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161.
The scale, structure and impacts of food systems in Ireland have changed dramatically over the last several hundred years, predominantly since the mechanisation and intensification of farming began in the late nineteenth century. The transformation of the potato production system, which for the preceding century had dominated the Irish diet, was particularly dramatic. The time from the introduction of the potato c. 1600 to its catastrophic decline in the mid-1800s, represented a period of Irish agriculture distinctly at odds with what came before and after, involving as it did complete dependence on a single crop system. Despite devastating crop losses suffered in the nineteenth century and particularly associated with the Great Famine, the potato remained agriculturally significant in Ireland. From the late 1800s onwards the system underwent a transition towards the highly mechanised, specialised, intensive and market-oriented agri-industrial food systems of today. This new high input-high output system was accompanied by an expansion in environmental impacts extending from local to global scales. This article addresses that transition in the role and impacts of the potato in Ireland, from its introduction to the present day.  相似文献   
162.
A survey of women AAG members in applied geography shows a geographical concentration in the Washington metropolitan area and an employment concentration in the private sector. The typical educational preparation is a master's degree. Job titles reflect the importance of planning, environmental issues, and cartography; cartography is cited as the most helpful career skill. Respondents want the AAG to promote geography and to help graduates in finding careers.  相似文献   
163.
The hydrologic effect of replacing pasture or other short crops with trees is reasonably well understood on a mean annual basis. The impact on flow regime, as described by the annual flow duration curve (FDC) is less certain. A method to assess the impact of plantation establishment on FDCs was developed. The starting point for the analyses was the assumption that rainfall and vegetation age are the principal drivers of evapotranspiration. A key objective was to remove the variability in the rainfall signal, leaving changes in streamflow solely attributable to the evapotranspiration of the plantation. A method was developed to (1) fit a model to the observed annual time series of FDC percentiles; i.e. 10th percentile for each year of record with annual rainfall and plantation age as parameters, (2) replace the annual rainfall variation with the long term mean to obtain climate adjusted FDCs, and (3) quantify changes in FDC percentiles as plantations age. Data from 10 catchments from Australia, South Africa and New Zealand were used. The model was able to represent flow variation for the majority of percentiles at eight of the 10 catchments, particularly for the 10–50th percentiles. The adjusted FDCs revealed variable patterns in flow reductions with two types of responses (groups) being identified. Group 1 catchments show a substantial increase in the number of zero flow days, with low flows being more affected than high flows. Group 2 catchments show a more uniform reduction in flows across all percentiles. The differences may be partly explained by storage characteristics. The modelled flow reductions were in accord with published results of paired catchment experiments. An additional analysis was performed to characterise the impact of afforestation on the number of zero flow days (Nzero) for the catchments in group 1. This model performed particularly well, and when adjusted for climate, indicated a significant increase in Nzero. The zero flow day method could be used to determine change in the occurrence of any given flow in response to afforestation. The methods used in this study proved satisfactory in removing the rainfall variability, and have added useful insight into the hydrologic impacts of plantation establishment. This approach provides a methodology for understanding catchment response to afforestation, where paired catchment data is not available.  相似文献   
164.
Al Huwaysah 010 is an ungrouped achondrite meteorite, recently referred to as a brachinite-like meteorite. This meteorite, showing a fine-grained assemblage of low-Ca pyroxene and opaque phases, is strongly reduced in comparison to other reduced brachinites. The occurrence of some tiny plates of graphite and oldhamite in this meteorite suggests that a partial melt residue has experienced a further reduction process. Olivine, the most abundant phase, is compositionally homogeneous (Fo83.3) as well as the clinopyroxene (En45.5Fs10.8Wo43.7) and the plagioclase (Ab69.5). Orthopyroxene (En85.4Fs13.9Wo0.7) also occurs but only in a fine intergrowth. Other accessory phases are Fe metal grains (Ni-free or Cr-bearing Fe-Ni alloy), troilite, chlorapatite, pentlandite (as inclusions in chromite). The sample shows two different closure temperatures: the highest (≈900°C) is determined via the olivine–chromite intercrystalline geothermometer and the lowest temperature (≈520°C) is determined via the pyroxene-based intracrystalline geothermometer. These temperatures may represent, respectively, the closure temperature associated with the formation and a subsequent impact event excavating the sample from the parental body. The visible to near-infrared (VNIR) reflectance spectra of Al Huwaysah 010 exhibit low reflectance, consistent with the presence of darkening components, and weak absorptions indicative of olivine and pyroxene. Comparing the spectral parameters of Al Huwaysah 010 to potential parent bodies characterized by olivine–pyroxene mineralogy, we find that it falls within the field previously attributed to the SIII type asteroids. These results lead us to classify the Al Huwaysah 010 meteorite as the most reduced brachinite, whose VNIR spectral features show strong affinities with those of SIII asteroids.  相似文献   
165.
Evaluation of the CORDEX-Africa multi-RCM hindcast: systematic model errors   总被引:4,自引:3,他引:1  
Monthly-mean precipitation, mean (TAVG), maximum (TMAX) and minimum (TMIN) surface air temperatures, and cloudiness from the CORDEX-Africa regional climate model (RCM) hindcast experiment are evaluated for model skill and systematic biases. All RCMs simulate basic climatological features of these variables reasonably, but systematic biases also occur across these models. All RCMs show higher fidelity in simulating precipitation for the west part of Africa than for the east part, and for the tropics than for northern Sahara. Interannual variation in the wet season rainfall is better simulated for the western Sahel than for the Ethiopian Highlands. RCM skill is higher for TAVG and TMAX than for TMIN, and regionally, for the subtropics than for the tropics. RCM skill in simulating cloudiness is generally lower than for precipitation or temperatures. For all variables, multi-model ensemble (ENS) generally outperforms individual models included in ENS. An overarching conclusion in this study is that some model biases vary systematically for regions, variables, and metrics, posing difficulties in defining a single representative index to measure model fidelity, especially for constructing ENS. This is an important concern in climate change impact assessment studies because most assessment models are run for specific regions/sectors with forcing data derived from model outputs. Thus, model evaluation and ENS construction must be performed separately for regions, variables, and metrics as required by specific analysis and/or assessments. Evaluations using multiple reference datasets reveal that cross-examination, quality control, and uncertainty estimates of reference data are crucial in model evaluations.  相似文献   
166.
Alice J. Hovorka 《Geoforum》2012,43(4):875-884
This paper is conceptually grounded in feminist–posthumanist intersectionality, offering an empirical case study that is geographic in scope, balances discursive and material elements, focuses on gender–species relations, and details dynamics of othering and privileging. It is empirically situated in a case study featuring women and chickens, men and cattle in the southern African nation of Botswana. It considers their symbolic associations with certain social realms, their spatial placements into and within particular locales, and the resulting context-specific dynamics that occur and shape their daily lives and interrelations with one another. Such socio-spatial practices are the means through which men, women, chickens and cattle become privileged and/or othered within dominant gender–species hierarchical arrangements. The paper also explores emerging urban and commercial agriculture spaces in contemporary Botswana, which empower women and chickens through increased access to land and productive activities, and increased visibility, status and value. Such empowerment remains bounded, however, given significant material, discursive and ethical implications of re-positioning within dominant structures.  相似文献   
167.
Reservoir sedimentation data and sediment yields from Taiwanese rivers show increased soil erosion in response to both 20th century changes in land use and a more recent increase in typhoon frequency and intensity. Decadal variations of up to 5- to 20-fold in suspended-sediment rating curves demonstrate supply-limited transport and correspond to increased sediment delivery from hillslopes due to changes in land use, regional ground shaking during the Chi-Chi earthquake, and post-2000 changes in typhoon frequency and intensity. While accelerated erosion in central Taiwan after the Chi-Chi earthquake has been documented previously, our results show that periods of increased upland erosion also occurred earlier, in response to 20th century changes in land use. Analyses of rainfall records and typhoon frequency for the period 1900–2009 further point to an island-wide increase in erosion rates corresponding to increased typhoon frequency and intensity after 1990.  相似文献   
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