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   58899篇
  免费   15767篇
  国内免费   906篇
电工技术   1899篇
技术理论   2篇
综合类   1369篇
化学工业   20475篇
金属工艺   1477篇
机械仪表   2071篇
建筑科学   3630篇
矿业工程   764篇
能源动力   1377篇
轻工业   8207篇
水利工程   634篇
石油天然气   1547篇
武器工业   121篇
无线电   9015篇
一般工业技术   13862篇
冶金工业   1721篇
原子能技术   244篇
自动化技术   7157篇
  2024年   105篇
  2023年   433篇
  2022年   639篇
  2021年   1073篇
  2020年   2124篇
  2019年   3726篇
  2018年   3704篇
  2017年   4120篇
  2016年   4461篇
  2015年   4724篇
  2014年   4927篇
  2013年   6142篇
  2012年   4018篇
  2011年   3690篇
  2010年   3870篇
  2009年   3617篇
  2008年   3151篇
  2007年   2967篇
  2006年   2802篇
  2005年   2458篇
  2004年   1980篇
  2003年   1868篇
  2002年   1766篇
  2001年   1584篇
  2000年   1515篇
  1999年   1048篇
  1998年   566篇
  1997年   452篇
  1996年   401篇
  1995年   351篇
  1994年   266篇
  1993年   172篇
  1992年   146篇
  1991年   136篇
  1990年   103篇
  1989年   86篇
  1988年   62篇
  1987年   37篇
  1986年   46篇
  1985年   25篇
  1984年   24篇
  1983年   23篇
  1982年   19篇
  1981年   13篇
  1980年   17篇
  1979年   10篇
  1976年   15篇
  1973年   8篇
  1971年   7篇
  1970年   7篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
Various products, including foods and pharmaceuticals, are sensitive to temperature fluctuations. Thus, temperature monitoring during production, transportation, and storage is critical. Facile indicators are required to monitor temperature conditions via color changes in real time. This study aimed to prepare and apply thiol-functionalized covalent organic frameworks (COFs) as a novel indicator for monitoring thermal history and temperature abuse. The COFs underwent obvious color changes from bright yellow to purple after exposure to different temperatures for varying durations. The reaction kinetics are analyzed under isothermal conditions, which reveal that the order of reaction rates is k−20°C < k4°C < k20°C < k35°C < k55°C. The activation energy (Ea) of the COFs is calculated using the Arrhenius equation as 50.71 kJ moL−1. The COFs are capable of sensitive color changes and offer a broad temperature tracking range, thereby demonstrating their application potential for the monitoring of temperature and time exposure history during production, transportation, and storage. This excellent performance thermal history indicator also shows promise for expanding the application field of COFs.  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.
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   
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