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   532589篇
  免费   10151篇
  国内免费   2581篇
电工技术   10336篇
技术理论   5篇
综合类   2091篇
化学工业   80160篇
金属工艺   20259篇
机械仪表   15966篇
建筑科学   13294篇
矿业工程   3032篇
能源动力   11935篇
轻工业   48492篇
水利工程   5716篇
石油天然气   9134篇
武器工业   320篇
无线电   58840篇
一般工业技术   97304篇
冶金工业   108610篇
原子能技术   10070篇
自动化技术   49757篇
  2021年   4734篇
  2020年   3470篇
  2019年   4382篇
  2018年   7656篇
  2017年   7803篇
  2016年   8679篇
  2015年   6249篇
  2014年   9118篇
  2013年   23239篇
  2012年   16155篇
  2011年   20780篇
  2010年   15533篇
  2009年   16782篇
  2008年   17977篇
  2007年   18025篇
  2006年   15961篇
  2005年   16724篇
  2004年   15076篇
  2003年   14074篇
  2002年   12647篇
  2001年   12541篇
  2000年   11512篇
  1999年   11791篇
  1998年   30919篇
  1997年   22035篇
  1996年   16749篇
  1995年   12365篇
  1994年   10920篇
  1993年   10824篇
  1992年   7941篇
  1991年   7444篇
  1990年   7403篇
  1989年   7060篇
  1988年   6769篇
  1987年   5880篇
  1986年   5759篇
  1985年   6644篇
  1984年   6214篇
  1983年   5680篇
  1982年   5267篇
  1981年   5594篇
  1980年   5274篇
  1979年   5136篇
  1978年   4935篇
  1977年   6049篇
  1976年   8272篇
  1975年   4475篇
  1974年   4288篇
  1973年   4332篇
  1972年   3573篇
排序方式: 共有10000条查询结果,搜索用时 771 毫秒
1.
2.
3.
Journal of Communications Technology and Electronics - A quantitative comparison of the spectral characteristics of the human visual system and matrix photodetectors is carried out. Criteria for a...  相似文献   
4.
5.
Virtual Reality - It is generally accepted that natural environments reduce stress and improve mood. Since access to natural environments is sometimes limited, virtual natural environments,...  相似文献   
6.
Refractories and Industrial Ceramics - The paper introduces a promising technology for utilizing a traditional scheme for implementing a flow-through micro-arc oxidation method to restore localized...  相似文献   
7.
Engineering new glass compositions have experienced a sturdy tendency to move forward from (educated) trial-and-error to data- and simulation-driven strategies. In this work, we developed a computer program that combines data-driven predictive models (in this case, neural networks) with a genetic algorithm to design glass compositions with desired combinations of properties. First, we induced predictive models for the glass transition temperature (Tg) using a dataset of 45,302 compositions with 39 different chemical elements, and for the refractive index (nd) using a dataset of 41,225 compositions with 38 different chemical elements. Then, we searched for relevant glass compositions using a genetic algorithm informed by a design trend of glasses having high nd (1.7 or more) and low Tg (500 °C or less). Two candidate compositions suggested by the combined algorithms were selected and produced in the laboratory. These compositions are significantly different from those in the datasets used to induce the predictive models, showing that the used method is indeed capable of exploration. Both glasses met the constraints of the work, which supports the proposed framework. Therefore, this new tool can be immediately used for accelerating the design of new glasses. These results are a stepping stone in the pathway of machine learning-guided design of novel glasses.  相似文献   
8.
Journal of Chemical Ecology - Biocontrol agents such as parasitic wasps use long-range volatiles and host-associated cues from lower trophic levels to find their hosts. However, this chemical...  相似文献   
9.
While protein medications are promising for treatment of cancer and autoimmune diseases, challenges persist in terms of development and injection stability of high-concentration formulations. Here, the extensional flow properties of protein-excipient solutions are examined via dripping-onto-substrate extensional rheology, using a model ovalbumin (OVA) protein and biocompatible excipients polysorbate 20 (PS20) and 80 (PS80). Despite similar PS structures, differences in extensional flow are observed based on PS identity in two regimes: at moderate total concentrations where surface tension differences drive changes in extensional flow behavior, and at small PS:OVA ratios, which impact the onset of weakly elastic flow behavior. Undesirable elasticity is observed in ultra-concentrated formulations, independent of PS identity; higher PS contents are required to observe these effects than in analogous polymeric excipient solutions. These studies reveal novel extensional flow behaviors in protein-excipient solutions, and provide a straightforward methodology for assessing the extensional flow stability of new protein-excipient formulations.  相似文献   
10.
Water Resources Management - The water evaluation and planning (WEAP) approach and the invasive weed optimization algorithm (IWOA) are herein employed to determine the optimal operating policies in...  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