全文获取类型
收费全文 | 86381篇 |
免费 | 14573篇 |
国内免费 | 9644篇 |
专业分类
电工技术 | 8904篇 |
技术理论 | 2篇 |
综合类 | 9738篇 |
化学工业 | 10568篇 |
金属工艺 | 1509篇 |
机械仪表 | 5557篇 |
建筑科学 | 2620篇 |
矿业工程 | 1103篇 |
能源动力 | 3999篇 |
轻工业 | 2291篇 |
水利工程 | 1273篇 |
石油天然气 | 1276篇 |
武器工业 | 1205篇 |
无线电 | 12526篇 |
一般工业技术 | 6959篇 |
冶金工业 | 911篇 |
原子能技术 | 382篇 |
自动化技术 | 39775篇 |
出版年
2024年 | 618篇 |
2023年 | 1634篇 |
2022年 | 3095篇 |
2021年 | 3390篇 |
2020年 | 3607篇 |
2019年 | 3026篇 |
2018年 | 2824篇 |
2017年 | 3338篇 |
2016年 | 3686篇 |
2015年 | 4305篇 |
2014年 | 5881篇 |
2013年 | 5676篇 |
2012年 | 7337篇 |
2011年 | 7521篇 |
2010年 | 6141篇 |
2009年 | 6202篇 |
2008年 | 6303篇 |
2007年 | 7047篇 |
2006年 | 5573篇 |
2005年 | 4687篇 |
2004年 | 3824篇 |
2003年 | 3114篇 |
2002年 | 2306篇 |
2001年 | 1835篇 |
2000年 | 1610篇 |
1999年 | 1283篇 |
1998年 | 1043篇 |
1997年 | 813篇 |
1996年 | 632篇 |
1995年 | 429篇 |
1994年 | 402篇 |
1993年 | 317篇 |
1992年 | 279篇 |
1991年 | 153篇 |
1990年 | 160篇 |
1989年 | 98篇 |
1988年 | 80篇 |
1987年 | 34篇 |
1986年 | 45篇 |
1985年 | 41篇 |
1984年 | 27篇 |
1983年 | 26篇 |
1982年 | 30篇 |
1981年 | 14篇 |
1980年 | 26篇 |
1978年 | 10篇 |
1977年 | 9篇 |
1975年 | 9篇 |
1959年 | 9篇 |
1951年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
An effective coding approach for multiobjective integrated resource selection and operation sequences problem 总被引:3,自引:1,他引:2
In this paper, we consider an integrated Resource Selection and Operation Sequences (iRS/OS) problem in Intelligent Manufacturing
System (IMS). Several kinds of objectives are taken into account, in which the makespan for orders should be minimized; workloads
among machine tools should be balanced; the total transition times between machines in a local plant should also be minimized.
To solve this multiobjective iRS/OS model, a new two vectors-based coding approach has been proposed to improve the efficiency
by designing a chromosome containing two kinds of information, i.e., operation sequences and machine selection. Using such
kind of chromosome, we adapt multistage operation-based Genetic Algorithm (moGA) to find the Pareto optimal solutions. Moreover
a special technique called left-shift hillclimber has been used as one kind of local search to improve the efficiency of our
algorithm. Finally, the experimental results of several iRS/OS problems indicate that our proposed approach can obtain best
solutions. Further more comparing with previous approaches, moGA performs better for finding Pareto solutions.
Received: May 2005/Accepted: December 2005 相似文献
82.
马钢二烧结配料计算机控制系统 总被引:1,自引:0,他引:1
阐明了马钢二烧结配科计算机控制系统的目的、控制形式、控制原理;根据烧结配料控制对象的特点对信号采样和控制算法进行了探讨;提供了系统的主要硬件结构,软件功能和程序框图。 相似文献
83.
Namyong Kim 《ETRI Journal》2006,28(2):155-161
In this paper, we introduce an escalator (ESC) algorithm based on the least squares (LS) criterion. The proposed algorithm is relatively insensitive to the eigenvalue spread ratio (ESR) of an input signal and has a faster convergence speed than the conventional ESC algorithms. This algorithm exploits the fast adaptation ability of least squares methods and the orthogonalization property of the ESC structure. From the simulation results, the proposed algorithm shows superior convergence performance. 相似文献
84.
USB数据传输中CRC校验码的并行算法实现 总被引:8,自引:2,他引:6
文章介绍了用于USB总线数据传输的CRC校验的原理和算法,并且采用并行电路实现USB2.0中的CRC产生和CRC校验,与传统的串行电路实现相比,并行电路实现方法虽然在芯片面积上大于串行电路实现,但由于降低了时钟频率,电路更容易综合实现,并且大大降低了功耗,有利于低功耗电路设计。 相似文献
85.
基于进化算法的常减压装置模拟 总被引:1,自引:0,他引:1
提出了基于优选优生进化算法(Select—best and prepotency evolution algorithm,SPEA)的常减压装置模拟方法。以各塔的温度分布为目标,基于生产过程和分析数据,采用SPEA确定各塔板Murphree效率,从而精确描述各塔板平衡偏离程度。在实际应用中,获得具有良好精度的常减压装置模型。系统分析了SPEA算法的关键参数——优选领域大小与计算复杂性及寻优性能之间的关系,结果显示其取值为群体规模的10%最为合适。 相似文献
86.
基于两层均匀媒质的GPEN SAR地下目标成像方法及其性能分析 总被引:3,自引:0,他引:3
地表穿透合成孔径雷达(Ground PENetration SAR,GPEN SAR)为了探测掩埋在地下的目标,通常工作在多层媒质的环境中。传统成像模型是建立在同一均匀媒质的假设上,不再适合于GPEN SAR的实际情况。本文首先建立了两层分区均匀媒质中的成像模型,然后利用后向投影(BP)算法定量分析了成像几何参数、土壤参数等对成像的影响,进而提出了一种修正的后向投影(MBP)算法。MBP算法不仅能够校正两层分区均匀媒质对成像定位的影响,还能估计目标的掩埋深度,提供目标三维位置坐标。仿真结果验证了MBP算法在不同信噪比环境下,对多目标的三维定位精度能满足实际的需要。 相似文献
87.
Depending on whether bidirectional links or unidirectional links are used for communications, the network topology under a
given range assignment is either an undirected graph referred to as the bidirectional topology, or a directed graph referred
to as the unidirectional topology. The Min-Power Bidirectional (resp., Unidirectional) k-Node Connectivity problem seeks a range assignment of minimum total power subject to the constraint that the produced bidirectional
(resp. unidirectional) topology is k-vertex connected. Similarly, the Min-Power Bidirectional (resp., Unidirectional) k-Edge Connectivity problem seeks a range assignment of minimum total power subject to the constraint the produced bidirectional
(resp., unidirectional) topology is k-edge connected.
The Min-Power Bidirectional Biconnectivity problem and the Min-Power Bidirectional Edge-Biconnectivity problem have been studied
by Lloyd et al. [23]. They show that range assignment based the approximation algorithm of Khuller and Raghavachari [18],
which we refer to as Algorithm KR, has an approximation ratio of at most 2(2 – 2/n)(2 + 1/n) for Min-Power Bidirectional Biconnectivity, and range assignment based on the approximation algorithm of Khuller and Vishkin [19],
which we refer to as Algorithm KV, has an approximation ratio of at most 8(1 – 1/n) for Min-Power Bidirectional Edge-Biconnectivity.
In this paper, we first establish the NP-hardness of Min-Power Bidirectional (Edge-) Biconnectivity. Then we show that Algorithm KR has an approximation ratio of at most 4 for both Min-Power Bidirectional Biconnectivity and Min-Power Unidirectional Biconnectivity,
and Algorithm KV has an approximation ratio of at most 2k for both Min-Power Bidirectional k-Edge Connectivity and Min-Power Unidirectional k-Edge Connectivity. We also propose a new simple constant-approximation algorithm for both Min-Power Bidirectional Biconnectivity
and Min-Power Unidirectional Biconnectivity. This new algorithm applies only to Euclidean instances, but is best suited for
distributed implementation.
A preliminary version of this work appeared in the proceedings of the 2nd International Conference on AD-HOC Network and Wireless
(Adhoc-Now 2003).
Research performed in part while visiting the Max-Plank-Institut fur Informatik.
Gruia Calinescu is an Assistant Professor of Computer Science at the Illinois Institute of Technology since 2000. He held postdoc or visiting
researcher positions at DIMACS, University of Waterloo, and Max-Plank Institut fur Informatik. Gruia has a Diploma from University
of Bucharest and a Ph.D. from Georgia Insitute of Technology. His research interests are in the area of algorithms.
Peng-Jun Wan has joined the Computer Science Department at Illinois Institute of Technology in 1997 and has been an Associate Professor
since 2004. He received his Ph.D. in Computer Science from University of Minnesota in 1997, M.S. in Operations Research and
Control Theory from Chinese Academy of Science in 1993, and B.S. in Applied Mathematics from Tsinghua University in 1990.
His research interests include optical networks and wireless networks. 相似文献
88.
论文提出利用用户提供的个性化信息来随机产生关联大素数,保证了素数选取的随机化、个性化,提高了RSA算法的安全性。 相似文献
89.
为了提高现代网络信息传输的安全性,利用无理数小数点后数字的无穷性、无规律性、分布均匀性,提出一种全新的加密算法,并用它所产生的密钥流进行数字签名,实现身份验证不可抵赖、信息传输无篡改,确保信息传输的完整性、真实性,达到提高加密效率、相互认证的效果。 相似文献
90.
文章分析了人工免疫系统的原理,简单建立了一种基于否定选择算法的网络入侵检测系统,引入了一种用于异常事件识别的r-字符块匹配规则,并对规则存在的漏洞进行了分析。 相似文献