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   5813篇
  免费   320篇
  国内免费   46篇
电工技术   74篇
综合类   20篇
化学工业   1633篇
金属工艺   124篇
机械仪表   220篇
建筑科学   154篇
矿业工程   4篇
能源动力   375篇
轻工业   559篇
水利工程   84篇
石油天然气   36篇
无线电   555篇
一般工业技术   1069篇
冶金工业   277篇
原子能技术   83篇
自动化技术   912篇
  2024年   23篇
  2023年   114篇
  2022年   324篇
  2021年   399篇
  2020年   301篇
  2019年   328篇
  2018年   360篇
  2017年   298篇
  2016年   325篇
  2015年   195篇
  2014年   324篇
  2013年   534篇
  2012年   306篇
  2011年   313篇
  2010年   278篇
  2009年   245篇
  2008年   166篇
  2007年   146篇
  2006年   132篇
  2005年   95篇
  2004年   73篇
  2003年   71篇
  2002年   55篇
  2001年   42篇
  2000年   36篇
  1999年   37篇
  1998年   69篇
  1997年   59篇
  1996年   42篇
  1995年   53篇
  1994年   24篇
  1993年   34篇
  1992年   30篇
  1991年   25篇
  1990年   24篇
  1989年   22篇
  1988年   15篇
  1987年   30篇
  1986年   30篇
  1985年   22篇
  1984年   30篇
  1983年   26篇
  1982年   16篇
  1981年   8篇
  1980年   14篇
  1979年   13篇
  1978年   12篇
  1977年   11篇
  1976年   14篇
  1975年   8篇
排序方式: 共有6179条查询结果,搜索用时 15 毫秒
991.
Telecommunication Systems - In the era of Internet-of-things (IoT), the future 5G networks are supposed to provide ubiquitous connectivity, high speed, as well as low latency and energy efficiency...  相似文献   
992.
Mobile Networks and Applications - An effective measure of Key Performance Indicators (KPIs) is of great significance to enhance the capabilities of a decision support system (DSS) of any...  相似文献   
993.
Mobile Networks and Applications - In Wireless Sensor Networks (WSNs), energy-efficient routing is required to conserve the scarce resources of these networks. Various energy-efficient routing...  相似文献   
994.
ZnAl2O4 and ZnO nanostructure particles and in situ crystallization of zinc aluminate and zinc oxide coating layers on sintered α-Al2O3 and γ-Al2O3 granules by the microwave-assisted combustion method were investigated. For powders, the effects of solution pH value and for coated samples the influence of support type on the structure, microstructure, and photocatalytic activity of powders were studied. Results showed that variation of synthesis pH value caused to considerable change in agglomeration, specific surface area, obtaining up to 88 and 92% yields for zinc aluminate and zinc oxide nanoparticles, respectively. γ-alumina granules were more appropriate supports than the α-alumina ones because of the better photocatalytic activities and lower extent of the attritions for both zinc aluminate and zinc oxide coating layers.  相似文献   
995.
The available aeromagnetic data together with information from some available wells have been used in the current study to shed the light on the geothermal setup of the Nile Delta Province. The aeromagnetic data was reduced-to-pole and critically analyzed using the Spectral Analysis Technique through the Fast Fourier Transform (FFT), to determine the expected depths to the Basement and Curie Point (CPD) surfaces. The geothermal gradient between CPD and earth's surface was estimated, and accordingly the heat flow was evaluated using the proposed thermal conductivity. Then, the Basement Surface Temperature (BST) was estimated, by which the geothermal gradient and heat flow for the igneous-rocky basement and sedimentary-rocky horizon was independently predicted. By which, it could be possible to distinguish between the heat flow contribution from each horizon separately.  相似文献   
996.
Telecommunication Systems - Integration of optical and millimeter-wave systems provide a promising solution for future giga-bits per second wireless communication systems. We have proposed and...  相似文献   
997.
Microgrids provide promising solution for integration of renewable energy sources in the electrical grid. To exploit the key benefits, achieving the economical operation of renewable aided microgrids has become necessary and is a challenging task. This paper presents an efficient optimization model to minimize the operational cost of a solar integrated microgrid. We formulate a joint optimization mixed integer problem for appropriate modeling of the system under various practical constraints. An efficient solution is obtained with a distributed approach such that the original problem is solved in two stages. Dual decomposition approach is adopted for cost, emissions, and solar share optimization. Lagrange relaxation, Lambda iteration method, and binary integer programming are employed to obtain the joint optimization solution. Finally, the performance of the proposed model is validated through simulations that show that an overall cost reduction of 4.2070e+04 $ and emission reduction of 7.2001e+03 kg are achieved with the proposed model.  相似文献   
998.
A fibrous silica zeolite Y (HY@KCC‐1) catalyst with a high surface area of 568 m2/g and unique core‐shell morphology was successfully synthesized via a modified KCC‐1 synthesis method. Characterization of the catalysts was achieved with X‐ray powder diffraction (XRD), field emission scanning microscope (FESEM), N2 adsorption/desorption, and 2,6‐dimethylpyridine adsorbed Fourier‐transform infrared spectroscopy (FTIR). The Pt/HY@KCC‐1 has displayed complete n‐dodecane conversion coupled with an incredibly enhanced isomer yield of 72% at 350°C, nearly two‐fold higher than that of unmodified Pt/HY catalyst. Remarkably, Pt/HY@KCC‐1 had an internal effectiveness factor (η) of unity and negligible internal diffusion limitation, thus suggesting its potential application in hydroisomerization of higher hydrocarbons for enhancing fuel properties.  相似文献   
999.
Battery is the sole power source for Internet of thing (IoT) sensors. Due to limited shelf life, the batteries are required to be replaced intermittently. This periodic replacement of batteries is inflated in terms of both logistics and time. This article illustrates conceptual design, development, and characterization of a flow‐based electromagnetic‐type energy harvester (F‐EH) using microplanar coil for IoT sensors application. The F‐EH converts hydro energy into useful electrical energy utilizing electromagnetic transduction mechanism. The microfabrication and macrofabrication techniques adopted to manufacture harvester's components are presented. The F‐EH has been successfully characterized by laboratory scale experimental flow test loop commissioned for this work. Experimentation with associated uncertainty analysis prevails that at a matching impedance, the F‐EH can generate a 686 μW of maximum power at an operating flow rate of 12 L/min with an uncertainty of 8.1%.  相似文献   
1000.
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