全文获取类型
收费全文 | 1144篇 |
免费 | 59篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 18篇 |
化学工业 | 305篇 |
金属工艺 | 11篇 |
机械仪表 | 26篇 |
建筑科学 | 28篇 |
能源动力 | 45篇 |
轻工业 | 66篇 |
水利工程 | 4篇 |
石油天然气 | 1篇 |
无线电 | 163篇 |
一般工业技术 | 212篇 |
冶金工业 | 108篇 |
原子能技术 | 2篇 |
自动化技术 | 215篇 |
出版年
2023年 | 15篇 |
2022年 | 45篇 |
2021年 | 69篇 |
2020年 | 35篇 |
2019年 | 34篇 |
2018年 | 30篇 |
2017年 | 25篇 |
2016年 | 52篇 |
2015年 | 20篇 |
2014年 | 44篇 |
2013年 | 79篇 |
2012年 | 58篇 |
2011年 | 87篇 |
2010年 | 67篇 |
2009年 | 72篇 |
2008年 | 68篇 |
2007年 | 53篇 |
2006年 | 43篇 |
2005年 | 57篇 |
2004年 | 20篇 |
2003年 | 22篇 |
2002年 | 17篇 |
2001年 | 9篇 |
2000年 | 14篇 |
1999年 | 6篇 |
1998年 | 28篇 |
1997年 | 21篇 |
1996年 | 24篇 |
1995年 | 14篇 |
1994年 | 11篇 |
1993年 | 14篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 2篇 |
排序方式: 共有1204条查询结果,搜索用时 31 毫秒
91.
Spatial contagion between two financial markets X and Y appears when there is more dependence between X and Y when they are doing badly than when they exhibit typical performance. In this paper, we introduce an index to measure the contagion effects. This tool is based on the use of suitable copulas associated with the markets and on the calculation of the related conditional Spearman's correlation coefficients. As an empirical application, the proposed index is used to create a clustering of European stock market indices to assess their behavior in the recent years. The whole procedure is expected to be useful for portfolio diversification in crisis periods. 相似文献
92.
We present a new multiclass algorithm in the bandit framework, where after making a prediction, the learning algorithm receives only partial feedback, i.e., a single bit indicating whether the predicted label is correct or not, rather than the true label. Our algorithm is based on the second-order Perceptron, and uses upper-confidence bounds to trade-off exploration and exploitation, instead of random sampling as performed by most current algorithms. We analyze this algorithm in a partial adversarial setting, where instances are chosen adversarially, while the labels are chosen according to a linear probabilistic model which is also chosen adversarially. We show a regret of $\mathcal{O}(\sqrt{T}\log T)$ , which improves over the current best bounds of $\mathcal{O}(T^{2/3})$ in the fully adversarial setting. We evaluate our algorithm on nine real-world text classification problems and on four vowel recognition tasks, often obtaining state-of-the-art results, even compared with non-bandit online algorithms, especially when label noise is introduced. 相似文献
93.
Stefano Baccianella Andrea Esuli Fabrizio Sebastiani 《Expert systems with applications》2013,40(11):4687-4696
Most popular feature selection methods for text classification such as information gain (also known as “mutual information”), chi-square, and odds ratio, are based on binary information indicating the presence/absence of the feature (or “term”) in each training document. As such, these methods do not exploit a rich source of information, namely, the information concerning how frequently the feature occurs in the training document (term frequency). In order to overcome this drawback, when doing feature selection we logically break down each training document of length k into k training “micro-documents”, each consisting of a single word occurrence and endowed with the same class information of the original training document. This move has the double effect of (a) allowing all the original feature selection methods based on binary information to be still straightforwardly applicable, and (b) making them sensitive to term frequency information. We study the impact of this strategy in the case of ordinal text classification, a type of text classification dealing with classes lying on an ordinal scale, and recently made popular by applications in customer relationship management, market research, and Web 2.0 mining. We run experiments using four recently introduced feature selection functions, two learning methods of the support vector machines family, and two large datasets of product reviews. The experiments show that the use of this strategy substantially improves the accuracy of ordinal text classification. 相似文献
94.
Optimal resource assignment through negotiation in a multi-agent manufacturing system 总被引:5,自引:0,他引:5
Research studies on multi-agent systems have been recently boosted by manufacturing and logistics with deep motivations like the presence of independent human deciders with individual goals, the aspiration to dominate the complexity of decision-making in large organizations, the simplicity and robustness of self-reacting distributed systems. After a survey of the multi-agent paradigm and its applications, the paper introduces the notion of hybrid holonic system to study the effect of supervision on a system whose elements negotiate and cooperate in a rule-settled environment to obtain resources for system operation. The supervisor can spur or disincentive agents by assigning/denying resources to them. A simple single-decider optimization model referred to a real application is described, and solution methodologies for optimal resource allocation fitting different scenarios (centralized, distributed, multi-agent) are discussed, identifying ranges of autonomy, quantifying rewarding and defining a negotiation protocol between the agents and the supervisor. Aim of the paper is to describe through an example a general methodology for quantitative decision-making in multi-agent organizations. 相似文献
95.
Anna Bernasconi Valentina Ciriani Fabrizio Luccio Linda Pagli 《Theory of Computing Systems》2008,42(4):450-464
Autosymmetric functions exhibit a special type of regularity that can speed-up the minimization process. Based on this autosymmetry,
we propose a three level form of logic synthesis, called ORAX (EXOR-AND-OR), to be compared with the standard minimal SOP
(Sum of Products) form.
First we provide a fast ORAX minimization algorithm for autosymmetric functions. The ORAX network for a function f has a first level of at most 2(n−k) EXOR gates, followed by the AND-OR levels, where n is the number of input variables and k is the “autosymmetry degree” of f. In general a minimal ORAX form has smaller size than a standard minimal SOP form for the same function. We show how the
gain in area of ORAX over SOP can be measured without explicitly generating the latter. If preferred, a SOP expression can
be directly derived from the corresponding ORAX. A set of experimental results confirms that the ORAX form is generally more
compact than the SOP form, and its synthesis is much faster than classical three-level logic minimization. Indeed ORAX and
SOP minimization times are often comparable, and in some cases ORAX synthesis is even faster. 相似文献
96.
Sueva Cantalupo Vito Alessandro Lasorsa Roberta Russo Immacolata Andolfo Giuseppe DAlterio Barbara Eleni Rosato Giulia Frisso Pasquale Abete Gian Marco Cassese Giuseppe Servillo Ivan Gentile Carmelo Piscopo Matteo Della Monica Giuseppe Fiorentino Giuseppe Russo Pellegrino Cerino Carlo Buonerba Biancamaria Pierri Massimo Zollo Achille Iolascon Mario Capasso 《International journal of molecular sciences》2021,22(10)
Genome-wide association studies (GWAS) found locus 3p21.31 associated with severe COVID-19. CCR5 resides at the same locus and, given its known biological role in other infection diseases, we investigated if common noncoding and rare coding variants, affecting CCR5, can predispose to severe COVID-19. We combined single nucleotide polymorphisms (SNPs) that met the suggestive significance level (P ≤ 1 × 10−5) at the 3p21.31 locus in public GWAS datasets (6406 COVID-19 hospitalized patients and 902,088 controls) with gene expression data from 208 lung tissues, Hi-C, and Chip-seq data. Through whole exome sequencing (WES), we explored rare coding variants in 147 severe COVID-19 patients. We identified three SNPs (rs9845542, rs12639314, and rs35951367) associated with severe COVID-19 whose risk alleles correlated with low CCR5 expression in lung tissues. The rs35951367 resided in a CTFC binding site that interacts with CCR5 gene in lung tissues and was confirmed to be associated with severe COVID-19 in two independent datasets. We also identified a rare coding variant (rs34418657) associated with the risk of developing severe COVID-19. Our results suggest a biological role of CCR5 in the progression of COVID-19 as common and rare genetic variants can increase the risk of developing severe COVID-19 by affecting the functions of CCR5. 相似文献
97.
The conversion of biomass into biofuels can reduce the strategic vulnerability of petroleum-based transportation systems. Bioethanol has received considerable attention over the last years as a fuel extender or even as a neat liquid fuel. Lignocellulosic materials are very attractive substrates for the production of bioethanol because of their low cost and their great potential availability. Two different process alternatives (i.e. the enzymatic hydrolysis and fermentation process and the gasification and fermentation process) for the production of fuel ethanol from lignocellulosic feedstock are considered and analysed. After a rigorous mass and energy balance, design optimisation is carried out. Both processes are assessed in terms of ethanol yield and power generation as well as from a financial point of view. A sensitivity analysis on critical parameters of the processes' productivity and profitability is performed. 相似文献
98.
99.
An innovative system for thermoplastic micromolding is presented. A completely transparent mold is used, and a diode laser is used as heating source. Laser heating is performed on a single thermoplastic pellet positioned inside the mold between two glass plates. A very low force is necessary for shaping. Molding tests were performed on commercial ABS and several process parameters were investigated such as laser power, interaction time, focalization condition, and support material properties. High pellet formability was observed in all the cases. Using nontransparent pellet supports it is possible to increase molding efficiency even if the risk of polymer degradation increases. A master curve can be fabricated for molding test results providing a correct comparison among the different process conditions. POLYM. ENG. SCI., 47:168–173, 2007. © 2007 Society of Plastics Engineers 相似文献
100.