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   21446篇
  免费   1322篇
  国内免费   55篇
电工技术   308篇
综合类   25篇
化学工业   4605篇
金属工艺   878篇
机械仪表   1299篇
建筑科学   426篇
矿业工程   6篇
能源动力   863篇
轻工业   1846篇
水利工程   90篇
石油天然气   15篇
无线电   3653篇
一般工业技术   4623篇
冶金工业   1539篇
原子能技术   291篇
自动化技术   2356篇
  2023年   265篇
  2022年   135篇
  2021年   675篇
  2020年   471篇
  2019年   496篇
  2018年   699篇
  2017年   661篇
  2016年   769篇
  2015年   602篇
  2014年   940篇
  2013年   1391篇
  2012年   1461篇
  2011年   1791篇
  2010年   1300篇
  2009年   1332篇
  2008年   1214篇
  2007年   937篇
  2006年   813篇
  2005年   710篇
  2004年   640篇
  2003年   589篇
  2002年   597篇
  2001年   518篇
  2000年   438篇
  1999年   425篇
  1998年   709篇
  1997年   416篇
  1996年   370篇
  1995年   255篇
  1994年   167篇
  1993年   151篇
  1992年   109篇
  1991年   99篇
  1990年   75篇
  1989年   86篇
  1988年   74篇
  1987年   63篇
  1986年   51篇
  1985年   43篇
  1984年   37篇
  1983年   28篇
  1982年   31篇
  1981年   26篇
  1980年   27篇
  1979年   13篇
  1977年   21篇
  1976年   33篇
  1975年   16篇
  1974年   13篇
  1973年   9篇
排序方式: 共有10000条查询结果,搜索用时 518 毫秒
21.
Chun  Dong Hyun  Rhim  Geun Bae  Youn  Min Hye  Deviana  Deviana  Lee  Ji Eun  Park  Ji Chan  Jeong  Heondo 《Topics in Catalysis》2020,63(9-10):793-809
Topics in Catalysis - Fischer–Tropsch synthesis (FTS) is a promising way to produce clean liquid fuels and high value-added chemicals from low-value carbon-containing resources such as coal,...  相似文献   
22.
23.
Here, we report a facile approach to electrostatically couple the surface charges of graphite nanoplate (GNP) fillers and poly(methyl methacrylate) (PMMA) polymer particles using ethylene maleic anhydride (EMA) copolymer as an electrostatic coupling agent. Our strategy involved switching the intrinsic repulsive electrostatic interactions between the directly exfoliated GNPs fillers and the PMMA particles to attractive electrostatic surface interactions for preparing core(PMMA)-shell (GNP) precursor in order to optimizing 3-dimensionally dispersed polymer nanocomposite. As a result, the electrical conductivity of the composites dramatically increased by a factor of 16.7 in the EMA-coupled GNP/PMMA composites compared with that of the EMA-free GNP/PMMA composites. In addition, the percolation threshold was also notably reduced from 0.32 to 0.159 vol% after electrostatic coupling of the GNPs fillers and PMMA particles. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48390.  相似文献   
24.
Metals and Materials International - This study investigated the influence of the initial grain size on the plastic deformation and tunnel defects that occurred from friction stir welding of...  相似文献   
25.
A facile sol–gel procedure has been developed for the synthesis of colloidal alumina nanocrystals. For the first time, optical characterization procedures were employed to study the quantum confinement effects in optical properties of the prepared Al2O3 sol. Accordingly, the hyperbolic band model was used to determine the optical band gap of colloidal alumina nanocrystals. X‐Ray diffraction pattern was used to study the crystallographic phase of the dried gel. Morphological characterization was performed using scanning electron microscopy (SEM). Inductively Coupled Plasma (ICP) emission spectroscopy was used to determination purity of the Al2O3 powder. High‐resolution TEM showed that the diameter of colloidal nanocrystals is about 10 nm. Photoluminescence spectroscopy demonstrated that quantum yields for colloidal nanocrystals are 68% with 300 nm excitation wavelength. The experimental observations confirm that highly stable alumina sol with strong UV emission was synthesized. The mentioned optical properties have not been reported before.  相似文献   
26.
27.
Over the past few decades, crystalline silicon solar cells have been extensively studied due to their high efficiency, high reliability, and low cost. In addition, these types of cells lead the industry and account for more than half of the market. For the foreseeable future, Si will still be a critical material for photovoltaic devices in the solar cell industry. In this paper, we discuss key issues, cell concepts, and the status of recent high-efficiency crystalline silicon solar cells.  相似文献   
28.
The majority of visualizations on the web are still stored as raster images, making them inaccessible to visually impaired users. We propose a deep‐neural‐network‐based approach that automatically recognizes key elements in a visualization, including a visualization type, graphical elements, labels, legends, and most importantly, the original data conveyed in the visualization. We leverage such extracted information to provide visually impaired people with the reading of the extracted information. Based on interviews with visually impaired users, we built a Google Chrome extension designed to work with screen reader software to automatically decode charts on a webpage using our pipeline. We compared the performance of the back‐end algorithm with existing methods and evaluated the utility using qualitative feedback from visually impaired users.  相似文献   
29.
30.
Vegetable soup (VS), a plant-based functional food, has been used as a traditional folk medicine and is attracting attention for its ability to enhance the immune response. β-Glucan, a well-established and effective immunomodulator, has synergistic effects when used in combination with some bioactive compounds. In the present study, we aimed to evaluate the synergistic immunomodulatory effects of the combination of VS and β-glucan on macrophage-mediated immune responses. β-Glucan was demonstrated to synergistically enhance the VS-stimulated immune response, including the production of interleukin-6, tumor necrosis factor-α, and nitric oxide, mainly through the mitogen-activated protein kinase pathway in macrophages. In addition, this combination has the potential for further development in functional foods with immune-enhancing activity.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10068-021-00888-x.  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