全文获取类型
收费全文 | 132134篇 |
免费 | 10403篇 |
国内免费 | 5894篇 |
专业分类
电工技术 | 5120篇 |
技术理论 | 13篇 |
综合类 | 11324篇 |
化学工业 | 23616篇 |
金属工艺 | 3101篇 |
机械仪表 | 3917篇 |
建筑科学 | 15805篇 |
矿业工程 | 6715篇 |
能源动力 | 9591篇 |
轻工业 | 9959篇 |
水利工程 | 19442篇 |
石油天然气 | 12524篇 |
武器工业 | 374篇 |
无线电 | 3598篇 |
一般工业技术 | 6693篇 |
冶金工业 | 6044篇 |
原子能技术 | 1492篇 |
自动化技术 | 9103篇 |
出版年
2024年 | 324篇 |
2023年 | 1474篇 |
2022年 | 2975篇 |
2021年 | 3591篇 |
2020年 | 3945篇 |
2019年 | 3226篇 |
2018年 | 2994篇 |
2017年 | 3624篇 |
2016年 | 3958篇 |
2015年 | 4035篇 |
2014年 | 7870篇 |
2013年 | 8024篇 |
2012年 | 9719篇 |
2011年 | 9907篇 |
2010年 | 7581篇 |
2009年 | 7691篇 |
2008年 | 6909篇 |
2007年 | 8961篇 |
2006年 | 8427篇 |
2005年 | 7546篇 |
2004年 | 6123篇 |
2003年 | 5521篇 |
2002年 | 4801篇 |
2001年 | 3847篇 |
2000年 | 3224篇 |
1999年 | 2534篇 |
1998年 | 1883篇 |
1997年 | 1487篇 |
1996年 | 1215篇 |
1995年 | 1067篇 |
1994年 | 847篇 |
1993年 | 588篇 |
1992年 | 500篇 |
1991年 | 365篇 |
1990年 | 273篇 |
1989年 | 287篇 |
1988年 | 173篇 |
1987年 | 170篇 |
1986年 | 132篇 |
1985年 | 146篇 |
1984年 | 121篇 |
1983年 | 89篇 |
1982年 | 48篇 |
1981年 | 36篇 |
1980年 | 42篇 |
1979年 | 34篇 |
1978年 | 13篇 |
1977年 | 23篇 |
1975年 | 9篇 |
1951年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Ivonne Sgura Amos S. Lawless Benedetto Bozzini 《Inverse Problems in Science & Engineering》2019,27(5):618-647
The process of electrodeposition can be described in terms of a reaction-diffusion partial differential equation (PDE) system that models the dynamics of the morphology profile and the chemical composition. Here we fit such a model to the different patterns present in a range of electrodeposited and electrochemically modified alloys using PDE constrained optimization. Experiments with simulated data show how the parameter space of the model can be divided into zones corresponding to the different physical patterns by examining the structure of an appropriate cost function. We then use real data to demonstrate how numerical optimization of the cost function can allow the model to fit the rich variety of patterns arising in experiments. The computational technique developed provides a potential tool for tuning experimental parameters to produce desired patterns. 相似文献
62.
《International Journal of Hydrogen Energy》2021,46(79):38983-38991
Water electrolysis is a process that can produce hydrogen in a clean way when renewable energy sources are used. This allows managing large renewable surpluses and transferring this energy to other sectors, such as industry or transport. Among the electrolytic technologies to produce hydrogen, proton exchange membrane (PEM) electrolysis is a promising alternative. One of the main components of PEM electrolysis cells are the bipolar plates, which are machined with a series of flow distribution channels, largely responsible for their performance and durability. In this work, AISI 316L stainless steel bipolar plates have been built by additive manufacturing (AM), using laser powder bed fusion (PBF-L) technology. These bipolar plates were subjected to ex-situ corrosion tests and assembled in an electrolysis cell to evaluate the polarization curve. Furthermore, the obtained results were compared with bipolar plates manufactured by conventional machining processes (MEC). The obtained experimental results are very similar for both manufacturing methods. This demonstrates the viability of the PBF-L technology to produce metal bipolar plates for PEM electrolyzers and opens the possibilities to design new and more complex flow distribution channels and to test these designs in initial phases before scaling them to larger surfaces. 相似文献
63.
64.
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
65.
《Oil and Energy Trends》2019,44(10):29-30
Current data on net electricity production, as well as a breakdown of production by country. Updated on a monthly basis. 相似文献
66.
Tian Xie Haixia Zhao Zunhang Lv Guangwen Xie Yan He 《International Journal of Hydrogen Energy》2021,46(1):581-588
This work demonstrates a facile Nb2O5-decorated electrocatalyst to prepare cost-effective Ni–Fe–P–Nb2O5/NF and compared HER & OER performance in alkaline media. The prepared electrocatalyst presented an outstanding electrocatalytic performance towards hydrogen evolution reaction, which required a quite low overpotential of 39.05 mV at the current density of ?10 mA cm?2 in 1 M KOH electrolyte. Moreover, the Ni–Fe–P–Nb2O5/NF catalyst also has excellent oxygen evolution efficiency, which needs only 322 mV to reach the current density of 50 mA cm?2. Furthermore, its electrocatalytic performance towards overall water splitting worked as both cathode and anode achieved a quite low potential of 1.56 V (10 mA cm?2). 相似文献
67.
《Oil and Energy Trends》2019,44(9):27-28
Current data on net electricity production, as well as a breakdown of production by country. Updated on a monthly basis. 相似文献
68.
69.
进入新发展阶段,中国水资源安全保障需要以“节水优先、空间均衡、系统治理、两手发力”治水思路为指导,厘清问题、研判趋势、优化对策,支撑新阶段水利高质量发展。本文在全面分析我国水资源安全保障存在的突出问题与面临形势基础上,阐述了新发展阶段中国水资源安全保障的基本思路与战略路径,从保证资源安全、构建国家水网、强化供水保障、建设美丽河湖、改善水环境质量等方面提出了战略对策和需要进一步回答的重大问题,以期为完善新发展阶段中国水资源安全保障战略,全面提高国家水资源安全保障能力提供有力支撑。 相似文献
70.
《Oil and Energy Trends》2019,44(1):26-28
Current data on natural gas production, as well as a breakdown of production by country. Updated on a monthly basis. 相似文献