全文获取类型
收费全文 | 6162篇 |
免费 | 18篇 |
国内免费 | 13篇 |
专业分类
航空 | 2929篇 |
航天技术 | 2270篇 |
综合类 | 21篇 |
航天 | 973篇 |
出版年
2021年 | 52篇 |
2019年 | 35篇 |
2018年 | 126篇 |
2017年 | 90篇 |
2016年 | 87篇 |
2015年 | 47篇 |
2014年 | 162篇 |
2013年 | 178篇 |
2012年 | 175篇 |
2011年 | 246篇 |
2010年 | 166篇 |
2009年 | 291篇 |
2008年 | 359篇 |
2007年 | 168篇 |
2006年 | 137篇 |
2005年 | 172篇 |
2004年 | 164篇 |
2003年 | 218篇 |
2002年 | 116篇 |
2001年 | 217篇 |
2000年 | 107篇 |
1999年 | 158篇 |
1998年 | 179篇 |
1997年 | 129篇 |
1996年 | 134篇 |
1995年 | 184篇 |
1994年 | 192篇 |
1993年 | 92篇 |
1992年 | 143篇 |
1991年 | 68篇 |
1990年 | 59篇 |
1989年 | 133篇 |
1988年 | 57篇 |
1987年 | 71篇 |
1986年 | 55篇 |
1985年 | 152篇 |
1984年 | 112篇 |
1983年 | 111篇 |
1982年 | 131篇 |
1981年 | 171篇 |
1980年 | 63篇 |
1979年 | 57篇 |
1978年 | 51篇 |
1977年 | 39篇 |
1976年 | 42篇 |
1975年 | 36篇 |
1974年 | 30篇 |
1973年 | 30篇 |
1972年 | 38篇 |
1969年 | 27篇 |
排序方式: 共有6193条查询结果,搜索用时 15 毫秒
291.
Devajyoti Dutta Sanjay Sharma G.K. Sen B.A.M. Kannan S. Venketswarlu R.M. Gairola J. Das G. Viswanathan 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
By using a Doppler Weather Radar (DWR) at Shriharikota (13.66°N & 80.23°E), an Artificial Neural Network (ANN) based technique is proposed to improve the accuracy of rain intensity estimation. Three spectral moments of a Doppler spectra are utilized as an input data to an ANN. Rain intensity, as measured by the tipping bucket rain gauges around the DWR station, are considered as a target values for the given inputs. Rain intensity as estimated by the developed ANN model is validated by the rain gauges measurements. With the help of a developed technique, reasonable improvement in the estimation of rain intensity is observed. By using the developed technique, root mean square error and bias are reduced in the range of 34–18% and 17–3% respectively, compared to Z–R approach. 相似文献
292.
293.
V. G. Dmitriev V. I. Biryukov O. V. Egorova S. I. Zhavoronok L. N. Rabinskii 《Russian Aeronautics (Iz VUZ)》2017,60(2):169-176
The discretization of the boundary value problem for laminated composite shells is based on the finite difference approach using the regular mesh with the constant grid step and the difference operators of the second order of accuracy. The dynamic relaxation method is proposed for the solution of the nonlinear problem. The evolutionary equations of the dynamic relaxation are constructed, and the optimum parameters of the converging linear iterative process are estimated. 相似文献
294.
This paper presents a brief review of activities in laminar flow control being performed at the Central Aerohydrodynamic Institute named after Prof. N.E. Zhukovsky (TsAGI). These efforts are focused on the improvement of the existing laminar flow control methods and on the development of new ones. The investigations have demonstrated the effectiveness of aircraft surface laminarization applications with the aim of friction drag reduction. The opportunity of considerable delaying of laminar-turbulent transition due to special wing profile geometry and using boundary layer suction and surface cooling has been verified at sub- and supersonic speeds through various wind tunnel testing at TsAGI and during flying laboratory experiments at the Flight Research Institute (LII). The investigations on using hybrid laminar flow control systems for friction drag reduction were also carried out. New techniques of laminar flow control were proposed, in particular, the method of local heating of the wing leading edge, boundary layer laminarization by means of receptivity control, and electrohydrodynamic methods of boundary layer stability control. 相似文献
295.
For an interception strategy of a removable target by a return space vehicle (RSV), we propose a structure of the control law by the aerodynamic efficiency that determines a chain of the three standard trajectories: nosing-up–free flight–nosing-down. A solution of the terminal problem is to determine numerical values of the control parameters that define moments to switch the RSV flight from one standard trajectory to another. 相似文献
296.
An algorithm of analyzing the design parameters for a thin-walled wing from composite material based on the efficient distribution
of structural material between load-carrying elements is described. We consider the problems of convergence acceleration for
the iteration design analysis. Also presented are the examples of determining the design parameters for a superlight aircraft
wing and the rational parameters of the filler in the form of a three-dimensional rod structure. 相似文献
297.
N. D. Akhmetov M. M. Gimadeev V. N. Drulis V. A. Krivosheev T. V. Rzaeva 《Russian Aeronautics (Iz VUZ)》2011,54(1):108-113
A technique for calculating the energy parameters of shock waves at electrical discharge in water is presented for the transition
region of discharge channel expansion using as the base the predetermined characteristics of discharge circuit. The technique
is based on the solution of energy transport equation that is similar in form to that of radiative transfer. The validity
of the presented approach was experimentally verified. 相似文献
298.
The paper describes a device and a technique of forming the information processing algorithms used in the integrated acoustic monitoring system for jet fuel tanks, intended for monitoring the level, density and mass of liquid products. 相似文献
299.
H.S. Ahluwalia J. Jackiewicz 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
The decay phase of the sunspot cycle 23 exhibited two unusual features. First, it lasted too long. Second, the interplanetary magnetic field intensity at earth orbit reached the lowest value since in situ measurements in space began in October 1963. These physical anomalies significantly altered the early forecasts for the sunspot activity parameters for cycle 24, made by several colleagues. We note that there was a significant change in the solar behavior during cycle 22. We discuss the observed trends and their effect on our empirical solar activity forecast technique, leading to our prediction for cycle 24 parameters; cycle 24 will be only half as active as cycle 23, reaching its peak in May 2013. We speculate on the possible implications of this outcome on future earth climate change and the ensuing socio-economic consequences. 相似文献
300.
Yu. A. Gravchenko B. K. Grankin V. V. Kozlov S. V. Chirva 《Russian Aeronautics (Iz VUZ)》2017,60(3):327-334
The paper adduces the relators for algebraic operations on graphs using the numeric codes of the graphs. The special algebra of codes has been devised with consideration of the principles of graph transformation. This paper demonstrates the relevance of numeric coding of graphs for solving the problems of enumeration, systematization, and compact representation of the information about the structural and functional characteristics of the systems of flow distribution and conversion of rocket and space technology and for conducting the modeling transformations of given systems in the course of the structural and functional studies as well. 相似文献