全文获取类型
收费全文 | 310917篇 |
免费 | 33807篇 |
国内免费 | 18658篇 |
专业分类
电工技术 | 63748篇 |
技术理论 | 18篇 |
综合类 | 30255篇 |
化学工业 | 20632篇 |
金属工艺 | 9426篇 |
机械仪表 | 22558篇 |
建筑科学 | 24885篇 |
矿业工程 | 9857篇 |
能源动力 | 15565篇 |
轻工业 | 14241篇 |
水利工程 | 10833篇 |
石油天然气 | 11517篇 |
武器工业 | 3281篇 |
无线电 | 30055篇 |
一般工业技术 | 21712篇 |
冶金工业 | 9027篇 |
原子能技术 | 5108篇 |
自动化技术 | 60664篇 |
出版年
2024年 | 892篇 |
2023年 | 3709篇 |
2022年 | 7418篇 |
2021年 | 9214篇 |
2020年 | 9844篇 |
2019年 | 8106篇 |
2018年 | 7589篇 |
2017年 | 9938篇 |
2016年 | 11456篇 |
2015年 | 12704篇 |
2014年 | 20967篇 |
2013年 | 19349篇 |
2012年 | 23968篇 |
2011年 | 26185篇 |
2010年 | 19182篇 |
2009年 | 19344篇 |
2008年 | 19042篇 |
2007年 | 22457篇 |
2006年 | 19508篇 |
2005年 | 16398篇 |
2004年 | 13754篇 |
2003年 | 11565篇 |
2002年 | 9090篇 |
2001年 | 7482篇 |
2000年 | 6364篇 |
1999年 | 4953篇 |
1998年 | 3957篇 |
1997年 | 3284篇 |
1996年 | 2807篇 |
1995年 | 2314篇 |
1994年 | 2020篇 |
1993年 | 1434篇 |
1992年 | 1273篇 |
1991年 | 943篇 |
1990年 | 762篇 |
1989年 | 667篇 |
1988年 | 532篇 |
1987年 | 375篇 |
1986年 | 315篇 |
1985年 | 319篇 |
1984年 | 359篇 |
1983年 | 341篇 |
1982年 | 290篇 |
1981年 | 145篇 |
1980年 | 119篇 |
1979年 | 105篇 |
1978年 | 74篇 |
1977年 | 70篇 |
1976年 | 58篇 |
1959年 | 48篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
针对异构计算节点组成的大规模多状态计算系统的容错性能分析问题,提出了一种计算系统容错性能的评估方法。该方法采用自定义的两级容错性能形式化描述框架进行系统描述,通过构造多值决策图(Multi-value Decision Diagram,MDD)模型对系统进行容错性能建模,并基于构造的模型高效地计算出部件故障的条件下计算系统在特定性能水平上运行的概率,减少了计算的冗余性。实验结果表明,该方法在模型的大小和构建时间上均优于传统方法。该方法的提出将对系统操作员或程序设计者具有重要意义,使其确保系统适合预期应用。 相似文献
52.
AbstractData mining techniques have been successfully utilized in different applications of significant fields, including medical research. With the wealth of data available within the health-care systems, there is a lack of practical analysis tools to discover hidden relationships and trends in data. The complexity of medical data that is unfavorable for most models is a considerable challenge in prediction. The ability of a model to perform accurately and efficiently in disease diagnosis is extremely significant. Thus, the model must be selected to fit the data better, such that the learning from previous data is most efficient, and the diagnosis of the disease is highly accurate. This work is motivated by the limited number of regression analysis tools for multivariate counts in the literature. We propose two regression models for count data based on flexible distributions, namely, the multinomial Beta-Liouville and multinomial scaled Dirichlet, and evaluated the proposed models in the problem of disease diagnosis. The performance is evaluated based on the accuracy of the prediction which depends on the nature and complexity of the dataset. Our results show the efficiency of the two proposed regression models where the prediction performance of both models is competitive to other previously used regression models for count data and to the best results in the literature. 相似文献
53.
Topic modeling is a popular analytical tool for evaluating data. Numerous methods of topic modeling have been developed which consider many kinds of relationships and restrictions within datasets; however, these methods are not frequently employed. Instead many researchers gravitate to Latent Dirichlet Analysis, which although flexible and adaptive, is not always suited for modeling more complex data relationships. We present different topic modeling approaches capable of dealing with correlation between topics, the changes of topics over time, as well as the ability to handle short texts such as encountered in social media or sparse text data. We also briefly review the algorithms which are used to optimize and infer parameters in topic modeling, which is essential to producing meaningful results regardless of method. We believe this review will encourage more diversity when performing topic modeling and help determine what topic modeling method best suits the user needs. 相似文献
54.
Traditionally, in supervised machine learning, (a significant) part of the available data (usually 50%-80%) is used for training and the rest—for validation. In many problems, however, the data are highly imbalanced in regard to different classes or does not have good coverage of the feasible data space which, in turn, creates problems in validation and usage phase. In this paper, we propose a technique for synthesizing feasible and likely data to help balance the classes as well as to boost the performance in terms of confusion matrix as well as overall. The idea, in a nutshell, is to synthesize data samples in close vicinity to the actual data samples specifically for the less represented (minority) classes. This has also implications to the so-called fairness of machine learning. In this paper, we propose a specific method for synthesizing data in a way to balance the classes and boost the performance, especially of the minority classes. It is generic and can be applied to different base algorithms, for example, support vector machines, k-nearest neighbour classifiers deep neural, rule-based classifiers, decision trees, and so forth. The results demonstrated that (a) a significantly more balanced (and fair) classification results can be achieved and (b) that the overall performance as well as the performance per class measured by confusion matrix can be boosted. In addition, this approach can be very valuable for the cases when the number of actual available labelled data is small which itself is one of the problems of the contemporary machine learning. 相似文献
55.
Data and software are nowadays one and the same: for this very reason, the European Union (EU) and other governments introduce frameworks for data protection — a key example being the General Data Protection Regulation (GDPR). However, GDPR compliance is not straightforward: its text is not written by software or information engineers but rather, by lawyers and policy-makers. As a design aid to information engineers aiming for GDPR compliance, as well as an aid to software users’ understanding of the regulation, this article offers a systematic synthesis and discussion of it, distilled by the mathematical analysis method known as Formal Concept Analysis (FCA). By its principles, GDPR is synthesised as a concept lattice, that is, a formal summary of the regulation, featuring 144372 records — its uses are manifold. For example, the lattice captures so-called attribute implications, the implicit logical relations across the regulation, and their intensity. These results can be used as drivers during systems and services (re-)design, development, operation, or information systems’ refactoring towards more GDPR consistency. 相似文献
56.
By leveraging the secret data coding using the remainder storage based exploiting modification direction (RSBEMD), and the pixel change operation recording based on multi-segment left and right histogram shifting, a novel reversible data hiding (RHD) scheme is proposed in this paper. The secret data are first encoded by some specific pixel change operations to the pixels in groups. After that, multi-segment left and right histogram shifting based on threshold manipulation is implemented for recording the pixel change operations. Furthermore, a multiple embedding policy based on chess board prediction (CBP) and threshold manipulation is put forward, and the threshold can be adjusted to achieve adaptive data hiding. Experimental results and analysis show that it is reversible and can achieve good performance in capacity and imperceptibility compared with the existing methods. 相似文献
57.
58.
59.
60.
Transmission system restoration with co-optimization of repairs,load pickups,and generation dispatch
This paper studies the restoration of a transmission system after a significant disruption such as a natural disaster. It considers the co-optimization of repairs, load pickups, and generation dispatch to produce a sequencing of the repairs that minimizes the size of the blackout over time. The core of this process is a Restoration Ordering Problem (ROP), a non-convex mixed-integer nonlinear program that is outside the capabilities of existing solver technologies. To address this computational barrier, the paper examines two approximations of the power flow equations: The DC model and the recently proposed LPAC model. Systematic, large-scale testing indicates that the DC model is not sufficiently accurate for solving the ROP. In contrast, the LPAC power flow model, which captures line losses, reactive power, and voltage magnitudes, is sufficiently accurate to obtain restoration plans that can be converted into AC-feasible power flows. An experimental study also suggests that the LPAC model provides a robust and appealing tradeoff between accuracy and computational performance for solving the ROP. 相似文献