首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   87352篇
  免费   7758篇
  国内免费   3853篇
电工技术   5705篇
技术理论   4篇
综合类   5890篇
化学工业   14270篇
金属工艺   5026篇
机械仪表   5769篇
建筑科学   6973篇
矿业工程   2730篇
能源动力   2500篇
轻工业   5977篇
水利工程   1590篇
石油天然气   5444篇
武器工业   790篇
无线电   9969篇
一般工业技术   10630篇
冶金工业   3807篇
原子能技术   975篇
自动化技术   10914篇
  2024年   157篇
  2023年   1547篇
  2022年   2501篇
  2021年   3638篇
  2020年   2992篇
  2019年   2417篇
  2018年   2717篇
  2017年   2995篇
  2016年   2544篇
  2015年   3568篇
  2014年   4581篇
  2013年   5100篇
  2012年   5579篇
  2011年   6107篇
  2010年   5286篇
  2009年   5056篇
  2008年   4959篇
  2007年   4500篇
  2006年   4682篇
  2005年   3864篇
  2004年   2694篇
  2003年   2494篇
  2002年   2402篇
  2001年   2083篇
  2000年   1985篇
  1999年   2267篇
  1998年   1879篇
  1997年   1624篇
  1996年   1440篇
  1995年   1237篇
  1994年   971篇
  1993年   718篇
  1992年   632篇
  1991年   403篇
  1990年   334篇
  1989年   276篇
  1988年   196篇
  1987年   125篇
  1986年   90篇
  1985年   71篇
  1984年   50篇
  1983年   44篇
  1982年   52篇
  1981年   23篇
  1980年   25篇
  1979年   12篇
  1978年   7篇
  1977年   7篇
  1951年   5篇
  1940年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Wen  Pushan  He  Rui  Li  Xiang-Dan  Lee  Myong-Hoon 《Journal of Materials Science》2022,57(1):755-765
Journal of Materials Science - Three polyimides (PIs) were prepared from a diamine containing biphenyl ester group as a side chain and a corresponding dianhydride chosen from...  相似文献   
2.

Cr doped ZnAl2O4 spinel samples were prepared by the traditional solid state reaction and co-precipitation synthetic route, and the results suggest that the co-precipitation method has some superiority in contrast to the solid state reaction method. XRD, FT-IR, and XPS spectra confirmed that the well-crystallized spinel cubic phase of ZnAl2O4: Cr3+ samples were successfully formed. The morphology of the samples was investigated by FE-SEM and FE-TEM, and the results show that the samples by the co-precipitation route can generate a smaller size of particles compared to the solid state reaction. Photoluminescence excitation spectra monitored at 686 nm are comprised of two broad excitation bands near 530 nm and 395 nm, and the emission spectra show emissions ranging from 640 to 780 nm, due to the 2E?→?4A2 spin-forbidden transition of Cr3+ ions in spinel lattices. The optimized concentration monitored at 686 nm is 1%, while at 693 nm is 3.5%. Compared with the samples by solid state reaction method, the samples by co-precipitation method show preferable luminescent properties, such as the higher photoluminescence intensity and higher quantum efficiency. Several phosphor-converted LEDs were to investigate the applicability of the prepared samples. The results confirm that the phosphor has potential applications in plant growth and supplementing the red region in white-LEDs and the phosphors prepared by co-precipitation are more suitable to be used in phosphor-converted LED devices due to their preferable luminescent properties.

  相似文献   
3.
4.
5.
Song  Yupeng  He  Fazhi  Liu  Yanan 《Multimedia Tools and Applications》2022,81(10):13961-13978
Multimedia Tools and Applications - Tree species classification is a necessary and challenging task for both multimedia technique and forestry engineering. Continuous developments in multimedia and...  相似文献   
6.
Qin  Yuancheng  Yao  Yingbiao  Feng  Wei  Li  Pei  Xu  Xin 《Wireless Networks》2022,28(8):3337-3347
Wireless Networks - With the dynamic voltage scaling (DVS) technology, the terminal node (TN) can dynamically adjust its computational speed, thus providing a new way to save energy during task...  相似文献   
7.
The effects of cellulose microfibres (CMFs, Average size: 100 ± 5 μm) and cellulose nanofibres (CNFs, Average size: 60 ± 3 nm) on the properties of myofibrillar protein (MP) gels from duck breast meat were studied. The results demonstrated that CMFs and CNFs were mostly connected to MP by non-covalent bonds, the diffusion and cross-linking of MP molecules was promoted, and a denser and more complete gel network was formed. With the increases of CMFs and CNFs concentration (0–10%), the hardness was increased by 13.15% and 19.78% for CMFs10% and CNFs10% gels, respectively, and the elasticity was increased by 40% and 80%, respectively. At the same concentration (0–10%), the increase in gel hardness, viscoelasticity and immobilised water content was greater in the CNFs-MP group than in the CMFs-MP group. The CNFs-MP group had a tighter gel network, and CNFs had a better potential to improve the gelation performance of MP.  相似文献   
8.
9.
盾构隧道施工物料无人运输有助于提升运输效率、降低运输成本、减少运输安全事故率。与公路汽车无人驾驶、港口车辆无人驾驶、轨道交通无人驾驶等逐步成熟的无人驾驶技术不同,在隧道场景下实施施工物料无人运输存在运输物料种类繁多、运输调度困难、地下定位信号拒止、狭窄车道频繁会车、行车路面工况复杂、地上地下联动响应慢等诸多挑战。从实现盾构隧道施工物料无人运输的关键问题分析入手,综述当前盾构隧道施工物料运输方式、运输需求、无人运输发展现状及存在的挑战,提出盾构隧道施工物料无人运输的五大关键技术:多种类物料智能货控能效管理技术,无人化垂直装卸门机控制技术,多传感器融合同步定位与地图构建技术,隧道复杂环境路径规划与自主避障技术,隧-地一体化联动响应的高可靠性无线通信技术。  相似文献   
10.
Zhang  Jiawei  Li  Chen  Rahaman  Md Mamunur  Yao  Yudong  Ma  Pingli  Zhang  Jinghua  Zhao  Xin  Jiang  Tao  Grzegorzek  Marcin 《Artificial Intelligence Review》2022,55(4):2875-2944

Microorganisms such as bacteria and fungi play essential roles in many application fields, like biotechnique, medical technique and industrial domain. Microorganism counting techniques are crucial in microorganism analysis, helping biologists and related researchers quantitatively analyze the microorganisms and calculate their characteristics, such as biomass concentration and biological activity. However, traditional microorganism manual counting methods, such as plate counting method, hemocytometry and turbidimetry, are time-consuming, subjective and need complex operations, which are difficult to be applied in large-scale applications. In order to improve this situation, image analysis is applied for microorganism counting since the 1980s, which consists of digital image processing, image segmentation, image classification and suchlike. Image analysis-based microorganism counting methods are efficient comparing with traditional plate counting methods. In this article, we have studied the development of microorganism counting methods using digital image analysis. Firstly, the microorganisms are grouped as bacteria and other microorganisms. Then, the related articles are summarized based on image segmentation methods. Each part of the article is reviewed by methodologies. Moreover, commonly used image processing methods for microorganism counting are summarized and analyzed to find common technological points. More than 144 papers are outlined in this article. In conclusion, this paper provides new ideas for the future development trend of microorganism counting, and provides systematic suggestions for implementing integrated microorganism counting systems in the future. Researchers in other fields can refer to the techniques analyzed in this paper.

  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号