全文获取类型
收费全文 | 12569篇 |
免费 | 59篇 |
国内免费 | 72篇 |
专业分类
航空 | 6106篇 |
航天技术 | 4362篇 |
综合类 | 114篇 |
航天 | 2118篇 |
出版年
2021年 | 95篇 |
2018年 | 188篇 |
2017年 | 145篇 |
2016年 | 108篇 |
2014年 | 248篇 |
2013年 | 335篇 |
2012年 | 305篇 |
2011年 | 460篇 |
2010年 | 338篇 |
2009年 | 487篇 |
2008年 | 587篇 |
2007年 | 356篇 |
2006年 | 313篇 |
2005年 | 361篇 |
2004年 | 307篇 |
2003年 | 406篇 |
2002年 | 263篇 |
2001年 | 401篇 |
2000年 | 269篇 |
1999年 | 314篇 |
1998年 | 356篇 |
1997年 | 264篇 |
1996年 | 318篇 |
1995年 | 370篇 |
1994年 | 400篇 |
1993年 | 215篇 |
1992年 | 279篇 |
1991年 | 154篇 |
1990年 | 143篇 |
1989年 | 288篇 |
1988年 | 127篇 |
1987年 | 124篇 |
1986年 | 146篇 |
1985年 | 380篇 |
1984年 | 316篇 |
1983年 | 277篇 |
1982年 | 279篇 |
1981年 | 387篇 |
1980年 | 128篇 |
1979年 | 96篇 |
1978年 | 111篇 |
1977年 | 90篇 |
1976年 | 84篇 |
1975年 | 120篇 |
1974年 | 94篇 |
1973年 | 91篇 |
1972年 | 116篇 |
1971年 | 90篇 |
1970年 | 89篇 |
1969年 | 78篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The problem of determining the “potential” number of integration steps by explicit difference schemes is solved within the framework of the prediction model for chemically non-equilibrium processes. 相似文献
992.
The Juno Waves Investigation 总被引:1,自引:0,他引:1
W. S. Kurth G. B. Hospodarsky D. L. Kirchner B. T. Mokrzycki T. F. Averkamp W. T. Robison C. W. Piker M. Sampl P. Zarka 《Space Science Reviews》2017,213(1-4):347-392
Jupiter is the source of the strongest planetary radio emissions in the solar system. Variations in these emissions are symptomatic of the dynamics of Jupiter’s magnetosphere and some have been directly associated with Jupiter’s auroras. The strongest radio emissions are associated with Io’s interaction with Jupiter’s magnetic field. In addition, plasma waves are thought to play important roles in the acceleration of energetic particles in the magnetosphere, some of which impact Jupiter’s upper atmosphere generating the auroras. Since the exploration of Jupiter’s polar magnetosphere is a major objective of the Juno mission, it is appropriate that a radio and plasma wave investigation is included in Juno’s payload. This paper describes the Waves instrument and the science it is to pursue as part of the Juno mission. 相似文献
993.
The paper discusses a method of designing the neural controller for two-channel control of a technical object by an example of the roll and yaw control depending on deviations, velocities and accelerations of their variation. 相似文献
994.
The methodology is proposed and the mathematical model is developed for the purpose of numerical simulation of the power circuit of the gas-hydraulic actuator with displacing power source for the gimbaled nozzle control. It provides the highest power efficiency factor of the actuator as a part of aircraft by means of pulling together the profiles of available and required power. 相似文献
995.
996.
Direct measurements of the geomagnetic field have been made for more than 400 years, beginning with individual determinations of the angle between geographic and magnetic North. This was followed by the start of continuous time series of full vector measurements at geomagnetic observatories and the beginning of geomagnetic repeat stations surveys in the 19th century. In the second half of the 20th century, true global coverage with geomagnetic field measurements was accomplished by magnetometer payloads on low-Earth-orbiting satellites. This article describes the procedures and instruments for magnetic field measurements on ground and in space and covers geomagnetic observatories, repeat stations, automatic observatories, satellites and historic observations. Special emphasis is laid on the global network of geomagnetic observatories. 相似文献
997.
E. M. Korovin 《Russian Aeronautics (Iz VUZ)》2012,55(3):326-331
In this paper, a mathematical model of labor-intensity and a method of searching for optimal control of operating conditions in machining arbitrarily configurated parts with the use of CNC machines are considered. Also given is an example of the process optimization.. 相似文献
998.
The paper presents an improved technique and the results of strength analysis for the aircraft structural elements with a structural defect like an arbitrary shape delamination. 相似文献
999.
This paper proposes a novel landing gear for spacecraft that allows a weight reduction due to using deformable crash legs. Numerical simulation of the landing process was performed. 相似文献
1000.
G. S. Anufriev 《Cosmic Research》2010,48(1):101-107
The isotopic composition and concentrations of helium are investigated in 9 samples taken from different depths of a soil
column delivered by the Luna-24 mission. It is demonstrated that, with allowance made for random errors, the isotopic composition of helium remains invariable.
The concentrations of helium are subject to considerable variations, the increases and decreases relative to the average value
reaching a factor of 1.5–2. Assuming that the full length of the soil column was formed due to long-term accumulation of lunar
clastic rocks (regolith), based on measurements of cosmogenic isotopes, a method of determining the rate of regolith accumulation
has been developed, as well as a method of determining the age of the column soil samples. It is found that the rate of regolith
accumulation is variable, and it changes over the column length within the limits (0.2–0.8 cm)/106 years. The range of the time for formation of the investigated part of the column is 100–600 million years. The observed
decreases of concentration (at 250 and 600 million years) can be associated with both solar and lunar processes. In particular,
a possibility of diffusion losses of helium due to the mechanism of jump-like diffusion is discussed, and diffusion parameters
are found. A comparison of time periods of the observed variations in the solar wind with paleontological epochs and periods
is made. 相似文献