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   695360篇
  免费   9837篇
  国内免费   2306篇
电工技术   12960篇
综合类   718篇
化学工业   104323篇
金属工艺   27859篇
机械仪表   20030篇
建筑科学   17407篇
矿业工程   2660篇
能源动力   18800篇
轻工业   63748篇
水利工程   6486篇
石油天然气   10256篇
武器工业   40篇
无线电   80876篇
一般工业技术   132057篇
冶金工业   138452篇
原子能技术   13085篇
自动化技术   57746篇
  2021年   5847篇
  2020年   4242篇
  2019年   5499篇
  2018年   9245篇
  2017年   8988篇
  2016年   9494篇
  2015年   6801篇
  2014年   11198篇
  2013年   31715篇
  2012年   18038篇
  2011年   25098篇
  2010年   19891篇
  2009年   22238篇
  2008年   23122篇
  2007年   22855篇
  2006年   20250篇
  2005年   18595篇
  2004年   17812篇
  2003年   17598篇
  2002年   16986篇
  2001年   17040篇
  2000年   15779篇
  1999年   16919篇
  1998年   43472篇
  1997年   30543篇
  1996年   23549篇
  1995年   17632篇
  1994年   15344篇
  1993年   15002篇
  1992年   10808篇
  1991年   10352篇
  1990年   9845篇
  1989年   9582篇
  1988年   9077篇
  1987年   7905篇
  1986年   7840篇
  1985年   8889篇
  1984年   8287篇
  1983年   7323篇
  1982年   6901篇
  1981年   7017篇
  1980年   6635篇
  1979年   6392篇
  1978年   6167篇
  1977年   7606篇
  1976年   10384篇
  1975年   5372篇
  1974年   5040篇
  1973年   5137篇
  1972年   4230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