全文获取类型
收费全文 | 3943篇 |
免费 | 119篇 |
国内免费 | 18篇 |
专业分类
管理学 | 390篇 |
民族学 | 7篇 |
人口学 | 73篇 |
丛书文集 | 59篇 |
理论方法论 | 100篇 |
综合类 | 394篇 |
社会学 | 258篇 |
统计学 | 2799篇 |
出版年
2024年 | 1篇 |
2023年 | 29篇 |
2022年 | 32篇 |
2021年 | 39篇 |
2020年 | 64篇 |
2019年 | 112篇 |
2018年 | 163篇 |
2017年 | 239篇 |
2016年 | 120篇 |
2015年 | 123篇 |
2014年 | 131篇 |
2013年 | 920篇 |
2012年 | 291篇 |
2011年 | 147篇 |
2010年 | 137篇 |
2009年 | 166篇 |
2008年 | 161篇 |
2007年 | 153篇 |
2006年 | 124篇 |
2005年 | 136篇 |
2004年 | 115篇 |
2003年 | 97篇 |
2002年 | 76篇 |
2001年 | 74篇 |
2000年 | 70篇 |
1999年 | 57篇 |
1998年 | 52篇 |
1997年 | 42篇 |
1996年 | 21篇 |
1995年 | 18篇 |
1994年 | 27篇 |
1993年 | 17篇 |
1992年 | 20篇 |
1991年 | 14篇 |
1990年 | 11篇 |
1989年 | 8篇 |
1988年 | 12篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 9篇 |
1984年 | 7篇 |
1983年 | 11篇 |
1982年 | 9篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 1篇 |
排序方式: 共有4080条查询结果,搜索用时 31 毫秒
51.
Lesa L. Aylward Robert C. Brunet Thomas B. Starr Gaétan Carrier Elizabeth Delzell Hong Cheng Colleen Beall 《Risk analysis》2005,25(4):945-956
Recent studies demonstrating a concentration dependence of elimination of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) suggest that previous estimates of exposure for occupationally exposed cohorts may have underestimated actual exposure, resulting in a potential overestimate of the carcinogenic potency of TCDD in humans based on the mortality data for these cohorts. Using a database on U.S. chemical manufacturing workers potentially exposed to TCDD compiled by the National Institute for Occupational Safety and Health (NIOSH), we evaluated the impact of using a concentration- and age-dependent elimination model (CADM) (Aylward et al., 2005) on estimates of serum lipid area under the curve (AUC) for the NIOSH cohort. These data were used previously by Steenland et al. (2001) in combination with a first-order elimination model with an 8.7-year half-life to estimate cumulative serum lipid concentration (equivalent to AUC) for these workers for use in cancer dose-response assessment. Serum lipid TCDD measurements taken in 1988 for a subset of the cohort were combined with the NIOSH job exposure matrix and work histories to estimate dose rates per unit of exposure score. We evaluated the effect of choices in regression model (regression on untransformed vs. ln-transformed data and inclusion of a nonzero regression intercept) as well as the impact of choices of elimination models and parameters on estimated AUCs for the cohort. Central estimates for dose rate parameters derived from the serum-sampled subcohort were applied with the elimination models to time-specific exposure scores for the entire cohort to generate AUC estimates for all cohort members. Use of the CADM resulted in improved model fits to the serum sampling data compared to the first-order models. Dose rates varied by a factor of 50 among different combinations of elimination model, parameter sets, and regression models. Use of a CADM results in increases of up to five-fold in AUC estimates for the more highly exposed members of the cohort compared to estimates obtained using the first-order model with 8.7-year half-life. This degree of variation in the AUC estimates for this cohort would affect substantially the cancer potency estimates derived from the mortality data from this cohort. Such variability and uncertainty in the reconstructed serum lipid AUC estimates for this cohort, depending on elimination model, parameter set, and regression model, have not been described previously and are critical components in evaluating the dose-response data from the occupationally exposed populations. 相似文献
52.
Current status data arise when the death of every subject in a study cannot be determined precisely, but is known only to have occurred before or after a random monitoring time. The authors discuss the analysis of such data under semiparametric linear transformation models for which they propose a general inference procedure based on estimating functions. They determine the properties of the estimates they propose for the regression parameters of the model and illustrate their technique using tumorigenicity data. 相似文献
53.
本文分析了传统FAGM(1,1)模型建模过程中存在的误差,提出了一种基于Simpson公式改进的FAGM(1,1)模型。首先,基于分数阶累加生成算子和分数阶累减生成算子建立分数阶FAGM(1,1)模型。其次,利用Simpson积分公式对FAGM(1,1)模型的背景值进行改进,建立SFAGM(1,1)模型。进一步,应用遗传算法确定SFAGM(1,1)模型的最优阶数以提高模型的预测精度。最后,以中国人均GDP为例,对比分析GM(1,1)模型、Simpson改进的GM(1,1)模型(SGM(1,1))、FAGM(1,1)模型、SFAGM(1,1)模型的模拟结果,并对"十三五"时期的人均GDP进行预测,其结果表明SFAGM(1,1)模型比GM(1,1)、SGM(1,1)、FAGM(1,1)在人均GDP的预测方面有更高的精度,"十三五"期间人均GDP年平均增长率为10.64%,到2020年达到83146.97元,是2010年人均GDP的2.69倍,以2010年的人均GDP为基准,到2020年将能够实现翻一番的目标。 相似文献
54.
55.
Inge S. Helland 《Scandinavian Journal of Statistics》1998,25(1):3-15
Several authors have contributed to what can now be considered a rather complete theory for analysis of variance in cases with orthogonal factors. By using this theory on an assumed basic reference population, the orthogonality concept gives a natural definition of independence between factors in the population. By looking upon the treated units in designed experiments as a formal sample from a future population about which we want to make inference, a natural parametrization of expectations and variances connected to such experiments arises. This approach seems to throw light upon several controversial questions in the theory of mixed models. Also, it gives a framework for discussing the choice of conditioning in models 相似文献
56.
Generalized Leverage and its Applications 总被引:2,自引:0,他引:2
The generalized leverage of an estimator is defined in regression models as a measure of the importance of individual observations. We derive a simple but powerful result, developing an explicit expression for leverage in a general M -estimation problem, of which the maximum likelihood problems are special cases. A variety of applications are considered, most notably to the exponential family non-linear models. The relationship between leverage and local influence is also discussed. Numerical examples are given to illustrate our results 相似文献
57.
A Multivariate Model for Repeated Failure Time Measurements 总被引:1,自引:1,他引:0
Martin Crowder 《Scandinavian Journal of Statistics》1998,25(1):53-67
A parametric multivariate failure time distribution is derived from a frailty-type model with a particular frailty distribution. It covers as special cases certain distributions which have been used for multivariate survival data in recent years. Some properties of the distribution are derived: its marginal and conditional distributions lie within the parametric family, and association between the component variates can be positive or, to a limited extent, negative. The simple closed form of the survivor function is useful for right-censored data, as occur commonly in survival analysis, and for calculating uniform residuals. Also featured is the distribution of ratios of paired failure times. The model is applied to data from the literature 相似文献
58.
J. E. Kelsall & P. J. Diggle 《Journal of the Royal Statistical Society. Series C, Applied statistics》1998,47(4):559-573
A common problem in environmental epidemiology is the estimation and mapping of spatial variation in disease risk. In this paper we analyse data from the Walsall District Health Authority, UK, concerning the spatial distributions of cancer cases compared with controls sampled from the population register. We formulate the risk estimation problem as a nonparametric binary regression problem and consider two different methods of estimation. The first uses a standard kernel method with a cross-validation criterion for choosing the associated bandwidth parameter. The second uses the framework of the generalized additive model (GAM) which has the advantage that it can allow for additional explanatory variables, but is computationally more demanding. For the Walsall data, we obtain similar results using either the kernel method with controls stratified by age and sex to match the age–sex distribution of the cases or the GAM method with random controls but incorporating age and sex as additional explanatory variables. For cancers of the lung or stomach, the analysis shows highly statistically significant spatial variation in risk. For the less common cancers of the pancreas, the spatial variation in risk is not statistically significant. 相似文献
59.
Maria Brouwer 《Journal of Management and Governance》2005,9(3-4):237-255
Organizational innovation is essential to economic development. But, the way successful societies have organized new ventures
has been remarkably similar in both past and present. The commenda organizations of medieval Italy shared many characteristics
with modern startups that are financed by venture capital. Profit share contracts; limited liability and periodic reevaluations
are cases in point. Agency contracts in both types of ventures are designed to absorb the high uncertainty inherent to these
enterprises through risk sharing. Uncertainty prohibits a unique ex ante ranking order of investment projects and prompts
investors to look for hidden human capital. Equity finance is better equipped to even out unexpected losses and gains that
are inherent to uncertainty than debt finance. 相似文献
60.