全文获取类型
收费全文 | 4700篇 |
免费 | 156篇 |
专业分类
4856篇 |
出版年
2020年 | 55篇 |
2019年 | 109篇 |
2018年 | 117篇 |
2017年 | 124篇 |
2016年 | 122篇 |
2015年 | 100篇 |
2014年 | 98篇 |
2013年 | 1373篇 |
2012年 | 143篇 |
2011年 | 128篇 |
2010年 | 159篇 |
2009年 | 154篇 |
2008年 | 102篇 |
2007年 | 126篇 |
2006年 | 109篇 |
2005年 | 65篇 |
2004年 | 59篇 |
2003年 | 63篇 |
2002年 | 67篇 |
2001年 | 71篇 |
2000年 | 57篇 |
1999年 | 63篇 |
1998年 | 64篇 |
1997年 | 55篇 |
1996年 | 64篇 |
1995年 | 48篇 |
1994年 | 50篇 |
1993年 | 46篇 |
1992年 | 45篇 |
1991年 | 37篇 |
1990年 | 28篇 |
1989年 | 44篇 |
1988年 | 37篇 |
1987年 | 52篇 |
1986年 | 40篇 |
1985年 | 43篇 |
1984年 | 51篇 |
1983年 | 45篇 |
1982年 | 32篇 |
1981年 | 42篇 |
1980年 | 53篇 |
1979年 | 47篇 |
1978年 | 32篇 |
1977年 | 52篇 |
1976年 | 35篇 |
1975年 | 37篇 |
1974年 | 25篇 |
1972年 | 25篇 |
1970年 | 23篇 |
1969年 | 22篇 |
排序方式: 共有4856条查询结果,搜索用时 0 毫秒
51.
52.
E. J. Fagan 《政策研究杂志》2023,51(2):243-263
This paper develops a theory of the relationship between policy disasters and political institutions. Policy disasters, defined as avoidable, unintended extreme negative policy outcomes, are important political, and historical events above that receive relatively little attention from political scientists and scholars of public policy. Using the predictions of punctuated equilibrium theory, I argue that systems with higher error accumulation will experience more policy disasters. Systems with more veto players and weaker information flows will experience more policy disasters, but information flows will have a stronger impact than veto players. I test this theory using data on financial crises and natural and technological disasters across 70 countries over 60 years. I find strong evidence that systems with weaker information flows and more veto players tend to have greater policy disaster risk. 相似文献
53.
54.
55.
The conventional model of the relationship between welfare incentives and poverty rates holds that welfare payments produce an income-enhancement effect that removes families from poverty until some threshold. Beyond this point increased payments engender a work-disincentive effect resulting in increased rates of poverty. We challenge the model's assumption that poverty levels are a simple and spatially invariant response to welfare incentives, contending instead that local employment conditions may substantially alter the relation. Our reformulation of the conventional modeling approach is based on the expansion method. Specifically, we extend the model to include the effects of local labor-market conditions on the response of poverty levels to welfare incentives. In contesting the invariance assumption, the expansion method allows us to determine where and in what contexts welfare is “work discouraging.” The empirical analysis, which is undertaken at the county level, indicates that welfare payments vary in their influence on poverty rates across different employment contexts. A national map portraying this parameter instability demonstrates that female-family poverty rates are most responsive to welfare assistance in the rural South and least responsive in the metropolitan Northeast. Finally, we examine two sharply contrasting locales to illustrate how poverty is governed by specific employment and welfare characteristics. 相似文献
56.
Robert E. Deyle 《政策研究杂志》1994,22(3):457-473
Innovation by "groping along," in which appointed public officials experiment during program implementation after little, if any, initial planning and analysis, has been promoted as a more accurate model of policy innovation than the rational comprehensive model of policy change. Analysis of two cases of environmental regulatory policy innovation suggests that administrative agencies may be more likely to follow the conventional model of the policy cycle when high levels of conflict are likely to accompany policy initiatives. The cases also suggest, however, that public officials will experiment during the innovation process when they are uncertain about the nature of the problem and the probable impacts of alternative solutions. 相似文献
57.
58.
D. E. NELSON G. CHALOUPKA C. CHIPPINDALE M. S. ALDERSON J. R. SOUTHON 《Archaeometry》1995,37(1):151-156
Accelerator mass spectrometry radiocarbon ages have been taken for a test suite of small samples of material removed from some of the ‘beeswax’art figures found in rock shelters in northern Australia. The results indicate that we can reliably date this unique form of rock art with no noticeable damage. We had not expected to find figures of any great antiquity, and so we were surprised to find that the ages obtained spanned the time period from the recent past to about 4000 BP. 相似文献
59.
A Roman archaeological site in northern Spain (La Maja, province of La Rioja) includes pottery workshops, part of an important ceramic industry that developed from about the first century BC to the first century AD. A geophysical study was planned to determine the extent of the industrial complex in the vicinity of an excavated kiln. Magnetic observations were done on a grid of 30 × 36m, with a sampling interval of 1m. Two dipolar-shaped anomalies were found: one in the north-east and the other in the south-west of the area. Low-pass and band-pass filters were used in the Fourier domain to enhance the characteristics of the magnetic data and to remove noise and undesirable shallow features. Three-dimensional polygonal prisms were used to model the magnetic anomalies based on palaeomagnetic measurements performed over an uncovered kiln that helped to constrain the induced and remanent parameters of the magnetizing fields. 相似文献
60.
In recent years, cultural anthropologists have made notable progress in understanding the bewildering variety of material exchange transactions found among the aboriginal populations of highland New Guinea. One of the major findings of this work is that competitive exchange behavior may bring in its wake alterations in agronomic practices involving an intensification of production. That intensification is primarily a product of social behavior, rather than an adaptation to climate change or population pressure, is a significant conclusion that should influence the thinking of archaeologists as they investigate past episodes of agronomic change, including the origins of agriculture. 相似文献