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   813920篇
  免费   11914篇
  国内免费   2451篇
电工技术   14825篇
综合类   838篇
化学工业   121963篇
金属工艺   29777篇
机械仪表   23159篇
建筑科学   21396篇
矿业工程   2939篇
能源动力   22242篇
轻工业   75152篇
水利工程   7363篇
石油天然气   10708篇
武器工业   49篇
无线电   97258篇
一般工业技术   153400篇
冶金工业   160427篇
原子能技术   14255篇
自动化技术   72534篇
  2021年   6675篇
  2020年   4837篇
  2019年   6136篇
  2018年   10317篇
  2017年   10127篇
  2016年   10739篇
  2015年   7881篇
  2014年   12936篇
  2013年   37946篇
  2012年   21114篇
  2011年   29592篇
  2010年   23195篇
  2009年   26093篇
  2008年   27145篇
  2007年   27059篇
  2006年   23952篇
  2005年   22030篇
  2004年   21231篇
  2003年   20926篇
  2002年   20007篇
  2001年   19988篇
  2000年   18571篇
  1999年   19808篇
  1998年   49622篇
  1997年   35233篇
  1996年   27213篇
  1995年   20801篇
  1994年   18256篇
  1993年   17816篇
  1992年   12887篇
  1991年   12276篇
  1990年   11812篇
  1989年   11471篇
  1988年   10808篇
  1987年   9403篇
  1986年   9250篇
  1985年   10810篇
  1984年   10103篇
  1983年   8871篇
  1982年   8311篇
  1981年   8389篇
  1980年   7942篇
  1979年   7739篇
  1978年   7342篇
  1977年   8906篇
  1976年   11985篇
  1975年   6293篇
  1974年   5992篇
  1973年   5982篇
  1972年   4874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.
9.
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   
10.
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   
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