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   43080篇
  免费   14970篇
  国内免费   17篇
电工技术   799篇
综合类   10篇
化学工业   18499篇
金属工艺   567篇
机械仪表   1156篇
建筑科学   1766篇
矿业工程   2篇
能源动力   1145篇
轻工业   7489篇
水利工程   291篇
石油天然气   57篇
武器工业   2篇
无线电   7756篇
一般工业技术   12542篇
冶金工业   931篇
原子能技术   135篇
自动化技术   4920篇
  2024年   6篇
  2023年   99篇
  2022年   112篇
  2021年   421篇
  2020年   1563篇
  2019年   3273篇
  2018年   3259篇
  2017年   3555篇
  2016年   4076篇
  2015年   4099篇
  2014年   4086篇
  2013年   5344篇
  2012年   3118篇
  2011年   2920篇
  2010年   2983篇
  2009年   2881篇
  2008年   2407篇
  2007年   2112篇
  2006年   1860篇
  2005年   1558篇
  2004年   1500篇
  2003年   1486篇
  2002年   1392篇
  2001年   1223篇
  2000年   1183篇
  1999年   570篇
  1998年   210篇
  1997年   171篇
  1996年   123篇
  1995年   80篇
  1994年   49篇
  1993年   61篇
  1992年   39篇
  1991年   40篇
  1990年   40篇
  1989年   27篇
  1988年   18篇
  1987年   17篇
  1986年   13篇
  1985年   11篇
  1984年   7篇
  1983年   9篇
  1981年   6篇
  1980年   5篇
  1978年   5篇
  1977年   8篇
  1976年   10篇
  1975年   7篇
  1973年   4篇
  1967年   5篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Hepatic fibrosis occurs when liver tissue becomes scarred from repetitive liver injury and inflammatory responses; it can progress to cirrhosis and eventually to hepatocellular carcinoma. Previously, we reported that neoagarooligosaccharides (NAOs), produced by the hydrolysis of agar by β-agarases, have hepatoprotective effects against acetaminophen overdose-induced acute liver injury. However, the effect of NAOs on chronic liver injury, including hepatic fibrosis, has not yet been elucidated. Therefore, we examined whether NAOs protect against fibrogenesis in vitro and in vivo. NAOs ameliorated PAI-1, α-SMA, CTGF and fibronectin protein expression and decreased mRNA levels of fibrogenic genes in TGF-β-treated LX-2 cells. Furthermore, downstream of TGF-β, the Smad signaling pathway was inhibited by NAOs in LX-2 cells. Treatment with NAOs diminished the severity of hepatic injury, as evidenced by reduction in serum alanine aminotransferase and aspartate aminotransferase levels, in carbon tetrachloride (CCl4)-induced liver fibrosis mouse models. Moreover, NAOs markedly blocked histopathological changes and collagen accumulation, as shown by H&E and Sirius red staining, respectively. Finally, NAOs antagonized the CCl4-induced upregulation of the protein and mRNA levels of fibrogenic genes in the liver. In conclusion, our findings suggest that NAOs may be a promising candidate for the prevention and treatment of chronic liver injury via inhibition of the TGF-β/Smad signaling pathway.  相似文献   
2.
3.
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   
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.
Multimedia Systems - The preferences of Web information purchasers are changing. Cost-effectiveness (i.e., an emphasis on performance with respect to price) is becoming less regarded than...  相似文献   
7.
8.
9.
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