全文获取类型
收费全文 | 649篇 |
免费 | 7篇 |
专业分类
管理学 | 16篇 |
民族学 | 1篇 |
人口学 | 5篇 |
丛书文集 | 10篇 |
理论方法论 | 10篇 |
综合类 | 103篇 |
社会学 | 28篇 |
统计学 | 483篇 |
出版年
2023年 | 2篇 |
2021年 | 3篇 |
2020年 | 6篇 |
2019年 | 20篇 |
2018年 | 20篇 |
2017年 | 28篇 |
2016年 | 7篇 |
2015年 | 14篇 |
2014年 | 41篇 |
2013年 | 196篇 |
2012年 | 51篇 |
2011年 | 22篇 |
2010年 | 26篇 |
2009年 | 16篇 |
2008年 | 33篇 |
2007年 | 30篇 |
2006年 | 19篇 |
2005年 | 13篇 |
2004年 | 11篇 |
2003年 | 12篇 |
2002年 | 8篇 |
2001年 | 9篇 |
2000年 | 8篇 |
1999年 | 9篇 |
1998年 | 6篇 |
1997年 | 5篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 5篇 |
1977年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有656条查询结果,搜索用时 15 毫秒
1.
Fire and restoration of the largest urban forest of the world in Rio de Janeiro City,Brazil 总被引:1,自引:1,他引:0
National Park of Tijuca in Rio de Janeiro (Brazil) is about 3,300 ha and considered the largest urban forest in the world. Its floristic composition is typical of Atlantic Rain Forest. The reserve is being altered because of fire occurrences and urban expansion. This study identified locations and causes of forest fires, and makes management recommendations to restore damaged areas. From 1991 to 2000, forest firefighters recorded an average of 75-fire occurrences/year. Identified causes included hot air balloons (24%), intentional (24%), rubbish burning (21%) and religious practices (17%). Primary fuels included invasive grasses and ferns. Although hot air balloons destroyed larger areas of forest in each occurrence, a greater number of fires started in the invasive vegetation along roads that bisect the forest. In response to recurrent forests, invasive vegetation has spread gradually into the forest increasing forest degradation. To decrease fire damage, sites with high fire frequencies and density of invasive vegetation were planted with less flammable species. Results indicate that fire frequency decreased and density of invasive vegetation declined. This approach appears to prevent fire incidence, reduce the need for fire fighting, and preserve existing biodiversity. 相似文献
2.
Michael P. Fay Ji-Hyun Lee 《Journal of the Royal Statistical Society. Series A, (Statistics in Society)》2006,169(1):81-96
Summary. We detail a general method for measuring agreement between two statistics. An application is two ratios of directly standardized rates which differ only by the choice of the standard. If the statistics have a high value for the coefficient of agreement then the expected squared difference between the statistics is small relative to the variance of the average of the two statistics, and inferences vary little by changing statistics. The estimation of a coefficient of agreement between two statistics is not straightforward because there is only one pair of observed values, each statistic calculated from the data. We introduce estimators of the coefficient of agreement for two statistics and discuss their use, especially as applied to functions of standardized rates. 相似文献
3.
John D. Emerson David C. Hoaglin Frederick Mosteller 《Statistical Methods and Applications》1993,2(3):269-290
Summary Meta-analyses of sets of clinical trials often combine risk differences from several 2×2 tables according to a random-effects
model. The DerSimonian-Laird random-effects procedure, widely used for estimating the populaton mean risk difference, weights
the risk difference from each primary study inversely proportional to an estimate of its variance (the sum of the between-study
variance and the conditional within-study variance). Because those weights are not independent of the risk differences, however,
the procedure sometimes exhibits bias and unnatural behavior. The present paper proposes a modified weighting scheme that
uses the unconditional within-study variance to avoid this source of bias. The modified procedure has variance closer to that
available from weighting by ideal weights when such weights are known. We studied the modified procedure in extensive simulation
experiments using situations whose parameters resemble those of actual studies in medical research. For comparison we also
included two unbiased procedures, the unweighted mean and a sample-size-weighted mean; their relative variability depends
on the extent of heterogeneity among the primary studies. An example illustrates the application of the procedures to actual
data and the differences among the results.
This research was supported by Grant HS 05936 from the Agency for Health Care Policy and Research to Harvard University. 相似文献
4.
Generalized additive models for location, scale and shape 总被引:10,自引:0,他引:10
R. A. Rigby D. M. Stasinopoulos 《Journal of the Royal Statistical Society. Series C, Applied statistics》2005,54(3):507-554
Summary. A general class of statistical models for a univariate response variable is presented which we call the generalized additive model for location, scale and shape (GAMLSS). The model assumes independent observations of the response variable y given the parameters, the explanatory variables and the values of the random effects. The distribution for the response variable in the GAMLSS can be selected from a very general family of distributions including highly skew or kurtotic continuous and discrete distributions. The systematic part of the model is expanded to allow modelling not only of the mean (or location) but also of the other parameters of the distribution of y , as parametric and/or additive nonparametric (smooth) functions of explanatory variables and/or random-effects terms. Maximum (penalized) likelihood estimation is used to fit the (non)parametric models. A Newton–Raphson or Fisher scoring algorithm is used to maximize the (penalized) likelihood. The additive terms in the model are fitted by using a backfitting algorithm. Censored data are easily incorporated into the framework. Five data sets from different fields of application are analysed to emphasize the generality of the GAMLSS class of models. 相似文献
5.
Given d>2 and a set of n grid points Q in ℜ
d
, we design a randomized algorithm that finds a w-wide separator, which is determined by a hyper-plane, in
sublinear time such that Q has at most
points on either side of the hyper-plane, and at most
points within
distance to the hyper-plane, where c
d
is a constant for fixed d. In particular, c
3=1.209. To our best knowledge, this is the first sublinear time algorithm for finding geometric separators. Our 3D separator
is applied to derive an algorithm for the protein side-chain packing problem, which improves and simplifies the previous algorithm
of Xu (Research in computational molecular biology, 9th annual international conference, pp. 408–422, 2005).
This research is supported by Louisiana Board of Regents fund under contract number LEQSF(2004-07)-RD-A-35.
The part of this research was done while Bin Fu was associated with the Department of Computer Science, University of New
Orleans, LA 70148, USA and the Research Institute for Children, 200 Henry Clay Avenue, New Orleans, LA 70118, USA. 相似文献
6.
It is shown that the uncertainty connected with a `random in a broad sense' (not necessarily stochastic) event always has some `statistical regularity' (SR) in the form of a family of finite-additive probability distributions. The specific principle of guaranteed result in decision making is introduced. It is shown that observing this principle of guaranteed result leads to determine the one optimality criterion corresponding to a decision system with a given `statistical regularity'. 相似文献
7.
8.
Yen-Luan Chen 《统计学通讯:理论与方法》2019,48(3):676-688
From the economical viewpoint in reliability theory, this paper addresses a scheduling replacement problem for a single operating system which works at random times for multiple jobs. The system is subject to stochastic failure which results the imperfect maintenance activity based on some random failure mechanism: minimal repair due to type-I (repairable) failure, or corrective replacement due to type-II (non-repairable) failure. Three scheduling models for the system with multiple jobs are considered: a single work, N tandem works, and N parallel works. To control the deterioration process, the preventive replacement is planned to undergo at a scheduling time T or the job's completion time of for each model. The objective is to determine the optimal scheduling parameters (T* or N*) that minimizes the mean cost rate function in a finite time horizon for each model. A numerical example is provided to illustrate the proposed analytical model. Because the framework and analysis are general, the proposed models extend several existing results. 相似文献
9.
Let X = {X1, X2, …} be a sequence of independent but not necessarily identically distributed random variables, and let η be a counting random variable independent of X. Consider randomly stopped sum Sη = ∑ηk = 1Xk and random maximum S(η) ? max?{S0, …, Sη}. Assuming that each Xk belongs to the class of consistently varying distributions, on the basis of the well-known precise large deviation principles, we prove that the distributions of Sη and S(η) belong to the same class under some mild conditions. Our approach is new and the obtained results are further studies of Kizinevi?, Sprindys, and ?iaulys (2016) and Andrulyt?, Manstavi?ius, and ?iaulys (2017). 相似文献
10.
唐静 《山西农业大学学报(社会科学版)》2010,9(5):516-518
我国林业工作在取得巨大成就的同时,也存在着一些突出问题。如人工纯林问题、天然林保护不力、绿化中大面积铺设草皮等现象。其根本原因在于传统的人类中心主义价值观指导下人们只关注森林的工具价值,而忽视森林的内在价值尤其是森林生态系统的价值。罗尔斯顿"生态整体论"为人类认识森林问题和森林价值提供了新视角,对林业实践具有指导意义。为实现林业可持续发展,必须扭转人类中心主义观念,实现由以木材生产为主向以生态建设为主的转变,注重维护森林系统整体性、保护生物多样性。 相似文献