全文获取类型
收费全文 | 1974篇 |
免费 | 135篇 |
国内免费 | 142篇 |
专业分类
电工技术 | 43篇 |
综合类 | 67篇 |
化学工业 | 108篇 |
金属工艺 | 45篇 |
机械仪表 | 190篇 |
建筑科学 | 23篇 |
矿业工程 | 34篇 |
能源动力 | 28篇 |
轻工业 | 51篇 |
水利工程 | 11篇 |
石油天然气 | 8篇 |
武器工业 | 12篇 |
无线电 | 101篇 |
一般工业技术 | 55篇 |
冶金工业 | 28篇 |
原子能技术 | 103篇 |
自动化技术 | 1344篇 |
出版年
2024年 | 3篇 |
2023年 | 7篇 |
2022年 | 13篇 |
2021年 | 46篇 |
2020年 | 33篇 |
2019年 | 42篇 |
2018年 | 40篇 |
2017年 | 51篇 |
2016年 | 53篇 |
2015年 | 63篇 |
2014年 | 66篇 |
2013年 | 113篇 |
2012年 | 101篇 |
2011年 | 139篇 |
2010年 | 121篇 |
2009年 | 145篇 |
2008年 | 165篇 |
2007年 | 215篇 |
2006年 | 193篇 |
2005年 | 128篇 |
2004年 | 99篇 |
2003年 | 136篇 |
2002年 | 61篇 |
2001年 | 43篇 |
2000年 | 33篇 |
1999年 | 28篇 |
1998年 | 21篇 |
1997年 | 11篇 |
1996年 | 11篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1959年 | 1篇 |
排序方式: 共有2251条查询结果,搜索用时 312 毫秒
101.
102.
目前对未知区间值的研究还处于起步阶段。以包含复杂的遗漏型未知区间值不完备信息系统为研究对象,提出了一种基于灰格运算和Hausdorff距离的新的邻域关系。在此基础上,依次提出了邻域关系、最大相容类和邻域系统3种灰色粗集模型。进一步讨论了3种灰色粗集模型之间的上、下近似空间,以提高近似空间的精确度,并用实例进行了分析及验证。 相似文献
103.
Yuhua Qian Author Vitae Jiye Liang Author Vitae Witold Pedrycz Author Vitae 《Pattern recognition》2011,44(8):1658-1670
Feature selection (attribute reduction) from large-scale incomplete data is a challenging problem in areas such as pattern recognition, machine learning and data mining. In rough set theory, feature selection from incomplete data aims to retain the discriminatory power of original features. To address this issue, many feature selection algorithms have been proposed, however, these algorithms are often computationally time-consuming. To overcome this shortcoming, we introduce in this paper a theoretic framework based on rough set theory, which is called positive approximation and can be used to accelerate a heuristic process for feature selection from incomplete data. As an application of the proposed accelerator, a general feature selection algorithm is designed. By integrating the accelerator into a heuristic algorithm, we obtain several modified representative heuristic feature selection algorithms in rough set theory. Experiments show that these modified algorithms outperform their original counterparts. It is worth noting that the performance of the modified algorithms becomes more visible when dealing with larger data sets. 相似文献
104.
Soft sets and soft rough sets 总被引:4,自引:0,他引:4
In this study, we establish an interesting connection between two mathematical approaches to vagueness: rough sets and soft sets. Soft set theory is utilized, for the first time, to generalize Pawlak’s rough set model. Based on the novel granulation structures called soft approximation spaces, soft rough approximations and soft rough sets are introduced. Basic properties of soft rough approximations are presented and supported by some illustrative examples. We also define new types of soft sets such as full soft sets, intersection complete soft sets and partition soft sets. The notion of soft rough equal relations is proposed and related properties are examined. We also show that Pawlak’s rough set model can be viewed as a special case of the soft rough sets, and these two notions will coincide provided that the underlying soft set in the soft approximation space is a partition soft set. Moreover, an example containing a comparative analysis between rough sets and soft rough sets is given. 相似文献
105.
Mining significant factors affecting the adoption of SaaS using the rough set approach 总被引:1,自引:0,他引:1
Wei-Wen WuAuthor Vitae 《Journal of Systems and Software》2011,84(3):435-441
Despite that Software as a Service (SaaS) seems to be the most tempting solution among different types of cloud services, yet it has not been adopted to-date with as much alacrity as was originally expected. A variety of factors may influence the adoption of SaaS solutions. The objective of this study is thus to explore the significant factors affecting the adoption of SaaS for vendors and enterprise users. An analytical framework is proposed containing two approaches—Technology Acceptance Model (TAM) and Rough Set Theory (RST). An empirical study on the IT/MIS enterprises in Taiwan is carried out. The results have revealed a considerable amount of meaningful information, which not only facilitates the SaaS vendors to grasp users’ needs and concerns about SaaS adoption, but also helps the managers to introduce effective marketing strategies and actions to promote the growth of SaaS market. Based on the findings, some managerial implications are discussed. 相似文献
106.
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
107.
108.
Support vector regression provides an alternative to the neural networks in modeling non-linear real-world patterns. Rough values, with a lower and upper bound, are needed whenever the variables under consideration cannot be represented by a single value. This paper describes two approaches for the modeling of rough values with support vector regression (SVR). One approach, by attempting to ensure that the predicted high value is not greater than the upper bound and that the predicted low value is not less than the lower bound, is conservative in nature. On the contrary, we also propose an aggressive approach seeking a predicted high which is not less than the upper bound and a predicted low which is not greater than the lower bound. The proposal is shown to use ?-insensitivity to provide a more flexible version of lower and upper possibilistic regression models. The usefulness of our work is realized by modeling the rough pattern of a stock market index, and can be taken advantage of by conservative and aggressive traders. 相似文献
109.
In this paper, we discuss the importance of information systems in modeling interactive computations performed on (complex) granules and we propose a formal approach to interactive computations based on generalized information systems and rough sets which can be combined with other soft computing paradigms such as fuzzy sets or evolutionary computing, but also with machine learning and data mining techniques. Information systems are treated as dynamic granules used for representing the results of the interaction of attributes with the environment. Two kinds of attributes are distinguished, namely, the perception attributes, including sensory attributes, and the action attributes. Sensory attributes are the basic perception attributes, other perception attributes are constructed on the basis of the sensory ones. Actions are activated when their guards, being often complex and vague concepts, are satisfied to a satisfactory degree. The guards can be approximated on the basis of measurements performed by sensory attributes rather than defined exactly. Satisfiability degrees for guards are results of reasoning called the adaptive judgment. The approximations are induced using hierarchical modeling. We show that information systems can be used for modeling more advanced forms of interactions in hierarchical modeling. The role of hierarchical interactions is emphasized in the modeling of interactive computations. Some illustrative examples of interactions used in the ACT-R 6.0 system are reported. ACT-R 6.0 is based on a cognitive architecture and can be treated as an example of a highly interactive complex granule which can be involved in hierarchical interactions. For modeling of interactive computations, we propose much more general information systems than the studied dynamic information systems (see, e.g., Ciucci (2010) [8] and Pa?asiński and Pancerz (2010) [32]). For example, the dynamic information systems are making it possible to consider incremental changes in information systems. However, they do not contain the perception and action attributes necessary for modeling interactive computations, in particular for modeling intrastep interactions. 相似文献
110.