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   55088篇
  免费   16453篇
  国内免费   1174篇
电工技术   2191篇
技术理论   1篇
综合类   1556篇
化学工业   19839篇
金属工艺   1382篇
机械仪表   1803篇
建筑科学   2856篇
矿业工程   505篇
能源动力   1635篇
轻工业   8503篇
水利工程   672篇
石油天然气   626篇
武器工业   152篇
无线电   9210篇
一般工业技术   13148篇
冶金工业   1467篇
原子能技术   261篇
自动化技术   6908篇
  2024年   77篇
  2023年   273篇
  2022年   594篇
  2021年   977篇
  2020年   1897篇
  2019年   3587篇
  2018年   3522篇
  2017年   3906篇
  2016年   4321篇
  2015年   4595篇
  2014年   4712篇
  2013年   6025篇
  2012年   3930篇
  2011年   3590篇
  2010年   3736篇
  2009年   3599篇
  2008年   3153篇
  2007年   2977篇
  2006年   2607篇
  2005年   2145篇
  2004年   2066篇
  2003年   2132篇
  2002年   2364篇
  2001年   1991篇
  2000年   1561篇
  1999年   797篇
  1998年   263篇
  1997年   251篇
  1996年   183篇
  1995年   143篇
  1994年   99篇
  1993年   91篇
  1992年   75篇
  1991年   84篇
  1990年   59篇
  1989年   50篇
  1988年   29篇
  1987年   35篇
  1986年   30篇
  1985年   30篇
  1984年   12篇
  1983年   19篇
  1982年   16篇
  1981年   10篇
  1980年   16篇
  1978年   8篇
  1977年   10篇
  1976年   7篇
  1975年   8篇
  1973年   9篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
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.
To evaluate the separate impacts on human health and establish effective control strategies, it is crucial to estimate the contribution of outdoor infiltration and indoor emission to indoor PM2.5 in buildings. This study used an algorithm to automatically estimate the long-term time-resolved indoor PM2.5 of outdoor and indoor origin in real apartments with natural ventilation. The inputs for the algorithm were only the time-resolved indoor/outdoor PM2.5 concentrations and occupants’ window actions, which were easily obtained from the low-cost sensors. This study first applied the algorithm in an apartment in Tianjin, China. The indoor/outdoor contribution to the gross indoor exposure and time-resolved infiltration factor were automatically estimated using the algorithm. The influence of outdoor PM2.5 data source and algorithm parameters on the estimated results was analyzed. The algorithm was then applied in four other apartments located in Chongqing, Shenyang, Xi'an, and Urumqi to further demonstrate its feasibility. The results provided indirect evidence, such as the plausible explanations for seasonal and spatial variation, to partially support the success of the algorithm used in real apartments. Through the analysis, this study also identified several further development directions to facilitate the practical applications of the algorithm, such as robust long-term outdoor PM2.5 monitoring using low-cost light-scattering sensors.  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.
The germline carrier of the BRCA1 pathogenic mutation has been well proven to confer an increased risk of breast and ovarian cancer. Despite BRCA1 biallelic pathogenic mutations being extremely rare, they have been reported to be embryonically lethal or to cause Fanconi anemia (FA). Here we describe a patient who was a 48-year-old female identified with biallelic pathogenic mutations of the BRCA1 gene, with no or very subtle FA-features. She was diagnosed with ovarian cancer and breast cancer at the ages of 43 and 44 and had a strong family history of breast and gynecological cancers.  相似文献   
6.
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