全文获取类型
收费全文 | 2862篇 |
免费 | 132篇 |
国内免费 | 89篇 |
专业分类
电工技术 | 54篇 |
技术理论 | 1篇 |
综合类 | 546篇 |
化学工业 | 224篇 |
金属工艺 | 64篇 |
机械仪表 | 237篇 |
建筑科学 | 359篇 |
矿业工程 | 41篇 |
能源动力 | 65篇 |
轻工业 | 48篇 |
水利工程 | 26篇 |
石油天然气 | 59篇 |
武器工业 | 7篇 |
无线电 | 167篇 |
一般工业技术 | 249篇 |
冶金工业 | 61篇 |
原子能技术 | 10篇 |
自动化技术 | 865篇 |
出版年
2024年 | 4篇 |
2023年 | 22篇 |
2022年 | 27篇 |
2021年 | 42篇 |
2020年 | 42篇 |
2019年 | 38篇 |
2018年 | 37篇 |
2017年 | 53篇 |
2016年 | 99篇 |
2015年 | 67篇 |
2014年 | 159篇 |
2013年 | 217篇 |
2012年 | 145篇 |
2011年 | 211篇 |
2010年 | 159篇 |
2009年 | 146篇 |
2008年 | 169篇 |
2007年 | 182篇 |
2006年 | 185篇 |
2005年 | 137篇 |
2004年 | 142篇 |
2003年 | 115篇 |
2002年 | 107篇 |
2001年 | 73篇 |
2000年 | 87篇 |
1999年 | 78篇 |
1998年 | 54篇 |
1997年 | 55篇 |
1996年 | 44篇 |
1995年 | 34篇 |
1994年 | 35篇 |
1993年 | 31篇 |
1992年 | 13篇 |
1991年 | 20篇 |
1990年 | 9篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1980年 | 4篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有3083条查询结果,搜索用时 31 毫秒
81.
交换机是分组网中的一个重要组成部分,对于分组网的性能有着很大影响。介绍共享存储器交换机的三种不同实现方法以及多播的实现过程.同时以排队论的知识为理论分析基础,介绍排队论中的生灭过程模型,状态转移模型和爱尔兰呼损模型,并对状态转移的稳态特性以及共享存储器结构的交换机的丢包率公式给出推导。对所做的工作做简要的总结,并指明未来的研究重点. 相似文献
82.
The specific problems associated with the work on board within the merchant fleet are well known and have over the years been a topic of discussion. The work conditions in the engine room (ER) are demanding due to, e.g. the thermal climate, noise and awkward working postures. The work in the engine control room (ECR) has over recent years undergone major changes, mainly due to the introduction of computers on board. In order to capture the impact these changes had implied, and also to investigate how the work situation has developed, a total of 20 engine officers and engine ratings were interviewed. The interviews were semi-structured and Grounded Theory was used for the data analysis. The aim of the present study was to describe how the engine crew perceive their work situation and working environment on board. Further, the aim was to identify areas for improvements which the engine crew consider especially important for a safe and effective work environment. The result of the study shows that the design of the ECR and ER is crucial for how different tasks are performed. Design which does not support operational procedures and how tasks are performed risk inducing inappropriate behaviour as the crew members’ are compelled to find alternative ways to perform their tasks in order to get the job done. These types of behaviour can induce an increased risk of exposure to hazardous substances and the engine crew members becoming injured. 相似文献
83.
84.
Víctor Lavín Puente 《Information Processing Letters》2011,111(11):550-555
Boolean formulas have been widely studied in the field of learning theory. We focus on the model of learning with queries, and study a restriction of the class of k-quasi-Horn formulas, that is, conjunctive normal form formulas where the number of unnegated literals per clause is at most k. This class is known to be as hard to learn as the general class CNF of conjunctive normal form formulas. By imposing some constraints, we define a fragment of this logic that can be learned using only membership queries. Also we prove that none of these constraints makes by itself the class learnable. 相似文献
85.
Yufeng Wang Akihiro Nakao Athanasios V. VasilakosJianhua Ma 《Computer Communications》2011,34(3):241-249
This paper thoroughly investigates the evolutionary dynamics of soft security mechanism, namely, reciprocity-based incentive mechanism, in P2P systems based on Evolutionary Game Theory (EGT). By soft security mechanism, it means social control mechanisms to overcome peers’ selfish (rational) behaviors, and encourage cooperation in P2P systems. Specifically, there exist three strategies in P2P systems: always cooperative (ALLC), always defect (ALLD) and reciprocator (R). Instead of existing work which take it for granted that, like ALLC users, R users did not bear any information-seeking cost, we assume small reciprocation cost, and study generalized mutation-selection dynamics. Our contributions are threefold: firstly, we prove and illustrate that, in a well-mixed P2P structure, ALLD is the only strict Nash equilibrium; secondly, we infer the specific condition under which evolution dynamics exhibits rock-scissors-paper oscillation in a structured P2P population. That is, the population cycles from ALLD to R to ALLC and back to ALLD; finally, we theoretically illustrate that the intensity of selection plays an important role in the evolutionary dynamics of P2P incentive mechanism. That is, when the intensity of selection is relatively weak and reciprocation cost limits to zero, the time average can be mostly concentrated on reciprocator. In brief, considering the existence of reciprocation cost and the small mutation in P2P incentive mechanisms, unlike existing work, it is impossible to simply achieve the “absolute cooperative” in P2P incentive mechanisms. On the other hand, stochastic evolution in P2P incentive mechanism with finite population and network structure still favor reciprocation. 相似文献
86.
Rough set based approaches to feature selection for Case-Based Reasoning classifiers 总被引:3,自引:0,他引:3
This paper investigates feature selection based on rough sets for dimensionality reduction in Case-Based Reasoning classifiers. In order to be useful, Case-Based Reasoning systems should be able to manage imprecise, uncertain and redundant data to retrieve the most relevant information in a potentially overwhelming quantity of data. Rough Set Theory has been shown to be an effective tool for data mining and for uncertainty management. This paper has two central contributions: (1) it develops three strategies for feature selection, and (2) it proposes several measures for estimating attribute relevance based on Rough Set Theory. Although we concentrate on Case-Based Reasoning classifiers, the proposals are general enough to be applicable to a wide range of learning algorithms. We applied these proposals on twenty data sets from the UCI repository and examined the impact of feature selection over classification performance. Our evaluation shows that all three proposals benefit the basic Case-Based Reasoning system. They also present robustness in comparison to well-known feature selection strategies. 相似文献
87.
Motivated by the increasing interest of the Computer Science community in the study and understanding of non-cooperative systems, we present a novel model for formalizing the rational behavior of agents with a more farsighted view of the consequences of their actions. This approach yields a framework creating new equilibria, which we call Second Order equilibria, starting from a ground set of traditional ones. By applying our approach to pure Nash equilibria, we define the set of Second Order pure Nash equilibria and present their applications to the Prisoner’s Dilemma game, to an instance of Braess’s Paradox in the Wardrop model and to the KP model with identical machines. 相似文献
88.
为了获得精确的氢键结合能并减小计算需求,在CCSD(T)水平下使用了一种基于相关一致性基函数的简单两点外推公式。为了提高氢键结合能的精确度,在公式中增加了一个变量。根据10个氢键体系分析的结果显示,使用基函数aug-cc-pVDZ和aug-cc-pVTZ计算所得总能量之差与变量存在线性关系,进而得到新的外推公式。从用于测试的18个氢键体系的数据显示,由这种外推方法获得的氢键结合能与使用基函数aug-cc-pVQZ计算所得结果能够很好的吻合。 相似文献
89.
粗集理论中的容错关系及其构造方法 总被引:1,自引:1,他引:0
粗集理论(Rough Sets Theory,RST)在许多领域已得到成功的应用,它在处理不完全、不精确、不确定性智能信息问题中表现出优秀品质。然而在标准RST理论中存在有局限性,比如对等价关系的定义使得知识约简相对复杂化。论文提出了基于RST的容错粗集的概念,给出了容错粗集上的性质,使得在进行知识约简时无需进行量化。从而大大提高了知识发现的效率。 相似文献
90.
WANG Xue-xin 《数字社区&智能家居》2008,(21)
计算机辅助教学与传统的课堂教学相比,的确具有其自身的优越性,它改变了以往传统电教手段相对呆板的教学方式,在文字、图形的基础上增加了图象,动画、声音、影像等,加强了表现效果;另一方面,当前的计算机辅助教学存在着严重的问题。要解决这些问题,必须做好教学设计工作我们如果想以某一种学习理论来指导我们的教学,解决教学中的一切问题,那也是行不通的。科学的做法是,以多种学习理论为指导,吸收其长处,克服其不足,对教学进行具体分析,鉴别不同的学习类型,再去寻找合适的指导思想、教学方法与策略。 相似文献