全文获取类型
收费全文 | 6527篇 |
免费 | 11篇 |
国内免费 | 13篇 |
专业分类
航空 | 2851篇 |
航天技术 | 2131篇 |
综合类 | 26篇 |
航天 | 1543篇 |
出版年
2021年 | 55篇 |
2019年 | 32篇 |
2018年 | 215篇 |
2017年 | 167篇 |
2016年 | 144篇 |
2015年 | 59篇 |
2014年 | 154篇 |
2013年 | 204篇 |
2012年 | 195篇 |
2011年 | 305篇 |
2010年 | 254篇 |
2009年 | 344篇 |
2008年 | 361篇 |
2007年 | 250篇 |
2006年 | 134篇 |
2005年 | 194篇 |
2004年 | 187篇 |
2003年 | 199篇 |
2002年 | 145篇 |
2001年 | 206篇 |
2000年 | 86篇 |
1999年 | 126篇 |
1998年 | 151篇 |
1997年 | 104篇 |
1996年 | 102篇 |
1995年 | 178篇 |
1994年 | 169篇 |
1993年 | 90篇 |
1992年 | 106篇 |
1991年 | 40篇 |
1990年 | 58篇 |
1989年 | 100篇 |
1988年 | 40篇 |
1987年 | 40篇 |
1986年 | 51篇 |
1985年 | 177篇 |
1984年 | 150篇 |
1983年 | 125篇 |
1982年 | 108篇 |
1981年 | 208篇 |
1980年 | 49篇 |
1979年 | 45篇 |
1978年 | 45篇 |
1977年 | 41篇 |
1976年 | 40篇 |
1975年 | 44篇 |
1974年 | 36篇 |
1973年 | 34篇 |
1972年 | 50篇 |
1971年 | 27篇 |
排序方式: 共有6551条查询结果,搜索用时 0 毫秒
31.
Kottaras G. Sarris E. Paschalidis B. Stamatopoulos N. Paschalidis N. 《IEEE transactions on aerospace and electronic systems》2004,40(3):862-878
Several design and testing aspects of the TRIO smart sensor data acquisition chip, developed by JHU/APL for NASA spacecraft applications are presented. TRIO includes a 10 bit self-corrected analog-to-digital converter (ADC), 16/32 analog inputs, a front end multiplexer with selectable aquisition time, a current source, memory, serial and parallel bus, and control logic. So far TRIO is used in many missions including Contour, Messenger, Stereo, Pluto, and the generic JPL X2000 spacecraft bus. 相似文献
32.
V. Koblik E. Polyakhova L. Sokolov A. Shmyrov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2002,29(12):4431-2088
We present results of numerical simulations of trajectories of a space probe with a flat solar sail which moves from a circular Earth orbit to near-Sun regions. We consider the upper limit of the sail temperature as the basic restriction. We also examine the planar (ecliptic) solar sail transfer with gravity-assist flybys around planets. 相似文献
33.
34.
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
35.
The governments’ priority and budgets for space activities are steadily decreasing and the importance of space activities is not any longer reaching the front pages of the newspaper, as in the 1960s. On the other hand in Europe the people, at large, have shown an important interest and support for space activities. A contribution to bridge the gap between decreasing funding and important support of citizen can come from teaching space policy in universities as well as in special workshops for government, industrial and military circles. The paper will outline a course that fulfils this goal. 相似文献
36.
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
37.
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
38.
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
39.
A novel stochastic optimal control guidance law is presented for a missile with bounded acceleration. The nonlinear optimal guidance law (NOGL) is obtained by numerically solving the stochastic optimization problem. Since the certainty equivalence principle is not valid in the investigated problem, the resulting NOGL depends on the conditional probability density function of the estimated states. It is shown that the NOGL is also nonlinear in the estimated zero effort miss distance, and that the probability density function of the miss distance is non-Gaussian. The dependence of the new guidance law on the acceleration limit is investigated and it is shown that only for an extremely large acceleration limit does the proposed guidance law degenerate to the classical optimal linear one 相似文献
40.
Although the elemental composition in all parts of the solar photosphere appears to be the same this is clearly not the case
with the solar upper atmosphere (SUA). Spectroscopic studies show that in the corona elemental composition along solar equatorial
regions is usually different from polar regions; composition in quiet Sun regions is often different from coronal hole and
active region compositions and the transition region composition is frequently different from the coronal composition along
the same line of sight. In the following two issues are discussed. The first involves abundance ratios between the high-FIP
O and Ne and the low-FIP Mg and Fe that are important for meaningful comparisons between photospheric and SUA compositions
and the second involves a review of composition and time variability of SUA plasmas at heights of 1.0≤h≤1.5R
⊙. 相似文献