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   108篇
  免费   7篇
  2023年   3篇
  2021年   1篇
  2020年   4篇
  2019年   10篇
  2018年   11篇
  2017年   8篇
  2016年   4篇
  2015年   5篇
  2014年   1篇
  2013年   31篇
  2012年   4篇
  2011年   1篇
  2010年   5篇
  2009年   3篇
  2008年   3篇
  2006年   1篇
  2004年   1篇
  2003年   1篇
  2002年   2篇
  2001年   2篇
  2000年   1篇
  1997年   2篇
  1994年   2篇
  1993年   2篇
  1992年   2篇
  1986年   1篇
  1982年   1篇
  1981年   1篇
  1976年   1篇
  1969年   1篇
排序方式: 共有115条查询结果,搜索用时 31 毫秒
31.
32.
While the most famous historical green earth deposits in Italy and Cyprus were exceptionally rich in celadonite, the deposits near Kadaň, Czech Republic, consisted of thin Fe‐rich celadonite impregnations accompanied by interstratified celadonite/smectite. In superimposed tuffs, smectites become prevalent and their colour changes from forest to olive green. Powder X‐ray microdiffraction and infrared microspectroscopy permit us to distinguish between green earth minerals in microsamples taken from works of art. The Ti contents and the Fe/Mg ratios help to indicate the presence of Bohemian green earth from Kadaň. We found this material in local 18th‐century works of art and also in paintings by Anton Kern (1709–47).  相似文献   
33.
The growth of collaborative approaches to governance has resulted in increasingly complex policy and management landscapes, where actors are presented with ever‐increasing numbers of decision‐making venues they can participate in and actors they can collaborate with. Given that actors face constraints on their capacity to manage actor and venue relationships in such polycentric governance systems, we assume the marginal benefit of yet another relationship should begin to diminish at some level of engagement. Furthermore, we hypothesize that such capacity limitations are not static, but decrease as actors learn, develop skills, and formulate strategies for how to navigate complex polycentric systems more effectively. Drawing on the Ecology of Games framework, this article investigates two Swedish collaborative governance initiatives where a multitude of actors came together to address a range of different, but interrelated, policy issues and management tasks. The empirical findings suggest that actors’ capacities to successfully navigate polycentric governance arrangements increase as they gain experience and develop their networking skills. Our findings imply there is a need to balance increased complexity in polycentric systems with increased capacity, otherwise the overall effect of an ever‐increasing number of venues and actors could be collaborative fatigue and decreased abilities to address diverse governance challenges.  相似文献   
34.
We examine the influence of various political actors on the substance and timing of presidential orders. Specifically, we analyze President John F. Kennedy’s decision to issue E. O. 11063, which directed the federal bureaucracy to eliminate discrimination in the sale or lease of residential property overseen by the federal government. We show that this order did not result solely from Kennedy’s policy preferences; rather, it was a product of persuasion by several political actors who coaxed Kennedy to act. This reinforces previous findings that the president’s power of the pen is often conditioned by the informal political costs of unilateral executive action.  相似文献   
35.
Planning of transport infrastructure in Sweden has undergone successive legislative changes as well as neoliberal corporatization and marketization reforms in recent years, with a general aim to increase efficiency and effectiveness. This paper presents planning practitioners’ experiences of far-reaching marketization of physical planning practice in line with a strategy within the Swedish Transport Administration (STA) to become a ‘Pure Purchaser’. The strategy implies that all practical planning work should be carried out by procured consultants. The paper follows a qualitative, explorative approach based on document studies and interviews with practitioners actively involved in carrying out physical planning of road and rail investments. The concept of ‘modes of governance’ is applied to highlight and analytically interpret differences in perspectives on efficient and effective governance as expressed in the planning legislation, and the STA marketization strategy, respectively. The empirical results make evident that the recent marketization reforms are generally perceived as strongly and negatively affecting the efficiency and effectiveness of planning practices while also circumscribing professional discretion. The study highlights the importance of specific organization and management perspectives as explanatory factors in studying efficiency and effectiveness of planning practices.  相似文献   
36.
Pacific Islanders in diaspora are disproportionately contracting COVID-19, experience hospitalization and develop complications. In Utah, Pacific Islanders have the highest contraction rate in the state. Pacific Islanders constitute only 2% of the state's population, but represent 4% of the those infected with COVID-19, begging the question how we might explain the high rates of contraction? As community engaged scholars and practitioners, we offer discussion, insight, and commentary on the COVID-19 pandemic affecting Pacific Islanders in Utah. Grounding this discussion is a history of the Pacific Islander community as an essential workforce that dates back to the 1850s, before statehood. We argue that historical discrimination against these early Pacific Islanders shaped the way this group is racialized as essential laborers today. The authors offer this assertion along with practices and protocols that honour cultural norms of socialization, which we see is the pathway to provide safe measures that are relevant to the Utah Pasifika community.  相似文献   
37.
The most crucial parameter to be determined in an archaeological ground‐penetrating radar (GPR) survey is the velocity of the subsurface material. Precision velocity estimates comprise the basis for depth estimation, topographic correction and migration, and can therefore be the difference between spurious interpretations and/or efficient GPR‐guided excavation with sound archaeological interpretation of the GPR results. Here, we examine the options available for determining the GPR velocity and for assessing the precision of velocity estimates from GPR data, using data collected at a small‐scale iron‐working site in Rhode Island, United States. In the case study, the initial velocity analysis of common‐offset GPR profile data, using the popular method of hyperbola fitting, produced some unexpectedly high subsurface signal velocity estimates, while analysis of common midpoint (CMP) GPR data yielded a more reasonable subsurface signal velocity estimate. Several reflection analysis procedures for CMP data, including hand and automated signal picking using cross‐correlation and semblance analysis, are used and discussed here in terms of efficiency of processing and yielded results. The case study demonstrates that CMP data may offer more accurate and precise velocity estimates than hyperbola fitting under certain field conditions, and that semblance analysis, though faster than hand‐picking or cross‐correlation, offers less precision.  相似文献   
38.
Gaussian Process Regression (GPR) is a nonparametric technique that is capable of yielding reliable out‐of‐sample predictions in the presence of highly nonlinear unknown relationships between dependent and explanatory variables. But in terms of identifying relevant explanatory variables, this method is far less explicit about questions of statistical significance. In contrast, more traditional spatial econometric models, such as spatial autoregressive models or spatial error models, place rather strong prior restrictions on the functional form of relationships, but allow direct inference with respect to explanatory variables. In this article, we attempt to combine the best of both techniques by augmenting GPR with a Bayesian Model Averaging (BMA) component that allows for the identification of statistically relevant explanatory variables while retaining the predictive performance of GPR. In particular, GPR‐BMA yields a posterior probability interpretation of model‐inclusion frequencies that provides a natural measure of the statistical relevance of each variable. Moreover, while such frequencies offer no direct information about the signs of local marginal effects, it is shown that partial derivatives based on the mean GPR predictions do provide such information. We illustrate the additional insights made possible by this approach by applying GPR‐BMA to a benchmark BMA data set involving potential determinants of cross‐country economic growth. It is shown that localized marginal effects based on partial derivatives of mean GPR predictions yield additional insights into comparative growth effects across countries.  相似文献   
39.
40.
This research aims to shed light on the early stages of agricultural development in Northern Africa through the analysis of the rich macro-botanical assemblages obtained from Ifri Oudadane, an Epipalaeolithic–Early Neolithic site from North-East Morocco. Results indicate the presence of domesticated plants, cereals (Hordeum vulgare, Triticum monococcum/dicoccum, Triticum durum and Triticum aestivum/durum) and pulses (Lens culinaris and Pisum sativum) in the Early Neolithic. One lentil has been dated to 7611 ± 37 cal BP representing the oldest direct date of a domesticated plant seed in Morocco and, by extension, in North Africa. Similarities in both radiocarbon dates and crop assemblages from Early Neolithic sites in Northern Morocco and the Iberian Peninsula suggest a simultaneous East to West maritime spread of agriculture along the shores of the Western Mediterranean. Wild plants were abundantly collected in both the Epipalaeolithic and the Early Neolithic periods pointing to the important role of these resources during the two periods. In addition to fruits and seeds that could have been consumed by both humans and domesticated animals, fragments of esparto grass (Stipa tenacissima) rhizomes have been identified. This is a western Mediterranean native plant that may have been used as a source of fibres for basketry.  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