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   13302篇
  免费   1509篇
  国内免费   567篇
电工技术   940篇
技术理论   1篇
综合类   625篇
化学工业   2710篇
金属工艺   800篇
机械仪表   829篇
建筑科学   812篇
矿业工程   305篇
能源动力   475篇
轻工业   961篇
水利工程   255篇
石油天然气   637篇
武器工业   97篇
无线电   1759篇
一般工业技术   1896篇
冶金工业   493篇
原子能技术   164篇
自动化技术   1619篇
  2024年   67篇
  2023年   223篇
  2022年   416篇
  2021年   625篇
  2020年   485篇
  2019年   422篇
  2018年   452篇
  2017年   501篇
  2016年   503篇
  2015年   628篇
  2014年   752篇
  2013年   829篇
  2012年   973篇
  2011年   1019篇
  2010年   837篇
  2009年   785篇
  2008年   721篇
  2007年   589篇
  2006年   624篇
  2005年   546篇
  2004年   460篇
  2003年   425篇
  2002年   346篇
  2001年   306篇
  2000年   262篇
  1999年   316篇
  1998年   240篇
  1997年   214篇
  1996年   179篇
  1995年   146篇
  1994年   115篇
  1993年   59篇
  1992年   68篇
  1991年   60篇
  1990年   42篇
  1989年   37篇
  1988年   14篇
  1987年   22篇
  1986年   8篇
  1985年   6篇
  1984年   10篇
  1983年   8篇
  1982年   6篇
  1981年   5篇
  1979年   5篇
  1978年   4篇
  1977年   3篇
  1973年   3篇
  1959年   5篇
  1951年   2篇
排序方式: 共有10000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.
The effects of La2O3–Al2O3–SiO2 addition on the thermal conductivity, coefficient of thermal expansion (CTE), Young's modulus and cyclic thermal shock resistance of hot-pressed h-BN composite ceramics were investigated. The samples were heated to 1000 °C and then quenched to room temperature with 1–50 cycles, and the residual flexural strength was used to evaluate cyclic thermal shock resistance. h-BN composite ceramics containing 10 vol% La2O3–Al2O3 and 20 vol% SiO2 addition exhibited the highest flexural strength, thermal conductivity and relatively low CTE, which were beneficial to the excellent thermal shock resistance. In addition, the viscous amorphous phase of ternary La2O3–Al2O3–SiO2 system could accommodate and relax thermal stress contributing to the high thermal shock resistance. Therefore, the residual flexural strength still maintained the value of 234.3 MPa (86.9% of initial strength) after 50 cycles of thermal shock.  相似文献   
6.
Zu  Guoqing  Lu  Yukuan  Yan  Yi  Zhang  Xiaoming  Zhao  Jingwei  Du  Wei  Ran  Xu  Jiang  Zhengyi 《Metals and Materials International》2020,26(2):248-259
Metals and Materials International - The flow behaviour and microstructure characteristics of a ferritic stainless steel were investigated using plain strain compression test on a Gleeble 3500...  相似文献   
7.
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   
8.
9.
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   
10.
分析了基于家庭网络开展多网络业务融合的多种形式和优势,并对基于家庭网络的多网络业务融合的实现方式进行了探讨。  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