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   495004篇
  免费   8433篇
  国内免费   1426篇
电工技术   8534篇
综合类   358篇
化学工业   78663篇
金属工艺   20292篇
机械仪表   16604篇
建筑科学   11979篇
矿业工程   2874篇
能源动力   13086篇
轻工业   43262篇
水利工程   5254篇
石油天然气   10091篇
武器工业   22篇
无线电   57171篇
一般工业技术   98798篇
冶金工业   86131篇
原子能技术   11597篇
自动化技术   40147篇
  2021年   4856篇
  2020年   3634篇
  2019年   4421篇
  2018年   7136篇
  2017年   7190篇
  2016年   7877篇
  2015年   5213篇
  2014年   8736篇
  2013年   22477篇
  2012年   14028篇
  2011年   18642篇
  2010年   14808篇
  2009年   16610篇
  2008年   16762篇
  2007年   16070篇
  2006年   14190篇
  2005年   13048篇
  2004年   12265篇
  2003年   11932篇
  2002年   11540篇
  2001年   11237篇
  2000年   10744篇
  1999年   10935篇
  1998年   25617篇
  1997年   18638篇
  1996年   14618篇
  1995年   10854篇
  1994年   9865篇
  1993年   9535篇
  1992年   7339篇
  1991年   7169篇
  1990年   6833篇
  1989年   6904篇
  1988年   6695篇
  1987年   5688篇
  1986年   5594篇
  1985年   6460篇
  1984年   6080篇
  1983年   5562篇
  1982年   5107篇
  1981年   5319篇
  1980年   5051篇
  1979年   5056篇
  1978年   5141篇
  1977年   5887篇
  1976年   7681篇
  1975年   4605篇
  1974年   4391篇
  1973年   4418篇
  1972年   3784篇
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
1.
2.
Multimedia Tools and Applications - Remote Sensing categorical signature classification has gained significant implications on spatial resolution image analysis due to differences in the...  相似文献   
3.
4.
5.
Theoretical Foundations of Chemical Engineering - On the basis of the classic concepts of the theory of solid-phase combustion, for the first time, a model with a detailed scheme of chemical...  相似文献   
6.
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.
A set of novel hydrazone derivatives were synthesized and analyzed for their biological activities. The compounds were tested for their inhibitory effect on the phosphorylating activity of the protein kinase CK2, and their antioxidant activity was also determined in three commonly used assays. The hydrazones were evaluated for their radical scavenging against the DPPH, ABTS and peroxyl radicals. Several compounds have been identified as good antioxidants as well as potent protein kinase CK2 inhibitors. Most hydrazones containing a 4-N(CH3)2 residue or perfluorinated phenyl rings showed high activity in the radical-scavenging assays and possess nanomolar IC50 values in the kinase assays.  相似文献   
10.
Journal of Communications Technology and Electronics - A statistical study of the effectiveness of the non-threshold search procedure for a noise-like phase-shift keyed signal by the delay time is...  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