全文获取类型
收费全文 | 35425篇 |
免费 | 2366篇 |
国内免费 | 1038篇 |
专业分类
电工技术 | 1506篇 |
技术理论 | 4篇 |
综合类 | 1570篇 |
化学工业 | 6102篇 |
金属工艺 | 1582篇 |
机械仪表 | 1733篇 |
建筑科学 | 1703篇 |
矿业工程 | 764篇 |
能源动力 | 1199篇 |
轻工业 | 2243篇 |
水利工程 | 457篇 |
石油天然气 | 1027篇 |
武器工业 | 146篇 |
无线电 | 5468篇 |
一般工业技术 | 5112篇 |
冶金工业 | 2767篇 |
原子能技术 | 399篇 |
自动化技术 | 5047篇 |
出版年
2024年 | 105篇 |
2023年 | 455篇 |
2022年 | 877篇 |
2021年 | 1210篇 |
2020年 | 946篇 |
2019年 | 812篇 |
2018年 | 909篇 |
2017年 | 961篇 |
2016年 | 875篇 |
2015年 | 1080篇 |
2014年 | 1432篇 |
2013年 | 2141篇 |
2012年 | 2003篇 |
2011年 | 2332篇 |
2010年 | 1852篇 |
2009年 | 1906篇 |
2008年 | 1945篇 |
2007年 | 1753篇 |
2006年 | 1588篇 |
2005年 | 1269篇 |
2004年 | 1120篇 |
2003年 | 1197篇 |
2002年 | 1410篇 |
2001年 | 1188篇 |
2000年 | 832篇 |
1999年 | 717篇 |
1998年 | 986篇 |
1997年 | 697篇 |
1996年 | 581篇 |
1995年 | 484篇 |
1994年 | 390篇 |
1993年 | 336篇 |
1992年 | 257篇 |
1991年 | 224篇 |
1990年 | 228篇 |
1989年 | 203篇 |
1988年 | 173篇 |
1987年 | 153篇 |
1986年 | 129篇 |
1985年 | 127篇 |
1984年 | 110篇 |
1983年 | 75篇 |
1982年 | 70篇 |
1981年 | 59篇 |
1980年 | 81篇 |
1979年 | 49篇 |
1978年 | 60篇 |
1977年 | 58篇 |
1976年 | 76篇 |
1975年 | 43篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
Sentiment-oriented contextual advertising 总被引:2,自引:2,他引:0
Web advertising (Online advertising), a form of advertising that uses the World Wide Web to attract customers, has become
one of the world’s most important marketing channels. This paper addresses the mechanism of Content-based advertising (Contextual advertising), which refers to the assignment of relevant ads to a generic web page, e.g., a blog post. As blogs become a platform for
expressing personal opinion, they naturally contain various kinds of expressions, including both facts and comments of both
a positive and negative nature. Besides, in line with the major tenet of Web 2.0 (i.e., user-centric), we believe that the web-site owners would be willing to be in charge of the ads which are positively related to their contents.
Hence, in this paper, we propose the utilization of sentiment detection to improve Web-based contextual advertising. The proposed
sentiment-oriented contextual advertising (SOCA) framework aims to combine contextual advertising matching with sentiment
analysis to select ads that are related to the positive (and neutral) aspects of a blog and rank them according to their relevance.
We experimentally validate our approach using a set of data that includes both real ads and actual blog pages. The results
indicate that our proposed method can effectively identify those ads that are positively correlated with the given blog pages. 相似文献
93.
Logistic regression in sealed-bid auctions with multiple rounds: Application in Korean court auction
This paper proposes a forecasting method for court auction information system using logistic regression model with heterogeneity across the multiple round. The goal is to predict whether an individual auction item in a certain round will be sold or not. A simple linear regression and the least angle regression (LARS) containing random effect terms were used to select meaningful variables for our logit model. The link function of the proposed logit model is represented by two bundles of parameters. The former part consists of the parameters whose values do not change over rounds. The latter part has parameters whose values interact with rounds. The observed data corresponding to an appraiser price as well as an intercept term reflecting local characteristics are used without any change. Data that corresponds to all the other parameters is not directly used, but transformed based on similarities between the original item and the surrounding auction items being recommended by the court auction experts. We tested the Bayesian logistic regression by establishing different priors: Dunson’s prior, Gelman’s prior and Ansari’s prior. Dunson’s prior was found to perform the best. Little significant difference was found between the results of the other two priors. These findings indicate that logistic regression taking the heterogeneity of multi-round into account performs better than a one-layered neural network over all time periods. 相似文献
94.
Dong-Xia Chang Author Vitae Xian-Da Zhang Author Vitae Author Vitae 《Pattern recognition》2009,42(7):1210-1987
In this paper, a new clustering algorithm based on genetic algorithm (GA) with gene rearrangement (GAGR) is proposed, which in application may effectively remove the degeneracy for the purpose of a more efficient search. A new crossover operator that exploits a measure of similarity between chromosomes in a population is also presented. Adaptive probabilities of crossover and mutation are employed to prevent the convergence of the GAGR to a local optimum. Using the real-world data sets, we compare the performance of our GAGR clustering algorithm with K-means algorithm and other GA methods. An application of the GAGR clustering algorithm in unsupervised classification of multispectral remote sensing images is also provided. Experiment results demonstrate that the GAGR clustering algorithm has high performance, effectiveness and flexibility. 相似文献
95.
96.
The electronic structures of quasi-one-dimensional ferrimagnetic Ca3Co2O6 are investigated using the generalized gradient approximation (GGA) as well as the GGA plus on-site Coulomb interaction (GGA+U) scheme. GGA+U calculations reveal that the interchain ferrimagnetic Ca3Co2O6 is a Mott–Hubbard insulator rather than a metal given from GGA. In addition, we found an on-site U induced 3z2−r2 orbital ordering on Copri sublattice which drives the intrachain ferromagnetic coupling along c-axis. Our findings suggest that strong electron-electron correlation plays an important role in Ca3Co2O6. 相似文献
97.
In this paper, prediction of axial and hoop residual stresses produced in high strength carbon steel pipe weld was made by employing a sequentially coupled 3-D thermal, metallurgical and mechanical FE model. Solid-state phase transformation during welding was incorporated into the FE model by allowing for volumetric changes and the associated changes in yield stress induced by austenitic and martensitic transformations. In the FE model, temperature-dependent thermo-physical and mechanical properties were considered, and phase transformation plasticity was also taken into account. The results showed the importance of incorporating solid-state phase transformation in the simulation of the pipe welding. 相似文献
98.
The model-based human body motion analysis system 总被引:3,自引:0,他引:3
In this paper, we propose a model-based method to analyze the human walking motion. This system consists of three phases: the preprocessing phase, the model construction phase, and the motion analysis phase. In the experimental results, we show that our system not only analyzes the motion characteristics of the human body, but also recognizes the motion type of the input image sequences. Finally, the synthesized motion sequences are illustrated for verification. The major contributions of this research are: (1) developing a skeleton-based method to analyze the human motion; (2) using Hidden Markov Model (HMM) and posture patterns to describe the motion type. 相似文献
99.
Chih-Lyang Hwang Li-Jui Chang 《Fuzzy Systems, IEEE Transactions on》2008,16(5):1271-1284
100.