全文获取类型
收费全文 | 22220篇 |
免费 | 3913篇 |
国内免费 | 3137篇 |
专业分类
电工技术 | 1446篇 |
技术理论 | 3篇 |
综合类 | 2191篇 |
化学工业 | 725篇 |
金属工艺 | 237篇 |
机械仪表 | 896篇 |
建筑科学 | 1071篇 |
矿业工程 | 745篇 |
能源动力 | 275篇 |
轻工业 | 638篇 |
水利工程 | 409篇 |
石油天然气 | 578篇 |
武器工业 | 200篇 |
无线电 | 2608篇 |
一般工业技术 | 1539篇 |
冶金工业 | 667篇 |
原子能技术 | 81篇 |
自动化技术 | 14961篇 |
出版年
2024年 | 193篇 |
2023年 | 545篇 |
2022年 | 972篇 |
2021年 | 1125篇 |
2020年 | 1071篇 |
2019年 | 890篇 |
2018年 | 859篇 |
2017年 | 1025篇 |
2016年 | 1038篇 |
2015年 | 1222篇 |
2014年 | 1606篇 |
2013年 | 1640篇 |
2012年 | 1762篇 |
2011年 | 1918篇 |
2010年 | 1464篇 |
2009年 | 1509篇 |
2008年 | 1573篇 |
2007年 | 1645篇 |
2006年 | 1299篇 |
2005年 | 1060篇 |
2004年 | 875篇 |
2003年 | 714篇 |
2002年 | 641篇 |
2001年 | 481篇 |
2000年 | 401篇 |
1999年 | 308篇 |
1998年 | 232篇 |
1997年 | 187篇 |
1996年 | 167篇 |
1995年 | 141篇 |
1994年 | 119篇 |
1993年 | 88篇 |
1992年 | 59篇 |
1991年 | 50篇 |
1990年 | 44篇 |
1989年 | 43篇 |
1988年 | 28篇 |
1987年 | 21篇 |
1986年 | 26篇 |
1985年 | 26篇 |
1984年 | 20篇 |
1983年 | 31篇 |
1982年 | 24篇 |
1981年 | 24篇 |
1980年 | 21篇 |
1979年 | 13篇 |
1978年 | 15篇 |
1977年 | 10篇 |
1976年 | 7篇 |
1975年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
The International Society for the Study of Vascular Anomalies (ISSVA) provides a classification for vascular anomalies that enables specialists to unambiguously classify diagnoses. This classification is only available in PDF format and is not machine-readable, nor does it provide unique identifiers that allow for structured registration. In this paper, we describe the process of transforming the ISSVA classification into an ontology. We also describe the structure of this ontology, as well as two applications of the ontology using examples from the domain of rare disease research. We used the expertise of an ontology expert and clinician during the development process. We semi-automatically added mappings to relevant external ontologies using automated ontology matching systems and manual assessment by experts. The ISSVA ontology should contribute to making data for vascular anomaly research more Findable, Accessible, Interoperable, and Reusable (FAIR). The ontology is available at https://bioportal.bioontology.org/ontologies/ISSVA. 相似文献
2.
3.
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
4.
5.
6.
This paper presents an innovative solution to model distributed adaptive systems in biomedical environments. We present an original TCBR-HMM (Text Case Based Reasoning-Hidden Markov Model) for biomedical text classification based on document content. The main goal is to propose a more effective classifier than current methods in this environment where the model needs to be adapted to new documents in an iterative learning frame. To demonstrate its achievement, we include a set of experiments, which have been performed on OSHUMED corpus. Our classifier is compared with Naive Bayes and SVM techniques, commonly used in text classification tasks. The results suggest that the TCBR-HMM Model is indeed more suitable for document classification. The model is empirically and statistically comparable to the SVM classifier and outperforms it in terms of time efficiency. 相似文献
7.
In this article we illustrate a methodology for building cross-language search engine. A synergistic approach between thesaurus-based approach and corpus-based approach is proposed. First, a bilingual ontology thesaurus is designed with respect to two languages: English and Spanish, where a simple bilingual listing of terms, phrases, concepts, and subconcepts is built. Second, term vector translation is used – a statistical multilingual text retrieval techniques that maps statistical information about term use between languages (Ontology co-learning). These techniques map sets of t f id f term weights from one language to another. We also applied a query translation method to retrieve multilingual documents with an expansion technique for phrasal translation. Finally, we present our findings. 相似文献
8.
The proposed work involves the multiobjective PSO based adaption of optimal neural network topology for the classification of multispectral satellite images. It is per pixel supervised classification using spectral bands (original feature space). This paper also presents a thorough experimental analysis to investigate the behavior of neural network classifier for given problem. Based on 1050 number of experiments, we conclude that following two critical issues needs to be addressed: (1) selection of most discriminative spectral bands and (2) determination of optimal number of nodes in hidden layer. We propose new methodology based on multiobjective particle swarm optimization (MOPSO) technique to determine discriminative spectral bands and the number of hidden layer node simultaneously. The accuracy with neural network structure thus obtained is compared with that of traditional classifiers like MLC and Euclidean classifier. The performance of proposed classifier is evaluated quantitatively using Xie-Beni and β indexes. The result shows the superiority of the proposed method to the conventional one. 相似文献
9.
The Vehicle Routing Problem with Simultaneous Pickup and Delivery (VRPSPD) is an extension to the classical Vehicle Routing Problem (VRP), where customers may both receive and send goods simultaneously. The Vehicle Routing Problem with Mixed Pickup and Delivery (VRPMPD) differs from the VRPSPD in that the customers may have either pickup or delivery demand. However, the solution approaches proposed for the VRPSPD can be directly applied to the VRPMPD. In this study, an adaptive local search solution approach is developed for both the VRPSPD and the VRPMPD, which hybridizes a Simulated Annealing inspired algorithm with Variable Neighborhood Descent. The algorithm uses an adaptive threshold function that makes the algorithm self-tuning. The proposed approach is tested on well-known VRPSPD and VRPMPD benchmark instances derived from the literature. The computational results indicate that the proposed algorithm is effective in solving the problems in reasonable computation time. 相似文献
10.
Qilin Liu Feng Ding 《International Journal of Adaptive Control and Signal Processing》2021,35(10):1970-1989
The identification of the Hammerstein–Wiener (H-W) systems based on the nonuniform input–output dataset remains a challenging problem. This article studies the identification problem of a periodically nonuniformly sampled-data H-W system. In addition, the product terms of the parameters in the H-W system are inevitable. In order to solve the problem, the key-term separation is applied and two algorithms are proposed. One is the key-term-based forgetting factor stochastic gradient (KT-FFSG) algorithm based on the gradient search. The other is the key-term-based hierarchical forgetting factor stochastic gradient (KT-HFFSG) algorithm. Compared with the KT-FFSG algorithm, the KT-HFFSG algorithm gives more accurate estimates. The simulation results indicate that the proposed algorithms are effective. 相似文献