全文获取类型
收费全文 | 342篇 |
免费 | 6篇 |
国内免费 | 8篇 |
专业分类
航空 | 79篇 |
航天技术 | 40篇 |
综合类 | 10篇 |
航天 | 227篇 |
出版年
2021年 | 2篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 2篇 |
2012年 | 16篇 |
2011年 | 20篇 |
2010年 | 9篇 |
2008年 | 10篇 |
2007年 | 11篇 |
2006年 | 10篇 |
2005年 | 29篇 |
2004年 | 7篇 |
2003年 | 8篇 |
2002年 | 7篇 |
2001年 | 7篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 26篇 |
1997年 | 8篇 |
1996年 | 4篇 |
1995年 | 25篇 |
1994年 | 16篇 |
1993年 | 7篇 |
1992年 | 12篇 |
1991年 | 16篇 |
1990年 | 3篇 |
1989年 | 7篇 |
1988年 | 7篇 |
1987年 | 13篇 |
1986年 | 4篇 |
1985年 | 11篇 |
1984年 | 11篇 |
1983年 | 6篇 |
1982年 | 9篇 |
1981年 | 2篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1976年 | 1篇 |
1975年 | 2篇 |
排序方式: 共有356条查询结果,搜索用时 156 毫秒
281.
美国《大修与维修》(Overhaul& Maintenance)是美国航空周刊集团出版社的,以报道飞机、发动机及机械电子设备维护维修的科技信息杂志,《航空工程与维修》是国际航空杂志社出版的一本集报道航空工程与维修为一体的刊物。自2001年初开始,国际航空杂志社与美国航空周刊集团签订了版权交换协议,因此,我刊从本期开始,开设了Overhaul&Maintenace专栏,为广大中国民航军队的飞机维护维修人员提供了一个了解国外维修业的窗口,希望广大读者对本专栏提出宝贵意见,以帮助我们不断改进。 相似文献
282.
采用高压固态调制器和高压电源能够延长采用微波真空电子管(VED)的高功率雷达发射机的使用寿命。无论是集成式的还是独立的固态调制器和电源,都适于改型设计和新设计的雷达发射机。本文同时列出了现代固态调制器的结构和被替代的传统固态调制器的结构,并介绍了几部已用或可能用“恰当技术”进行改进的战场雷达发射机。 相似文献
283.
本文提出了快撕裂模加热是1980年5月21日—22日耀斑后冕拱长达10多小时的有效加热机制。作者计算了撕裂模所提供的能量和相应的增长率,并讨论了该冕拱的MHD平衡和稳定性问题,主要结论如下:1.对5月21日冕拱,当密度取1.6×109cm-3(实测值)时,剪切宽度αα=1.8×108cm(冕拱小半径的十分之一)剪切磁场为18—32×10-4T,所对应的增长率为1.79×10-5s-1—2.66×10-5s-1,不稳定的增长时间为15.5h—10.4h,这组解与观测到的冕拱存在10多小时相符。所以,撕裂模是冕拱合理的有效加热机制。2.该冕拱之所以维持10多小时之久,除撕裂模加热与辐射损失平衡外,在力学上必须处于平衡态,其平衡条件为Bφ(冕拱轴向磁场)=2Bθ(冕拱的环向场),和气压梯度dp/dr大于零。若冕拱满足该力学平衡条件,则利用能量原理可得到该系统对腊肠扰动、扭曲扰动、螺旋扰动均是稳定的。 相似文献
284.
285.
286.
When predicting parameters of quasi-stationary Solar Wind (SW) streams at 1 AU, it is customary to use, as the indicator of solar sources, the Bases of Open Magnetic Tubes (BOMT) on the solar surface obtained via a calculation relying on a new Bd-technique of harmonic expansion of the magnetic field from daily full-disk magnetograms developed by Rudenko[4]. By considering an example of 17 events, it is shown that the correspondence between fast SW streams at the Earth's orbit and the BOMT, calculated with ≤ 24 h time resolution, makes up about 94%, while the correspondence of SW stereams with the CH in the light of the 10830 A line is about 29%. With this technique, the predictability of maxima of the Kp index of magnetospheric disturbance caused by a fast quasi-stationary SW, is over 90%, and the prediction accuracy of the maximun velocity vm of the stream is ±15%. 相似文献
287.
Alfredo Güemes Antonio Fernandez-Lopez Jaime García-Ramírez Maria Eugenia Reyes-Perez Flor Criado Zurita 《南京航空航天大学学报(英文版)》2018,(2)
Probability of detection(POD)graphics allow for a change from qualitative to quantitative assessment for every damage detection system,and as such it is a main request for conventional non-destructive testing(NDT)techniques.Its availability can greatly help towards the industrialization of the corresponding Structural health monitoring(SHM)system.But having in mind that for SHM systems the sensors are at fixed positions,and the location of a potential damage would change its detectability.Consequently robust simulation tools are required to obtain the model assisted probability of detection(MAPOD)which is needed to validate the SHM system.This tool may also help for the optimization of the sensor distribution,and finally will allow a probabilistic risk management.INDEUS,simulation of ultrasonic waves SHM system,was a main milestone in this direction.This article deals with the simulation tools for a strain based SHM system,using fiber optic sensors(FOS).FOS are essentially strain/temperature sensors,either with multi-point or with distributed sensing.The simulation tool includes the finite element model(FEM)for the original and damaged structure,and algorithms to compare the strain data at the pre-established sensors locations,and from this comparison to extract information about damage occurrence and location.The study has been applied to the structure of an all-composite unmanned aircraft vehicle(UAV)now under construction,designed at Universidad Politecnica de Madrid for the inspection of electrical utilities networks.Distributed sensing optical fibers were internally bonded at the fuselage and wing.Routine inspection is planned to be done with the aircraft at the test bench by imposing known loads.From the acquired strain data,damage occurrence may be calculated as slight deviations from the baselines.This is a fast inspection procedure without requiring trained specialists,and it would allow for detection of hidden damages.Simulation indicates that stringer partial debondings are detected before they become critical,while small delaminations as those produced by barely visible impact damages would require a prohibited number of sensing lines.These simulation tools may easily be applied to any other complex structure,just by changing the FEM models.From these results it is shown how a fiber optic based SHM system may be used as a reliable damage detection procedure. 相似文献
288.
In this report briefly presented the contemporary state of the experimental base of Radio Astrophysical Observatory (RAO) of the Institute of Solar-Terrestrial Physics (ISTP), the methodology of radioheliographic monitoring of the solar corona, the SSRT database, the RAO Web-pages, factors limiting the effective use of SSRT. Here are formulated the original results of the basic directions of the solar activity researches and the problems solutions on SSRT: (1) active regions at various development stages, morphology, modeling,signs of energy accumulation and flares buildup, forecast of powerful flares; (2) scenario, topology and the fine temporal picture of flares development, signs of primary energy release, radio emission mechanisms, scatter effects of radio emission in turbulent corona, energetic particles fluxes; (3) filaments; (4) CME with the localization of their initiation at the solar disk background, development scenario of filament activation + CME +flare; (5) coronal holes, and (6) bright coronal points. 相似文献
289.
G.Y.Smolkov 《空间科学学报》2005,25(5):338-344
In this paper, the possibility and some results of radioheliographic study of space weather solar factors are shortly described. 相似文献
290.
This paper presents simulated results of the ionospheric behavior during few geomagnetic storms,which were occurred in the different seasons. The numerical model for ionosphere-plasmasphere coupling was used to interpret the observed variation of ionosphere structure. Reasons why the positive storms are dominant in the winter whereas the negative ones are dominant in the summer season present the special interest for the mid-latitude ionosphere. A theoretical analysis of the processes controlling the ionospheric response to the geomagnetic storms has showed a good agreement between the simulated results and measurements, as well as the crucial role of the neutral composition variations to fit the calculated and the observed ionospheric parameters. 相似文献