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   52670篇
  免费   15025篇
  国内免费   23篇
电工技术   912篇
综合类   3篇
化学工业   19049篇
金属工艺   672篇
机械仪表   1038篇
建筑科学   2234篇
矿业工程   62篇
能源动力   1124篇
轻工业   8335篇
水利工程   400篇
石油天然气   165篇
无线电   8316篇
一般工业技术   13737篇
冶金工业   5704篇
原子能技术   165篇
自动化技术   5802篇
  2022年   119篇
  2021年   343篇
  2020年   1511篇
  2019年   3274篇
  2018年   3277篇
  2017年   3534篇
  2016年   3994篇
  2015年   4062篇
  2014年   4079篇
  2013年   5523篇
  2012年   2995篇
  2011年   2769篇
  2010年   2993篇
  2009年   2843篇
  2008年   2525篇
  2007年   2360篇
  2006年   2110篇
  2005年   1781篇
  2004年   1681篇
  2003年   1687篇
  2002年   1567篇
  2001年   1420篇
  2000年   1376篇
  1999年   848篇
  1998年   1383篇
  1997年   889篇
  1996年   629篇
  1995年   446篇
  1994年   400篇
  1993年   416篇
  1992年   297篇
  1991年   251篇
  1990年   269篇
  1989年   224篇
  1988年   226篇
  1987年   211篇
  1986年   203篇
  1985年   257篇
  1984年   213篇
  1983年   214篇
  1982年   202篇
  1981年   181篇
  1980年   194篇
  1979年   133篇
  1978年   144篇
  1977年   246篇
  1976年   321篇
  1975年   137篇
  1974年   126篇
  1973年   107篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Recent advances in three‐dimensional (3D) printing have enabled the fabrication of interesting structures which are not achievable using traditional fabrication approaches. The 3D printing of carbon microtube composite inks allows fabrication of conductive structures for practical applications in soft robotics and tissue engineering. However, it is challenging to achieve 3D printed structures from solution‐based composite inks, which requires an additional process to solidify the ink. Here, we introduce a wet 3D printing technique which uses a coagulation bath to fabricate carbon microtube composite structures. We show that through a facile nanogrooving approach which introduces cavitation and channels on carbon microtubes, enhanced interfacial interactions with a chitosan polymer matrix are achieved. Consequently, the mechanical properties of the 3D printed composites improve when nanogrooved carbon microtubes are used, compared to untreated microtubes. We show that by carefully controlling the coagulation bath, extrusion pressure, printing distance and printed line distance, we can 3D print composite lattices which are composed of well‐defined and separated printed lines. The conductive composite 3D structures with highly customised design presented in this work provide a suitable platform for applications ranging from soft robotics to smart tissue engineering scaffolds. © 2019 Society of Chemical Industry  相似文献   
2.
3.
With liquefied natural gas becoming increasingly prevalent as a flexible source of energy, the design and optimization of industrial refrigeration cycles becomes even more important. In this article, we propose an integrated surrogate modeling and optimization framework to model and optimize the complex CryoMan Cascade refrigeration cycle. Dimensionality reduction techniques are used to reduce the large number of process decision variables which are subsequently supplied to an array of Gaussian processes, modeling both the process objective as well as feasibility constraints. Through iterative resampling of the rigorous model, this data-driven surrogate is continually refined and subsequently optimized. This approach was not only able to improve on the results of directly optimizing the process flow sheet but also located the set of optimal operating conditions in only 2 h as opposed to the original 3 weeks, facilitating its use in the operational optimization and enhanced process design of large-scale industrial chemical systems.  相似文献   
4.
The aim of this exploratory study has been to investigate the fire properties and environmental aspects of different upholstery material combinations, mainly for domestic applications. An analysis of the sustainability and circularity of selected textiles, along with lifecycle assessment, is used to qualitatively evaluate materials from an environmental perspective. The cone calorimeter was the primary tool used to screen 20 different material combinations from a fire performance perspective. It was found that textile covers of conventional fibres such as wool, cotton and polyester, can be improved by blending them with fire resistant speciality fibres. A new three‐dimensional web structure has been examined as an alternative padding material, showing preliminary promising fire properties with regard to ignition time, heat release rates and smoke production.  相似文献   
5.
6.
7.
8.
9.
Lobster krill (Munida genus) represents an under‐valued crustacean frequently caught on European fishing banks. In this work, its sensory, microbiological and biochemical qualities were evaluated during chilled storage. Additionally, the effects of a prestorage antimelanosic treatment consisting of soaking in sodium metabisulphite (SMB) solutions at two different concentrations (0.25% and 0.75%) were also studied. SMB prestorage treatment provided lobster specimens that still exhibited acceptable sensory quality after 10 days of storage, while control specimens were unacceptable at that time. SMB treatment also resulted in a significant (P < 0.05) inhibition of microbial growth, mainly of Enterobacteriaceae, psychrotrophes and proteolytic bacteria. Low lipid oxidation levels were observed for all batches; however, a significantly higher (P < 0.05) retention of polyunsaturated fatty acids was found in SMB‐treated lobster, especially in the 0.75% SMB batch. The results presented here open the way to the potential commercialisation of currently under‐utilised lobster krill as a chilled product.  相似文献   
10.
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