首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   502篇
  免费   28篇
  2023年   3篇
  2020年   6篇
  2019年   12篇
  2018年   11篇
  2017年   17篇
  2016年   21篇
  2015年   17篇
  2014年   13篇
  2013年   160篇
  2012年   19篇
  2011年   17篇
  2010年   10篇
  2009年   12篇
  2008年   13篇
  2007年   8篇
  2006年   14篇
  2005年   5篇
  2004年   15篇
  2003年   4篇
  2002年   4篇
  2001年   4篇
  2000年   8篇
  1999年   10篇
  1998年   4篇
  1997年   5篇
  1995年   6篇
  1994年   3篇
  1993年   4篇
  1992年   3篇
  1991年   5篇
  1990年   4篇
  1989年   6篇
  1988年   7篇
  1987年   6篇
  1986年   4篇
  1985年   5篇
  1984年   11篇
  1983年   3篇
  1982年   5篇
  1978年   3篇
  1976年   2篇
  1974年   3篇
  1973年   4篇
  1972年   3篇
  1971年   5篇
  1970年   2篇
  1969年   3篇
  1968年   2篇
  1954年   3篇
  1949年   2篇
排序方式: 共有530条查询结果,搜索用时 15 毫秒
471.
This paper examines the trends in residential segregation by income (post-transfer, pretax income) in the thirty-nine largest Canadian urban areas between 1991 and 1996. The study is motivated by the relative lack of attention paid to residential segregation by income in the Canadian context and by conceptual arguments linking compromised life chances and increased social tensions for the populations of highly segregated cities. We investigated several dimensions of segregation using five different measures (we focus on three of these here given the correlation structure of the measures) to examine changes in segregation between 1991 and 1996, a period characterised by economic recession, cutbacks in social programs and a widening of inequality in market incomes at the national scale. Overall, income segregation increased in most urban areas across all dimensions of segregation during the time period, with particularly high degrees of segregation observed in prairie cities (Winnipeg, Saskatoon and Regina). Of the three largest metropolitan areas (Vancouver, Toronto and Montréal), Montréal was the most consistently segregated. We also find that increases in spatial separation and spatial concentration by income occurred despite the fact that at the national scale, the tax and transfer system appeared to be adequately redressing a rise in inequality in labour and market incomes (as demonstrated by the lack of change in post-transfer national income inequality measures during a period when inequality in market and labour incomes rose sharply). This implies that the lived experience of changes in income distribution are unlikely fully captured by aspatial, national-scale measures and that intra-urban measures with a spatial dimension are an important indicators of inequality in Canadian society.  相似文献   
472.
This article examines the place of religious values in the thinking of leading figures in the mainstream German women's movement in the period before World War I. Focusing on the debate of sexual morality and abortion within the German League of Women's Associations, it argues that the position taken by these women is best understood as a product of their religious commitments, rather than their political ideas. The article seeks to place these women in the historical context of a particular liberal, Protestant, social and intellectual milieu that flourished in the period before 1914.  相似文献   
473.
474.
In recent years, an apparent increase in the frequency and severity of floods in the UK has led to growing concerns about societal exposure and vulnerability to flooding, particularly in the context of climate change, floodplain development and changing insurance practices. Despite the important link between assessments of exposure to flooding (hazard assessments) and issues of societal vulnerability, this link has rarely been explored in detail and has often been reflected in policy terms by a highly technocratic approach to flood risk management. Indeed, more comprehensive studies have usually favoured rigid and deterministic definitions of vulnerability, in keeping with the wider technocratic paradigm pervading management institutions. In an attempt to redress the balance, this paper considers the role of hazard assessment and issues of societal vulnerability as mutually informative debates and advocates a movement away from the technocratic ideals currently favoured in the UK.  相似文献   
475.
Comparisons were made between two commonly used methods for the extraction of ancient DNA from charred plant remains. Using artificially charred wheat seeds, we show that silica-binding is the most efficient method for extraction of DNA. We describe a improved silica-binding procedure, including pre-incubation with N-phenacylthiazolium bromide and increased washing of bound DNA, which yields amplifiable DNA from seeds heated at 200 °C for up to 8 h, conditions which promote the formation of Maillard products which often copurify with aDNA and inhibit subsequent PCRs. We believe that this method will be effective in ancient DNA extraction with most types of charred archaeobotanical material. Both cold- and hot-start PCR procedures gave good amplicon yields with extracts prepared in this way, but cold-start PCRs also resulted in synthesis of short artefact products. Addition of bovine serum albumin to PCRs, an inert carrier substance thought to enhance amplification efficiency by binding contaminants, had no advantageous effect and in fact reduced amplicon synthesis.  相似文献   
476.
Scavenging is one of the primary taphonomic processes shaping the final composition of fossil faunal assemblages. The taphonomic effect of scavengers is variable and must be understood in the context of the causes of that variation. In this study, we investigated relationships between the El Niño Southern Oscillation (ENSO), variable rainfall and scavenging on 20–40 kg mammal carcasses in semi‐arid New South Wales over four years. Following periods of above‐average rainfall (coincident with the La Niña phase of the ENSO), there was an increased availability of non‐carrion food and scavenging activity was moderate. Following below‐average rainfall (coincident with the El Niño phase of the ENSO), foraging options diminished, leading to a greater importance of carrion in the diet of scavengers and a resultant increase in carcass disturbance, transport and destruction by scavengers. Feral pigs (Sus scrofa) and red foxes (Vulpes vulpes) were the most taphonomically significant scavengers in the study. Australian ravens (Corvus coronoides) and wedge‐tailed eagles (Aquila audax) were active scavengers throughout the period of the study, but had little impact on bone survival. Lace monitors (Varanus varius) also fed mostly on soft tissue and were only present seasonally. We found that climate variability in the form of short‐term oscillation can result in significant variation in the impact of scavengers on carcasses and may be an important consideration when evaluating site formation scenarios and biases in fossil faunal assemblages. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
477.
478.
The World Food Programme (WFP) is currently the largest and arguably one of the most successful of the United Nations Special Agencies, yet there has been little examination of it by international relations scholars since the early 1990s. This article seeks to analyse the normative and political characteristics of the WFP which have contributed to its effectiveness. Among its most significant findings is that American agricultural interests, interpreted through the prism of domestic political norms, have dovetailed with ‘feed-the-hungry’ norms that are projected and implemented by the WFP, resulting in the strong support of the United States for the WFP. This support undermines the perception, promoted by some critics, that the UN is incapable of acting in ways that are compatible with the national interests of the United States and other significant member-states who inherently pursue ‘national interests’ in institutional environments.  相似文献   
479.
Andrew Sherratt included horseback riding and chariotry in his conception of the Secondary Products Revolution, but his emphasis on the role of horses in warfare and on a Near Eastern influence in the earliest episode of horse domestication is viewed here as as an important shortcoming in his understanding of the process of horse domestication. Current evidence indicates that horses were domesticated in the steppes of Kazakhstan and Russia, certainly by 3500 BC and possibly by 4500 BC. Tribal raiding on horseback could be almost that old, but organized cavalry appeared only after 1000 BC. Riding might initially have been more important for increasing the productivity and efficiency of sheep and cattle pastoralism in the western Eurasian steppes. The earliest (so far) direct evidence for riding consists of pathologies on the teeth and jaw associated with bitting, found at Botai and Kozhai 1. Recent developments and debates in the study of bit-related pathologies are reviewed and the reliability of bit wear as a diagnostic indicator of riding and driving is defended.  相似文献   
480.
The English 'sexual revolution' has recently become increasingly conceived as 'long', lasting many decades, and by some historians as a gradual phenomenon, but reaching a peak with the introduction of the oral contraceptive pill in the 1960s. At the same time, the 'religious crisis' of the same decade has been attributed by some recent scholarship to liberal Christian revolt within the churches, and largely unconnected with sex. This article offers different views. First, based on the illegitimacy rate, it argues that, after a period of decline, restraint, and only minor change in the period 1946-59, the 1960s witnessed a sudden growth in pre-marital heterosexual intercourse before the pill's availability to single women, implying a cultural rather than a technological cause. Second, based on contemporary social surveys, it argues that there is clear evidence of a strong inverse correlation between levels of religious activity and levels of pre-marital sexual intercourse. Third, it argues that in the 1950s the dominant conservative Christian culture restrained single women from pre-marital sexual intercourse, but that from the early 1960s changing attitudes led to rising levels of sexual activity, led by single women, which reduced religious attitudes and Christian churchgoing, thus constituting a significant instigator of the religious crisis.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号