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   580215篇
  免费   9187篇
  国内免费   1723篇
电工技术   10360篇
综合类   1182篇
化学工业   87255篇
金属工艺   20927篇
机械仪表   16630篇
建筑科学   15095篇
矿业工程   2829篇
能源动力   15538篇
轻工业   50399篇
水利工程   5850篇
石油天然气   9438篇
武器工业   42篇
无线电   62862篇
一般工业技术   108886篇
冶金工业   120605篇
原子能技术   10838篇
自动化技术   52389篇
  2022年   3531篇
  2021年   5424篇
  2020年   3753篇
  2019年   4875篇
  2018年   9029篇
  2017年   8919篇
  2016年   9512篇
  2015年   6773篇
  2014年   10239篇
  2013年   25761篇
  2012年   17340篇
  2011年   23616篇
  2010年   17313篇
  2009年   19252篇
  2008年   19689篇
  2007年   19204篇
  2006年   16808篇
  2005年   18609篇
  2004年   17031篇
  2003年   16118篇
  2002年   13974篇
  2001年   13842篇
  2000年   12421篇
  1999年   13355篇
  1998年   37075篇
  1997年   25644篇
  1996年   19375篇
  1995年   14267篇
  1994年   12263篇
  1993年   11983篇
  1992年   8297篇
  1991年   7817篇
  1990年   7637篇
  1989年   7412篇
  1988年   6829篇
  1987年   6080篇
  1986年   5961篇
  1985年   6606篇
  1984年   6133篇
  1983年   5389篇
  1982年   5142篇
  1981年   5285篇
  1980年   4973篇
  1979年   4778篇
  1978年   4607篇
  1977年   5948篇
  1976年   8164篇
  1975年   3987篇
  1974年   3675篇
  1973年   3768篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
In this paper, we present a novel memory access reduction scheme (MARS) for two-dimension fast cosine transform (2-D FCT). It targets programmable DSPs with high memory-access latency. It reduces the number of memory accesses by: 1) reducing the number of weighting factors and 2) combining butterflies in vector-radix 2-D FCT pruning diagram from two stages to one stage with an efficient structure. Hardware platform based on general purpose processor is used to verify the effectiveness of the proposed method for vector-radix 2-D FCT pruning implementation. Experimental results validate the benefits of the proposed method with reduced memory access, less clock cycle and fewer memory space compared with the conventional implementation.  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