全文获取类型
收费全文 | 301551篇 |
免费 | 24321篇 |
国内免费 | 17337篇 |
专业分类
电工技术 | 39921篇 |
技术理论 | 46篇 |
综合类 | 34887篇 |
化学工业 | 13019篇 |
金属工艺 | 8436篇 |
机械仪表 | 22038篇 |
建筑科学 | 31420篇 |
矿业工程 | 11866篇 |
能源动力 | 9945篇 |
轻工业 | 6685篇 |
水利工程 | 10421篇 |
石油天然气 | 8413篇 |
武器工业 | 4745篇 |
无线电 | 30948篇 |
一般工业技术 | 15845篇 |
冶金工业 | 12332篇 |
原子能技术 | 2718篇 |
自动化技术 | 79524篇 |
出版年
2024年 | 968篇 |
2023年 | 2716篇 |
2022年 | 5405篇 |
2021年 | 6831篇 |
2020年 | 7463篇 |
2019年 | 5377篇 |
2018年 | 4984篇 |
2017年 | 6949篇 |
2016年 | 8348篇 |
2015年 | 9678篇 |
2014年 | 20290篇 |
2013年 | 17236篇 |
2012年 | 22203篇 |
2011年 | 23583篇 |
2010年 | 18146篇 |
2009年 | 18636篇 |
2008年 | 19033篇 |
2007年 | 23590篇 |
2006年 | 21040篇 |
2005年 | 18582篇 |
2004年 | 15434篇 |
2003年 | 13792篇 |
2002年 | 10558篇 |
2001年 | 8596篇 |
2000年 | 6955篇 |
1999年 | 5547篇 |
1998年 | 4068篇 |
1997年 | 3278篇 |
1996年 | 2843篇 |
1995年 | 2419篇 |
1994年 | 1974篇 |
1993年 | 1383篇 |
1992年 | 1122篇 |
1991年 | 819篇 |
1990年 | 641篇 |
1989年 | 566篇 |
1988年 | 415篇 |
1987年 | 234篇 |
1986年 | 198篇 |
1985年 | 208篇 |
1984年 | 203篇 |
1983年 | 194篇 |
1982年 | 108篇 |
1981年 | 88篇 |
1980年 | 72篇 |
1979年 | 71篇 |
1978年 | 43篇 |
1977年 | 46篇 |
1976年 | 29篇 |
1959年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
基于SONET/SDH的存储网络容灾技术分析 总被引:1,自引:0,他引:1
吴丽征 《微电子学与计算机》2006,23(6):119-122
文章分析了存储网络(SAN)容灾技术,认为在某些企业中,数据是至关重要的资产之一,是业务系统运行的血脉.保护企业的重要数据是企业成功的关键因素。文章讨论了设计容灾技术解决方案应考虑的各种因素,并给出了基于SONET/SDH的存储网络技术的体系架构设计方案。 相似文献
82.
Ben-Jye Chang 《Telecommunication Systems》2006,33(4):333-352
3G Wideband CDMA systems adopt the Orthogonal Variable Spreading Factor code tree as the channelization codes management for
achieving high data rate transmission in personal multimedia communications. It assigns a single channelization code for each
accepted connection. Nevertheless, it wastes the system capacity when the required rate is not powers of two of the basic
rate. One good solution is to assign multiple codes for each accepted connection but it causes two inevitable drawbacks: long
handoff delay and new call setup delay due to high complexity of processing with multiple channelization codes, and high cost
of using more number of rake combiners. Especially, long handoff delay may result in more call dropping probability and higher
Grade of Service, which will degrade significantly the utilization and revenue of the 3G cellular systems. Therefore, we propose
herein an adaptive efficient codes determination algorithm based on the Markov Decision Process analysis approach to reduce
the waste rate and reassignments significantly while providing fast handoff. Numerical results demonstrate that the proposed
approach yields several advantages, including the lowest GOS, the least waste rate, and the least number of reassignments.
Meanwhile, the optimal number of rake combiners is also analyzed in this paper.
This research was supported in part by the National Science Council of Taiwan, ROC, under contract NSC-93-2213-E-324-018. 相似文献
83.
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
84.
随着运动控制技术的飞速发展,交流伺服系统应用的日益广泛。介绍了液晶生产中的关键设备玻璃裂片机,并详细分析松下MINAS A系列交流伺服系统在玻璃裂片机中的应用。 相似文献
85.
管道风险管理方法研究 总被引:6,自引:0,他引:6
按照管道风险管理的流程分别对管道风险评价、风险控制和决策支持、效能测试和响应进行了论述。针对目前国内管道行业的情况,提出了进行管道风险评价的有效方法及维护措施。着重介绍了国外管道风险可接受标准的情况,作为国内制定管道风险评价标准的参考。 相似文献
86.
针对国外变频器价格昂贵、调试周期和维修周期长等特点,我公司自主研发了可替代进口机的高性能钻机国产专用变频器。该变频器能够从零开始调速。当钻井卡钻时,能及时断开电动机,在低速提升时,能最大限度地发挥电动机的动力特性,提供220%的转矩输出。变频器具有易安装、调试、维护,性能稳定。应用中据实测数据显示,采用变频改造后,打1口井可节省柴油15t。 相似文献
87.
Efficient multicast search under delay and bandwidth constraints 总被引:1,自引:0,他引:1
The issue of a multicast search for a group of users is discussed in this study. Given the condition that the search is over
only after all the users in the group are found, this problem is called the Conference Call Search (CCS) problem. The goal
is to design efficient CCS strategies under delay and bandwidth constraints. While the problem of tracking a single user has
been addressed by many studies, to the best of our knowledge, this study is one of the first attempts to reduce the search
cost for multiple users. Moreover, as oppose to the single user tracking, for which one can always reduce the expected search
delay by increasing the expected search cost, for a multicast search the dependency between the delay and the search cost
is more complicated, as demonstrated in this study. We identify the key factors affecting the search efficiency, and the dependency
between them and the search delay. Our analysis shows that under tight bandwidth constraints, the CCS problem is NP-hard.
We therefore propose a search method that is not optimal, but has a low computational complexity. In addition, the proposed
strategy yields a low search delay as well as a low search cost. The performance of the proposed search strategy is superior
to the implementation of an optimal single user search on a group of users.
Amotz Bar-Noy received the B.Sc. degree in 1981 in Mathematics and Computer Science and the Ph.D. degree in 1987 in Computer Science, both
from the Hebrew University, Israel. From October 1987 to September 1989 he was a post-doc fellow in Stanford University, California.
From October 1989 to August 1996 he was a Research Staff Member with IBM T. J. Watson Research Center, New York. From February
1995 to September 2001 he was an associate Professor with the Electrical Engineering-Systems department of Tel Aviv University,
Israel. From September 1999 to December 2001 he was with AT research labs in New Jersey. Since February 2002 he is a Professor
with the Computer and Information Science Department of Brooklyn College - CUNY, Brooklyn New York.
Zohar Naor received the Ph.D. degree in Computer Science from Tel Aviv University, Tel Aviv, Israel, in 2000. Since 2003 he is with
the University of Haifa, Israel. His areas of interests include wireless networks, resource management of computer networks,
mobility, search strategies, and multiple access protocols. 相似文献
88.
基于ISO/IEC17799标准建立了一个综合的信息系统风险分析框架,并运用模糊多准则决策(FMCDM)方法计算信息安全风险,根据风险等级矩阵(RLM)对信息资产风险进行级别划分,最终建立评估信息资产相关风险的完整模型。 相似文献
89.
为实现电源设备乃至通信机房的少人或无人值守和集中维护,必须建立一套完善的电信局动力环境集中监控系统。文中结合番禺区电信局的实际,讨论了提高系统运行可靠性的几点措施,包括硬件方面与软件方面的手段,关键在于加强系统的运行管理。 相似文献
90.