全文获取类型
收费全文 | 3490篇 |
免费 | 25篇 |
国内免费 | 5篇 |
专业分类
航空 | 1779篇 |
航天技术 | 1196篇 |
综合类 | 12篇 |
航天 | 533篇 |
出版年
2021年 | 30篇 |
2019年 | 27篇 |
2018年 | 63篇 |
2017年 | 46篇 |
2016年 | 47篇 |
2015年 | 23篇 |
2014年 | 67篇 |
2013年 | 84篇 |
2012年 | 81篇 |
2011年 | 118篇 |
2010年 | 89篇 |
2009年 | 135篇 |
2008年 | 183篇 |
2007年 | 90篇 |
2006年 | 77篇 |
2005年 | 94篇 |
2004年 | 86篇 |
2003年 | 113篇 |
2002年 | 70篇 |
2001年 | 122篇 |
2000年 | 73篇 |
1999年 | 83篇 |
1998年 | 106篇 |
1997年 | 70篇 |
1996年 | 95篇 |
1995年 | 131篇 |
1994年 | 102篇 |
1993年 | 62篇 |
1992年 | 90篇 |
1991年 | 34篇 |
1990年 | 39篇 |
1989年 | 86篇 |
1988年 | 43篇 |
1987年 | 37篇 |
1986年 | 35篇 |
1985年 | 96篇 |
1984年 | 92篇 |
1983年 | 82篇 |
1982年 | 83篇 |
1981年 | 90篇 |
1980年 | 27篇 |
1979年 | 27篇 |
1978年 | 29篇 |
1977年 | 27篇 |
1976年 | 19篇 |
1975年 | 35篇 |
1974年 | 25篇 |
1973年 | 18篇 |
1972年 | 33篇 |
1971年 | 18篇 |
排序方式: 共有3520条查询结果,搜索用时 0 毫秒
101.
D. Spänkuch W. von Hoyningen-Huene 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1982,2(5):131-134
In a previous paper the authors showed that the aerosol size distribution can be estimated with reasonable accuracy from spectral extinction measurements in a limited spectral region (λ ≤ 1 μm) only. Using the same method it will be discussed if the anticipated WMO turbidity network with four spectral channels has the potential of estimating the aerosol size distribution. 相似文献
102.
G. Stanev M. Petrunova D. Teodosiev I. Kutiev K. Serafimov S. Chapkunov V. Chmyrev N. Isaev P. Puschaev I. Pimenov S. Bilichanko 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1982,2(7):43-47
The instrument IESP-IPMP represents the complex unit measuring the vector of the DC electric field, the vectors of the electric and magnetic field in the frequency range of 0.2 – 6.5 Hz (wave form), autocorrelation functions of waves with frequencies of 0.1 – 5 kHz, and wave amplitudes in 8 bandpass channels. Some results are shown and compared in the various frequency ranges. 相似文献
103.
G.H. Schwehm R.H. Giese F. Giovane D.W. Schuerman J.L. Weinberg 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(8):121-125
The 1985 International Solar Polar Mission will provide the first opportunity to perform measurements from out of the ecliptic and from above the solar poles. Included in this mission is the Zodiacal Light/Background Starlight Experiment of the Ruhr-University Bochum, FRG (in collaboration with the State University of New York at Albany). The experiment is based on the use of a multicolor, sky-scanning photopolarimeter, which will be carried on the NASA S/C.The scientific objectives of the experiment are to investigate the intensity, polarization, and color of the diffuse sky brightness and determine the spatial distribution and physical properties of the interplanetary dust, including a possible interstellar component, as a function of S/C position in and out of the ecliptic.The instrument will allow simultaneous measurements in two separate wavelength bands. Measurements will be performed at 180, 220, 240, 280, 320, 350, 360, 440, 540, 640, 800 nm, including the state of polarization. Two different fields-of-view (1 sq deg and 5.6 sq deg) can be selected.The use of a microprocessor system in the instrument electronics will provide flexibility in measurement sequences and programs, on-board data processing and data quality control. 相似文献
104.
D. Cunnold 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(6):47-56
Stratospheric ozone observations by the SAGE and SBUV satellite instruments in March and April, 1979 have been analyzed. All SAGE profiles have been smoothed vertically over 8 km to provide some compatibility with the SBUV vertical resolution. Comparing the zonal mean ozone mixing ratios against smoothed LIMS profiles, it is inferred that SAGE is systematically overestimating ozone by approximately 20% at tropical latitudes at pressures lower than 5 mb and that SBUV is underestimating ozone by approximately 15% at 50–70° latitude at 10 mb. A comparison of the longitudinal variations of ozone by SBUV and SAGE is made and the detectability of planetary waves in ozone is emphasized. The uncorrelated portion of the SAGE variances are found to be approximately consistent with the SAGE noise model. Based on the correlated variances, the amplitudes of the smoothed SAGE planetary waves in ozone are found to be the same, on average, as in the SBUV experiment at mid-latitudes between 1 and 10 mb. Planetary wave detectability is illustrated during two several day periods at mid-latitudes and a persistent and theoretically-consistent relationship between ozone and temperature is noted. These examples, however, indicate that differences between ozone planetary wave amplitudes derived from the two sensors may occur when there is a strong vertical gradient in wave amplitude. 相似文献
105.
M.J. Smith J.B. Gregory A.H. Manson C.E. Meek R. Schminder D. Ku¨rschner K. Labitzke 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1982,2(10):173-176
The global developments of the four stratospheric events (~20–50 km) are described, using balloon, satellite and rocket data. Winds data for heights of 60–95 km, derived from L.F. drift (52°N, 15°E; Europe) and M.F. radar (52°N, 107°W; Canada), are then compared with the stratospheric data. There is clear evidence that the preliminary planetary waves often penetrate strongly to ~90 km, and that mean wind reversals also occur. However, there are dramatic differences between European and Canadian mesospheric responses. 相似文献
106.
M.G. Kivelson K.W. Behannon T.E. Cravens I. de Pater T.V. Johnson D.L. Matson H. Masursky D.J. Southwood V.M. Vasyliunas 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(3):5-14
A was presented in conjunction with the Twenty-fourth Plenary Meeting of the Committee on Space Research. This paper summarizes the talks presented and places the remaining papers of this volume in context. 相似文献
107.
Thin-film rechargeable Li-LiMn2O4 batteries have been fabricated and characterized. Following deposition by electron beam evaporation of LiMn2O4, the amorphous as-deposited cathode films 1 cm2 in area by 0.3to 4-μm thick were annealed at 700°C to 800°C in oxygen in order to form the crystalline spinet phase. The specific capacity of the cells between 4.5 V to 3.8 V ranged from 50 μAh/mg to 120 μAh/mg. When cycled over this range, the batteries exhibited excellent secondary performance with capacity losses as low as 0.001% per cycle. On charging to 5.3 V, a plateau with a median voltage of 5.1 V was observed. The total charge extracted between 3.8 V to 5.3 V corresponded to about 1 Li/Mn2 O4 相似文献
108.
The results of a survey of data on failures of aircraft electronic and electrical components that was conducted to identify problematic components are reported. The motivation for the work was to determine priorities for future work on the development of accident investigation techniques for aircraft electrical components. The primary source of data was the Airforce Mishap Database, which is maintained by the Directorate of Aerospace Safety at Norton Air Force Base. Published data from the Air Force Avionics Integrity Program (AVIP) and Hughes Aircraft were also reviewed. Statistical data from these three sources are presented. Two major conclusions are that problems with interconnections are major contributors to aircraft electrical equipment failures, and that environmental factors, especially corrosion, are significant contributors to connector problems 相似文献
109.
The application of magnetostriction in the design of a hybrid, electromechanical/hydraulic high-performance linear (large force and stroke) and/or rotational (large moment and angle) actuator is considered. The design concept combines the high power density of actuation possible with magnetostriction (approaching 0.1 HP/cm3 of the magnetostrictive material assuming 3 kHz excitation frequency) and the design flexibility of hydraulics. The objective of the research described was to validate the concept theoretically and to study alternatives and improvements. The system, as currently envisioned, offers very small packaging volume (approximately an order of magnitude smaller than conventional electromechanical systems), flexible packaging (relative location of the major system components is not critical), and easy control (precise control of actuation speed, quick reverse time, and inherent position lockup). The major technical problems associated with the design are outlined, and results of a computer simulation of a prototype actuator are presented 相似文献
110.
A smart system that uses state-of-the-art image processing techniques to detect and track targets moving in video or infrared imagery is presented. It is a general-purpose system that was developed to be independent of the application and the user interface. TCATS has successfully demonstrated a high detection capability and the ability to ignore exterior environmental conditions, such as cloud shadows moving through the scene, snow, blowing dust, rain and moderate camera motion. TCATS can handle many targets and retain the identity of each object from one frame to the next. Special rugged hardware has been developed to reduce the size, cost, and power consumption and to increase the processing rate, reliability, and environmental operating capability of the system. TCATS can be incorporated into an existing video assessment system without a major cost outlay intruder. The TCATS algorithms, custom-developed hardware, and preliminary field test results are described 相似文献