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   735051篇
  免费   10553篇
  国内免费   2279篇
电工技术   13468篇
综合类   1287篇
化学工业   109248篇
金属工艺   27200篇
机械仪表   21247篇
建筑科学   18171篇
矿业工程   3324篇
能源动力   20154篇
轻工业   62873篇
水利工程   7249篇
石油天然气   11462篇
武器工业   49篇
无线电   84982篇
一般工业技术   139961篇
冶金工业   149260篇
原子能技术   14032篇
自动化技术   63916篇
  2022年   4297篇
  2021年   6498篇
  2020年   4688篇
  2019年   5955篇
  2018年   10472篇
  2017年   10476篇
  2016年   11314篇
  2015年   7839篇
  2014年   12336篇
  2013年   32999篇
  2012年   20576篇
  2011年   28104篇
  2010年   21222篇
  2009年   23977篇
  2008年   24454篇
  2007年   24008篇
  2006年   21152篇
  2005年   21466篇
  2004年   20242篇
  2003年   19659篇
  2002年   17675篇
  2001年   17966篇
  2000年   16287篇
  1999年   17348篇
  1998年   46813篇
  1997年   32490篇
  1996年   24765篇
  1995年   18403篇
  1994年   15984篇
  1993年   15788篇
  1992年   11032篇
  1991年   10537篇
  1990年   10270篇
  1989年   9847篇
  1988年   9298篇
  1987年   8168篇
  1986年   8001篇
  1985年   8829篇
  1984年   8172篇
  1983年   7443篇
  1982年   7009篇
  1981年   7025篇
  1980年   6768篇
  1979年   6411篇
  1978年   6120篇
  1977年   7802篇
  1976年   10696篇
  1975年   5220篇
  1974年   4927篇
  1973年   4972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