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   526904篇
  免费   7780篇
  国内免费   1483篇
电工技术   9587篇
综合类   530篇
化学工业   79117篇
金属工艺   20013篇
机械仪表   15264篇
建筑科学   12745篇
矿业工程   2274篇
能源动力   14844篇
轻工业   47246篇
水利工程   5231篇
石油天然气   9375篇
武器工业   37篇
无线电   60098篇
一般工业技术   102105篇
冶金工业   103617篇
原子能技术   10570篇
自动化技术   43514篇
  2022年   3248篇
  2021年   5022篇
  2020年   3565篇
  2019年   4637篇
  2018年   7944篇
  2017年   7706篇
  2016年   8056篇
  2015年   5630篇
  2014年   9341篇
  2013年   24247篇
  2012年   14745篇
  2011年   20290篇
  2010年   15887篇
  2009年   17797篇
  2008年   18164篇
  2007年   17849篇
  2006年   15565篇
  2005年   14236篇
  2004年   13646篇
  2003年   13442篇
  2002年   12659篇
  2001年   12848篇
  2000年   11885篇
  1999年   12613篇
  1998年   32845篇
  1997年   22921篇
  1996年   17467篇
  1995年   13064篇
  1994年   11299篇
  1993年   10992篇
  1992年   7921篇
  1991年   7429篇
  1990年   7266篇
  1989年   7023篇
  1988年   6475篇
  1987年   5774篇
  1986年   5659篇
  1985年   6277篇
  1984年   5908篇
  1983年   5173篇
  1982年   4909篇
  1981年   4973篇
  1980年   4710篇
  1979年   4612篇
  1978年   4409篇
  1977年   5339篇
  1976年   6976篇
  1975年   3798篇
  1974年   3553篇
  1973年   3674篇
排序方式: 共有10000条查询结果,搜索用时 0 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