全文获取类型
收费全文 | 8149篇 |
免费 | 13篇 |
国内免费 | 17篇 |
专业分类
航空 | 4001篇 |
航天技术 | 2702篇 |
综合类 | 194篇 |
航天 | 1282篇 |
出版年
2021年 | 67篇 |
2018年 | 152篇 |
2017年 | 95篇 |
2016年 | 98篇 |
2014年 | 174篇 |
2013年 | 203篇 |
2012年 | 221篇 |
2011年 | 306篇 |
2010年 | 196篇 |
2009年 | 353篇 |
2008年 | 397篇 |
2007年 | 208篇 |
2006年 | 170篇 |
2005年 | 202篇 |
2004年 | 195篇 |
2003年 | 250篇 |
2002年 | 244篇 |
2001年 | 317篇 |
2000年 | 145篇 |
1999年 | 192篇 |
1998年 | 238篇 |
1997年 | 166篇 |
1996年 | 192篇 |
1995年 | 252篇 |
1994年 | 240篇 |
1993年 | 140篇 |
1992年 | 185篇 |
1991年 | 92篇 |
1990年 | 84篇 |
1989年 | 191篇 |
1988年 | 83篇 |
1987年 | 93篇 |
1986年 | 80篇 |
1985年 | 220篇 |
1984年 | 185篇 |
1983年 | 159篇 |
1982年 | 181篇 |
1981年 | 240篇 |
1980年 | 89篇 |
1979年 | 72篇 |
1978年 | 79篇 |
1977年 | 52篇 |
1976年 | 60篇 |
1975年 | 65篇 |
1974年 | 61篇 |
1973年 | 46篇 |
1972年 | 67篇 |
1971年 | 64篇 |
1970年 | 44篇 |
1969年 | 48篇 |
排序方式: 共有8179条查询结果,搜索用时 140 毫秒
81.
The force exerted by the solar radiation, though very small in magnitude, produces significant effects, especially in the case of high altitude satellites. The solar radiation pressure represents one freely available environmental force that may be put to use for various purposes. This may lead to enhancement of the life of the satellite since it consumes a very nominal amount of on-board energy. The advantages offered by the solar radiation pressure have drawn the attention of several researchers. Various controllers were proposed for many space missions, particularly for attitude control and stabilization of satellites. A controller for achieving large angle pitch attitude maneuver is described. The proposed control law is very simple in its form and requires a minimum number of on-board computations. Varieties of cases are tried and the effect of various parameters is studied 相似文献
82.
D. L. Judge H. S. Ogawa D. R. McMullin P. Gangopadhyay J. M. Pap 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2002,29(12):502-1968
The SOHO Solar EUV Monitor has been in operation since December 1995 onboard the SOHO spacecraft. This instrument is a highly stable transmission grating solar extreme ultraviolet spectrometer. It has made nearly continuous full disk solar irradiance measurements both within an 8 nm bandpass centered at 30.4 nm and throughout the 0.1 to 50 nm solar flux region since launch. The 30.4 nm flux, the 0.1 to 50 nm flux and the extracted soft X-ray (0.1 to 5 nm) flux are presented and compared with the behavior of solar proxies. 相似文献
83.
An electric vehicle (EV) energy management system (EMS) developed to accurately predict and extend the usable driving range and the life of the battery pack is discussed. The EMS monitors and records battery state of charge, vehicle performance, power consumption of key components, and driver's actions. Convenient drive inputs in conjunction with memorized energy consumption profiles allow accurate prediction of driving range and selection of appropriate recharging profiles. EV range extension is accomplished by identifying inefficient use of energy, resulting in EMS modification of energy usage by offending subsystems or EMS suggestion to the driver of improved driving habits or vehicle use. Factors affecting the accuracy of range prediction and the amount of range extension are described 相似文献
84.
R. Wickramatunga 《Space Policy》1991,7(1)
Parties to the Registration Convention are committed to providing the United Nations with certain information about objects they launch into space. This report describes the categories of information required, outlines the inadequacies of the present Register and suggests modifications. 相似文献
85.
86.
G Horneck R Facius G Reitz P Rettberg C Baumstark-Khan R Gerzer 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2003,31(1):87-95
Human missions to Mars are planned to happen within this century. Activities associated therewith will interact with the environment of Mars in two reciprocal ways: (i) the mission needs to be protected from the natural environmental elements that can be harmful to human health, the equipment or to their operations; (ii) the specific natural environment of Mars should be protected so that it retains its value for scientific and other purposes. The following environmental elements need to be considered in order to protect humans and the equipment on the planetary surface: (i) cosmic ionizing radiation, (ii) solar particle events; (iii) solar ultraviolet radiation; (iv) reduced gravity; (v) thin atmosphere; (vi) extremes in temperatures and their fluctuations; and (vii) surface dust. In order to protect the planetary environment, the requirements for planetary protection as adopted by COSPAR for lander missions need to be revised in view of human presence on the planet. Landers carrying equipment for exobiological investigations require special consideration to reduce contamination by terrestrial microorganisms and organic matter to the greatest feasible extent. Records of human activities on the planet's surface should be maintained in sufficient detail that future scientific experimenters can determine whether environmental modifications have resulted from explorations. 相似文献
87.
F. S. Khairullin 《Russian Aeronautics (Iz VUZ)》2009,52(4):480-483
We consider a possibility to apply the method of analyzing the complex-shaped shells, proposed in [1], for determining the
stress strain state of thin shells with a degenerating domain. The results of numerical calculations are presented. 相似文献
88.
A. Sh. Dzhabrailov Yu. V. Klochkov S. S. Marchenko A. P. Nikolaev 《Russian Aeronautics (Iz VUZ)》2007,50(2):115-120
We demonstrate that it is possible to express each component of the displacement vector for the interior point of the finite element (FE) through all components of nodal unknowns in curvilinear coordinates. The effectiveness of the valid technique of vector approximation for displacement fields has been verified on an example. 相似文献
89.
D. Koschny V. Dhiri K. Wirth J. Zender R. Solaz R. Hoofs R. Laureijs T.-M Ho B. Davidsson G. Schwehm 《Space Science Reviews》2007,128(1-4):167-188
ESA’s Rosetta mission was launched in March 2004 and is on its way to comet 67P/Churyumov-Gerasimenko, where it is scheduled
to arrive in summer 2014. It comprises a payload of 12 scientific instruments and a Lander. All instruments are provided by
Principal Investigators, which are responsible for their operations.
As for most ESA science missions, the ground segment of the mission consists of a Mission Operations Centre (MOC) and a Science
Operations Centre (SOC). While the MOC is responsible for all spacecraft-related aspects and the final uplink of all command
timelines to the spacecraft, the scientific operations of the instruments and the collection of the data and ingestion into
the Planetary Science Archive are coordinated by the SOC. This paper focuses on the tasks of the SOC and in particular on
the methodology and constraints to convert the scientific goals of the Rosetta mission to operational timelines. 相似文献
90.
The characteristics of the insulator wear process in the discharge chamber of a stationary plasma thruster (SPT) are analyzed. The results of studying the erosion resistance to ionic spraying of different ceramic compositions are presented. It is shown experimentally that the integral characteristics (the value of thrust and thrust efficiency) as well as the SPT lifetime can be improved in changing from the conventional hot-pressed boron silicate (BN + SiO2) ceramics to the BN + Si3N4 ceramic compositions. 相似文献