全文获取类型
收费全文 | 4741篇 |
免费 | 169篇 |
出版年
2020年 | 50篇 |
2019年 | 104篇 |
2018年 | 115篇 |
2017年 | 119篇 |
2016年 | 135篇 |
2015年 | 104篇 |
2014年 | 93篇 |
2013年 | 1420篇 |
2012年 | 148篇 |
2011年 | 130篇 |
2010年 | 153篇 |
2009年 | 159篇 |
2008年 | 95篇 |
2007年 | 118篇 |
2006年 | 106篇 |
2005年 | 61篇 |
2004年 | 61篇 |
2003年 | 58篇 |
2002年 | 67篇 |
2001年 | 69篇 |
2000年 | 55篇 |
1999年 | 67篇 |
1998年 | 69篇 |
1997年 | 52篇 |
1996年 | 57篇 |
1995年 | 49篇 |
1994年 | 52篇 |
1993年 | 47篇 |
1992年 | 42篇 |
1991年 | 40篇 |
1990年 | 26篇 |
1989年 | 45篇 |
1988年 | 39篇 |
1987年 | 51篇 |
1986年 | 40篇 |
1985年 | 46篇 |
1984年 | 54篇 |
1983年 | 48篇 |
1982年 | 36篇 |
1981年 | 44篇 |
1980年 | 56篇 |
1979年 | 48篇 |
1978年 | 31篇 |
1977年 | 52篇 |
1976年 | 36篇 |
1975年 | 41篇 |
1974年 | 24篇 |
1972年 | 27篇 |
1970年 | 24篇 |
1969年 | 25篇 |
排序方式: 共有4910条查询结果,搜索用时 78 毫秒
1.
Evidence from several disciplines supports the proposition that following the Wisconsinan and an initial but brief moist phase of the Holocene, there was a gradual drying trend in the mid-continent Prairie Peninsula that peaked about 7000 years ago, a pattern that was not reversed until about 4000 years ago. Except for minor perturbations, conditions during the past four millennia have essentially been similar to those of the present. Studies in palynology and geomorphology have shown that the climatic regimes of the early/mid Post-glacial had a marked influence on both the biota and landscape erosional patterns, especially along the margins of the Prairie Peninsula. Measurable changes in the landscape and attendant biota show a time-transgressive pattern of drought related phenomena recorded palaeo-ecologically from west to east.Few studies of archaeological sites in the Prairie Peninsula have examined the evidence in and around the sites themselves for data reflecting local environmental dynamics. In fact, earlier models proposed for explaining the evolution of food-procuring systems in eastern North America virtually ignored potential changes in the natural environment. This paper examines data from two archaeological sites along the prairie-forest border in Missouri that contain long cultural sequences. Evidence is presented that pronounced changes in the natural environment occurred and that these biophysical variables are indeed critical for understanding the evolution of food-procuring societies in the American Midwest. 相似文献
2.
Geographic research on neoliberalism has explored the restructuring of educational landscapes wrought through marketisation of preschool, school and higher-education provision and considered the responsibilisation of parents and children for educational outcomes. This study develops understanding of the contingent emergence of neoliberal educational reform, and its progressive and regressive impacts, through an examination of the burgeoning private tuition market in England and Wales. The paper outlines the contours of the previously hidden supplementary education industry, demonstrating that it reinforces regional and classed inequalities, while opening possibilities for ethnic minority advancement. Conceptually, the paper advances debate about socio-spatial specificity in neoliberal change, showing that the intersection of policy, free markets and consumer behaviour reshapes the educational landscape in ways that extend beyond state intention and control. Through these processes, contingent market forms are produced that offer social mobility for some, but ensure the social reproduction of enduring regimes of power. 相似文献
3.
4.
5.
6.
7.
8.
9.
10.