全文获取类型
收费全文 | 70929篇 |
免费 | 6387篇 |
国内免费 | 3807篇 |
专业分类
电工技术 | 5279篇 |
技术理论 | 4篇 |
综合类 | 5265篇 |
化学工业 | 10007篇 |
金属工艺 | 4565篇 |
机械仪表 | 5166篇 |
建筑科学 | 5854篇 |
矿业工程 | 2431篇 |
能源动力 | 2045篇 |
轻工业 | 3986篇 |
水利工程 | 1624篇 |
石油天然气 | 4070篇 |
武器工业 | 765篇 |
无线电 | 7845篇 |
一般工业技术 | 7467篇 |
冶金工业 | 3446篇 |
原子能技术 | 871篇 |
自动化技术 | 10433篇 |
出版年
2024年 | 260篇 |
2023年 | 1015篇 |
2022年 | 1937篇 |
2021年 | 2770篇 |
2020年 | 2158篇 |
2019年 | 1643篇 |
2018年 | 2015篇 |
2017年 | 2141篇 |
2016年 | 1977篇 |
2015年 | 2835篇 |
2014年 | 3755篇 |
2013年 | 4436篇 |
2012年 | 5168篇 |
2011年 | 5377篇 |
2010年 | 4938篇 |
2009年 | 4705篇 |
2008年 | 4701篇 |
2007年 | 4615篇 |
2006年 | 4432篇 |
2005年 | 3776篇 |
2004年 | 2654篇 |
2003年 | 2129篇 |
2002年 | 1921篇 |
2001年 | 1611篇 |
2000年 | 1485篇 |
1999年 | 1370篇 |
1998年 | 1038篇 |
1997年 | 890篇 |
1996年 | 797篇 |
1995年 | 604篇 |
1994年 | 491篇 |
1993年 | 341篇 |
1992年 | 276篇 |
1991年 | 202篇 |
1990年 | 157篇 |
1989年 | 140篇 |
1988年 | 100篇 |
1987年 | 65篇 |
1986年 | 59篇 |
1985年 | 28篇 |
1984年 | 29篇 |
1983年 | 20篇 |
1982年 | 21篇 |
1981年 | 13篇 |
1980年 | 14篇 |
1979年 | 7篇 |
1966年 | 1篇 |
1959年 | 2篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
内容导读目前,针对潜在6G关键技术的场景与需求研究成为学术界的热点。面向未来更多类型终端的智能互联与新兴服务的需求,人工智能应用于无线通信物理层的信道估计、编译码及接收机设计,解决基于大数据的网络自主优化,基于泛在无线感知和边缘侧的强大算力构成的多接入边缘计算,已成为6G无线技术发展的重要趋势。在未来智能车联网、物联网、有人/无人交互、全息通信等场景下,面向未来的智能通信计算融合需求,存在许多拟待解决的关键科学问题。 相似文献
2.
3.
4.
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.
三元复合驱油体系中驱油剂的协同效应,会使油水间的界面张力大幅度下降,原油采收率大幅度提高;但三元复合驱油体系的色谱分离现象也会破坏其协同效应和完整性,揭示色谱分离现象及其影响因素对于改善三元复合驱油效果具有十分重要意义。以油藏工程和分析化学理论为指导,以化学分析和物理模拟为技术途径,并以大庆喇嘛甸油田典型区块地质特征和流体性质为研究对象,开展强碱三元复合驱色谱分离现象及其影响因素研究。结果表明,采用前置高浓度聚合物段塞后,可以有效扩大波及体积,但表面活性剂与碱和聚合物之间无因次等浓距增加,色谱分离现象加剧。大庆油区喇嘛甸油田不同区块油水性质差异对色谱分离现象存在影响,原因在于部分重烷基苯石油磺酸进入油相,影响水相中浓度检测值。强碱三元复合驱油体系中表面活性剂与碱和聚合物之间色谱分离程度比较严重,碱与聚合物之间较弱。 相似文献
8.
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
9.
Basins with various mineral resources coexisting and enriching often occupy an important strategic position. The exploration of various mineral resources is repetitive at present due to unshared data and imperfect management mechanism. This situation greatly increases the cost of energy exploitation in the country. Traditional data-sharing mode has several disadvantages, such as high cost, difficulty in confirming the right of data, and lack of incentive mechanism, which make achieving real data sharing difficult. In this paper, we propose a data-sharing mechanism based on blockchain and provide implementation suggestions and technical key points. Compared with traditional data-sharing methods, the proposed data-sharing mechanism can realize data sharing, ensure data quality, and protect intellectual property. Moreover, key points in the construction are stated in the case study section to verify the feasibility of the data-sharing system based on blockchain proposed in this paper. 相似文献
10.
Weigang Liang Beibei Wang Guofeng Shen Suzhen Cao Bertrand Mcswain Ning Qin Liyun Zhao Dongmei Yu Jicheng Gong Shanshan Zhao Yawei Zhang Xiaoli Duan 《Indoor air》2020,30(2):264-274
Stunting adversely affects physical and mental outcomes of children. It has not been examined whether household air pollution from solid fuel combustion is a risk factor for stunting in children. In a total of 41,439 children aged 6-17 across China, height was measured using a unified protocol. Multivariable linear regression models and logistic regression models were used to assess the associations of solid fuel use for cooking/heating with stunting in children. Adjusted for covariates, cooking/heating with solid fuel was significantly associated with a lower z-score for height for age and sex (β = −0.21 [−0.32 to −0.09] and −0.17 [−0.31 to −0.03], respectively) and an increased risk of stunting with an estimated ORs of 1.34 [1.07~1.68] and 1.37 [1.02~1.83], respectively. The risk of stunting associated with solid fuel use was statistically significant in high-age children. And the effect was greater on girls than on boys, though the difference was not statistically significant. Our study suggested that Chinese children living in households using solid fuel had a significantly higher risk of stunting than those living in households using cleaner fuel. 相似文献