全文获取类型
收费全文 | 5944篇 |
免费 | 184篇 |
专业分类
管理学 | 983篇 |
民族学 | 36篇 |
人才学 | 2篇 |
人口学 | 442篇 |
丛书文集 | 47篇 |
理论方法论 | 696篇 |
综合类 | 65篇 |
社会学 | 2914篇 |
统计学 | 943篇 |
出版年
2023年 | 26篇 |
2021年 | 33篇 |
2020年 | 74篇 |
2019年 | 120篇 |
2018年 | 136篇 |
2017年 | 182篇 |
2016年 | 176篇 |
2015年 | 116篇 |
2014年 | 140篇 |
2013年 | 963篇 |
2012年 | 198篇 |
2011年 | 202篇 |
2010年 | 175篇 |
2009年 | 162篇 |
2008年 | 178篇 |
2007年 | 209篇 |
2006年 | 156篇 |
2005年 | 178篇 |
2004年 | 168篇 |
2003年 | 160篇 |
2002年 | 160篇 |
2001年 | 131篇 |
2000年 | 121篇 |
1999年 | 102篇 |
1998年 | 100篇 |
1997年 | 122篇 |
1996年 | 105篇 |
1995年 | 93篇 |
1994年 | 87篇 |
1993年 | 96篇 |
1992年 | 76篇 |
1991年 | 78篇 |
1990年 | 80篇 |
1989年 | 69篇 |
1988年 | 64篇 |
1987年 | 65篇 |
1986年 | 49篇 |
1985年 | 67篇 |
1984年 | 71篇 |
1983年 | 62篇 |
1982年 | 65篇 |
1981年 | 58篇 |
1980年 | 57篇 |
1979年 | 59篇 |
1978年 | 50篇 |
1977年 | 27篇 |
1976年 | 53篇 |
1975年 | 36篇 |
1974年 | 42篇 |
1973年 | 26篇 |
排序方式: 共有6128条查询结果,搜索用时 31 毫秒
971.
972.
The exchangeability and leachability of metals from select green roof growth substrates 总被引:4,自引:0,他引:4
Batch extraction and leaching studies were conducted with potential green roof substrates (e.g., Axis, Arklayte, coal bottom
ash, Haydite, Lassenite, lava rock, and composted pine bark). The results indicated that these materials would not likely
be sources of Cr, Cu, Fe, Ni, or Zn and that Lassenite would be considered a source of Mn if the leachate concentrations were
compared to USEPA drinking water standards for these elements. Lassenite would not be a source of Mn if the data was compared
to a USEPA standard for Mn toxicity to aquatic life. All of the substrates tested leached Cd and/or Pb concentrations that
exceeded the USEPA water quality standards at least once during the 6-month leaching study, so these materials may be potential
sources of Cd and Pb in green roof storm water runoff. The leaching of Cu, Cd, Fe, Mn, Pb, and Zn was differentially influenced
by time and/or the presence of a single Sedum hybridum ‘immergrauch’ plant. The leaching of Cd, Cu, and Pb displayed complex, three-way interactions between main effects (substrate
type and the presence or absence of a plant) and between leaching events. For all substrates except Lassenite, the presence
of a S. hybridum plant decreased the leaching of Pb over time. The leaching of Cd was generally enhanced by plants for most substrates with
time. Collectively the results suggest that changes in the biogeochemical conditions within green roof systems may alter metal
solubility, decreasing the leaching of some elements and increasing the leaching of others. 相似文献
973.
974.
Assessment following serious child abuse is a significant activity for the social work, psychology and psychiatric professions. Notwithstanding the profound significance of the consequences for abused children and their families from recommendations made by such assessments, there is little research which examines the process and outcome of child protection assessments. This paper describes the professional practice principles of an independent assessment team and presents preliminary findings from a retrospective examination of 160 major independent assessments undertaken over a period of 11 years. The review suggests that nearly 60% of the families gained some therapeutic benefit from the assessment process and outlines the areas in which such benefits occurred. It is argued that structuring assessments in a way which maximizes the possibility of parents/carers effecting changes in problem areas is the essence of a constructive partnership relation with families. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
975.
976.
Bryan Ellickson Birgit Grodal Suzanne Scotchmer William R. Zame 《Econometrica : journal of the Econometric Society》1999,67(5):1185-1217
This paper defines a general equilibrium model with exchange and club formation. Agents trade multiple private goods widely in the market, can belong to several clubs, and care about the characteristics of the other members of their clubs. The space of agents is a continuum, but clubs are finite. It is shown that (i) competitive equilibria exist, and (ii) the core coincides with the set of equilibrium states. The central subtlety is in modeling club memberships and expressing the notion that membership choices are consistent across the population. 相似文献
977.
We establish a reflection principle for three lattice walkers and use this principle to reduce the enumeration of configurations of three vicious walkers to the enumeration of configurations of two vicious walkers. More precisely, the reflection principle leads to a bijection between three walks (L1, L2, L3) such that L2 intersects both L1 and L3 and three walks (L1, L2, L3) such that L1 intersects L3. Hence we find a combinatorial interpretation of the formula for the generating function for the number of configurations of three vicious walkers, originally derived by Bousquet-Mélou by using the kernel method, and independently by Gessel by using tableaux and symmetric functions. This answers a question posed by Gessel and Bousquet-Mélou. We also find a reflection principle for four vicious walks that leads to a combinatorial interpretation of a formula derived from Gessel's theorem. 相似文献
978.
In longitudinal biomedical studies, there is often interest in the rate functions, which describe the functional rates of change of biomarker profiles. This paper proposes a semiparametric approach to model these functions as the realizations of stochastic processes defined by stochastic differential equations. These processes are dependent on the covariates of interest and vary around a specified parametric function. An efficient Markov chain Monte Carlo algorithm is developed for inference. The proposed method is compared with several existing methods in terms of goodness-of-fit and more importantly the ability to forecast future functional data in a simulation study. The proposed methodology is applied to prostate-specific antigen profiles for illustration. Supplementary materials for this paper are available online. 相似文献
979.
980.
Andreas Alfons Wolfgang E. Baaske Peter Filzmoser Wolfgang Mader Roland Wieser 《Statistical Methods and Applications》2011,20(1):65-82
A large database containing socioeconomic data from 60 communities in Austria and Germany has been built, stemming from 18,000
citizens’ responses to a survey, together with data from official statistical institutes about these communities. This paper
describes a procedure for extracting a small set of explanatory variables to explain response variables such as the cognition
of quality of life. For better interpretability, the set of explanatory variables needs to be very small and the dependencies
among the selected variables need to be low. Due to possible inhomogeneities within the data set, it is further required that
the solution is robust to outliers and deviating points. In order to achieve these goals, a robust model selection method,
combined with a strategy to reduce the number of selected predictor variables to a necessary minimum, is developed. In addition,
this context-sensitive method is applied to obtain responsible factors describing quality of life in communities. 相似文献