首页 | 官方网站   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   466117篇
  免费   7062篇
  国内免费   1348篇
工业技术   474527篇
  2021年   4043篇
  2019年   3761篇
  2018年   6443篇
  2017年   6468篇
  2016年   6935篇
  2015年   4567篇
  2014年   7661篇
  2013年   20942篇
  2012年   12325篇
  2011年   16673篇
  2010年   13360篇
  2009年   15139篇
  2008年   15301篇
  2007年   14969篇
  2006年   13091篇
  2005年   12132篇
  2004年   11436篇
  2003年   11089篇
  2002年   10866篇
  2001年   10682篇
  2000年   10258篇
  1999年   10500篇
  1998年   24848篇
  1997年   18062篇
  1996年   13671篇
  1995年   10496篇
  1994年   9515篇
  1993年   9211篇
  1992年   7070篇
  1991年   6946篇
  1990年   6593篇
  1989年   6649篇
  1988年   6474篇
  1987年   5503篇
  1986年   5469篇
  1985年   6299篇
  1984年   5934篇
  1983年   5436篇
  1982年   5011篇
  1981年   5225篇
  1980年   4978篇
  1979年   4961篇
  1978年   5054篇
  1977年   5795篇
  1976年   7589篇
  1975年   4545篇
  1974年   4327篇
  1973年   4367篇
  1972年   3743篇
  1971年   3420篇
排序方式: 共有10000条查询结果,搜索用时 343 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.
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   
4.
5.
Food Science and Biotechnology - Various hilling materials (rice hulls, pine sawdust, and perlite) were compared to produce sprout vegetables using beach silvertop (Glehnia littoralis Fr. Schm. ex...  相似文献   
6.
International Journal of Information Security - Machine learning techniques have been widely used and shown remarkable performance in various fields. Along with the widespread utilization of...  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.
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-23

京公网安备 11010802026262号