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   550878篇
  免费   8989篇
  国内免费   1510篇
电工技术   9755篇
综合类   559篇
化学工业   84594篇
金属工艺   20434篇
机械仪表   15654篇
建筑科学   13526篇
矿业工程   2333篇
能源动力   15337篇
轻工业   51587篇
水利工程   5458篇
石油天然气   9451篇
武器工业   39篇
无线电   61123篇
一般工业技术   105276篇
冶金工业   108403篇
原子能技术   10729篇
自动化技术   47119篇
  2022年   3797篇
  2021年   5727篇
  2020年   4060篇
  2019年   5268篇
  2018年   8674篇
  2017年   8460篇
  2016年   8890篇
  2015年   6307篇
  2014年   10223篇
  2013年   25975篇
  2012年   16085篇
  2011年   21766篇
  2010年   17102篇
  2009年   18941篇
  2008年   19210篇
  2007年   18761篇
  2006年   16284篇
  2005年   14876篇
  2004年   14237篇
  2003年   13958篇
  2002年   13144篇
  2001年   13150篇
  2000年   12174篇
  1999年   12935篇
  1998年   34380篇
  1997年   23889篇
  1996年   18189篇
  1995年   13442篇
  1994年   11619篇
  1993年   11341篇
  1992年   8042篇
  1991年   7526篇
  1990年   7356篇
  1989年   7138篇
  1988年   6563篇
  1987年   5847篇
  1986年   5736篇
  1985年   6380篇
  1984年   5969篇
  1983年   5227篇
  1982年   4980篇
  1981年   5041篇
  1980年   4783篇
  1979年   4649篇
  1978年   4450篇
  1977年   5469篇
  1976年   7235篇
  1975年   3828篇
  1974年   3568篇
  1973年   3695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.
In this study, amaranth flour was used as an ingredient to prepare gluten-free cookies. The production process and attributes of amaranth cookies were characterised, and the potential use of amaranth flour as a functional ingredient was analysed. Cookies exhibited a non-uniform reddish brown colour and a cookie factor ratio of 4.5 ± 0.6. Storage studies indicated that after 3 weeks at room temperature cookies presented slight variations in the texture. Simulated gastrointestinal digestion of this product was able to release peptides capable of exerting potential antithrombotic and antihypertensive activities, IC50 values of 0.22 ± 0.04 and 0.23 ± 0.03 mg mL−1 protein, respectively. This work demonstrates for the first time that food made with amaranth flour exerts potential antithrombotic and antihypertensive activity. In conclusion, these amaranth cookies could be an alternative way of incorporating potentially health beneficial products for people who choose a conscious diet, including coeliac or vegan consumers.  相似文献   
3.
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   
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