全文获取类型
收费全文 | 424300篇 |
免费 | 5100篇 |
国内免费 | 1351篇 |
专业分类
电工技术 | 7778篇 |
综合类 | 323篇 |
化学工业 | 63031篇 |
金属工艺 | 18260篇 |
机械仪表 | 13392篇 |
建筑科学 | 9534篇 |
矿业工程 | 2803篇 |
能源动力 | 10884篇 |
轻工业 | 31704篇 |
水利工程 | 4785篇 |
石油天然气 | 9932篇 |
武器工业 | 35篇 |
无线电 | 51376篇 |
一般工业技术 | 87641篇 |
冶金工业 | 76565篇 |
原子能技术 | 10560篇 |
自动化技术 | 32148篇 |
出版年
2021年 | 3891篇 |
2020年 | 2911篇 |
2019年 | 3639篇 |
2018年 | 6364篇 |
2017年 | 6426篇 |
2016年 | 6807篇 |
2015年 | 4100篇 |
2014年 | 7086篇 |
2013年 | 18719篇 |
2012年 | 10927篇 |
2011年 | 14643篇 |
2010年 | 11801篇 |
2009年 | 13334篇 |
2008年 | 13920篇 |
2007年 | 13673篇 |
2006年 | 11911篇 |
2005年 | 10685篇 |
2004年 | 10109篇 |
2003年 | 10246篇 |
2002年 | 9652篇 |
2001年 | 10155篇 |
2000年 | 9426篇 |
1999年 | 9794篇 |
1998年 | 24391篇 |
1997年 | 17074篇 |
1996年 | 13215篇 |
1995年 | 9975篇 |
1994年 | 8831篇 |
1993年 | 8928篇 |
1992年 | 6590篇 |
1991年 | 6458篇 |
1990年 | 6247篇 |
1989年 | 6010篇 |
1988年 | 5953篇 |
1987年 | 5137篇 |
1986年 | 5129篇 |
1985年 | 5607篇 |
1984年 | 5235篇 |
1983年 | 5011篇 |
1982年 | 4580篇 |
1981年 | 4500篇 |
1980年 | 4471篇 |
1979年 | 4346篇 |
1978年 | 4148篇 |
1977年 | 4751篇 |
1976年 | 6054篇 |
1975年 | 3681篇 |
1974年 | 3520篇 |
1973年 | 3581篇 |
1972年 | 3190篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
73.
74.
In order to improve the process effectiveness and joint quality, ultrasonic vibrations were integrated with friction stir lap welding. Effect of ultrasonic exertion on the process and joint quality of AA 6061-T6 were investigated. Upon ultrasonic exertion, joints owned larger effective lap width, shorter hooks and improved strength. Weld fracture mode changed from a ductile–brittle mixed mode to a more ductile mode while the fracture path shifted from lap interface to beyond the stir zone. Material flow and interface defects were characterised using lap welded dissimilar aluminium alloy joints. Ultrasonic vibration improved the material flow and reduced the interfacial defects. Variations in failure load of joints were found in accordance with the variations in material flow and interfacial defects. 相似文献
75.
The dynamic interaction between the mechanical and electrical drive parameters when damage suddenly appears in the mechanical part of a conveyer belt is investigated. The possibility of using the change in the motor’s electrical parameters as a diagnostic signal is assessed. A model for investigating the dynamic processes in the system consisting of the grid, the induction motor, and the conveyer belt is proposed. The grid and induction motor are described by a model of fourth-order state space, whose output is the torque at the motor shaft. The moments of inertia and pliability of the links between the elements in the mechanical part of the conveyer belt are determined. By gradually identifying the elements with the minimum moment of inertia and distributing their moments of inertia and pliabilities among the adjacent elements, we obtain a three-mass system simulating the mechanical part of the conveyer belt. This dynamic model is solved by means of Matlab Simulink software. The energy characteristics of the drive are determined in dynamic processes following a mechanical accident. 相似文献
76.
77.
78.
Senthilkumar M. Vasundhara M. G. Kalavathi G. K. 《International Journal of Mechanics and Materials in Design》2019,15(3):611-627
International Journal of Mechanics and Materials in Design - The resonant frequency of electromechanical energy harvester should be tuned to ambient frequency so as to maximize the harvester power.... 相似文献
79.
ABSTRACTIn recent times, the applications of multimedia are rising in a greedy mode and hence the amount of video transactions is also increasing exponentially. This has shouted great demands on effective models on video encoding and also for reducing the transmission channel congestion. This research work introduces a managing technique termed weighted encoding for High-Efficiency Video Coding (HEVC). HEVC, also termed as MPEG-H Part 2 and H.265 is a video compression standard that is widely utilized AVC (H.264 or MPEG-4 Part 10). When compared to AVC, HEVC grants double the ratio of data compression at a similar level of quality of the video or considerably enhanced video quality at a similar bit rate. This work intends to optimize the weight that adopted in HEVC for encoding. For this, this paper proposes a new Iterative based propagation update in the water wave Optimization Algorithm (IPU-WWO), which is the improved form of Water wave Optimization (WWO). The performance of proposed IPU-WWO is compared over other conventional methods like Artificial Bee Colony (ABC), Firefly (FF), Particle Swarm Optimization (PSO) and Genetic Algorithm (GA) with respect to Peak Signal to Noise Ratio (PSNR). By doing the encoding process, it minimizes the video size with perceptually better quality video or PSNR. 相似文献
80.