全文获取类型
收费全文 | 82872篇 |
免费 | 7948篇 |
国内免费 | 4692篇 |
专业分类
电工技术 | 5571篇 |
技术理论 | 4篇 |
综合类 | 6334篇 |
化学工业 | 13611篇 |
金属工艺 | 4623篇 |
机械仪表 | 4855篇 |
建筑科学 | 6990篇 |
矿业工程 | 2460篇 |
能源动力 | 2457篇 |
轻工业 | 6439篇 |
水利工程 | 1609篇 |
石油天然气 | 4156篇 |
武器工业 | 630篇 |
无线电 | 9854篇 |
一般工业技术 | 9688篇 |
冶金工业 | 3484篇 |
原子能技术 | 1108篇 |
自动化技术 | 11639篇 |
出版年
2024年 | 445篇 |
2023年 | 1588篇 |
2022年 | 2873篇 |
2021年 | 3719篇 |
2020年 | 2901篇 |
2019年 | 2584篇 |
2018年 | 2740篇 |
2017年 | 2995篇 |
2016年 | 2486篇 |
2015年 | 3486篇 |
2014年 | 4239篇 |
2013年 | 4824篇 |
2012年 | 5140篇 |
2011年 | 5338篇 |
2010年 | 4822篇 |
2009年 | 4590篇 |
2008年 | 4506篇 |
2007年 | 4122篇 |
2006年 | 4132篇 |
2005年 | 3368篇 |
2004年 | 2677篇 |
2003年 | 3213篇 |
2002年 | 4029篇 |
2001年 | 3393篇 |
2000年 | 2161篇 |
1999年 | 1907篇 |
1998年 | 1291篇 |
1997年 | 1130篇 |
1996年 | 1041篇 |
1995年 | 879篇 |
1994年 | 683篇 |
1993年 | 494篇 |
1992年 | 439篇 |
1991年 | 272篇 |
1990年 | 236篇 |
1989年 | 196篇 |
1988年 | 152篇 |
1987年 | 88篇 |
1986年 | 67篇 |
1985年 | 66篇 |
1984年 | 41篇 |
1983年 | 34篇 |
1982年 | 33篇 |
1981年 | 16篇 |
1980年 | 24篇 |
1979年 | 12篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1959年 | 5篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
在分析了数字版权研究现状和功能框架的基础上,设计了基于多重数字水印和密码的版权管理模型;该模型采用数字内容和许可证各自单独封装、独立分发的方式,使得只有购买了许可证的特定用户才能使用数字内容,实现了水印作品的许可交易;另外,内容服务器采用的对数字作品加载两次水印,对数字内容部分签名加密,未加密部分签名的方案,在有效保证数字内容安全传输的基础上又减少了计算量和存储量;分析表明该模型有显著的优点和很好的安全性。 相似文献
92.
Jian-You Guo Miao Yu Jing Wang Bao-Mei Yao Peng Jiao 《Computer Physics Communications》2010,181(3):550-556
We develop the complex scaling method within the relativistic framework by expanding the Dirac spinors in the complete set of eigensolutions of a harmonic oscillator potential, and present the theoretical formalism of describing the discrete bound and resonant states on the same footing. Based on a well established and frequently used model, we demonstrate the utility and applicability of the extended method and examine the stability of the results with respect to the variations of the parameters of the model. Satisfactory agreements are found for all the calculated results in comparison with some other calculations in references. Especially, the present calculation in the nonrelativistic limit gives a consistent result with that in the nonrelativistic calculation. 相似文献
93.
针对燃气行业人工抄表费时费力等问题,提出一种基于GPRS和无线多跳网络技术的燃气无线抄表系统,在分析传统抄表系统的结构以及传输方式优缺点的基础上介绍了系统的总体结构、工作原理以及各部分组成和功能。采用计算机网络和数据库等技术,使得该系统具有功能强大、使用方便、可扩展性好等特点,可实现对整个燃气输配系统的监控,有效提高燃气公司的管理水平和服务效率。 相似文献
94.
Different from reversible image data hiding, most reversible video data hiding schemes have the particular problem that the distortion due to hidden data will spread and accumulate. In this paper, the problem of distortion drift caused by reversible data hiding in compressed video is analyzed, and a lossless drift compensation scheme is proposed to restrain the distortion for the first time. In order to ensure the reversibility, drift compensation signals are merged in the quantized DCT (Discrete Cosine Transform) coefficients of P-frames and the corresponding recovery mechanism is presented as well. Experimental results demonstrate that the proposed lossless drift compensation scheme significantly improves the video quality, and the original compressed video can be recovered exactly after the hidden data and compensation signals are removed. In addition, the proposed scheme does not depend on specific reversible data hiding method. 相似文献
95.
<正>毋庸置疑,"可靠性"一直是评价电子产品性能的关键词之一,尤其在军工、航天等领域,产品的可靠性更是具有举足轻重的地位。一个细小器件的故障引发系统重大事故的案例屡见不鲜。随着人们对可靠性的重要性认识的不断提高,业内对可靠性理论及可靠性设计的研究也不断深入。12月2日,由中国电子 相似文献
96.
Yuan X He X Guo H Guo P Kendall W Huang J Zhang Y 《IEEE transactions on visualization and computer graphics》2010,16(6):1413-1420
Over the past few years, large human populations around the world have been affected by an increase in significant seismic activities. For both conducting basic scientific research and for setting critical government policies, it is crucial to be able to explore and understand seismic and geographical information obtained through all scientific instruments. In this work, we present a visual analytics system that enables explorative visualization of seismic data together with satellite-based observational data, and introduce a suite of visual analytical tools. Seismic and satellite data are integrated temporally and spatially. Users can select temporal ;and spatial ranges to zoom in on specific seismic events, as well as to inspect changes both during and after the events. Tools for designing high dimensional transfer functions have been developed to enable efficient and intuitive comprehension of the multi-modal data. Spread-sheet style comparisons are used for data drill-down as well as presentation. Comparisons between distinct seismic events are also provided for characterizing event-wise differences. Our system has been designed for scalability in terms of data size, complexity (i.e. number of modalities), and varying form factors of display environments. 相似文献
97.
Segmenting center of interests (COIs) from pictures is an important but highly challenging problem for researchers in computer vision and image processing. The capability of understanding the meanings of pictures by computers can lead to breakthroughs in a wide range of applications including Web image search and online picture-sharing communities. In this paper, a two-level strategy is presented, which consists of a rough segmentation stage and a fine segmentation stage. In the first level, a picture is partitioned into four regions by using a block clustering method based on color and texture features, and the COI within the picture is distinguished from the background according to the principles of photographic composition. This stage aims to determine the approximate region of the target. In the second level, a novel active contour model is established based on shape information and vector method, where the image energy is defined by a hue gradient and the external energy is generated from either a triangular inner force or a supplementary force. This stage tries to extract the boundary of the target accurately. Experimental results on photos downloaded from the Internet show the feasibility and effectiveness of the proposed method. 相似文献
98.
Research on fine tuning stabilization properties has received attention for more than a decade. This paper presents probabilistic algorithms for fault containment. We demonstrate two exercises in fault containment in a weakly stabilizing system, which expedite recovery from single failures, and confine the effect of any single fault to the constant-distance neighborhood of the faulty process. The most significant aspect of the algorithms is that the fault gap, defined as the smallest interval after which the system is ready to handle the next single fault with the same efficiency, is independent of the network size. We argue that a small fault gap increases the availability of the fault-free system. 相似文献
99.
100.
一种基于组策略的过滤式特征选择算法 总被引:1,自引:0,他引:1
MRMR算法具有快速、高效等优势,在处理高维数据方面较为流行。基于此,提出一种基于组策略的MRMR改进算法(MRMRE),该算法不仅考虑单个特征属性的相关性与冗余性,同时针对特征组间的相互关系进行研究。算法以MRMR算法为框架,以CCA作为度量基准,选择SVMs作为基分类器,使其特征选择效果提升。在UCI机器学习数据库中图像与基因序列数据集上的大量实验表明:与MRMR算法相比,所提出的算法其特征选择结果具有更高的结果稳定性与分类精度。 相似文献