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   526500篇
  免费   7684篇
  国内免费   1468篇
电工技术   9568篇
综合类   526篇
化学工业   78835篇
金属工艺   19997篇
机械仪表   15215篇
建筑科学   12764篇
矿业工程   2274篇
能源动力   14567篇
轻工业   47183篇
水利工程   5229篇
石油天然气   9343篇
武器工业   37篇
无线电   60033篇
一般工业技术   102015篇
冶金工业   104144篇
原子能技术   10564篇
自动化技术   43358篇
  2022年   3172篇
  2021年   4901篇
  2020年   3480篇
  2019年   4565篇
  2018年   7818篇
  2017年   7624篇
  2016年   7943篇
  2015年   5572篇
  2014年   9258篇
  2013年   24165篇
  2012年   14670篇
  2011年   20205篇
  2010年   15844篇
  2009年   17723篇
  2008年   18132篇
  2007年   17839篇
  2006年   15557篇
  2005年   14251篇
  2004年   13637篇
  2003年   13437篇
  2002年   12663篇
  2001年   12866篇
  2000年   11907篇
  1999年   12637篇
  1998年   32984篇
  1997年   23001篇
  1996年   17507篇
  1995年   13092篇
  1994年   11344篇
  1993年   11022篇
  1992年   7934篇
  1991年   7430篇
  1990年   7278篇
  1989年   7028篇
  1988年   6485篇
  1987年   5779篇
  1986年   5672篇
  1985年   6287篇
  1984年   5918篇
  1983年   5181篇
  1982年   4922篇
  1981年   4985篇
  1980年   4722篇
  1979年   4626篇
  1978年   4430篇
  1977年   5369篇
  1976年   7023篇
  1975年   3810篇
  1974年   3562篇
  1973年   3677篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
This paper presents part of the work ComEd and Quanta Technology have performed to quantify the locational and temporal value of DER to avoid distribution grid upgrade investments. It focuses on the formulation of a robust and efficient algorithm for DER optimal dispatch on a distribution feeder to mitigate the violation of current and voltage limits using the allocated cost of capacity and locational marginal value of real and reactive DER injection/withdrawal.  相似文献   
2.
The proliferating need for sustainability intervention in food grain transportation planning is anchoring the attention of researchers in the interests of stakeholders and environment at large. Uncertainty associated with food grain supply further intensifies the problem steering the need for designing robust, cost-efficient and sustainable models. In line with this, this paper aims to develop a robust and sustainable intermodal transportation model to facilitate single type of food grain commodity shipments while considering procurement uncertainty, greenhouse gas emissions, and intentional hub disruption. The problem is designed as a mixed integer non-linear robust optimisation model on a hub and spoke network for evaluating near optimal shipment quantity, route selection and hub location decisions. The robust optimisation approach considers minimisation of total relative regret associated with total cost subject to several real-time constraints. A version of Particle Swarm Optimisation with Differential Evolution is proposed to tackle the resulting NP-hard problem. The model is tested with two other state-of the art meta-heuristics for small, medium, and large datasets subject to different procurement scenarios inspired from real time food grain operations in Indian context. Finally, the solution is evaluated with respect to total cost, model and solution robustness for all instances.  相似文献   
3.
4.
5.
6.
7.
8.
A layer-by-layer analysis of the structures, the phase compositions, and the defect substructures of differentially hardened rails has been carried by optical and transmission electron microscopy. It is found that the material volume of the rail head fillet is cooled faster than the volume located along the central axis.  相似文献   
9.
Lobster krill (Munida genus) represents an under‐valued crustacean frequently caught on European fishing banks. In this work, its sensory, microbiological and biochemical qualities were evaluated during chilled storage. Additionally, the effects of a prestorage antimelanosic treatment consisting of soaking in sodium metabisulphite (SMB) solutions at two different concentrations (0.25% and 0.75%) were also studied. SMB prestorage treatment provided lobster specimens that still exhibited acceptable sensory quality after 10 days of storage, while control specimens were unacceptable at that time. SMB treatment also resulted in a significant (P < 0.05) inhibition of microbial growth, mainly of Enterobacteriaceae, psychrotrophes and proteolytic bacteria. Low lipid oxidation levels were observed for all batches; however, a significantly higher (P < 0.05) retention of polyunsaturated fatty acids was found in SMB‐treated lobster, especially in the 0.75% SMB batch. The results presented here open the way to the potential commercialisation of currently under‐utilised lobster krill as a chilled product.  相似文献   
10.
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