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   114489篇
  免费   9177篇
  国内免费   4702篇
电工技术   6162篇
技术理论   9篇
综合类   7398篇
化学工业   19342篇
金属工艺   6045篇
机械仪表   7552篇
建筑科学   8594篇
矿业工程   3522篇
能源动力   3573篇
轻工业   7052篇
水利工程   1734篇
石油天然气   8106篇
武器工业   798篇
无线电   12410篇
一般工业技术   14434篇
冶金工业   5663篇
原子能技术   1270篇
自动化技术   14704篇
  2024年   312篇
  2023年   1773篇
  2022年   2729篇
  2021年   4256篇
  2020年   3281篇
  2019年   2912篇
  2018年   3344篇
  2017年   3749篇
  2016年   3230篇
  2015年   4179篇
  2014年   5371篇
  2013年   6540篇
  2012年   6793篇
  2011年   7573篇
  2010年   6519篇
  2009年   6196篇
  2008年   6118篇
  2007年   5869篇
  2006年   6094篇
  2005年   5360篇
  2004年   3693篇
  2003年   3711篇
  2002年   3746篇
  2001年   3280篇
  2000年   3090篇
  1999年   3384篇
  1998年   2732篇
  1997年   2244篇
  1996年   2240篇
  1995年   1826篇
  1994年   1503篇
  1993年   1135篇
  1992年   836篇
  1991年   639篇
  1990年   494篇
  1989年   400篇
  1988年   370篇
  1987年   227篇
  1986年   153篇
  1985年   121篇
  1984年   81篇
  1983年   49篇
  1982年   63篇
  1981年   41篇
  1980年   31篇
  1979年   23篇
  1977年   7篇
  1976年   9篇
  1975年   5篇
  1945年   4篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
The esophagus is a tubular-shaped muscular organ where swallowed fluids and muscular contractions constitute a highly dynamic environment. The turbulent, coordinated processes that occur through the oropharyngeal conduit can often compromise targeted administration of therapeutic drugs to a lesion, significantly reducing therapeutic efficacy. Here, magnetically guidable drug vehicles capable of strongly adhering to target sites using a bioengineered mussel adhesive protein (MAP) to achieve localized delivery of therapeutic drugs against the hydrodynamic physiological conditions are proposed. A suite of highly uniform microparticles embedded with iron oxide (IO) nanoparticles (MAP@IO MPs) is microfluidically fabricated using the genipin-mediated covalent cross-linking of bioengineered MAP. The MAP@IO MPs are successfully targeted to a specific region and prolongedly retained in the tubular-structured passageway. In particular, orally administered MAP@IO MPs are effectively captured in the esophagus in vivo in a magnetically guidable manner. Moreover, doxorubicin (DOX)-loaded MAP@IO MPs exhibit a sustainable DOX release profile, effective anticancer therapeutic activity, and excellent biocompatibility. Thus, the magnetically guidable locomotion and robust underwater adhesive properties of the proteinaceous soft microbots can provide an intelligent modular approach for targeted locoregional therapeutics delivery to a specific lesion site in dynamic fluid-associated tubular organs such as the esophagus.  相似文献   
42.
43.
With the emergence of large-scale knowledge base, how to use triple information to generate natural questions is a key technology in question answering systems. The traditional way of generating questions require a lot of manual intervention and produce lots of noise. To solve these problems, we propose a joint model based on semi-automated model and End-to-End neural network to automatically generate questions. The semi-automated model can generate question templates and real questions combining the knowledge base and center graph. The End-to-End neural network directly sends the knowledge base and real questions to BiLSTM network. Meanwhile, the attention mechanism is utilized in the decoding layer, which makes the triples and generated questions more relevant. Finally, the experimental results on SimpleQuestions demonstrate the effectiveness of the proposed approach.  相似文献   
44.
45.
46.
Science China Technological Sciences - Accurate modelling of lithium ion batteries is crucial for battery management in electric vehicles. Recent studies have revealed the fractional order nature...  相似文献   
47.
48.
With the ambition of solving the challenges of the shortage of fossil fuels and their associated environmental pollution, visible-light-driven splitting of water into hydrogen and oxygen using semiconductor photocatalysts has emerged as a promising technology to provide environmentally friendly energy vectors. Among the current library of developed photocatalysts, organic conjugated polymers present unique advantages of sufficient light-absorption efficiency, excellent stability, tunable electronic properties, and economic applicability. As a class of rising photocatalysts, organic conjugated polymers offer high flexibility in tuning the framework of the backbone and porosity to fulfill the requirements for photocatalytic applications. In the past decade, significant progress has been made in visible-light-driven water splitting employing organic conjugated polymers. The recent development of the structural design principles of organic conjugated polymers (including linear, crosslinked, and supramolecular self-assembled polymers) toward efficient photocatalytic hydrogen evolution, oxygen evolution, and overall water splitting is described, thus providing a comprehensive reference for the field. Finally, current challenges and perspectives are also discussed.  相似文献   
49.
Sun  Yue  Zhu  Yu  Li  Ying  Zhang  Mingyu 《Wireless Personal Communications》2020,111(1):83-96
Wireless Personal Communications - The existing long term evolution networks originally designed for human-to-human communications are hard to tackle numerous and bursty random access requests from...  相似文献   
50.
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