全文获取类型
收费全文 | 4238篇 |
免费 | 101篇 |
国内免费 | 20篇 |
专业分类
电工技术 | 221篇 |
综合类 | 5篇 |
化学工业 | 1287篇 |
金属工艺 | 115篇 |
机械仪表 | 125篇 |
建筑科学 | 102篇 |
矿业工程 | 1篇 |
能源动力 | 157篇 |
轻工业 | 255篇 |
水利工程 | 6篇 |
石油天然气 | 3篇 |
无线电 | 233篇 |
一般工业技术 | 953篇 |
冶金工业 | 413篇 |
原子能技术 | 177篇 |
自动化技术 | 306篇 |
出版年
2023年 | 18篇 |
2022年 | 48篇 |
2021年 | 68篇 |
2020年 | 41篇 |
2019年 | 48篇 |
2018年 | 65篇 |
2017年 | 60篇 |
2016年 | 83篇 |
2015年 | 56篇 |
2014年 | 85篇 |
2013年 | 208篇 |
2012年 | 144篇 |
2011年 | 253篇 |
2010年 | 168篇 |
2009年 | 185篇 |
2008年 | 206篇 |
2007年 | 159篇 |
2006年 | 179篇 |
2005年 | 157篇 |
2004年 | 117篇 |
2003年 | 146篇 |
2002年 | 109篇 |
2001年 | 80篇 |
2000年 | 95篇 |
1999年 | 89篇 |
1998年 | 187篇 |
1997年 | 159篇 |
1996年 | 123篇 |
1995年 | 65篇 |
1994年 | 83篇 |
1993年 | 74篇 |
1992年 | 46篇 |
1991年 | 47篇 |
1990年 | 44篇 |
1989年 | 61篇 |
1988年 | 46篇 |
1987年 | 49篇 |
1986年 | 65篇 |
1985年 | 57篇 |
1984年 | 66篇 |
1983年 | 54篇 |
1982年 | 36篇 |
1981年 | 34篇 |
1980年 | 30篇 |
1979年 | 33篇 |
1978年 | 26篇 |
1977年 | 23篇 |
1976年 | 27篇 |
1974年 | 15篇 |
1973年 | 11篇 |
排序方式: 共有4359条查询结果,搜索用时 15 毫秒
81.
T. Sato T. Murakami T. Endo M. Shimada K. Komeya T. Kameda M. Komatsu 《Journal of Materials Science》1991,26(7):1749-1754
Corrosion behaviour of Si3N4 ceramics containing Y2O3, Al2O3 and AIN as sintering aids was investigated under hydrothermal conditions at 200–300 C and saturated vapour pressures of water for 1–10 days. Hydrothermal corrosion resulted in the dissolution of the Si3N4 matrix and the formation of a product layer consisting of the original grain-boundary phases and hydrated silica. The dissolution rate of Si3N4 ceramics decreased with decreasing crystallinity of the grain-boundary phase. The dissolution rate could be adequately described by a parabolic plot in the initial stage of the reaction. The apparent activation energies were 83.5–108 kJ mol–1, and the bending strength of the corroded samples decreased from 600 to 400 MPa in the initial stage of the reaction upto a weight loss of 0.004 g cm–2, and then was almost constant up to a weight loss of 0.012 g cm–2. 相似文献
82.
固态直线变压器驱动源(LTD)是新型的脉冲功率电路方法之一.其工作原理基于大量功率半导体器件的同步控制,因此它在电路结构和工作特性方面与传统的脉冲功率电源有很大不同.在此通过实验,首先验证了LTD的基本工作原理,进而试制了一台采用650个功率MOSFET的LTD系统.实验结果分别给出了超过20 kV的最高输出电压和超过3.2 kA的最高输出电流,上升时间(10%~90%)小于20 ns.在此基础上还采用少量的模块验证了双极性LTD的可行性.实验结果同时也显示了开关的导通电阻对LTD输出参数的影响和由此带来的技术问题. 相似文献
83.
84.
Naoji Shiroma Ryo Miyauchi Akira Nagafusa Youhei Haga Fumitoshi Matsuno 《Advanced Robotics》2015,29(3):149-163
In robot teleoperation, a robot works as a physical agent at a remote site for a robot operator. There are mainly two tasks in robot teleoperation using camera images: environment recognition using visual information and robot control according to the recognition. In this paper, we propose a gaze direction based vehicle teleoperation method with an omnidirectional image stabilization and an automatic body rotation control. In the proposed method, we manage above two tasks in the same manner that are usually treated separately. This method is an intuitive vehicle teleoperation method where an operator do not need to have concern about vehicle body orientations and can absorb differences of vehicle driving mechanisms. That is, this method frees an operator from being bothered from controlling a vehicle and the operator can concentrate on where he/she intends to go. This method mainly consists of two technologies: an omnidirectional image stabilization technology and automatic body rotation control. The conducted experiments show effectiveness of the proposed method. 相似文献
85.
Satoshi Ueki Tetsuya Mouri Takahiro Endo Haruhisa Kawasaki 《Artificial Life and Robotics》2016,21(1):31-36
This paper proposes a method for visualizing the stiffness of a soft object in a palpation-support information system by the teleoperation of a robot hand. It is important that a palpation system display a body’s shape and stiffness. In our method, the stiffness of the contact area between the soft object and the robot finger is estimated by a recursive least-squares method with forgetting factor that uses an impedance dynamics model. With the estimated stiffness and direction of contact force, we calculate the scalar parameter for visualization of stiffness. Moreover, we propose a safety control method for the palpation system, which is part of a tele-control method based on will-consensus building. The system configuration, estimated algorithm, and experimental results are presented. 相似文献
86.
In this paper null controllability with vanishing energy for discrete-time systems is considered. As in the case of continuous time systems necessary and sufficient conditions in terms of an algebraic Riccati equation are given. Then necessary and sufficient conditions involving the eigenvalues of the state matrix are given. Reachability and controllability with vanishing energy are also considered and necessary and sufficient conditions for them are given. Finally applications to sampled-data systems, systems with impulse control and periodic systems are discussed. 相似文献
87.
Yoshihisa Shinya Kenji Kamiya Tomoyuki Toyoda Yasumi Endo Nelly Soudakova Hirofumi Kondo 《Journal of the Society for Information Display》2009,17(4):331-336
Abstract— The display used in current cell phones has an air gap between the cover glass and the liquid‐crystal‐display (LCD) module to prevent the LCD glass from being damaged. Reflections at the boundaries of the air gap cause a reduction in the LCD luminance and contrast. To address this problem, a newly proposed LCD structure has been investigated. The “Super View Resin (SVR),” a transparent elastic resin which improves the shock resistance and visibility of the LCD, has been developed. Filling the air gap between the cover glass and LCD module with a refractive‐index‐matching resin solves the light‐reflection problem inherent in the use of a reinforced cover‐glass lens. Moreover, the elastic filler works as a damper, reducing any external shock, which prevents not only the cover glass and LCD module from being damaged, but also the glass from being shattered when it is broken. 相似文献
88.
Hiroki Kikuchi Shigeki Hashimoto Shinichiro Tajiri Tsuneo Hayashi Yutaka Sugawara Michio Oka Yoshiyuki Akiyama Akira Nakamura Naoya Eguchi 《Journal of the Society for Information Display》2009,17(3):263-269
Abstract— A high‐pixel‐rate, high‐contrast (30,000:1) wide‐color‐gamut grating‐light‐valve laser projector is reported. A new optical engine enabling high‐frame‐rate (240 Hz) scan projection is employed. Panoramic wide‐angle‐scan projection with a 64:9 aspect ratio was also developed. Speckle noise is eliminated using a simple but highly efficient technique. The optical throughput efficiency of the grating‐light‐valve laser projector is reviewed. 相似文献
89.
Tadashi Endo Naomichi Miyagawa Hirotsugu Takizawa Masahiko Shimada 《Journal of Materials Science》1994,29(9):2395-2400
Multiphase composites of yttria- and ceria-doped tetragonal zirconia agglomerates (10–50 m) dispersed into an alumina or alumina-zirconia matrix were sintered at 1500–1600 °C in air, followed by post-Hot Isostatic Pressing (HIP) at 1450°C and 150 MPa in an Ar gas atmosphere. The relative density of the recovered composites was above 98% of the theoretical density. By chemically etching on the surface of zirconia agglomerates, the sinterability of composites was apparently improved; and no microcracks nor pores were observed at the interface of agglomerate and matrix. According to scanning electron microscopy (SEM) observation, tetragonal and tetragonal-monoclinic zirconia agglomerates were highly dispersed into the alumina or alumina-zirconia matrix. The multiphase composites containing 10 vol% spherical agglomerates demonstrate the relatively low value of bending strength, < 400 MPa, and a high value of fracture toughness, > 11 MPa m1/2. The crack propagation introduced by Vickers indentation was efficiently suppressed and deflected by the agglomerates. 相似文献
90.
Kiyoshi Itatani Takayasu Kubozono F. Scott Howell Akira Kishioka Makio Kinoshita 《Journal of Materials Science》1995,30(5):1196-1202
The sinterability of mullite (3Al2O3·2SiO2) powder prepared by chemical vapour deposition was examined to improve the conditions for fabricating dense mullite ceramics. The starting powder contained not only mullite, but also a small amount of -Al2O3 (Al-Si spinel) and amorphous material. Although the compressed powder was fired at a temperature between 1550 and 1700 °C for 1, 3 and 5 h, the relative densities of the sintered compacts were limited to 90%: (i) due to the creation of pores/microcracks during the solid state reaction (1100–1350 °C), and (ii) due to restriction on the rearrangement of grains because the amount of liquid phase (1550–1700 °C) was insufficient. Calcination of the starting powder was effective for preparation of easily sinterable powder with homogeneous composition. When the compact formed by compressing the calcined powder at 1400 °C for 1 h was fired at 1650 °C for 3 h, the relative density was raised up to 97.2%; moreover, mullite was the only phase detected from the sintered compact. The sintered compact was composed of polyhedral grains with sizes of 1–2 m and elongated grains with long axes of 6 m. 相似文献