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   475篇
  免费   25篇
  2021年   2篇
  2020年   9篇
  2019年   15篇
  2018年   17篇
  2017年   16篇
  2016年   25篇
  2015年   14篇
  2014年   11篇
  2013年   137篇
  2012年   17篇
  2011年   14篇
  2010年   8篇
  2009年   16篇
  2008年   7篇
  2007年   9篇
  2006年   10篇
  2005年   5篇
  2004年   10篇
  2003年   6篇
  2002年   9篇
  2001年   4篇
  2000年   5篇
  1999年   5篇
  1998年   6篇
  1997年   5篇
  1995年   8篇
  1994年   4篇
  1993年   3篇
  1991年   5篇
  1990年   2篇
  1989年   3篇
  1988年   2篇
  1986年   3篇
  1985年   6篇
  1984年   8篇
  1983年   5篇
  1982年   6篇
  1981年   4篇
  1980年   7篇
  1979年   5篇
  1978年   6篇
  1977年   3篇
  1976年   5篇
  1975年   4篇
  1974年   4篇
  1973年   4篇
  1972年   3篇
  1971年   2篇
  1969年   4篇
  1948年   2篇
排序方式: 共有500条查询结果,搜索用时 15 毫秒
71.
In this paper, we explore regional innovation in the use of varieties of algae as inputs to industrial processes. It is important to understand that algae are one of nature's most bountiful products, with an almost infinite variety of applications. Algae have received prominence in the research literature because of the strong evidence that they can make a major contribution to the production and—importantly—storage of renewable energy. Following the introduction to this paper, Section 2 reviews the nature and application of algae in two main aspects of clean energy production: first as biogasolene or biodiesel; second as large-scale storage batteries for electricity. The latter is particularly important as one classic deficiency of electricity is the difficulty in storing it for lengthy periods other than in short-life batteries. However (Section 3), there are other uses for algae, ranging from aquaculture to medicine and the production of cosmetics. In the southwest corner of the Iberian Peninsula, between Faro in Portugal through Huelva to Cadiz in Spain, is a significant research and commercial algae production zone. The paper describes the key system elements in play in this trans-border innovation network and considers prospects for new path creation towards biofuels, the main research and application centres for which are in the San Francisco Bay Area in California. Conclusions and recommendations for policy action are then drawn.  相似文献   
72.
A set of contemporary and increasingly urgent environmental problems in the USSR are surveyed, emerging as a result of continued development and technological change and mandating, in effect, a new environmental agenda. Analysis of specific problems reveals ways in which the new agenda must differ from the old: it must be more ecologically based, more comprehensive, and more global in scope. A concluding section examines how this agenda appears to be evolving over time, and identifies components which will be essential in order for it to effectively address the environmental challenges of the next century.  相似文献   
73.
74.
This article recovers the global history of the English millennial religion of Southcottianism. After Joanna Southcott died in 1814, leaving thousands of English followers still expecting the millennium that she prophesied, elements of her movement generated further prophets and a dynamic missionary division known as “Israelite Preachers.” From the 1820s onwards, these preachers took Southcott's ideas and new doctrines developed by her successor, John Wroe, throughout the British Isles, then the English‐speaking world, most notably Australia and North America. Drawing mission approaches (and recruits) from revivalist dissent, Israelite preachers forged first a Britain‐wide sect, then a global movement which followed the British settler diaspora and competed with rival American millennialisms. The spread of Southcottianism is a forgotten episode in the story of nineteenth‐century British colonial missions, and an argument for examining millennial movements beside more mainstream Christianity.  相似文献   
75.
76.
Single‐sheet charters and coin epigraphy provide valuable evidence for the development of representations of the Old English dental fricative in the seventh and eighth centuries. This evidence indicates differing Kentish and Mercian practices up to the 780s, when scribes in both areas rapidly adopt <ð> to represent this sound. In Kent, occasional experimentation with this character from perhaps as early as the reign of Eadbald (616–40 ad ) may suggest a lengthy period of gradual adoption prior to the rapid increase. Mercian practice instead shows an abrupt adoption, which is perhaps the result of reform according to external (perhaps Kentish) models.  相似文献   
77.
78.
79.
Abstract

Documentary evidence reveals that, when in 1395 the Purbeck marble tomb with gilt cast copper-alloy effigies commemorating Richard II and his queen, Anne of Bohemia, was installed in St Edward the Confessor's Chapel in Westminster Abbey, another tomb was moved to make room for it. It has commonly been supposed that the displaced tomb was the Cosmatesque tomb chest now in the south ambulatory, which has traditionally been believed to house the bones of Katherine, daughter of Henry III, and up to eight other royal infants and older children of Henry III and Edward I. Examination of the evidence indicates that neither part of this view is correct. Three other tombs may have been moved from the Confessor's chapel; of these, the highstatus monument to William de Valence is the most likely candidate for the tomb displaced in 1395.  相似文献   
80.
SURVEY of a field, immediately north of the early Norman motte-and-bailey castle of Hen Domen, Montgomery, revealed ridge-and-furrow, averaging 4 m. in width, cut by the outer ditch of the bailey. Excavation demonstrated that the ridge-and-furrow extended under the inner rampart of the bailey. Pollen analysis of the buried soil showed the former presence of cereals and the weeds of cultivation. A Carbon-14 date from charcoal in the buried soil reinforced the view that this field-system was in use before the Norman conquest.  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