全文获取类型
收费全文 | 2135篇 |
免费 | 376篇 |
国内免费 | 747篇 |
专业分类
测绘学 | 156篇 |
大气科学 | 364篇 |
地球物理 | 354篇 |
地质学 | 1538篇 |
海洋学 | 410篇 |
天文学 | 13篇 |
综合类 | 111篇 |
自然地理 | 312篇 |
出版年
2024年 | 15篇 |
2023年 | 40篇 |
2022年 | 103篇 |
2021年 | 90篇 |
2020年 | 122篇 |
2019年 | 137篇 |
2018年 | 101篇 |
2017年 | 131篇 |
2016年 | 103篇 |
2015年 | 99篇 |
2014年 | 123篇 |
2013年 | 136篇 |
2012年 | 153篇 |
2011年 | 117篇 |
2010年 | 102篇 |
2009年 | 143篇 |
2008年 | 155篇 |
2007年 | 147篇 |
2006年 | 148篇 |
2005年 | 114篇 |
2004年 | 127篇 |
2003年 | 102篇 |
2002年 | 102篇 |
2001年 | 80篇 |
2000年 | 75篇 |
1999年 | 54篇 |
1998年 | 75篇 |
1997年 | 66篇 |
1996年 | 46篇 |
1995年 | 44篇 |
1994年 | 36篇 |
1993年 | 40篇 |
1992年 | 21篇 |
1991年 | 30篇 |
1990年 | 18篇 |
1989年 | 17篇 |
1988年 | 20篇 |
1987年 | 13篇 |
1986年 | 8篇 |
1985年 | 3篇 |
1983年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有3258条查询结果,搜索用时 15 毫秒
991.
An assessment of Indo-Pacific oceanic channel dynamics in the FGOALS-g2 coupled climate system model 总被引:2,自引:0,他引:2
Lag correlations of sea surface temperature anomalies (SSTAs), sea surface height anomalies (SSHAs), subsurface temperature anomalies, and surface zonal wind anomalies (SZWAs) produced by the Flexible Global Ocean-Atmosphere-Land System model: Grid-point Version 2 (FGOALS-g2) are analyzed and compared with observations. The insignificant, albeit positive, lag correlations between the SSTAs in the southeastern tropical Indian Ocean (STIO) in fall and the SSTAs in the central-eastern Pacific cold tongue in the following summer through fall are found to be not in agreement with the observational analysis. The model, however, does reproduce the significant lag correlations between the SSHAs in the STIO in fall and those in the cold tongue at the one-year time lag in the observations. These, along with the significant lag correlations between the SSTAs in the STIO in fall and the subsurface temperature anomalies in the equatorial Pacific vertical section in the following year, suggest that the Indonesian Throughflow plays an important role in propagating the Indian Ocean anomalies into the equatorial Pacific Ocean. Analyses of the interannual anomalies of the Indonesian Throughflow transport suggest that the FGOALS-g2 climate system simulates, but underestimates, the oceanic channel dynamics between the Indian and Pacific Oceans. FGOALS-g2 is shown to produce lag correlations between the SZWAs over the western equatorial Pacific in fall and the cold tongue SSTAs at the one-year time lag that are too strong to be realistic in comparison with observations. The analyses suggest that the atmospheric bridge over the Indo-Pacific Ocean is overestimated in the FGOALS-g2 coupled climate model. 相似文献
992.
993.
This paper analyzes the Urban Heat Island (UHI) effect in Lhasa City of Tibet using meteorological observations, the Normalized Difference Vegetation Index (NDVI), Land Surface Temperature (LST) data obtained from Earth Observing System/Moderate resolution Imaging Spectroradiometer (EOS/MODIS) information, and correlation and composite analyses. The results show: (1) Areas with high temperature are primarily located in the center of the city or nearby counties, while low temperature areas are in the suburbs of counties. The area with high temperature has expanded in recent years and some high-temperature centers have even migrated to certain other regions. (2) The UHI intensity tends to be stronger both in annual and seasonal variations, especially in winter. Also, LST is somewhat positively related to mean air temperature. (3) A negative correlation exists between the changes of LST and NDVI with the increase of vegetation from urban to rural areas in different seasons. (4) The UHI intensity is negatively correlated with precipitation while positively correlated with wind speed, and the relation between the UHI intensity and evaporation varies with the seasons, namely, the intensity is positively correlated with summer evaporation but negatively correlated with winter evaporation. (5) UHI intensity might be enhanced by intensified urbanization, wherein built-up areas expand, there is increased heat from human activity, and there is more artificial heat input to the atmosphere. 相似文献
994.
995.
996.
A three-dimensional fog model,suitable for precipitous and complex terrain,is designed contain-ing four prognostic variables—wind speed,potential temperature,specific humidity and mixing ratioof liquid water.The model considers turbulent exchange,the long-wave radiation on the ground sur-face and in the air.the short-wave solar radiation,the evaporation and condensation of moisture andthe surface heat budget and so on.In order to make the model run steadily on precipitous and complexterrain,we have improved the method of calculating horizontal pressure gradient force in the terraincoordinate system.The results coincide on the whole with the actual situation. 相似文献
997.
本文通过成都城市发展前后气候要素变化的对比分析,探索了城市化对成都市气候影响的基本规律,并用统计方法得出了城市“热岛”强度(△T,△Tmin)与城市人口总户数及建成区面积密切相关的客观事实,为改善和治理成都城市气候提供了一定的依据。 相似文献
998.
Climate and tectonics are two interactive factors in the earth's system. They are controlled by astronomical cycles. It has been unheeded for a long time that large-scale material motion caused by global climatic change is one of the powers for tectonic movement. Tectonic movement makes the distributional pattern of continent and ocean change and makes global climate type change strongly in large scale. It is a good example that the change of the sea-ice around Antarctic Continent and in the Drake Passage has the switch process for global climatic changes. Tide makes the oceanic crust of the East Pacific Ocean and the West Pacific Ocean rise or fall 60 cm oppositely. Before and after El Nino events,the oceanic level of the East Pacific Ocean and the West Pacific Ocean may rise or fall 40 cm oppositely. Because of isostasy, oceanic crust may fall or rise 13 or 20 cm. They are the reasons why El Nino events are interrelated with the earthquakes and volcanoes. This is so called seesaw phenomenon of oceanic crust. 相似文献
999.
《The Professional geographer》1987,39(3):363-386
Book Reviewed in this article: Hillslope Processes. Binghamton Symposia in Geomorphology International Series: 16. Athol D. Abrahams , ed. The Atlas of Central America and the Caribbean. The Diagram Group . The Cultural Atlas of Islam. Isma'il R. al Faruqi and Lois Lamaya'al Faruqi . Atlas of Israel Contemporary Africa: Development, Culture and the State. Morag Bell . Fundamentals of Physical Geography. David Briggs and Peter Smithson . The Bicentennial Census: New Directions for Methodology in 1990. Constance F. Citro and Michael L. Cohen , eds . World Patterns of Modern Urban Change: Essays in Honor of Chauncy D. Harris. Michael P. Conzen , ed . New Directions for Agriculture and Agricultural Research: Neglected Dimensions and Emerging Alternatives. Kenneth A. Dahlberg , ed . Water Resources Atlas of Florida. E.A. Fernald and D.J. Patton , eds . Landscape Ecology. R.T.T. Forman and M. Godron . The Myth of the North American City: Continentalism Challenged. Michael Goldberg and John Mercer . The Permafrost Environment. Stuart A. Harris . Climate and Circulation of the Tropics. Stefan Hastenrath . The Island of South Georgia. Robert Headland . The Making of Urban Europe, 1000-1950. Paul M. Hohenberg and Lynn Hollen Lees . Bombay in Transition: The Growth and Social Ecology of a Colonial City, 1889–1980. Meera Kosambi . Plant Closings; Public or Private Choices? Richard B. McKenzie , ed . Malaysia: Tradition, Modernity and Islam. R.S. Milne and Diane K. Mauzy . Technology on the Frontier: Mining in Old Ontario. Dianne Newell . The Maritime Political Boundaries of the World. J.R.V. Prescott . Tall Office Buildings in the United States. James W. Pygman and Richard Kateley (Real Estate Research Corporation). Technology, Regions, and Policy. John Rees , ed . The United States and the Regional Organization of Asia and the Pacific: 1965-1985. W.W. Rostow . Renewable Energy: Progress, Prospects. Stephen W. Sawyer Wisconsin Foundations. Gwen Schultz . Dwelling, Place and Environment: Towards a Phenomenology of Person and World. David Seamon and Robert Mugerauer , eds . Power and Place: Canadian Urban Development in the North American Context. Gilbert A. Stelter and Alan F.J. Artibise , eds . Small Firms in Regional Economic Development: Britain, Ireland and the United States. D. J. Storey , ed . Mathematical Methods in Human Geography and Planning. A. G. Wilson and R. J. Bennett . El Niño North: Niño Effects on the Eastern Subarctic Pacific Ocean. W. S. Wooster and D. L. Fluharty , eds . The Soviet Iron and Steel Industry. Craig ZumBrunnen and Jeffrey Osleeb . 相似文献
1000.
本文提出一组εNd-La/Nb、εNd-Ba/Nb和εNd-Nb/Th图。在这些图中岛弧火山岩呈三角形分布,从而将其源区的三个主要端元(MORB型亏损地幔、俯冲洋壳析出流体、陆源沉积物)同时显示在一张图上。据此,岛弧火山岩可根据其源区特征划分成两类:二端元型(无陆源沉积物)和三端元型。此外,EMII型幔源岩石在这些图中也被分成两类:与岛弧火山岩类似的,具有高La/Nb、Ba/Nb和低Nb/Th的大陆溢流玄武岩和某些橄榄岩包体;具有低La/Nb、Ba/Nb和高Nb/Th的萨莫德型海岛玄武岩。它们对应的EMII富集地幔端元也可分为两种:EMIIM,由俯冲洋壳析出流体交代楔型地幔而成;EMIISR,与陆源沉积物再循环进入对流上地幔有关。 相似文献