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   7416篇
  免费   893篇
  国内免费   190篇
电工技术   242篇
技术理论   1篇
综合类   190篇
化学工业   1904篇
金属工艺   328篇
机械仪表   462篇
建筑科学   259篇
矿业工程   70篇
能源动力   386篇
轻工业   662篇
水利工程   81篇
石油天然气   213篇
武器工业   20篇
无线电   1108篇
一般工业技术   1363篇
冶金工业   254篇
原子能技术   91篇
自动化技术   865篇
  2024年   38篇
  2023年   159篇
  2022年   293篇
  2021年   402篇
  2020年   316篇
  2019年   281篇
  2018年   301篇
  2017年   324篇
  2016年   326篇
  2015年   303篇
  2014年   445篇
  2013年   522篇
  2012年   531篇
  2011年   554篇
  2010年   457篇
  2009年   414篇
  2008年   417篇
  2007年   270篇
  2006年   276篇
  2005年   271篇
  2004年   225篇
  2003年   203篇
  2002年   157篇
  2001年   137篇
  2000年   118篇
  1999年   157篇
  1998年   110篇
  1997年   82篇
  1996年   90篇
  1995年   57篇
  1994年   59篇
  1993年   31篇
  1992年   26篇
  1991年   30篇
  1990年   21篇
  1989年   22篇
  1988年   7篇
  1987年   10篇
  1986年   4篇
  1985年   6篇
  1984年   10篇
  1983年   8篇
  1982年   4篇
  1981年   5篇
  1980年   2篇
  1979年   4篇
  1978年   4篇
  1977年   3篇
  1973年   3篇
  1972年   2篇
排序方式: 共有8499条查询结果,搜索用时 15 毫秒
1.

LiFe2/3Mn1/3PO4/C composite was prepared by the rheological phase reaction using LiH2PO4, Li2CO3, FePO4, Mn(Ac)2·4H2O and ascorbic acid as starting materials. The crystal structure and morphology of as-synthesized sample were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The analysis of XRD results showed that the obtained sample was single-phase with orthorhombic olivine-type structure (Pnma space group). SEM micrographs revealed that the sample was aggregates, with an irregular morphology. The initial discharge capacity was 166.9, 149.1, 139.6, 112.8, 82.93 mAh g??1 at the rate of 0.1, 0.5, 1, 2, and 10 C, respectively. And when the rate was 0.1, 0.5, 1, 2, and 10 C, the capacity retention was 92.2%, 90%, 92.9%, 97.6%, 91.5% after 50, 100, 200, 200, 500 cycles, respectively.

  相似文献   
2.
Neural Processing Letters - Raman spectroscopy is often used for the composition determination and rapid classification of materials because it can reflect the molecular information of materials....  相似文献   
3.
4.
5.
为了响应"全员育人、全程育人、全方位育人"三全育人的重要举措,以及体现专业课程在立德树人方面的重要作用和对生物化工专业的认同,文中旨将专业知识与社会主义核心价值观有机的融合,润物细无声的对学生进行思政教育,积极探索微生物学实验中能够与思政元素相融合的切入点,一方面激发了学生的学习兴趣和自学潜能,提升了课堂教学效果和效率,另一方面达成了生物化工行业对高质量人才的需求.  相似文献   
6.
Intelligent Service Robotics - A robust control designed for multiple degrees-of-freedom (DOF) robot manipulators performing complex tasks requiring frequent physical interaction with unknown...  相似文献   
7.
8.
The electrochemical reduction of carbon dioxide (CO2) to hydrocarbons is a challenging task because of the issues in controlling the efficiency and selectivity of the products. Among the various transition metals, copper has attracted attention as it yields more reduced and C2 products even while using mononuclear copper center as catalysts. In addition, it is found that reversible formation of copper nanoparticle acts as the real catalytically active site for the conversion of CO2 to reduced products. Here, it is demonstrated that the dinuclear molecular copper complex immobilized over graphitized mesoporous carbon can act as catalysts for the conversion of CO2 to hydrocarbons (methane and ethylene) up to 60%. Interestingly, high selectivity toward C2 product (40% faradaic efficiency) is achieved by a molecular complex based hybrid material from CO2 in 0.1 m KCl. In addition, the role of local pH, porous structure, and carbon support in limiting the mass transport to achieve the highly reduced products is demonstrated. Although the spectroscopic analysis of the catalysts exhibits molecular nature of the complex after 2 h bulk electrolysis, morphological study reveals that the newly generated copper cluster is the real active site during the catalytic reactions.  相似文献   
9.
All-buried InP-InGaAsP ring resonators laterally coupled to bus waveguides are demonstrated. The buried configurations offer a lower built-in refractive index step along the resonator periphery, which affords enhanced optical coupling coefficients between the waveguides and reduced scattering losses caused by the resonator sidewall imperfections. Very low optical intensity attenuations of 0.4 cm/sup -1/ and coupling-limited quality factors of greater than 10/sup 5/ are observed from 200-/spl mu/m-radii ring resonators. The measured spectral linewidth is as narrow as 0.0145 nm.  相似文献   
10.
We have developed a new type of tunable band rejection filter, which provides high spectral-shaping flexibility in a wide tuning range. The filter consists of a long-period fiber grating (LPFG) with divided coil heaters. Each of the divided coil heaters is controlled individually to adjust a temperature distribution along the LPFG and to modify the spectral shape of the LPFG filter. The tunable band rejection filter is demonstrated to function properly when applied as an erbium-doped fiber amplifier gain-flattening filter.  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