全文获取类型
收费全文 | 101726篇 |
免费 | 11334篇 |
国内免费 | 6397篇 |
专业分类
电工技术 | 8071篇 |
技术理论 | 7篇 |
综合类 | 7909篇 |
化学工业 | 14863篇 |
金属工艺 | 5714篇 |
机械仪表 | 6980篇 |
建筑科学 | 9111篇 |
矿业工程 | 3372篇 |
能源动力 | 2976篇 |
轻工业 | 7749篇 |
水利工程 | 2321篇 |
石油天然气 | 4751篇 |
武器工业 | 1140篇 |
无线电 | 12956篇 |
一般工业技术 | 10700篇 |
冶金工业 | 3887篇 |
原子能技术 | 1412篇 |
自动化技术 | 15538篇 |
出版年
2024年 | 602篇 |
2023年 | 1950篇 |
2022年 | 3915篇 |
2021年 | 5452篇 |
2020年 | 4040篇 |
2019年 | 3085篇 |
2018年 | 3393篇 |
2017年 | 3816篇 |
2016年 | 3384篇 |
2015年 | 4909篇 |
2014年 | 6208篇 |
2013年 | 7116篇 |
2012年 | 8352篇 |
2011年 | 8657篇 |
2010年 | 7808篇 |
2009年 | 7239篇 |
2008年 | 6809篇 |
2007年 | 6139篇 |
2006年 | 5395篇 |
2005年 | 4399篇 |
2004年 | 2889篇 |
2003年 | 2144篇 |
2002年 | 1983篇 |
2001年 | 1631篇 |
2000年 | 1426篇 |
1999年 | 1374篇 |
1998年 | 907篇 |
1997年 | 835篇 |
1996年 | 787篇 |
1995年 | 643篇 |
1994年 | 522篇 |
1993年 | 352篇 |
1992年 | 262篇 |
1991年 | 209篇 |
1990年 | 146篇 |
1989年 | 129篇 |
1988年 | 111篇 |
1987年 | 71篇 |
1986年 | 58篇 |
1985年 | 33篇 |
1984年 | 24篇 |
1983年 | 17篇 |
1982年 | 22篇 |
1981年 | 19篇 |
1980年 | 31篇 |
1979年 | 25篇 |
1962年 | 42篇 |
1961年 | 39篇 |
1960年 | 16篇 |
1959年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
As a solid state joining process, ultrasonic spot welding has been proven to be a promising technique for joining copper alloys. However, challenges still remain in employing ultrasonic spot welding to join copper alloys. This article comprehensively reviews the current state of ultrasonic spot welding of copper alloys with a number of critical issues including materials flow, plastic deformation, temperature distribution, vibration, relative motion, vertical displacement, interface friction coefficient, online monitoring technique, coupled with the macrostructure and microstructure, the mechanical properties and electrical conductivity. In addition, the future trends in this field are provided. 相似文献
32.
33.
34.
35.
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
36.
分析了20号无缝钢管的室温和低温力学性能,结合显微组织观察、晶粒度统计和断口分析,发现低温低应力工况下服役后20号无缝钢管的力学性能完全符合冷库用液氨管道的使用要求。 相似文献
37.
为解决共享交通下的共乘用户群体发现效率低、准确率不高问题,依据R-树原理建立GeoOD-Tree索引,并在此基础上提出以最大化共乘率为目标的群体发现策略。首先,对原始时空轨迹数据进行特征提取与标定处理,挖掘有效出行起讫点(OD)轨迹;其次,针对用户起讫点轨迹的特征,建立GeoOD-Tree索引进行有效的存储管理;最后,给出以最大化共乘行程为目标的群体发现模型,并运用K最近邻(KNN)查询对搜索空间剪枝压缩,提高群体发现效率。采用西安市近12000辆出租车营运轨迹数据,选取动态时间规整(DTW)等典型算法与所提算法在查询效率与准确率上进行性能对比分析。与DTW算法相比,所提算法的准确率提高了10.12%,查询效率提高了约15倍。实验结果表明提出的群体发现策略能有效提高共乘用户群体发现的准确率和效率,可有效提升共乘出行方式的出行率。 相似文献
38.
Zehu Xie Na Peng Tingting Liu Xing Cheng Wuquan Ye Runtian Zheng Jundong Zhang Haoxiang Yu Jie Shu 《Ceramics International》2019,45(9):11812-11818
Here, LiY(WO4)2 nanotubes are prepared via a feasible electrospinning technique. This new anode material shows excellent electrochemical properties. The capacity loss of LiY(WO4)2 nanotubes is as low as 6.9% after 156 cycles, while bulk LiY(WO4)2 presents the capacity loss higher than 55.0%. Even after 600 long-life cycles, the capacity loss of the nanotubes is only 9%. It can be seen that the hollow structure with a rough surface and a porous morphology contributes to the improvement of electrochemical performance. Furthermore, online X-ray diffraction (XRD) method is firstly applied to understand the lithium ions insertion/extraction mechanism of LiY(WO4)2 nanotubes. It can be concluded that it is an asymmetrical two-phase reaction. A phase transformation from LiY(WO4)2 to Li3Y(WO4)2 can be obviously seen from the in situ XRD during discharge process. While Li2Y(WO4)2 appears as an intermediate phase with a reverse charge reaction. In addition, in situ XRD also demonstrates that LiY(WO4)2 nanotubes have surprised electrochemical reversibility. All the above results indicate that LiY(WO4)2 nanotubes can be expected to be anode candidate for rechargeable lithium ion batteries (LIBs). 相似文献
39.
Bo Wang Edison Huixiang Ang Yang Yang Yufei Zhang Hongbo Geng Minghui Ye Cheng Chao Li 《Advanced functional materials》2020,30(28)
Orthorhombic molybdenum trioxide (MoO3) is one of the most promising anode materials for sodium‐ion batteries because of its rich chemistry associated with multiple valence states and intriguing layered structure. However, MoO3 still suffers from the low rate capability and poor cycle induced by pulverization during de/sodiation. An ingenious two‐step synthesis strategy to fine tune the layer structure of MoO3 targeting stable and fast sodium ionic diffusion channels is reported here. By integrating partially reduction and organic molecule intercalation methodologies, the interlayer spacing of MoO3 is remarkably enlarged to 10.40 Å and the layer structural integration are reinforced by dimercapto groups of bismuththiol molecules. Comprehensive characterizations and density functional theory calculations prove that the intercalated bismuththiol (DMcT) molecules substantially enhanced electronic conductivity and effectively shield the electrostatic interaction between Na+ and the MoO3 host by conjugated double bond, resulting in improved Na+ insertion/extraction kinetics. Benefiting from these features, the newly devised layered MoO3 electrode achieves excellent long‐term cycling stability and outstanding rate performance. These achievements are of vital significance for the preparation of sodium‐ion battery anode materials with high‐rate capability and long cycling life using intercalation chemistry. 相似文献
40.