全文获取类型
收费全文 | 856篇 |
免费 | 23篇 |
专业分类
管理学 | 61篇 |
民族学 | 5篇 |
人口学 | 71篇 |
丛书文集 | 7篇 |
理论方法论 | 104篇 |
综合类 | 4篇 |
社会学 | 568篇 |
统计学 | 59篇 |
出版年
2023年 | 6篇 |
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 17篇 |
2019年 | 23篇 |
2018年 | 18篇 |
2017年 | 45篇 |
2016年 | 18篇 |
2015年 | 20篇 |
2014年 | 19篇 |
2013年 | 174篇 |
2012年 | 29篇 |
2011年 | 26篇 |
2010年 | 24篇 |
2009年 | 23篇 |
2008年 | 31篇 |
2007年 | 31篇 |
2006年 | 26篇 |
2005年 | 22篇 |
2004年 | 17篇 |
2003年 | 19篇 |
2002年 | 23篇 |
2001年 | 24篇 |
2000年 | 22篇 |
1999年 | 18篇 |
1998年 | 22篇 |
1997年 | 13篇 |
1996年 | 18篇 |
1995年 | 14篇 |
1994年 | 13篇 |
1993年 | 10篇 |
1992年 | 14篇 |
1991年 | 2篇 |
1990年 | 8篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1986年 | 7篇 |
1985年 | 9篇 |
1984年 | 11篇 |
1983年 | 3篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1973年 | 2篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1967年 | 2篇 |
排序方式: 共有879条查询结果,搜索用时 15 毫秒
121.
Leaf litter, by modifying microenvironmental conditions, can alter plant population distributions and is considered to be a major force in structuring many plant communities. Comparative studies of urban, suburban, and rural forests in the New York City (NYC) metropolitan area have identified numerous biotic and abiotic differences among these forests, including several involved in leaf litter decomposition. These differences in decomposition among the forests could result in differences in litter quantity on the forest floor and hence microenvironmental conditions and safe sites for germination of different plant species. We conducted a survey of forest floor leaf litter quantity in forests located along an urban-to-rural land-use gradient originating in urban NYC and extending to rural Connecticut. Mean litter depth, mass, and density increased significantly with increased distance of the forest from NYC.We also surveyed woody seedlings and compared the litter depth in which they naturally occurred to the mean litter depth of the surrounding forest. Seedlings of small-seeded species were much more likely to be located in litter shallower than mean forest litter depth than were seedlings of large-seeded species. Taken together, these results suggest that environmental changes associated with urbanization may have profound effects on long-term patterns of forest regeneration. 相似文献
122.
Topics in Microbial Risk Assessment: Dynamic Flow Tree Process 总被引:5,自引:0,他引:5
Microbial risk assessment is emerging as a new discipline in risk assessment. A systematic approach to microbial risk assessment is presented that employs data analysis for developing parsimonious models and accounts formally for the variability and uncertainty of model inputs using analysis of variance and Monte Carlo simulation. The purpose of the paper is to raise and examine issues in conducting microbial risk assessments. The enteric pathogen Escherichia coli O157:H7 was selected as an example for this study due to its significance to public health. The framework for our work is consistent with the risk assessment components described by the National Research Council in 1983 (hazard identification; exposure assessment; dose-response assessment; and risk characterization). Exposure assessment focuses on hamburgers, cooked a range of temperatures from rare to well done, the latter typical for fast food restaurants. Features of the model include predictive microbiology components that account for random stochastic growth and death of organisms in hamburger. For dose-response modeling, Shigella data from human feeding studies were used as a surrogate for E. coli O157:H7. Risks were calculated using a threshold model and an alternative nonthreshold model. The 95% probability intervals for risk of illness for product cooked to a given internal temperature spanned five orders of magnitude for these models. The existence of even a small threshold has a dramatic impact on the estimated risk. 相似文献
123.
Margaret K. Nelson 《Rural sociology》1999,64(1):18-43
Abstract This paper combines three issues that have previously been considered separately: economic restructuring, gender, and participation in the informal economy. Drawing on two complementary data sets of interviews with the residents of a rural county, the paper first suggests that the participation in the informal economy is extensive. The second major finding is that households whose members have held on to “good” work in the formal economy participate in the informal economy in a different way than do households whose members are less fortunate. Third, the paper demonstrates that participation in the informal economy is highly differentiated by gender. Finally the intersections among location in the formal economy, gender, and informal economic activities are discussed. 相似文献
124.
125.
126.
Gaohong Dong David C. Hoaglin Bo Huang Ying Cui Duolao Wang Yu Cheng Margaret Gamalo-Siebers 《Pharmaceutical statistics》2023,22(4):748-756
The win odds and the net benefit are related directly to each other and indirectly, through ties, to the win ratio. These three win statistics test the same null hypothesis of equal win probabilities between two groups. They provide similar p-values and powers, because the Z-values of their statistical tests are approximately equal. Thus, they can complement one another to show the strength of a treatment effect. In this article, we show that the estimated variances of the win statistics are also directly related regardless of ties or indirectly related through ties. Since its introduction in 2018, the stratified win ratio has been applied in designs and analyses of clinical trials, including Phase III and Phase IV studies. This article generalizes the stratified method to the win odds and the net benefit. As a result, the relations of the three win statistics and the approximate equivalence of their statistical tests also hold for the stratified win statistics. 相似文献
127.
This evaluation assessed whether participation in Parents Anonymous mutual support groups was associated with child maltreatment prevention. Parents new to groups across the United States were interviewed at baseline, one month, and six months. Using standardized scales, all parents showed improvements in some child maltreatment outcomes, risk factors, and protective factors. Parents starting out with particularly serious needs showed statistically significant improvement on every scale. Results indicated that Parents Anonymous participation contributes to child maltreatment reduction. 相似文献
128.
Hana Jeon Margaret C. Moulson Nathan Fox Charles Zeanah Charles A. Nelson III 《Infancy》2010,15(2):209-221
The current study examined the effects of institutionalization on the discrimination of facial expressions of emotion in three groups of 42‐month‐old children. One group consisted of children abandoned at birth who were randomly assigned to Care‐as‐Usual (institutional care) following a baseline assessment. Another group consisted of children abandoned at birth who were randomly assigned to high‐quality foster care following a baseline assessment. A third group consisted of never‐institutionalized children who were reared by their biological parents. All children were familiarized to happy, sad, fearful, and neutral facial expressions and tested on their ability to discriminate familiar versus novel facial expressions. Contrary to our prediction, all three groups of children were equally capable of discriminating among the different expressions. Furthermore, in contrast to findings at 13–30 months of age, these same children showed familiarity rather than novelty preferences toward different expressions. There were also asymmetries in children’s discrimination of facial expressions depending on which facial expression served as the familiar versus novel stimulus. Collectively, early institutionalization appears not to impact the development of the ability to discriminate facial expressions of emotion, at least when preferential looking serves as the dependent measure. These findings are discussed in the context of the myriad domains that are affected by early institutionalization. 相似文献
129.
The autonomy perspective of housework time predicts that wives' housework time falls steadily as their earnings rise, because wives use additional financial resources to outsource or forego time in housework. We argue, however, that wives' ability to reduce their housework varies by household task. That is, we expect that increases in wives' earnings will allow them to forego or outsource some tasks, but not others. As a result, we hypothesize more rapid declines in wives' housework time for low-earning wives as their earnings increase than for high-earning wives who have already stopped performing household tasks that are the easiest and cheapest to outsource or forego. Using fixed-effects models and data from the Panel Study of Income Dynamics, we find considerable support for our hypothesis. We further conclude that past evidence that wives who out-earn their husbands spend additional time in housework to compensate for their gender-deviant success in the labor market is due to the failure to account for the non-linear relationship between wives' absolute earnings and their housework time. 相似文献
130.
Stephen J. Ruberg Frank E. Harrell Jr. Margaret Gamalo-Siebers Lisa LaVange J. Jack Lee Karen Price 《The American statistician》2019,73(1):319-327
ABSTRACTThe cost and time of pharmaceutical drug development continue to grow at rates that many say are unsustainable. These trends have enormous impact on what treatments get to patients, when they get them and how they are used. The statistical framework for supporting decisions in regulated clinical development of new medicines has followed a traditional path of frequentist methodology. Trials using hypothesis tests of “no treatment effect” are done routinely, and the p-value < 0.05 is often the determinant of what constitutes a “successful” trial. Many drugs fail in clinical development, adding to the cost of new medicines, and some evidence points blame at the deficiencies of the frequentist paradigm. An unknown number effective medicines may have been abandoned because trials were declared “unsuccessful” due to a p-value exceeding 0.05. Recently, the Bayesian paradigm has shown utility in the clinical drug development process for its probability-based inference. We argue for a Bayesian approach that employs data from other trials as a “prior” for Phase 3 trials so that synthesized evidence across trials can be utilized to compute probability statements that are valuable for understanding the magnitude of treatment effect. Such a Bayesian paradigm provides a promising framework for improving statistical inference and regulatory decision making. 相似文献