全文获取类型
收费全文 | 9750篇 |
免费 | 1002篇 |
国内免费 | 695篇 |
专业分类
电工技术 | 310篇 |
技术理论 | 8篇 |
综合类 | 616篇 |
化学工业 | 1690篇 |
金属工艺 | 326篇 |
机械仪表 | 211篇 |
建筑科学 | 810篇 |
矿业工程 | 379篇 |
能源动力 | 759篇 |
轻工业 | 332篇 |
水利工程 | 810篇 |
石油天然气 | 179篇 |
武器工业 | 28篇 |
无线电 | 1568篇 |
一般工业技术 | 1737篇 |
冶金工业 | 399篇 |
原子能技术 | 486篇 |
自动化技术 | 799篇 |
出版年
2024年 | 11篇 |
2023年 | 176篇 |
2022年 | 210篇 |
2021年 | 409篇 |
2020年 | 351篇 |
2019年 | 313篇 |
2018年 | 286篇 |
2017年 | 389篇 |
2016年 | 407篇 |
2015年 | 341篇 |
2014年 | 612篇 |
2013年 | 816篇 |
2012年 | 608篇 |
2011年 | 719篇 |
2010年 | 566篇 |
2009年 | 602篇 |
2008年 | 545篇 |
2007年 | 560篇 |
2006年 | 517篇 |
2005年 | 417篇 |
2004年 | 404篇 |
2003年 | 325篇 |
2002年 | 310篇 |
2001年 | 239篇 |
2000年 | 168篇 |
1999年 | 120篇 |
1998年 | 117篇 |
1997年 | 117篇 |
1996年 | 92篇 |
1995年 | 94篇 |
1994年 | 97篇 |
1993年 | 79篇 |
1992年 | 67篇 |
1991年 | 47篇 |
1990年 | 36篇 |
1989年 | 67篇 |
1988年 | 41篇 |
1987年 | 25篇 |
1986年 | 25篇 |
1985年 | 25篇 |
1984年 | 17篇 |
1983年 | 15篇 |
1982年 | 17篇 |
1981年 | 19篇 |
1980年 | 9篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1959年 | 3篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
N. Leclerc A. Michaud K. Sirois J.‐F. Morin M. Leclerc 《Advanced functional materials》2006,16(13):1694-1704
New electroactive and photoactive conjugated copolymers consisting of alternating 2,7‐carbazole and oligothiophene moieties linked by vinylene groups have been developed. Different oligothiophene units have been introduced to study the relationship between the polymer structure and the electronic properties. The resulting copolymers are characterized by UV‐vis spectroscopy, size‐exclusion chromatography, and thermal and electrochemical analyses. Bulk heterojunction photovoltaic cells from different copolymers and a soluble fullerene derivative, [6,6]‐phenyl‐C61 butyric acid methyl ester, have been fabricated, and promising preliminary results are obtained. For instance, non‐optimized devices using poly(N‐(4‐octyloxyphenyl)‐2,7‐carbazolenevinylene‐alt‐3″,4″‐dihexyl‐2,2′;5′,2″;5″,2″′;5″′,2″″‐quinquethiophenevinylene 1″,1″‐dioxide) as an absorbing and hole‐carrier semiconductor exhibit power conversion efficiency up to 0.8 % under air mass (AM) 1.5 illumination. These features make 2,7‐carbazolenevinylene‐based and related polymers attractive candidates for solar‐cell applications. 相似文献
992.
Automatic fog detection and estimation of visibility distance through use of an onboard camera 总被引:2,自引:0,他引:2
Nicolas Hautiére Jean-Philippe Tarel Jean Lavenant Didier Aubert 《Machine Vision and Applications》2006,17(1):8-20
In this paper, we will present a technique for measuring visibility distances under foggy weather conditions using a camera mounted onboard a moving vehicle. Our research has focused in particular on the problem of detecting daytime fog and estimating visibility distances; thanks to these efforts, an original method has been developed, tested and patented. The approach consists of dynamically implementing Koschmieder's law. Our method enables computing the meteorological visibility distance, a measure defined by the International Commission on Illumination (CIE) as the distance beyond which a black object of an appropriate dimension is perceived with a contrast of less than 5%. Our proposed solution is an original one, featuring the advantage of utilizing a single camera and necessitating the presence of just the road and sky in the scene. As opposed to other methods that require the explicit extraction of the road, this method offers fewer constraints by virtue of being applicable with no more than the extraction of a homogeneous surface containing a portion of the road and sky within the image. This image preprocessing also serves to identify the level of compatibility of the processed image with the set of Koschmieder's model hypotheses.
Nicolas Hautiére graduated from the École Nationale des Travaux Publics de l'État, France (2002). He received his M.S. and Ph.D. degree in computer vision, respectively, in 2002 and 2005 from Saint-Étienne University (France). From 2002, he is a researcher in the Laboratoire Central des Ponts et Chaussées (LCPC), Paris, France. His research interests include trafic engineering, computer vision, and pattern recognition.
Jean-Philippe Tarel graduated from the École Nationale des Ponts et Chaussées, Paris, France (1991). He received his Ph.D. degree in Applied Mathematics from Paris IX-Dauphine University in 1996 and he was with the Institut National de Recherche en Informatique et Automatique (INRIA) from 1991 to 1996. From 1997 to 1998, he was a research associate at Brown University, USA. From 1999, he is a researcher in the Laboratoire Central des Ponts et Chaussées (LCPC), Paris, France, and from 2001 to 2003 in the INRIA. His research interests include computer vision, pattern recognition, and shape modeling.
Jean Lavenant graduated from the École Nationale des Travaux Publics de l'État, Lyon, France (2001). He received the M.S. degree in Computer Vision from Jean Monnet university of Saint-Étienne in 2001. In 2001, he was a researcher in the Laboratoire Central des Ponts et Chaussées (LCPC). In 2002, he was a system engineer in Chicago (USA). He is currently an engineer for the french ministry of transports.
Didier Aubert received the M.S. and Ph.D. degree, respectively, in 1985 and 1989 from the National Polytechnical Institut of Grenoble (INPG). From 1989--1990, he worked as a research scientist on the development of an automatic road following system for the NAVLAB at Carnegie Mellon University. From 1990–1994, he worked in the research department of a private company (ITMI). During this period he was the project leader of several projects dealing with computer vision. He is currently a researcher at INRETS since 1995 and works on Road traffic measurements, crowd monitoring, automated highway systems, and driving assistance systems for vehicles. He is an image processing expert for several companies, teaches at Universities (Paris VI, Paris XI, ENPC, ENST) and is at the editorial board of RTS (Research - Transport - Safety). 相似文献
993.
基于有限体积法及FDS格式的感潮河段二维泥沙冲淤模型 总被引:3,自引:0,他引:3
本文以木兰溪下游裁弯河段为例,建立了有限体积法的水平二维非恒定流均匀沙不平衡输移计算模型。采用黎曼近似解通量差分裂(FDS)格式计算通过各单元边的水流、含沙量法向数值通量,并应用相关的悬移质、推移质河床变形计算公式计算冲淤变化。数值模型经相应的河工模型试验资料率定、检验后,预测了裁弯工程建成后河道可能的冲淤变化,为工程设计和施工提供依据。 相似文献
994.
大位移水平井两层不稳定岩屑传输模型研究 总被引:9,自引:0,他引:9
本文在Martins提出的两层模型基础上.考虑了悬浮层岩屑颗粒的扩散,建立了与时间相关的两层不稳定岩屑传输数学模型。用有限容积法求解了此偏微分方程组。研究结果表明:在一定条件下,环空岩屑传输流动达到稳定状态需要很长的时间,这表明用稳定流动模型来模拟环空中岩屑传输问题有其局限性;粘度的增加、环空返速的提高和机械钻速的降低有助于水平环空中岩屑的传输。 相似文献
995.
本文简要介绍了钱宁从事泥沙研究事业的一生及其主要成就;对《泥沙运动力学》一书进行了评述,并分章扼要说明及主要内容。与此同时,说明了作者对泥沙研究一些问题的观点。 相似文献
996.
997.
998.
999.
论黄河干支流悬移质粒径与含沙量关系 总被引:3,自引:0,他引:3
黄河干支流资料表明,河流中悬移质泥沙粗细的变化既有随着含沙量的增加而变粗的,也有随着含沙量的增加而变细的。本文分析了黄河干支流泥沙粒径与含沙量关系的不同资料,提出了较大含沙量情况下泥沙粒径与含沙量的统计关系,解析和讨论了所推导出的悬移质泥沙粒径与含沙量的关系。 相似文献
1000.