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892.
893.
To cope with the problem of emitter identification caused by the radar words' uncertainty of measured multi-function radar emitters, this paper proposes a new identification method based on stochastic syntax-directed translation schema(SSDTS). This method, which is deduced from the syntactic modeling of multi-function radars, considers the probabilities of radar phrases appearance in different radar modes as well as the probabilities of radar word errors occurrence in different radar phrases. It concludes that the proposed method can not only correct the defective radar words by using the stochastic translation schema, but also identify the real radar phrases and working modes of measured emitters concurrently. Furthermore, a number of simulations are presented to demonstrate the identification capability and adaptability of the SSDTS algorithm.The results show that even under the condition of the defective radar words distorted by noise,the proposed algorithm can infer the phrases, work modes and types of measured emitters correctly. 相似文献
894.
895.
Hepp A. McNatt J. Bailey S. Raffaelle R. Landi B. Sun S.-S. Bonner C. Banger K. Rauh D. 《Aerospace and Electronic Systems Magazine, IEEE》2008,23(9):31-41
The development of hybrid inorganic/organic thin-film solar cells on flexible, lightweight, space-qualified, durable substrates provides an attractive solution for space power generation with high mass specific power (W/kg). The high-volume, low-cost fabrication potential of organic cells will allow for square miles of solar cell production at one-tenth the cost of conventional inorganic materials. Plastic solar cells take a minimum of storage space and can be inflated or unrolled for deployment. We explore a cross-section of NASA in-house and sponsored research efforts that aim to provide new hybrid technologies that include both inorganic and polymer materials as active and substrate materials. For NASA applications, any solar cell or array technology must not only meet weight and AMO efficiency goals, but also must be durable enough to survive launch and space environments. Also, balance of system technologies must be developed to take advantage of ultra-lightweight solar arrays in power generation systems. 相似文献
896.
897.
As an efficient artificial truncating boundary condition, conformal perfectly matched layer (CPML) is a kind of multilayer anisotropic absorbing media. To reduce computing effort of CPML, this article proposes a layer-oriented element integration algorithm. In this algorithm, the relative dielectric constant and permeability are considered as constants for each the very thin monolayer of CPML, and the element integration of multilayer along the normal direction is substituted by the element integration of monolayer. The CPML is divided into multilayer elements, whose element matrixes are evaluated by monolayer integration. Numerical examples show that the layer-oriented element integration algorithm is reliable and the CPML formed with this algorithm possesses high-efficient absorbing performance. 相似文献
898.
发动机喘振裕度自适应控制 总被引:1,自引:0,他引:1
本文研究飞行 /推进系统一体化控制中的发动机喘振裕度自适应控制。通过一定的控制作用 ,使发动机在所有飞行条件和工况下都保持一定的喘振裕度 ,从而充分发挥发动机的潜力。将发动机大偏差模型、进气道及飞机模型综合在一起 ,构成飞机 /推进系统一体化数学模型 ,以进行发动机自适应控制的仿真。计算机仿真表明 ,发动机自适应控制具有很好的性能效益 ,例如在飞行高度 H=10公里 ,飞机由 Ma=0 .65加速到 Ma=0 .90 ,在采用自适应喘振裕度控制后 ,双发动机推力提高 16 ,飞机加速时间缩短 2 3 ,大大提高了飞机性能。 相似文献
899.
Susan Jason Alex da Silva Curiel Luis Gomes Andy Phipps Dr. Jeff Ward Dr. Wei Sun Prof. Martin Sweeting 《Acta Astronautica》2001,48(5-12)
In order to meet the growing global requirement for affordable missions beyond Low Earth Orbit, two types of platform are under design at the Surrey Space Centre. The first platform is a derivative of Surrey's UoSAT-12 minisatellite, launched in April 1999 and operating successfully in-orbit. The minisatellite has been modified to accommodate a propulsion system capable of delivering up to 1700 m/s delta-V, enabling it to support a wide range of very low cost missions to LaGrange points, Near-Earth Objects, and the Moon. A mission to the Moon - dubbed “MoonShine” - is proposed as the first demonstration of the modified minisatellite beyond LEO. The second platform - Surrey's Interplanetary Platform - has been designed to support missions with delta-V requirements up to 3200 m/s, making it ideal for low cost missions to Mars and Venus, as well as Near Earth Objects (NEOs) and other interplanetary trajectories. Analysis has proved mission feasibility, identifying key challenges in both missions for developing cost-effective techniques for: spacecraft propulsion; navigation; autonomous operations; and a reliable safe mode strategy. To reduce mission risk, inherently failure resistant lunar and interplanetary trajectories are under study. In order to significantly reduce cost and increase reliability, both platforms can communicate with low-cost ground stations and exploit Surrey's experience in autonomous operations. The lunar minisatellite can provide up to 70 kg payload margin in lunar orbit for a total mission cost US$16–25 M. The interplanetary platform can deliver 20 kg of scientific payload to Mars or Venus orbit for a mission cost US$25–50 M. Together, the platforms will enable regular flight of payloads to the Moon and interplanetary space at unprecedented low cost. This paper outlines key systems engineering issues for the proposed Lunar Minisatellite and interplanetary Platform Missions, and describes the accommodation and performance offered to planetary payloads. 相似文献
900.
本文介绍了旋转弹在低速风洞中 Magnus 效应的实验研究结果。通过不同组合体的实验,如光弹,“一”字型前翼+强身,弹身+“十”字型尾翼,“一”字型前翼+弹身+“十”字型尾翼,分别研究了旋转对弹纵向气动特性的影响及弹的 Magnus 效应特性。 相似文献