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151.
BOOK REVIEWS     
Book Reviewed in this article: Portable Utopia: Glasgow and the United States 1820–1920. Bernard Aspinwall. Studies in Russian Historical Geography. James H. Bater and R. A. French, eds. Water and Sanitation: Economic and Sociological Perspectives. Peter G. Bourne, ed. Green Politics. Fritjof Capra and Charlene Spretnak. The Southern Cone: Realities of the Authoritarian State. César N. Caviedes. Women in Third World Development. Sue Ellen Charlton. Land Management: New Directions. David Chiddick and Alan Millington, eds. Geography and Ethnic Pluralism. Colin Clarke, David Ley, Ceri Peach, eds. Geomorphological Hazards in Los Angeles. R. U. Cooke. Regional Impacts of United States-Mexico Economic Relations. Alfonso Corona and Lay James Gibson. eds. Patterns of Jobs and Geographic Mobility. Torvald Gerger. Cities and Sickness: Health Care in Urban America. Ann Lennarson Greer and Scott Greer, eds. Neighborhoods: Their Place in Urban Life. Howard W. Hallman. Development and the Rural-Urban Divide. John Harriss and Mick Moore, eds. Patterns of Undocumented Migration: Mexico and the United States. Richard C. Jones, ed. Central Place Theory. Leslie J. King. The Geography of Western Europe: A Socio-economic Survey. Paul L. Knox. Regions and Resources: Strategies for Development. David T. Krisge, Daniel A. Seiver, Oliver S. Goldsmith and Michael J. Scott. Geography of Crowding and Human Response. A Study of Ahmedabad City. K. M. Kulkarni. Haciendo Pueblo. The Development of a Guadalajaran Suburb. Kathleen Logan. The Imperial Lion: Human Dimensions of Wildlife Management in Central Africa. Stewart A. Marks. Water in the Hispanic Southwest: A Social and Legal History, 1550–1850. Michael C. Meyer. Imlil: A Moroccan Mountain Community in Change. James A. Miller. Tourism in Canada: Selected Issues and Options. Peter E. Murphy, ed. David Harvey's Geography. John L. Paterson. Raster Scanning, Processing and Plotting of Cartographic Documents. Donna J. Peuquet and A. Raymond Boyle. The USSR and the Muslim World: Issues in Domestic and Foreign Policy. Yaacov Ro'i, ed. Environmental Perception and Behavior: An Inventory and Prospect. Thomas F. Saarinen, David Seamon, and James L. Sell. Incised channels, Morphology, Dynamics, and Control. Stanley A. Schumm, Michael D. Harvey, and Chester C. Watson. The Gap Between Rich and Poor: Contending Perspectives on the Political Economy of Development. Mitchell A. Seligson, ed. Twentieth-Century Richmond. Planning, Politics and Race. Christopher Silver. Land Conservation and Development: Examples of Land-Use Planning Projects and Programs. F. R. Steiner and H. N. van Lier, eds. Biogeography: Recent Advances and Future Directions. J. A. Taylor, ed. Late Quaternary Environments of the Soviet Union. A. A. Velichko, ed. H. E. Wright, Jr. and C. W. Barnosky, eds.  相似文献   
152.
Many arctic terrestrial ecosystems suffer from a permanent deficiency of nutrients. Marine birds that forage at sea and breed on land can transport organic matter from the sea to land, and thus help to initiate and sustain terrestrial ecosystems. This organic matter initiates the emergence of local tundra communities, increasing primary and secondary production and species diversity. Climate change will influence ocean circulation and the hydrologic regime, which will consequently lead to a restructuring of zooplankton communities between cold arctic waters, with a dominance of large zooplankton species, and Atlantic waters in which small species predominate. The dominance of large zooplankton favours plankton-eating seabirds, such as the little auk (Alle alle), while the presence of small zooplankton redirects the food chain to plankton-eating fish, up through to fish-eating birds (e.g., guillemots Uria sp.). Thus, in regions where the two water masses compete for dominance, such as in the Barents Sea, plankton-eating birds should dominate the avifauna in cold periods and recess in warmer periods, when fish-eaters should prevail. Therefore under future anthropogenic climate scenarios, there could be serious consequences for the structure and functioning of the terrestrial part of arctic ecosystems, due in part to changes in the arctic marine avifauna. Large colonies of plankton-eating little auks are located on mild mountain slopes, usually a few kilometres from the shore, whereas colonies of fish-eating guillemots are situated on rocky cliffs at the coast. The impact of guillemots on the terrestrial ecosystems is therefore much smaller than for little auks because of the rapid washing-out to sea of the guano deposited on the seabird cliffs. These characteristics of seabird nesting sites dramatically limit the range of occurrence of ornithogenic soils, and the accompanying flora and fauna, to locations where talus-breeding species occur. As a result of climate warming favoring the increase of ichthyiofagous cliff-nesting seabirds, we can expect that large areas of ornithogenic tundra around the colonies of plankton-eating seabirds situated far from the sea may disappear, while areas of tundra in the vicinity of cliffs inhabited by fish-eating seabirds, with low total production and supporting few large herbivores, will likely increase, but only imperceptibly. This may lead to habitat fragmentation with negative consequences for populations of tundra-dependent birds and mammals, and the possibility of a substantial decrease in biodiversity of tundra plant and animal communities.  相似文献   
153.
This note provides a brief review of five analytical methods previously used or promoted for diagnosing regime shifts in marine ecosystems. The methods discussed are: (i) principal components analysis, (ii) compositing average standard deviates, (iii) autoregressive moving average and intervention analysis modeling, (iv) vector autoregressive process modeling, and (v) Fisher information. Assessments of the relative strengths and weaknesses for the different analytical approaches are also offered. Some of these methods are applied to a collection of fishery oceanographic time series for the N. Pacific to illustrate aspects of their relative utility and limitations for diagnosing regime shift behavior. One recommendation for future studies is to analyze biotic and abiotic time series separately in order to identify ecosystem state variables of interest and to better isolate ecosystem behaviors from other influences like environmental change. Methods that allow for quantitative assessments of the statistical significance of hypothesized regime shifts should be favored over those that do not. Analyses of especially large collections of time series may benefit from first using a data compression technique and then applying one of the methods that are more appropriate for just one or a small number of time series. Because of the difficulties in observing and adequately documenting many aspects of marine ecosystem variability, it is crucial that future research attempt to combine empirical studies of large marine ecosystems with theoretical and modeling studies of other systems for which the dynamics and predictability are better understood. With such a comparative approach it should be possible to refine conceptual and simulation models, while also identifying crucial gaps in existing observations.  相似文献   
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155.
Realistic modelling of marine ecosystems is necessary for improving our understanding of the ocean’s biogeochemical state and for predicting their response to anthropic perturbations. An essential step in achieving this task is the use of mechanistic formulations to describe the biogeochemical processes involved in the dynamics of marine pelagic ecosystems. This study provides a review on some modelling strategies for some of the key processes involved in the dynamics of phytoplankton. It encompasses the most advanced work in terms of mechanistic understanding and, therefore, mainly deals with photosynthesis (including photoacclimation and photoinhibition), respiration, and nutrient uptake (including multi-limitation of algal growth by nutrients). We highlight, that in many ecosystem models, phytoplankton processes are still described more or less empirically, mainly due to a lack of biochemical knowledge, or if a mechanistic formulation exists, the parameters are often difficult to assess experimentally. As a result of this investigation, a preliminary structure for a generic phytoplankton model is delivered in the last section of this paper. This model includes a mechanistic representation of photosynthesis/photoinhibition based on photosystem II status, as well as new formulations for photoacclimation and dissolved organic matter exudation processes. The model sensitivity analysis with regard to its parameters and a comparison with chemostat experimental data are presented in a companion paper [Baklouti, M., Faure, V., Pawlowski, L., Sciandra, A., 2006. Investigation and sensitivity analysis of a mechanistic phytoplankton model implemented in a new modular numerical tool (Eco3M) dedicated to biogeochemical modelling. Progress in Oceanography]. Finally, this new class of multi-element, multi-species phytoplankton models will provide the basis for future studies on ecosystem modelling.  相似文献   
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158.
叶金聪 《台湾海峡》2005,24(4):553-557
本文系斜带髭鲷鱼苗室外水泥池不同生态系的育苗试验.在育苗前的“养水”期 间,1号池接入小球藻、微绿球藻、扁藻、金藻、轮虫、桡足类、枝角类等生物饵料;2号 池仅接入小球藻、轮虫生物饵料.在水温19.1~23℃、比重1.019、pH值8.5的条件 下.2池鱼苗经100d的培育后,平均全长各为31mm和29mm,平均体重各为0.90g 和0.75g,成活率18.5%和10.1%.试验表明:在育苗前期,生物饵料的多样性有利于 开口仔鱼的摄食和营养,也利于鱼苗的生长发育和成活率的提高.  相似文献   
159.
Net primary production (NPP) is a crucial feature of ecosystem function and structure. Furthermore, precipitation use efficiency (PUE) is a critical indicator for exploring NPP in grassland ecosystem responses to variations in precipitation and temperature. In this study, we examined the spatial patterns of NPP and PUE in China’s grasslands from 2000 to 2010 and explored the effects of environmental factors on NPP and PUE at different scales. The results showed first that the spatial distribution of NPP and PUE decreased from the northeast to southwest. NPP increased in most places across China’s grasslands; however, there was no obvious change in PUE during 2000–2010. Second, in most regions across China’s grasslands, positive and negative correlations existed between precipitation and NPP and PUE, respectively. The spatial distribution of the relationship between temperature and NPP and PUE was consistent with the relationship between precipitation with NPP and PUE. Finally, for the gradients of the various environmental factors in different regional grassland ecosystems, on the Tibetan Plateau, there were unimodal correlations between precipitation with NPP and PUE and aridity with NPP and PUE, but a positive linear correlation existed for temperature with NPP and PUE. However, in the Inner Mongolian Plateau, there were positive correlations between precipitation and NPP, temperature and NPP, and aridity and both NPP and PUE and negative correlations between precipitations and PUE and temperature and PUE. Our findings improve understanding of grassland ecosystem responses to global climate change and provide a basis for the protection of grassland ecosystems in arid and semi-arid regions.  相似文献   
160.
水生生态系统中的捕食与生物多样性   总被引:1,自引:0,他引:1  
捕食在水生生态系统中有重要的作用,是影响生物多样性的主要因素子之一。选择性的捕食中能使被喜食的猎物种类从水体中消失,使生物多样性降低。这种捕食也可能抑制优势种的发展,占免竞争排斥,提高猎生物多样性。  相似文献   
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