全文获取类型
收费全文 | 4274篇 |
免费 | 114篇 |
国内免费 | 19篇 |
专业分类
管理学 | 208篇 |
民族学 | 9篇 |
人口学 | 56篇 |
丛书文集 | 71篇 |
理论方法论 | 37篇 |
综合类 | 614篇 |
社会学 | 65篇 |
统计学 | 3347篇 |
出版年
2024年 | 10篇 |
2023年 | 25篇 |
2022年 | 47篇 |
2021年 | 60篇 |
2020年 | 70篇 |
2019年 | 151篇 |
2018年 | 195篇 |
2017年 | 296篇 |
2016年 | 167篇 |
2015年 | 136篇 |
2014年 | 174篇 |
2013年 | 1131篇 |
2012年 | 339篇 |
2011年 | 148篇 |
2010年 | 134篇 |
2009年 | 140篇 |
2008年 | 159篇 |
2007年 | 118篇 |
2006年 | 92篇 |
2005年 | 110篇 |
2004年 | 102篇 |
2003年 | 73篇 |
2002年 | 67篇 |
2001年 | 55篇 |
2000年 | 63篇 |
1999年 | 54篇 |
1998年 | 59篇 |
1997年 | 40篇 |
1996年 | 19篇 |
1995年 | 28篇 |
1994年 | 18篇 |
1993年 | 20篇 |
1992年 | 21篇 |
1991年 | 10篇 |
1990年 | 9篇 |
1989年 | 8篇 |
1988年 | 8篇 |
1987年 | 7篇 |
1986年 | 2篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 5篇 |
1975年 | 1篇 |
排序方式: 共有4407条查询结果,搜索用时 15 毫秒
51.
Logistic regression is estimated by maximizing the log-likelihood objective function formulated under the assumption of maximizing the overall accuracy. That does not apply to the imbalanced data. The resulting models tend to be biased towards the majority class (i.e. non-event), which can bring great loss in practice. One strategy for mitigating such bias is to penalize the misclassification costs of observations differently in the log-likelihood function. Existing solutions require either hard hyperparameter estimating or high computational complexity. We propose a novel penalized log-likelihood function by including penalty weights as decision variables for observations in the minority class (i.e. event) and learning them from data along with model coefficients. In the experiments, the proposed logistic regression model is compared with the existing ones on the statistics of area under receiver operating characteristics (ROC) curve from 10 public datasets and 16 simulated datasets, as well as the training time. A detailed analysis is conducted on an imbalanced credit dataset to examine the estimated probability distributions, additional performance measurements (i.e. type I error and type II error) and model coefficients. The results demonstrate that both the discrimination ability and computation efficiency of logistic regression models are improved using the proposed log-likelihood function as the learning objective. 相似文献
52.
J. M. Thilini Jayasinghe Leif Ellingson Chalani Prematilake 《Journal of applied statistics》2022,49(16):4294
Researchers in statistical shape analysis often analyze outlines of objects. Even though these contours are infinite-dimensional in theory, they must be discretized in practice. When discretizing, it is important to reduce the number of sampling points considerably to reduce computational costs, but to not use too few points so as to result in too much approximation error. Unfortunately, determining the minimum number of points needed to achieve sufficiently approximate the contours is computationally expensive. In this paper, we fit regression models to predict these lower bounds using characteristics of the contours that are computationally cheap as predictor variables. However, least squares regression is inadequate for this task because it treats overestimation and underestimation equally, but underestimation of lower bounds is far more serious. Instead, to fit the models, we use the LINEX loss function, which allows us to penalize underestimation at an exponential rate while penalizing overestimation only linearly. We present a novel approach to select the shape parameter of the loss function and tools for analyzing how well the model fits the data. Through validation methods, we show that the LINEX models work well for reducing the underestimation for the lower bounds. 相似文献
53.
Jimmy Reyes Jaime Arru Osvaldo Venegas Hctor W. Gmez 《Journal of applied statistics》2022,49(16):4206
This work presents an extension of the slash Lindley–Weibull distribution, of which it can be considered a modification. The new family is obtained by using the quotient of two independent random variables: a two-parameter Lindley–Weibull distribution divided by a power of the exponential distribution with parameter equal to 2. We present the pdf and cdf of the new distribution, analyzing their risk functions. Some statistical properties are studied and the moments and coefficients of asymmetry and kurtosis are shown. The parameter estimation problem is carried out by the maximum likelihood method. The method is assessed by a Monte Carlo simulation study. We use nutrition data, which are characterized by high kurtosis, to illustrate the usefulness of the proposed model. 相似文献
54.
刘锦凤 《江苏科技大学学报(自然科学版)》2008,8(2)
财务危机预警分析正在成为企业提高管理水平的重要工具。我国上市饭店企业数量减少,经济效益总体差强人意。企业出现危机能够通过财务信息反映出来,将逻辑回归预警模型引入饭店企业管理中,有助于企业建立相应的预警应对机制,及时采取措施,以减少或消除财务危机带给企业的危害,提高上市饭店企业的竞争力。 相似文献
55.
Chun-Chao Wang Yi-Ting Hwang Chung-Chuan Chou Hui-Ling Lee 《Journal of applied statistics》2023,50(1):155
Many medical applications are interested to know the disease status. The disease status can be related to multiple serial measurements. Nevertheless, owing to various reasons, the binary outcome can be measured incorrectly. The estimators derived from the misspecified outcome can be biased. This paper derives the complete data likelihood function to incorporate both the multiple serial measurements and the misspecified outcome. Owing to the latent variables, EM algorithm is used to derive the maximum-likelihood estimators. Monte Carlo simulations are conducted to compare the impact of misspecification on the estimates. A retrospective data for the recurrence of atrial fibrillation is used to illustrate the usage of the proposed model. 相似文献
56.
朱帮助 《北京理工大学学报(社会科学版)》2014,16(3):22-29
探索碳市场价格驱动力是能源经济领域关注的焦点问题之一。基于欧盟排放交易体系(EU ETS)碳期货价格,综合运用结构性断点检验、协整技术和岭回归方法分析碳市场价格驱动因素和驱动模式。结果表明:2007年巴厘行动计划、2008年全球金融危机和2011年欧债危机,均对碳市场价格走势产生了显著影响,导致了碳市场价格发生结构性变化;碳市场价格与能源价格、工业生产、气温条件等因素间存在协整关系;自2009年10月以来,碳市场价格观测值低于均衡值,未来碳市场价格仍将倾向于贬值。 相似文献
57.
数字经济时代,数字贫困问题对农户收入差距的影响引发新的关注。基于2021年中国农村经济与农村金融数据,采用再中心化响应函数(RIF)回归方法探究数字素养对农户收入差距的影响。研究发现:(1)数字素养显著扩大了农户收入差距,并具备明显的马太效应,高数字素养能够攫取更多数字红利,而低数字素养更容易陷入“数字贫困”状态,无法发挥出数字经济的增收效应。(2)应用数字素养会显著加剧农户收入差距,而通用数字素养对农户收入差距的影响并不显著。这种情况也得以印证,现阶段数字“接入鸿沟”已经得以解决,数字“应用鸿沟”差距逐渐凸显。(3)数字素养能够缩小农户财产性收入差距,但会显著扩大工资性收入差距与非农经营性收入差距。脱贫地区受到数字素养的马太效应更强,农户收入差距明显加剧。研究结论证实了我国农村内部存在明显的数字鸿沟,同时数字贫困问题加剧了农户收入差距。新发展阶段我国数字乡村战略的推进不仅要注重农村低收入群体以及弱势群体数字素养的培育,更要加快构建农村数字经济的包容性发展路径,助力农民农村共同富裕的实现。 相似文献
58.
气候适应性技术采用率低下已成为制约农业可持续发展的重要因素,数字金融可能影响农户的气候适应性行为。基于河南、陕西、山西三省1 384份农户微观调查数据,运用内生转换回归模型构建反事实分析框架,实证分析数字金融使用对农户气候适应性行为的影响效应及其作用机制。研究发现:使用数字金融能显著促进农户气候适应性技术采纳行为,具体表现为在反事实假设下,使用数字金融的农户若未使用其气候适应性技术采纳程度将下降;未使用数字金融的农户如果使用了,其气候适应性技术采纳程度将上升。机制分析表明,数字金融能够提高借贷易得性与信息易得性,进而促进农户采纳气候适应性行为,农户对于金融包容性的认知能够正向增强数字金融对农户气候适应性行为的影响效应。异质性分析表明,数字金融使用对于资本型适应性行为影响的边际效应最大,在反事实假设下也表现为数字金融使用对农户资本型适应性行为提升效果最强;数字金融对农业收入占家庭收入比率较高、接受过培训的农户采纳气候适应性技术促进效应更高。 相似文献
59.
基于1995~2009年中国省际面板数据,利用面板分位数回归模型估计人口因素对我国CO2排放量的影响,结果显示:人口数量和人口城市化率是影响我国CO2排放的主要人口因素,但从影响大小上看,人口数量变化对发达省份CO2排放的影响大于欠发达省份,而人口城市化率则对欠发达省份的CO2排放具有更大的影响;家庭小型化对CO2排放的影响因省而异,对不同省份,要么没有明显的影响,要么可能导致CO2排放量增加;年龄结构目前还不是导致我国CO2排放量变化的主要人口因素;综合比较而言,经济发展水平对CO2排放的影响大于人口各因素,产业结构对CO2排放的影响小于人口数量和人口城市化率,而技术进步与CO2排放的关系则显得模糊。 相似文献
60.
J. C. S. Vasconcelos E. M. M. Ortega J. S. Vasconcelos G. M. Cordeiro A. L. Vivan M. A. M. Biaggioni 《Journal of applied statistics》2022,49(8):2035
A heteroscedastic regression based on the odd log-logistic Marshall–Olkin normal (OLLMON) distribution is defined by extending previous models. Some structural properties of this distribution are presented. The estimation of the parameters is addressed by maximum likelihood. For different parameter settings, sample sizes and some scenarios, various simulations investigate the performance of the heteroscedastic OLLMON regression. We use residual analysis to detect influential observations and to check the model assumptions. The new regression explains the mass loss of different wood species in civil construction in Brazil. 相似文献