全文获取类型
收费全文 | 24044篇 |
免费 | 1922篇 |
国内免费 | 873篇 |
专业分类
电工技术 | 1157篇 |
技术理论 | 5篇 |
综合类 | 1334篇 |
化学工业 | 4323篇 |
金属工艺 | 1607篇 |
机械仪表 | 1449篇 |
建筑科学 | 1796篇 |
矿业工程 | 676篇 |
能源动力 | 778篇 |
轻工业 | 1582篇 |
水利工程 | 367篇 |
石油天然气 | 1646篇 |
武器工业 | 150篇 |
无线电 | 2438篇 |
一般工业技术 | 3016篇 |
冶金工业 | 1372篇 |
原子能技术 | 251篇 |
自动化技术 | 2892篇 |
出版年
2024年 | 122篇 |
2023年 | 479篇 |
2022年 | 721篇 |
2021年 | 1006篇 |
2020年 | 828篇 |
2019年 | 692篇 |
2018年 | 800篇 |
2017年 | 819篇 |
2016年 | 712篇 |
2015年 | 958篇 |
2014年 | 1143篇 |
2013年 | 1551篇 |
2012年 | 1493篇 |
2011年 | 1570篇 |
2010年 | 1376篇 |
2009年 | 1311篇 |
2008年 | 1255篇 |
2007年 | 1214篇 |
2006年 | 1288篇 |
2005年 | 1118篇 |
2004年 | 683篇 |
2003年 | 632篇 |
2002年 | 580篇 |
2001年 | 466篇 |
2000年 | 536篇 |
1999年 | 648篇 |
1998年 | 550篇 |
1997年 | 410篇 |
1996年 | 397篇 |
1995年 | 331篇 |
1994年 | 273篇 |
1993年 | 189篇 |
1992年 | 155篇 |
1991年 | 107篇 |
1990年 | 88篇 |
1989年 | 49篇 |
1988年 | 66篇 |
1987年 | 41篇 |
1986年 | 29篇 |
1985年 | 32篇 |
1984年 | 28篇 |
1983年 | 16篇 |
1982年 | 12篇 |
1981年 | 9篇 |
1980年 | 13篇 |
1979年 | 9篇 |
1978年 | 4篇 |
1974年 | 3篇 |
1959年 | 2篇 |
1958年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
111.
杜冀秦 《计算机光盘软件与应用》2010,(12)
考虑到工控位号历史数据时间戳递增的特点,针对已有实时数据库产品历史数据存储索引查询效率不高,磁盘空间利用率低的不足,提出了一种以B+树为索引方式,以状态链表和页式存储为管理方式的历史数据缓冲区管理方式.经过实际测试表明,基于该缓冲区管理算法的历史数据存储模块存取效率高,并发性能好,磁盘空间的利用率高,完全可以替代关系数据库作为实时数据库的历史数据存储模块. 相似文献
112.
Richmond VL Rayson MP Wilkinson DM Carter JM Blacker SD Nevill A Ross JD Moore S 《Ergonomics》2008,51(6):935-946
Since 2002, the Royal Air Force (RAF) has been working towards developing role-related physical tests for use as an operational fitness test (OFT). The purpose of this study was to establish reliability of the OFT (comprising four tests), investigate gym-based tests as predictors of performance and establish performance standards. Fifty-eight RAF personnel performed the OFT on three occasions. A separate cohort carried out fitness and anthropometric tests before performing the OFT, by way of establishing performance predictors. Documented evidence and views of an expert panel were used to determine OFT standards. Reliability ranged from moderate to good for three tests, with one test (Dig) showing poor reliability. The 95% limits of agreement for the prediction models ranged from good to poor (6.7-34.2%). The prediction models were not sufficiently accurate to estimate confidently OFT performance, but could be used as a guide to quantify likely outcome and training needs. 相似文献
113.
Weilin Du 《Information Sciences》2008,178(15):3096-3109
Optimization in dynamic environments is important in real-world applications, which requires the optimization algorithms to be able to find and track the changing optimum efficiently over time. Among various algorithms for dynamic optimization, particle swarm optimization algorithms (PSOs) are attracting more and more attentions in recent years, due to their ability of keeping good balance between convergence and diversity maintenance. To tackle the challenges of dynamic optimization, several strategies have been proposed to enhance the performance of PSO, and have gained success on various dynamic optimization problems. But there still exist some issues in dynamic optimization which need to be studied carefully, i.e. the robustness of the algorithm to problems of various dynamic features. In this paper, a new multi-strategy ensemble particle swarm optimization (MEPSO) for dynamic optimization is proposed. In MEPSO, all particles are divided into two parts, denoted as part I and part II, respectively. Two new strategies, Gaussian local search and differential mutation, are introduced into these two parts, respectively. Experimental analyses reveal that the mechanisms used in part I can enhance the convergence ability of the algorithm, while mechanisms used in part II can extend the searching area of the particle population to avoid being trapped into the local optimum, and can enhance the ability of catching up with the changing optimum in dynamic environments. The whole algorithm has few parameters that need to be tuned, and all of them are not sensitive to problems. We compared MEPSO with other PSOs, including MQSO, PHPSO and Standard PSO with re-initialization, on moving peaks Benchmark and dynamic Rastrigin function. The experimental results show that MEPSO has pretty good performance on almost all testing problems adopted in this paper, and outperforms other algorithms when the dynamic environment is unimodal and changes severely, or has a great number of local optima as dynamic Rastrigin function does. 相似文献
114.
115.
116.
117.
How to compose existing web services automatically and to guarantee the correctness of the design(e.g. freeness of deadlock and unspecified reception,and temporal constraints) is an important and challenging problem in web services. Most existing approaches require a detailed specification of the desired behaviors of a composite service beforehand and then perform certain formal verification to guarantee the correctness of the design,which makes the composition process both complex and time-consuming. In th... 相似文献
118.
多类支持向量机推广性能分析 总被引:1,自引:0,他引:1
为了分析多类支持向量机(Multi-category support vector machines,M-SVMs)的推广性能,对常用的M-SVMs算法加以概述,推导、总结了理论推广误差公式.对于给定的样本集,可以设计合理的编码来提高ECOCSVMs的推广性能,通过构造合理的层次结构来提高H-SVMs推广性能,其余M-SVMs算法的推广性能均取决于样本空间.研究结果为有效使用M-SVMs提供了依据,为改进M-SVMs指明了方向. 相似文献
119.
120.
基于显著性检验的意义及其存在的问题,提出了评价经验模型预测性的观点与方法,从理论与实践两方面探讨有关的统计检验手段,进而提出预测性检验理论.所涉方法用于化工装置的建模实践,实际效果良好.在其他领域,同样具有理论和实践的指导意义. 相似文献