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41.
This paper describes a multi‐proxy palaeoecological investigation undertaken in conjunction with an archaeological survey of the Upper Sangro Valley in the Abruzzo National Park, Central Italy. Despite being a biodiversity hotspot and regarded as a near‐pristine area, the pollen, spore and diatom data all show major changes in the vegetation extending to over 2000 m a.s.l. during the mid to late Holocene. Although there are changes in ecological composition earlier in the Holocene they are different in type and magnitude from the changes which began about 800 cal a BC. The pollen and diatom evidence do not correlate well with regional palaeoclimate data, or on‐site isotopic evidence, but do appear to be related to Samnite (later Iron Age) clearance and upland grazing associated with transhumance and later annexation (and centuriation) of the lower slopes by Roman surveyors. The greatest change in vegetation was during the period c. AD 500–600 and corresponds with the Byzantine–Gothic Wars, and Lombard–Carolingian settlement reorganization into nucleated hilltop settlements which managed upland grazing. This pattern of intensive land use at all altitudes persisted until the early 20th century and only changed following rural depopulation after World War II. These data illustrate how cultural factors had a profound effect on this mountainous region which, in this case, far outweighed the effects of climatic fluctuations which are known to have occurred from both this study area and the region. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
42.
Ana Moreno Blas L. Valero‐Garcés Montserrat Jiménez‐Sánchez María José Domínguez‐Cuesta M. Pilar Mata Ana Navas Penélope González‐Sampériz Heather Stoll Pedro Farias Mario Morellón J. Pablo Corella Mayte Rico 《第四纪科学杂志》2010,25(7):1076-1091
A sedimentological and geochemical study of the Lago Enol sequence (Cantabrian Mountains, northern Spain), together with detailed geomorphological mapping, provides a first record of glacier evolution and climate change over the last 40 ka in the Picos de Europa National Park. The Enol glacier retreated from its maximum extent prior to 40 ka BP as demonstrated by the onset of proglacial lacustrine sedimentation in two glaciated depressions: the Comella hollow to the north (before 40 ka BP) and the Lago Enol (before 38 ka BP). These results support previous evidence that the maximum extent of southern European glaciers occurred earlier than in northern Europe. Alternation of homogeneous and laminated proglacial sediments during the glacier retreat illustrate a dynamic glacial evolution during the Marine Isotope Stage (MIS) 3 (40–26 ka BP). A slight warming is detected at 26 ka ago with the change from proglacial sediments (in a lake located in contact to the glacier) to glaciolacustrine sedimentation (in a non‐contact or distal lake). Finally, the onset of organic‐rich sediments took place at 18 ka ago. This last transition occurred in two phases, similarly to the North Atlantic Last Termination, suggesting a link between North Atlantic Deep Water formation oscillations and palaeohydrological variability in the Cantabrian Mountains. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
43.
从人口资源与生态环境的观点分析我国国情与农村经济发展 总被引:7,自引:0,他引:7
本文从人口与资源、生态环境等方面,简要地探讨了我国国情与农村经济发展的趋向,论述了人口与资源、环境的制约因素。认为只有通过严格控制人口,强化人力开发利用;节约资源,增加投入,挖掘潜力;增强环境保护意识,推行综合防治措施等有效途径,辩证地处理好生存与发展的关系,才能保证我国农村经济获得持续稳定协调发展。 相似文献
44.
本文认为,华南地区于燕山旋回中早期主压应力轴是北西——南东和北西西——南东东向的。燕山晚期以来,主压应力轴基本上是北东——南西和北东东——南西西乃至近东西向的。 相似文献
45.
本文从探空史、气象学史、气候学史、物侯学史、军事地理学史、数理地理学史以及科学家评介、自然科学史理论等几个侧面,较为系统地论述了竺可桢教授在地理学史方面的贡献.以此纪念竺可桢教授逝世二十周年. 相似文献
46.
Paul A. Knapp Judith M. Lancaster Kathleen A. Bishop Richard L. Taylor 《The Professional geographer》1993,45(3):323-331
This paper demonstrates the use of a Geographic Information System (GIS) to develop timber thinning strategies on the Kyburz Planning Area of the Tahoe National Forest in northeastern California. The primary criteria used in an assessment of selective thinning potential were forest health and fire hazard ratings. By eliminating environmentally sensitive, economically unfeasible, or low fire hazard areas from consideration, the use of GIS reduced the area that was considered appropriate for thinning by approximately 58%. GIS offers considerable potential for improving resource management strategies. 相似文献
47.
48.
Lauren Patterson Marie Urban Aaron Myers Budhendra Bhaduri Eddie Bright Phillip Coleman 《GeoJournal》2007,69(1-2):93-102
Geospatial technologies and digital data have developed and disseminated rapidly in conjunction with increasing computing
efficiency and Internet availability. The ability to store and transmit large datasets has encouraged the development of national
infrastructure datasets in geospatial formats. National datasets are used by numerous agencies for analysis and modeling purposes
because these datasets are standardized and considered to be of acceptable accuracy for national scale applications. At Oak
Ridge National Laboratory a population model has been developed that incorporates national schools data as one of the model
inputs. This paper evaluates spatial and attribute inaccuracies present within two national school datasets, Tele Atlas North
America and National Center of Education Statistics (NCES).
Schools are an important component of the population model, because they are spatially dense clusters of vulnerable populations.
It is therefore essential to validate the quality of school input data. Schools were also chosen since a validated schools
dataset was produced in geospatial format for Philadelphia County; thereby enabling a comparison between a local dataset and
the national datasets.
Analyses found the national datasets are not standardized and incomplete, containing 76 to 90 percent of existing schools.
The temporal accuracy of updating annual enrollment values resulted in 89 percent inaccuracy for 2003. Spatial rectification
was required for 87 percent of NCES points, of which 58 percent of the errors were attributed to the geocoding process. Lastly,
it was found that by combining the two national datasets, the resultant dataset provided a more useful and accurate solution. 相似文献
49.
The subject of the security fence between Israel and the Palestinians in the West Bank has become a major issue in Israel
and in the world in the last several years. The main aim of this research is to reveal the attitudes and thoughts about the
fence held by local residents living in settlements (borderlanders) in the proximity of a part of the security fence that
has already been completed. The research concentrates on the western-Israeli side of the fence, as it aspires to delve into
and understand the meaning and implications of the security fence on matters such as personal security, safety of property
and freedom of movement, the possibility of maintaining social and economic ties between the two sides and feelings about
living in the area in the future. Underlying this research is the transformation occurring in the border area as a result
of its closure by construction of the security fence, after many years in which it was open partially. This process has many
diverse consequences, some of them contradictory, on the two populations residing near the border in Israel: the majority
Jewish population (the national borderlanders), and the minority Arab population (the transnational borderlanders). 相似文献
50.
The karst landscape in the interior of the Philippines' Bohol Province represents one of the world's premier kegelkarst (cone karst) environments. Government efforts to protect some of this karst, exemplified by the establishment of the Rajah Sikatuna National Park and the Chocolate Hills Natural Monument, have proven to be significant catalysts of social conflict. In Bohol there is a long history of traditional land tenure, which has recently been supplanted by a Westernized model. Protected area establishment is a response to deforestation, agricultural exploitation and uncontrolled quarrying. However, the imposition of protective legislation to prevent further degradation has disenfranchized and marginalized many local farmers and residents. The conflict between the obligation of the State to ensure environmental protection and the perceived property rights of landowners and farmers has provoked an escalation in civil unrest and armed conflict. 相似文献