全文获取类型
收费全文 | 200篇 |
免费 | 5篇 |
专业分类
化学工业 | 27篇 |
金属工艺 | 23篇 |
机械仪表 | 8篇 |
建筑科学 | 6篇 |
能源动力 | 14篇 |
轻工业 | 24篇 |
石油天然气 | 3篇 |
无线电 | 33篇 |
一般工业技术 | 24篇 |
冶金工业 | 26篇 |
原子能技术 | 1篇 |
自动化技术 | 16篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 2篇 |
2020年 | 10篇 |
2019年 | 4篇 |
2018年 | 9篇 |
2017年 | 7篇 |
2016年 | 4篇 |
2015年 | 4篇 |
2014年 | 10篇 |
2013年 | 16篇 |
2012年 | 8篇 |
2011年 | 16篇 |
2010年 | 15篇 |
2009年 | 12篇 |
2008年 | 9篇 |
2007年 | 5篇 |
2006年 | 7篇 |
2005年 | 12篇 |
2004年 | 6篇 |
2003年 | 6篇 |
2002年 | 2篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 5篇 |
1997年 | 8篇 |
1996年 | 2篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1991年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1983年 | 1篇 |
1979年 | 2篇 |
排序方式: 共有205条查询结果,搜索用时 0 毫秒
1.
A method for the time suboptimal control of an industrial manipulator from an initial position and orientation to a final
position and orientation as it moves along a specified path is proposed. Nonlinear system equations that describe the manipulator
motion are linearized at each time step along the path. A method which gives the control inputs (joint angular velocities)
for time suboptimal control of the manipulator is developed. In the formulation, joint angular velocity and acceleration limitations
are also taken into consideration. A six degree of freedom elbow type manipulator is used in numerical examples to verify
the method developed. 相似文献
2.
Book Reviewed: Iain E.G. Richardson, H.264 and MPEG-4 VideoCompression: Video Coding for Next-GenerationMultimedia, John Wiley & Sons, 2003, $102.00, 206 pp., ISBN 0-470-84837-5. 相似文献
3.
4.
Ugur Ozdemir Yucel Orkut Aktas Aslihan Vuruskan Yasin Dereli Ahmed Farabi Tarhan Karaca Demirbag Ahmet Erdem Ganime Duygu Kalaycioglu Ibrahim Ozkol Gokhan Inalhan 《Journal of Intelligent and Robotic Systems》2014,74(1-2):371-393
For the last four decades Unmanned Air Vehicles (UAVs) have been extensively used for military operations that include tracking, surveillance, active engagement with weapons and airborne data acquisition. UAVs are also in demand commercially due to their advantages in comparison to manned vehicles. These advantages include lower manufacturing and operating costs, flexibility in configuration depending on customer request and not risking the pilot on demanding missions. Even though civilian UAVs currently constitute 3 % of the UAV market, it is estimated that their numbers will reach up to 10 % of the UAV market within the next 5 years. Most of the civilian UAV applications require UAVs that are capable of doing a wide range of different and complementary operations within a composite mission. These operations include taking off and landing from limited runway space, while traversing the operation region in considerable cruise speed for mobile tracking applications. This is in addition to being able traverse in low cruise speeds or being able to hover for stationary measurement and tracking. All of these complementary and but different operational capabilities point to a hybrid unmanned vehicle concept, namely the Vertical Take-Off and Landing (VTOL) UAVs. In addition, the desired UAV system needs to be cost-efficient while providing easy payload conversion for different civilian applications. In this paper, we review the preliminary design process of such a capable civilian UAV system, namely the TURAC VTOL UAV. TURAC UAV is aimed to have both vertical take-off and landing and Conventional Take-off and Landing (CTOL) capability. TURAC interchangeable payload pod and detachable wing (with potential different size variants) provides capability to perform different mission types, including long endurance and high cruise speed operations. In addition, the TURAC concept is to have two different variants. The TURAC A variant is an eco-friendly and low-noise fully electrical platform which includes 2 tilt electric motors in the front, and a fixed electric motor and ducted fan in the rear, where as the TURAC B variant is envisioned to use high energy density fuel cells for extended hovering time. In this paper, we provide the TURAC UAV’s iterative design and trade-off studies which also include detailed aerodynamic and structural configuration analysis. For the aerodynamic analysis, an in-house software including graphical user interface has been developed to calculate the aerodynamic forces and moments by using the Vortex Lattice Method (VLM). Computational Fluid Dynamics (CFD) studies are performed to determine the aerodynamic effects for various configurations For structural analysis, a Finite Element Model (FEM) of the TURAC has been prepared and its modal analysis is carried out. Maximum displacements and maximal principal stresses are calculated and used for streamlining a weight efficient fuselage design. Prototypes have been built to show success of the design at both hover and forward flight regime. In this paper, we also provide the flight management and autopilot architecture of the TURAC. The testing of the controller performance has been initiated with the prototype of TURAC. Current work focuses on the building of the full fight test prototype of the TURAC UAV and aerodynamic modeling of the transition flight. 相似文献
5.
Yucel Birol 《国际钢铁研究》2009,80(8):588-592
Semisolid processing, already a well established manufacturing route for the production of intricate, thin‐walled aluminium and magnesium parts with mechanical properties as good as forged grades, faces a major challenge in the case of steels. The tool materials must withstand complex load profiles and relatively higher forming temperatures for thousands of forming cycles for industrial application to be attractive. Since the forming pressures are much lower than those encountered in conventional forging, the principle die failure mechanism in steel thixoforging is expected to be thermal fatigue. Hence, suitable materials able to withstand the steel thixoforming environment for an economically acceptable life, can be best identified with a thermal fatigue test. Such a test is described in the present work. A novel CrNiCo and a nickel‐base superalloy, reported to exhibit superior thermal fatigue resistance in demanding tooling applications, was tested under thermal fatigue conditions encountered in the thixoforming of steels. 相似文献
6.
The potential of cooling slope casting process to produce EN AW 6082 forging stock for the manufacture of EN AW 6082 suspension components was investigated. EN AW 6082 billets cast over a cooling plate offer a fine uniform structure that can be forged even without a separate homogenization treatment. This is made it possible by the limited superheat of the melt at the start of casting and the fractional solidification that occurs already on the cooling plate. Suspension parts forged from cast and homogenized billets with or without Cr all showed a uniform structure, and the hardness reached HV 110 after the standard artificial ageing treatment. 相似文献
7.
In this work, sulfur-doped graphene-coated electrodes are prepared by cyclic voltammetry in different potential ranges and different cycles (from 10 to 50) for selective modification of electrodes by different functional groups. The prepared electrodes are characterized by spectroscopic, microscopic and electrochemical methods. In scanning electron microscopic analysis, formation of graphene layers and their porous structure have been determined. Electrochemical impedance spectroscopic and cyclic voltammetric analyses are also used in electrochemical characterization of the electrodes. Then, the prepared sulfur-doped graphene-coated electrodes by using cyclic voltammetry in one-step and low cost are used as electrode materials of supercapacitor for the first time in the literature. Since the mesoporous structure of the electrodes prepared in lower potential ranges increases, specific capacitance of the electrodes increases from 74 to 1833 mF cm−2 with 10 mA cm−2 current density. This result shows that specific capacitances of prepared electrodes are higher than those of the electrodes prepared with metal-doped in the literature. 相似文献
8.
Food Science and Biotechnology - In the present study, variety of fruit vinegars were investigated in terms of their physicochemical, microbiological and bioactive properties. Total phenolic and... 相似文献
9.
Twin roll cast EN AW Al-Mn1Cu plates were butt welded with the friction stir welding process which employed a non-consumable tool, tilted by 1.5° and 3° with respect to the plate normal, rotated in a clockwise direction at 400 and 800 rpm, while traversing at a fixed rate of 80 mm/min along the weld line. Microstructural observations and microhardness tests were performed on sections perpendicular to the tool traverse direction. Tensile tests were carried out at room temperature on samples cut perpendicular to the weld line. The ultimate tensile strength of the welded EN AW Al-Mn1Cu plates improved with increasing tool rotation speed and decreasing tool tilt angle. This marked improvement in ultimate tensile strength is attributed to the increase in the heat input owing to an increased frictional heat generation. There appears to be a perfect correlation between the ultimate tensile strength and the size of the weld zone. The fracture surfaces of the base plate and the welded plates are distinctly different. The former is dominated by dimples typical of ductile fractures. A vast majority of the intermetallic particles inside the weld zones are too small to generate dimples during a tensile test. The fracture surface of the welded plates is thus characterized by occasional dimples that are elongated in the same direction suggesting a tensile tearing mechanism. 相似文献
10.
铝合金半固态浆料中球形颗粒的演变 总被引:1,自引:0,他引:1
Yucel BIROL 《中国有色金属学会会刊》2013,23(1):1-6
用AlSi7Mg0.6半固态浆料进行实验,研究球形颗粒的演变机理.在略高于液相线温度下水淬的样品中结晶相主要为枝晶,而采用旋转圆筒的方式来搅拌熔体使其冷却到半固态温度范围内时样品的结晶相完全球化.在铸造前进行较长时间的内冷却和搅拌,可以得到较高的固相分数.不同大小的枝晶碎片的存在表明,在搅拌过程中,初始的固相分数形成后不再受冷却的影响. 相似文献