全文获取类型
收费全文 | 89753篇 |
免费 | 12348篇 |
国内免费 | 4173篇 |
专业分类
电工技术 | 6689篇 |
技术理论 | 2篇 |
综合类 | 6630篇 |
化学工业 | 16892篇 |
金属工艺 | 2705篇 |
机械仪表 | 2981篇 |
建筑科学 | 13612篇 |
矿业工程 | 5300篇 |
能源动力 | 1755篇 |
轻工业 | 8430篇 |
水利工程 | 2518篇 |
石油天然气 | 9183篇 |
武器工业 | 460篇 |
无线电 | 6700篇 |
一般工业技术 | 8315篇 |
冶金工业 | 4112篇 |
原子能技术 | 874篇 |
自动化技术 | 9116篇 |
出版年
2024年 | 440篇 |
2023年 | 1738篇 |
2022年 | 4769篇 |
2021年 | 5219篇 |
2020年 | 3603篇 |
2019年 | 3061篇 |
2018年 | 3237篇 |
2017年 | 3859篇 |
2016年 | 5167篇 |
2015年 | 5706篇 |
2014年 | 6806篇 |
2013年 | 6365篇 |
2012年 | 5884篇 |
2011年 | 5539篇 |
2010年 | 4261篇 |
2009年 | 4246篇 |
2008年 | 3945篇 |
2007年 | 5389篇 |
2006年 | 5258篇 |
2005年 | 4469篇 |
2004年 | 3169篇 |
2003年 | 2898篇 |
2002年 | 2208篇 |
2001年 | 1650篇 |
2000年 | 1461篇 |
1999年 | 1035篇 |
1998年 | 727篇 |
1997年 | 569篇 |
1996年 | 554篇 |
1995年 | 421篇 |
1994年 | 437篇 |
1993年 | 293篇 |
1992年 | 290篇 |
1991年 | 202篇 |
1990年 | 222篇 |
1989年 | 171篇 |
1988年 | 80篇 |
1987年 | 78篇 |
1986年 | 73篇 |
1985年 | 74篇 |
1984年 | 72篇 |
1983年 | 55篇 |
1982年 | 45篇 |
1981年 | 55篇 |
1980年 | 73篇 |
1979年 | 27篇 |
1964年 | 35篇 |
1962年 | 64篇 |
1959年 | 27篇 |
1955年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
Veronika Šoltészová Daniel Patel Stefan Bruckner Ivan Viola 《Computer Graphics Forum》2010,29(3):883-891
In this paper, we present a novel technique which simulates directional light scattering for more realistic interactive visualization of volume data. Our method extends the recent directional occlusion shading model by enabling light source positioning with practically no performance penalty. Light transport is approximated using a tilted cone‐shaped function which leaves elliptic footprints in the opacity buffer during slice‐based volume rendering. We perform an incremental blurring operation on the opacity buffer for each slice in front‐to‐back order. This buffer is then used to define the degree of occlusion for the subsequent slice. Our method is capable of generating high‐quality soft shadowing effects, allows interactive modification of all illumination and rendering parameters, and requires no pre‐computation. 相似文献
993.
Juyong Zhang Chunlin Wu Jianfei Cai Jianmin Zheng Xue‐cheng Tai 《Computer Graphics Forum》2010,29(2):517-526
This paper considers the problem of interactively finding the cutting contour to extract components from a given mesh. Some existing methods support cuts of arbitrary shape but require careful and tedious input from the user. Others need little user input however they are sensitive to user input and need a postprocessing step to smooth the generated jaggy cutting contours. The popular geometric snake can be used to optimize the cutting contour, but it cannot deal with the topology change. In this paper, we propose a geodesic curvature flow based framework to overcome all these problems. Since in many cases the meaningful cutting contour on a 3D mesh is locally shortest in the sense of some weighted curve length, the geodesic curvature flow is an ideal tool for our problem. It evolves the cutting contour to the nearby local minimum. We should mention that the previous numerical scheme, discretized geodesic curvature flow (dGCF) is too slow and has not been applied to mesh segmentation. With a careful observation to dGCF, we devise here a fast computation scheme called fast geodesic curvature flow (FGCF), which only needs to solve a smaller and easier problem. The initial cutting contour is generated by a variant of random walks algorithm, which is very fast and gives reasonable cutting result with little user input. Experiment results on the benchmark mesh segmentation data set show that our proposed framework is robust to user input and capable of producing good results reflecting geometric features and human shape perception. 相似文献
994.
Active contours with selective local or global segmentation: A new formulation and level set method 总被引:4,自引:0,他引:4
A novel region-based active contour model (ACM) is proposed in this paper. It is implemented with a special processing named Selective Binary and Gaussian Filtering RegularizedLevel Set(SBGFRLS) method, which first selectively penalizes the level set function to be binary, and then uses a Gaussian smoothing kernel to regularize it. The advantages of our method are as follows. First, a new region-based signed pressure force (SPF) function is proposed, which can efficiently stop the contours at weak or blurred edges. Second, the exterior and interior boundaries can be automatically detected with the initial contour being anywhere in the image. Third, the proposed ACM with SBGFRLS has the property of selective local or global segmentation. It can segment not only the desired object but also the other objects. Fourth, the level set function can be easily initialized with a binary function, which is more efficient to construct than the widely used signed distance function (SDF). The computational cost for traditional re-initialization can also be reduced. Finally, the proposed algorithm can be efficiently implemented by the simple finite difference scheme. Experiments on synthetic and real images demonstrate the advantages of the proposed method over geodesic active contours (GAC) and Chan–Vese (C–V) active contours in terms of both efficiency and accuracy. 相似文献
995.
996.
随着校园网办公自动化的不断普及,校园网络的安全问题也越来越受到更多地重视,它关系到学校的教学、科研和管理地工作是否能够正常进行。而传统的校园网安全防御体系已经很难适应当前复杂、大规模的攻击行为。虽然主动防御系统还存在着一些技术上的不足,但是它能够主动地检测、分析这些攻击行为,并对其及时阻断并提高系统的免疫力。该文以P2DR为实施模型,并结合现有的安全防御技术,构建了针对校园网存在的安全问题的主动防御系统及其相关的实施策略。 相似文献
997.
998.
Lili Wang Yan Tu Li Chen Panpan Zhang Kees Teunissen Ingrid Heynderickx 《Journal of the Society for Information Display》2010,18(6):405-414
Abstract— One of the most annoying distortions in (auto)stereoscopic displays is probably cross‐talk, visible as double edges, which is mainly caused by an imperfect separation of left‐ and right‐eye images. For different types of three‐dimensional (3‐D) displays, cross‐talk is caused by different origins, which could result in different levels of perceived image distortion. To evaluate the influence of (auto)stereoscopic display technology on cross‐talk perception, optical measurements and subjective assessments were performed with three different types of 3‐D displays. It is shown with natural still images that the 3‐D display technology with the lowest luminance and contrast level tolerates the highest level of cross‐talk, while still maintaining an acceptable image‐quality level. 相似文献
999.
介绍了传统的基于瞬时无功功率理论的ip-iq谐波电流检测算法;针对谐波检测环节产生的时延问题,提出了一种基于传统的瞬时无功功率理论、通过增加预置补偿角来消除时延的谐波电流实时检测新算法。Matlab动态仿真结果表明,利用增加预置补偿角的新算法进行谐波检测补偿效果较好,补偿后的电流波形接近正弦波,实现了谐波的实时检测,验证了该算法的可行性和有效性。 相似文献
1000.
为了对多源信息融合技术在海战场作战指挥方面发挥的作用进行定量描述,文章在多年信息融合测试评估研究的基础上,对海战场多源信息融合所涉及的能力指标计算、归一化及综合、测试评估系统设计、测试想定设计、适合信息融合的信息源模拟器建设等涉及的关键技术进行了描述,并给出了一个实际的评估例子。 相似文献