全文获取类型
收费全文 | 6493篇 |
免费 | 635篇 |
国内免费 | 482篇 |
专业分类
航空 | 3678篇 |
航天技术 | 1728篇 |
综合类 | 432篇 |
航天 | 1772篇 |
出版年
2023年 | 42篇 |
2022年 | 108篇 |
2021年 | 158篇 |
2020年 | 130篇 |
2019年 | 119篇 |
2018年 | 272篇 |
2017年 | 262篇 |
2016年 | 172篇 |
2015年 | 185篇 |
2014年 | 231篇 |
2013年 | 235篇 |
2012年 | 280篇 |
2011年 | 403篇 |
2010年 | 428篇 |
2009年 | 470篇 |
2008年 | 419篇 |
2007年 | 359篇 |
2006年 | 198篇 |
2005年 | 249篇 |
2004年 | 170篇 |
2003年 | 201篇 |
2002年 | 200篇 |
2001年 | 207篇 |
2000年 | 149篇 |
1999年 | 185篇 |
1998年 | 152篇 |
1997年 | 139篇 |
1996年 | 126篇 |
1995年 | 159篇 |
1994年 | 150篇 |
1993年 | 78篇 |
1992年 | 106篇 |
1991年 | 56篇 |
1990年 | 54篇 |
1989年 | 73篇 |
1988年 | 38篇 |
1987年 | 43篇 |
1986年 | 29篇 |
1985年 | 88篇 |
1984年 | 48篇 |
1983年 | 49篇 |
1982年 | 63篇 |
1981年 | 92篇 |
1980年 | 28篇 |
1979年 | 26篇 |
1978年 | 25篇 |
1977年 | 19篇 |
1976年 | 16篇 |
1975年 | 18篇 |
1972年 | 18篇 |
排序方式: 共有7610条查询结果,搜索用时 15 毫秒
21.
We present an algorithm for calculating the shells of revolution with the branching meridian using the triangular finite elements, the rigidity matrices of which are formed based on the vector method of displacement interpolation [1]. The correct kinematic and static conditions of shell conjugation on the line of their coupling have been developed. The shell structure consisting of a cylinder and adjacent shells is calculated under various conditions of support. 相似文献
22.
I. S. Akhmed’yanov 《Russian Aeronautics (Iz VUZ)》2009,52(4):383-389
The application of the quadrature method [1] to analyzing the shells of revolution under symmetrical loading relative to the
zero meridian is considered. The method can be treated as a generalization of the method presented in [2] to solve the Volterra
integral equation of the second kind. 相似文献
23.
以小车式起落架为例,利用ADAMS/Airc- raft建立了起落架滑跑试验仿真模型.给出了起落架滑跑运动方程,并进行了滑跑试验仿真分析。仿真结果与理论要求对比具有较好的一致性。 相似文献
24.
A problem of determining a shape of the airfoil being streamlined by a potential incompressible inviscid flow is solved by
the successive approximation method using a specified chord velocity diagram. It is shown that a closed airfoil that possesses
a specified chord velocity diagram can be constructed with a sufficient accuracy; if the chord diagram is unsuccessfully specified,
the closed airfoil may prove to be not univalent, that is, physically unrealizable. 相似文献
25.
Garenaux K. Merlet T. Alouini M. Lopez J. Vodjdani N. Boula-Picard R. Fourdin C. Chazelas J. 《Aerospace and Electronic Systems Magazine, IEEE》2007,22(2):3-8
Radar systems require transmission of very high purity signals. Photonics is now mature enough to achieve analog transmission with very low noise, strong immunity, and wide-bandwidth even in harsh environments. We present our recent developments of optimized optical links dedicated to radar and multifunction systems 相似文献
26.
Manufacturers are increasingly offering Ethernet connectivity on their test instruments. An additional benefit of this connection method is the ease of conversion to wireless connectivity. This paper describes the Ethernet interface used in the remote control of a RF power amplifier and describes the conversion to wireless connection. 相似文献
27.
28.
Stability of resonance rotation of a satellite with respect to its center of mass in the orbit plane
S. Yu. Sadov 《Cosmic Research》2006,44(2):160-171
The stability of resonance oscillations and rotations of a satellite in the plane of its orbit in the case when the difference of the moments of inertia with respect to the principal axes lying in the orbit plane is small is determined at a given rotation number m by the sign of function Φm(e), introduced by F.L. Chernous’ko in 1963. In this paper, convenient analytical representations of functions Φm(e) are described in the form of integrals and series of Bessel functions regular at e → 1?. Values of Φm(1) are calculated in explicit form. A theorem about the double asymptotic form of functions Φm(e) at m → ∞ and e → 1? is proved by the saddlepoint method. 相似文献
29.
30.
L.B. Tsirulnik T.V. Kuznetsova V.N. Oraevsky 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1997,20(12):2369-2372
A new method of nonlinear spectral analysis (called the method of global minimum: MGM), based on the best presentation (in sense of minimal squares) of a given time data set as a sum of sinusoids whose frequencies, amplitudes and phases are to be determined, has been used to find periodicities in annual Wolf sunspot numbers (W) during the period 1700–1995. The possible future behaviour of the 11-year solar cycle (based on an extrapolation of the calculated model) is also presented. The main characteristics of the 23rd solar cycle are as follows: the W maximum occurs about 2004, with a peak of nearly 220. An unusually large value of W will occur during the 23rd cycle, which should be characterised by the longest maximum, specifically, W will be greater than 100 during the 11-year period from 1997 to 2007. The first sharp rise will occur during the period 1996–1998, the second sharp during 2002–2004. The main features of the 24 year cycle are as follows: the next minimum in W, associated with the 24th solar cycle, should occur in the year 2008 and the maximum in 2014. W is expected to peak at about 180. The minimum value for the 25th year cycle is expected to occur in the year 2019. It is shown that the accuracy of these predictions depends, first of all, on the extrapolation of the hyperlong harmonic of the calculated polyharmonic model fit of observed annual sunspot numbers during the period 1700–1995. The error bars in the definition of the maximum and minimum epochs can be as large as two years. 相似文献