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   11762篇
  免费   309篇
财政金融   1828篇
工业经济   820篇
计划管理   1695篇
经济学   2125篇
综合类   119篇
运输经济   69篇
旅游经济   153篇
贸易经济   1493篇
农业经济   475篇
经济概况   1070篇
水利工程   2202篇
信息产业经济   1篇
邮电经济   21篇
  2021年   98篇
  2020年   142篇
  2019年   218篇
  2018年   279篇
  2017年   279篇
  2016年   293篇
  2015年   171篇
  2014年   263篇
  2013年   1076篇
  2012年   428篇
  2011年   430篇
  2010年   332篇
  2009年   371篇
  2008年   405篇
  2007年   390篇
  2006年   433篇
  2005年   321篇
  2004年   333篇
  2003年   219篇
  2002年   237篇
  2001年   234篇
  2000年   245篇
  1999年   214篇
  1998年   221篇
  1997年   209篇
  1996年   219篇
  1995年   185篇
  1994年   180篇
  1993年   187篇
  1992年   195篇
  1991年   198篇
  1990年   185篇
  1989年   145篇
  1988年   127篇
  1987年   126篇
  1986年   137篇
  1985年   196篇
  1984年   158篇
  1983年   146篇
  1982年   120篇
  1981年   144篇
  1980年   136篇
  1979年   133篇
  1978年   139篇
  1977年   74篇
  1976年   102篇
  1975年   78篇
  1974年   73篇
  1973年   75篇
  1972年   71篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The practical significance of the conventional “net farm income” is elusive. It would be useful to have an accepted method of dividing “management and investment income” into its recognised Components—managerial salary and return on tenant's capital. One is a residual if the other can be calculated, and both alternatives are considered. An empirical formula is suggested for estimating the managerial salary which may be imputed to the farmer, taking account of his total turnover, his labour bill and his net farm income. This formula is then applied to Farm Management Survey data, for individual farms and for groups of average, high and low performance (output per £ input). The method may permit closer analysis of relative profitability.  相似文献   
992.
993.
994.
995.
996.
997.
Gravitational collapse in response to the creation of salt swells and diapirs is a common phenomenon within regions such as the Southern North Sea. Although collapse faulting and slumping of linear salt swell flanks has previously been documented, the existence of concentric collapse structures surrounding diapirs and isolated salt lows is a recently recognised feature. 3-D seismic data from the Southern North Sea demonstrates that concentric collapse faulting around both diapirs and subcircular salt lows is common. The recognition of concentric collapse structures formed in response to salt withdrawal, and adjacent inflation, provides an alternative mechanism for the origin of the proposed Silverpit impact crater.  相似文献   
998.
A population sample from a community in a developing urban area (Botshabelo), which obtains its treated water supply from a communal standpipe system, was subjected to a short Health and Hygiene Awareness and Education (HHA&E) programme to improve its practices on storing water in, and handling water from, storage containers at home. The problem was that the community's practices lead to the deterioration of the microbiological quality of the water in domestic storage containers. Measuring changes in the practices, as well as the microbiological quality of water in the containers, were the instruments used to determine whether the programme had a positive educational effect. This paper reports on selected elements of the practices measurement. Structured interviews, observations and statistical analyses assessed three variables--container hygiene, container storage and hand hygiene. Results indicated insignificant improvements in practices. This was supported by insignificant improvements in the microbiological water quality, that was still above health-safety limits. This implied that short-term "quick fix" HHA&E programmes would tend to be ineffective. Results also suggested that some negative water-hygiene habits may readily change (container hygiene and storage), while behaviour of a more personal nature, such as hand-washing, was not easily changed.  相似文献   
999.
Environmental engineering education at universities is a rapidly changing field globally. Traditionally it has resided in the civil engineering program addressing water and wastewater quality, treatment, design and regulatory issues. In recent years environmental engineering has become a much broader field encompassing water, wastewater, soil pollution, air pollution, risk assessment, ecosystems, human health, toxicology, sustainable development, regulatory aspects and much more. The need to introduce environmental engineering/green engineering/pollution prevention/design for the environment concepts to undergraduate engineering students has become recognized to be increasingly important. This need is being driven in part through the US Engineering Accreditation Commission Accreditation Board for Engineering and Technology criteria 2000. Thus there has been a major shift in environmental engineering education and it no longer resides only within the civil engineering discipline. This paper focuses on the development of innovative curricula for a brand new engineering program at Rowan University that integrates environmental education for all engineers. A common course known as "engineering clinic" was developed for all engineering students throughout their eight semesters of engineering education. One of the clinic goals is to integrate engineering design and the environment. The program, in its seventh year, indicates successful implementation of environmental education in all four engineering disciplines in their course work and clinics.  相似文献   
1000.
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