全文获取类型
收费全文 | 1911篇 |
免费 | 255篇 |
国内免费 | 154篇 |
专业分类
电工技术 | 135篇 |
综合类 | 169篇 |
化学工业 | 81篇 |
金属工艺 | 38篇 |
机械仪表 | 37篇 |
建筑科学 | 157篇 |
矿业工程 | 18篇 |
能源动力 | 75篇 |
轻工业 | 76篇 |
水利工程 | 97篇 |
石油天然气 | 20篇 |
武器工业 | 5篇 |
无线电 | 162篇 |
一般工业技术 | 160篇 |
冶金工业 | 333篇 |
原子能技术 | 17篇 |
自动化技术 | 740篇 |
出版年
2024年 | 5篇 |
2023年 | 22篇 |
2022年 | 38篇 |
2021年 | 46篇 |
2020年 | 36篇 |
2019年 | 42篇 |
2018年 | 54篇 |
2017年 | 61篇 |
2016年 | 79篇 |
2015年 | 75篇 |
2014年 | 108篇 |
2013年 | 115篇 |
2012年 | 114篇 |
2011年 | 177篇 |
2010年 | 141篇 |
2009年 | 156篇 |
2008年 | 147篇 |
2007年 | 157篇 |
2006年 | 134篇 |
2005年 | 148篇 |
2004年 | 104篇 |
2003年 | 91篇 |
2002年 | 71篇 |
2001年 | 45篇 |
2000年 | 23篇 |
1999年 | 32篇 |
1998年 | 14篇 |
1997年 | 11篇 |
1996年 | 10篇 |
1995年 | 6篇 |
1994年 | 12篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1974年 | 1篇 |
1965年 | 1篇 |
1964年 | 1篇 |
1963年 | 2篇 |
1962年 | 1篇 |
1959年 | 1篇 |
1956年 | 1篇 |
1955年 | 2篇 |
排序方式: 共有2320条查询结果,搜索用时 15 毫秒
61.
结合半监督学习和集成学习方法,提出了一种基于置信度重取样的SemiBoost-CR分类模型.给出了基于标注近邻与未标注近邻的置信度计算公式,按照置信度重采样,不仅选取一定比例置信度较高的未标注样本,而且选取一定比例置信度较低的未标注样本,分别以不同的策略加入到已标注的训练样本集,引入置信度高的未标注样本,用以提高基分类... 相似文献
62.
63.
Fabien Tricoire Martin Romauch Karl F. Doerner Richard F. Hartl 《Computers & Operations Research》2010,37(2):351-367
We present the multi-period orienteering problem with multiple time windows (MuPOPTW), a new routing problem combining objective and constraints of the orienteering problem (OP) and team orienteering problem (TOP), constraints from standard vehicle routing problems, and original constraints from a real-world application. The problem itself comes from a real industrial case. Specific route duration constraints result in a route feasibility subproblem. We propose an exact algorithm for this subproblem, and we embed it in a variable neighborhood search method to solve the whole routing problem. We then provide experimental results for this method. We compare them to a commercial solver. We also adapt our method to standard benchmark OP and TOP instances, and provide comparative tables with state-of-the-art algorithms. 相似文献
64.
65.
66.
67.
Feature selection for text categorization is a well-studied problem and its goal is to improve the effectiveness of categorization, or the efficiency of computation, or both. The system of text categorization based on traditional term-matching is used to represent the vector space model as a document; however, it needs a high dimensional space to represent the document, and does not take into account the semantic relationship between terms, which leads to a poor categorization accuracy. The latent semantic indexing method can overcome this problem by using statistically derived conceptual indices to replace the individual terms. With the purpose of improving the accuracy and efficiency of categorization, in this paper we propose a two-stage feature selection method. Firstly, we apply a novel feature selection method to reduce the dimension of terms; and then we construct a new semantic space, between terms, based on the latent semantic indexing method. Through some applications involving the spam database categorization, we find that our two-stage feature selection method performs better. 相似文献
68.
In this paper we formulate a least squares version of the recently proposed twin support vector machine (TSVM) for binary classification. This formulation leads to extremely simple and fast algorithm for generating binary classifiers based on two non-parallel hyperplanes. Here we attempt to solve two modified primal problems of TSVM, instead of two dual problems usually solved. We show that the solution of the two modified primal problems reduces to solving just two systems of linear equations as opposed to solving two quadratic programming problems along with two systems of linear equations in TSVM. Classification using nonlinear kernel also leads to systems of linear equations. Our experiments on publicly available datasets indicate that the proposed least squares TSVM has comparable classification accuracy to that of TSVM but with considerably lesser computational time. Since linear least squares TSVM can easily handle large datasets, we further went on to investigate its efficiency for text categorization applications. Computational results demonstrate the effectiveness of the proposed method over linear proximal SVM on all the text corpuses considered. 相似文献
69.
Hypersonic vehicles (HSVs) offer great advantages over airplanes and satellites, owing to their hypersonic speeds and flexible trajectories. However, HSV-borne radar may suffer from performance degradation if traditional target integration methods with stop-and-go (SAG) approximation are applied; this is especially true for high resolution radar and applications that utilize long-time coherent integration. In this paper, we consider the effects of moving-in-pulse duration (MPD) to derive an HSV-borne radar signal model without SAG approximation by specifically characterizing platform motion during the transmission and reception of a pulse. An explicit formula for wavenumber domain echo is derived using the 2-D joint stationary phase method. To mitigate the pulse-dependent echo distortion induced by the MPD effect, a target integration method based on the omega-K algorithm is proposed; this method employs revised filters for bulk focusing and revised Stolt interpolation for differential focusing to improve the overall focusing quality. The paper discusses the ambiguity functions of in-range MPD echo models, and describes the performance metrics for the integration results in both dimensions, including impulse response width (IRW), peak sidelobe ratio (PSLR), and integrated sidelobe ratio (ISLR). Simulation results have verified the effectiveness of the proposed method in MPD circumstances. 相似文献
70.
特征降维是文本分类过程中的一个重要环节。在现有特征选择方法的基础上,综合考虑特征词在正类和负类中的分布性质,综合四种衡量特征类别区分能力的指标,提出了一个新的特征选择方法,即综合比率(CR)方法。实验采用K-最近邻分类算法(KNN)来考查CR方法的有效性,实验结果表明该方法能够取得比现有特征选择方法更优的降维效果。 相似文献