全文获取类型
收费全文 | 50740篇 |
免费 | 4349篇 |
国内免费 | 2187篇 |
专业分类
电工技术 | 2880篇 |
技术理论 | 7篇 |
综合类 | 3263篇 |
化学工业 | 8593篇 |
金属工艺 | 2949篇 |
机械仪表 | 3219篇 |
建筑科学 | 3585篇 |
矿业工程 | 1626篇 |
能源动力 | 1583篇 |
轻工业 | 3178篇 |
水利工程 | 787篇 |
石油天然气 | 3176篇 |
武器工业 | 467篇 |
无线电 | 5931篇 |
一般工业技术 | 6457篇 |
冶金工业 | 2475篇 |
原子能技术 | 707篇 |
自动化技术 | 6393篇 |
出版年
2024年 | 264篇 |
2023年 | 932篇 |
2022年 | 1567篇 |
2021年 | 2221篇 |
2020年 | 1672篇 |
2019年 | 1372篇 |
2018年 | 1566篇 |
2017年 | 1807篇 |
2016年 | 1622篇 |
2015年 | 2096篇 |
2014年 | 2669篇 |
2013年 | 3203篇 |
2012年 | 3360篇 |
2011年 | 3611篇 |
2010年 | 3033篇 |
2009年 | 2907篇 |
2008年 | 2876篇 |
2007年 | 2731篇 |
2006年 | 2625篇 |
2005年 | 2234篇 |
2004年 | 1572篇 |
2003年 | 1351篇 |
2002年 | 1339篇 |
2001年 | 1164篇 |
2000年 | 1170篇 |
1999年 | 1166篇 |
1998年 | 980篇 |
1997年 | 824篇 |
1996年 | 765篇 |
1995年 | 584篇 |
1994年 | 496篇 |
1993年 | 331篇 |
1992年 | 269篇 |
1991年 | 199篇 |
1990年 | 172篇 |
1989年 | 135篇 |
1988年 | 110篇 |
1987年 | 59篇 |
1986年 | 63篇 |
1985年 | 34篇 |
1984年 | 28篇 |
1983年 | 27篇 |
1982年 | 24篇 |
1981年 | 14篇 |
1980年 | 8篇 |
1979年 | 7篇 |
1976年 | 6篇 |
1973年 | 2篇 |
1970年 | 2篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
993.
本文结合广东境内近期建设的几座500kV变电站,介绍日本三菱公司生产的500kV H-GIS的结构和技术特 点,以及运输、安装、试验的情况。 相似文献
994.
The effect and the action mechanism of lanthanum on GF43 plantlet in vitro were studied. The results of experiments show that root growth rate and dry weight of GF43 by LaCI3 treatments increase. The activities of antioxidant enzymes in root system such as superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) apparently enhance. Moreover O^-2 and malond ialdehyde (MDA) contents and cell membrane permeability of GF43 are decreased by LaC13. The relatively stable membrane structure of cell could also be maintained and the root ageing of GF43 plantlet in vitro delays. 相似文献
995.
996.
本文介绍了新一代的可编程自动化控制器(PACs)的概念、产生背景及现状,分析了其构成方式、技术优势,最后阐述了其应用前景及发展趋势。 相似文献
997.
Hee Seok Song Jae Kyeong Kim Yeong Bin Cho Soung Hie Kim 《Artificial Intelligence Review》2004,21(2):161-184
Customer retention is an increasinglypressing issue in today's competitiveenvironment. This paper proposes a personalizeddefection detection and prevention procedurebased on the observation that potentialdefectors have a tendency to take a couple ofmonths or weeks to gradually change theirbehaviour (i.e., trim-out their usage volume)before their eventual withdrawal. For thispurpose, we suggest a SOM (Self-Organizing Map)based procedure to determine the possiblestates of customer behaviour from pastbehaviour data. Based on this staterepresentation, potential defectors aredetected by comparing their monitoredtrajectories of behaviour states with frequentand confident trajectories of past defectors.Also, the proposed procedure is extended toprevent the defection of potential defectors byrecommending the desirable behaviour state forthe next period so as to lower the likelihoodof defection. For the evaluation of theproposed procedure, a case study has beenconducted for a Korean online game site. Theresult demonstrates that the proposed procedureis effective for defection prevention andefficiently detects potential defectors withoutdeterioration of prediction accuracy whencompared to that of the MLP (Multi-LayerPerceptron) neural networks. 相似文献
998.
999.
Xi-Wen Zhang Author Vitae Ji-Qiang Song Author Vitae Author Vitae Shi-Jie Cai Author Vitae 《Pattern recognition》2004,37(2):351-361
Extracting karyocytes and their components from microscopic bone marrow images is prerequisite for computer-aided early diagnosis of hemopathy. Most existing methods assume all pixels belonging to a karyon region or a cytoplasm region have similar colors. Practically, the color of neither a karyon nor a cytoplasm in a microscopic image is homogeneous in the pixel level. Therefore, the regional color features of a region are emphasized in this paper. Based on this observation, we propose a novel method to karyocyte extraction that first identifies a karyon by 4-connected block growing from a karyon feature block, then identifies feature blocks of its cytoplasm based on the extracted karyon, and finally extracts all cytoplasm regions by growing the cytoplasm feature blocks. Combining the karyon region and the corresponding cytoplasm regions can attain a complete karyocyte. Experimental results show that the proposed method is effective and robust. 相似文献
1000.
Kawamori E Lee JY Huang YJ Syugu WJ Song SX Hsieh TY Cheng CZ 《The Review of scientific instruments》2011,82(9):093502
This paper presents a newly developed lithium plasma emitter, which can provide quiescent and low-temperature collisionless conditions for magnetized plasma experiments. This plasma emitter generates thermal emissions of lithium ions and electrons to produce a lithium plasma. Lithium type beta-eucryptite and lanthanum-hexaboride (LaB(6)) powders were mixed and directly heated with a tungsten heater to synthesize ion and electron emissions. As a result, a plasma with a diameter of ~15 cm was obtained in a magnetic mirror configuration. The typical range of electron density was 10(12)-10(13) m(-3) and that of electron temperature was 0.1-0.8 eV with the emitter operation temperature of about 1500 K. The amplitude fluctuations for the plasma density were lower than 1%. 相似文献