全文获取类型
收费全文 | 217116篇 |
免费 | 2804篇 |
国内免费 | 656篇 |
专业分类
电工技术 | 4267篇 |
综合类 | 140篇 |
化学工业 | 30815篇 |
金属工艺 | 7981篇 |
机械仪表 | 5809篇 |
建筑科学 | 4897篇 |
矿业工程 | 834篇 |
能源动力 | 5156篇 |
轻工业 | 15674篇 |
水利工程 | 1940篇 |
石油天然气 | 3042篇 |
武器工业 | 8篇 |
无线电 | 28625篇 |
一般工业技术 | 40475篇 |
冶金工业 | 49582篇 |
原子能技术 | 3708篇 |
自动化技术 | 17623篇 |
出版年
2021年 | 1474篇 |
2020年 | 1115篇 |
2019年 | 1521篇 |
2018年 | 2405篇 |
2017年 | 2383篇 |
2016年 | 2521篇 |
2015年 | 1767篇 |
2014年 | 3049篇 |
2013年 | 9109篇 |
2012年 | 5151篇 |
2011年 | 6983篇 |
2010年 | 5639篇 |
2009年 | 6483篇 |
2008年 | 6966篇 |
2007年 | 7091篇 |
2006年 | 6368篇 |
2005年 | 5986篇 |
2004年 | 5859篇 |
2003年 | 5662篇 |
2002年 | 5435篇 |
2001年 | 5632篇 |
2000年 | 5250篇 |
1999年 | 5775篇 |
1998年 | 16024篇 |
1997年 | 10673篇 |
1996年 | 8267篇 |
1995年 | 6120篇 |
1994年 | 5299篇 |
1993年 | 5345篇 |
1992年 | 3673篇 |
1991年 | 3474篇 |
1990年 | 3463篇 |
1989年 | 3301篇 |
1988年 | 3028篇 |
1987年 | 2473篇 |
1986年 | 2557篇 |
1985年 | 2882篇 |
1984年 | 2591篇 |
1983年 | 2339篇 |
1982年 | 2112篇 |
1981年 | 2283篇 |
1980年 | 2026篇 |
1979年 | 1900篇 |
1978年 | 1872篇 |
1977年 | 2238篇 |
1976年 | 2900篇 |
1975年 | 1611篇 |
1974年 | 1534篇 |
1973年 | 1481篇 |
1972年 | 1231篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
31.
32.
An explicit extraction of the retinal vessel is a standout amongst the most significant errands in the field of medical imaging to analyze both the ophthalmological infections, for example, Glaucoma, Diabetic Retinopathy (DR), Retinopathy of Prematurity (ROP), Age-Related Macular Degeneration (AMD) as well as non retinal sickness such as stroke, hypertension and cardiovascular diseases. The state of the retinal vasculature is a significant indicative element in the field of ophthalmology. Retinal vessel extraction in fundus imaging is a difficult task because of varying size vessels, moderately low distinction, and presence of pathologies such as hemorrhages, microaneurysms etc. Manual vessel extraction is a challenging task due to the complicated nature of the retinal vessel structure, which also needs strong skill set and training. In this paper, a supervised technique for blood vessel extraction in retinal images using Modified Adaboost Extreme Learning Machine (MAD-ELM) is proposed. Firstly, the fundus image preprocessing is done for contrast enhancement and in-homogeneity correction. Then, a set of core features is extracted, and the best features are selected using “minimal Redundancy-maximum Relevance (mRmR).” Later, using MAD-ELM method vessels and non vessels are classified. DRIVE and DR-HAGIS datasets are used for the evaluation of the proposed method. The algorithm’s performance is assessed based on accuracy, sensitivity and specificity. The proposed technique attains accuracy of 0.9619 on the DRIVE database and 0.9519 on DR-HAGIS database, which contains pathological images. Our results show that, in addition to healthy retinal images, the proposed method performs well in extracting blood vessels from pathological images and is therefore comparable with state of the art methods. 相似文献
33.
34.
35.
36.
37.
38.
39.
H. Cherfouh O. Fellahi T. Hadjersi B. Marsan 《International Journal of Hydrogen Energy》2018,43(6):3431-3440
This work aims at developing a new composite material based on nanosized semiconducting CuInS2 (CIS) particles combined with silicon nanowires grown on a silicon substrate (SiNWs/Si) for photoelectrochemical (PEC)-splitting of water. The CIS particles were prepared via a colloidal method using N-methylimidazole (NMI) as the solvent and an annealing treatment. The SiNWs were obtained by chemical etching of silicon (100) substrates assisted by a metal. The CIS/SiNWs/Si composite material was obtained by deposition of an aliquot of a suspension of CIS particles onto the SiNWs/Si substrate, using spin coating followed by a drying step. The XRD pattern demonstrated that CuInS2 grows in the tetragonal/chalcopyrite phase, while SiNWs/Si presents a cubic structure. The SEM images show semi-spherical particles (~10 nm) distributed on the surface of silicon nanowires (~10 μm). The EIS measurements reveal n-type conductivity for CIS, SiNWs/Si and CIS/SiNWs/Si materials, which could favour the oxidation reaction of water molecules. 相似文献
40.