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   44080篇
  免费   4337篇
  国内免费   2196篇
电工技术   2877篇
技术理论   3篇
综合类   2862篇
化学工业   7151篇
金属工艺   2473篇
机械仪表   2740篇
建筑科学   3305篇
矿业工程   1260篇
能源动力   1242篇
轻工业   2905篇
水利工程   893篇
石油天然气   2833篇
武器工业   425篇
无线电   5322篇
一般工业技术   5215篇
冶金工业   1955篇
原子能技术   447篇
自动化技术   6705篇
  2024年   277篇
  2023年   910篇
  2022年   1738篇
  2021年   2354篇
  2020年   1730篇
  2019年   1322篇
  2018年   1551篇
  2017年   1602篇
  2016年   1356篇
  2015年   1921篇
  2014年   2417篇
  2013年   2684篇
  2012年   3062篇
  2011年   3260篇
  2010年   2883篇
  2009年   2430篇
  2008年   2513篇
  2007年   2260篇
  2006年   2174篇
  2005年   1896篇
  2004年   1250篇
  2003年   1044篇
  2002年   990篇
  2001年   849篇
  2000年   840篇
  1999年   1022篇
  1998年   787篇
  1997年   623篇
  1996年   587篇
  1995年   491篇
  1994年   403篇
  1993年   269篇
  1992年   246篇
  1991年   182篇
  1990年   130篇
  1989年   106篇
  1988年   88篇
  1987年   53篇
  1986年   47篇
  1985年   37篇
  1984年   31篇
  1983年   28篇
  1982年   25篇
  1981年   23篇
  1980年   26篇
  1979年   12篇
  1978年   12篇
  1977年   11篇
  1976年   8篇
  1973年   12篇
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
91.
92.
Large holes are unavoidably generated in depth image based rendering (DIBR) using a single color image and its associated depth map. Such holes are mainly caused by disocclusion, which occurs around the sharp depth discontinuities in the depth map. We propose a divide-and-conquer hole-filling method which refines the background depth pixels around the sharp depth discontinuities to address the disocclusion problem. Firstly, the disocclusion region is detected according to the degree of depth discontinuity, and the target area is marked as a binary mask. Then, the depth pixels located in the target area are modified by a linear interpolation process, whose pixel values decrease from the foreground depth value to the background depth value. Finally, in order to remove the isolated depth pixels, median filtering is adopted to refine the depth map. In these ways, disocclusion regions in the synthesized view are divided into several small holes after DIBR, and are easily filled by image inpainting. Experimental results demonstrate that the proposed method can effectively improve the quality of the synthesized view subjectively and objectively.  相似文献   
93.
It is considered to be the most suitable solution for large scale elections to design an electronic voting scheme using blind signatures and anonymous channels. Based on this framework, Okamoto first proposed a receipt-free voting scheme [30] for large scale elections. However, in the following paper, Okamoto [31] proved that the scheme [30] was not receipt-free and presented two improved schemes. One scheme requires the help of the parameter registration committee and the other needs a stronger physical assumption of the voting booth. In this paper, we utilize the double-trapdoor commitment to propose a new receipt-free voting scheme based on blind signatures for large scale elections. Neither the parameter registration committee nor the voting booth is required in our scheme. We also present a more efficient zero-knowledge proof for secret permutation. Therefore, our scheme is much more efficient than Okamoto’s schemes [30] and [31] with the weaker physical assumptions. Moreover, we prove that our scheme can achieve the desired security properties.  相似文献   
94.
随着Internet的快速发展,网络在综合船桥系统中得到了广泛的应用。在享受网络带来的便利的同时,它的各种弊端也日益显露,如网上数据传输的完整性等问题。为了很好地解决这一问题,将RSA数字签名和数字摘要应用于综合船桥系统中。在保证数据安全传输的同时,很好地验证了数据的完整性,同时完成了发送方的身份验证。  相似文献   
95.
对信息需求的准确分析是建立设计管理系统的基础。传统的分析方法从过程与人,过程与信息的角度出发综合分析整个机构的信息需求,但是,这种方法没有示识产生和使用信息的范围。为此,;补充分析了信息的机构和项目属性,并通过建立三维组织机构模型;机械、人员和任务模型,有效控制基本的信息存取。  相似文献   
96.
自然主义对许多艺术门类都产生过深刻影响,在设计领域中,以自然主义为主要特点的新艺术运动曾在一个重大的设计变革时期——工业革命后风靡各国,然而却又在短短十多年后沉寂下来,本文主要分析自然主义为什么会在设计史的重要阶段产生如此特别的表现。  相似文献   
97.
ZnO-Bi2O3-based ceramic varistors containing up to 2500 p.p.m. Ag2O were prepared by the mixed oxide route. The products were characterized in terms of current-voltage (I–V) behaviour, capacitance-voltage (C-V) behaviour and d.c. degradation behaviour. Additions of silver did not significantly affect ZnO grain growth or sintered density, but decreased the non-linearity exponent, a, and increased the breakdown voltage. Silver-doped specimens exhibited an unusual d.c. degradation behaviour, with the leakage current initially decreasing before reaching a stable value. For doping levels 500 p.p.m. Ag2O, the change in breakdown voltage was positive for both forward and reverse directions. Silver doping appeared to increase the Schottky barrier height under conditions of continuous d.c. stress and improve the degradation behaviour. The optimum levels of Ag2O addition were in the range 500–1000 p.p.m.  相似文献   
98.
We show that it is possible to collect data that are useful for collaborative filtering (CF) using an autonomous Web spider. In CF, entities are recommended to a new user based on the stated preferences of other, similar users. We describe a CF spider that collects from the Web lists of semantically related entities. These lists can then be used by existing CF algorithms by encoding them as ‘pseudo-users'. Importantly, the spider can collect useful data without pre-programmed knowledge about the format of particular pages or particular sites. Instead, the CF spider uses commercial Web-search engines to find pages likely to contain lists in the domain of interest, and then applies previously proposed heuristics to extract lists from these pages. We show that data collected by this spider are nearly as effective for CF as data collected from real users, and more effective than data collected by two plausible hand-programmed spiders. In some cases, autonomously spidered data can also be combined with actual user data to improve performance.  相似文献   
99.
100.
混合碳四的来料加工   总被引:2,自引:0,他引:2  
范仲明 《乙烯工业》2004,16(2):49-53
分析了混合碳四中3种关键组分超标对丁二烯生产的不利影响,提出了外加工混合碳四过程中具体的应对措施和解决方案。  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