全文获取类型
收费全文 | 16570篇 |
免费 | 1452篇 |
国内免费 | 750篇 |
专业分类
电工技术 | 986篇 |
技术理论 | 1篇 |
综合类 | 1044篇 |
化学工业 | 2984篇 |
金属工艺 | 915篇 |
机械仪表 | 1132篇 |
建筑科学 | 1130篇 |
矿业工程 | 508篇 |
能源动力 | 474篇 |
轻工业 | 1106篇 |
水利工程 | 345篇 |
石油天然气 | 992篇 |
武器工业 | 125篇 |
无线电 | 1797篇 |
一般工业技术 | 2187篇 |
冶金工业 | 762篇 |
原子能技术 | 211篇 |
自动化技术 | 2073篇 |
出版年
2024年 | 85篇 |
2023年 | 318篇 |
2022年 | 488篇 |
2021年 | 727篇 |
2020年 | 605篇 |
2019年 | 458篇 |
2018年 | 545篇 |
2017年 | 579篇 |
2016年 | 483篇 |
2015年 | 662篇 |
2014年 | 824篇 |
2013年 | 1016篇 |
2012年 | 1019篇 |
2011年 | 1022篇 |
2010年 | 980篇 |
2009年 | 867篇 |
2008年 | 827篇 |
2007年 | 856篇 |
2006年 | 880篇 |
2005年 | 717篇 |
2004年 | 518篇 |
2003年 | 545篇 |
2002年 | 577篇 |
2001年 | 469篇 |
2000年 | 413篇 |
1999年 | 400篇 |
1998年 | 341篇 |
1997年 | 304篇 |
1996年 | 259篇 |
1995年 | 203篇 |
1994年 | 172篇 |
1993年 | 117篇 |
1992年 | 101篇 |
1991年 | 83篇 |
1990年 | 63篇 |
1989年 | 49篇 |
1988年 | 41篇 |
1987年 | 25篇 |
1986年 | 31篇 |
1985年 | 10篇 |
1984年 | 16篇 |
1983年 | 9篇 |
1982年 | 9篇 |
1981年 | 11篇 |
1980年 | 15篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 8篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 19 毫秒
21.
Benedikt Ley Corinna Ogonowski Jan Hess Tim Reichling Lin Wan Volker Wulf 《Behaviour & Information Technology》2014,33(8):815-828
Technological infrastructure at home is changing continuously and is becoming increasingly interconnected. Media devices, including the TV set, provide access to the Internet and offer manifold opportunities to consume media on demand. Additionally, personal devices, such as smartphones, also enable flexible consumption and sharing of media. Questions about how these technologies change the user's media usage and how these changes affect the social structure of a household, however, remain largely unanswered. In order to gain insight into the adoption of new technologies into daily routines, we explored these changes in respect of people's media usage in a qualitative long-term Living Lab study. We will present findings regarding personal routines, flexible integration of new devices into existing practices, influences on households as social systems and related issues in device access and collective use. We will highlight potentials and conflicts regarding device shifts and roles; restrictions in device access; social influences in the living room; and individual changes in media consumption. 相似文献
22.
23.
万来志 《重庆科技学院学报(社会科学版)》2010,(21)
抗日战争是中华民族历史上的一次大浩劫,中国人民为此承受了太多的痛苦与磨难,特别是对于肩负着国家与民族振兴使命的青年更是如此.分析战时青年的心理变化及原因,指出政府和社会对青年人的心理没有采取恰当的方法进行有效的疏导,提出要总结和吸取历史的经验教训,为我们今天应对大灾难提供借鉴. 相似文献
24.
Effects of Copper Coating on the Crystalline Structure of Fine Barium Titanate Particles 总被引:1,自引:0,他引:1
Xinghua Liu Wan Y. Shih Wei-Heng Shih 《Journal of the American Ceramic Society》1997,80(11):2781-2788
We have investigated the effect of a metal coating—copper—on the tetragonal structure of fine barium titanate (BaTiO3 ) particles. The BaTiO3 particles were synthesized by a sol-gel method and heat treated at temperatures >900°C for various amounts of time before coating. The copper coating was achieved by an electroless coating technique. The transmission electron microscopy micrographs revealed that the coated powder contained fine BaTiO3 particles that were embedded in copper patches. The X-ray diffractometry patterns showed that the copper coating increased the c/a ratio of the fine BaTiO3 particles. For powders that were heat treated at 900°C for 10 h and were initially cubic, the copper coating changed the c/a ratio, from 1 to 1.0034. For powders that were calcined at 900°C for 20 h and were initially tetragonal, the copper coating further enhanced the c/a ratio, from 1.0028 to 1.0043. When the copper-coated BaTiO3 particles were oxidized, the c/a ratio was reduced to a value that was approximately equal to or below that of the uncoated powders. A conductive coating can eliminate the depolarization energy of an insulating polar particle. The fact that the copper coating promoted the polar tetragonal phase but the nonconductive copper-oxide coating did not was consistent with the interpretation that the presence of the cubic phase (nonpolar) in small BaTiO3 particles was caused by the depolarization effect. 相似文献
25.
本文讨论了焊接结构生产技术改造的有关问题,包括总思路及总目标、自动化的基本框架、按低成本自动化的原则设计生产线和关键技术问题的论述。 相似文献
26.
Shaohui Mei Genliang Guan Zhiyong Wang Shuai Wan Mingyi He David Dagan Feng 《Pattern recognition》2015
The rapid growth of video data demands both effective and efficient video summarization methods so that users are empowered to quickly browse and comprehend a large amount of video content. In this paper, we formulate the video summarization task with a novel minimum sparse reconstruction (MSR) problem. That is, the original video sequence can be best reconstructed with as few selected keyframes as possible. Different from the recently proposed convex relaxation based sparse dictionary selection method, our proposed method utilizes the true sparse constraint L0 norm, instead of the relaxed constraint L2,1 norm, such that keyframes are directly selected as a sparse dictionary that can well reconstruct all the video frames. An on-line version is further developed owing to the real-time efficiency of the proposed MSR principle. In addition, a percentage of reconstruction (POR) criterion is proposed to intuitively guide users in obtaining a summary with an appropriate length. Experimental results on two benchmark datasets with various types of videos demonstrate that the proposed methods outperform the state of the art. 相似文献
27.
瞿海军 《计算机光盘软件与应用》2011,(6)
本文从安全服务运营管理角度出发探讨了当前移动通信业务开展中面临的各项安全成胁,并提出了移动通信业务的安全应用策略,对促进移动业务实现高质、高效、安全、持续的服务有重要的推进作用. 相似文献
28.
Image preview is a convenient way to browse large or multiple images on small displays. However, current signal-level image
resampling algorithms may remove many features of interest in the preview image. In this paper, we propose perceptual image
preview which retains more perceptual features such that users can inspect features of interest by viewing the preview image
only and without zooming in. This technology has two components, structure enhancement and perceptual feature visualization.
Structure enhancement enhances the image structure while suppressing subtle details using a gradient modulation method, thus
making the succedent perceptual features more apparent. For perceptual feature visualization, features of interest detected
in the picture is visualized on the structure enhanced preview image. We demonstrate with two examples of most commonly used image quality features, image blur and noise. The effectiveness of the proposed method is validated
by experimental results. 相似文献
29.
个性化、高性能的树形菜单有着广泛的应用。在分析.NET框架的TreeView控件的基础上,总结了基于.NET平台实现个性化树形菜单的基本方法,给出了优化树形菜单数据处理性能的基本策略。 相似文献
30.
蝶类昆虫识别算法的研究与分析 总被引:1,自引:0,他引:1
提出利用边缘检测及角点提取来识别蝶类昆虫的方法.通过用四种边缘检测算子对鳞翅目蝴蝶进行边缘检测并作比较分析,从中找出鳞翅目昆虫边缘检测的最佳边缘检测算子,然后对边缘检测后的图像进行了角点提取特征信息,通过实验能够得到蝶类图像的特征,为下一步蝶类识别奠定了基础. 相似文献