首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1835篇
  免费   61篇
  国内免费   18篇
电工技术   25篇
技术理论   1篇
综合类   46篇
化学工业   36篇
金属工艺   4篇
机械仪表   23篇
建筑科学   188篇
矿业工程   12篇
能源动力   302篇
轻工业   42篇
水利工程   7篇
石油天然气   17篇
武器工业   1篇
无线电   79篇
一般工业技术   241篇
冶金工业   13篇
原子能技术   1篇
自动化技术   876篇
  2024年   1篇
  2023年   92篇
  2022年   43篇
  2021年   91篇
  2020年   131篇
  2019年   89篇
  2018年   45篇
  2017年   171篇
  2016年   144篇
  2015年   102篇
  2014年   178篇
  2013年   125篇
  2012年   85篇
  2011年   117篇
  2010年   71篇
  2009年   65篇
  2008年   31篇
  2007年   64篇
  2006年   37篇
  2005年   40篇
  2004年   22篇
  2003年   20篇
  2002年   23篇
  2001年   31篇
  2000年   21篇
  1999年   19篇
  1998年   12篇
  1997年   14篇
  1996年   11篇
  1995年   1篇
  1994年   3篇
  1993年   3篇
  1990年   1篇
  1988年   2篇
  1983年   1篇
  1982年   2篇
  1981年   1篇
  1980年   2篇
  1979年   1篇
  1978年   1篇
  1960年   1篇
排序方式: 共有1914条查询结果,搜索用时 31 毫秒
41.
Support Vector Machine, an optimization technique, is well known in the data mining community. In fact, many other optimization techniques have been effectively used in dealing with data separation and analysis. For the last 10 years, the author and his colleagues have proposed and extended a series of optimization-based classification models via Multiple Criteria Linear Programming (MCLP) and Multiple Criteria Quadratic Programming (MCQP). These methods are different from statistics, decision tree induction, and neural networks. The purpose of this paper is to review the basic concepts and frameworks of these methods and promote the research interests in the data mining community. According to the evolution of multiple criteria programming, the paper starts with the bases of MCLP. Then, it further discusses penalized MCLP, MCQP, Multiple Criteria Fuzzy Linear Programming (MCFLP), Multi-Class Multiple Criteria Programming (MCMCP), and the kernel-based Multiple Criteria Linear Program, as well as MCLP-based regression. This paper also outlines several applications of Multiple Criteria optimization-based data mining methods, such as Credit Card Risk Analysis, Classification of HIV-1 Mediated Neuronal Dendritic and Synaptic Damage, Network Intrusion Detection, Firm Bankruptcy Prediction, and VIP E-Mail Behavior Analysis.  相似文献   
42.
Hedonic digital artifacts have become prevalent in today's society. Their users typically pay for them, and in exchange are generally provided with benefits involving enjoyment. Today's research on technology adoption and use, though, has focused mostly on organizational or personal aids that provide efficiency and effectiveness and are free of charge for users. To bridge this gap, we identified several value drivers of hedonic digital artifacts and measured them in the context of mobile phone ringtones using the theory of consumption values. Hypothesis testing was performed using PLS on data collected from 422 ringtone users. Results confirmed that the overall value of hedonic digital artifacts is a third-order composite assessment, which successfully predicted behavioral usage and positive word-of-mouth intentions. Theoretical and practical implications were discussed.  相似文献   
43.
This paper proposes a clustering asset allocation scheme which provides better risk-adjusted portfolio performance than those obtained from traditional asset allocation approaches such as the equal weight strategy and the Markowitz minimum variance allocation. The clustering criterion used, which involves maximization of the in-sample Sharpe ratio (SR), is different from traditional clustering criteria reported in the literature. Two evolutionary methods, namely Differential Evolution and Genetic Algorithm, are employed to search for such an optimal clustering structure given a cluster number. To explore the clustering impact on the SR, the in-sample and the out-of-sample SR distributions of the portfolios are studied using bootstrapped data as well as simulated paths from the single index market model. It was found that the SR distributions of the portfolios under the clustering asset allocation structure have higher mean values and skewness but approximately the same standard deviation and kurtosis than those in the non-clustered case. Genetic Algorithm is suggested as a more efficient approach than Differential Evolution for the purpose of solving the clustering problem.  相似文献   
44.
We present a wide range of fuzzy induced generalized aggregation operators such as the fuzzy induced generalized ordered weighted averaging (FIGOWA) and the fuzzy induced quasi-arithmetic OWA (Quasi-FIOWA) operator. They are aggregation operators that use the main characteristics of the fuzzy OWA (FOWA) operator, the induced OWA (IOWA) operator and the generalized (or quasi-arithmetic) OWA operator. Therefore, they use uncertain information represented in the form of fuzzy numbers, generalized (or quasi-arithmetic) means and order inducing variables. The main advantage of these operators is that they include a wide range of mean operators such as the FOWA, the IOWA, the induced Quasi-OWA, the fuzzy IOWA, the fuzzy generalized mean and the fuzzy weighted quasi-arithmetic average (Quasi-FWA). We further generalize this approach by using Choquet integrals, obtaining the fuzzy induced quasi-arithmetic Choquet integral aggregation (Quasi-FICIA) operator. We also develop an application of the new approach in a strategic multi-person decision making problem.  相似文献   
45.
The optimal pricing decision problem of a fuzzy closed-loop supply chain with retail competition is considered in this paper. The fuzziness is associated with the customer demands, the remanufacturing cost and the collecting cost. By using game theory and fuzzy theory, the optimal decision on wholesale price, retail prices and remanufacturing rate are explored respectively under the centralized and the decentralized decision scenarios, and the expressions for them are also established. Some insights into the economic behavior of firms are given, which can serve as the basis for further study in the future.  相似文献   
46.
In this paper, regression analyses (RA) are presented for the neutronic calculation of ThO2 mixed 244CmO2 fuel with different neutronic parameters for various coolants, natural lithium, Li20Sn80 and Flinabe, respectively. The tritium breeding ratio (TBR), energy multiplication factor (M), total fission rate (Σf) and 232Th(n, γ) reaction is computed by XSDRNPM. In addition, this numerical results are estimated by RA depends on neutronic parameters and the empirical equations for neutronic performance are acquired. The results obtained by using XSDRNPM and the results of the RA, obtained empirical equations, are compared. The empirical equations indicate that RA can successfully be used for the prediction of the neutronic performance parameters in the hybrid reactor with a high degree of accuracy. In addition, correlation matrix is calculated to determined statistical relationships between variables TBR, M, Σf, and 232Th(n, γ).  相似文献   
47.
48.
本文基于复杂网络理论提出了一种评估电网发生连锁故障的新方法,运用复杂网络理论来分析电网有助于从电网架构上研究连锁故障.首先,以输电线路和变压器的阻抗模值为边权构建了电网加权拓扑模型,并给出评价电网中心性的指标;其次,基于线路断开瞬间线路传输功率优先分配到邻近线路的原则,提出评估电网发生连锁故障的阈值模型;最后,以IEEE 118节点系统为例,通过计算反映其中心性的指标值,找出了IEEE 118节点系统的中心节点,验证了加权拓扑模型在反映节点中心性方面优于无权拓扑模型,与实际网路也更接近.在此基础上,针对四种攻击网络的典型模式,运用阈值模型计算该系统发生连锁故障的临界阈值,揭示了电网发生连锁故障的机理.  相似文献   
49.
The majority of the scheduling studies carry a common assumption that machines are available all the time. However, machines may not always be available in the scheduling period due to breakdown or preventive maintenance. Taking preventive maintenance activity into consideration, we dealt with the two-machine flowshop scheduling problem with makespan objective. The preventive maintenance policy in this paper was dependent on the number of finished jobs. The integer programming model was proposed. We combined two recent constructive heuristics, HI algorithm and H algorithm, with Johnson’s algorithm, and named the combined heuristic H&J algorithm. We also developed a constructive heuristic, HD, with time complexities O(n2). Based on the difference in job processing times on two machines, both H&J and HD showed good performance, and the latter was slightly better. The HD algorithm was able to obtain the optimality in 98.88% of cases. We also employed the branch and bound (B&B) algorithm to obtain the optimum. With a good upper bound and a modified lower bound, the proposed B&B algorithm performed significantly effectively.  相似文献   
50.
Case-based reasoning (CBR) is one of the most popular prediction techniques in medical domains because it is easy to apply, has no possibility of overfitting, and provides a good explanation for the output. However, it has a critical limitation – its prediction performance is generally lower than other AI techniques like artificial neural networks (ANN). In order to obtain accurate results from CBR, effective retrieval and matching of useful prior cases for the problem is essential, but it is still a controversial issue to design a good matching and retrieval mechanism for CBR systems. In this study, we propose a novel approach to enhance the prediction performance of CBR. Our suggestion is the simultaneous optimization of feature weights, instance selection, and the number of neighbors that combine using genetic algorithms (GA). Our model improves the prediction performance in three ways – (1) measuring similarity between cases more accurately by considering relative importance of each feature, (2) eliminating useless or erroneous reference cases, and (3) combining several similar cases represent significant patterns. To validate the usefulness of our model, this study applied it to a real-world case for evaluating cytological features derived directly from a digital scan of breast fine needle aspirate (FNA) slides. Experimental results showed that the prediction accuracy of conventional CBR may be improved significantly by using our model. We also found that our proposed model outperformed all the other optimized models for CBR using GA.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号