全文获取类型
收费全文 | 2709篇 |
免费 | 2篇 |
国内免费 | 8篇 |
专业分类
航空 | 1370篇 |
航天技术 | 1027篇 |
综合类 | 5篇 |
航天 | 317篇 |
出版年
2021年 | 19篇 |
2019年 | 16篇 |
2018年 | 99篇 |
2017年 | 65篇 |
2016年 | 27篇 |
2015年 | 16篇 |
2014年 | 53篇 |
2013年 | 71篇 |
2012年 | 55篇 |
2011年 | 102篇 |
2010年 | 77篇 |
2009年 | 110篇 |
2008年 | 158篇 |
2007年 | 71篇 |
2006年 | 50篇 |
2005年 | 68篇 |
2004年 | 77篇 |
2003年 | 94篇 |
2002年 | 47篇 |
2001年 | 105篇 |
2000年 | 45篇 |
1999年 | 88篇 |
1998年 | 86篇 |
1997年 | 62篇 |
1996年 | 64篇 |
1995年 | 89篇 |
1994年 | 97篇 |
1993年 | 41篇 |
1992年 | 62篇 |
1991年 | 22篇 |
1990年 | 28篇 |
1989年 | 56篇 |
1988年 | 21篇 |
1987年 | 36篇 |
1986年 | 20篇 |
1985年 | 75篇 |
1984年 | 44篇 |
1983年 | 47篇 |
1982年 | 58篇 |
1981年 | 80篇 |
1980年 | 26篇 |
1979年 | 24篇 |
1978年 | 22篇 |
1977年 | 18篇 |
1976年 | 15篇 |
1975年 | 18篇 |
1974年 | 12篇 |
1972年 | 17篇 |
1969年 | 13篇 |
1966年 | 9篇 |
排序方式: 共有2719条查询结果,搜索用时 31 毫秒
121.
Q. Wang G. Xu S. Petrovic U. Schaefer U. Meyer T. Xu 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
A regional tropospheric model can be constructed using surveys from GPS ground networks. Using this model the tropospheric delays of a kinematic station within the region can be interpolated. However, such a model is generally not suitable for an airborne platform high above the ground networks. In this paper, a method of constructing a regional tropospheric model for airborne GPS applications is described. First, the kinematic station in the air is projected onto the ground. Then the tropospheric delays at projected point are interpolated from those of the ground networks. Finally, the tropospheric delays at projected point are extended upward to the airborne platform using pressure and temperature gradients and humidity exponential function. For validation of this method, the data of airborne campaign carried out by BKG in cooperation with GFZ and BGR 2008 in the northern Alps are used. The results show that GPS kinematic positioning precision in height component can be improved using this method. 相似文献
122.
123.
An algorithm of analyzing the design parameters for a thin-walled wing from composite material based on the efficient distribution
of structural material between load-carrying elements is described. We consider the problems of convergence acceleration for
the iteration design analysis. Also presented are the examples of determining the design parameters for a superlight aircraft
wing and the rational parameters of the filler in the form of a three-dimensional rod structure. 相似文献
124.
N. D. Akhmetov M. M. Gimadeev V. N. Drulis V. A. Krivosheev T. V. Rzaeva 《Russian Aeronautics (Iz VUZ)》2011,54(1):108-113
A technique for calculating the energy parameters of shock waves at electrical discharge in water is presented for the transition
region of discharge channel expansion using as the base the predetermined characteristics of discharge circuit. The technique
is based on the solution of energy transport equation that is similar in form to that of radiative transfer. The validity
of the presented approach was experimentally verified. 相似文献
125.
J. Mazur L. Friesen A. Lin D. Mabry N. Katz Y. Dotan J. George J. B. Blake M. Looper M. Redding T. P. O’Brien J. Cha A. Birkitt P. Carranza M. Lalic F. Fuentes R. Galvan M. McNab 《Space Science Reviews》2013,179(1-4):221-261
The Relativistic Proton Spectrometer (RPS) on the Radiation Belt Storm Probes spacecraft is a particle spectrometer designed to measure the flux, angular distribution, and energy spectrum of protons from ~60 MeV to ~2000 MeV. RPS will investigate decades-old questions about the inner Van Allen belt proton environment: a nearby region of space that is relatively unexplored because of the hazards of spacecraft operation there and the difficulties in obtaining accurate proton measurements in an intense penetrating background. RPS is designed to provide the accuracy needed to answer questions about the sources and losses of the inner belt protons and to obtain the measurements required for the next-generation models of trapped protons in the magnetosphere. In addition to detailed information for individual protons, RPS features count rates at a 1-second timescale, internal radiation dosimetry, and information about electrostatic discharge events on the RBSP spacecraft that together will provide new information about space environmental hazards in the Earth’s magnetosphere. 相似文献
126.
127.
128.
Mahaffy P.R. Donahue T.M. Atreya S.K. Owen T.C. Niemann H.B. 《Space Science Reviews》1998,84(1-2):251-263
The Galileo Probe Mass Spectrometer measurements in the atmosphere of Jupiter give D/H = (2.6 ± 0.7) × 10-5 3He/4He = (1.66 ± 0.05) × 10-4These ratios supercede earlier results by Niemann et al. (1996) and are based on a reevaluation of the instrument response at high count rates and a more detailed study of the contributions of different species to the mass peak at 3 amu. The D/H ratio is consistent with Voyager and ground based data and recent spectroscopic and solar wind (SW) values obtained from the Infrared Spectroscopic Observatory (ISO) and Ulysses. The 3He/4He ratio is higher than that found in meteoritic gases (1.5 ± 0.3) × 10-4. The Galileo result for D/H when compared with that for hydrogen in the local interstellar medium (1.6 ± 0.12) × 10-5 implies a small decrease in D/H in this part of the universe during the past 4.55 billion years. Thus, it tends to support small values of primordial D/H - in the range of several times 10-5 rather than several times 10-4. These results are also quite consistent with no change in (D+3He)/H during the past 4.55 billion years in this part of our galaxy. 相似文献
129.
B. Ragent C. A. Privette P. Avrin J. G. Waring C. E. Carlston T. C. D. Knight J. P. Martin 《Space Science Reviews》1992,60(1-4):179-201
The objective of the Nephelometer Experient aboard the Probe of the Galileo mission is to explore the vertical structure and microphysical properties of the clouds and hazes in the atmosphere of Jupiter along the descent trajectory of the Probe (nominally from 0.1 to > 10 bars). The measurements, to be obtained at least every kilometer of the Probe descent, will provide the bases for inferences of mean particle sizes, particle number densities (and hence, opacities, mass densities, and columnar mass loading) and, for non-highly absorbing particles, for distinguishing between solid and liquid particles. These quantities, especially the location of the cloud bases, together with other quantities derived from this and other experiments aboard the Probe, will not only yield strong evidence for the composition of the particles, but, using thermochemical models, for species abundances as well. The measurements in the upper troposphere will provide ground truth data for correlation with remote sensing instruments aboard the Galileo Orbiter vehicle. The instrument is carefully designed and calibrated to measure the light scattering properties of the particulate clouds and hazes at scattering angles of 5.8°, 16°, 40°, 70°, and 178°. The measurement sensitivity and accuracy is such that useful estimates of mean particle radii in the range from about 0.2 to 20 can be inferred. The instrument will detect the presence of typical cloud particles with radii of about 1.0 , or larger, at concentrations of less than 1 cm3.Deceased. 相似文献
130.
Profiles of the visible Fe X (6374 Å) coronal emission line as a function of height above the limb were obtained out to 1.16 solar radii in a coronal hole using the NSO/Sacramento Peak Observatory Coronagraph, Universal Spectrograph and a CCD camera. These are the first coronal line profiles obtained as a function of height in a coronal hole from the ground. Analysis of the line widths suggests a large component of nonthermal broadening which increases with height ranging from 40 to 60 km/s, depending upon the assumed temperature or thermal component of the profile. 相似文献