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21.
Cathy W. S. Chen F. C. Liu Mike K. P. So 《Australian & New Zealand Journal of Statistics》2008,50(1):29-51
To capture mean and variance asymmetries and time‐varying volatility in financial time series, we generalize the threshold stochastic volatility (THSV) model and incorporate a heavy‐tailed error distribution. Unlike existing stochastic volatility models, this model simultaneously accounts for uncertainty in the unobserved threshold value and in the time‐delay parameter. Self‐exciting and exogenous threshold variables are considered to investigate the impact of a number of market news variables on volatility changes. Adopting a Bayesian approach, we use Markov chain Monte Carlo methods to estimate all unknown parameters and latent variables. A simulation experiment demonstrates good estimation performance for reasonable sample sizes. In a study of two international financial market indices, we consider two variants of the generalized THSV model, with US market news as the threshold variable. Finally, we compare models using Bayesian forecasting in a value‐at‐risk (VaR) study. The results show that our proposed model can generate more accurate VaR forecasts than can standard models. 相似文献
22.
Demographic Shifts in the Czech Republic after 1989: A Second Demographic Transition View 总被引:1,自引:1,他引:0
A dramatic change in fertility,family formation and living arrangements tookplace in the Czech Republic over the 1990s. Theestablishment of democracy, profound socialtransformation and transition to the marketeconomy affected the values and demographicbehaviour of the young Czech generation. Thispaper examines whether these demographic shiftscan be interpreted within the framework of thesecond demographic transition. The theoreticalpart discusses the idea of the transition,outlining three distinctive conceptualisations.Two of them – the view of the transition as aprogression of characteristic interrelateddemographic changes and a broader viewstressing the importance of underlyingideational factors – fit the Czech situationvery well. A comparison with the Netherlandsreveals that the onset of the transition in theCzech Republic may be clearly located in thefirst half of the 1990s, lagging two decadesbehind the Netherlands. 相似文献
23.
V. Nollau 《Statistical Papers》1995,36(1):163-174
In this note we prove some inequalities for variances and other measures of deviation of functions of random variables. Based
on these inequalities we find some corollaries concerning the variances of fractional powers of random variables and of sums
of independent random variables. 相似文献
24.
A table is presented for the construction and selection of tightened-normal-tightened sampling scheme of type TNT-(n1, n2;c). Efficiency of TNT-(n1, n2;c) scheme over conventional single and double sampling plans is discussed. 相似文献
25.
Raymond V. Padilla 《Qualitative sociology》1991,14(3):263-274
Concept modeling is presented as a way to describe and understand social situations. Concepts are developed from field data and supported by sets of exemplars drawn from the data which illustrate the various concepts. The computer is considered an essential tool for conducting this type of qualitative data analysis and displaying the resulting concept models. Two sample concept models are presented along with a discussion of how concept models can be related to teaching and learning, as well as to the nonlinear presentation of research results. Assessment of concept models is then considered. Three types of assessment are suggested: empirical, qualitative and quantitative. 相似文献
26.
The purpose of this paper is to consider the relation between commuting and the settlement structure, with particular attention to rural and nonmetropolitan areas. I examined commuting flows between metropolitan central cities, other metropolitan areas, nonmetropolitan places with more than 10,000 people, those with 2500–10000 people, and other rural areas. Despite the deconcentration of population, industry and trade that was especially marked in the 1970s, commuting in 1980 was predominantly toward larger places in the ruralurban hierarchy, and particularly from rural areas and the other metropolitan category to cities. Overall levels of commuting were high, and most were within either nonmetropolitan or metropolitan areas. Smaller nonmetropolitan places particularly had high proportions of both in- and out-commuters. Differences in commuting flows by gender, socioeconomic status and industry were small, but generally in the directions expected on the basis of prior research. The findings reveal a high degree of work-residence interdependence among settlement units in nonmetropolitan America, with social and economic differences in commuting flows representing an important aspect of community structure. 相似文献
27.
Tomáš Sobotka 《Revue europeenne de demographie》2006,22(1):100-103
28.
V. Scott H. Solberg Aaron H. Carlstrom Kimberly A. S. Howard Janice E. Jones 《The Career development quarterly》2007,55(4):313-327
Using cluster analysis, 789 predominately Latino and African American high school youth were classified into varying academic at‐risk profiles using self‐reported levels of academic confidence, motivation to attend school, perceived family support, connections with teachers and peers, and exposure to violence. Six clusters emerged, 5 of which were identified as “at‐risk.” The clusters were examined in relation to academic stress, health status, grades, and school retention. Exposure to violence was one distinguishing feature of youth identified as most vulnerable, vulnerable, and resilient; however, youth identified as resilient recorded better academic outcomes. 相似文献
29.
Jason P. Fine David V. Glidden Kristine E. Lee 《Journal of the Royal Statistical Society. Series B, Statistical methodology》2003,65(1):317-329
Summary. We propose a simple estimation procedure for a proportional hazards frailty regression model for clustered survival data in which the dependence is generated by a positive stable distribution. Inferences for the frailty parameter can be obtained by using output from Cox regression analyses. The computational burden is substantially less than that of the other approaches to estimation. The large sample behaviour of the estimator is studied and simulations show that the approximations are appropriate for use with realistic sample sizes. The methods are motivated by studies of familial associations in the natural history of diseases. Their practical utility is illustrated with sib pair data from Beaver Dam, Wisconsin. 相似文献
30.
The purpose of this paper is threefold. First, we obtain the asymptotic properties of the modified model selection criteria proposed by Hurvich et al. (1990. Improved estimators of Kullback-Leibler information for autoregressive model selection in small samples. Biometrika 77, 709–719) for autoregressive models. Second, we provide some highlights on the better performance of this modified criteria. Third, we extend the modification introduced by these authors to model selection criteria commonly used in the class of self-exciting threshold autoregressive (SETAR) time series models. We show the improvements of the modified criteria in their finite sample performance. In particular, for small and medium sample size the frequency of selecting the true model improves for the consistent criteria and the root mean square error (RMSE) of prediction improves for the efficient criteria. These results are illustrated via simulation with SETAR models in which we assume that the threshold and the parameters are unknown. 相似文献