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   179657篇
  免费   13974篇
  国内免费   7371篇
电工技术   9919篇
技术理论   9篇
综合类   10461篇
化学工业   28986篇
金属工艺   11089篇
机械仪表   11083篇
建筑科学   10766篇
矿业工程   4462篇
能源动力   4023篇
轻工业   10870篇
水利工程   3567篇
石油天然气   10093篇
武器工业   1280篇
无线电   18870篇
一般工业技术   27870篇
冶金工业   11403篇
原子能技术   5026篇
自动化技术   21225篇
  2024年   719篇
  2023年   2478篇
  2022年   5168篇
  2021年   6801篇
  2020年   5140篇
  2019年   4351篇
  2018年   5485篇
  2017年   5990篇
  2016年   5460篇
  2015年   6245篇
  2014年   8061篇
  2013年   9751篇
  2012年   10719篇
  2011年   11446篇
  2010年   9825篇
  2009年   9614篇
  2008年   9535篇
  2007年   9047篇
  2006年   8321篇
  2005年   7025篇
  2004年   5451篇
  2003年   5101篇
  2002年   5141篇
  2001年   4679篇
  2000年   4023篇
  1999年   3415篇
  1998年   2643篇
  1997年   2222篇
  1996年   1981篇
  1995年   1736篇
  1994年   1464篇
  1993年   1248篇
  1992年   1209篇
  1991年   1078篇
  1990年   1089篇
  1989年   1008篇
  1988年   892篇
  1987年   831篇
  1986年   758篇
  1985年   713篇
  1984年   700篇
  1981年   668篇
  1979年   738篇
  1978年   777篇
  1977年   739篇
  1976年   755篇
  1975年   713篇
  1974年   719篇
  1973年   723篇
  1972年   705篇
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
61.
62.
63.
Pleurotus eryngii, the second largest industrial cultivation mushroom in China, is usually cultivated on substrates mainly consisting of sawdust and corncob. In this study, experiments were performed to determine the effects of different carbon sources and C/N values on nonvolatile taste components of P. eryngii. The effects of different carbon sources on nonvolatile taste components levels revealed that sawdust was beneficial to high levels of crude protein, amino acids, 5′‐nucleotides and equivalent umami concentration, while corncob was beneficial to high contents of carbohydrate, polysaccharides and trehalose. At the similar C/N values, relatively higher sawdust content was beneficial to umami amino acid production, while relatively higher corncob content was beneficial to high contents of carbohydrate, polysaccharides and mannitol. Higher C/N value was beneficial to high levels of crude protein, amino acids, 5′‐nucleotides and equivalent umami concentration, while lower C/N value was beneficial to high contents of carbohydrate, polysaccharides and trehalose. These results provided information for P. eryngii fruit body industrial cultivation to obtain specific nonvolatile taste components with high levels.  相似文献   
64.
Colour remains one of the key factors in presenting an object and, consequently, has been widely applied in retrieval of images based on their visual contents. However, a colour appearance changes with the change of viewing surroundings, the phenomenon that has not been paid attention yet while performing colour‐based image retrieval. To comprehend this effect, in this article, a chromatic contrast model, CAMcc, is developed for the application of retrieval of colour intensive images, cementing the gap that most of existing colour models lack to fill by taking simultaneous colour contrast into account. Subsequently, the model is applied to the retrieval task on a collection of museum wallpapers of colour‐rich images. In comparison with current popular colour models including CIECAM02, HSI and RGB, with respect to both foreground and background colours, CAMcc appears to outperform the others with retrieved results being closer to query images. In addition, CAMcc focuses more on foreground colours, especially by maintaining the balance between both foreground and background colours, while the rest of existing models take on dominant colours that are perceived the most, usually background tones. Significantly, the contribution of the investigation lies in not only the improvement of the accuracy of colour‐based image retrieval but also the development of colour contrast model that warrants an important place in colour and computer vision theory, leading to deciphering the insight of this age‐old topic of chromatic contrast in colour science. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 361–373, 2015  相似文献   
65.
66.
67.
68.
69.
  Qing  Xu  Bin  Yu  Yang  Zhan  Wei  Zhao  Yu  Zheng  Jun  Ji  Jian 《Bulletin of Engineering Geology and the Environment》2021,80(8):6513-6525
Bulletin of Engineering Geology and the Environment - Many uncertainties exist in pile-stabilized slopes which make their design substantially complicated. In this paper, a first-order reliability...  相似文献   
70.
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