全文获取类型
收费全文 | 118360篇 |
免费 | 10386篇 |
国内免费 | 5274篇 |
专业分类
电工技术 | 6815篇 |
技术理论 | 6篇 |
综合类 | 7569篇 |
化学工业 | 19527篇 |
金属工艺 | 7410篇 |
机械仪表 | 8360篇 |
建筑科学 | 9582篇 |
矿业工程 | 4001篇 |
能源动力 | 3411篇 |
轻工业 | 7588篇 |
水利工程 | 2110篇 |
石油天然气 | 8425篇 |
武器工业 | 1017篇 |
无线电 | 12873篇 |
一般工业技术 | 13803篇 |
冶金工业 | 5899篇 |
原子能技术 | 1343篇 |
自动化技术 | 14281篇 |
出版年
2024年 | 574篇 |
2023年 | 2156篇 |
2022年 | 3803篇 |
2021年 | 5163篇 |
2020年 | 4054篇 |
2019年 | 3319篇 |
2018年 | 3563篇 |
2017年 | 4033篇 |
2016年 | 3718篇 |
2015年 | 5128篇 |
2014年 | 6169篇 |
2013年 | 7247篇 |
2012年 | 7789篇 |
2011年 | 8076篇 |
2010年 | 7009篇 |
2009年 | 6622篇 |
2008年 | 6390篇 |
2007年 | 6108篇 |
2006年 | 6392篇 |
2005年 | 5495篇 |
2004年 | 3504篇 |
2003年 | 3285篇 |
2002年 | 3112篇 |
2001年 | 2810篇 |
2000年 | 2656篇 |
1999年 | 2936篇 |
1998年 | 2316篇 |
1997年 | 1913篇 |
1996年 | 1893篇 |
1995年 | 1562篇 |
1994年 | 1282篇 |
1993年 | 823篇 |
1992年 | 736篇 |
1991年 | 499篇 |
1990年 | 400篇 |
1989年 | 336篇 |
1988年 | 267篇 |
1987年 | 173篇 |
1986年 | 155篇 |
1985年 | 89篇 |
1984年 | 69篇 |
1983年 | 56篇 |
1982年 | 54篇 |
1981年 | 45篇 |
1980年 | 35篇 |
1979年 | 26篇 |
1977年 | 10篇 |
1976年 | 23篇 |
1975年 | 10篇 |
1974年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Research funding has been seen as one of the most important resource in the reward system of science. And usage of publications denotes an interesting perspective of user behavior in scientific communication. This study aims to address the relationship between funding and Usage Count, which is a new metrics item established on the platform of Web of Science. Full records of 300,010 articles published in 2013 were downloaded in October 2015, and divided into six disciplines, including information science library science, education educational research, economics, computer science, materials science, and chemistry. Seven indicators were proposed to measure the impact, including Funding rate, Citation per paper, Usage rate, Usage per paper, Citation difference, Usage difference, and Conversion rate. It concluded funding has impact on usage and citation, and funded papers attract more usage, but varying in different disciplines. Usage Count can be used in the extension of citation metrics but with limits. This study originally engages with usage metrics and detected that there is positive correlation between usage and funding. 相似文献
32.
To minimize the mass and increase the bearing failure load of composite doublelap bolted joints, a three-step optimization strategy including feasible region reduction,
optimization model decoupling and optimization was presented. In feasible region
reduction, the dimensions of the feasible design region were reduced by selecting dominant
design variables from numerous multilevel parameters by sensitivity analyses, and the
feasible regions of variables were reduced by influence mechanism analyses. In model
decoupling, the optimization model with a large number of variables was divided into
various sub-models with fewer variables by variance analysis. In the third step, the
optimization sub-models were solved one by one using a genetic algorithm, and the
modified characteristic curve method was adopted as the failure prediction method. Based
on the proposed optimization method, optimization of a double-lap single-bolt joint was
performed using the ANSYS® code. The results show that the bearing failure load increased
by 13.5% and that the mass decreased by 8.7% compared with those of the initial design of
the joint, which validated the effectiveness of the three-step optimization strategy. 相似文献
33.
热轧态中锰TRIP钢首先经650 ℃退火2 h,随后在550 ℃进行等温时效热处理,采用场发射扫描电镜(FE-SEM)研究该钢中P的偏聚和时效析出行为的变化情况。结果表明,中锰TRIP钢中P在晶界的偏聚是一种非平衡偏聚现象,临界时间约为50 h,与理论计算结果48 h较为吻合。在局部偏聚区域内,C与P存在共偏聚的关系,即P偏聚量高的地方,C含量也高。而合金元素Nb具有抑制P偏聚的效果,在20~70 h时效时间内,可以相对降低6.57%~19.5%的最大P偏聚量。根据电子背散射衍射(EBSD)菊池线分析,P偏聚量低于2.28at%时,P为固溶状态,高于2.28at.%时,P为析出状态。 相似文献
34.
Semiconductors - The performance of InGaN/GaN multiple quantum well (MQW) solar cells with five different Si-doping concentrations, namely 0, 4 × 1017 cm–3, 1 × 1018 cm–3, 3... 相似文献
35.
Guankui Long Yecheng Zhou Mingtao Zhang Randy Sabatini Abdullah Rasmita Li Huang Girish Lakhwani Weibo Gao 《Advanced materials (Deerfield Beach, Fla.)》2019,31(17)
Hybrid organic–inorganic perovskites (HOIPs), in particular 3D HOIPs, have demonstrated remarkable properties, including ultralong charge‐carrier diffusion lengths, high dielectric constants, low trap densities, tunable absorption and emission wavelengths, strong spin–orbit coupling, and large Rashba splitting. These superior properties have generated intensive research interest in HOIPs for high‐performance optoelectronics and spintronics. Here, 3D hybrid organic–inorganic perovskites that implant chirality through introducing the chiral methylammonium cation are demonstrated. Based on structural optimization, phonon spectra, formation energy, and ab initio molecular dynamics simulations, it is found that the chirality of the chiral cations can be successfully transferred to the framework of 3D HOIPs, and the resulting 3D chiral HOIPs are both kinetically and thermodynamically stable. Combining chirality with the impressive optical, electrical, and spintronic properties of 3D perovskites, 3D chiral perovskites is of great interest in the fields of piezoelectricity, pyroelectricity, ferroelectricity, topological quantum engineering, circularly polarized optoelectronics, and spintronics. 相似文献
36.
37.
Xueliang Wang Huiqin Yin Wenguan Liu Guojun Yu Jian He Zhongfeng Tang Long Yan 《工业材料与腐蚀》2020,71(6):931-937
Understanding the corrosion of molten ZnCl2 on metal surfaces is significant for the corrosion protection of metals, sustainable use of molten salts, preparation of ZnO coatings, and so on. In this paper, surfaces of pure Ni, Cr, and Fe corroded by molten ZnCl2 were investigated. The results show that Ni suffered very slight corrosion, while Cr experienced more serious corrosion than Ni, but lighter corrosion than Fe. The morphology of the corrosion of Cr and Fe, respectively, presented pitting and intergranular corrosion characteristics. Furthermore, nanostructured ZnO coatings were obtained on the surfaces of Ni and Fe, but not on the surface of Cr. The ZnO coating on the Ni surface was doped with a small amount of Zn5(OH)8Cl2, and the ZnO coating on the Fe surface was doped with ZnFe2O4 and Zn2OCl2. The coatings on the Ni and Fe surfaces had an average thickness of 1.5 and 50 μm, respectively. 相似文献
38.
Yejun Wu Bowen Yan Juan Zhou Huizhang Lian Xiaojun Yu Jianxin Zhao Hao Zhang Wei Chen Daming Fan 《Journal of food science》2020,85(10):3282-3292
39.
40.
Zhao Hongliang Lu Tingting Liu Fengqin Yin Pan Wang Sen 《JOM Journal of the Minerals, Metals and Materials Society》2019,71(5):1643-1649
JOM - The Isa/Ausmelt smelting technology with a top submerged lance (TSL) has been extensively used in copper smelting processes. However, the TSL is extremely vulnerable to damage and failure... 相似文献