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   149篇
  免费   2篇
  2019年   2篇
  2018年   3篇
  2017年   6篇
  2016年   3篇
  2015年   9篇
  2014年   3篇
  2013年   50篇
  2012年   8篇
  2011年   5篇
  2010年   2篇
  2009年   1篇
  2008年   4篇
  2007年   5篇
  2006年   3篇
  2004年   3篇
  2003年   2篇
  2002年   3篇
  2001年   1篇
  1999年   1篇
  1998年   2篇
  1997年   2篇
  1995年   2篇
  1994年   2篇
  1993年   1篇
  1991年   2篇
  1989年   1篇
  1988年   1篇
  1987年   1篇
  1986年   2篇
  1985年   3篇
  1983年   1篇
  1981年   1篇
  1979年   1篇
  1978年   3篇
  1977年   1篇
  1976年   1篇
  1975年   2篇
  1974年   1篇
  1973年   1篇
  1972年   1篇
  1971年   1篇
  1969年   1篇
  1968年   1篇
  1967年   2篇
排序方式: 共有151条查询结果,搜索用时 15 毫秒
131.
132.
Geographical variation operates at a variety of scales. Methods of mapping variation in disease incidence between different countries or even counties are relatively well developed. When, however, the question relates to much smaller aggregations (that is, “clustering”), attention has mainly been restricted to areas near putative point hazards; the majority of cases are excluded from such an investigation. In this study we show how clustering may be investigated and displayed in such a way that it becomes a powerful tool in epidemiological research. As examples we use incidence data from the Yorkshire health region for selected childhood cancers and adult haematopoietic malignancies. The methods would readily extend to any small clusters of rare events.  相似文献   
133.
In this paper, an unresolved boundary dispute in the Gulf of Maine, between the United States and Canada, in an area known as the Grey Zone is examined. In the context of a juridically weak framework of principles for determining international maritime boundaries, the case of a small fishing community caught between conflicting national interests and a lucrative fishing zone being claimed by both countries is examined. Left unresolved with the 1984 International Court of Justice decision defining the 'Hague Line', this dispute is made more problematic because of ambiguous objectives and conflicting agendas between national governments, between state and community levels and within the community itself.  相似文献   
134.
Longstanding observations about the relationship between increasing aridity and 15N enrichment in mammalian collagen values have led to an interest in their use as a paleoclimatic marker. Here we report on variability in collagen nitrogen values from five modern and two archaeological samples of black-tailed jackrabbits (Lepus californicus) from the eastern Great Basin of the United States (N = 178 individuals). Nitrogen δ15N values were highly variable within all samples. Modern samples showed significant differences despite similarities in average annual precipitation and temperature. Archaeological samples were indistinguishable from each other or from modern samples taken from the same area despite independent evidence for differences in precipitation for the two prehistoric periods considered. Differences between modern samples were most strongly associated with soil characteristics. We discuss these results in light of their relationship with topography and vegetation and highlight their implications for archaeological applications of stable nitrogen analyses in several contexts.  相似文献   
135.
136.
This is an invited to response to K. Ryan’s comments on Coltrain et al. (2004) and Coltrain (2009). Both publications present stable isotope data and AMS radiocarbon dates on a suite of eastern Arctic burials from three sites in north-western Hudson Bay. In these articles, we examined the importance of bowhead whaling among Thule foragers at Silimiut and Kamarvik and contrasted their subsistence strategies with those of the proto-historic Sadlermiut, using the stable and radio-isotope chemistry of purified bone collagen to monitor variability in resource acquisition over time. Ryan dismisses a Dorset-era radiocarbon date on a burial collected by Collins from the T-1 site asserting that a single radiocarbon measurement is not a reliable indicator of age and thus the burial is Sadlermiut not Dorset. She also contests our assessment that two historic-era individuals in the Sadlermiut mortuary assemblage were either European or consumed diets relatively high in European foods. Ryan further argues that our reconstruction of protohistoric Sadlermiut diets is not in keeping with the archaeofaunal record. Her primary concern is a perceived lack of agreement between a subset of our findings and the archaeological record.  相似文献   
137.
138.
Our ongoing investigation of early maize farming in the American Southwest has entailed stable isotope analysis and accelerator radiocarbon dating of Basketmaker II remains from sites in the Four Corners region. Here we report radiocarbon dates on a large mortuary assemblage excavated by Richard Wetherill in 1893 from a burial cave in southeastern Utah. It has long been thought that all individuals interred in Cave 7 were massacred in a single violent attack given embedded projectiles and evidence for blunt force trauma. However, accelerator radiocarbon dates on purified bone collagen (n = 96) do not lend strong support to this argument, even among the subset of individuals with clear evidence for violent injuries. Moreover, nearly 80% of Cave 7 burials examined in the study show no evidence of perimortem trauma and no adult females or subadults under the age of 12 appear to have suffered violent deaths. Rather than an anomalous single-event massacre, the Cave 7 radiocarbon dataset suggests that raiding and intra-group, male/male violence was episodic among Basketmaker groups in southeastern Utah. Population densities were relatively high and individuals interred in Cave 7 and elsewhere in the region were heavily dependent on maize agriculture, a prehistoric economic strategy typically characterized by high amplitude fluctuations in productivity. Variability in the array of grave goods accompanying Cave 7 male burials and elsewhere suggests competitive social differentiation likely heightened during periods of resource shortfall leading to intra-group conflict, raiding and perhaps ritualized acts of violence.  相似文献   
139.
In the debate over Western Europe??s Middle to Upper Palaeolithic transition we need to consider the importance of both the chronology and the ecological context of the different techno-complexes, as well as the organization of production and consumption activities. In this article we study the adaptative strategies of Middle Palaeolithic human communities based on the information obtained from archaeological sites north of the river Ebro. This transition in the northern part of the peninsula presents a chronological and geographic dichotomy, with the appearance of the Upper Palaeolithic and survival of the Middle Palaeolithic. The geographic distribution appears to indicate intergroup competition and the existence of contact, albeit of an unverified nature. This competition would explain the time that elapsed before one of the cultural, and perhaps biological, groups triumphed over the other in a process culminating in the expansion of Upper Palaeolithic technology.  相似文献   
140.
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