全文获取类型
收费全文 | 4314篇 |
免费 | 6篇 |
国内免费 | 12篇 |
专业分类
航空 | 1856篇 |
航天技术 | 1594篇 |
综合类 | 13篇 |
航天 | 869篇 |
出版年
2021年 | 32篇 |
2019年 | 20篇 |
2018年 | 99篇 |
2017年 | 81篇 |
2016年 | 73篇 |
2015年 | 29篇 |
2014年 | 108篇 |
2013年 | 119篇 |
2012年 | 111篇 |
2011年 | 179篇 |
2010年 | 133篇 |
2009年 | 212篇 |
2008年 | 265篇 |
2007年 | 132篇 |
2006年 | 92篇 |
2005年 | 113篇 |
2004年 | 129篇 |
2003年 | 160篇 |
2002年 | 89篇 |
2001年 | 173篇 |
2000年 | 74篇 |
1999年 | 115篇 |
1998年 | 121篇 |
1997年 | 89篇 |
1996年 | 103篇 |
1995年 | 126篇 |
1994年 | 124篇 |
1993年 | 53篇 |
1992年 | 89篇 |
1991年 | 29篇 |
1990年 | 39篇 |
1989年 | 87篇 |
1988年 | 33篇 |
1987年 | 51篇 |
1986年 | 36篇 |
1985年 | 129篇 |
1984年 | 74篇 |
1983年 | 69篇 |
1982年 | 87篇 |
1981年 | 128篇 |
1980年 | 40篇 |
1979年 | 30篇 |
1978年 | 29篇 |
1977年 | 30篇 |
1976年 | 24篇 |
1975年 | 32篇 |
1974年 | 26篇 |
1973年 | 16篇 |
1972年 | 19篇 |
1969年 | 15篇 |
排序方式: 共有4332条查询结果,搜索用时 93 毫秒
1.
The simplest version of the method of detecting the single molecular scattering field based on the polarization measurements of the twilight sky background by all-sky cameras has been considered. The method can be used during transitive twilight (with solar zenith angles of 94°–98°), when effective single scattering occurs in the upper stratosphere and lower mesosphere. The long-term measurements conducted using this method in the Moscow region and Apatity make it possible to determine the temperature of these atmospheric layers and estimate the contribution and properties of multiple scattering during the transitive twilight. 相似文献
2.
A. V. Bogatyi R. V. El’nikov I. P. Nazarenko G. A. Popov S. A. Semenikhin 《Russian Aeronautics (Iz VUZ)》2018,61(3):445-451
The paper presents the research results of the effect of a capacitor energy storage device configuration on the specific characteristics of advanced modern propulsion systems based on the ablative pulsed plasma thrusters (APPT). These thrusters are designed to perform specific tasks within the small spacecrafts with the onboard power capacity up to 200 W. 相似文献
3.
4.
E. R. Muslimov E. Hugot M. Ferrari T. Behaghel N. K. Pavlycheva 《Russian Aeronautics (Iz VUZ)》2018,61(1):1-7
The possibility of constructing an optical scheme of a telescope for a small satellite based on mirrors with freeform surfaces and a curved photodetector is considered. It is shown that the use of a new element base allows the effective area of the main mirror to be maximized and the field of view up to 9.4 times to be increased in comparison with the classical scheme of the Ritchey–Chretien scheme in ensuring the high image quality. 相似文献
5.
Giulio L. Marco B. Aldo F. Domenico T.P. Mario M. 《Aerospace and Electronic Systems Magazine, IEEE》2002,17(9):22-27
This paper reviews the results of the thermal and static analysis of small motor aerospace technology (SMART) propulsion system, constituted of a microthrusters array realised by MEMS technology on silicon wafers. This system has been studied using FEM (NASTRAN) and the results have been verified by the electro-thermic analogy and the FDM method, using, respectively, SPICE and MATLAB codes. The simulation results demonstrated the feasibility of SMART systems for aerospace applications such as attitude control and deorbiting missions for small satellite station-keeping. A theoretical impulse of 20 mNs has been calculated for the SMART system. 相似文献
6.
L O Bjorn S Widell T Wang 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2002,30(6):1557-1562
Plants have evolved under the influence of UV-B radiation and have acquired systems for monitoring it and investing appropriate resources for protection against it, i.e., filters, quenchers of radicals and reactive oxygen species, and repair systems. An hypothesis for how plants monitor radiation has been presented. 相似文献
7.
This study introduces a field oriented controlled (FOC) induction machine based flywheel energy storage (FES) system fed from a 20 kHz high frequency (HF) ac link and pulse density modulated (PDM) Converter. The feasibility of FES system is investigated both in software and hardware and is demonstrated successfully in both cases. The investigated system offers a good potential as a temporary energy storage system for various applications from automobile industry to aerospace applications. 相似文献
8.
R. Vilhena de Moraes K. T. Fitzgibbon M. Konemba 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1995,16(12)
Due to the characteristics of their orbits the GPS satellites are submitted to the following main perturbations: terrestrial gravitational field, luni-solar gravitational attraction and solar radiation pressure (including the effects of the Earth's shadow). An additional perturbation arises due to the 2:1 commensurability of the orbital period of the satellite with the period of the Earth's rotation. An analytical theory is briefly presented to solve the equations of motion including the previously mentioned effects. The analytical solution, based on the Lie-Hori method, is compared with a numerical integration of the equations. 相似文献
9.
10.
S I Bartsev V V Mezhevikin V A Okhonin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1996,18(1-2):201-204
Any attempt to create LSS for practical applications must take into account the possibility of castastrophic consequences if the problem of LSS reliability and stability is not solved. An integrated conception of CELSS studies development as a possible way to increase its reliability is considered. The BIOS-4 facility project is developed in the context of the conception. Three principles of highly effective experimental CELSS facility design are proposed. Some details of BIOS-4 design and its exploitation features are presented. 相似文献