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   168270篇
  免费   14068篇
  国内免费   5802篇
电工技术   9050篇
技术理论   11篇
综合类   8796篇
化学工业   27536篇
金属工艺   10105篇
机械仪表   10384篇
建筑科学   9953篇
矿业工程   4020篇
能源动力   3870篇
轻工业   9591篇
水利工程   3179篇
石油天然气   9618篇
武器工业   1054篇
无线电   18000篇
一般工业技术   27189篇
冶金工业   11115篇
原子能技术   5028篇
自动化技术   19641篇
  2024年   2012篇
  2023年   2803篇
  2022年   4820篇
  2021年   6497篇
  2020年   5017篇
  2019年   4090篇
  2018年   5231篇
  2017年   5673篇
  2016年   5266篇
  2015年   5726篇
  2014年   7363篇
  2013年   8941篇
  2012年   9554篇
  2011年   10251篇
  2010年   8714篇
  2009年   8536篇
  2008年   8427篇
  2007年   7909篇
  2006年   7326篇
  2005年   6257篇
  2004年   4791篇
  2003年   4713篇
  2002年   4756篇
  2001年   4326篇
  2000年   3749篇
  1999年   3330篇
  1998年   2628篇
  1997年   2213篇
  1996年   1984篇
  1995年   1736篇
  1994年   1470篇
  1993年   1247篇
  1992年   1227篇
  1991年   1075篇
  1990年   1092篇
  1989年   1012篇
  1988年   897篇
  1987年   842篇
  1986年   767篇
  1985年   716篇
  1984年   702篇
  1981年   668篇
  1979年   736篇
  1978年   777篇
  1977年   739篇
  1976年   755篇
  1975年   713篇
  1974年   719篇
  1973年   723篇
  1972年   705篇
排序方式: 共有10000条查询结果,搜索用时 587 毫秒
71.
全球最大的家居建材零售商——美国家得宝(The Home Depot)8月26日在北京宣布,对于去年12月13日从天津家世界家居建材超市有限公司(下称"家世界")收购而来的12家分店的整合工作已经完毕,家得宝由此正式进入中国市场。家得宝在中国  相似文献   
72.
张宇 《建筑创作》2005,(8):34-35
刚拿到这本书时.以为只是布正伟先生四十多年建筑创作生涯文论的汇总的集子.但稍静下来翻阅便发现,呈现给读者的《建筑视界论——现代建筑创作平台建构的理念与实践》为广大建筑师展示的是一幅将文化研析、城市体验、环境设计、职业修养融为一体的建筑创作理论的“风情画”.从而使国人关注的建筑创作的多元化理念得到尽情的阐发。  相似文献   
73.
Zhu  Xuefang  He  Meng  Xiao  Ling  Liu  Haozhuo  Hu  Mancheng  Li  Shuni  Zhai  Quanguo  Chen  Yu  Jiang  Yucheng 《Journal of Applied Electrochemistry》2022,52(6):979-987
Journal of Applied Electrochemistry - A novel nitrite electrochemical biosensor is constructed by glassy carbon electrodes (GC) coated by chloroperoxidase (CPO) -Au nanoparticles-MoS2 nanoflowers...  相似文献   
74.
Theoretical Foundations of Chemical Engineering - A new approach to the processing of the dump waste product stored in the tailings dumps of the nickel production enterprise Punda Gourda (Cuba) has...  相似文献   
75.
Glass and Ceramics - The granulometric compositions of native and acid-activated rocks containing aluminosilicates are compared. It is shown that in water rocks gradually dissolve and the particle...  相似文献   
76.
Glass and Ceramics - The results of experimental studies of the transmission of 12 and 15 keV electron beams through tapered glass macro-capillaries are presented. Measurements showed that there is...  相似文献   
77.
The current research of state of charge(SoC) online estimation of lithium-ion battery(LiB) in electric vehicles(EVs)mainly focuses on adopting or improving of battery models and estimation filters. However, little attention has been paid to the accuracy of various open circuit voltage(OCV) models for correcting the SoC with aid of the ampere-hour counting method. This paper presents a comprehensive comparison study on eighteen OCV models which cover the majority of models used in literature. The low-current OCV tests are conducted on the typical commercial LiFePO_4/graphite(LFP) and LiNiMnCoO_2/graphite(NMC) cells to obtain the experimental OCV-SoC curves at different ambient temperature and aging stages. With selected OCV and SoC points from experimental OCV-SoC curves, the parameters of each OCV model are determined by curve fitting toolbox of MATLAB 2013. Then the fitting OCV-SoC curves based on diversified OCV models are also obtained. The indicator of root-mean-square error(RMSE) between the experimental data and fitted data is selected to evaluate the adaptabilities of these OCV models for their main features, advantages,and limitations. The sensitivities of OCV models to ambient temperatures, aging stages, numbers of data points,and SoC regions are studied for both NMC and LFP cells. Furthermore, the influences of these models on SoC estimation are discussed. Through a comprehensive comparison and analysis on OCV models, some recommendations in selecting OCV models for both NMC and LFP cells are given.  相似文献   
78.
Russian Engineering Research - Polymer samples based on polydicyclopentadiene produced from Russian dicyclopentadiene are investigated by thermogravimetric analysis and differential scanning...  相似文献   
79.
The phase structure, chemical stability, sinterability, and electrical performance of the proton‐conducting Ba(Ce,Ti)O3 solid solution with a series of acceptors M (M = In, Y, Sm) synthesized by a modified Pechini method were systematically investigated. The substitution of cerium with titanium was proved as an effective way to improve the stability of BaCeO3. Especially for the BaCe0.95Ti0.05O3?δ sample doped with In, no change in the phase was found even after treatment in the atmosphere containing both CO2 and H2O at 700°C for 10 h. Thanks to the highly sinteractive powders with particle size of ~100 nm, dense ceramics were easily acquired. Moreover, compared with the undoped BaCe0.95Ti0.05O3 sample, In, Y, and Sm dopants further improved the sinterability of the solid solution. In particular, In played a role of sintering aid and led to the largest linear shrinkage of the ceramics. As to the electrical performance, the transport properties of the samples under various atmospheres were analyzed and compared. The impedance tests demonstrated the best electrical performance of the Y‐doped samples.  相似文献   
80.
Manganese oxides are good candidates of strongly correlated electron materials due to the uniqueness of electronic structure of manganese and the mobility of oxygen among lattice sites under external impacts. Here, we used electron beam as the excitation source to explore the structural evolution of YMnO3 and identified a new phase under the radiation of electron beam in the transmission electron microscope. Analyses of the electron energy‐loss spectra reveal that this phase originates from ordered oxygen vacancy. We applied the first principles calculation to pick out the optimized stable structure with a lower polarization, and verified its correctness by electron diffraction and image simulations. Analyses of density of states indicate that weak Y–O covalence is favorable for the existence of ferroelectricity, supporting the electrostatic nature of ferroelectricity in the YMnO3.  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