全文获取类型
收费全文 | 632篇 |
免费 | 22篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 16篇 |
大气科学 | 44篇 |
地球物理 | 152篇 |
地质学 | 243篇 |
海洋学 | 64篇 |
天文学 | 62篇 |
综合类 | 2篇 |
自然地理 | 75篇 |
出版年
2023年 | 3篇 |
2021年 | 2篇 |
2020年 | 12篇 |
2019年 | 10篇 |
2018年 | 21篇 |
2017年 | 15篇 |
2016年 | 21篇 |
2015年 | 18篇 |
2014年 | 19篇 |
2013年 | 27篇 |
2012年 | 23篇 |
2011年 | 33篇 |
2010年 | 37篇 |
2009年 | 49篇 |
2008年 | 41篇 |
2007年 | 35篇 |
2006年 | 19篇 |
2005年 | 33篇 |
2004年 | 25篇 |
2003年 | 23篇 |
2002年 | 21篇 |
2001年 | 14篇 |
2000年 | 7篇 |
1999年 | 9篇 |
1998年 | 17篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 7篇 |
1984年 | 15篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1973年 | 3篇 |
1966年 | 1篇 |
排序方式: 共有658条查询结果,搜索用时 390 毫秒
651.
David Gallego-Torres Oscar E. Romero Francisca Martínez-Ruiz Jung-Hyun Kim Barbara Donner Miguel Ortega-Huertas 《Quaternary Research》2014
Previous paleoceanographic studies along the NW African margin focused on the dynamics of surface and intermediate waters, whereas little attention has been devoted to deep-water masses. Currently, these deep waters consist mainly of North Atlantic Deep Waters as part of the Atlantic Meridional Overturning Circulation (AMOC). However, this configuration was altered during periods of AMOC collapse. We present a high-resolution reconstruction of bottom-water ventilation and current evolution off Mauritania from the last glacial maximum into the early Holocene. Applying redox proxies (Mo, U and Mn) measured on sediments from off Mauritania, we describe changes in deep-water oxygenation and we infer the evolution of deep-water conditions during millennial-scale climate/oceanographic events in the area. The second half of Heinrich Event 1 and the Younger Dryas were recognized as periods of reduced ventilation, coinciding with events of AMOC reduction. We propose that these weakening circulation events induced deficient deep-water oxygenation in the Mauritanian upwelling region, which together with increased productivity promoted reducing conditions and enhanced organic-matter preservation. This is the first time the effect of AMOC collapse in the area is described at high resolution, broadening the knowledge on basin-wide oceanographic changes associated with rapid climate variability during the last deglaciation. 相似文献
652.
653.
654.
Hervé Piégay Fanny Arnaud Barbara Belletti Mélanie Bertrand Simone Bizzi Patrice Carbonneau Simon Dufour Frédéric Liébault Virginia Ruiz-Villanueva Louise Slater 《地球表面变化过程与地形》2020,45(1):157-188
The rivers of the world are undergoing accelerated change in the Anthropocene, and need to be managed at much broader spatial and temporal scales than before. Fluvial remote sensing now offers a technical and methodological framework that can be deployed to monitor the processes at work and to assess the trajectories of rivers in the Anthropocene. In this paper, we review research investigating past, present and future fluvial corridor conditions and processes using remote sensing and we consider emerging challenges facing fluvial and riparian research. We introduce a suite of remote sensing methods designed to diagnose river changes at reach to regional scales. We then focus on identification of channel patterns and acting processes from satellite, airborne or ground acquisitions. These techniques range from grain scales to landform scales, and from real time scales to inter-annual scales. We discuss how remote sensing data can now be coupled to catchment scale models that simulate sediment transfer within connected river networks. We also consider future opportunities in terms of datasets and other resources which are likely to impact river management and monitoring at the global scale. We conclude with a summary of challenges and prospects for remotely sensed rivers in the Anthropocene. © 2019 John Wiley & Sons, Ltd. 相似文献
655.
Leptiminus, a Roman port city on the west coast of Tunisia, North Africa, exported olive oil and a garum fish paste to Rome. Excavations have uncovered many facilities including kilns and a potter's workshop, indicating an extensive ceramic industry. The vessels, manufactured at Leptiminus, included African red‐slip fineware, coarseware, and amphorae. A petrographic study of pottery sherds showed them to contain very similar temper, rounded aeolian sand grains and limestone, but varying in proportions to produce different textures. An investigation of the source of raw materials for the pottery found three distinct types of clay within a 50 km radius of Leptiminus: grey Miocene, brown Pliocene, and green Late Pliocene clay. Statistical analysis of trace element compositions, using induced neutron activation, of clays and sherds showed that the Pliocene brown clay was used to create all types of pottery. The specific clay horizon, used in Roman times, has apparently been removed by quarrying. However, a lateral continuation of this bed was found 7 m beneath the Leptiminus site 290. © 2002 Wiley Periodicals, Inc. 相似文献
656.
Samples from extremely acidic waters should be taken using the introduced syringe technique avoiding atmospheric contact to minimize CO2 evaporation from the samples. The syringe technique inclusive manual injection enables the determination of TIC in acid waters with high precision and accuracy. If a TOC analyser with a small sample volume is used, the vials should be filled directly inside the water sampler without air bubbles, covered with aluminium foil and transported at ambient water temperatures. If an autosampler is used, partial selection of the vials increases the stability of the results. Care should be taken that samples can be analysed within a short time. 相似文献
657.
Barbara Rumsby 《地球表面变化过程与地形》2000,25(6):617-631
A wide range of approaches has been adopted for collecting and reporting vertical accretion rates, hence evaluation of results from different catchments, or even from different reaches within the same basin, is difficult as they may not be directly comparable. The present study compares depth‐ and volume‐based estimates of sediment accumulation for well‐dated vertical accretion sequences at Broomhaugh Island in the Tyne basin, northern England. High resolution dating control (based on heavy metal stratigraphy and cartography) coupled with detailed reconstruction of channel geometry allows accumulation rates to be calculated for the last 300–400 years. The results show a marked disparity in the magnitude and pattern of vertical accretion rates between the two approaches. The average annual thickness of sediment increases progressively, with a six‐fold difference between the seventeenth and twentieth centuries. The volume figures are more consistent, with a two‐fold difference between the highest and lowest rates, both of which occurred in the twentieth century. A major control on vertical accretion is found to be changing channel shape and capacity. Enlargement of the channel by 76 per cent since the seventeenth century, associated with channel bed incision, has resulted in fewer overbank flows. Hence floods, with their associated suspended sediment loads, which once inundated the floodplain are now confined within the channel. The reduced areal extent of surfaces available for deposition has resulted in greater annual thickness of sediment accumulated, despite an overall reduction in volume. This study emphasizes that caution is needed when attempting to identify causal linkages between changes in sedimentation rates and catchment land use and/or climatic factors and the geomorphological setting of the site must be taken into account. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
658.
P. G. Brown P. J. A. McCausland A. R. Hildebrand L. T. J. Hanton L. M. Eckart H. Busemann D. Krietsch C. Maden K. Welten M. W. Caffee M. Laubenstein D. Vida F. Ciceri E. Silber C. D. K. Herd P. Hill H. Devillepoix Eleanor K. Sansom Martin Cupák Seamus Anderson R. L. Flemming A. J. Nelson M. Mazur D. E. Moser W. J. Cooke D. Hladiuk Barbara Malečić Maja Telišman Prtenjak R. Nowell The Golden Meteorite Consortium 《Meteoritics & planetary science》2023,58(12):1773-1807