全文获取类型
收费全文 | 7912篇 |
免费 | 17篇 |
国内免费 | 24篇 |
专业分类
航空 | 3532篇 |
航天技术 | 2727篇 |
综合类 | 25篇 |
航天 | 1669篇 |
出版年
2021年 | 81篇 |
2019年 | 48篇 |
2018年 | 229篇 |
2017年 | 154篇 |
2016年 | 130篇 |
2015年 | 56篇 |
2014年 | 201篇 |
2013年 | 245篇 |
2012年 | 241篇 |
2011年 | 370篇 |
2010年 | 264篇 |
2009年 | 384篇 |
2008年 | 434篇 |
2007年 | 251篇 |
2006年 | 179篇 |
2005年 | 216篇 |
2004年 | 212篇 |
2003年 | 245篇 |
2002年 | 173篇 |
2001年 | 267篇 |
2000年 | 144篇 |
1999年 | 176篇 |
1998年 | 206篇 |
1997年 | 125篇 |
1996年 | 191篇 |
1995年 | 224篇 |
1994年 | 200篇 |
1993年 | 134篇 |
1992年 | 163篇 |
1991年 | 54篇 |
1990年 | 58篇 |
1989年 | 158篇 |
1988年 | 66篇 |
1987年 | 66篇 |
1986年 | 77篇 |
1985年 | 216篇 |
1984年 | 168篇 |
1983年 | 122篇 |
1982年 | 136篇 |
1981年 | 238篇 |
1980年 | 59篇 |
1979年 | 50篇 |
1978年 | 54篇 |
1977年 | 51篇 |
1975年 | 56篇 |
1974年 | 48篇 |
1973年 | 40篇 |
1972年 | 36篇 |
1971年 | 38篇 |
1970年 | 40篇 |
排序方式: 共有7953条查询结果,搜索用时 0 毫秒
171.
S. A. Naroenkov 《Cosmic Research》2010,48(5):455-458
Numerous discoveries of asteroids unknown earlier led to a multiple increase in the number of information on small bodies of the Solar System. Huge volumes of information accumulated and obtained at observations of objects approaching the Earth’s orbit require storing and prompt processing, presenting more and more possibilities for studying distributions of small bodies of the Solar System and ways of their evolution. That is why development of information systems which will contain large volumes of data on small bodies of the Solar System and facilities for processing these data is actual and promising direction of activity. 相似文献
172.
A method for approximate analytical optimization of low-thrust transfers, described in [1] and based on linearization of the equations of motion, is considered. A more precise method of reducing the errors due to linearization is suggested. The method of optimization is generalized for the case of a mission to several celestial bodies. 相似文献
173.
Malakhov A. V. Mitrofanov I. G. Litvak M. L. Sanin A. B. Golovin D. V. Djachkova M. V. Nikiforov S. Yu. Anikin A. A. Lisov D. I. Lukyanov N. V. Mokrousov M. I. Shvetsov V. N. Timoshenko G. N. 《Cosmic Research》2022,60(1):23-37
Cosmic Research - The article presents results of ground calibrations of the FREND neutron telescope installed onboard the TGO spacecraft of the Russian-European ExoMars project. The main goal of... 相似文献
174.
Cosmic Research - We have considered procedure and results of the experimental study for spectral characteristics of self emission from laboratory models of electric thrusters with closed electron... 相似文献
175.
Space sustainability is emerging as a core element of national policy and international initiatives. At this time, however, a coherent strategy and supporting policies have not been developed. To initiate a conversation to develop such a strategy, the authors have applied the principles developed by Elinor Ostrom for terrestrial common-pool resource (CPR) governance to near-Earth orbit in space. A concern arises as to whether Ostrom's eight principles are a good “fit” for application to space CPR because of the unique physical characteristics of space and the legal underpinnings of our presence there. This commentary will address selected issues raised by Weeden and Chow, and suggest alternative ways to approach near-Earth orbit sustainability. 相似文献
176.
The 2007 US National Research Council Decadal Survey for Earth Science and Applications from Space was the first consensus perspective produced by the US Earth Science community of the relative priorities among a sequence of 17 satellite missions over the course of the next decade. However, the Decadal Survey only captured the perspective of the science community, leading to questions about the inclusion of broader priorities from constituent communities and stakeholders. We present a stakeholder value network analysis for the NASA/NOAA Earth Observation Program. The analysis includes a rigorous articulation of the needs and objectives of 13 major stakeholders and a complete stakeholder value network with 190 individual “value flows” that capture the interactions between all the stakeholders. It produces a novel stakeholder map, graphically indicating the outputs most likely to create a lasting Earth Science program. The most important value loops and program outputs are used to derive a set of high-level program goals that suggest what NASA and NOAA should do, as well as how they should conduct business. The analysis concludes that international partnerships represent a strong potential partner for certain science missions with greater potential value delivery than currently-prioritized efforts with defense stakeholders and concludes that weather and land-use missions, in addition to climate missions, should be given highest priority; water, human health, and solid Earth missions should be given lower priority based on each science category's potential for delivering value to the entire stakeholder network. 相似文献
177.
V. Gushin D. Shved A. Vinokhodova G. Vasylieva I. Nitchiporuk B. Ehmann L. Balazs 《Acta Astronautica》2012
“Mars-105” experiment was executed in March–July 2009 in Moscow, at the Institute for Bio-Medical Problems (IBMP) with participation of European Space Agency (ESA) to simulate some specific conditions of future piloted Mars mission. In the last 35 days of isolation, in order to simulate autonomous flight conditions, some serious restrictions were established for the crew resupply and communication with Mission Control (MC). The objective of the study was to investigate psychophysiological and behavioral aspects (communication) of adaptation during this period of “high autonomy”. We used computerized analysis of the crew written daily reports to calculate the frequencies of utilization of certain semantic units, expressing different psychological functions. To estimate the level of psycho-physiological stress, we measured the concentration of urinal cortisol once in two weeks. To investigate psycho-emotional state, we used the questionnaire SAN, estimating Mood, Activity and Health once in two weeks.During the simulation of autonomous flight, we found out the different tendencies of communicative behavior. One group of subjects demonstrated the tendency to “activation and self-government” under “high autonomy” conditions. The other subjects continued to use communicative strategy that we called “closing the communication channel”. “Active” communication strategy was accompanied by increasing in subjective scores of mood and activity. The subjects, whose communication strategy was attributed as “closing”, demonstrated the considerably lower subjective scores of mood and activity. Period of high autonomy causes specific changes in communication strategies of the isolated crew. 相似文献
178.
This paper completes the study of optimal transfers with constraints imposed on the thrust vector direction that was opened by paper [1]. The linear inhomogeneous and homogeneous constraints on the thrust direction are considered (specified either by equalities or inequalities), as well as mixed constraints. Some examples of the constraints are presented. A modified method of the transporting trajectory is applied in order to find the optimal transfer under the linear constraints on the thrust direction. This method also gives the necessary condition for a transfer possibility at a given constraint on the thrust direction. A numerical example is considered, in which the propellant consumption is analyzed for the cases of transfers with and without constraints. 相似文献
179.
A correlative analysis has been made between cosmic ray intensity and solar activity (sunspot numbers) during high amplitude days for the period 1991–1995. The high amplitude days with the time of maximum in the corotational/azimuthal direction do not indicate any significant correlation with solar activity. The diurnal amplitude significantly remains constant and high (0.5%) during the entire period. Our observations suggest that the direction of the anisotropy of high amplitude anisotropic wave train events contribute significantly to the short-term behavior of the cosmic ray diurnal anisotropy. The correlation coefficient is found to remain positive during solar activity maximum for all the high amplitude anisotropic wave train events. 相似文献
180.
A. G. Tuchin 《Cosmic Research》2008,46(6):506-516
The problem of selecting quasi-synchronous orbits of a spacecraft around Phobos is considered. These quasi-synchronous orbits are far (with respect to the Hill’s sphere) quasi-satellite orbits with retrograde rotation in the restricted three body problem. The orbit should pass through a given point at a specified time instant. It should also possess a property of minimum distance from the Phobos surface at every passage above the region of planned landing. The equations of dynamics are represented in the form describing the orbit as a combination of motions in two drifting ellipses, inner and outer ellipses. The center of the outer ellipse is located on the inner ellipse. A formula is derived that relates averaged values of half-axes of the inner and outer ellipses. It is used for construction of the first approximation of numerically designed orbit, which makes it possible to simplify and speed up the computing process. The tables of initial conditions obtained as a result of calculations are presented. 相似文献