全文获取类型
收费全文 | 5177篇 |
免费 | 303篇 |
国内免费 | 284篇 |
专业分类
测绘学 | 911篇 |
大气科学 | 384篇 |
地球物理 | 304篇 |
地质学 | 605篇 |
海洋学 | 38篇 |
天文学 | 2篇 |
综合类 | 474篇 |
自然地理 | 3046篇 |
出版年
2024年 | 23篇 |
2023年 | 36篇 |
2022年 | 265篇 |
2021年 | 273篇 |
2020年 | 289篇 |
2019年 | 320篇 |
2018年 | 212篇 |
2017年 | 283篇 |
2016年 | 265篇 |
2015年 | 254篇 |
2014年 | 231篇 |
2013年 | 475篇 |
2012年 | 263篇 |
2011年 | 317篇 |
2010年 | 194篇 |
2009年 | 236篇 |
2008年 | 257篇 |
2007年 | 284篇 |
2006年 | 211篇 |
2005年 | 192篇 |
2004年 | 170篇 |
2003年 | 143篇 |
2002年 | 111篇 |
2001年 | 77篇 |
2000年 | 82篇 |
1999年 | 57篇 |
1998年 | 39篇 |
1997年 | 41篇 |
1996年 | 27篇 |
1995年 | 19篇 |
1994年 | 20篇 |
1993年 | 21篇 |
1992年 | 7篇 |
1991年 | 10篇 |
1990年 | 7篇 |
1989年 | 3篇 |
1988年 | 11篇 |
1987年 | 11篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 3篇 |
排序方式: 共有5764条查询结果,搜索用时 343 毫秒
821.
《The Professional geographer》2013,65(1):64-76
While inventive activity is necessary for industrial economies to progress, little is known about the types of enterprises inventing in Canada. The present study examines a typology of Canadian inventive enterprises at the national, subnational, and urban levels and the types of inventions developed in these areas from 1975 to 1989. Canadian patent and industrial directory information shows that Canada's largest enterprises are the most inventive, followed by small and then medium-sized enterprises. Although Canadian enterprises used teams of inventors to develop a considerably larger share of their inventions by 1989, they became discernably more inventive in only one industry after 1981 while concentrating on many process inventions between 1975 and 1989. Geographically, Canada's two largest cities and its core region were adversely affected by the declining inventiveness of this nation's large and foreign-owned enterprises during the 1980s. With respect to Canada's periphery, many of the characteristics typical of Canadian inventive enterprises were not readily apparent in this region, which had a more specialized inventive base than did the core. 相似文献
822.
《The Professional geographer》2013,65(2):243-255
Mutual funds are the primary investment vehicle for individual retirement savings, but the spatial aspects of mutual fund investments have not been examined. This paper discusses the characteristics of the mutual fund industry and compares them to other financial industries. Previous studies of the financial industry and quaternary location theory are used to formulate three hypotheses predicting the distribution of mutual fund assets: (1) mutual fund assets will concentrate in the largest urban centers; (2) mutual fund assets will become increasingly concentrated in financial centers over the 1986-1996 period; and (3) the distribution of mutual fund assets will be similar to the distribution of other financial activities. Examination of mutual fund asset data from 1986 and 1996 did not fully support any of the three hypotheses. These findings suggest that the standard elements of quaternary location theory may need to be reevaluated. 相似文献
823.
This paper analyses the recent developments in public space policy in the city of Hanoi, Vietnam. It has three aims. The first is to look at a potentially progressive urban policy in contrast to most work on ‘policies in motion’ that has primarily been concerned with neoliberal policies. The second is to put the process of public space policymaking in Hanoi in historical and cultural perspective. We therefore describe public space in Hanoi as historically constituted by different layers of meaning and physical urban patterns. The paper's third aim is to analyse the translocal connections involved in a policy that is still in the making, and therefore characterized by a series of ‘loose threads’. We show how different types of connections – policy mobility, topological relations and inter‐referencing – relate Hanoi to multiple locales elsewhere. The conclusion reflects on the ‘politics of reception’ showing how analysing a policy in the making develops a critical analysis of policies in motion. 相似文献
824.
825.
《The Professional geographer》2013,65(3):394-405
Collaborative urban governance has increased the role of community organizations in local decision-making processes. These organizations need financial resources in order to participate in urban governance. In this article, I examine the impact of foundation grants on the relationships and agendas of four community organizations in one neighborhood in St. Paul, Minnesota. Drawing on interviews, observations of organizations, and archival research, I demonstrate that in the 1990s, nonprofit foundations had a significant impact on the formation of new organizations and on their agendas in the neighborhood. Foundations are, therefore, an important player in urban governance, shaping a “neighborhood policy regime.” 相似文献
826.
827.
Abstract This paper explores the dynamics behind the changing regimes of urban renewal and its social impacts in Taiwan. Before the 1980s, the state was willing to solely shoulder the job of urban renewal with a wholly supportive financial budget and land appropriation law, while in the 1990s it became financially overburdened due to its renewal policy. Around the year 2000, the state turned towards promoting urban regeneration as a key business model. Through this historical exposition, the Taiwanese story of state transformation in urban renewal policy brings two issues to the fore. The first issue is the learning process concerning the policy of public-private partnership (PPP) initiatives. Trans-border policy mobility connects and constitutes cities, such as Taipei, with other places, such as London, through visits and seminars attended by policy makers and experts. However, policy transferred from abroad is “localized” in the learning process and used to prioritize the regeneration of public lands in the urban area. The PPP model is transformed in the face of domestic political struggles. The second issue is the social exclusion as a result of property-led regeneration. Rather than playing the role of an impartial institutional moderator, the state privileged landowners and developers and sacrificed the rights of tenants to stay put. By doing so, the state secures political support from landowner-cum-citizens and initiates a political culture of property in which local citizenship is predicated on ownership. 相似文献
828.
Abstract Creating resiliency, accomplished in part by individuals preparing for disaster, is the primary strategy outside of law enforcement for responding to the threat of urban terrorism. Individuals prepare when they perceive a need to do so, yet little is known about what shapes a person's awareness of vulnerability to terrorism. Because evidence indicates that social contacts act as conduits of information and affect perception of risk to natural hazards, it is possible that such contacts also affect terrorism vulnerability awareness. Because social contacts are also known to be systematically segmented by gender and location, we hypothesized that conversations about terrorism vary by gender and place, specifically the home and work place. Drawing on data from 93 interviews with householders in Boston, the study demonstrates that: (1) family networks generated discussions of home preparedness, whereas workplace networks engaged a wider variety of topics; (2) women discussed terrorism more frequently and in greater depth than did men; and (3) women heard more preparedness messages for the home than did men, whereas men undertook preparedness activities external to the home. The findings bridge geography and terrorism studies by theorizing emplaced and subjective human experiences that prompt conversations about terrorism. These conversations, in turn, help urban emergency managers and risk-hazards geographers promote rational dialogue and action vis-à-vis terrorism. Hazards researchers have shown that the more people discuss terrorism, the less they seek extreme and unwarranted responses. 相似文献
829.
Recent anti-systemic social movements have illustrated the central role of cities in social movement mobilization. We not only highlight the characteristics of urban social relations that make cities fertile ground for mobilization, but also point to the disjunctures between the geographies and spatialities of social relations in the city, and the geographies and spatialities of many systemic processes. Struggles for a more just society must consider the broad geographies and spatialities of oppression, which we illustrate with a brief analysis of the Occupy movement. Finally, we introduce the next five articles in this special issue, all illustrating the importance of the geographies and spatialities of urban social struggle. 相似文献
830.
In this article, we use local indicators of spatial association (LISA) and other spatial analysis techniques to analyze the distribution of centers with high employment density within metropolitan areas. We examine the 359 metropolitan areas across the United States at three points in time (1990, 2000, and 2010) to provide a spatio-temporal panoramic of urban spatial structure. Our analysis highlights three key findings. (1) The monocentric structure persists in a majority of metropolitan areas: 56.5% in 1990, 64.1% in 2000, and 57.7% in 2010. (2) The pattern of employment centers remains stable for most metropolitan areas: the number of centers remained the same for 74.9% of metropolitan areas between 1990 and 2000 and for 85.2% between 2000 and 2010. (3) Compared with monocentric metropolitan areas, polycentric metros are larger and more dense, with higher per-capita incomes and lower poverty rates. 相似文献