全文获取类型
收费全文 | 1869篇 |
免费 | 55篇 |
专业分类
1924篇 |
出版年
2020年 | 19篇 |
2019年 | 45篇 |
2018年 | 36篇 |
2017年 | 49篇 |
2016年 | 56篇 |
2015年 | 46篇 |
2014年 | 45篇 |
2013年 | 692篇 |
2012年 | 30篇 |
2011年 | 28篇 |
2010年 | 49篇 |
2009年 | 47篇 |
2008年 | 48篇 |
2007年 | 36篇 |
2006年 | 27篇 |
2005年 | 17篇 |
2004年 | 24篇 |
2003年 | 26篇 |
2002年 | 23篇 |
2001年 | 25篇 |
2000年 | 22篇 |
1999年 | 20篇 |
1998年 | 21篇 |
1997年 | 20篇 |
1996年 | 15篇 |
1995年 | 16篇 |
1994年 | 12篇 |
1993年 | 17篇 |
1992年 | 16篇 |
1991年 | 13篇 |
1990年 | 15篇 |
1989年 | 17篇 |
1988年 | 19篇 |
1987年 | 21篇 |
1986年 | 24篇 |
1985年 | 26篇 |
1984年 | 16篇 |
1983年 | 31篇 |
1982年 | 19篇 |
1981年 | 14篇 |
1980年 | 13篇 |
1979年 | 22篇 |
1978年 | 14篇 |
1977年 | 14篇 |
1976年 | 13篇 |
1975年 | 12篇 |
1974年 | 12篇 |
1973年 | 10篇 |
1972年 | 13篇 |
1969年 | 11篇 |
排序方式: 共有1924条查询结果,搜索用时 0 毫秒
21.
22.
23.
24.
OPTIMALITY OF RECYCLING AND THE LOCATION OF A RECYCLING CENTER 总被引:1,自引:0,他引:1
ABSTRACT. Consider a community investigating the integration of recycling into its waste management program. Even if (1) the county's citizens do not gain utility from recycling, (2) landfill space is plentiful, and (3) the market price for recyclables is zero, recycling can still be optimal for a local government. By determining the relationship between the amount of recycling and the location of a recycling center, conditions are identified under which recycling will reduce total waste management costs enough that municipal recycling will be optimal. In addition, it is shown that the likelihood of municipal recycling increases with the size of the city. 相似文献
25.
Robert E. Deyle 《政策研究杂志》1994,22(3):457-473
Innovation by "groping along," in which appointed public officials experiment during program implementation after little, if any, initial planning and analysis, has been promoted as a more accurate model of policy innovation than the rational comprehensive model of policy change. Analysis of two cases of environmental regulatory policy innovation suggests that administrative agencies may be more likely to follow the conventional model of the policy cycle when high levels of conflict are likely to accompany policy initiatives. The cases also suggest, however, that public officials will experiment during the innovation process when they are uncertain about the nature of the problem and the probable impacts of alternative solutions. 相似文献
26.
Robert Steffens 《Berichte zur Wissenschaftsgeschichte》1995,18(4):259-260
27.
28.
This paper describes the results of a study investigating cross‐border networking by enterprises in the border region where the Netherlands, Belgium and Germany meet, the so‐called Euregion Maas‐Rhine. The study was undertaken in view of the completion of the Single European Market in 1993, which was expected to induce enterprises to make more effective use of available opportunities to improve their innovative and hence competitive potential. Special attention was given to knowledge transfer and sourcing of technology across borders. It was found that the majority of enterprises are still oriented towards a purely national environment. Technology‐intensive enterprises that are engaged in cross‐border networking, however, seem to be doing better than the ones that maintain a national orientation. 相似文献
29.
After over a century of archaeological research in the American Southwest, questions focusing on population aggregation and abandonment continue to preoccupy much of Pueblo archaeology. This article presents a historical overview of the present range of explanatory approaches to these two processes, with a primary focus on population aggregation in those regions occupied by historic and prehistoric Pueblo peoples. We stress the necessarily complementary nature of most of these explanations of residential abandonment and aggregation. Case studies from the northern Southwest illustrate the continuous nature of these processes across time and space. We suggest that additional explanatory potential will be gained by the use of well-defined theoretical units to frame our current approaches. We extend the use of the local community concept as a theoretical unit of organization that, along with explicit archaeological correlates, should help advance our research into population aggregation and abandonment in this and other regions of the world. 相似文献
30.
Robert Hassink 《European Planning Studies》1996,4(2):167-184
Many regions in Western Europe have set up technology transfer agencies in order to support endogenous potential by encouraging the diffusion of new technologies from universities and large firms to small and medium‐sized enterprises (SMEs). However, many studies have shown that business partners such as customers and suppliers are the most important partners for the stimulation of the innovativeness of SMEs. Universities and transfer agencies are given a very low rank in these studies. These results have led to doubts about the usefulness of these institutions for regional economic development. In order to increase transparency, streamlining of the agencies involved is necessary so that there are fewer actors and more cooperation between them. To be able to reach technology‐following SMEs, at least one transfer organization in every region should employ senior engineers with extensive business experience to visit firms frequently (proactive) to help them come up with some technological issues (demand‐oriented). These agencies need long‐term financial backing so as to provide free advice to technology‐following SMEs. 相似文献