全文获取类型
收费全文 | 4767篇 |
免费 | 8篇 |
国内免费 | 10篇 |
专业分类
航空 | 1927篇 |
航天技术 | 1494篇 |
综合类 | 20篇 |
航天 | 1344篇 |
出版年
2022年 | 16篇 |
2021年 | 48篇 |
2019年 | 21篇 |
2018年 | 212篇 |
2017年 | 167篇 |
2016年 | 138篇 |
2015年 | 53篇 |
2014年 | 145篇 |
2013年 | 164篇 |
2012年 | 155篇 |
2011年 | 257篇 |
2010年 | 215篇 |
2009年 | 298篇 |
2008年 | 306篇 |
2007年 | 217篇 |
2006年 | 100篇 |
2005年 | 144篇 |
2004年 | 137篇 |
2003年 | 148篇 |
2002年 | 109篇 |
2001年 | 165篇 |
2000年 | 62篇 |
1999年 | 79篇 |
1998年 | 84篇 |
1997年 | 63篇 |
1996年 | 77篇 |
1995年 | 104篇 |
1994年 | 85篇 |
1993年 | 52篇 |
1992年 | 70篇 |
1991年 | 18篇 |
1990年 | 30篇 |
1989年 | 66篇 |
1988年 | 21篇 |
1987年 | 31篇 |
1986年 | 32篇 |
1985年 | 118篇 |
1984年 | 78篇 |
1983年 | 66篇 |
1982年 | 64篇 |
1981年 | 119篇 |
1980年 | 33篇 |
1979年 | 21篇 |
1978年 | 19篇 |
1977年 | 25篇 |
1976年 | 20篇 |
1975年 | 24篇 |
1974年 | 23篇 |
1972年 | 15篇 |
1971年 | 14篇 |
排序方式: 共有4785条查询结果,搜索用时 156 毫秒
371.
The paper presents a technique of calculating the life for gas turbine engine parts in a low cycle area based on the influence coefficients taking into account analytical and operational factors. A statistical method is used to determine the influence coefficients. 相似文献
372.
A comparison of temporal profiles of low-energy ion intensity and magnetic field magnitude in different periods of solar activity
in the outer heliosphere is carried out using the data of the Voyager 1 and Voyager 2 spacecraft. It is shown that temporal, spectral, and statistical characteristics of particle fluxes and magnetic field in
the heliospheric regions before and after the terminal shock in 2002–2008 had similar dynamics in different hemispheres. This
similarity allowed one to assume that, in the region of the inner heliospheric boundary, a quasistable spatial structure existed
moving together with the terminal shock in accordance with the solar wind pressure, as well as, probably, under the action
of the interstellar medium. It was revealed that the spatial dimensions of most details of this structure are less on Voyager 2, which, probably, is due to variation of the solar activity level, difference in latitude of spacecraft disposition, and
also the influence of the interstellar magnetic field. 相似文献
373.
I. Antonenko G.R. Osinski M. Battler M. Beauchamp L. Cupelli A. Chanou R. Francis M.M. Mader C. Marion E. McCullough A.E. Pickersgill L.J. Preston B. Shankar T. Unrau D. Veillette 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
Remote robotic data provides different information than that obtained from immersion in the field. This significantly affects the geological situational awareness experienced by members of a mission control science team. In order to optimize science return from planetary robotic missions, these limitations must be understood and their effects mitigated to fully leverage the field experience of scientists at mission control. 相似文献
374.
In this paper, we consider some typical values of motion parameters in exceptional situations when approaching to the helicopter critical flight regimes and present a technique for constructing the partial and integral informative functions of hazards at current flight regimes. Also described are the possibilities of their use for solving the problems of warning, informative crew support, and synthesizing the control algorithms to remove helicopter from the exceptional situation occurred. 相似文献
375.
V. Anmireddy R. VasudevanD. Anand T.V. RaoB.V.N. Kapardhi D. TrivediR.K. Manchanda 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
Highly sophisticated balloon-borne scientific payloads have stringent requirement on the telemetry and command system. The development and fabrication of the on-board TT&C package for telemetry, tracking, command, safety and ranging for these experiments is done in-house at the National Balloon Facility (NBF) at Hyderabad. In the last few years, we have made major improvements both in the ground station and the on-board sub-systems, thereby improving the data quality, data handling speed and the general flight control along with aviation safety. The new system has telemetry data rate up to 1 Mbps. A reduction in weight, power and cost of the reengineered on-board integrated package has also lead to the ease of operation during field tests prior to launch and at remote recovery sites. In this paper, we describe the details of the new control package, its flight performance and our plans for portable S-band telemetry and telecommand system to cater to the balloon flights from Antarctic station and long duration balloon flights. 相似文献
376.
I. A. Krivosheev A. G. Godovanyuk V. S. Fatikov G. I. Pogorelov 《Russian Aeronautics (Iz VUZ)》2010,53(1):57-62
A technique for linear interpolation of the multidimensional characteristics of a coaxial propeller fan with opposite rotation
propellers is proposed; the technique makes it possible to simulate the turbofan engine operation in the entire range of flight
conditions and reduce expenses for fullscale tests. The mathematical models obtained meet the requirements imposed in the
semi-full-scale simulation. 相似文献
377.
L. Di Fino V. ZaconteA. Ciccotelli M. LarosaL. Narici 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
Active detectors used as radiation monitors in space are not usually able to perform Particle Identification (PID). Common techniques need energy loss spectra with high statistics to estimate ion abundances. The ALTEA-space detector system is a set of silicon strip particle telescopes monitoring the radiation environment on board the International Space Station since July 2006 with real-time telemetry capabilities. Its large geometrical factor due to the concurrent use of six detectors permits the acquisition of good energy loss spectra even in a short period of observation. In this paper we present a novel Fast Probabilistic Particle Identification (FPPI) algorithm developed for the ALTEA data analysis in order to perform nuclear identification with low statistics and, with some limitations, also in real time. 相似文献
378.
V. A. Trushin 《Russian Aeronautics (Iz VUZ)》2013,56(4):372-378
The finite-difference method acceptable for on-board computers is applied to analyze the thermo-stressed state for the thermal-barrier coating of a perforated turbine blade and its wall at transient and stationary conditions of air-breathing jet engine operation during a flight. 相似文献
379.
We present the results of investigation of the dynamics of (99942) Apophis asteroid, which will undergo a very close encounter
with the Earth on April 13, 2029. The region of possible motions of the asteroid is considered on the time interval (2004,
2040). In addition, it is shown that an increase of the observational interval (2004, 2006) until 2008 allowed us to reduce
significantly the area of possible motions. All investigations were performed by numerical methods with the help of algorithms
and software developed by us in the environment of parallel programming using the SKIF Cyberia multiprocessor computer of
the Tomsk State University. 相似文献
380.
The paper presents the results of calculating nonstatitionary heat exchange between a heattransfer agent (water) and a gadolinium working element of the thermomagnetic engine with the use of ANSYS 13.0 certified software. Recommendations for designing the thermomagnetic engine working elements are given based on the analysis of calculation results. 相似文献