全文获取类型
收费全文 | 327072篇 |
免费 | 10550篇 |
国内免费 | 4924篇 |
专业分类
电工技术 | 10520篇 |
技术理论 | 6篇 |
综合类 | 6513篇 |
化学工业 | 50254篇 |
金属工艺 | 18384篇 |
机械仪表 | 17817篇 |
建筑科学 | 13847篇 |
矿业工程 | 4576篇 |
能源动力 | 7467篇 |
轻工业 | 24687篇 |
水利工程 | 3920篇 |
石油天然气 | 9455篇 |
武器工业 | 810篇 |
无线电 | 38336篇 |
一般工业技术 | 60445篇 |
冶金工业 | 34643篇 |
原子能技术 | 4471篇 |
自动化技术 | 36395篇 |
出版年
2023年 | 1982篇 |
2022年 | 3518篇 |
2021年 | 4979篇 |
2020年 | 3816篇 |
2019年 | 3509篇 |
2018年 | 12989篇 |
2017年 | 14057篇 |
2016年 | 9264篇 |
2015年 | 5711篇 |
2014年 | 6740篇 |
2013年 | 12389篇 |
2012年 | 12196篇 |
2011年 | 20054篇 |
2010年 | 17768篇 |
2009年 | 16813篇 |
2008年 | 16799篇 |
2007年 | 18892篇 |
2006年 | 9787篇 |
2005年 | 12637篇 |
2004年 | 9063篇 |
2003年 | 8397篇 |
2002年 | 7219篇 |
2001年 | 6437篇 |
2000年 | 6182篇 |
1999年 | 6323篇 |
1998年 | 8694篇 |
1997年 | 6937篇 |
1996年 | 6154篇 |
1995年 | 5116篇 |
1994年 | 4532篇 |
1993年 | 3936篇 |
1992年 | 3433篇 |
1991年 | 3146篇 |
1990年 | 2975篇 |
1989年 | 2907篇 |
1988年 | 2690篇 |
1987年 | 2315篇 |
1986年 | 2236篇 |
1985年 | 2626篇 |
1984年 | 2369篇 |
1983年 | 2238篇 |
1982年 | 2109篇 |
1981年 | 2019篇 |
1980年 | 1885篇 |
1979年 | 1890篇 |
1978年 | 1771篇 |
1977年 | 2085篇 |
1976年 | 2562篇 |
1975年 | 1583篇 |
1973年 | 1453篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
V. E. Gromov A. M. Glezer K. V. Morozov Yu. F. Ivanov K. V. Volkov 《Russian Metallurgy (Metally)》2015,2015(13):1094-1097
A layer-by-layer analysis of the structures, the phase compositions, and the defect substructures of differentially hardened rails has been carried by optical and transmission electron microscopy. It is found that the material volume of the rail head fillet is cooled faster than the volume located along the central axis. 相似文献
33.
34.
C. Doga Demirhan William W. Tso Joseph B. Powell Efstratios N. Pistikopoulos 《American Institute of Chemical Engineers》2019,65(7):e16498
Current ammonia production technologies have a significant carbon footprint. In this study, we present a process synthesis and global optimization framework to discover the efficient utilization of renewable resources in ammonia production. Competing technologies are incorporated in a process superstructure where biomass, wind, and solar routes are compared with the natural gas-based reference case. A deterministic global optimization-based branch-and-bound algorithm is used to solve the resulting large-scale nonconvex mixed-integer nonlinear programming problem (MINLP). Case studies for Texas, California, and Iowa are conducted to examine the effects of different feedstock prices and availabilities. Results indicate that profitability of ammonia production is highly sensitive to feedstock and electricity prices, as well as greenhouse gas (GHG) restrictions. Under strict 75% GHG reductions, biomass to ammonia route is found to be competitive with natural gas route, whereas wind and solar to ammonia routes require further improvement to compete with those two routes. © 2018 American Institute of Chemical Engineers AIChE J, 65: e16498 2019 相似文献
35.
Babilas R. Łoński W. Młynarek K. Bajorek A. Radoń A. 《Metallurgical and Materials Transactions A》2020,51(8):4215-4227
Metallurgical and Materials Transactions A - The influence of the chemical composition on the crystallization process, amorphous phase formation, and the anticorrosion properties of Al-Zr-Ni-Fe-Y... 相似文献
36.
Lin Haicheng Huang Wantong Zhao Kun Qiao Shuang Liu Zheng Wu Jian Chen Xi Ji Shuai-Hua 《Nano Research》2020,13(1):133-137
Nano Research - The isostructural and isoelectronic transition-metal-dichalcogenides 1T-TaS2 and 1T-TaSe2 are layered materials with intricate electronic structures. Combining the molecular beam... 相似文献
37.
Chengxiao Zhao Zupeng Chen Run Shi Xiaofei Yang Tierui Zhang 《Advanced materials (Deerfield Beach, Fla.)》2020,32(28):1907296
With the ambition of solving the challenges of the shortage of fossil fuels and their associated environmental pollution, visible-light-driven splitting of water into hydrogen and oxygen using semiconductor photocatalysts has emerged as a promising technology to provide environmentally friendly energy vectors. Among the current library of developed photocatalysts, organic conjugated polymers present unique advantages of sufficient light-absorption efficiency, excellent stability, tunable electronic properties, and economic applicability. As a class of rising photocatalysts, organic conjugated polymers offer high flexibility in tuning the framework of the backbone and porosity to fulfill the requirements for photocatalytic applications. In the past decade, significant progress has been made in visible-light-driven water splitting employing organic conjugated polymers. The recent development of the structural design principles of organic conjugated polymers (including linear, crosslinked, and supramolecular self-assembled polymers) toward efficient photocatalytic hydrogen evolution, oxygen evolution, and overall water splitting is described, thus providing a comprehensive reference for the field. Finally, current challenges and perspectives are also discussed. 相似文献
38.
Qi Yang Qilong Wu Yang Liu Shuiping Luo Xiaotong Wu Xixia Zhao Haiyuan Zou Baihua Long Wen Chen Yujia Liao Lanxi Li Pei Kang Shen Lele Duan Zewei Quan 《Advanced materials (Deerfield Beach, Fla.)》2020,32(36):2002822
Engineering novel Sn-based bimetallic materials could provide intriguing catalytic properties to boost the electrochemical CO2 reduction. Herein, the first synthesis of homogeneous Sn1−xBix alloy nanoparticles (x up to 0.20) with native Bi-doped amorphous SnOx shells for efficient CO2 reduction is reported. The Bi-SnOx nanoshells boost the production of formate with high Faradaic efficiencies (>90%) over a wide potential window (−0.67 to −0.92 V vs RHE) with low overpotentials, outperforming current tin oxide catalysts. The state-of-the-art Bi-SnOx nanoshells derived from Sn0.80Bi0.20 alloy nanoparticles exhibit a great partial current density of 74.6 mA cm−2 and high Faradaic efficiency of 95.8%. The detailed electrocatalytic analyses and corresponding density functional theory calculations simultaneously reveal that the incorporation of Bi atoms into Sn species facilitates formate production by suppressing the formation of H2 and CO. 相似文献
39.
40.