全文获取类型
收费全文 | 20645篇 |
免费 | 405篇 |
专业分类
管理学 | 2349篇 |
民族学 | 122篇 |
人才学 | 8篇 |
人口学 | 1977篇 |
丛书文集 | 121篇 |
教育普及 | 2篇 |
理论方法论 | 1993篇 |
现状及发展 | 1篇 |
综合类 | 243篇 |
社会学 | 10470篇 |
统计学 | 3764篇 |
出版年
2023年 | 114篇 |
2022年 | 92篇 |
2021年 | 108篇 |
2020年 | 337篇 |
2019年 | 539篇 |
2018年 | 541篇 |
2017年 | 763篇 |
2016年 | 545篇 |
2015年 | 423篇 |
2014年 | 515篇 |
2013年 | 3487篇 |
2012年 | 738篇 |
2011年 | 670篇 |
2010年 | 520篇 |
2009年 | 496篇 |
2008年 | 565篇 |
2007年 | 587篇 |
2006年 | 539篇 |
2005年 | 472篇 |
2004年 | 485篇 |
2003年 | 434篇 |
2002年 | 446篇 |
2001年 | 501篇 |
2000年 | 413篇 |
1999年 | 405篇 |
1998年 | 327篇 |
1997年 | 300篇 |
1996年 | 298篇 |
1995年 | 291篇 |
1994年 | 270篇 |
1993年 | 272篇 |
1992年 | 303篇 |
1991年 | 299篇 |
1990年 | 271篇 |
1989年 | 265篇 |
1988年 | 254篇 |
1987年 | 243篇 |
1986年 | 229篇 |
1985年 | 257篇 |
1984年 | 246篇 |
1983年 | 245篇 |
1982年 | 184篇 |
1981年 | 165篇 |
1980年 | 179篇 |
1979年 | 183篇 |
1978年 | 149篇 |
1977年 | 154篇 |
1976年 | 127篇 |
1975年 | 131篇 |
1974年 | 103篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
13.
A NOTE ON EVANESCENT PROCESSES 总被引:1,自引:0,他引:1
This note examines the connection between μ-invariant measures for the transition function of a continuous-time Markov chain and those of its q-matrix, Q. The major result establishes a necessary and aufficient condition for a convergent μ-invariant measure for Q to be μ-inhant for the minimal transition function, P, under the assumption that P is honest. This corrects Theorem 6 of Vere-Jones (1969) and the first part of Corollary 1 of Pollett (1986), both of which assert that the above conclusion holds in the absence of this condition. The error was pointed out by E.A. van Doom (1991) and the counterexample which be presented provides the basis for the present arguments. In determining where the error occurred in the original proof, we are able to identify a simple sufficient condition for μ-invariance. 相似文献
14.
15.
Albert A. Bartlett 《Population and environment》1993,14(4):359-387
This is a tutorial on the relations between population data and the rates of growth that are calculated from the data. For the calculation of rates of growth, discrete and continuous compounding will be compared so that the reader can see the reasons for using the mathematics of continuous compounding, which is the mathematics of exponential growth. Some properties of exponential growth are developed. Semi-logarithmic graphs will be discussed as a device for representing the size of growing populations and for analyzing the nature of the growth. Illustrative examples will be worked out in order to emphasize applications and utility. 相似文献
16.
Multiparameter evidence synthesis in epidemiology and medical decision-making: current approaches 总被引:1,自引:0,他引:1
A. E. Ades A. J. Sutton 《Journal of the Royal Statistical Society. Series A, (Statistics in Society)》2006,169(1):5-35
Summary. Alongside the development of meta-analysis as a tool for summarizing research literature, there is renewed interest in broader forms of quantitative synthesis that are aimed at combining evidence from different study designs or evidence on multiple parameters. These have been proposed under various headings: the confidence profile method, cross-design synthesis, hierarchical models and generalized evidence synthesis. Models that are used in health technology assessment are also referred to as representing a synthesis of evidence in a mathematical structure. Here we review alternative approaches to statistical evidence synthesis, and their implications for epidemiology and medical decision-making. The methods include hierarchical models, models informed by evidence on different functions of several parameters and models incorporating both of these features. The need to check for consistency of evidence when using these powerful methods is emphasized. We develop a rationale for evidence synthesis that is based on Bayesian decision modelling and expected value of information theory, which stresses not only the need for a lack of bias in estimates of treatment effects but also a lack of bias in assessments of uncertainty. The increasing reliance of governmental bodies like the UK National Institute for Clinical Excellence on complex evidence synthesis in decision modelling is discussed. 相似文献
17.
18.
19.
Diane Hope Weixing Zhu Corinna Gries Jacob Oleson Jason Kaye Nancy B. Grimm Lawrence A. Baker 《Urban Ecosystems》2005,8(3-4):251-273
We explored variations in inorganic soil nitrogen (N) concentrations across metropolitan Phoenix, Arizona, and the surrounding
desert using a probability-based synoptic survey. Data were examined using spatial statistics on the entire region, as well
as for the desert and urban sites separately. Concentrations of both NO3-N and NH4-N were markedly higher and more heterogeneous amongst urban compared to desert soils. Regional variation in soil NO3-N concentration was best explained by latitude, land use history, population density, along with percent cover of impervious
surfaces and lawn, whereas soil NH4-N concentrations were related to only latitude and population density. Within the urban area, patterns in both soil NO3-N and NH4-N were best predicted by elevation, population density and type of irrigation in the surrounding neighborhood. Spatial autocorrelation
of soil NO3-N concentrations explained 49% of variation among desert sites but was absent between urban sites. We suggest that inorganic
soil N concentrations are controlled by a number of ‘local’ or ‘neighborhood’ human-related drivers in the city, rather than
factors related to an urban-rural gradient. 相似文献
20.
A sample size justification should be given for all clinical investigations. However, sometimes the objective of a trial is to estimate an effect with a view to planning a later definitive study. This paper describes the calculations for designing studies where one wishes to adopt an estimation approach through using confidence intervals around the overall response. Calculations are given for data anticipated to take a Normal form. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献