全文获取类型
收费全文 | 33780篇 |
免费 | 3385篇 |
国内免费 | 2082篇 |
专业分类
电工技术 | 2847篇 |
技术理论 | 2篇 |
综合类 | 2878篇 |
化学工业 | 4195篇 |
金属工艺 | 966篇 |
机械仪表 | 1864篇 |
建筑科学 | 3069篇 |
矿业工程 | 1389篇 |
能源动力 | 3966篇 |
轻工业 | 1408篇 |
水利工程 | 788篇 |
石油天然气 | 2008篇 |
武器工业 | 327篇 |
无线电 | 5183篇 |
一般工业技术 | 2895篇 |
冶金工业 | 1373篇 |
原子能技术 | 616篇 |
自动化技术 | 3473篇 |
出版年
2024年 | 146篇 |
2023年 | 544篇 |
2022年 | 948篇 |
2021年 | 1163篇 |
2020年 | 1275篇 |
2019年 | 1100篇 |
2018年 | 1039篇 |
2017年 | 1280篇 |
2016年 | 1434篇 |
2015年 | 1508篇 |
2014年 | 2241篇 |
2013年 | 2286篇 |
2012年 | 2512篇 |
2011年 | 2682篇 |
2010年 | 2046篇 |
2009年 | 2061篇 |
2008年 | 1902篇 |
2007年 | 2030篇 |
2006年 | 1911篇 |
2005年 | 1470篇 |
2004年 | 1224篇 |
2003年 | 1074篇 |
2002年 | 883篇 |
2001年 | 757篇 |
2000年 | 659篇 |
1999年 | 551篇 |
1998年 | 402篇 |
1997年 | 364篇 |
1996年 | 354篇 |
1995年 | 270篇 |
1994年 | 243篇 |
1993年 | 167篇 |
1992年 | 116篇 |
1991年 | 139篇 |
1990年 | 92篇 |
1989年 | 75篇 |
1988年 | 49篇 |
1987年 | 47篇 |
1986年 | 40篇 |
1985年 | 31篇 |
1984年 | 26篇 |
1983年 | 19篇 |
1982年 | 24篇 |
1981年 | 26篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1976年 | 3篇 |
1959年 | 3篇 |
1955年 | 3篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
81.
Multifocus image fusion is the process of obtaining a single image from multiple partially focused images such that the newly formed image consists of the well-defined information extracted from each source image. This paper proposes the use of saliency of the source images based on Mutual Spectral Residual. Spectral Residual brings out the unique/salient features of an image in frequency domain. The idea of proposed mutual spectral residual is to emphasize the relative unique features of a source image with respect to the other source images. The relative unique features are utilized to form saliency maps for each source image. These saliency maps can clearly indicate the focused and defocused parts of an image. Based on the saliency maps obtained, the image fusion takes place in spatial domain. Visual inspection and quantitative evaluation of the fused images obtained by the proposed method, using different evaluation metrics, demonstrate its effectiveness over several existing image fusion methods. 相似文献
82.
Kathleen Menzies Duncan Birrell Gordon Dunsire 《New Review of Information Networking》2013,18(2):92-140
This article reports on the key findings and implications of the Joint Information Systems Committee (JISC)-funded Online Catalogue and Repository Interoperability Study (OCRIS), a 3-month project which investigated the interoperability of Online Public Access Catalogues (OPACs) and Institutional Repositories (IRs) within UK universities. A series of detailed recommendations enumerate some of the ways in which they might begin to develop and support an interoperable systems landscape to the benefit of all key stakeholders. The project combined quantitative and qualitative research methods including an online questionnaire distributed to staff within 85 universities, desk research, and two case studies conducted at the Universities of Cambridge and Glasgow. 相似文献
83.
直流变频电动执行机构主要是控制系统采用的控制器集成BLDC电机驱动,具有智能变频型电动执行器所有功能要求,配合直流无刷电机适用于各种类型的场合,作为工业控制的核心单元,被广泛应用在各行业工业控制单元。执行机构所用蜗杆传动用于交错轴间运动及动力。本论文根据在相同条件下讨论三种蜗杆传动设计和校核,来验证采用不同的加工方法。以达到提高其承载能力的目的[1][3]。 相似文献
84.
根据相关的调查显示,在传统观念和设计标准的影响下,网络机房存在各种各样的设计缺陷,其中的一些缺陷会导致网络机房内部空间形成热点、降低制冷容错能力、制冷效率和制冷量,从而提高运行成本。网络机房的制冷效率和运行成本的大幅提高成为制约发展的重要因素。文章从网络机房面临的实际问题出发,有针对性地分析了机房设计的典型错误,阐述了其原理和影响,并根据实践经验,介绍了一些简单可行的解决方案。 相似文献
85.
提出了一种基于谱直方图和支持向量机的人脸检测算法。首先使用梯度滤波器、LoG滤波器和LBP算子计算图像的谱直方图,然后使用支持向量机进行分类。经实验表明,算法可以克服光照、姿势、表情、眼镜等干扰,并允许有局部遮挡,具有较强的鲁棒性。 相似文献
86.
87.
This paper presents a systematic study of light interferences at single thin films. Based on Fresnel's law, we have derived generic expressions of reflectance and transmittance for film interference, as well as specific expressions for free thin films and films coated on transparent or opaque objects. By combining film interference and volume absorption, we have obtained the reflectances and transmittances of film‐coated thin objects such as ribbons. Illumination models for all interference cases of single thin films are presented, and they have been implemented and tested for various structures and materials. 相似文献
88.
Elif Derya Übeyli 《Expert Systems》2008,25(4):367-379
Abstract: In this study, Doppler signals recorded from the internal carotid artery (ICA) of 97 subjects were processed by personal computer using classical and model-based methods. Fast Fourier transform (classical method) and autoregressive (model-based method) methods were selected for processing the ICA Doppler signals. The parameters in the autoregressive method were found by using maximum likelihood estimation. The Doppler power spectra of the ICA Doppler signals were obtained by using these spectral analysis techniques. The variations in the shape of the Doppler spectra as a function of time were presented in the form of sonograms in order to obtain medical information. These Doppler spectra and sonograms were then used to compare the applied methods in terms of their frequency resolution and the effects in determination of stenosis and occlusion in the ICA. Reliable information on haemodynamic alterations in the ICA can be obtained by evaluation of these sonograms. 相似文献
89.
This paper presents the development of the planar bipedal robot ERNIE as well as numerical and experimental studies of the
influence of parallel knee joint compliance on the energetic efficiency of walking in ERNIE. ERNIE has 5 links—a torso, two
femurs and two tibias—and is configured to walk on a treadmill so that it can walk indefinitely in a confined space. Springs
can be attached across the knee joints in parallel with the knee actuators. The hybrid zero dynamics framework serves as the
basis for control of ERNIE’s walking. In the investigation of the effects of compliance on the energetic efficiency of walking,
four cases were studied: one without springs and three with springs of different stiffnesses and preloads. It was found that
for low-speed walking, the addition of soft springs may be used to increase energetic efficiency, while stiffer springs decrease
the energetic efficiency. For high-speed walking, the addition of either soft or stiff springs increases the energetic efficiency
of walking, while stiffer springs improve the energetic efficiency more than do softer springs.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users.
相似文献
R. A. BockbraderEmail: |
90.