全文获取类型
收费全文 | 2169篇 |
免费 | 4篇 |
国内免费 | 6篇 |
专业分类
航空 | 752篇 |
航天技术 | 762篇 |
综合类 | 8篇 |
航天 | 657篇 |
出版年
2022年 | 6篇 |
2021年 | 22篇 |
2019年 | 7篇 |
2018年 | 73篇 |
2017年 | 58篇 |
2016年 | 56篇 |
2015年 | 20篇 |
2014年 | 69篇 |
2013年 | 68篇 |
2012年 | 66篇 |
2011年 | 109篇 |
2010年 | 80篇 |
2009年 | 125篇 |
2008年 | 144篇 |
2007年 | 81篇 |
2006年 | 51篇 |
2005年 | 66篇 |
2004年 | 70篇 |
2003年 | 83篇 |
2002年 | 53篇 |
2001年 | 90篇 |
2000年 | 38篇 |
1999年 | 41篇 |
1998年 | 43篇 |
1997年 | 34篇 |
1996年 | 49篇 |
1995年 | 40篇 |
1994年 | 33篇 |
1993年 | 20篇 |
1992年 | 35篇 |
1991年 | 9篇 |
1990年 | 12篇 |
1989年 | 34篇 |
1988年 | 13篇 |
1987年 | 18篇 |
1986年 | 20篇 |
1985年 | 67篇 |
1984年 | 35篇 |
1983年 | 25篇 |
1982年 | 37篇 |
1981年 | 66篇 |
1980年 | 16篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 13篇 |
1976年 | 9篇 |
1975年 | 14篇 |
1974年 | 15篇 |
1973年 | 8篇 |
1970年 | 4篇 |
排序方式: 共有2179条查询结果,搜索用时 828 毫秒
691.
A.M. Galper V.G. Kirillov-Ugryumov Yu.D. Kotov L.V. Kurnosova A.V. Kurochkin N.G. Leikov V.I. Logachev L.A. Razorenov Yu.V. Smirnov M.I. Fradkin S.V. Damle P.K. Kunte B.V. Sreekantan 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(11):101-106
The report presents some results on the cosmic radiation intensity research carried out with the high-altitude balloons for the period of 1977–1979. The intensity of gamma-radiation with the energy above 40 MeV was measured in two balloon flights at an altitude of 4–7 g/cm2 of residual atmosphere in the vicinity of the geomagnetic equator. A temporal analysis of the intensity to discover fluctuations with periods in the range of 4–60 min was made. Quasi-periodic fluctuations of gamma-radiation intensity with 5 min periods, amplitude ~20% and duration of several hours were discovered. Possible mechanisms of such fluctuation appearance are discussed.The report gives the results of measuring downward, upward and horizontal electron fluxes in the vicinity of the equator. The obtained data and the data provided by satellites are compared. The report discusses the prospects of further joint Soviet-Indian research of cosmic gamma-radiation. 相似文献
692.
A.A. Borisov B.E. Gel'fand V.M. Kudinov B.I. Palamarchuk V.V. Stepanov E.I. Timofeev S.V. Khomik 《Acta Astronautica》1978,5(11-12)
Propagation of shock waves in tubes filled with water foams is studied using pressure gauges. Low amplitude shock waves consist of a precursor which propagates at a velocity slightly less than the acoustic velocity in the gas, and of a main compression wave which propagates slower than the precursor. Stronger shock waves have a single front. Maximum pressure rise in the incident and reflected shock waves cannot be calculated using one-dimensional conservation equations at the shock front. It is suggested that the flow of the liquid in foam cells has to be taken into account in order to predict the behavior of shock waves in foams. The nature of the gas which fills the cells is shown to have a strong effect on the quenching of blast waves in foams. 相似文献
693.
B. Kirov K. Georgieva E. Apostolov M. Gusheva I. Kutiev S. Chapkunov Yu. Simeonova 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1982,2(7):89-92
A Retarding Potential Analyzer (RPA) is designed using a micro-channel plate in front of the collector as a flow amplifier, which makes it possible to detect ion species with very low concentration (<0,5 cm.?3). A technique is described for using the micro-channel plate at abnormally high pressure (>0.01 N/m2). This allows the precise determination of the mass composition of the low ionosphere. An adaptive retarding potential consisting of 2048 steps is used to increase the sensitivity. This retarding potential is applied in the range where dI/dU ≠ 0. The sensor is hermetically sealed and opens on command. 相似文献
694.
Results are reported on the attempt to define a pseudotransfer funtion of a circuit composed of a 2-pulse canceler and hard limiter. 相似文献
695.
The properties of an adaptive array antenna, including transient response rate and control loop noise, depend on the intensity of the external noise field. This dependence can be reduced by envelope hard limiting in the control loops, without degrading the performance of the adaptive array. 相似文献
696.
A minimax filter is derived to estimate the state of a system, using observations corrupted by colored noise, when large uncertainties in the plant dynamics and process noise are present. 相似文献
697.
Analysis of a typical amplitude-comparison monopulse angle-tracking radar shows that gain variation and bias in the radar error signal can occur under certain conditions involving multiple targets. The general behavior depends on the Doppler separation of the targets relative to system bandwidths; for a specific situation, the gain variation and bias are functions of the relative strengths of the targs. The analysis is shown to be consistent with experimental observations. 相似文献
698.
699.
T I Pisman Ya V Galayda N S Loginova 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2005,35(9):1579-1583
The paper deals with microalgae-bacteria interrelationships in the "autotroph-heterotroph" aquatic biotic cycle. Explanations of why and how algal-bacterial ecosystems are formed still remain controversial. The paper presents results of experimental and theoretical investigations of the functioning of the algal-bacterial cenosis (the microalga Chlorella vulgaris and concomitant microflora). The Chlorella microbial community is dominated by representatives of the genus Pseudomonas. Experiments with non-sterile batch cultures of Chlorella on Tamiya medium showed that the biomass of microorganisms increases simultaneously with the increase in microalgal biomass. The microflora of Chlorella can grow on organic substances released by photosynthesizing Chlorella. Microorganisms can also use dying Chlorella cells, i.e. form a "producer-reducer" biocycle. To get a better insight into the cenosis-forming role of microalgae, a mathematical model of the "autotroph-heterotroph" aquatic biotic cycle has been constructed, taking into account the utilization of Chlorella photosynthates and dead cells by microorganisms and the contribution of the components to the nitrogen cycle. A theoretical study showed that the biomass of concomitant bacteria grown on glucose and detritus is larger than the biomass of bacteria utilizing only microalgal photosynthates, which agrees well with the experimental data. 相似文献
700.
This paper is devoted to the analysis of the results of wide-angle polarimetric observations of the night sky, which has been carried out in December 2002 in the Southern Laboratory of Shternberg State Astronomical Institute (Crimea, Ukraine) in a color band close to the V band (the effective wavelength is 5250 ). We propose a method with the help of which the sky light was separated into basic components: the atmospheric glow, emission of weak stars, and the zodiacal light. The polarization map of extra-atmospheric emission of five sky zones close to the ecliptic is constructed, and it is shown that polarization of the sky background far from the antisolar point is determined, in the main, by the zodiacal light. For each observational period, the time dependence of the atmospheric luminosity and absorption is obtained.Translated from Kosmicheskie Issledovaniya, Vol. 43, No. 1, 2005, pp. 19–26.Original Russian Text Copyright © 2005 by Ougolnikov, Maslov. 相似文献