全文获取类型
收费全文 | 2522篇 |
免费 | 347篇 |
国内免费 | 248篇 |
学科分类
工业技术 | 3117篇 |
出版年
2024年 | 4篇 |
2023年 | 42篇 |
2022年 | 52篇 |
2021年 | 54篇 |
2020年 | 82篇 |
2019年 | 76篇 |
2018年 | 74篇 |
2017年 | 84篇 |
2016年 | 129篇 |
2015年 | 123篇 |
2014年 | 173篇 |
2013年 | 216篇 |
2012年 | 183篇 |
2011年 | 198篇 |
2010年 | 161篇 |
2009年 | 167篇 |
2008年 | 166篇 |
2007年 | 184篇 |
2006年 | 145篇 |
2005年 | 106篇 |
2004年 | 116篇 |
2003年 | 92篇 |
2002年 | 70篇 |
2001年 | 38篇 |
2000年 | 46篇 |
1999年 | 37篇 |
1998年 | 32篇 |
1997年 | 40篇 |
1996年 | 27篇 |
1995年 | 27篇 |
1994年 | 22篇 |
1993年 | 22篇 |
1992年 | 19篇 |
1991年 | 19篇 |
1990年 | 12篇 |
1989年 | 18篇 |
1988年 | 8篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1982年 | 4篇 |
1978年 | 2篇 |
1973年 | 2篇 |
1966年 | 4篇 |
1965年 | 2篇 |
1962年 | 2篇 |
1960年 | 2篇 |
1958年 | 2篇 |
1957年 | 4篇 |
排序方式: 共有3117条查询结果,搜索用时 343 毫秒
101.
102.
基于颜色和纹理特征的林火烟雾识别 总被引:1,自引:0,他引:1
为了实现森林火灾的智能化预警,提出了基于颜色和纹理特征的林火烟雾识别方法.首先使用颜色特征确定烟雾疑似区域,随后采用局部二值模式方差(Local Binary Pattern Variance,LBPV)提取疑似区域纹理的不规则度特征并产生LBP图像.然后利用小波变换分解LBP图像并提取模糊度、复杂度和相关度特征.最后利用支持向量机(Support Vector Machine,SVM)进行烟雾识别.结果证明,颜色结合纹理特征方法可以有效实现林火烟雾的识别,为林火烟雾识别研究提供了一种有效方案. 相似文献
103.
104.
针对某型MEMS陀螺随机误差较大、精度不高的问题,通过时间序列分析法,建立自回归滑动平均 ARMA(Auto-Regressive and Moving Average)模型,采用ARMA(2,1)模型将预处理后的MEMS陀螺随机误差进行建模.设计基于ARMA模型的经典Kalman滤波器.静态试验和恒定速率试验结果表明在经典Kalman滤波器作用下,静态试验下其均值与均方差下降32.62%和66.31%;恒定速率试验下,其均值有明显的降低,其均方差减小了一个数量级.针对经典Kalman滤波器不能解决振动试验中大振幅时滤波发散问题,提出一种新的自适应Kalman滤波法,通过寻找合适的标定因子s解决滤波发散问题.振动试验结果表明,当振幅为100°时,滤波后的均值和均方差分别下降8.25%和8.36%. 相似文献
105.
106.
Target sales rebate (TSR) contracts have been shown to be useful in coordinating supply chains with risk-neutral agents. However, there have been few studies on the cases with risk sensitive agents. As a result, based on the classic Markowitz portfolio theory in finance, we carry out in this paper a mean–variance (MV) analysis of supply chains under TSR contracts. We study a supply chain with a single supplier and a single risk averse retailer. We propose TSR contracts for achieving coordination. We demonstrate how TSR contracts can coordinate the supply chain which takes into consideration the degree of risk aversion of the retailer. We find that the supplier can coordinate the channel with flexible TSR contracts. In addition, we extend the supply chain model to include sales effort decision of the retailer. Conditions for TSR contracts to coordinate the supply chain with sales effort of retailer are also derived. 相似文献
107.
Giacomo Veneri Pietro PiuFrancesca Rosini Pamela Federighi Antonio FedericoAlessandra Rufa 《Pattern recognition letters》2011,32(13):1588-1593
Eye movement is the simplest and repetitive movement that enables humans to interact with the environment. The common daily activities, such as reading a book or watching television, involve this natural activity, which consists of rapidly shifting our gaze from one region to another. In clinical application, the identification of the main components of eye movement during visual exploration, such as fixations and saccades, is the objective of the analysis of eye movements: however, in patients affected by motor control disorder the identification of fixation is not banal. This work presents a new fixation identification algorithm based on the analysis of variance and covariance: the main idea was to use bivariate statistical analysis to compare variance over x and y to identify fixation. We describe the new algorithm, and we compare it with the common fixations algorithm based on dispersion. To demonstrate the performance of our approach, we tested the algorithm in a group of healthy subjects and patients affected by motor control disorder. 相似文献
108.
We study comparisons of several treatments with a common control when it is believed a priori that the treatment means, μi, are at least as large as the control mean, μ0. In this setting, which is called a tree ordering, we study multiple comparisons that determine whether μi>μ0 or μi=μ0 for each treatment. The classical procedure by Dunnett (1955) and the step-down and step-up techniques by
[Dunnett and Tamhane, 1991] and [Dunnett and Tamhane, 1992] are well known. The results in Marcus and Talpaz (1992) provide multiple comparisons based on the maximum likelihood estimates restricted by the tree ordering. We also study two-stage procedures that consist of the likelihood ratio test of homogeneity with the alternative constrained by the tree ordering followed by two-sample t comparisons with possibly different critical values for the two-sample comparisons. Marcus et al. (1976) discuss the use of closed tests in such situations and propose using a closed version of the restricted likelihood ratio test. We describe step-down versions of the Marcus-Talpaz, the two-stage, and the likelihood ratio procedures, as well as a closed version of the Marcus-Talpaz multiple comparison procedure. Using Monte Carlo techniques, we study the familywise errors and powers of these procedures and make some recommendations concerning techniques that perform well for all tree ordered mean vectors. 相似文献
109.
Rong ZhuSherry Z.F. Zhou 《Computational statistics & data analysis》2011,55(7):2312-2323
This paper considers the estimation of the error variance after a pre-test of an interval restriction on the coefficients. We derive the exact finite sample risks of the interval restricted and pre-test estimators of the error variance, and examine the risk properties of the estimators to model misspecification through the omission of relevant regressors. It is found that the pre-test estimator performs better than the interval restricted estimator in terms of the risk properties in a large region of the parameter space; moreover, its risk performance is more robust with respect to the degrees of model misspecification. Furthermore, we propose a bootstrap procedure for estimating the risks of the estimators, to overcome the difficulty of computing the exact risks. 相似文献
110.