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   977篇
  免费   34篇
  1011篇
  2023年   5篇
  2021年   3篇
  2020年   16篇
  2019年   13篇
  2018年   32篇
  2017年   32篇
  2016年   36篇
  2015年   29篇
  2014年   36篇
  2013年   255篇
  2012年   27篇
  2011年   25篇
  2010年   20篇
  2009年   32篇
  2008年   38篇
  2007年   31篇
  2006年   16篇
  2005年   21篇
  2004年   9篇
  2003年   12篇
  2002年   21篇
  2001年   20篇
  2000年   12篇
  1999年   14篇
  1998年   10篇
  1997年   14篇
  1996年   10篇
  1995年   8篇
  1994年   8篇
  1993年   13篇
  1992年   5篇
  1991年   10篇
  1990年   9篇
  1989年   10篇
  1988年   5篇
  1987年   8篇
  1986年   9篇
  1985年   10篇
  1984年   19篇
  1983年   11篇
  1982年   9篇
  1981年   10篇
  1980年   7篇
  1979年   15篇
  1978年   9篇
  1977年   10篇
  1976年   4篇
  1975年   10篇
  1974年   4篇
  1972年   5篇
排序方式: 共有1011条查询结果,搜索用时 0 毫秒
81.
Recent research has studied the effects of seasonal variability on waterlogged burial environments. In a new approach to the study of archaeological contexts, the use of controlled laboratory conditions via lysimeters has enabled new insights into the nature of short term fluctuations in saturation, and the impact that these can have on burial contexts. In addition, the protocols used have facilitated interesting insights into burial environments and the way in which fluctuations in saturation and seasonality can impact on the contained organic components within them.  相似文献   
82.
The advertising of unhealthy food and beverages forms an important component of obesogenic environments. Such marketing to children is a key health determinant because of its impact on dietary preference and food purchasing behaviour. The location of outdoor advertising is important in exploring obesogenic environments and children's neighbourhoods. The aim of this study is to explore issues involved in the use of Google Street View to examine outdoor food and beverage advertising. The implications for using Google Street View in the context of neighbourhood built environment research and grass‐roots advocacy are discussed. The study was conducted within walkable distances from 19 primary and intermediate schools in Auckland, New Zealand, where “walkable” was defined as limited by 800 m road network boundaries, which are equivalent to school buffer boundaries. Google Street View allows for centrality of data collection, coding, and storage. However, challenges exist with the method because 727 (29.4%) of a total of 2,474 outdoor advertisements that were identified were not able to be categorised because images were unclear, not in English, blocked, or at angles where detail cannot be deciphered. Specific to outdoor advertising for food and beverages, the results presented here show that children are exposed to a significantly greater number of unhealthy advertising than other advertising, P=0.001, eta‐squared statistic (0.45) indicates a large effect size. Overall, the results show promise for the use of Google Street View in the study of obesogenic environments.  相似文献   
83.
84.
Scholars have been studying the concept of public engagement and its role in the policy process for some time. Scholars have argued that understanding the interests and motivations of the public and engaging them in the decision‐making process can lead to better policy designs and, ultimately, better policy outcomes. However, studies of public engagement often assume that people have a desire to get involved in the policy process. This paper tests this key assumption using the case of nuclear facility siting in the United States to ask: what factors influence an individual's stated willingness to want to engage in the policy process? Using data from a national web survey fielded in 2013, we ask the public if and to what extent they would likely engage in the siting process if given the opportunity. Findings indicate that the likelihood of engagement varies rather substantially across individuals. We find that an individual's cultural belief system and existing level of political activity account for some of this variation. These findings suggest that public engagement programs may vary across groups and communities. In other words, the prospects of engagement are likely to appeal to some members of the population and not others.  相似文献   
85.
ABSTRACT The spatial intensities of both industries and population are highly uneven across space. Moreover, these intensities differ not only across industries, but also change through time. Nevertheless, we show using Japanese data for metropolitan areas in two time periods that the location intensities of both industries and population are linked by surprisingly simple and persistent patterns. In particular, we identify a strong negative log‐linear relation between the number and the average (population) size of metro areas in which a given industry is found. This relation, which we designate as the Number‐Average Size (NAS) Rule, is also shown to be intimately connected to both the Rank‐Size Rule and Christaller's (1966) Hierarchy Principle applied to metropolitan areas. In particular, we show mathematically that in the presence of the Hierarchy Principle (which holds quite well in Japan) this NAS Rule is essentially equivalent to the Rank Size Rule.  相似文献   
86.
Ron J. Smith 《对极》2016,48(3):750-769
Scholars have argued that in attempts to achieve geopolitical goals, siege often results in covert assaults against civilian populations. In the Gazan context, siege subjects are rendered as surplus to the Israeli state, and are therefore isolated and deprived of basic human needs as well as human rights. In 2006, siege was enacted against Gaza, enforced by the Egyptian and Israeli militaries. As a consequence, the population of Gaza is isolated from the exchange of goods, services, people, and ideas. This article begins with an analysis of siege as a violent process and as a subset of occupation practices. Using ethnographic data collected in Gaza between 2009 and 2014, this article mobilizes the methods and approach of subaltern geopolitics to undermine the notion of siege as a humanitarian alternative to war. This study reveals the micro‐scale, graduated nature of siege and its impacts on the civilians living in Gaza.  相似文献   
87.
In Part I of this paper (Smith and Hsieh, 1997) a programming formulation of steady states was developed for gravity-type interactive Markov chains in terms of their associated spatial-flow chains. These results are here applied to analyze the stability properties of interactive Markov chains. In particular, the objective function for this programming formulation is shown to constitute a Lyapunov function for an appropriately defined continuous-time version of spatial-flow chains. The Lyapunov stability properties of these spatial flows are then shown to yield corresponding stability properties for the continuous-time versions of interactive Markov chains. In particular, these processes always exhibit global convergence to steady states. Finally, it is shown that when steady states are unique, these convergence results are inherited by those interactive Markov chains that are 'sufficiently close' to their continuous-time versions.  相似文献   
88.
89.
Fragments of plastron and vertebrae from the Griman Creek Formation (middle Albian) at Lightning Ridge, New South Wales, extend the Australian record for chelid pleurodires back in time by over 50 my. Contemporaneous with the oldest known occurrences of chelids in Patagonia, this record indicates that during globally warm intervals, pleurodire distribution included high palaeolatitude locations. Although referred to Chelidae, the material shows no characters to enable more detailed taxonomic assessment and it is unclear whether known genera are represented. The diverse and prolonged history of chelids in South America and Australia indicates that the basal eupleurodiran divergence occurred deep in the Jurassic.  相似文献   
90.
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