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   526602篇
  免费   7730篇
  国内免费   1473篇
电工技术   9591篇
综合类   532篇
化学工业   79232篇
金属工艺   20011篇
机械仪表   15230篇
建筑科学   12782篇
矿业工程   2278篇
能源动力   14559篇
轻工业   47173篇
水利工程   5224篇
石油天然气   9334篇
武器工业   37篇
无线电   60030篇
一般工业技术   102078篇
冶金工业   103597篇
原子能技术   10582篇
自动化技术   43535篇
  2022年   3193篇
  2021年   4949篇
  2020年   3507篇
  2019年   4586篇
  2018年   7839篇
  2017年   7639篇
  2016年   7998篇
  2015年   5606篇
  2014年   9298篇
  2013年   24150篇
  2012年   14729篇
  2011年   20270篇
  2010年   15903篇
  2009年   17779篇
  2008年   18189篇
  2007年   17858篇
  2006年   15606篇
  2005年   14274篇
  2004年   13671篇
  2003年   13444篇
  2002年   12671篇
  2001年   12865篇
  2000年   11899篇
  1999年   12629篇
  1998年   32847篇
  1997年   22926篇
  1996年   17469篇
  1995年   13055篇
  1994年   11305篇
  1993年   10991篇
  1992年   7935篇
  1991年   7438篇
  1990年   7276篇
  1989年   7028篇
  1988年   6478篇
  1987年   5780篇
  1986年   5661篇
  1985年   6277篇
  1984年   5909篇
  1983年   5181篇
  1982年   4912篇
  1981年   4977篇
  1980年   4718篇
  1979年   4620篇
  1978年   4417篇
  1977年   5344篇
  1976年   6979篇
  1975年   3810篇
  1974年   3566篇
  1973年   3671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.
Wu  Li  Li  Jing  Fu  Caixia  Kühn  Bernd  Wang  Xiaolin 《Magma (New York, N.Y.)》2019,32(4):501-509
Magnetic Resonance Materials in Physics, Biology and Medicine - To investigate the value of using diffusion-weighted imaging (DWI) and intravoxel incoherent motion DWI (IVIM-DWI) to assess the...  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