全文获取类型
收费全文 | 1082篇 |
免费 | 21篇 |
国内免费 | 3篇 |
专业分类
航空 | 484篇 |
航天技术 | 488篇 |
综合类 | 15篇 |
航天 | 119篇 |
出版年
2022年 | 6篇 |
2021年 | 12篇 |
2019年 | 8篇 |
2018年 | 10篇 |
2017年 | 4篇 |
2016年 | 12篇 |
2015年 | 5篇 |
2014年 | 24篇 |
2013年 | 23篇 |
2012年 | 34篇 |
2011年 | 45篇 |
2010年 | 30篇 |
2009年 | 50篇 |
2008年 | 94篇 |
2007年 | 26篇 |
2006年 | 29篇 |
2005年 | 47篇 |
2004年 | 36篇 |
2003年 | 32篇 |
2002年 | 25篇 |
2001年 | 50篇 |
2000年 | 19篇 |
1999年 | 36篇 |
1998年 | 38篇 |
1997年 | 13篇 |
1996年 | 32篇 |
1995年 | 21篇 |
1994年 | 33篇 |
1993年 | 22篇 |
1992年 | 29篇 |
1991年 | 10篇 |
1990年 | 14篇 |
1989年 | 31篇 |
1988年 | 13篇 |
1987年 | 6篇 |
1986年 | 12篇 |
1985年 | 20篇 |
1984年 | 28篇 |
1983年 | 23篇 |
1982年 | 20篇 |
1981年 | 24篇 |
1980年 | 6篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1975年 | 6篇 |
1974年 | 3篇 |
1970年 | 3篇 |
1969年 | 4篇 |
排序方式: 共有1106条查询结果,搜索用时 15 毫秒
241.
242.
K. Fujita Y. ItohT. Mukai 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
We are currently developing a polarimeter to study surface physical properties of asteroids. To enhance polarimetric accuracy and observational efficiency, we newly devised the polarimeter whose measurements can provide the two Stokes parameters Q and U, simultaneously. The test-observations of the prototype polarimeter have been carried out in December 2003 and January 2004, mounted on the 101 cm telescope at Bisei Astronomical Observatory, Okayama, Japan. In the observations, unpolarized and polarized standard stars were observed to measure an instrumental polarization and its uncertainty. As a result, an instrumental polarization of 5.06 ± 0.18% has been measured. 相似文献
243.
244.
K.Y. Chen S.Y. Su H.C. Yeh C.H. Liu 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
This paper adopts a scale analysis technique to investigate the properties of intermediate-scale plasma structures observed by ROCSAT-1 in the equatorial F-region. A procedure of scale analysis that is developed via the empirical mode decomposition (EMD) method of Hilbert–Huang transform (HHT) technique allows the mutually correlated components in velocity, density and relative density gradient to be identified and extracted. Comparing the three parameters, good match in wave form is found for density and velocity in the scales between kilometers and hundred meters (few kilometers to 300 m). It implies that there are electric fields proportional to density fluctuation −δn/n in the form similar to what is expected for the generalized Rayleigh–Taylor instability. We find that such a one-to-one match holds for various pre- and post-midnight ESF bubbles during quiet and storm times. It, therefore, means that spatial structures of electric field in the intermediate-scale (300 m to few kilometers) correlates to the density structures in a manner of δE ∝ −δn/n that is not necessarily depending on the driving mechanism of ESF bubbles, although it is known that ESF bubbles can be driven by different mechanisms under different space weather conditions. In smaller scales (300–50 m), fluctuation patterns of density and velocity do not correlate to each other any more, the good match is then found in the density gradient ∇xn/n and velocity. It is known as the manifestation of the Boltzmann relation. We note that the GRT instability related relationship δVz ∝ −δn/n for irregularities in scale of kilometers holds only for ESF bubbles that occur within ±5 dip latitude, while the Boltzmann relation (δVz proportional to ∇xn/n) holds for small-scale irregularities without such a limitation. 相似文献
245.
Efficient fault tolerant estimation using the IMM methodology 总被引:2,自引:0,他引:2
Space systems are characterized by a low-intensity process noise resulting from uncertain forces and moments. In many cases, their scalar measurement channels can be assumed to be independent, with one-dimensional internal dynamics. The nominal operation of these systems can be severely damaged by faults in the sensors. A natural method that can be used to yield fault tolerant estimates of such systems is the interacting multiple model (IMM) filtering algorithm, which is known to provide very accurate results. However, having been derived for a general class of systems with switching parameters, the IMM filter does not utilize the independence of the measurement errors in different channels, nor does it exploit the fact that the process noise is of low intensity. Thus, the implementation of the IMM in this case is computationally expensive. A new estimation technique is proposed herein, that explicitly utilizes the aforementioned properties. In the resulting estimation scheme separate measurement channels are handled separately, thus reducing the computational complexity. It is shown that, whereas the IMM complexity is exponential in the number of fault-prone measurements, the complexity of the proposed technique is polynomial. A simulation study involving spacecraft attitude estimation is carried out. This study shows that the proposed technique closely approximates the full-blown IMM algorithm, while requiring only a modest fraction of the computational cost. 相似文献
246.
因超高的理论能量密度,锂空气电池在航空航天、电动汽车等领域展示了广阔的应用前景,但其目前的性能仍与实际使用需求有较大的差距。本文旨在开发具有双功能催化作用的正极催化剂以提升锂空气电池的性能。采用简易的一步溶剂热法成功制备了花状结构的SnS_2微球,并首次探究了其作为可充锂空气电池正极催化剂的应用前景。结果表明:所制备的花状SnS_2微球对锂空气电池的正极过程具有优异的催化性能,大大改善了以其为催化剂的锂空气电池的综合性能,证明SnS_2是一种有潜力的、值得深入研究的锂空气电池用催化剂材料。 相似文献
247.
K. Abe H. Fuke S. Haino T. Hams M. Hasegawa A. Horikoshi A. Itazaki K.C. Kim T. Kumazawa A. Kusumoto M.H. Lee Y. Makida S. Matsuda Y. Matsukawa K. Matsumoto J.W. Mitchell A.A. Moiseev J. Nishimura M. Nozaki R. Orito J.F. Ormes N. Picot-Clémente K. Sakai M. Sasaki E.S. Seo Y. Shikaze R. Shinoda R.E. Streitmatter J. Suzuki Y. Takasugi K. Takeuchi K. Tanaka N. Thakur T. Yamagami A. Yamamoto T. Yoshida K. Yoshimura 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
The Balloon-borne Experiment with a Superconducting Spectrometer (BESS) is configured with a solenoidal superconducting magnet and a suite of precision particle detectors, including time-of-flight hodoscopes based on plastic scintillators, a silica-aerogel Cherenkov detector, and a high resolution tracking system with a central jet-type drift chamber. The charges of incident particles are determined from energy losses in the scintillators. Their magnetic rigidities (momentum/charge) are measured by reconstructing each particle trajectory in the magnetic field, and their velocities are obtained by using the time-of-flight system. Together, these measurements can accurately identify helium isotopes among the incoming cosmic-ray helium nuclei up to energies in the GeV per nucleon region. The BESS-Polar I instrument flew for 8.5 days over Antarctica from December 13th to December 21st, 2004. Its long-duration flight and large geometric acceptance allow the time variations of isotopic fluxes to be studied for the first time. The time variations of helium isotope fluxes are presented here for rigidities from 1.2 to 2.5 GV and results are compared to previously reported proton data and neutron monitor data. 相似文献
248.
Asteroid and comet hazard: Identification problem of observed space objects with the parental bodies
M.G. Sokolova Y.A. Nefedyev N.Y. Varaksina 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
This article focuses on the genetic identification of observed small cosmic bodies with alleged parental bodies; namely, comets, asteroids and meteoroid swarms. There is a problem of the upper D-value limit as a measure of proximity between the orbits of the bodies in the five-dimensional phase space (Southworth and Hawkins, 1963). In the study of genetic relationships of the comet and meteor complexes, the D value is usually taken as equal to 0.2 for all meteor showers. However, the upper D limit should be investigated for each meteoroid complex. For example, such investigation was performed for the Taurid meteor complex (Porub?an et al., 2006). In this paper, the upper D-criterion limit value was investigated for the Perseid meteor shower. The 1862 III Swift–Tuttle comet is its parental comet. 相似文献
249.
Kai Matsuka Aaron O. Feldman Elena S. Lupu Soon-Jo Chung Fred Y. Hadaegh 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(11):3527-3545
For spacecraft swarms, the multi-agent localization algorithm must scale well with the number of spacecraft and adapt to time-varying communication and relative sensing networks. In this paper, we present a decentralized, scalable algorithm for swarm localization, called the Decentralized Pose Estimation (DPE) algorithm. The DPE considers both communication and relative sensing graphs and defines an observable local formation. Each spacecraft jointly localizes its local subset of spacecraft using direct and communicated measurements. Since the algorithm is local, the algorithm complexity does not grow with the number of spacecraft in the swarm. As part of the DPE, we present the Swarm Reference Frame Estimation (SRFE) algorithm, a distributed consensus algorithm to co-estimate a common Local-Vertical, Local-Horizontal (LVLH) frame. The DPE combined with the SRFE provides a scalable, fully-decentralized navigation solution that can be used for swarm control and motion planning. Numerical simulations and experiments using Caltech’s robotic spacecraft simulators are presented to validate the effectiveness and scalability of the DPE algorithm. 相似文献