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   554篇
  免费   61篇
  2024年   4篇
  2023年   27篇
  2022年   19篇
  2021年   13篇
  2020年   25篇
  2019年   21篇
  2018年   25篇
  2017年   35篇
  2016年   35篇
  2015年   30篇
  2014年   18篇
  2013年   118篇
  2012年   27篇
  2011年   37篇
  2010年   23篇
  2009年   37篇
  2008年   18篇
  2007年   15篇
  2006年   19篇
  2005年   15篇
  2004年   7篇
  2003年   4篇
  2002年   12篇
  2001年   12篇
  2000年   5篇
  1999年   4篇
  1998年   4篇
  1997年   3篇
  1984年   1篇
  1983年   2篇
排序方式: 共有615条查询结果,搜索用时 15 毫秒
1.
In the Andes, there are several pre-Hispanic irrigation networks with structures destined for water storage. However, it has not been widely discussed in archaeological research. This is probably due to their being difficult to identify. The aim of this study is to explore the use of diatom assemblage analysis as a methodological tool suitable to help in the identification and characterization of these ancient hydraulic structures. We analyzed two archaeological structures interpreted as water reservoirs from north-western Argentina (EH1 in Antofagasta de la Sierra and U-88R1 in Yocavil) and compared them to current reservoirs. The diatom species composition and the changes in the dominant ecological groups in the studied structures highlight different periods of hydraulic behavior. EH1 contained and stored water, but there were periods of time in which there was a lack of use or abandonment of the structure. However, the U88-R1 structure does not have diatom evidence of containing standing water for a prolonged time but presence of wet soils. Thus, the structure could have been used for other water management strategies. The results show that diatom analysis is a methodological tool with a high potential to study ancestral hydrotechnologies.  相似文献   
2.
The aim of this investigation was to analyze the materials and techniques of the paintings in the 16th-century ce St Mary's Church, to evaluate deterioration of the paintings, and to propose a suitable conservation treatment for their preservation. The material analysis of ground, pigments, binders, and plasters was undertaken using binocular microscopy, field emission scanning electron microscopy (SEM)–energy dispersive X-ray spectroscopy, X-ray fluorescence, Fourier transform infrared spectroscopy in reflectance (KBr) and transmittance mode (attenuated total reflection), thin-film X-ray diffraction, and micro-Raman spectroscopy. Gas chromatography–mass spectrometry (GC-MS) was used for identifying proteinaceous and lipidic materials extracted from the micro-samples. The study generated data on two different red and green pigments used as decorative materials. The red pigments were identified as cinnabar along with traces of hematite and clay minerals, and green as malachite and the minor presence of other minerals. SEM analysis identified cotton fiber embedded in the coarse plaster layer that provided better strength to the plaster. Plant oils and proteins found as the binder in the pigment samples suggested that the painting technique was executed as tempera. Lead white and gypsum materials were used in previous restoration works.  相似文献   
3.
Zali Fung  Vanessa Lamb 《对极》2023,55(6):1662-1685
We engage geography's longstanding debate on what “counts” as resistance by introducing slow resistance to account for temporal-political strategies against unjust developments, particularly under authoritarian conditions. We draw on over a decade of fieldwork in the Salween River Basin where dams and diversions have been proposed since 1979, including the most recent iteration, the Yuam River water diversion project in Northwest Thailand. We find that resistance by impacted communities and civil society encompasses slow, strategic, and considered actions over time and generations. Such resistance is necessarily protracted to contest developments (re)proposed over decades. By foregrounding the strategic use of time and temporality, we highlight often overlooked actions and strategies of resistance by a diverse range of actors, showing how resistance movements are incremental and interconnected over time, even when “under the radar”. These strategies are key to contesting and (re)shaping the conditions of development in the Basin.  相似文献   
4.
Julia Sizek 《对极》2023,55(6):1898-1918
A proposed project will take water from an aquifer in the California desert to the coast. Lacking final approvals more than 30 years after it started, the project remains a plan despite sizeable opposition. What is its secret? In this paper, I examine the imaginaries of the underground aquifer underneath the lands of Cadiz Inc, the project proponent. While local theories insist the company is at the centre of a Chinatown conspiracy, I argue that the company stays alive through regulatory alchemy, a term that reveals the magic at the heart of scientific and regulatory approval processes. I examine narratives of the aquifer in environmental compliance and financial reporting in order to reveal how regulatory processes become the conditions of profit-making, building on debates in critical legal geography and political ecology.  相似文献   
5.
Much practically orientated environmental research is marked by a polarity between functionalist abstraction and ahistorical normative discourse. This paper seeks to bridge the divide between theoretical and empirical research through a case study of New York City's water supply. Current processes of socio-economic restructuring are leading to negative environmental consequences obscured by a failure to extend analysis beyond limited temporal, spatial or sectoral scales. Insights from regulationist theory show that a combination of fiscal, political and other developments are bringing about a wide-ranging reformulation of existing patterns of environmental regulation and service provision in the city. The power of the state is being radically diminished in relation to the power of capital and a plethora of different interest groups. A relatively simple centralized model of environmental regulation is being transformed into a complex decentralized pattern involving the emergence of new approaches to urban governance. Further research is needed on the contradictions between capitalist accumulation and environmental regulation at different spatial scales in order to link New York's changing role within the global economy to the declining political legitimacy and fiscal capability of the state to play an extensive role in environmental management.  相似文献   
6.
Recent studies have shown that pre-Columbian societies in the Amazon undertook significant landscape modifications, including earthworks. Our fieldwork has revealed that pre-Columbian settlements in the Santarém Region, Lower Amazon, were not limited to the vicinities of permanent water courses, as formerly often assumed. Instead, numerous archaeological sites, dating from ca. a.d. 1300 up to the time of European colonization in the seventeenth century, have been found in an upland area known as the Belterra Plateau, south of the present-day city of Santarém. These upland sites have been found to be associated with particular features in the landscape: cavities or depressions, known locally as “Poços de Água”. LiDAR data shows that a pattern of non-randomly distributed depressions extends far into the densely forested Tapajós National Forest (Flona-Tapajós), allowing us to suggest that the expansion of inland settlement extended considerably farther to the south than what has previously been established through conventional archaeological fieldwork.  相似文献   
7.
A shipwreck from the early 3rd century BC was discovered in the Black Sea's suboxic depths off Ere?li, Turkey, during the 2011 E/V Nautilus expedition. Remote investigation revealed the trawl‐damaged remains of a merchant ship carrying multiple amphora types associated with Aegean and Pontic production areas. Also discovered were elements of the ship's hull that show evidence of both pegged mortise‐and‐tenon and laced construction. The wreck provides crucial archaeological evidence for both maritime connectivity and ship‐construction methods during a period of political and economic transition.  相似文献   
8.
北京大学入藏的秦代水陆里程简册中记载秦代有"阳"县存在,关于这一新出现的秦县,前辈学者认为可能是位于今河南省方城县的秦汉"阳城"。然而,从简册中记载的"阳"县下属各乡到其他地区的距离来看,"阳县"不太可能在今方城附近,而更有可能是位于先秦"唐"国故地的"唐"县。其他出土材料所见的"唐"县一般写作"阳",清华简《系年》中还有楚国曾灭"唐(阳)"置县的明确记载。秦代的阳县应该就是继承了楚灭唐国之后所设的阳县。  相似文献   
9.
This article examines the impact of decentralization reforms on improving access to domestic water supply in the rural districts of Kondoa and Kongwa, Tanzania, using a users' and a gender perspective. The article addresses the question whether and to what extent the delivery of gender-sensitive water services to rural households improved after the reforms. Household- and village-level data were obtained through a household survey and qualitative methods. The findings show an increase of the proportion of households using improved sources of domestic water between 2002 and 2011. However, more than half of users still travel over a kilometre and use more than an hour to collect water in the dry season. Despite the increased proportion of women in water management committees, the outcomes of these decentralized arrangements differ for men and women. Overall, the reforms have produced contradictory effects by improving access to water supply for some users, and creating or reinforcing existing inter- and intra-village inequalities.  相似文献   
10.
I. Stober  K. Bucher 《Geofluids》2015,15(3):464-482
Hydraulic and hydrochemical data from several hundred wells mostly drilled by the oil and gas industry within the four deep carbonate and siliciclastic reservoirs of the Upper Rhine Graben area in France and Germany have been compiled, examined, validated and analysed with the aim to characterize fluids and reservoir properties. Due to enhanced temperatures in the subsurface of the Upper Rhine Graben, this study on hydraulic and hydrochemical properties has been motivated by an increasing interest in deep hydrogeothermal energy projects in the Rhine rift valley. The four examined geothermal reservoir formations are characterized by high hydraulic conductivity reflecting the active tectonic setting of the rift valley and its fractured and karstified reservoirs. The hydraulic conductivity decreases only marginally with depth in each of the reservoirs, because the Upper Rhine Graben is a young tectonically active structure. The generally high hydraulic conductivity of the reservoir rocks permits cross‐formation advective flow of thermal water. Water composition data reflect the origin and hydrochemical evolution of deep water. Shallow water to 500 m depth is, in general, weakly mineralized. The chemical signature of the water is controlled by fluid–rock geochemical interactions. With increasing depth, the total of dissolved solids (TDS) increases. In all reservoirs, the fluids evolve to a NaCl‐dominated brine. The high salinity of the reservoirs is partly derived from dissolution of halite in evaporitic Triassic and Cenozoic formations, and partly from the fluids residing in the crystalline basement. Water of all four reservoirs is saturated with respect to calcite and other minerals including quartz and barite.  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