全文获取类型
收费全文 | 17604篇 |
免费 | 36篇 |
国内免费 | 124篇 |
专业分类
航空 | 9820篇 |
航天技术 | 5135篇 |
综合类 | 242篇 |
航天 | 2567篇 |
出版年
2021年 | 157篇 |
2018年 | 189篇 |
2016年 | 156篇 |
2014年 | 432篇 |
2013年 | 514篇 |
2012年 | 408篇 |
2011年 | 569篇 |
2010年 | 398篇 |
2009年 | 748篇 |
2008年 | 775篇 |
2007年 | 355篇 |
2006年 | 420篇 |
2005年 | 368篇 |
2004年 | 417篇 |
2003年 | 500篇 |
2002年 | 464篇 |
2001年 | 535篇 |
2000年 | 343篇 |
1999年 | 442篇 |
1998年 | 402篇 |
1997年 | 306篇 |
1996年 | 367篇 |
1995年 | 439篇 |
1994年 | 387篇 |
1993年 | 352篇 |
1992年 | 291篇 |
1991年 | 251篇 |
1990年 | 234篇 |
1989年 | 380篇 |
1988年 | 202篇 |
1987年 | 233篇 |
1986年 | 224篇 |
1985年 | 637篇 |
1984年 | 511篇 |
1983年 | 405篇 |
1982年 | 487篇 |
1981年 | 608篇 |
1980年 | 244篇 |
1979年 | 183篇 |
1978年 | 189篇 |
1977年 | 144篇 |
1976年 | 156篇 |
1975年 | 185篇 |
1974年 | 180篇 |
1973年 | 161篇 |
1972年 | 188篇 |
1971年 | 148篇 |
1970年 | 143篇 |
1969年 | 147篇 |
1967年 | 142篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
441.
D. B. Dobritsa 《Cosmic Research》2014,52(3):229-234
In this paper, the problems of the application and development of models of space debris when designing means of the anti-meteorite spacecraft protection are considered. The developed method enables us to calculate the resistance of design elements based on the conjugation of a modified spatial model of the distribution of space-debris particles and ballistic limit dependences for a calculated element. 相似文献
442.
D. S. Ivanov N. A. Ivlev S. O. Karpenko M. Yu. Ovchinnikov D. S. Roldugin S. S. Tkachev 《Cosmic Research》2014,52(3):205-215
The attitude control system of the Chibis-M microsatellite is described. Results of flight experiments on damping the initial angular velocity (made using magnetorquers) are considered, as well as stabilization in the orbital referece frame, and orientation of solar arrays toward the Sun using reaction wheels. The operation of algorithms of satellite attitude determination on sunlit and shadow segments of the orbit is also under study. The general logic of operation of the attitude control system in automatic mode is presented and discussed. 相似文献
443.
Future piloted missions to explore asteroids, Mars, and other targets beyond the Moon will experience strict limitations on communication between vehicles in space and control centers on Earth. These limitations will require crews to operate with greater autonomy than any past space mission has demonstrated. The Antarctic Search for Meteorites (ANSMET) project, which regularly sends small teams of researchers to remote parts of the southern continent, resembles a space mission in many ways but does not rely upon a control center. It provides a useful crew autonomy model for planners of future deep space exploration missions. In contrast to current space missions, ANSMET gives the crew the authority to adjust competing work priorities, task assignments, and daily schedules; allows the crew to be the primary monitor of mission progress; demands greater crew accountability for operational errors; requires the crew to make the most of limited communication bandwidth; adopts systems designed for simple operation and failure recovery; and grants the crew a leading role in the selection and stowage of their equipment. 相似文献
444.
This paper describes the experimental and computational analyses of a high velocity aluminum projectile impact on an Al6061-T6 spacecraft inner wall at different oblique angles. Al2017-T4 spherical projectiles of 5.56 mm in diameter and 0.25 g in weight were chosen within the velocity range of 1000±200 m/s due to the limitation of the light gas gun. The energy absorbed was calculated by measuring the velocities before and after impact on the inner wall. The energy absorbed by the wall and the remaining energy carried by the projectile helped to estimate the severity of further damage to inner components. Afterwards, validation was done by using the commercially available software LS-DYNA with a dedicated SPH. On average, a 10% energy absorption difference between experimentation and simulation was found. By using C-SCAN, the damage area proportion of the total inner wall to impact penetration hole area was found to be on average 6%, 26% and 53% greater than the projectile cross sectional area for the oblique angle impacts of 30°, 45°, and 60°, respectively. These findings helped to understand the relationship between the oblique impact event and the damage area on a spacecraft inner wall along with space debris cloud propagation and comparison with experimental results using LS-DYNA. 相似文献
445.
The CIVA-M instrument, a highly integrated infrared/visible microscope for the Rosetta mission (ESA — 2003) is presented. It will enable scientists to study in great detail the composition of the Wirtanen Comet: minerals, organic compounds and ices. A monochromator will illuminate a cometary sample, drilled from the comet sub-surface (≈40cm). An infrared detector will give an image of the sample for each wavelength, from 1 to 4μm with a spectral resolution of 6nm and a spatial resolution of 50 μm. In order to analyze accurately spectra a signal to noise ratio of 50 is needed (for ALBEDO = 0.04). We will use a 128×128 elements photovoltaic mercury cadmium telluride bi-dimensional array working at intermediate temperature (110K to 150K), from the French company SOFRADIR. At such relatively high temperature the critical parameter is the dark current: it limits the exposure time, preventing a high signal to noise ratio. I am in charge of the electronic board, which is the interface between the detector and the on-board processor. Some preliminary results obtained with this board, on a test detector, are then discussed. 相似文献
446.
Presented herein is a concept of an Autonomous Navigation & Guidance System for electrically propelled deep space missions, including hardware configuration, algorithms for autonomous navigation and guidance, and estimates of potential guidance precision and mass consumption. This concept is actually a unified Navigation, Guidance and Attitude Control system. The unification is imposed by strong coupling between the orbital motion and the spacecraft attitude characteristic of low thrust space flights. The sensor set of the system consists of an optical instrument (Coupled Sun Star Tracker), and a block of four vector accelerometers. The propulsion subsystem is a set of nearly parallel Hall thrusters rigidly attached to the spacecraft body. The final stage of data processing is combining the thrust and torque programs and generating power and mass rate shares for every thruster. An end-to-end computer simulation provides guidance accuracy estimates versus the navigation data precision, flight time and available maximum thrust. Terminal guidance errors of a few tens of km in position and a few tens of cm/s in velocities are predicted under plausible assumptions on system parameters. Mass expenditures for the control are typically below one percent of total fuel mass budget. 相似文献
447.
This article presents main scientific and practical results obtained in course of scientific and applied research and experiments on Mir space station. Based on Mir experience, processes of research program formation for the Russian Segment of the ISS are briefly described. The major trends of activities planned in the frames of these programs as well as preliminary results of increment research programs implementation in the ISS' first missions are also presented. 相似文献
448.
Cosmic Research - An Erratum to this paper has been published: https://doi.org/10.1134/S0010952521120030 相似文献
449.
Kugusheva A. D. Kalegaev V. V. Vlasova N. A. Petrov K. A. Bazilevskaya G. A. Makhmutov V. S. 《Cosmic Research》2021,59(6):446-455
Cosmic Research - The results of an analysis of the space–time characteristics and dynamics of precipitations of magnetospheric electrons with energies in the range from 0.1 to 0.7 MeV are... 相似文献
450.
Cosmic Research - An Erratum to this paper has been published: https://doi.org/10.1134/S0010952521110010 相似文献