全文获取类型
收费全文 | 13157篇 |
免费 | 2247篇 |
国内免费 | 1549篇 |
专业分类
电工技术 | 534篇 |
综合类 | 1538篇 |
化学工业 | 501篇 |
金属工艺 | 306篇 |
机械仪表 | 686篇 |
建筑科学 | 601篇 |
矿业工程 | 2847篇 |
能源动力 | 291篇 |
轻工业 | 662篇 |
水利工程 | 640篇 |
石油天然气 | 362篇 |
武器工业 | 107篇 |
无线电 | 1285篇 |
一般工业技术 | 690篇 |
冶金工业 | 398篇 |
原子能技术 | 95篇 |
自动化技术 | 5410篇 |
出版年
2024年 | 46篇 |
2023年 | 156篇 |
2022年 | 432篇 |
2021年 | 595篇 |
2020年 | 661篇 |
2019年 | 425篇 |
2018年 | 381篇 |
2017年 | 400篇 |
2016年 | 488篇 |
2015年 | 631篇 |
2014年 | 970篇 |
2013年 | 839篇 |
2012年 | 1289篇 |
2011年 | 1255篇 |
2010年 | 957篇 |
2009年 | 926篇 |
2008年 | 1042篇 |
2007年 | 1069篇 |
2006年 | 863篇 |
2005年 | 743篇 |
2004年 | 569篇 |
2003年 | 453篇 |
2002年 | 370篇 |
2001年 | 302篇 |
2000年 | 234篇 |
1999年 | 199篇 |
1998年 | 129篇 |
1997年 | 114篇 |
1996年 | 99篇 |
1995年 | 64篇 |
1994年 | 60篇 |
1993年 | 39篇 |
1992年 | 33篇 |
1991年 | 30篇 |
1990年 | 22篇 |
1989年 | 18篇 |
1988年 | 11篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1979年 | 2篇 |
1975年 | 2篇 |
1961年 | 1篇 |
1959年 | 1篇 |
1955年 | 1篇 |
1954年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
目的 为了解决目前三维数据隐藏算法不能兼顾无失真和盲提取的问题,提出一种新的完全无失真的三维网格模型数据隐藏盲算法。方法 首先使用混沌逻辑映射选择嵌入与提取模式,保证数据的安全性。然后利用面元素重排,完全不会造成三维模型失真的性质,通过不同嵌入模式规则对三角面元素进行重排,以嵌入秘密数据。接收端则可根据相应的提取模式规则提取秘密数据。结果 仿真结果与分析表明,该算法不会对三维模型造成任何失真,嵌入容量为每顶点2比特,且能抵抗仿射变换攻击、噪声攻击和平滑攻击等。结论 这种三维数据隐藏盲算法无失真,容量大、安全性高、鲁棒性强,适用于三维载体不容修改的情形,如军事、医学、秘密通信和版权保护等。 相似文献
2.
3.
4.
High-efficiency filtration in residential forced-air heating, ventilation, and air conditioning (HVAC) systems protects equipment and can reduce exposure to particulate matter. Laboratory tests provide a measure of the nominal efficiency, but they may not accurately reflect the in situ efficiency of the filters because of variations in system conditions and changes in filter performance over time. The primary focus of this paper is to evaluate the effective filtration efficiency, which is inclusive of any loading and system impacts, in 21 occupied residential homes through in-duct concentration measurements. We considered the role of filter media by testing both electret and non-electret media, as well as the role of loading by considering new and used filters. The results show that filters with higher nominal efficiency generally had higher effective filtration efficiency in the same home. In terms of performance change, there is no significant difference in efficiency between initial and 3-month non-electret filters, but the efficiency of electret filters generally decreased over time. However, both nominal efficiency and performance change were vastly overshadowed by the wide variety in loading and system conditions across homes, making it hard to predict filter efficiency in a given home without in situ measurements. 相似文献
5.
Zhijiang Li Yingping Zheng Liqin Cao Lei Jiao Yanfei Zhong Caiyi Zhang 《Color research and application》2020,45(4):656-670
Image color clustering is a basic technique in image processing and computer vision, which is often applied in image segmentation, color transfer, contrast enhancement, object detection, skin color capture, and so forth. Various clustering algorithms have been employed for image color clustering in recent years. However, most of the algorithms require a large amount of memory or a predetermined number of clusters. In addition, some of the existing algorithms are sensitive to the parameter configurations. In order to tackle the above problems, we propose an image color clustering method named Student's t-based density peaks clustering with superpixel segmentation (tDPCSS), which can automatically obtain clustering results, without requiring a large amount of memory, and is not dependent on the parameters of the algorithm or the number of clusters. In tDPCSS, superpixels are obtained based on automatic and constrained simple non-iterative clustering, to automatically decrease the image data volume. A Student's t kernel function and a cluster center selection method are adopted to eliminate the dependence of the density peak clustering on parameters and the number of clusters, respectively. The experiments undertaken in this study confirmed that the proposed approach outperforms k-means, fuzzy c-means, mean-shift clustering, and density peak clustering with superpixel segmentation in the accuracy of the cluster centers and the validity of the clustering results. 相似文献
6.
7.
In this paper, we first re-examine the previous protocol of controlled quantum secure direct communication of Zhang et al.’s scheme, which was found insecure under two kinds of attacks, fake entangled particles attack and disentanglement attack. Then, by changing the party of the preparation of cluster states and using unitary operations, we present an improved protocol which can avoid these two kinds of attacks. Moreover, the protocol is proposed using the three-qubit partially entangled set of states. It is more efficient by only using three particles rather than four or even more to transmit one bit secret information. Given our using state is much easier to prepare for multiqubit states and our protocol needs less measurement resource, it makes this protocol more convenient from an applied point of view. 相似文献
8.
9.
10.
为解决21000工作面采空区及顶板涌水问题,根据工作面出水点的不同情况,采取了集水器导水、老塘设挡水堰截水、挖排水沟疏水等多项治水措施,经统计排水量达33~42m3/h,有效控制了水情,确保了工作面正常生产。 相似文献