全文获取类型
收费全文 | 2927篇 |
免费 | 4篇 |
国内免费 | 6篇 |
专业分类
航空 | 1240篇 |
航天技术 | 762篇 |
综合类 | 8篇 |
航天 | 927篇 |
出版年
2022年 | 6篇 |
2021年 | 22篇 |
2019年 | 7篇 |
2018年 | 181篇 |
2017年 | 156篇 |
2016年 | 83篇 |
2015年 | 37篇 |
2014年 | 70篇 |
2013年 | 68篇 |
2012年 | 89篇 |
2011年 | 198篇 |
2010年 | 164篇 |
2009年 | 212篇 |
2008年 | 210篇 |
2007年 | 185篇 |
2006年 | 52篇 |
2005年 | 100篇 |
2004年 | 80篇 |
2003年 | 83篇 |
2002年 | 53篇 |
2001年 | 92篇 |
2000年 | 38篇 |
1999年 | 41篇 |
1998年 | 43篇 |
1997年 | 34篇 |
1996年 | 49篇 |
1995年 | 40篇 |
1994年 | 33篇 |
1993年 | 25篇 |
1992年 | 37篇 |
1991年 | 9篇 |
1990年 | 12篇 |
1989年 | 34篇 |
1988年 | 13篇 |
1987年 | 18篇 |
1986年 | 20篇 |
1985年 | 67篇 |
1984年 | 35篇 |
1983年 | 25篇 |
1982年 | 37篇 |
1981年 | 66篇 |
1980年 | 16篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 13篇 |
1976年 | 9篇 |
1975年 | 14篇 |
1974年 | 15篇 |
1973年 | 8篇 |
1970年 | 4篇 |
排序方式: 共有2937条查询结果,搜索用时 312 毫秒
971.
M. I. Panasuyk V. V. Kalegaev I. N. Myagkova N. V. Kuznetsov M. V. Podzolko 《Cosmic Research》2017,55(6):464-468
Factors of radiation environment in near-Earth space in a period from December 1 to 10, 2014 have been analyzed, which could affect serviceability of the onboard systems of Vernov spacecraft. 相似文献
972.
The paper describes a mathematical model of drop tests on the landing gear of the Ka-62 helicopter. The model is formulated using the multibody system simulation procedure based on the Lagrange equations of the first kind. 相似文献
973.
A technique is proposed of calculating the characteristic flight velocities for an airplane with taking into account the nominal performance of a piston engine. We consider an algorithm of design calculation for the airscrew blade geometry (twist angle, chord and optimal angle of attack along blade). Feasible rational versions of design parameters are discussed. 相似文献
974.
Analysis of errors in atmospheric density measurements by lidar on board the ISS is performed. It is shown that using as the lidar transmitter a Nd:YAG laser with moderate parameters of emission at a wavelength of 353 nm and a receiving mirror diameter of 0.4 m, it is possible to cover with a 10% measurement error a height range, on average, from 40–60 km and 30–40 km in the nighttime and daytime, respectively, down to the troposphere. Working with emission at 266 nm with a 10% error, it is possible to move to the heights of the mesosphere (70 km) and penetrate the atmosphere down to a height of 40 km. Thus, the use of two harmonics makes it possible to assimilate the height range of atmospheric density measurements from on board the ISS beginning from 70 km and down to the troposphere. 相似文献
975.
V. M. Gureev A. Kh. Khairullin F. A. Varlamov I. F. Gumerov R. Kh. Khafizov 《Russian Aeronautics (Iz VUZ)》2016,59(4):554-558
This paper considers the problem of reducing the nitrogen oxide emissions in exhaust gases (EG) of the diesel aircraft engine by exhaust gas recirculation (EGR). The main directions in improving a working process of diesel engines with EGR system were formulated. 相似文献
976.
Elkin I.GUTIRREZ VELSQUEZ 《中国航空学报》2017,30(5)
Performance prediction in preliminary design stages of several turbomachinery components is a critical task in order to bring the design processes of these devices to a successful conclusion.In this paper,a review and analysis of the major loss mechanisms and loss models,used to determine the efficiency of a single stage centrifugal compressor,and a subsequent examination to determine an appropriate loss correlation set for estimating the isentropic efficiency in preliminary design stages of centrifugal compressors,were developed.Several semi-empirical correlations,commonly used to predict the efficiency of centrifugal compressors,were implemented in FORTRAN code and then were compared with experimental results in order to establish a loss correlation set to determine,with good approximation,the isentropic efficiency of single stage compressor.The aim of this study is to provide a suitable loss correlation set for determining the isentropic efficiency of a single stage centrifugal compressor,because,with a large amount of loss mechanisms and correlations available in the literature,it is difficult to ascertain how many and which correlations to employ for the correct prediction of the efficiency in the preliminary stage design of a centrifugal compressor.As a result of this study,a set of correlations composed by nine loss mechanisms for single stage centrifugal compressors,conformed by a rotor and a diffuser,are specified. 相似文献
977.
D. Yu. Kolodyazhnyi V. S. Nagornyi A. M. Sipatov V. Ya. Modorskii 《Russian Aeronautics (Iz VUZ)》2017,60(1):97-102
A technique for calculating the two-phase flows in the pneumatic injector of the aircraft engine is developed based on solving the model problem, namely, on verification of the two-phase flow model by means of solving the problem of liquid column disintegration under the effect of an incident airflow. We determine the turbulence models that satisfactorily describe the biphase flow processes. 相似文献
978.
Sobolevsky N. M. Latysheva L. N. Kuznetsov H. V. Panasyuk M. I. Podzolko M. V. 《Cosmic Research》2021,59(4):259-267
Cosmic Research - A special version of the SHIELD transport code has been developed intended for radiation protection purposes in space. The calculation of the fluxes of primary and secondary... 相似文献
979.
Cosmic Research - We have analyzed the experimental data obtained in 2016–2019 from the measurements of plasma disturbances and electric currents induced at ionospheric altitudes upon the... 相似文献
980.
S. Z. Sverdlov 《Russian Aeronautics (Iz VUZ)》2017,60(2):163-168
In this paper, it is proposed the flight duration to be assessed by the potential value and the helicopter number. The data on the available power and the relative efficiency for a number of multicopter models are provided. 相似文献