全文获取类型
收费全文 | 68652篇 |
免费 | 5647篇 |
国内免费 | 2979篇 |
专业分类
电工技术 | 3890篇 |
技术理论 | 10篇 |
综合类 | 4535篇 |
化学工业 | 11520篇 |
金属工艺 | 3590篇 |
机械仪表 | 3885篇 |
建筑科学 | 5376篇 |
矿业工程 | 1823篇 |
能源动力 | 1918篇 |
轻工业 | 5305篇 |
水利工程 | 1288篇 |
石油天然气 | 3662篇 |
武器工业 | 526篇 |
无线电 | 8235篇 |
一般工业技术 | 8515篇 |
冶金工业 | 3415篇 |
原子能技术 | 715篇 |
自动化技术 | 9070篇 |
出版年
2024年 | 310篇 |
2023年 | 1176篇 |
2022年 | 2086篇 |
2021年 | 2875篇 |
2020年 | 2244篇 |
2019年 | 1784篇 |
2018年 | 2045篇 |
2017年 | 2133篇 |
2016年 | 2084篇 |
2015年 | 2676篇 |
2014年 | 3339篇 |
2013年 | 3891篇 |
2012年 | 4302篇 |
2011年 | 4708篇 |
2010年 | 3882篇 |
2009年 | 3706篇 |
2008年 | 3683篇 |
2007年 | 3442篇 |
2006年 | 3279篇 |
2005年 | 2856篇 |
2004年 | 2133篇 |
2003年 | 1887篇 |
2002年 | 1729篇 |
2001年 | 1547篇 |
2000年 | 1687篇 |
1999年 | 2004篇 |
1998年 | 1707篇 |
1997年 | 1395篇 |
1996年 | 1378篇 |
1995年 | 1143篇 |
1994年 | 1004篇 |
1993年 | 695篇 |
1992年 | 543篇 |
1991年 | 393篇 |
1990年 | 338篇 |
1989年 | 308篇 |
1988年 | 219篇 |
1987年 | 154篇 |
1986年 | 110篇 |
1985年 | 81篇 |
1984年 | 61篇 |
1983年 | 41篇 |
1982年 | 52篇 |
1981年 | 33篇 |
1980年 | 34篇 |
1979年 | 13篇 |
1977年 | 9篇 |
1976年 | 13篇 |
1974年 | 11篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
51.
Direct imaging of a high-power diode laser cavity using a transparent indium-tin-oxide (ITO) contact
We describe a novel "see-through" indium-tin-oxide contact on the n-side of a high power unstable resonator semiconductor laser (URSL) that allows direct observation of the cavity during high power operation. Under optimized annealing conditions this transparent ITO contact has a low enough specific contact resistivity to permit normal high power CW operation of the URSL and allows the observation of filamentation. This contact scheme is applicable to a wide range of semiconductor lasers and is especially appropriate for high power devices. The same structure can also be used to obtain a 2-D thermal map of the laser cavity. 相似文献
52.
观赏草在庭园中的设计与应用 总被引:2,自引:0,他引:2
观赏草以其灵动的景观特质,草类特有的自然色调,飘逸的质感越来越受到设计师们的青睐,用于焦点、绿蒿、花镜、镶边均有不凡的表现,虽为草类,却有着灌木的功能。 相似文献
53.
陆传赉 《北京邮电大学学报》1992,(1)
本文考察了ρ-混合噪声中ρ-混合随机信号的 Min-Max 检测问题.首先,将[5]中(?)-混合条件减弱为ρ-混合相依条件;其次,去掉了[5]中式(5)(?)r_n<∞的限制条件;第三,将[5]中常值的弱信号拓广到具有ρ-混合相依的随机信号,故本文改进了[5]中结果. 相似文献
54.
Ching-Te Chuang De V. Shih-Lien Lu Soumyanath K. Partovi H. Sakurai T. 《Design & Test of Computers, IEEE》1998,15(3):119-124
Microprocessor and other lC performance continues to improve at historic rates, with no visible end in sight for the next 10 years. However, we are starting to encounter a power wall. This is true for high-performance components as well as for low-power chips with a very limited energy budget offered by batteries. We need to find ways to manage power and energy consumption on all fronts-technology, design, and architecture-without compromising performance. Otherwise, we may face discontinuation of Moore's law for the semiconductor industry in the near future. This would be triggered not by any difficulty in the scaling of process technology but by formidable barriers posed by packaging and cooling, inefficacy of power delivery, and energy constraints dictated by battery technology, which is advancing at a very lukewarm pace 相似文献
55.
Hung-Ching Lu Wen-Chen Lin 《Industrial Electronics, IEEE Transactions on》1993,40(1):157-162
A controller is presented that improves the performance and reduces the sensitivity of hydraulic servo systems in the presence of parameter variations, nonlinear effects, and other disturbances. The control system has enhanced closed-loop stability and can recover from steady-state and transient error quickly and completely. It consists of a servo controller, an auxiliary controller, and a robust controller. Simulation and experimental results demonstrate the validity of the controller 相似文献
56.
Neural Computing and Applications - Most traditional genetic programming methods that handle symbolic regression are random algorithms without memory and direction. They repeatedly search for the... 相似文献
57.
Hao Ruiyang Lu Bingyu Cheng Ying Li Xiu Huang Biqing 《Journal of Intelligent Manufacturing》2021,32(7):1833-1843
Journal of Intelligent Manufacturing - With the advance in Industry 4.0, smart industrial monitoring has been proposed to timely discover faults and defects in industrial processes. Steel is widely... 相似文献
58.
59.
60.
Chemical looping combustion (CLC) is a clean and efficient flame-free combustion technology,which combust the fuels by lattice oxygen from a solid oxygen carrier with inherent CO2 capture.The develop-ment of oxygen carriers with low cost and high redox performance is crucial to the whole efficiency of CLC process.As the solid by-product from the sulfuric acid production,pyrite cinder presented excellent redox performance as an oxygen carrier in CLC process.The main components in pyrite cinder are Fe2O3,CaSO4,Al2O3 and SiO2 in which Fe2O3 is the active component to provide lattice oxygen.In order to sys-tematic investigate the functions of supports (CaSO4,Al2O3 and SiO2) in pyrite cinder,three oxygen car-riers (Fe2O3-CaSO4,Fe2O3-Al2O3 and Fe2O3-SiO2) were prepared and evaluated in this study.The results showed that Fe2O3-CaSO4 displayed high redox activity and cycling stability in the multiple redox cycles.However,both Fe2O3-Al2O3 and Fe2O3-SiO2 experienced serious deactivation during redox reactions.It indicated that the inert Fe-Si solid solution (Fe2SiO4) was formed in the spent Fe2O3-SiO2 sample,which decreased the oxygen carrying capacity of this sample.The XPS results showed that the oxygen species on the surface of Fe2O3-CaSO4 could be fully recovered after the 20 redox cycles.It can be concluded that CaSO4 is the key to the high redox activity and cycling stability of pyrite cinder. 相似文献