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   381552篇
  免费   29652篇
  国内免费   15320篇
电工技术   21346篇
技术理论   57篇
综合类   25093篇
化学工业   64514篇
金属工艺   21191篇
机械仪表   24176篇
建筑科学   29493篇
矿业工程   12175篇
能源动力   10906篇
轻工业   25405篇
水利工程   6397篇
石油天然气   24547篇
武器工业   3147篇
无线电   41797篇
一般工业技术   44204篇
冶金工业   19764篇
原子能技术   3744篇
自动化技术   48568篇
  2024年   1256篇
  2023年   5653篇
  2022年   10363篇
  2021年   14412篇
  2020年   11172篇
  2019年   9054篇
  2018年   10304篇
  2017年   11659篇
  2016年   10520篇
  2015年   14261篇
  2014年   18662篇
  2013年   22373篇
  2012年   23998篇
  2011年   26659篇
  2010年   23229篇
  2009年   22118篇
  2008年   21893篇
  2007年   21055篇
  2006年   21594篇
  2005年   18780篇
  2004年   12290篇
  2003年   10683篇
  2002年   9745篇
  2001年   8813篇
  2000年   9049篇
  1999年   10304篇
  1998年   8556篇
  1997年   7019篇
  1996年   6615篇
  1995年   5572篇
  1994年   4486篇
  1993年   3186篇
  1992年   2564篇
  1991年   2024篇
  1990年   1540篇
  1989年   1264篇
  1988年   1039篇
  1987年   662篇
  1986年   532篇
  1985年   339篇
  1984年   236篇
  1983年   198篇
  1982年   199篇
  1981年   125篇
  1980年   140篇
  1979年   77篇
  1978年   35篇
  1977年   38篇
  1976年   59篇
  1975年   22篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
131.
Li2ZrO3-modified LiNi0.5Mn0.5O2 materials with improved electrochemical performance were directly synthesized by a simple mechanical milling route with ZrO2, Li2CO3 and Ni0.5Mn0.5(OH)2 precursors...  相似文献   
132.
133.
Orthorhombic molybdenum trioxide (MoO3) is one of the most promising anode materials for sodium‐ion batteries because of its rich chemistry associated with multiple valence states and intriguing layered structure. However, MoO3 still suffers from the low rate capability and poor cycle induced by pulverization during de/sodiation. An ingenious two‐step synthesis strategy to fine tune the layer structure of MoO3 targeting stable and fast sodium ionic diffusion channels is reported here. By integrating partially reduction and organic molecule intercalation methodologies, the interlayer spacing of MoO3 is remarkably enlarged to 10.40 Å and the layer structural integration are reinforced by dimercapto groups of bismuththiol molecules. Comprehensive characterizations and density functional theory calculations prove that the intercalated bismuththiol (DMcT) molecules substantially enhanced electronic conductivity and effectively shield the electrostatic interaction between Na+ and the MoO3 host by conjugated double bond, resulting in improved Na+ insertion/extraction kinetics. Benefiting from these features, the newly devised layered MoO3 electrode achieves excellent long‐term cycling stability and outstanding rate performance. These achievements are of vital significance for the preparation of sodium‐ion battery anode materials with high‐rate capability and long cycling life using intercalation chemistry.  相似文献   
134.
Unreliable mobility values, and particularly greatly overestimated values and severely distorted temperature dependences, have recently hampered the development of the organic transistor field. Given that organic field‐effect transistors (OFETs) have been routinely used to evaluate mobility, precise parameter extraction using the electrical properties of OFETs is thus of primary importance. This review examines the origins of the various mobilities that must be determined for OFET applications, the relevant extraction methods, and the data selection limitations, which help in avoiding conceptual errors during mobility extraction. For increased precision, the review also discusses device fabrication considerations, calibration of both the specific gate‐dielectric capacitance and the threshold voltage, the contact effects, and the bias and temperature dependences, which must actually be handled with great care but have mostly been overlooked to date. This review serves as a systematic overview of the OFET mobility extraction process to ensure high precision and will also aid in improving future research.  相似文献   
135.
慕星宇  王佳璐 《电子测试》2020,(10):137-138,130
本文对国内外的电视技术发展现状进行了充分的研究和分析,并对超高清电视系统的相关图像技术参数进行了分析和介绍。  相似文献   
136.
介绍机械制造厂燃煤锅炉的烟尘特点,分析滤料失效的原因,提出一套针对该工况的滤料解决方案。介绍针对复杂工况条件所选用的纤维种类以及复合面层原料成分配比的确定,最终选用针刺工艺加工并对该新产品的基本性能进行了测试分析。  相似文献   
137.
曾雄伟  程红莉  王桂彩 《玻璃》2015,42(6):14-17
简述了压力管道用安全阀的分类及选择,通过实例介绍如何选用安全阀。  相似文献   
138.
139.
Cobalt-incorporated MCM-41(Co-MCM-41) was used as a heterogeneous catalyst for the ozonation of para-chlorobenzoic acid (p-CBA) in aqueous solution. Cobalt oxide supported on MCM-41(Co/MCM-41) was synthesized for comparison. Their textural properties were elucidated by various characterization techniques to understand the relationship between surface texture and catalytic activity. TOC removal at 60 min reached 91% with Co-MCM-41, 83% with Co/MCM-41 and only 52% with ozone alone, respectively. Observations from diffuse reflection spectroscopy demonstrated that different metal phases were formed in these cobalt-modified molecular sieves samples. Radical scavenger experiments indicated the formation of hydroxyl radicals that were responsible for the effective degradation of p-CBA. An integrated approach to the catalytic mechanism was proposed by considering the variation of pH in the course of ozonation as well as its subsequent influence on the dissociation of targeted compounds and surface charge of the catalyst. In the reusability experiments, the reused Co-MCM-41 was able to regain the same catalytic capability as the fresh one within 5 cycles. X-ray photoelectron spectroscopy results indicated that a part of Co2+ was oxidized to Co3+ after oxidation reaction.  相似文献   
140.
微型步进马达线圈组卷线上下料基本靠手动作业,效率低下,同时因工人技术水平的不同造成产品品质不稳定的问题多发.为此专门设计了微型步进马达线圈组自动卷线及上下料设备.通过结合现阶段的先进工业技术,采用振动盘分离区分进料,多机构并联三菱PLC及威纶人机界面触摸屏研发了此微型步进马达线圈组自动上下料及卷线设备.通过该设备实现了微型步进马达因工人不足导致产能减少和品质多发问题,减少企业成本,提升产品品质.  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