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   133870篇
  免费   6931篇
  国内免费   5088篇
化学   48924篇
晶体学   1125篇
力学   8764篇
综合类   241篇
数学   35819篇
物理学   28180篇
无线电   22836篇
  2024年   169篇
  2023年   1146篇
  2022年   1362篇
  2021年   1803篇
  2020年   1788篇
  2019年   1600篇
  2018年   12879篇
  2017年   12477篇
  2016年   8628篇
  2015年   2897篇
  2014年   2804篇
  2013年   3490篇
  2012年   7982篇
  2011年   15181篇
  2010年   9408篇
  2009年   9348篇
  2008年   9990篇
  2007年   12086篇
  2006年   2754篇
  2005年   3761篇
  2004年   3438篇
  2003年   3505篇
  2002年   2287篇
  2001年   1309篇
  2000年   1322篇
  1999年   1323篇
  1998年   1219篇
  1997年   1076篇
  1996年   1183篇
  1995年   969篇
  1994年   852篇
  1993年   770篇
  1992年   672篇
  1991年   548篇
  1990年   464篇
  1989年   356篇
  1988年   324篇
  1987年   292篇
  1986年   223篇
  1985年   228篇
  1984年   194篇
  1983年   167篇
  1982年   139篇
  1981年   104篇
  1980年   104篇
  1979年   82篇
  1978年   64篇
  1976年   47篇
  1975年   52篇
  1914年   45篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
通过在FPD铁路上使用LVDS技术可使具有数字RGB接口的液晶显示屏的工作距离大大增加。文章通过一个具体应用环境介绍了21位LVDS发送器/接收器DS90C363/DS90CF364传输套片的主要特性、引脚功能、工作原理,同时指出了在具体设计使用时的注意事项。  相似文献   
62.
The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films were investigated using a number of techniques. A high saturation magnetic induction up to B s = 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed, which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of the composition. The text was submitted by the authors in English.  相似文献   
63.
从美国有线电视产业应对竞争的策略和举措获得的启示   总被引:1,自引:0,他引:1  
1前言 近年来出现了有关IP电视(网络电视)和移动电视(手机电视)属于电信增值业务,应当由电信企业主办、电信部门主管的大量论调,并已在社会上造成许多误解.由于其论据是外国情况、世界趋势就是这样,而且把这些信息网络传播视听节目的产业运营前景描绘得非常光明,笔者于是认真查考有关的外国情况,写了多篇综述(本刊2005年第2、第3、第5、第6、第8、第9、第14、第16及第22期),其中结合国情的评述,由于国内针对这些新事物的政策法规不明朗,论据尚有欠缺.  相似文献   
64.
With the proliferation of mobile computing technologies, location based services have been identified as one of the most promising target application. We classify mobile information service domains based on feature characteristics of the information sources and different patterns of mobile information access. By carefully examining the service requirements, we identify the dynamic data management problem that must be addressed for effective location based services in mobile environments. We then devise a general architecture and cost model for servicing both location independent and location dependent data. Based on the architecture and cost model, we propose a set of dynamic data management strategies that employs judicious caching, proactive server pushing and neighborhood replication to reduce service cost and improve response time under changing user mobility and access patterns. Detail behavior analysis helps us in precisely capturing when and how to apply these strategies. Simulation results suggest that different strategies are effective for different types of data in response to different patterns of movement and information access. Shiow-yang Wu is an associate professor of the Department of Computer Science and Information Engineering at National Dong Hwa University, Hualien, Taiwan, R.O.C. He received the BS and MS degrees in computer engineering from National Chiao Tung University, Hsinchu, Taiwan, ROC, and the PhD degree in computer science from the University of Texas at Austin in 1984, 1986, and 1995, respectively. His research interests include data/knowledge bases, mobile computing, distributed processing, intelligence information systems, and electronic commerce. Kun-Ta Wu was born in Taipei, Taiwan, R.O.C., in 1976. He received the B.S. degree in computer science from Soochow University, Taipei, Taiwan, R.O.C., in 1999 and the M.S. degree in computer science and information engineering from National Dong Hwa University, Hualien, Taiwan, R.O.C., in 2001. Currently, he is an Assistant Researcher in the Domestic Division at Science and Technology Information Center, National Science Council, R.O.C., as a member of Information Gathering and Analysis Group of National Information and Communication Security Taskforce. His research interests include mobile computing, wireless network and information security.  相似文献   
65.
This paper presents a novel power-driven multiplication instruction-set design method for application-specific instruction-set processors (ASIPs). Based on a dual-and-configurable-multiplier structure, our proposed method devises a multiplication instruction set for low-power ASIPs. Our method exploits the execution sequences of multiplication instructions and effective bit widths of variables to reduce power consumed by redundant multiplication bits while minimizing the multiplication execution time. Experimental results on a set of DSP programs demonstrate that our proposed method achieves significant power reduction (up to 18.53%) and execution time improvement (up to 10.43%) with 18% area overhead.  相似文献   
66.
孙暐  吴镇扬 《信号处理》2006,22(4):559-563
根据Flether等人的研究,基于感知独立性假设的子带识别方法被用于抗噪声鲁棒语音识别。本文拓展子带方法,采用基于噪声污染假定的多带框架来减少噪声影响。论文不仅从理论上分析了噪声污染假定多带框架在识别性能上的潜在优势,而且提出了多带环境下的鲁棒语音识别算法。研究表明:多带框架不仅回避了独立感知假设要求,而且与子带方法相比,多带方法能更好的减少噪声影响,提高系统识别性能。  相似文献   
67.
本文介绍了一种新颖的数码像素全息高速拍摄装置来实现全息母版的制作。提出和介绍了运用Photoshop软件一些特殊的图像处理功能设计制作动感像素全息图的方法,并结合多种防伪技术,使产生的图案具有不可仿制的图形畸变特点,并列举了设计实例。  相似文献   
68.
The advances in digital medical imaging and storage in integrated databases are resulting in growing demands for efficient image retrieval and management. Content-based image retrieval (CBIR) refers to the retrieval of images from a database, using the visual features derived from the information in the image, and has become an attractive approach to managing large medical image archives. In conventional CBIR systems for medical images, images are often segmented into regions which are used to derive two-dimensional visual features for region-based queries. Although such approach has the advantage of including only relevant regions in the formulation of a query, medical images that are inherently multidimensional can potentially benefit from the multidimensional feature extraction which could open up new opportunities in visual feature extraction and retrieval. In this study, we present a volume of interest (VOI) based content-based retrieval of four-dimensional (three spatial and one temporal) dynamic PET images. By segmenting the images into VOIs consisting of functionally similar voxels (e.g., a tumor structure), multidimensional visual and functional features were extracted and used as region-based query features. A prototype VOI-based functional image retrieval system (VOI-FIRS) has been designed to demonstrate the proposed multidimensional feature extraction and retrieval. Experimental results show that the proposed system allows for the retrieval of related images that constitute similar visual and functional VOI features, and can find potential applications in medical data management, such as to aid in education, diagnosis, and statistical analysis.  相似文献   
69.
70.
托盘能否有效运用对物流的畅通与否关系重大,这已经引起了国内外专家和学者们的重视,并就此制定了托盘电子信息化管理系统,旨在更合理地使用托盘,推进托盘一体化和共用系统的建立。而RFID技术在托盘的电子信息化管理的应用更将大大提高物流的效率与准确性,托盘电子信息化管理将成为今后托盘管理的趋势。  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