全文获取类型
收费全文 | 34136篇 |
免费 | 2479篇 |
国内免费 | 1019篇 |
专业分类
电工技术 | 1464篇 |
综合类 | 3623篇 |
化学工业 | 1549篇 |
金属工艺 | 1453篇 |
机械仪表 | 4828篇 |
建筑科学 | 13454篇 |
矿业工程 | 1953篇 |
能源动力 | 1108篇 |
轻工业 | 774篇 |
水利工程 | 2010篇 |
石油天然气 | 844篇 |
武器工业 | 157篇 |
无线电 | 383篇 |
一般工业技术 | 1687篇 |
冶金工业 | 1445篇 |
原子能技术 | 218篇 |
自动化技术 | 684篇 |
出版年
2024年 | 136篇 |
2023年 | 324篇 |
2022年 | 828篇 |
2021年 | 966篇 |
2020年 | 949篇 |
2019年 | 634篇 |
2018年 | 675篇 |
2017年 | 822篇 |
2016年 | 986篇 |
2015年 | 1107篇 |
2014年 | 2206篇 |
2013年 | 1493篇 |
2012年 | 2479篇 |
2011年 | 2732篇 |
2010年 | 2104篇 |
2009年 | 2158篇 |
2008年 | 1858篇 |
2007年 | 2512篇 |
2006年 | 2256篇 |
2005年 | 1968篇 |
2004年 | 1390篇 |
2003年 | 1270篇 |
2002年 | 1134篇 |
2001年 | 929篇 |
2000年 | 822篇 |
1999年 | 649篇 |
1998年 | 507篇 |
1997年 | 410篇 |
1996年 | 339篇 |
1995年 | 222篇 |
1994年 | 206篇 |
1993年 | 131篇 |
1992年 | 97篇 |
1991年 | 65篇 |
1990年 | 40篇 |
1989年 | 45篇 |
1988年 | 36篇 |
1987年 | 33篇 |
1986年 | 19篇 |
1985年 | 14篇 |
1984年 | 9篇 |
1983年 | 7篇 |
1982年 | 14篇 |
1981年 | 4篇 |
1980年 | 25篇 |
1979年 | 11篇 |
1975年 | 2篇 |
1959年 | 4篇 |
1954年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
In actual engineering scenarios, limited fault data leads to insufficient model training and over-fitting, which negatively affects the diagnostic performance of intelligent diagnostic models. To solve the problem, this paper proposes a variational information constrained generative adversarial network (VICGAN) for effective machine fault diagnosis. Firstly, by incorporating the encoder into the discriminator to map the deep features, an improved generative adversarial network with stronger data synthesis capability is established. Secondly, to promote the stable training of the model and guarantee better convergence, a variational information constraint technique is utilized, which constrains the input signals and deep features of the discriminator using the information bottleneck method. In addition, a representation matching module is added to impose restrictions on the generator, avoiding the mode collapse problem and boosting the sample diversity. Two rolling bearing datasets are utilized to verify the effectiveness and stability of the presented network, which demonstrates that the presented network has an admirable ability in processing fault diagnosis with few samples, and performs better than state-of-the-art approaches. 相似文献
2.
Qiqi Peng Xu Jiang Yifan Chen Wei Zhang Jun Jiang Anquan Jiang 《Ceramics International》2021,47(16):22753-22759
Large domain wall (DW) conductivity in an insulating ferroelectric plays an important role in the future nanosensors and nonvolatile memories. However, the wall current was usually too small to drive high-speed memory circuits and other agile nanodevices requiring high output-powers. Here, a large domain-wall current of 67.8 μA in a high on/off ratio of ~4460 was observed in an epitaxial Au/BiFeO3/SrRuO3 thin-film capacitor with the minimized oxygen vacancy concentration. The studies from read current-write voltage hysteresis loops and piezo-response force microscope images consistently showed remaining of partially unswitched domains after application of an opposite poling voltage that increased domain wall density and wall current greatly. A theoretical model was proposed to explain the large wall current. According to this model, the domain reversal occurs with the appearance of head-to-head and tail-to-tail 180° domain walls (DWs), resulting in the formation of highly conductive wall paths. As the applied voltage increased, the domain-wall number increased to enhance the on-state current, in agreement with the measurements of current-voltage curves. This work paves a way to modulate DW currents within epitaxial Au/BiFeO3/SrRuO3 thin-film capacitors through the optimization of both oxygen vacancy and domain wall densities to achieve large output powers of modern domain-wall nanodevices. 相似文献
3.
This paper introduces the potential feasibility that ELID (electrolytic in-process dressing) grinding replaces superfinishing in bearing manufacturing, but ELID grinding will bring new challenges. Different regions present distinguish surface profile due to the non-uniform contact in ELID groove grinding. However, few reports explaining the non-uniform contact are available. This article explores the mechanisms of the non-uniform contact during ELID groove grinding. Experiments on the non-uniform contact between bearing raceway and grinding wheel have been carried out under different conditions. The results show that non-uniform contact exists in ELID groove grinding process and it exerts influence on the profile of the raceway surface. Non-uniform contact influences the Rsk and Rku value all the time, but it influences the Ra value occasionally. Improvement strategies of eliminating the non-uniform contact are also discussed based on the experimental study. 相似文献
4.
5.
Donghai Xu Peng Feng Yang Wang Wanpeng Yang Yu Wang Shaoyan Sun 《American Institute of Chemical Engineers》2022,68(2):e17472
Corrosion and salt deposition problems severely restrict the industrialization of supercritical water oxidation. Transpiring wall reactor can effectively weaken these two problems by a protective water film. In this work, methanol was selected as organic matter, and the influences of vital structural parameters on water film properties and organic matter removal were studied via numerical simulation. The results indicate that higher than 99% of methanol conversion could be obtained and hardly affected by transpiration water layer, transpiring wall porosity and inner diameter. Increasing layer and porosity reduced reactor center temperature, but inner diameter's influence was lower relatively. Water film temperature reduced but coverage rate raised as layer, porosity, and inner diameter increased. Notably, the whole reactor was in supercritical state and coverage rate was only approximately 85% in the case of one layer. Increasing reactor length affected slightly the volume of the upper supercritical zone but enlarged the subcritical zone. 相似文献
6.
7.
8.
9.
墙体裂缝的成因及防治 总被引:2,自引:2,他引:0
介绍了墙体裂缝的种类,从地基不均匀下沉、温度变化等方面分析了引起墙体裂缝的原因,介绍了墙体裂缝的预防措施和治理措施,以有效控制墙体裂缝的危害程度。 相似文献
10.