全文获取类型
收费全文 | 44229篇 |
免费 | 9293篇 |
国内免费 | 6563篇 |
专业分类
电工技术 | 2635篇 |
综合类 | 5534篇 |
化学工业 | 1072篇 |
金属工艺 | 862篇 |
机械仪表 | 3922篇 |
建筑科学 | 1401篇 |
矿业工程 | 648篇 |
能源动力 | 452篇 |
轻工业 | 1128篇 |
水利工程 | 469篇 |
石油天然气 | 1178篇 |
武器工业 | 812篇 |
无线电 | 11776篇 |
一般工业技术 | 3958篇 |
冶金工业 | 575篇 |
原子能技术 | 391篇 |
自动化技术 | 23272篇 |
出版年
2024年 | 388篇 |
2023年 | 964篇 |
2022年 | 1620篇 |
2021年 | 1944篇 |
2020年 | 1915篇 |
2019年 | 1560篇 |
2018年 | 1442篇 |
2017年 | 1849篇 |
2016年 | 2005篇 |
2015年 | 2409篇 |
2014年 | 3180篇 |
2013年 | 2958篇 |
2012年 | 3876篇 |
2011年 | 3917篇 |
2010年 | 3334篇 |
2009年 | 3268篇 |
2008年 | 3454篇 |
2007年 | 3672篇 |
2006年 | 3009篇 |
2005年 | 2629篇 |
2004年 | 2078篇 |
2003年 | 1689篇 |
2002年 | 1334篇 |
2001年 | 1043篇 |
2000年 | 805篇 |
1999年 | 642篇 |
1998年 | 528篇 |
1997年 | 476篇 |
1996年 | 373篇 |
1995年 | 308篇 |
1994年 | 250篇 |
1993年 | 212篇 |
1992年 | 168篇 |
1991年 | 135篇 |
1990年 | 129篇 |
1989年 | 93篇 |
1988年 | 80篇 |
1987年 | 45篇 |
1986年 | 50篇 |
1985年 | 55篇 |
1984年 | 43篇 |
1983年 | 37篇 |
1982年 | 24篇 |
1981年 | 24篇 |
1980年 | 10篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1973年 | 5篇 |
1959年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
陈明志 《数字社区&智能家居》2006,1(12):159-160
本文对数字图像中几种具有代表性的边缘检测算子进行了理论分析,并通过VC编程实验,对各种算法进行实现,通过比较得出了各自的优缺点和适用范围。 相似文献
102.
Robert L. Stevenson Susan M. Schweizer 《Journal of Mathematical Imaging and Vision》1992,2(2-3):137-154
This paper introduces a new nonlinear filtering structure for filtering image data that have been corrupted by both impulsive and nonimpulsive additive noise. Like other nonlinear filters, the proposed filtering structure uses order-statistic operations to remove the effects of the impulsive noise. Unlike other filters, however, nonimpulsive noise is smoothed by using a maximum a posteriori estimation criterion. The prior model for the image is a novel Markov random-field model that models image edges so that they are accurately estimated while additive Gaussian noise is smoothed. The Markov random-field-based prior is chosen such that the filter has desirable analytical and computational properties. The estimate of the signal value is obtained at the unique minimum of the a posteriori log likelihood function. This function is convex so that the output of the filter can be easily computed by using either digital or analog computational methods. The effects of the various parameters of the model will be discussed, and the choice of the predetection order statistic filter will also be examined. Example outputs under various noise conditions will be given. 相似文献
103.
Yvon Maday Frédéric Magoulès 《Computer Methods in Applied Mechanics and Engineering》2007,196(8):1541-1553
In this paper an original variant of the Schwarz domain decomposition method is introduced for heterogeneous media. This method uses new optimized interface conditions specially designed to take into account the heterogeneity between the sub-domains on each sides of the interfaces. Numerical experiments illustrate the dependency of the proposed method with respect to several parameters, and confirm the robustness and efficiency of this method based on such optimized interface conditions. Several mesh partitions taking into account multiple cross points are considered in these experiments. 相似文献
104.
对现行的森林火情监测方法进行了分析比较。根据实际存在的难题,提出了料为产用的实施方案及应采取的技术措施,进行了实地试验,取得较好的效果。 相似文献
105.
介绍了X-射线荧光增量法同时测定硅铁合金中的Ca、Ba,探讨了基体效应校正、扩展曲线的应用范围,方法准确度和精度高。 相似文献
106.
In this paper we present a new radiosity algorithm, based on the notion of a well distributed ray set (WDRS). A WDRS is a set of rays, connecting mutually visible points and patches, that forms an approximate representation of the radiosity operator and the radiosity distribution. We propose an algorithm that constructs an optimal WDRS for a given accuracy and mesh. The construction is based on discrete importance sampling as in previously proposed stochastic radiosity algorithms, and on quasi Monte Carlo sampling. Quasi Monte Carlo sampling leads to faster convergence rates and the fact that the sampling is deterministic makes it possible to represent the well distributed ray set very efficiently in computer memory. Like previously proposed stochastic radiosity algorithms, the new algorithm is well suited for computing the radiance distribution in very complex diffuse scenes, when it is not feasible to explicitly compute and store form factors as in classical radiosity algorithms. Experiments show that the new algorithm is often more efficient than previously proposed Monte Carlo radiosity algorithms by half an order of magnitude and more. 相似文献
107.
Speed-up fractal image compression with a fuzzy classifier 总被引:4,自引:0,他引:4
This paper presents a fractal image compression scheme incorporated with a fuzzy classifier that is optimized by a genetic algorithm. The fractal image compression scheme requires to find matching range blocks to domain blocks from all the possible division of an image into subblocks. With suitable classification of the subblocks by a fuzzy classifier we can reduce the search time for this matching process so as to speedup the encoding process in the scheme. Implementation results show that by introducing three image classes and using fuzzy classifier optimized by a genetic algorithm the encoding process can be speedup by about 40% of an unclassified encoding system. 相似文献
108.
改善高平均功率固体激光器光束质量的研究 总被引:5,自引:0,他引:5
本文首先概述了内含热透镜的激光谐振腔的分析方法,提出影响高平均功率固体激光器光束质量的主要因素是激光介质的热效应,尤其是非对称的热透镜象差。因此,改善光束质量的途径是补偿或修正透镜象差,使光束质量达到非相干多模振荡的理论值。 相似文献
109.
110.
地层微电阻率成像测井在中原油田的应用 总被引:2,自引:0,他引:2
介绍地层微电阻率测井(FMI)技术以及它在地质构造解释、沉积学解释、裂缝识别、地层分析等方面独特的枝术优势,并详细介绍了FMI在中原油田濮深X井的实际应用,进行了应用效果分析,指出成像测井是未来油田油气勘探开发的重要技术手段。 相似文献