全文获取类型
收费全文 | 11370篇 |
免费 | 998篇 |
国内免费 | 401篇 |
专业分类
电工技术 | 558篇 |
技术理论 | 2篇 |
综合类 | 827篇 |
化学工业 | 2055篇 |
金属工艺 | 173篇 |
机械仪表 | 193篇 |
建筑科学 | 1270篇 |
矿业工程 | 1806篇 |
能源动力 | 769篇 |
轻工业 | 932篇 |
水利工程 | 1112篇 |
石油天然气 | 488篇 |
武器工业 | 19篇 |
无线电 | 342篇 |
一般工业技术 | 328篇 |
冶金工业 | 1264篇 |
原子能技术 | 56篇 |
自动化技术 | 575篇 |
出版年
2024年 | 25篇 |
2023年 | 158篇 |
2022年 | 331篇 |
2021年 | 397篇 |
2020年 | 370篇 |
2019年 | 263篇 |
2018年 | 223篇 |
2017年 | 289篇 |
2016年 | 340篇 |
2015年 | 335篇 |
2014年 | 747篇 |
2013年 | 559篇 |
2012年 | 886篇 |
2011年 | 926篇 |
2010年 | 704篇 |
2009年 | 655篇 |
2008年 | 542篇 |
2007年 | 778篇 |
2006年 | 672篇 |
2005年 | 577篇 |
2004年 | 465篇 |
2003年 | 448篇 |
2002年 | 365篇 |
2001年 | 300篇 |
2000年 | 290篇 |
1999年 | 262篇 |
1998年 | 217篇 |
1997年 | 140篇 |
1996年 | 103篇 |
1995年 | 99篇 |
1994年 | 75篇 |
1993年 | 59篇 |
1992年 | 58篇 |
1991年 | 33篇 |
1990年 | 22篇 |
1989年 | 16篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1971年 | 1篇 |
1957年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
41.
The microstructure and electrochemical behavior of Mg–6Al–1Zn, Mg–6Al–1Zn–1Ga, Mg–6Al–1Zn–1Sn, and Mg–6Al–1Zn–0.5Sn–0.5Ga as anode materials in a 3.5 wt% NaCl solution are compared systematically. The results show that Sn alloying refines the second-phases of Mg–6Zn–1Al by promoting tiny granular Mg17Al12 phases containing Sn, and inspires their disperse distribution. However, the Ga results in the formation of semicontinuous reticular Ga containing Mg17Al12 phases. The comparison of discharge tests indicates that Mg–6Al–1Zn–1Sn has the highest discharge activity, and Mg–6Al–1Zn–1Ga displays the largest hydrogen evolution corrosion resistance in 3.5 wt% NaCl solution at 298 K. The synergy of Ga and Sn can shorten discharge activation time and promote low discharge potential. In addition, the utilization efficiencies of the alloys decrease as follows: Mg–6Al–1Zn–1Ga > Mg–6Al–1Zn–0.5Sn–0.5Ga > Mg–6Al–1Zn–1Sn > Mg–6Zn–1Al. This study illustrates that the Mg–6Al–1Zn–0.5Sn–0.5Ga alloy has acceptable utilization efficiency and desirable electrochemical activity, which implies that doping Ga and Sn obtains a balance between discharge activity and utilization efficiencies. 相似文献
42.
当前,我国新能源电力飞速发展,新能源大规模的接入给电网企业规划带来了更大的挑战。电网规划研究对象多集中于电网本身,对电网企业规划研究较少。文章在该背景下构建电网企业规划能力评价指标体系,并在组合赋权的基础上建立改进物元可拓模型对实际算例展开电网企业规划能力综合评价。最终验证所提出的模型能在实际应用中有较强的推广性,能帮助电网企业更好地识别自身规划能力。 相似文献
43.
介绍了黄背场铅锌矿采用全面采矿法在小矿体开采和探矿中的应用实践,该工艺具有投入少、生产成本低,简单易行等特点,有很强的适应性和实用性。 相似文献
44.
45.
随着国家对矿产资源开采的不断深入,富矿石、易选矿石逐渐枯竭,入选的贫矿石和难选矿石比例不断上升,导致生产处理成本增加。人工智能、智能光电选矿技术,可以甄别和分拣矿石,实现提前抛废,对矿石进行预富集,提高矿石的入选品位,提升矿石综合利用率,成为解决经济增长中矿产资源短缺重要手段,确保矿产资源安全和矿业经济稳定发展的研究方向。 相似文献
46.
47.
《International Journal of Hydrogen Energy》2022,47(75):32071-32080
Ni-based catalysts have been widely studied in reforming methane with carbon dioxide. However, Ni-based catalysts tends to form carbon deposition at low temperatures (≤600 °C), compared with high temperatures. In this paper, a series of Ni/SiO2-XG catalysts were prepared by the glycine-assisted incipient wetness impregnation method, in which X means the molar ratio of glycine to nitrate. XRD, H2-TPR, TEM and XPS results confirmed that the addition of glycine can increase Ni dispersion and enhance the metal-support interaction. When X ≥ 0.3, these catalysts have strong metal-support interaction and small Ni particle size. The Ni/SiO2-0.7G catalyst has the best catalytic performance in dry reforming of methane (DRM) test at 600 °C, and its CH4 conversion is 3.7 times that of Ni/SiO2-0G catalyst. After 20 h reaction under high GHSV (6 × 105 ml/gcat/h), the carbon deposition of Ni/SiO2-0.7G catalyst is obviously lower than that of Ni/SiO2-0G catalyst. Glycine-assisted impregnation method can enhance the metal-support interaction and decrease the metal particle size,which is a method to prepare highly dispersed and stable Ni-based catalyst. 相似文献
48.
《水科学与水工程》2022,15(2):114-124
Hydrological, sediment, and bathymetric data of the Shashi Reach in the middle Yangtze River for the period of 1975–2018 were collected, and the characteristics of low water level changes and their impacts on utilization of water depth for navigation were investigated. The results showed that, during the study period, the Shashi Reach riverbed was significantly scoured and incised, with cross-sectional profiles showing overall narrowing and deepening. This indicated a strong potential to improve the water depth of the channel. The analysis of the temporal variation of in-channel topographical features showed that the Taipingkou diara underwent siltation and erosion, with its head gradually scoured and relocated downstream after 2008, and the Sanbatan diara continued to shrink and migrate leftwards. Low water levels with the same flow rate over the study period decreased. For instance, from 2003 to 2020, the water level at the Shashi hydrological station decreased to 1.37 m with a flow rate of 6 000 m3/s. Furthermore, the designed minimum navigable water level of the Shashi Reach was approximately 2.11 m lower than the recommended level. In terms of utilization of the channel water depth, continuous scouring of the river channel is expected to result in a reduction in discharge at the Taipingkou mouth, which will improve the water depth conditions of the channel during the dry season in the Shashi Reach. With several channel regulation projects, the 3.5-m depth of the Shashi Reach would basically be unobstructed. This promotes utilization of the shipping route from the Taipingkou south branch to the Sanbatan north branch as the main navigation channel during the dry season. Considering the factors of current water depth and the clear width limitation of the navigation hole at the Jingzhou Yangtze River Bridge, this route can still be favored as the main navigation channel with a 4.5-m depth during the dry season. 相似文献
49.