全文获取类型
收费全文 | 142656篇 |
免费 | 9919篇 |
国内免费 | 5543篇 |
专业分类
电工技术 | 8206篇 |
技术理论 | 23篇 |
综合类 | 13199篇 |
化学工业 | 18319篇 |
金属工艺 | 7917篇 |
机械仪表 | 7776篇 |
建筑科学 | 17705篇 |
矿业工程 | 5858篇 |
能源动力 | 3673篇 |
轻工业 | 9389篇 |
水利工程 | 5489篇 |
石油天然气 | 5035篇 |
武器工业 | 888篇 |
无线电 | 9094篇 |
一般工业技术 | 9989篇 |
冶金工业 | 11096篇 |
原子能技术 | 909篇 |
自动化技术 | 23553篇 |
出版年
2024年 | 432篇 |
2023年 | 1341篇 |
2022年 | 2634篇 |
2021年 | 3370篇 |
2020年 | 3789篇 |
2019年 | 2751篇 |
2018年 | 2453篇 |
2017年 | 3260篇 |
2016年 | 3948篇 |
2015年 | 4315篇 |
2014年 | 10162篇 |
2013年 | 9157篇 |
2012年 | 10350篇 |
2011年 | 11004篇 |
2010年 | 8198篇 |
2009年 | 8629篇 |
2008年 | 8095篇 |
2007年 | 10119篇 |
2006年 | 9203篇 |
2005年 | 7890篇 |
2004年 | 6805篇 |
2003年 | 6046篇 |
2002年 | 5011篇 |
2001年 | 3979篇 |
2000年 | 3218篇 |
1999年 | 2563篇 |
1998年 | 1888篇 |
1997年 | 1433篇 |
1996年 | 1275篇 |
1995年 | 1015篇 |
1994年 | 833篇 |
1993年 | 559篇 |
1992年 | 459篇 |
1991年 | 366篇 |
1990年 | 241篇 |
1989年 | 236篇 |
1988年 | 184篇 |
1987年 | 107篇 |
1986年 | 124篇 |
1985年 | 111篇 |
1984年 | 114篇 |
1983年 | 114篇 |
1982年 | 41篇 |
1981年 | 34篇 |
1980年 | 38篇 |
1979年 | 28篇 |
1977年 | 28篇 |
1961年 | 14篇 |
1959年 | 17篇 |
1951年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
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
102.
姜浩 《信息安全与通信保密》2006,(10):49-50
论文详细描述并分析了从RC5到RC6的演化设计过程,在详细研究了RC6性能的同时,指出了应该如何从一个旧的密码设计出好的新密码。最后对RC6和Rijndael作了一些比较,指出各自在性能上的优缺点。 相似文献
103.
Real-time multimedia applications have to use forward error correction (FEC) anderror concealment techniques to cope with
losses in today’s best-effort Internet. The efficiency of these solutions is known however to depend on the correlation between
losses in the media stream. In this paper we investigate how the packet size distribution affects the packet loss process,
that is, the distribution of the number of lost packets in a block, the related FEC performance and the average loss run length.
We present mathematical models for the loss process of the MMPP+M/D/1/K and the MMPP+M/M/1/K queues; we validate the models
via simulations, and compare the results to simulation results with an MPEG-4 coded video trace. We conclude that the deterministic
packet size distribution (PSD) not only results in lower stationary loss probability than the exponential one, but also gives
a less correlated loss process, both at a particular average link load and at a particular stationary loss probability as
seen by the media stream.Our results show that for applications that can only measure the packet loss probability, the effects
of the PSD on FEC performance are higher in access networks, where a single multimedia stream might affect the multiplexing
behavior. Our results show that the effects of the PSD on FEC performance are higher in access networks, where a single multimedia
stream might affect the multiplexing behavior and thus can improve the queuing performance by decreasing the variance of its
PSD. 相似文献
104.
探讨分类挖掘技术在高校实际工作中的应用方式与应用领域。以高校人事管理为模型,应用数据挖掘中决策树算法,对高校人力资源数据源中的信息进行分析,发现其中有价值的数据模式,寻找其中存在的关系和规则,对高校人才规划提供比较客观的决策支持。 相似文献
105.
以亚欧海底光缆S2段为例,介绍亚欧海底光缆远供电源(PFE)的供电方式,以及其在正常运行时和故障维修时的维护管理方法。探讨在实际维护中如何贯彻落实及灵活运用系统联合维护文档,总结适合中国国情的远供电源维护经验,确保亚欧海底光缆远供电源安全稳定运行。 相似文献
106.
福建周宁水电站工程由闽东水电开发有限公司负责项目管理。该项目严格按照《招投标法》进行工程和设备的招标,进行了多项设计优化,注重工程质量和安全文明生产,积极开展达标投产工作,实现了进度快、质量优、投资省、效益好的管理目标。 相似文献
107.
沙漠地区高精度地震资料处理技术 总被引:1,自引:1,他引:0
受静校正及各种类型干扰的影响,西部沙漠地区地震资料的高精度处理较东部地区有更大的难度。对准噶尔盆地中部Ⅱ区、Ⅲ区、Ⅳ区、顺托果勒等区块地震资料在振幅恢复、静校正、去除各类噪音、高精度速度分析及叠前、叠后子波处理等方面进行了大量的试验与研究,形成了较为系统的高精度地震资料处理技术,在西部不同区块地震资料处理中取得了较好的应用效果。 相似文献
108.
设计管理信息系统的提出及其面临的问题 总被引:12,自引:2,他引:10
从管理和设计的两个方面出发,通过对现代企业产品设计管理信息系统的探讨,阐明了设计管理信息系统的概念和结构;并对其实施的条件及面临的困难进行了系统的分析。 相似文献
109.
110.