全文获取类型
收费全文 | 3315篇 |
免费 | 633篇 |
国内免费 | 490篇 |
专业分类
航空 | 1990篇 |
航天技术 | 795篇 |
综合类 | 437篇 |
航天 | 1216篇 |
出版年
2024年 | 10篇 |
2023年 | 42篇 |
2022年 | 112篇 |
2021年 | 149篇 |
2020年 | 135篇 |
2019年 | 106篇 |
2018年 | 123篇 |
2017年 | 143篇 |
2016年 | 129篇 |
2015年 | 162篇 |
2014年 | 193篇 |
2013年 | 183篇 |
2012年 | 209篇 |
2011年 | 223篇 |
2010年 | 270篇 |
2009年 | 277篇 |
2008年 | 202篇 |
2007年 | 192篇 |
2006年 | 155篇 |
2005年 | 150篇 |
2004年 | 89篇 |
2003年 | 115篇 |
2002年 | 156篇 |
2001年 | 105篇 |
2000年 | 106篇 |
1999年 | 101篇 |
1998年 | 68篇 |
1997年 | 79篇 |
1996年 | 65篇 |
1995年 | 71篇 |
1994年 | 53篇 |
1993年 | 36篇 |
1992年 | 46篇 |
1991年 | 35篇 |
1990年 | 26篇 |
1989年 | 17篇 |
1988年 | 18篇 |
1987年 | 8篇 |
1986年 | 10篇 |
1985年 | 15篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 9篇 |
1981年 | 19篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1976年 | 2篇 |
1974年 | 3篇 |
1965年 | 1篇 |
排序方式: 共有4438条查询结果,搜索用时 312 毫秒
981.
982.
983.
984.
E. V. Babkin M. Yu. Belyaev N. I. Efimov V. V. Sazonov V. M. Stazhkov 《Cosmic Research》2001,39(1):23-37
The results of determining the rotational motion of the Mir orbital station are presented for four long segments of its unmanned uncontrolled flight in 1999–2000. The determination was carried out using the data of onboard measurements of the Earth's magnetic field intensity. These data, taken for a time interval of several hours, were jointly processed by the least squares method with the help of integration of the equations of station motion relative to its center of mass. As a result of this processing, the initial conditions of motion and the parameters of the mathematical model used were evaluated. The technique of processing is verified using the telemetry data on angular velocity of the station and its attitude parameters. Two types of motion were applied on the investigated segments. One of them (three segments) presents a rotation around the axis of the minimum moment of inertia. This axis executes small oscillations with respect to a normal to the orbit plane. Such a motion was used for the first time on domestic manned orbital complexes. The second type of motion begins with a biaxial rotation which, in a few weeks, goes over into a motion very similar to the rotation around the normal to the orbit plane, but around the axis of the maximum moment of inertia. 相似文献
985.
本文介绍一种遥感相机自动调焦技术的实验研究结果,实验表明,差分式对比传递函数法调焦,具有调焦精度高,调焦速度快,受像移影响不明显,适应性好等优点。 相似文献
986.
987.
988.
丁羟推进剂粘接体系中的组分迁移 总被引:3,自引:1,他引:3
用浸泡增重法研究了衬层、绝热层对DOS和T27的吸收能力,用气相色谱仪研究了HTPB推进剂/HTPB衬层/EPDM绝热层粘接体系中DOS、T27和GFP的迁移。结果表明,HTPB衬层和EPDM绝热层对DOS和T27的吸收能力很强;粘合剂的极性增大或交联密度升高,衬层对DOS、T27的吸收能力下降,但粘合剂的极性增大,对衬层与HTPB推进剂的界面粘接性能不利;在HTPB推进剂/HTPB衬层/EPDM绝热层粘接体系中,DOS、T27或GFP的迁移平衡浓度为粘合剂相的平衡浓度。 相似文献
989.
990.
Sazonov V. V. Chebukov S. Yu. Abrashkin V. I. Kazakova A. E. Zaitsev A. S. 《Cosmic Research》2004,42(2):178-193
We analyze the microacceleration measurements carried out onboard the Foton-11 satellite with the three-component accelerometer BETA. The microaccelerations were recorded virtually throughout the entire orbital flight of the Foton-11 satellite. The data obtained were analyzed in the following way. First they were used to determine the actual rotational motion of the satellite for several arbitrarily selected time intervals 4 h long. This problem was solved by constructing the approximation of the microacceleretation low-frequency component (previously determined from the data) by its calculated analog computed along the solutions to differential equations of rotational motion of the satellite. The approximation was made by the least squares method. As a result, those mathematical model parameters and the solutions to equations of motion were found that gave the best consistency of the microacceleretation low-frequency component and its calculated analog. Then the spectral analysis of the low-frequency component and its calculated analog was made. It was shown that, although basic harmonics of these functions coincided sufficiently well, some harmonics of the low-frequency component failed to be interpreted in terms of the satellite's rotational motion. 相似文献