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   313803篇
  免费   5334篇
  国内免费   872篇
电工技术   5547篇
综合类   273篇
化学工业   51656篇
金属工艺   12678篇
机械仪表   9296篇
建筑科学   8064篇
矿业工程   1993篇
能源动力   7384篇
轻工业   29410篇
水利工程   3384篇
石油天然气   7216篇
武器工业   29篇
无线电   33042篇
一般工业技术   63155篇
冶金工业   52922篇
原子能技术   7749篇
自动化技术   26211篇
  2021年   2785篇
  2019年   2494篇
  2018年   4644篇
  2017年   4623篇
  2016年   5052篇
  2015年   3321篇
  2014年   5456篇
  2013年   14186篇
  2012年   8211篇
  2011年   10897篇
  2010年   8896篇
  2009年   9919篇
  2008年   10255篇
  2007年   10051篇
  2006年   8766篇
  2005年   8047篇
  2004年   7467篇
  2003年   7215篇
  2002年   7318篇
  2001年   6982篇
  2000年   6622篇
  1999年   6574篇
  1998年   15205篇
  1997年   11484篇
  1996年   8895篇
  1995年   6805篇
  1994年   6162篇
  1993年   6029篇
  1992年   4656篇
  1991年   4588篇
  1990年   4407篇
  1989年   4423篇
  1988年   4362篇
  1987年   3710篇
  1986年   3693篇
  1985年   4363篇
  1984年   4148篇
  1983年   3769篇
  1982年   3577篇
  1981年   3724篇
  1980年   3559篇
  1979年   3492篇
  1978年   3560篇
  1977年   4070篇
  1976年   5207篇
  1975年   3275篇
  1974年   3111篇
  1973年   3120篇
  1972年   2697篇
  1971年   2523篇
排序方式: 共有10000条查询结果,搜索用时 15 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.
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   
5.
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   
6.
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   
7.
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   
8.
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   
9.
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   
10.
This study investigates the behavior of fruit and vegetable samples during drying. The experimental data are fitted to several different thin-layer drying models. Regression analysis is used to determine model parameters, while statistical indicators serve to evaluate the goodness of fit. The power function model gives the best fit for all examined samples. Based on this model, different drying and heat storage technologies can be combined to ensure that the required residual moisture content of an agricultural product is reached. It is demonstrated on the case of a specific Togolese processing plant that under favorable conditions, fossil fuel consumption can be decreased by 33 %.  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