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201.
Brent Taylor  Rob C. de Loë 《Geoforum》2012,43(6):1207-1217
A major challenge to integrating local knowledge into collaborative environmental governance processes stems from the underlying differences between positivist science and local knowledge; these differences often result in strong differences of opinion regarding which forms of knowledge are valid in environmental decision-making. Previous research on these issues has mainly focused on the attitudes of scientists towards local knowledge. Studies of the views of local and non-scientific actors regarding their own knowledge are much less common. Through a qualitative case study of water allocation planning in South Australia, we analyzed participants’ conceptualizations of local knowledge and the role of local knowledge in collaborative governance. We found that participants defined local knowledge broadly across a number of dimensions and that many acknowledged variability in the nature and quality of different types of local knowledge. While most recognized the value of local knowledge in supporting technical investigations and developing policies, very few participants identified a role for local knowledge in the early stages of the collaborative process (i.e., in framing problems or establishing research protocols). Previous research has highlighted “epistemological anxiety” among scientists and resource managers toward local knowledge as a significant barrier to its effective use in environmental decision-making. This study suggests that state and local actors, and scientists and non-scientists, share similar reservations about local knowledge and highlights the need for researchers and practitioners to take into account the attitudes of all types of participants when considering how to overcome the epistemological challenges related to integrating local knowledge into collaborative management.  相似文献   
202.
Paleorecords from multiple indicators of environmental change provide evidence for the interactions between climate, human alteration of watersheds and lake ecosystem processes at Lake Tanganyika, Africa, a lake renowned for its extraordinary biodiversity, endemism and fisheries. This paper synthesizes geochronology, sedimentology, paleoecology, geochemistry and hydrology studies comparing the history of deltaic deposits from watersheds of various sizes and deforestation disturbance levels along the eastern coast of the lake in Tanzania and Burundi. Intersite differences are related to climate change, differences in the histories of forested vs. deforested watersheds, differences related to regional patterns of deforestation, and differences related to interactions of deforestation and climate effects. Climate change is linked to variations in sediment accumulation rates, charcoal accumulation, lake level and water chemistry, especially during the arid-humid fluctuations of the latter part of the Little Ice Age. Differences between forested and deforested watersheds are manifested by major increases in sediment accumulation rates in the latter (outside the range of climatically driven variability and for the last 40 years unprecedented in comparison with other records from the lake in the late Holocene), differences in eroded sediment and watershed stream composition, and compositional or diversity trends in lake faunal communities related to sediment inundation. Variability in regional patterns of deforestation is illustrated by the timing of transitions from numerous sedimentologic, paleoecologic and geochemical indicators. These data suggest that extensive watershed deforestation occurred as early as the late-18th to the early-19th centuries in the northern part of the Lake Tanganyika catchment, in the late-19th to early-20th centuries in the northern parts of modern-day Tanzania, and in the mid-20th century in central Tanzania. Rapid increases in sediment and charcoal accumulation rates, palynological and lake faunal changes occurred in the early-1960s. We interpret this to be the result of greatly enhanced flushing of sediments in previously deforested watersheds triggered by extraordinary rainfall in 1961/62. Regional differences in deforestation histories can be understood in light of the very different cultural and demographic histories of the northern and central parts of the lake shoreline. Incursion of slaving and ivory caravans from the Indian Ocean to the central coast of Lake Tanganyika by the early-19th century, with their attendant diseases, reduced human and elephant populations and therefore maintained forest cover in this region through the late-19th to early-20th centuries. In contrast, the northeastern portion of the lakeshore did not experience the effects of the caravan trades and consequently experienced high human population densities and widespread deforestation much earlier. These studies demonstrate the importance of paleolimnological data for making informed risk assessments of the potential effects of watershed deforestation on long-term lake ecosystem response in the Lake Tanganyika catchment. Differences in sediment yield and lake floor distribution of that yield, linked to factors such as watershed size, slope, and sediment retention, must be accounted for in management plans for both human occupation of currently forested watersheds and the development of future underwater reserves.  相似文献   
203.
We established sediment geochronologies for cores from eight deltaic areas in Lake Tanganyika (the Lubulungu, Kabesi, Halembe, Malagarasi, Nyasanga/Kahama, Mwamgongo, Nyamusenyi, and Karonge/Kirasa River deltas), recording a range of watershed disturbance histories from the eastern margin of this African rift valley lake. Cores from currently disturbed sites on the central Tanzanian coast display remarkably uniform and low rates of sediment accumulation from the 18th century until the early 1960s, when a synchronous and dramatic rise in rates occurs. Through this same time interval sedimentation rates offshore from undisturbed Tanzanian watersheds either remain unchanged or decline. Further north, at disturbed sites along the northern Tanzania and Burundi coasts, the pattern of sedimentation rate increase is more complex. Although a mid-late 20th century increase is also evident in these sites, indications of earlier periods of increasing sediment erosion, dating from the mid-late 19th century, are also evident. Synchronous changes in sediment accumulation rates dating from the early 1960s may be the result of exceptionally wet years triggering an increase in the discharge of previously eroded and unconsolidated alluvium and stream/beach terrace deposits, previously accumulated in the deltas and stream valleys of impacted watersheds. Sedimentation rate impacts of deforestation on lake ecosystems are likely modulated by short-term climatic forcing events, which can impact the specific timing and location of sediment discharge to lakes.  相似文献   
204.
This paper contributes to the ongoing debate on the concentration of social service facilities within North American cities. The location quotient and the coefficient of localization are applied to data on Adult Services, Children's Services and psychiatric group homes (residential care facilities) in Metropolitan Toronto. Results demonstrate a high degree of localization in all three categories, particularly the psychiatric, and could be used in the formulation of placement policies to relieve certain areas of the inner city of the social and economic pressures created by group home concentration.  相似文献   
205.
Synchrotron X-ray computed microtomography (CMT) was applied to five basalt samples from different locations in order to determine the microgeometrical structures and physical properties of vesicles. Two vesiculated basaltic lavas and one calcite-filled vesiculated basaltic lava were collected from the Lesotho Highland, South Africa, and two basaltic scoria tephra were taken from the Lungkuan Volcano Group in northeast China. They were examined with CMT on the X27C beam line of the Brookhaven National Synchrotron Light Source. The voxel size varied from 10 to 20 µm depending on the chosen field of view of the tomographic instrument. A fast-filtered back-transform (FFBT) algorithm was employed in the tomographic reconstruction. A 3D image geometry analysis package was used to measure the vesicularity, specific surface area and interconnectivity of the vesicles. The results of the analyses showed that the bubbles have roughly spheroidal forms of different sizes. Vesicularity ranged from 45% for lavas to 80% for scoria. At least 90% of the vesicles are interconnected. Specific surface area was determined both by counting voxel faces and by use of two-point correlation functions.  相似文献   
206.
207.
208.
The spatial variability of two fundamental morphological variables is investigated for rivers having a wide range of discharge (five orders of magnitude). The variables, water‐surface width and average depth, were measured at 58 to 888 equally spaced cross‐sections in channel links (river reaches between major tributaries). These measurements provide data to characterize the two‐dimensional structure of a channel link which is the fundamental unit of a channel network. The morphological variables have nearly log‐normal probability distributions. A general relation was determined which relates the means of the log‐transformed variables to the logarithm of discharge similar to previously published downstream hydraulic geometry relations. The spatial variability of the variables is described by two properties: (1) the coefficient of variation which was nearly constant (0·13–0·42) over a wide range of discharge; and (2) the integral length scale in the downstream direction which was approximately equal to one to two mean channel widths. The joint probability distribution of the morphological variables in the downstream direction was modelled as a first‐order, bivariate autoregressive process. This model accounted for up to 76 per cent of the total variance. The two‐dimensional morphological variables can be scaled such that the channel width–depth process is independent of discharge. The scaling properties will be valuable to modellers of both basin and channel dynamics. Published in 2002 John Wiley & Sons, Ltd.  相似文献   
209.
川东北地区构造-热演化探讨——来自(U-Th)/He年龄Ro的约束   总被引:1,自引:0,他引:1  
利用镜质组反射率和磷灰石与锆石的(U-Th)/He年龄一起模拟了川东北地区三叠纪以来的构造-热演化特征.结果表明早三叠世的热流值在51~66 mW/m2,自晚三叠世至白垩纪随盆地性质由前陆盆地演化为陆内坳陷盆地,热流缓慢降低直至现今的44.5 mW/m2.但在晚白垩世-古新世时期受燕山晚期构造运动的影响,热流有一个微弱增高的现象.同时,磷灰石和锆石的He年龄揭示了川东北地区大致在晚白垩世期间开始隆升且抬升剥蚀量较大.因此,磷灰石和锆石的(U-Th)/He年龄可以揭示后期详细的冷却历史.  相似文献   
210.
New KAr ages for a basalt flow interbedded with Tahoe and Tioga tills in Sawmill Canyon, southeastern Sierra Nevada, slightly refine previously published ages for the flow and provide an estimate of 53,000 ± 44,000 yr for the Tahoe-Tioga interglaciation.  相似文献   
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