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261.
High-temperature mass spectrometric studies have been made to determine the distribution of volatiles within glassy rims of submarine pillow basalts dredged from the east rift zone of Kilauea volcano, Hawaii. The CO2/H2O mole ratio for glass-vapor inclusions within olivine phenocrysts in the glassy rims is greater than 30 : 1 compared to 0.06 for matrix glasses. Enclosing matrix glasses contain 0.53–0.74 wt.% H2O, 0.02–0.04 wt.% carbon, 0.08–0.12 wt.% sulfur, 0.012–0.028 wt.% chlorine and 0.012–0.077 wt.% fluorine.  相似文献   
262.
263.
An index of relative displacement risk to hurricanes   总被引:2,自引:2,他引:0  
Indicator and index-building activities have become commonplace for assessing and estimating social, environmental, and economic strengths and vulnerabilities of communities, regions and even countries. In the context of disasters, much of the empirical research has focused on identifying places and populations that are vulnerable to catastrophic hurricane and flood disasters. However, there have not been parallel efforts to capture measures for displacement risk. This article seeks to fill this gap by focusing on (1) a preliminary conceptualization of displacement risk; (2) a set of related indicators and measures at various scales, including indicators tapping policy capacity and commitment; and (3) development of an operational displacement risk index (DRI) and results for a snapshot year of 2007. The study area, 158 counties in the United States, was the coastal portion (an area two counties “deep”) of eight states. Findings suggest that the mean levels of DRI scores were much higher for coastal counties. Clusters of the highest DRI scores are particularly evident for coastal counties of Florida, especially the South Florida counties of Miami Dade, Monroe, Palm Beach, and Broward. Florida also scores high in terms of the top ten most vulnerable counties (i.e., 7 of the top 10) as well as exposure to hurricanes (i.e., 6 of the top 10 counties with the highest probability of hurricane strikes). Despite the limitations explained in the paper, we hope that the creation of the DRI has helped to fill a gap in knowledge and will lead to higher level theoretical and research discussions on the population displacement phenomenon, its determinants and planning and policy interventions.  相似文献   
264.
The Puelo River is a watershed shared between Chile and Argentina with a mean annual streamflow of 644 m3 s?1. It has a high ecologic and economic importance, including introduced farmed salmon, tourism, sports fishing and projected hydroelectricity. Using Austrocedrus chilensis and Pilgerodendron uviferum tree-ring records we reconstructed summer–fall (December–May) Puelo River streamflow, which is the first of such reconstructions developed in the Pacific domain of South America. The reconstruction goes back to 1599 and has an adjusted r 2 of 0.42. Spectral analysis of the reconstructed streamflow shows a dominant 84-year cycle which explains 25.1% of the total temporal variability. The Puelo River summer–fall streamflow shows a significant correlation (P?>?0.95, 1943–2002) with hydrological records throughout a vast geographic range within the Valdivian eco-region (35 to 46°S). Seasonal Puelo River interannual streamflow variability is related to large-scale oceanic and atmospheric circulation features. Summer–fall streamflows showed a significant negative correlation with the Antarctic Oscillation (AAO), whereas winter–spring anomalies appear to be positively connected with sea surface temperature variations in the tropical Pacific. In general, above- and below-average discharges in winter–spring are related to El Niño and La Niña events, respectively. The temporal patterns of the observed and reconstructed records of the Puelo River streamflow show a general decreasing trend in the 1943–1999 period. Projected circulation changes for the next decades in the Southern Hemisphere would decrease summer–fall Puelo River streamflows with significant impacts on salmon production, tourism and hydropower generation.  相似文献   
265.
A total of 22 species of zooplankton were identified from 8 sampling stations located in the limnetic zone of Pedu reservoir.The zooplankton community was dominated by rotifers (11 species),followed by cladocerans (9 species) and copepods (2 species).Four species of zooplankton comprised of 3 rotifers,Brachionus quadridentata,Brachionus caudatus and Keratella cochlearis and one cladoceran,Ceriodaphnia cornuta were present at all sampling stations.Species richness was highest at Station 2 (17 species) followed by Station 4 and Station 8 (14 species),Station 5 (15 species),Station 7 (11 species),Station 6 (10 species),Station 3 (9 species) and Station 1 (7 species).With an exception of water transparency,all other water quality parameters such as temperature,dissolved oxygen,conductivity,pH and total dissolved solids were not significant when compared between sampling stations.The study found that station 5 which was located in a calm strait,protected from strong wave and wind was a suitable area for zooplankton growth and establishment.Factors supporting the findings included highest water transparency (3.4 m),rich in species numbers (15 species),high diversity index (0.950) and evenness index (0.808).  相似文献   
266.
The relentless loss of biological diversity, which will have a direct impact on human society and degrade ecosystem buffers against the extremes of climate perturbation, requires a strong global governance response. Of the numerous international legal instruments relating to the protection of nature, the Convention on Biological Diversity (CBD) is the most comprehensive. This paper examines its current emphasis on global biodiversity targets to extend our understanding of its trajectory, and its evolving nature as an instrument of global governance. We review CBD documents, and early examinations of its emergent character, in the context of the distinction between hard and soft law approaches, and combine analysis on the issue of targets from the literature on development, climate change and conservation biology. We emphasise that the CBD, created as a hard law instrument with a framework character, had the clear facility to develop subsidiary hard law instruments in the form of protocols but has not significantly followed this route. We document how its approach - which has been typically ‘soft’, as exemplified by its focus on global biodiversity targets which are not backed up by obligations - suggests it operates de facto as policy rather than an instrument requiring state action. The adoption of global targets has parallels with other initiatives within global governance and may influence international political agendas, but they have failed to provide practical instruments for national implementation. Conditions may now exist for the CBD to develop focussed hard legal instruments in specific areas of its wide remit that support realistic targets.  相似文献   
267.
Fungal disease epidemics have the potential to bring about drastic innovations. However, in the case of the Black Sigatoka (Mycosphaerella fijiensis) fungus in bananas, producers and international traders are still awaiting a breakthrough in crop protection research. Using the cases of Brazil and Colombia, this paper examines different agricultural research responses to the disease. Brazil opted to replace susceptible varieties with resistant ones, whereas in Colombia chemical control by private actors dominated. We argue that these different responses result from at least three interrelated factors. First, producer type—smallholder farmers or larger export‐oriented plantations—influences the setting of crop protection research priorities. Second, a central, state‐led role versus a private sector response influences the size and time perspective of research activities. Third, domestic markets with multiple crop varieties versus Cavendish‐only export markets leads to differences in control practices and research responses. From this case study, we argue that the currently proposed innovation systems approaches in international agricultural research should adopt a broader perspective that assesses how research is interwoven with agrarian dynamics, commodity chains and particular state roles to elucidate how state–producer–researcher networks perform disease control and where and how to find new solutions.  相似文献   
268.
Climate change is inevitably altering the hydrological regime of water bodies. The interest in changing behaviour of intermittent rivers is increasing in many countries. This research was focused on intermittent rivers (rivers which naturally, periodically cease to flow) in Lithuania. The purpose of this research was to provide an overview of flow intermittency phenomena according to available data in a historical period and to evaluate the impact of catchment geographical features and climate variability on zero-flow events. The calculated indices of flow intermittency showed that the selected rivers had very different flow regimes. The threshold for the separation of typically intermittent rivers from only occasionally intermittent ones was suggested. Multiple linear regression analysis defined the crucial role of catchment size and watercourse slope on the river cessation process in Lithuania. The applied non-parametric Wilcoxon–Mann–Whitney test revealed the significance of the relationship between precipitation (in June–September) and zero-flow duration. Flow intermittency phenomena in Lithuanian rivers were linked to a low-frequency teleconnection pattern (SCAND index). A methodology of estimating the relation between river intermittency and large-scale atmospheric circulation pattern (based on SCAND index) was created. The generated regression equations between flow intermittency indices and catchment characteristics might be useful for the estimation of zero-flows in ungauged river catchments. The main aspect of future investigations might be related to forecasting flow intermittency using modern hydrological models and climate scenarios as well as the defined relationships between zero-flow indices and physico-geographical features of river catchments.  相似文献   
269.
The results from the simultaneous observations in B and R colours of AM Her are presented. Analysis of these data shows the following: (a) There are always two clear minima in the R light curves, while the secondary minimum in B light curves sometimes is not well defined; (b) The times of the minima in R and B colour nearly coincide; (c) The photometric period changes remarkably from cycle to cycle but its mean value remains constant; (d) Short stillstands on the increasing branches of the two minima are seen similar to those visible in UX UMa-type cataclysmic stars; (e) Besides the irregular flickering with time scale of a few minutes, a variability with a period 20.28 min in the two colours is established.  相似文献   
270.
Non-glaciated Arctic lowlands in north-east Siberia were subjected to extensive landscape and environmental changes during the Late Quaternary. Coastal cliffs along the Arctic shelf seas expose terrestrial archives containing numerous palaeoenvironmental indicators (e.g., pollen, plant macro-fossils and mammal fossils) preserved in the permafrost. The presented sedimentological (grain size, magnetic susceptibility and biogeochemical parameters), cryolithological, geochronological (radiocarbon, accelerator mass spectrometry and infrared-stimulated luminescence), heavy mineral and palaeoecological records from Cape Mamontov Klyk record the environmental dynamics of an Arctic shelf lowland east of the Taymyr Peninsula, and thus, near the eastern edge of the Eurasian ice sheet, over the last 60 Ky. This region is also considered to be the westernmost part of Beringia, the non-glaciated landmass that lay between the Eurasian and the Laurentian ice caps during the Late Pleistocene. Several units and subunits of sand deposits, peat–sand alternations, ice-rich palaeocryosol sequences (Ice Complex) and peaty fillings of thermokarst depressions and valleys were presented. The recorded proxy data sets reflect cold stadial climate conditions between 60 and 50 Kya, moderate inderstadial conditions between 50 and 25 Kya and cold stadial conditions from 25 to 15 Kya. The Late Pleistocene to Holocene transition, including the Allerød warm period, the early to middle Holocene thermal optimum and the late Holocene cooling, are also recorded. Three phases of landscape dynamic (fluvial/alluvial, irregular slope run-off and thermokarst) were presented in a schematic model, and were subsequently correlated with the supraregional environmental history between the Early Weichselian and the Holocene.  相似文献   
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