全文获取类型
收费全文 | 487篇 |
免费 | 40篇 |
国内免费 | 60篇 |
专业分类
系统科学 | 50篇 |
丛书文集 | 12篇 |
理论与方法论 | 3篇 |
现状及发展 | 42篇 |
综合类 | 477篇 |
自然研究 | 3篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 5篇 |
2021年 | 11篇 |
2020年 | 16篇 |
2019年 | 8篇 |
2018年 | 8篇 |
2017年 | 13篇 |
2016年 | 11篇 |
2015年 | 26篇 |
2014年 | 34篇 |
2013年 | 16篇 |
2012年 | 30篇 |
2011年 | 34篇 |
2010年 | 28篇 |
2009年 | 27篇 |
2008年 | 24篇 |
2007年 | 39篇 |
2006年 | 33篇 |
2005年 | 22篇 |
2004年 | 23篇 |
2003年 | 26篇 |
2002年 | 13篇 |
2001年 | 12篇 |
2000年 | 20篇 |
1999年 | 17篇 |
1998年 | 10篇 |
1997年 | 12篇 |
1996年 | 11篇 |
1995年 | 12篇 |
1994年 | 6篇 |
1993年 | 7篇 |
1992年 | 8篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1985年 | 1篇 |
排序方式: 共有587条查询结果,搜索用时 46 毫秒
161.
多维AR(p)模型的估计理论及应用 总被引:3,自引:1,他引:3
叙述了多维AR(p)模型的分析与处理方法、多维AR(p)预测模型的建模过程及参数估计的计算方法,并将该模型在测井曲线的预测中加以实际应用.应用结果表明:本预测模型对多维动态数据进行预测是可行的。 相似文献
162.
基于多维统计分析方法的脑电消噪 总被引:1,自引:0,他引:1
基于二阶统计特性的主分量分析(PCA)和基于高阶统计特性的独立分量分析(ICA)是两种非常典型的多维统计分析方法.本文对PCA和ICA基本原理进行了简单介绍,并结合脑电消噪问题,对两种方法的性能和特点进行了比较.实验结果表明,在脑电消噪和特征增强等方面,独立分量分析方法具有明显的优势. 相似文献
163.
Michael McCrae Yan‐Xia Lin Daniel Pavlik Chandra M. Gulati 《Journal of forecasting》2002,21(5):355-380
Conventional wisdom holds that restrictions on low‐frequency dynamics among cointegrated variables should provide more accurate short‐ to medium‐term forecasts than univariate techniques that contain no such information; even though, on standard accuracy measures, the information may not improve long‐term forecasting. But inconclusive empirical evidence is complicated by confusion about an appropriate accuracy criterion and the role of integration and cointegration in forecasting accuracy. We evaluate the short‐ and medium‐term forecasting accuracy of univariate Box–Jenkins type ARIMA techniques that imply only integration against multivariate cointegration models that contain both integration and cointegration for a system of five cointegrated Asian exchange rate time series. We use a rolling‐window technique to make multiple out of sample forecasts from one to forty steps ahead. Relative forecasting accuracy for individual exchange rates appears to be sensitive to the behaviour of the exchange rate series and the forecast horizon length. Over short horizons, ARIMA model forecasts are more accurate for series with moving‐average terms of order >1. ECMs perform better over medium‐term time horizons for series with no moving average terms. The results suggest a need to distinguish between ‘sequential’ and ‘synchronous’ forecasting ability in such comparisons. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
164.
165.
P. J. Harrison 《Journal of forecasting》1997,16(5):287-292
It is well known that, as calculated using the Kalman filter recurrence relationships, the posterior parameter variance and the adaptive vector of observable constant dynamic linear models converge to limiting values. However, most proofs are tortuous, some have subtle errors and some relate only to specific cases. An elegant probabilistic convergence proof demonstrates that the limit is independent of the initial parametric prior. The result is extended to a class of multivariate dynamic linear models. Finally the proof is shown to apply to many non-observable constant DLMs. © 1997 John Wiley & Sons, Ltd. 相似文献
166.
167.
168.
Modeling European industrial production with multivariate singular spectrum analysis: A cross‐industry analysis 下载免费PDF全文
In this paper, an optimized multivariate singular spectrum analysis (MSSA) approach is proposed to find leading indicators of cross‐industry relations between 24 monthly, seasonally unadjusted industrial production (IP) series for German, French, and UK economies. Both recurrent and vector forecasting algorithms of horizontal MSSA (HMSSA) are considered. The results from the proposed multivariate approach are compared with those obtained via the optimized univariate singular spectrum analysis (SSA) forecasting algorithm to determine the statistical significance of each outcome. The data are rigorously tested for normality, seasonal unit root hypothesis, and structural breaks. The results are presented such that users can not only identify the most appropriate model based on the aim of the analysis, but also easily identify the leading indicators for each IP variable in each country. Our findings show that, for all three countries, forecasts from the proposed MSSA algorithm outperform the optimized SSA algorithm in over 70% of cases. Accordingly, this new approach succeeds in identifying leading indicators and is a viable option for selecting the SSA choices L and r, which minimizes a loss function. 相似文献
169.
Monthly Employment Indicators of the Euro Area and Larger Member States: Real‐Time Analysis of Indirect Estimates 下载免费PDF全文
Filippo Moauro 《Journal of forecasting》2014,33(5):339-349
The paper presents a comparative real‐time analysis of alternative indirect estimates relative to monthly euro area employment. In the experiment quarterly employment is temporally disaggregated using monthly unemployment as related series. The strategies under comparison make use of the contribution of sectoral data of the euro area and its six larger member states. The comparison is carried out among univariate temporal disaggregations of the Chow and Lin type and multivariate structural time series models of small and medium size. Specifications in logarithms are also systematically assessed. All multivariate set‐ups, up to 49 series modelled simultaneously, are estimated via the EM algorithm. Main conclusions are that mean revision errors of disaggregated estimates are overall small, a gain is obtained when the model strategy takes into account the information by both sector and member state and that larger multivariate set‐ups perform very well, with several advantages with respect to simpler models.Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
170.
《Journal of Natural History》2012,46(31-32):1957-1969
Multivariate prey trait analysis is a functional approach to understand predator–prey relationships. In the present study, six prey macroinvertebrate ecological traits were used to identify several key factors in the handling efficiency of seven predatory larval newt species. The results revealed a remarkable similarity in the feeding behaviour among species, suggesting a foraging behaviour convergence among species in the prey-handling efficiency of larval newts. Nevertheless, larvae of some newt species showed clear preferences for particular categories of ecological trait; for example, Lissotriton vulgaris tended to feed on macroinvertebrate taxa with random trajectory, and Calotriton asper fed on macroinvertebrate taxa with high agility. In contrast, Mesotriton alpestris showed a clear ability to feed on prey with movable accessories (cases/tubes) and patterned concealment. This study shows how multivariate approaches can complement traditional diet analyses, and the method has wide applicability across life-stages and species. 相似文献