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   43271篇
  免费   14868篇
  国内免费   15篇
电工技术   982篇
综合类   5篇
化学工业   18042篇
金属工艺   487篇
机械仪表   867篇
建筑科学   1767篇
矿业工程   2篇
能源动力   1010篇
轻工业   7427篇
水利工程   339篇
石油天然气   53篇
无线电   7547篇
一般工业技术   12239篇
冶金工业   2452篇
原子能技术   189篇
自动化技术   4746篇
  2023年   27篇
  2022年   53篇
  2021年   315篇
  2020年   1472篇
  2019年   3220篇
  2018年   3150篇
  2017年   3469篇
  2016年   3954篇
  2015年   4008篇
  2014年   3980篇
  2013年   5212篇
  2012年   2861篇
  2011年   2526篇
  2010年   2770篇
  2009年   2712篇
  2008年   2270篇
  2007年   2061篇
  2006年   1832篇
  2005年   1533篇
  2004年   1491篇
  2003年   1478篇
  2002年   1401篇
  2001年   1230篇
  2000年   1187篇
  1999年   630篇
  1998年   778篇
  1997年   469篇
  1996年   313篇
  1995年   210篇
  1994年   177篇
  1993年   188篇
  1992年   79篇
  1991年   96篇
  1990年   78篇
  1989年   74篇
  1988年   64篇
  1987年   64篇
  1986年   83篇
  1985年   55篇
  1984年   66篇
  1983年   52篇
  1982年   60篇
  1981年   52篇
  1980年   54篇
  1979年   31篇
  1978年   46篇
  1977年   55篇
  1976年   80篇
  1975年   14篇
  1974年   12篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Monitoring the temperature in liquid hydrogen (LH2) storage tanks on ships is important for the safety of maritime navigation. In addition, accurate temperature measurement is also required for commercial transactions. Temperature and pressure define the density of liquid hydrogen, which is directly linked to trading interests. In this study, we developed and tested a liquid hydrogen temperature monitoring system that uses platinum resistance sensors with a nominal electrical resistance of approximately 1000 Ω at room temperature, PT-1000, for marine applications. The temperature measurements were carried out using a newly developed temperature monitoring system under different pressure conditions. The measured values are compared with a calibrated reference PT-1000 resistance thermometer. We confirm a measurement accuracy of ±50 mK in a pressure range of 0.1 MPa–0.5 MPa.  相似文献   
2.
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   
3.
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   
4.
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