全文获取类型
收费全文 | 4320篇 |
免费 | 9篇 |
国内免费 | 6篇 |
专业分类
航空 | 1775篇 |
航天技术 | 1285篇 |
综合类 | 21篇 |
航天 | 1254篇 |
出版年
2022年 | 18篇 |
2021年 | 52篇 |
2019年 | 22篇 |
2018年 | 214篇 |
2017年 | 167篇 |
2016年 | 133篇 |
2015年 | 54篇 |
2014年 | 139篇 |
2013年 | 164篇 |
2012年 | 155篇 |
2011年 | 235篇 |
2010年 | 209篇 |
2009年 | 287篇 |
2008年 | 272篇 |
2007年 | 197篇 |
2006年 | 86篇 |
2005年 | 140篇 |
2004年 | 114篇 |
2003年 | 121篇 |
2002年 | 99篇 |
2001年 | 136篇 |
2000年 | 52篇 |
1999年 | 64篇 |
1998年 | 79篇 |
1997年 | 47篇 |
1996年 | 61篇 |
1995年 | 90篇 |
1994年 | 81篇 |
1993年 | 45篇 |
1992年 | 59篇 |
1991年 | 13篇 |
1990年 | 21篇 |
1989年 | 51篇 |
1988年 | 16篇 |
1987年 | 25篇 |
1986年 | 19篇 |
1985年 | 94篇 |
1984年 | 72篇 |
1983年 | 55篇 |
1982年 | 48篇 |
1981年 | 94篇 |
1980年 | 27篇 |
1979年 | 21篇 |
1978年 | 19篇 |
1977年 | 19篇 |
1976年 | 17篇 |
1975年 | 19篇 |
1974年 | 18篇 |
1972年 | 21篇 |
1971年 | 13篇 |
排序方式: 共有4335条查询结果,搜索用时 109 毫秒
31.
R D Govorun I V Koshlan N A Koshlan E A Krasavin N L Shmakova 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2002,30(4):885-890
The induction of HPRT-mutations and survival of Chinese hamster cells (line B11ii-FAF28, clone 431) were studied after irradiation by 4He and 12C-ions of various LET (20-360 keV/micrometers), produced by the U-200 heavy ion accelerator. The RBE increases with LET up to the maximum at 100-200 keV/micrometers and then decreases. Cytogenetic analysis was performed on the HPRT-mutant subclones selected from unirradiated Chinese hamster V-79 cells and from HPRT-mutant subclones that arose after exposure to gamma-rays, 1 GeV protons and 14N-ions (LET-77 keV/micrometers), produced by the synchrophasotron and the U-400M heavy ion accelerator. Slow growing mutant subclones were observed. The cytogenetic properties of individual clones were highly heterogeneous and chromosome instability was observed in both spontaneous and radiation-induced mutants. Chromosome instability was highest among spontaneous mutants and decreased with increasing LET. 相似文献
32.
V. Koblik E. Polyakhova L. Sokolov A. Shmyrov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2002,29(12):4431-2088
We present results of numerical simulations of trajectories of a space probe with a flat solar sail which moves from a circular Earth orbit to near-Sun regions. We consider the upper limit of the sail temperature as the basic restriction. We also examine the planar (ecliptic) solar sail transfer with gravity-assist flybys around planets. 相似文献
33.
34.
F. S. Khairullin 《Russian Aeronautics (Iz VUZ)》2009,52(4):480-483
We consider a possibility to apply the method of analyzing the complex-shaped shells, proposed in [1], for determining the
stress strain state of thin shells with a degenerating domain. The results of numerical calculations are presented. 相似文献
35.
A. Sh. Dzhabrailov Yu. V. Klochkov S. S. Marchenko A. P. Nikolaev 《Russian Aeronautics (Iz VUZ)》2007,50(2):115-120
We demonstrate that it is possible to express each component of the displacement vector for the interior point of the finite element (FE) through all components of nodal unknowns in curvilinear coordinates. The effectiveness of the valid technique of vector approximation for displacement fields has been verified on an example. 相似文献
36.
D. Koschny V. Dhiri K. Wirth J. Zender R. Solaz R. Hoofs R. Laureijs T.-M Ho B. Davidsson G. Schwehm 《Space Science Reviews》2007,128(1-4):167-188
ESA’s Rosetta mission was launched in March 2004 and is on its way to comet 67P/Churyumov-Gerasimenko, where it is scheduled
to arrive in summer 2014. It comprises a payload of 12 scientific instruments and a Lander. All instruments are provided by
Principal Investigators, which are responsible for their operations.
As for most ESA science missions, the ground segment of the mission consists of a Mission Operations Centre (MOC) and a Science
Operations Centre (SOC). While the MOC is responsible for all spacecraft-related aspects and the final uplink of all command
timelines to the spacecraft, the scientific operations of the instruments and the collection of the data and ingestion into
the Planetary Science Archive are coordinated by the SOC. This paper focuses on the tasks of the SOC and in particular on
the methodology and constraints to convert the scientific goals of the Rosetta mission to operational timelines. 相似文献
37.
The fastest pulsar and the slowest nova; the oldest galaxies and the youngest stars; the weirdest life forms and the commonest
dwarfs; the highest energy particles and the lowest energy photons. These were some of the extremes of Astrophysics 2006.
We attempt also to bring you updates on things of which there is currently only one (habitable planets, the Sun, and the Universe)
and others of which there are always many, like meteors and molecules, black holes and binaries. 相似文献
38.
N. N. Makarov 《Russian Aeronautics (Iz VUZ)》2008,51(1):60-66
The problem is formulated and a technique is revealed for synthesizing the optimal strategy of troubleshooting and constructing an operation algorithm for the information-control system of inspection and diagnostics of the aircraft equipment state. 相似文献
39.
V. A. Ovchinnikov 《Russian Aeronautics (Iz VUZ)》2007,50(2):146-149
We analyze the effect of injection both of uniformly distributed over the entire cylinder surface and of the optimal one on the velocity distribution at the outer border of the boundary layer and, as a result, on friction. 相似文献
40.
The results of studying an incompressible gas flow field in a periodic element of the porous structure made up of the same radius spheres are presented; the studies were based on the solution of the Navier-Stokes equations using FLUENT software. The possibilities to accelerate the solution process with the use of parallel calculations are investigated and the calculation results under changes of pressure differential in the periodic element are given. 相似文献