全文获取类型
收费全文 | 11833篇 |
免费 | 2739篇 |
国内免费 | 1840篇 |
专业分类
电工技术 | 413篇 |
综合类 | 1033篇 |
化学工业 | 1399篇 |
金属工艺 | 206篇 |
机械仪表 | 674篇 |
建筑科学 | 118篇 |
矿业工程 | 54篇 |
能源动力 | 34篇 |
轻工业 | 391篇 |
水利工程 | 44篇 |
石油天然气 | 61篇 |
武器工业 | 60篇 |
无线电 | 2299篇 |
一般工业技术 | 1139篇 |
冶金工业 | 645篇 |
原子能技术 | 148篇 |
自动化技术 | 7694篇 |
出版年
2024年 | 158篇 |
2023年 | 460篇 |
2022年 | 1002篇 |
2021年 | 1056篇 |
2020年 | 729篇 |
2019年 | 552篇 |
2018年 | 470篇 |
2017年 | 531篇 |
2016年 | 584篇 |
2015年 | 641篇 |
2014年 | 812篇 |
2013年 | 715篇 |
2012年 | 895篇 |
2011年 | 996篇 |
2010年 | 830篇 |
2009年 | 804篇 |
2008年 | 833篇 |
2007年 | 807篇 |
2006年 | 654篇 |
2005年 | 624篇 |
2004年 | 506篇 |
2003年 | 414篇 |
2002年 | 289篇 |
2001年 | 219篇 |
2000年 | 138篇 |
1999年 | 129篇 |
1998年 | 96篇 |
1997年 | 59篇 |
1996年 | 44篇 |
1995年 | 49篇 |
1994年 | 43篇 |
1993年 | 28篇 |
1992年 | 21篇 |
1991年 | 15篇 |
1990年 | 16篇 |
1989年 | 26篇 |
1988年 | 15篇 |
1987年 | 10篇 |
1986年 | 8篇 |
1985年 | 23篇 |
1984年 | 9篇 |
1983年 | 16篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1979年 | 8篇 |
1966年 | 5篇 |
1965年 | 5篇 |
1964年 | 6篇 |
1960年 | 5篇 |
1957年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
基于区域GAC模型的二值化水平集图像分割算法 总被引:2,自引:1,他引:1
针对测地线主动轮廓(GAC)模型进行了改进,提出了一种基于区域的GAC模型.通过构造基于区域统计信息的符号压力函数取代边界停止函数,有效解决了弱边界目标或离散状边界目标的分割问题.该模型采用二值化水平集方法实现,避免了传统实现方法水平集函数需要重新初始化为符号距离函数,从而导致稳定性差、计算量大、实现复杂等缺点.对不同类型图像的试验结果表明:该算法迭代收敛速度比GAC模型传统实现方法明显加快,且可有效防止边界泄漏,分割效果优于传统GAC模型与C-V模型. 相似文献
12.
13.
在分析了中国书画印章图像特点的基础上,针对基于内容的书画作品图像检索领域中存在的"语义鸿沟"问题,提出了一种自动提取中国书画作品中印章图像的方法,并设计实现了该算法.通过对提取效果进行分析,证明该方法有较高提取率,这对书画作品中图像语义和特定图像鉴别的研究有重要意义. 相似文献
14.
15.
C. Fellner F. Fellner R. Schmitt T. Helmberger N. Obletter H. Böhm-jurkovic 《Magma (New York, N.Y.)》1994,2(1):51-59
Fast SE imaging provides considerable measure time reduction, high signal-to-noise ratios as well as similar contrast behavior compared to conventional SE sequences. Besides TR and TEeff, echo train length (ETL), interecho time , and-space trajectory determine image contrast and image quality in fast SE sequences. True proton density contrast (CSF hypointense) and not too strong T2 contrast are essential requirements in routine brain MRI. A Turbo SE sequence with very short echo train length (ETL=3), short TEeff and short interecho time (17 ms), and TR=2000 ms was selected for proton density contrast; a Turbo SE sequence with ETL=7, TEeff=90 ms, =22 ms, and TR=3250 ms was selected for T2-weighted images. Using both single-echo Turbo SE sequences yielded 50% measure time reduction compared to the conventional SE technique. Conventional SE and optimized Turbo SE sequences were compared in 150 patients resulting in very similar signal and contrast behavior. Furthermore, reduced flow artifacts in proton density—and especially in T2-weighted Turbo SE images—and better contrast of high-intensity lesions in proton density-weighted Turbo SE images were found. Slightly reduced edge sharpness—mainly in T2-weighted Turbo SE images—did not reduce diagnostic reliability. Differences between conventional and Turbo SE images concerning image contrast and quality are explained regarding special features of fast SE technique.Address for correspondence: Institut für Röntgendiagnostik, Klinikum der Universität Regensburg, Franz-Josef-Strauß-Allee 11, 93042 Regensburg, Germany. Additional reprints of this chapter may be obtained from the Reprints Department, Chapman & Hall, One Venn Plaza, New York, NY 10119. 相似文献
16.
17.
During the past decade, feature extraction and knowledge acquisition based on video analysis have been extensively researched and tested on many applications such as closed-circuit television(CCTV)data analysis, large-scale public event control, and other daily security monitoring and surveillance operations with various degrees of success. However, since the actual video process is a multi-phased one and encompasses extensive theories and techniques ranging from fundamental image processing, computational geometry and graphics, and machine vision, to advanced artificial intelligence, pattern analysis, and even cognitive science, there are still many important problems to resolve before it can be widely applied. Among them, video event identification and detection are two prominent ones. Comparing with the most popular frame-to-frame processing mode of most of today's approaches and systems, this project reorganizes video data as a 3D volume structure that provides the hybrid spatial and temporal information in a unified space. This paper reports an innovative technique to transform original video frames to 3D volume structures denoted by spatial and temporal features. It then highlights the volume array structure in a so-called "pre-suspicion" mechanism for a later process. The focus of this report is the development of an effective and efficient voxel-based segmentation technique suitable to the volumetric nature of video events and ready for deployment in 3D clustering operations. The paper is concluded with a performance evaluation of the devised technique and discussion on the future work for accelerating the pre-processing of the original video data. 相似文献
18.
Antonio C. Sobieranski Daniel D. Abdala Eros Comunello Aldo von Wangenheim 《Pattern recognition letters》2009,30(16):127
In this paper we describe an experiment where we studied empirically the application of a learned distance metric to be used as discrimination function for an established color image segmentation algorithm. For this purpose we chose the Mumford–Shah energy functional and the Mahalanobis distance metric. The objective was to test our approach in an objective and quantifiable way on this specific algorithm employing this particular distance model, without making generalization claims. The empirical validation of the results was performed in two experiments: one applying the resulting segmentation method on a subset of the Berkeley Image Database, an exemplar image set possessing ground-truths and validating the results against the ground-truths using two well-known inter-cluster validation methods, namely, the Rand and BGM indexes, and another experiment using images of the same context divided into training and testing set, where the distance metric is learned from the training set and then applied to segment all the images. The obtained results suggest that the use of the specified learned distance metric provides better and more robust segmentations, even if no other modification of the segmentation algorithm is performed. 相似文献
19.
20.