全文获取类型
收费全文 | 3716篇 |
免费 | 44篇 |
国内免费 | 28篇 |
专业分类
航空 | 1770篇 |
航天技术 | 1322篇 |
综合类 | 71篇 |
航天 | 625篇 |
出版年
2021年 | 35篇 |
2018年 | 51篇 |
2017年 | 61篇 |
2016年 | 34篇 |
2015年 | 35篇 |
2014年 | 74篇 |
2013年 | 100篇 |
2012年 | 85篇 |
2011年 | 164篇 |
2010年 | 116篇 |
2009年 | 142篇 |
2008年 | 207篇 |
2007年 | 115篇 |
2006年 | 109篇 |
2005年 | 117篇 |
2004年 | 81篇 |
2003年 | 118篇 |
2002年 | 91篇 |
2001年 | 105篇 |
2000年 | 88篇 |
1999年 | 102篇 |
1998年 | 107篇 |
1997年 | 102篇 |
1996年 | 89篇 |
1995年 | 104篇 |
1994年 | 107篇 |
1993年 | 64篇 |
1992年 | 76篇 |
1991年 | 39篇 |
1990年 | 44篇 |
1989年 | 75篇 |
1988年 | 39篇 |
1987年 | 32篇 |
1986年 | 34篇 |
1985年 | 113篇 |
1984年 | 79篇 |
1983年 | 79篇 |
1982年 | 60篇 |
1981年 | 103篇 |
1980年 | 25篇 |
1979年 | 27篇 |
1978年 | 33篇 |
1977年 | 25篇 |
1976年 | 23篇 |
1975年 | 40篇 |
1974年 | 20篇 |
1972年 | 33篇 |
1971年 | 25篇 |
1969年 | 23篇 |
1967年 | 24篇 |
排序方式: 共有3788条查询结果,搜索用时 78 毫秒
401.
C.T. Russell T.L. Zhang R.J. Strangeway H.Y. Wei M. Delva W. Magnes 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(1):113-117
The magnetometer on Venus Express was designed to be able to obtain 128 Hz samples of the magnetic field from two sensors in a gradiometer configuration. This mode is used around periapsis to determine whether the signals reported at low altitudes near 100 Hz, had the properties of electromagnetic waves generated by electric discharges in the Venus atmosphere. The lack of a magnetic cleanliness program and the shortness of the magnetometer boom make this a challenging measurement. Fortunately the signals are sufficiently strong that they can be easily resolved with rather straightforward analysis techniques. 相似文献
402.
V. Génot C. Jacquey M. Bouchemit M. Gangloff A. Fedorov B. Lavraud N. André L. Broussillou C. Harvey E. Pallier E. Penou E. Budnik R. Hitier B. Cecconi F. Dériot D. Heulet J.-L. Pinçon 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
AMDA (Automated Multi-Dataset Analysis), a new data analysis service, recently opened at the French Plasma Physics Data Center (CDPP). AMDA is developed according to the Virtual Observatory paradigm: it is a web-based facility for on-line analyses of space physics. Data may come from its own local database as well as remote ones. This tool allows the user to perform classical manipulations such as data visualization, parameter computation and data extraction. AMDA also offers innovative functionalities such as event searches on the content of the data in either visual or automated ways, generation, use and management of time tables (event lists). The general functionalities of AMDA are presented in the context of Space Weather with example scientific use cases. 相似文献
403.
A three-dimensional design model of a helicopter tubular skid landing gear based on the application of the large beam displacement
theory is presented. The design model takes into account special features of constructive, physical and geometrical deformation
nonlinearity. The analysis of a real helicopter structure is given that confirms sufficient validity of calculation results
obtained using the model developed by comparing with the results of the finite element analysis. 相似文献
404.
俯仰三角翼的流态及结构 总被引:1,自引:0,他引:1
本文对俯仰三角翼的流动特性进行了实验研究,给出了俯三角翼的截面流态特点,对三角翼俯仰 运动的流动机理进行了分析。 相似文献
405.
C. P. T. Groth D. L. De Zeeuw T. I. Gombosi K. G. Powell 《Space Science Reviews》1999,87(1-2):193-198
A parallel adaptive mesh refinement (AMR) scheme is described for solving the governing equations of ideal magnetohydrodynamics
(MHD) in three space dimensions. This solution algorithm makes use of modern finite-volume numerical methodology to provide
a combination of high solution accuracy and computational robustness. Efficient and scalable implementations of the method
have been developed for massively parallel computer architectures and high performance achieved. Numerical results are discussed
for a simplified model of the initiation and evolution of coronal mass ejections (CMEs) in the inner heliosphere. The results
demonstrate the potential of this numerical tool for enhancing our understanding of coronal and solar wind plasma processes.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
406.
Using empirical velocity distributions derived from UVCS and SUMER ultraviolet spectroscopy, we construct theoretical models
of anisotropic ion temperatures in the polar solar corona. The primary energy deposition mechanism we investigate is the dissipation
of high frequency (10-10000 Hz) ion-cyclotron resonant Alfvén waves which can heat and accelerate ions differently depending
on their charge and mass. We find that it is possible to explain the observed high perpendicular temperatures and strong anisotropies
with relatively small amplitudes for the resonant waves. There is suggestive evidence for steepening of the Alfvén wave spectrum
between the coronal base and the largest heights observed spectroscopically. Because the ion-cyclotron wave dissipation is
rapid, even for minor ions like O5+, the observed extended heating seems to demand a constantly replenished population of waves over several solar radii. This
indicates that the waves are generated gradually throughout the wind rather than propagated up from the base of the corona.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
407.
Do you know what Firewire is? If not, you soon will, IEEE 1394, or Firewire, is an up-and-coming electronics industry standard that will soon be in wide use for interconnecting a massive variety of electronic equipment. It will be used for connecting CD-ROMs and scanners to computers, and it will be used for connecting VCRs, DVDs and satellite dishes to digital televisions. How does this affect Test & Measurement? This paper discusses Firewire, along with it's lower-end companion, USE, and how they can and will be utilized in T&M applications to replace T&M specific technologies, such as IEEE 488, and MXI. The advantages-and disadvantages-of these new technologies are discussed along with what the Test & Measurement industry should do to support these new technologies. 相似文献
408.
A. V. Tavrov O. I. Korablev A. V. Rodin I. I. Vinogradov A. Yu. Trokhimovsky A. Yu. Ivanov L. V. Ksanfomaliti D. A. Orlov 《Cosmic Research》2011,49(2):99-109
In order to observe exoplanets we propose a space-based achromatic stellar coronagraph combined with a 0.8–1.5 m telescope.
We develop an achromatic common path interferometer for observing an exoplanet (a faint off-axis source) on the background
of a hoste star (bright axial source). An image of the star and its copy acquire an achromatic phase shift by 180° and interfere
in antiphase. The achromatic phase shift is caused by geometric phase in the scheme of a three-dimensional interferometer.
The interference process divides spatially the dark and light fields of the star image redirecting them to the opposite sides
of a beam splitter. The interference process does not weaken the image of a planet, with equal intensities it is redirected
to both sides of a beam splitter. The suggested scheme of common path interferometer ensures mechanical stability. The background
signal is experimentally demonstrated to be reduced by six orders of magnitude. 相似文献
409.
Possible consequences of collisions of natural cosmic bodies with the Earth’s atmosphere and surface are described. The methodological
basis of classification of consequences is the solution of meteor physics equations characterizing the trajectory of a body
in the atmosphere, namely, the dependence of the body’s velocity and mass on the flight altitude. The solution depends on
two dimensionless parameters characterizing the drag altitude and the role of mass loss by a meteoroid during its motion in
the atmosphere. Depending on values of these parameters, the degree of effect on the planetary surface considerably changes.
In particular, the conditions of cratering and meteorite fall on the planetary surface are obtained. The results are presented
in a simple analytical form. They quite match to the real events considered in the paper. Recommendations are given on further
investigations into the important problem of interaction of cosmic bodies with planetary atmospheres. 相似文献
410.
Ontological Modularity and Spatial Diversity 总被引:1,自引:1,他引:0