全文获取类型
收费全文 | 5146篇 |
免费 | 27篇 |
国内免费 | 9篇 |
专业分类
航空 | 2658篇 |
航天技术 | 1798篇 |
综合类 | 23篇 |
航天 | 703篇 |
出版年
2021年 | 36篇 |
2019年 | 32篇 |
2018年 | 80篇 |
2017年 | 59篇 |
2016年 | 51篇 |
2014年 | 86篇 |
2013年 | 110篇 |
2012年 | 102篇 |
2011年 | 156篇 |
2010年 | 116篇 |
2009年 | 178篇 |
2008年 | 264篇 |
2007年 | 113篇 |
2006年 | 101篇 |
2005年 | 128篇 |
2004年 | 131篇 |
2003年 | 167篇 |
2002年 | 96篇 |
2001年 | 162篇 |
2000年 | 111篇 |
1999年 | 101篇 |
1998年 | 149篇 |
1997年 | 108篇 |
1996年 | 138篇 |
1995年 | 177篇 |
1994年 | 168篇 |
1993年 | 100篇 |
1992年 | 136篇 |
1991年 | 60篇 |
1990年 | 65篇 |
1989年 | 143篇 |
1988年 | 59篇 |
1987年 | 59篇 |
1986年 | 81篇 |
1985年 | 165篇 |
1984年 | 132篇 |
1983年 | 122篇 |
1982年 | 121篇 |
1981年 | 144篇 |
1980年 | 56篇 |
1979年 | 46篇 |
1978年 | 52篇 |
1977年 | 44篇 |
1975年 | 53篇 |
1974年 | 45篇 |
1973年 | 39篇 |
1972年 | 51篇 |
1971年 | 45篇 |
1969年 | 35篇 |
1967年 | 30篇 |
排序方式: 共有5182条查询结果,搜索用时 312 毫秒
241.
We considered the influence of temperature on the nitric oxide emission under combustion of the near-stoichiometric mixtures
with and without water feed. We revealed the advantage of the method of fuel-water-air mixture combustion over that of the
leaned mixture combustion. 相似文献
242.
N. D. Akhmetov M. M. Gimadeev V. N. Drulis V. A. Krivosheev T. V. Rzaeva 《Russian Aeronautics (Iz VUZ)》2011,54(1):108-113
A technique for calculating the energy parameters of shock waves at electrical discharge in water is presented for the transition
region of discharge channel expansion using as the base the predetermined characteristics of discharge circuit. The technique
is based on the solution of energy transport equation that is similar in form to that of radiative transfer. The validity
of the presented approach was experimentally verified. 相似文献
243.
The results of investigating free oscillations of the International Space Station construction appearing during spacecraft docking and undocking are described. The study is carried out using the measurement
data of the low-frequency MAMS accelerometer. Several intervals of measurements performed in 2005 and 2006 were chosen to
be studied. For chosen intervals, only the data intervals corresponding to the process of free attenuation of the oscillations
construction elements were analyzed. Characteristic frequencies of elastic oscillations of the station construction and attenuation
coefficients corresponding to them are found. The comparative analysis of the results obtained for various docking ports (nodes)
is carried out. The described study is performed as a part of the technical experiment “The ISS Environment” carried out onboard the station in accordance with the Russian program of scientific and engineering experiments. 相似文献
244.
J. Mazur L. Friesen A. Lin D. Mabry N. Katz Y. Dotan J. George J. B. Blake M. Looper M. Redding T. P. O’Brien J. Cha A. Birkitt P. Carranza M. Lalic F. Fuentes R. Galvan M. McNab 《Space Science Reviews》2013,179(1-4):221-261
The Relativistic Proton Spectrometer (RPS) on the Radiation Belt Storm Probes spacecraft is a particle spectrometer designed to measure the flux, angular distribution, and energy spectrum of protons from ~60 MeV to ~2000 MeV. RPS will investigate decades-old questions about the inner Van Allen belt proton environment: a nearby region of space that is relatively unexplored because of the hazards of spacecraft operation there and the difficulties in obtaining accurate proton measurements in an intense penetrating background. RPS is designed to provide the accuracy needed to answer questions about the sources and losses of the inner belt protons and to obtain the measurements required for the next-generation models of trapped protons in the magnetosphere. In addition to detailed information for individual protons, RPS features count rates at a 1-second timescale, internal radiation dosimetry, and information about electrostatic discharge events on the RBSP spacecraft that together will provide new information about space environmental hazards in the Earth’s magnetosphere. 相似文献
245.
Marco B. Quadrelli Paul Backes W. Keats Wilkie Lou Giersch Ubaldo Quijano Jason Keim Daniel Scharf Rudranarayan Mukherjee S. Case Bradford Michael McKee 《Acta Astronautica》2011,68(7-8):947-973
This paper summarizes the modeling, simulation, and testing work related to the development of technology to investigate the potential that shape memory actuation has to provide mechanically simple and affordable solutions for delivering assets to a surface and for sample capture and possible return to Earth. We investigate the structural dynamics and controllability aspects of an adaptive beam carrying an end-effector which, by changing material equilibrium phases, is able to actively decouple the end-effector dynamics from the spacecraft dynamics during the surface contact phase. Asset delivery and sample capture and return are at the heart of several emerging potential missions to small bodies, such as asteroids and comets, and to the surface of large bodies, such as Titan. 相似文献
246.
247.
248.
为提升高压比串列离心压气机的性能,借鉴常规一体化离心叶轮中偏置分流叶片的方法,针对某高压比串列离心压气机,应用数值仿真手段分析了串列叶轮中导风轮叶片周向偏置对压气机流场和性能的影响。通过对不同导风轮叶片偏置方案下压气机流场的分析,建立了压气机流动损失与偏置参数的关联性。研究表明:采用较大的偏置参数γ可降低导风轮叶片1前缘的激波强度,改善激波作用导致的泄漏涡破碎和流动分离,但过大或过小的γ方案中导风轮叶顶会出现二次泄漏致使低能流体的掺混损失增加;γ=65%方案压气机综合性能最佳,其压比和效率较γ=50%分别提高了1.5%和1.4%;对于串列离心压气机导风轮叶片周向位置的优化,在避免导风轮叶顶形成较强二次泄漏的前提下,应考虑采用较大的偏置参数γ,同时应防止诱导轮尾迹流体参与导风轮的叶顶泄漏。 相似文献
249.
D. Vaniman M. D. Dyar R. Wiens A. Ollila N. Lanza J. Lasue J. M. Rhodes S. Clegg H. Newsom 《Space Science Reviews》2012,170(1-4):229-255
The ChemCam instrument on the Mars Science Laboratory rover Curiosity will use laser-induced breakdown spectroscopy (LIBS) to analyze major and minor element chemistry from sub-millimeter spot sizes, at ranges of ~1.5–7?m. To interpret the emission spectra obtained, ten calibration standards will be carried on the rover deck. Graphite, Ti?metal, and four glasses of igneous composition provide primary, homogeneous calibration targets for the laser. Four granular ceramic targets have been added to provide compositions closer to soils and sedimentary materials like those expected at the Gale Crater field site on Mars. Components used in making these ceramics include basalt, evaporite, and phyllosilicate materials that approximate the chemical compositions of detrital and authigenic constituents of clastic and evaporite sediments, including the elevated sulfate contents present in many Mars sediments and soils. Powdered components were sintered at low temperature (800?°C) with a small amount (9?wt.%) of lithium tetraborate flux to produce ceramics that retain volatile sulfur yet are durable enough for the mission. The ceramic targets are more heterogeneous than the pure element and homogenous glass standards but they provide standards with compositions more similar to the sedimentary rocks that will be Curiosity’s prime targets at Gale Crater. 相似文献
250.
Solar Wind Electron Proton Alpha Monitor (SWEPAM) for the Advanced Composition Explorer 总被引:1,自引:0,他引:1
McComas D.J. Bame S.J. Barker P. Feldman W.C. Phillips J.L. Riley P. Griffee J.W. 《Space Science Reviews》1998,86(1-4):563-612
The Solar Wind Electron Proton Alpha Monitor (SWEPAM) experiment provides the bulk solar wind observations for the Advanced
Composition Explorer (ACE). These observations provide the context for elemental and isotopic composition measurements made
on ACE as well as allowing the direct examination of numerous solar wind phenomena such as coronal mass ejections, interplanetary
shocks, and solar wind fine structure, with advanced, 3-D plasma instrumentation. They also provide an ideal data set for
both heliospheric and magnetospheric multi-spacecraft studies where they can be used in conjunction with other, simultaneous
observations from spacecraft such as Ulysses. The SWEPAM observations are made simultaneously with independent electron and
ion instruments. In order to save costs for the ACE project, we recycled the flight spares from the joint NASA/ESA Ulysses
mission. Both instruments have undergone selective refurbishment as well as modernization and modifications required to meet
the ACE mission and spacecraft accommodation requirements. Both incorporate electrostatic analyzers whose fan-shaped fields
of view sweep out all pertinent look directions as the spacecraft spins. Enhancements in the SWEPAM instruments from their
original forms as Ulysses spare instruments include (1) a factor of 16 increase in the accumulation interval (and hence sensitivity)
for high energy, halo electrons; (2) halving of the effective ion-detecting CEM spacing from ∼5° on Ulysses to ∼2.5° for ACE;
and (3) the inclusion of a 20° conical swath of enhanced sensitivity coverage in order to measure suprathermal ions outside
of the solar wind beam. New control electronics and programming provide for 64-s resolution of the full electron and ion distribution
functions and cull out a subset of these observations for continuous real-time telemetry for space weather purposes.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献