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   43654篇
  免费   14707篇
  国内免费   295篇
电工技术   1087篇
技术理论   3篇
综合类   498篇
化学工业   17952篇
金属工艺   657篇
机械仪表   1155篇
建筑科学   2205篇
矿业工程   246篇
能源动力   995篇
轻工业   7345篇
水利工程   420篇
石油天然气   480篇
武器工业   56篇
无线电   7384篇
一般工业技术   12032篇
冶金工业   867篇
原子能技术   78篇
自动化技术   5196篇
  2024年   43篇
  2023年   130篇
  2022年   242篇
  2021年   528篇
  2020年   1657篇
  2019年   3338篇
  2018年   3289篇
  2017年   3640篇
  2016年   4065篇
  2015年   4218篇
  2014年   4165篇
  2013年   5283篇
  2012年   3049篇
  2011年   2717篇
  2010年   2972篇
  2009年   2821篇
  2008年   2321篇
  2007年   2167篇
  2006年   1951篇
  2005年   1660篇
  2004年   1512篇
  2003年   1516篇
  2002年   1443篇
  2001年   1258篇
  2000年   1244篇
  1999年   611篇
  1998年   150篇
  1997年   121篇
  1996年   111篇
  1995年   93篇
  1994年   73篇
  1993年   49篇
  1992年   48篇
  1991年   49篇
  1990年   30篇
  1989年   22篇
  1988年   16篇
  1987年   16篇
  1986年   11篇
  1985年   4篇
  1984年   5篇
  1983年   5篇
  1982年   1篇
  1981年   3篇
  1980年   4篇
  1978年   1篇
  1977年   1篇
  1975年   1篇
  1951年   1篇
  1890年   1篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
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   
3.
4.
5.
6.
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   
7.
With the advent of mobile technologies, well-designed fraction apps can be used to help children gain fraction knowledge, a challenging topic for both teachers and students. The present pilot study adopted a quasi-experimental design to investigate whether children can learn fraction concepts equally well if half of the lesson time (20 min) is replaced with game-based learning. Keeping the total lesson time (40 min) identical, the control group (N = 33) received traditional instruction, and the experimental group (N = 32) was presented with a blended learning approach spending half of the class time (20 min) playing tablet-based fraction games, where each of the learners had their own tablet. The results suggested that in the posttest, the experimental group achieved similar learning gains to the control group and appear to have achieved better performance in the transfer test than the control group. This paper also discusses the efficiency of game-based learning, the mechanism of how fraction games might enhance learning, and the potential of integrating game-based learning in educational settings.  相似文献   
8.
9.
10.
Pinhão seed is an unconventional source of starch and the pines grow up in native forests of southern Latin America. In this study, pinhão starch was adjusted at 15, 20 and 25% moisture content and heated to 100, 110 and 120 °C for 1 h. A decrease in λ max (starch/iodine complex) was observed as a result of increase in temperature and moisture content of HMT. The ratio of crystalline to amorphous phase in pinhão starch was determined via Fourier transform infra red by taking 1045/1022 band ratio. A decrease in crystallinity occurred as a result of HMT. Polarised light microscopy indicated a loss of birefringence of starch granules under 120 °C at 25% moisture content. Granule size distribution was further confirmed via scanning electron microscopy which showed the HMT effects. These results increased the understanding on molecular and structural properties of HMT pinhão starch and broadened its food and nonfood industrial applications.  相似文献   
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