全文获取类型
收费全文 | 2469篇 |
免费 | 28篇 |
国内免费 | 12篇 |
专业分类
航空 | 983篇 |
航天技术 | 911篇 |
综合类 | 12篇 |
航天 | 603篇 |
出版年
2022年 | 13篇 |
2021年 | 27篇 |
2019年 | 24篇 |
2018年 | 73篇 |
2017年 | 61篇 |
2016年 | 49篇 |
2015年 | 20篇 |
2014年 | 78篇 |
2013年 | 91篇 |
2012年 | 71篇 |
2011年 | 137篇 |
2010年 | 102篇 |
2009年 | 145篇 |
2008年 | 148篇 |
2007年 | 77篇 |
2006年 | 63篇 |
2005年 | 76篇 |
2004年 | 79篇 |
2003年 | 81篇 |
2002年 | 56篇 |
2001年 | 75篇 |
2000年 | 39篇 |
1999年 | 47篇 |
1998年 | 52篇 |
1997年 | 49篇 |
1996年 | 41篇 |
1995年 | 56篇 |
1994年 | 35篇 |
1993年 | 38篇 |
1992年 | 50篇 |
1991年 | 13篇 |
1990年 | 16篇 |
1989年 | 45篇 |
1988年 | 19篇 |
1987年 | 16篇 |
1986年 | 13篇 |
1985年 | 60篇 |
1984年 | 51篇 |
1983年 | 41篇 |
1982年 | 42篇 |
1981年 | 56篇 |
1980年 | 34篇 |
1979年 | 16篇 |
1978年 | 17篇 |
1977年 | 9篇 |
1976年 | 16篇 |
1975年 | 15篇 |
1974年 | 12篇 |
1971年 | 7篇 |
1969年 | 7篇 |
排序方式: 共有2509条查询结果,搜索用时 46 毫秒
971.
J. Isbert J.H. Adams Jr. H.S. Ahn G.L. Bashindzhagyan K.E. Batkov M. Christl A.R. Fazely O. Ganel R.M. Gunashingha T.G. Guzik J. Chang K.C. Kim E.N. Kouznetsov Z.W. Lin M.I. Panasyuk A.D. Panov W.K.H. Schmidt E.S. Seo N.V. Sokolskaya John W. Watts J.P. Wefel J. Wu V.I. Zatsepin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
The Advanced Thin Ionization Calorimeter (ATIC) Balloon Experiment had a successful test flight and a science flight in 2000–01 and 2002–03 and an unsuccessful launch in 2005–06 from McMurdo, Antarctica, returning 16 and 19 days of flight data. ATIC is designed to measure the spectra of cosmic rays (protons to iron). The instrument is composed of a Silicon matrix detector followed by a carbon target interleaved with scintillator tracking layers and a segmented BGO calorimeter composed of 320 individual crystals totaling 18 radiation lengths to determine the particle energy. BGO (Bismuth Germanate) is an inorganic scintillation crystal and its light output depends not only on the energy deposited by particles but also on the temperature of the crystal. The temperature of balloon instruments during flight is not constant due to sun angle variations as well as differences in albedo from the ground. The change in output for a given energy deposit in the crystals in response to temperature variations was determined. 相似文献
972.
N.J. Szewczyk J. Tillman C.A. Conley L. Granger L. Segalat A. Higashitani S. Honda Y. Honda H. Kagawa R. Adachi A. Higashibata N. Fujimoto K. Kuriyama N. Ishioka K. Fukui D. Baillie A. Rose G. Gasset B. Eche D. Chaput M. Viso 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
973.
A conceptual configuration of the lunar base bioregenerative life support system including soil-like substrate for growing plants 总被引:1,自引:0,他引:1
H. Liu C.Y. Yu N.S. Manukovsky V.S. Kovalev Yu L. Gurevich J. Wang 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
The paper presents a conceptual configuration of the lunar base bioregenerative life support system (LBLSS), including soil-like substrate (SLS) for growing plants. SLS makes it possible to combine the processes of plant growth and the utilization of plant waste. Plants are to be grown on SLS on the basis of 20 kg of dry SLS mass or 100 kg of wet SLS mass per square meter. The substrate is to be delivered to the base ready-made as part of the plant growth subsystem. Food for the crew was provided by prestored stock 24% and by plant growing system 76%. Total dry weight of the food is 631 g per day (2800 kcal/day) for one crew member (CM). The list of candidate plants to be grown under lunar BLSS conditions included 14 species: wheat, rice, soybean, peanuts, sweet pepper, carrots, tomatoes, coriander, cole, lettuce, radish, squash, onion and garlic. From the prestored stock the crew consumed canned fish, iodinated salt, sugar, beef sauce and seafood sauce. Our calculations show that to provide one CM with plant food requires the area of 47.5 m2. The balance of substance is achieved by the removal dehydrated urine 59 g, feces 31 g, food waste 50 g, SLS 134 g, and also waters 86 g from system and introduction food 236 g, liquid potassium soap 4 g and mineral salts 120 g into system daily. To reduce system setup time the first plants could be sowed and germinated to a certain age on the Earth. 相似文献
974.
T.G. Guzik J.H. Adams Jr. H.S. Ahn G.L. Bashindzhagyan K.E. Batkov J. Chang M. Christl A.R. Fazely O. Ganel R.M. Gunashingha J. Isbert K.C. Kim E.N. Kouznetsov M.I. Panasyuk A.D. Panov W.K.H. Schmidt E.S. Seo N.V. Sokolskaya J.W. Watts J.P. Wefel J. Wu V.I. Zatsepin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
The Advanced Thin Ionization Calorimeter (ATIC) experiment is designed to investigate the charge composition and energy spectra of primary cosmic rays over the energy range from about 1011 to 1014 eV during Long Duration Balloon (LDB) flights from McMurdo, Antarctica. Currently, analysis from the ATIC-1 test flight and ATIC-2 science flight is underway and preparation for a second science flight is in progress. Charge identification of the incident cosmic ray is accomplished, primarily, by a pixilated Silicon Matrix detector located at the very top of the instrument. While it has been shown that the Silicon Matrix detector provides good charge identification even in the presence of electromagnetic shower backscatter from the calorimeter, the detector only measures the charge once. In this paper, we examine use of the top scintillator hodoscope detector to provide a second measure of the cosmic ray charge and, thus, improve the ATIC charge identification. 相似文献
975.
E.S. Seo H.S. Ahn P. Allison M.G. Bagliesi L. Barbier A. Barrau R. Bazer-Bachi J.J. Beatty G. Bigongiari P. Boyle T.J. Brandt M. Buénerd J.T. Childers N.B. Conklin S. Coutu L. Derome M.A. DuVernois O. Ganel J.H. Han J.A. Jeon K.C. Kim M.H. Lee L. Lutz A. Malinin M. Mangin-Brinet P.S. Marrocchesi P. Maestro A. Menchaca-Rocha S. Minnick S.I. Mognet S. Nam S. Nutter I.H. Park N.H. Park A. Putze R. Sina S. Swordy S. Wakely P. Walpole J. Wu J. Yang Y.S. Yoon R. Zei S.Y. Zinn 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
The Cosmic-Ray Energetics And Mass balloon-borne experiment has been launched twice in Antarctica, first in December 2004 and again in December 2005. It circumnavigated the South Pole three times during the first flight, which set a flight duration record of 42 days. A cumulative duration of 70 days within 13 months was achieved when the second flight completed 28 days during two circumnavigations of the Pole on 13 January 2006. Both the science instrument and support systems functioned extremely well, and a total 117 GB of data including 67 million science events were collected during these two flights. Preliminary analysis indicates that the data extend well above 100 TeV and follow reasonable power laws. The payload recovered from the first flight has been refurbished for the third flight in 2007, whereas the payload from the second flight is being refurbished to be ready for the fourth flight in 2008. Each flight will extend the reach of precise cosmic-ray composition measurements to energies not previously possible. 相似文献
976.
T. Ma J. Chang N. Zhang M.S. Cai Y.Z. Gong H.S. Tang R.J. Zhang N.S. Wang M. Yu J.P. Mao S.B. Su Z. Fang R. Xu Y.M. Hu Q. Gu Y.L. Zhou A.A. Xu L.G. Liu 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
Gamma-ray spectrometer (GRS) is included in the payload of Chinese first lunar mission Chang’E-1 that will be launched in 2007. Specific objectives of the GRS are to map abundance of O, Si, Fe, Ti, U, Th, K, and perhaps, Mg, Al, and Ca to depths of about 20 cm. There are remarkable advantages for GRS application to remote sensing elemental materials over the entire lunar surface: large effective area and good ability for background rejection. We will describe the design of GRS and present its performance in this paper. Moreover, the GRS calibration will also be introduced. 相似文献
977.
A mechanical model of the line-of-sight stabilization system for the optical device mounted on a movable carrier vehicle is considered. The nonlinear Lagrange equations of motion for a four-axis gimbal suspension are derived. Requirements on design and parameters for the passive line-of-sight shock absorption system of the optoelectronic payload are worked out. 相似文献
978.
N. F. Averkiev S. A. Vlasov V. V. Salov V. V. Kiselev 《Russian Aeronautics (Iz VUZ)》2016,59(4):474-479
A method of finding the aircraft optimal route by means of task-oriented replacement of the functional being optimized is proposed. 相似文献
979.
980.
CW radar signals and processors are discussed. The use of the periodic ambiguity function (PAF) to analyze the delay-Doppler performance of CW signals and their corresponding correlation receivers, is extended to include weight function effects. This work provides tools which can predict the delay-Doppler response of almost any phase-coded CW radar. Examples demonstrate that a combination of CW signals having perfect periodic autocorrelation, a matched reference signal with a large number of modulation periods and a smooth weight function, can create a delay-Doppler response with extremely low sidelobes, strongly resembling the response of a coherent pulse train 相似文献