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   302341篇
  免费   4611篇
  国内免费   825篇
电工技术   5348篇
综合类   216篇
化学工业   48889篇
金属工艺   12347篇
机械仪表   8960篇
建筑科学   7654篇
矿业工程   1939篇
能源动力   6985篇
轻工业   27923篇
水利工程   3293篇
石油天然气   7107篇
武器工业   16篇
无线电   32414篇
一般工业技术   60989篇
冶金工业   51727篇
原子能技术   7643篇
自动化技术   24327篇
  2021年   2442篇
  2019年   2228篇
  2018年   4224篇
  2017年   4172篇
  2016年   4548篇
  2015年   2977篇
  2014年   4903篇
  2013年   13289篇
  2012年   7616篇
  2011年   10158篇
  2010年   8343篇
  2009年   9364篇
  2008年   9733篇
  2007年   9591篇
  2006年   8404篇
  2005年   7770篇
  2004年   7177篇
  2003年   6934篇
  2002年   7016篇
  2001年   6799篇
  2000年   6447篇
  1999年   6426篇
  1998年   14911篇
  1997年   11209篇
  1996年   8707篇
  1995年   6663篇
  1994年   6038篇
  1993年   5883篇
  1992年   4578篇
  1991年   4519篇
  1990年   4350篇
  1989年   4356篇
  1988年   4314篇
  1987年   3661篇
  1986年   3642篇
  1985年   4285篇
  1984年   4092篇
  1983年   3701篇
  1982年   3504篇
  1981年   3658篇
  1980年   3502篇
  1979年   3428篇
  1978年   3514篇
  1977年   3983篇
  1976年   5089篇
  1975年   3231篇
  1974年   3054篇
  1973年   3080篇
  1972年   2672篇
  1971年   2498篇
排序方式: 共有10000条查询结果,搜索用时 31 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.
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   
4.
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   
5.
Multimedia Tools and Applications - Endometriosis is a common gynecologic condition typically treated via laparoscopic surgery. Its visual versatility makes it hard to identify for non-specialized...  相似文献   
6.
Forschung im Ingenieurwesen - Das Arbeitsmittel in Wärmepumpen unterliegt einer Vielzahl von Anforderungen, welche für einen effizienten und sicheren Betrieb eingehalten werden...  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