processes is estimated by a value of the degree of stability of linearized equations of
motion. The optimization of the degree of stability is sequentially performed in dimensionless damping coefficient (the first
stage) and in inertial system parameters (the second stage). The result of the first stage is the partition of system parameter
space into the regions, in each of which the maximum of the degree of stability is reached on a particular configuration of
roots of the characteristic equation. It is shown at the second stage that the global maximum is reached at two points of
parameter space, where one of system bodies degenerates into a plate, and the characteristic equation has four equal real
roots. 相似文献
456.
Castella F.R. Dunnebacke F.G. 《IEEE transactions on aerospace and electronic systems》1974,(6):891-895
A two-dimensional x, y Kalman tracking filter is analyzed for a track-while-scan (TWS) operation when the radar sensor measures range and bearing (r, ?) at uniform sampling intervals T seconds apart. This development explicitly considers the coupling between the quantities measured by the sensor (r, ?) and the Cartesian x, y coordinate system selected for the tracking operation. The steadystate components of the gain and error covariance matrixes are analytically determined under the assumption of a white noise maneuver acceleration model in two dimensions. These results are verified by computer calculation of the Kalman filter matrix equations. 相似文献
457.
A review is given of the present state of the problem of upper atmospheric emission, in relation to the processes which take
place in that region.
Translated by the Express Translation Service, Wimbledon, London, W-2. 相似文献
458.
J. B. Blake B. H. Mauk D. N. Baker P. Carranza J. H. Clemmons J. Craft W. R. Crain A. Crew Y. Dotan J. F. Fennell R. H. Friedel L. M. Friesen F. Fuentes R. Galvan C. Ibscher A. Jaynes N. Katz M. Lalic A. Y. Lin D. M. Mabry T. Nguyen C. Pancratz M. Redding G. D. Reeves S. Smith H. E. Spence J. Westlake 《Space Science Reviews》2016,199(1-4):309-329
459.
We investigate the behavior of mean values of the solar wind’s and interplanetary magnetic field’s (IMF) parameters and their
absolute and relative variations during the magnetic storms generated by various types of the solar wind. In this paper, which
is a continuation of paper [1], we, on the basis of the OMNI data archive for the period of 1976–2000, have analyzed 798 geomagnetic
storms with D
st
≤ −50 nT and their interplanetary sources: corotating interaction regions CIR, compression regions Sheath before the interplanetary
CMEs; magnetic clouds MC; “Pistons” Ejecta, and an uncertain type of a source. For the analysis the double superposed epoch
analysis method was used, in which the instants of the magnetic storm onset and the minimum of the D
st
index were taken as reference times. It is shown that the set of interplanetary sources of magnetic storms can be sub-divided
into two basic groups according to their slowly and fast varying characteristics: (1) ICME (MC and Ejecta) and (2) CIR and
Sheath. The mean values, the absolute and relative variations in MC and Ejecta for all parameters appeared to be either mean
or lower than the mean value (the mean values of the electric field E
y
and of the B
z
component of IMF are higher in absolute value), while in CIR and Sheath they are higher than the mean value. High values
of the relative density variation sN/〈N〉 are observed in MC. At the same time, the high values for relative variations of the velocity, B
z
component, and IMF magnitude are observed in Sheath and CIR. No noticeable distinctions in the relationships between considered
parameters for moderate and strong magnetic storms were observed. 相似文献
460.
Structural health management technologies for inflatable/deployable structures: Integrating sensing and self-healing 总被引:1,自引:0,他引:1
Erik J. Brandon Max Vozoff Elizabeth A. Kolawa George F. Studor Frankel Lyons Michael W. Keller Brett Beiermann Scott R. White Nancy R. Sottos Mark A. Curry David L. Banks Robert Brocato Lisong Zhou Soyoun Jung Thomas N. Jackson Kevin Champaigne 《Acta Astronautica》2011,68(7-8):883-903
Inflatable/deployable structures are under consideration as habitats for future Lunar surface science operations. The use of non-traditional structural materials combined with the need to maintain a safe working environment for extended periods in a harsh environment has led to the consideration of an integrated structural health management system for future habitats, to ensure their integrity. This article describes recent efforts to develop prototype sensing technologies and new self-healing materials that address the unique requirements of habitats comprised mainly of soft goods. A new approach to detecting impact damage is discussed, using addressable flexible capacitive sensing elements and thin film electronics in a matrixed array. Also, the use of passive wireless sensor tags for distributed sensing is discussed, wherein the need for on-board power through batteries or hardwired interconnects is eliminated. Finally, the development of a novel, microencapuslated self-healing elastomer with applications for inflatable/deployable habitats is reviewed. 相似文献