全文获取类型
收费全文 | 3351篇 |
免费 | 4篇 |
国内免费 | 3篇 |
专业分类
航空 | 1862篇 |
航天技术 | 827篇 |
综合类 | 13篇 |
航天 | 656篇 |
出版年
2018年 | 167篇 |
2017年 | 146篇 |
2016年 | 51篇 |
2015年 | 31篇 |
2014年 | 25篇 |
2013年 | 48篇 |
2012年 | 69篇 |
2011年 | 192篇 |
2010年 | 176篇 |
2009年 | 187篇 |
2008年 | 218篇 |
2007年 | 178篇 |
2006年 | 33篇 |
2005年 | 101篇 |
2004年 | 84篇 |
2003年 | 72篇 |
2002年 | 37篇 |
2001年 | 58篇 |
2000年 | 49篇 |
1999年 | 27篇 |
1998年 | 75篇 |
1997年 | 53篇 |
1996年 | 62篇 |
1995年 | 69篇 |
1994年 | 85篇 |
1993年 | 55篇 |
1992年 | 71篇 |
1991年 | 29篇 |
1990年 | 33篇 |
1989年 | 70篇 |
1988年 | 24篇 |
1987年 | 29篇 |
1986年 | 50篇 |
1985年 | 87篇 |
1984年 | 54篇 |
1983年 | 60篇 |
1982年 | 56篇 |
1981年 | 68篇 |
1980年 | 34篇 |
1979年 | 27篇 |
1978年 | 25篇 |
1977年 | 24篇 |
1975年 | 24篇 |
1974年 | 24篇 |
1973年 | 24篇 |
1972年 | 21篇 |
1971年 | 31篇 |
1969年 | 25篇 |
1967年 | 20篇 |
1966年 | 19篇 |
排序方式: 共有3358条查询结果,搜索用时 15 毫秒
941.
N. A. Vlasova N. N. Pavlov M. I. Panasyuk N. N. Vedenkin T. A. Ivanova G. P. Lyubimov S. Ya. Reizman V. I. Tulupov 《Cosmic Research》2011,49(6):485-499
We compared fluxes of the 1–100 MeV solar energetic particles (SEP) measured in the interplanetary medium (ACE) and in the magnetosphere (Universitetsky-Tatiana, POES—in polar caps, and GOES-11—at geosynchronous orbit) during several SEP events of 2005–2006. Peak intensities of the SEP fluxes inside and outside the
magnetosphere were compared for each event. It is shown that observed inside-outside difference depends mainly on direction
of interplanetary magnetic field (IMF), on degree of the SEP anisotropy (pitch-angle distribution) in IMF, and on distance
of the dayside magnetopause from the Earth. 相似文献
942.
W. R. Binns M. E. Wiedenbeck M. Arnould A. C. Cummings G. A. de Nolfo S. Goriely M. H. Israel R. A. Leske R. A. Mewaldt G. Meynet L. M. Scott E. C. Stone T. T. von Rosenvinge 《Space Science Reviews》2007,130(1-4):439-449
We have measured the isotopic abundances of neon and a number of other species in the galactic cosmic rays (GCRs) using the
Cosmic Ray Isotope Spectrometer (CRIS) aboard the ACE spacecraft. Our data are compared to recent results from two-component
(Wolf–Rayet material plus solar-like mixtures) Wolf–Rayet (WR) models. The three largest deviations of galactic cosmic ray
isotope ratios from solar-system ratios predicted by these models, 12C/16O, 22Ne/20Ne, and 58Fe/56Fe, are very close to those observed. All of the isotopic ratios that we have measured are consistent with a GCR source consisting
of ∼20% of WR material mixed with ∼80% material with solar-system composition. Since WR stars are evolutionary products of
OB stars, and most OB stars exist in OB associations that form superbubbles, the good agreement of our data with WR models
suggests that OB associations within superbubbles are the likely source of at least a substantial fraction of GCRs. In previous
work it has been shown that the primary 59Ni (which decays only by electron-capture) in GCRs has decayed, indicating a time interval between nucleosynthesis and acceleration
of >105 y. It has been suggested that in the OB association environment, ejecta from supernovae might be accelerated by the high
velocity WR winds on a time scale that is short compared to the half-life of 59Ni. Thus the 59Ni might not have time to decay and this would cast doubt upon the OB association origin of cosmic rays. In this paper we
suggest a scenario that should allow much of the 59Ni to decay in the OB association environment and conclude that the hypothesis of the OB association origin of cosmic rays
appears to be viable. 相似文献
943.
944.
945.
946.
Transfers with a low thrust are considered under constraints imposed on the thrust vector direction. These constraints can be caused by peculiarities of the attitude control system and the mode of stabilization of a spacecraft, and, in the general case, they are functions of the time and state vector. The constraints specified by equalities and inequalities are investigated. It is shown that the optimal thrust is directed along the projection of the Lawden’s primer vector onto the restricting set. 相似文献
947.
N. N. Inozemtsev 《Russian Aeronautics (Iz VUZ)》2010,53(4):443-449
A problem of applying closed multiloop thermodynamic cycles with mixing of dissimilar working gases in spacecraft power plants
has been considered. The advantage of these cycles that is due to reduction of a heat quantity being rejected into space has
been shown for ecologically clean generation of electric energy in prolonged space flights. 相似文献
948.
The mathematical models of the solid-liquid flow regimes in the vertical cylindrical channel are described. A two-speed flow
based on the solid-liquid phase interaction is considered. The problem was numerically solved and the calculation results
were compared with experimental data. 相似文献
949.
A procedure of calculating an axial radial-flow centrifugal stage is considered. Using the gas-dynamically expedient load
ratio distribution in profile, the process of impeller flow passage profiling is described. Also given are some techniques
for decreasing or eliminating a wake zone as well as a graph of loss dependence on the divergence factor and velocity deceleration
on the rarefaction side of the blade channel at the impeller outlet. 相似文献
950.
A comprehensive numerical study of transient interchamber processes occurring when reaching the SPRE operational conditions
is carried out. A conjugate problem under consideration includes nonstationary operation of an igniter heating, ignition and
subsequent nonstationary and turbulent burning of a solid-propellant charge; nonstationary three-phase homo-heterogeneous
flow of combustion products in the combustion chamber, nozzle and downstream of the nozzle block of a rocket engine; motion
of a nozzle block cover. The calculation results are presented. 相似文献