全文获取类型
收费全文 | 2429篇 |
免费 | 418篇 |
国内免费 | 629篇 |
专业分类
测绘学 | 118篇 |
大气科学 | 515篇 |
地球物理 | 590篇 |
地质学 | 1239篇 |
海洋学 | 313篇 |
天文学 | 159篇 |
综合类 | 240篇 |
自然地理 | 302篇 |
出版年
2024年 | 8篇 |
2023年 | 59篇 |
2022年 | 136篇 |
2021年 | 154篇 |
2020年 | 94篇 |
2019年 | 119篇 |
2018年 | 171篇 |
2017年 | 139篇 |
2016年 | 161篇 |
2015年 | 119篇 |
2014年 | 157篇 |
2013年 | 142篇 |
2012年 | 118篇 |
2011年 | 133篇 |
2010年 | 149篇 |
2009年 | 128篇 |
2008年 | 112篇 |
2007年 | 92篇 |
2006年 | 71篇 |
2005年 | 80篇 |
2004年 | 42篇 |
2003年 | 65篇 |
2002年 | 54篇 |
2001年 | 46篇 |
2000年 | 87篇 |
1999年 | 119篇 |
1998年 | 97篇 |
1997年 | 94篇 |
1996年 | 90篇 |
1995年 | 100篇 |
1994年 | 71篇 |
1993年 | 64篇 |
1992年 | 46篇 |
1991年 | 30篇 |
1990年 | 23篇 |
1989年 | 24篇 |
1988年 | 21篇 |
1987年 | 12篇 |
1986年 | 12篇 |
1985年 | 10篇 |
1984年 | 5篇 |
1983年 | 9篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1958年 | 2篇 |
排序方式: 共有3476条查询结果,搜索用时 31 毫秒
961.
欧亚大陆及边缘海岩石圈的结构特性 总被引:2,自引:0,他引:2
从地球层块结构的研究思路出发,运用构造解析的理论和方法,对东亚及西太平洋地区人工地震测深和天然地震面波层析成像进行构造解析,发现岩石圈中下部存在形态各异、大小不等的高速块体,结合地质学、地球化学及其他地球物理学标志的综合研究将其称为幔块构造,高速块体或幔块构造是控制东亚西太平洋岩石圈构造格局和岩石圈表层构造变形最基本条件之一。在系统研究该区岩石圈高速块体或幔块构造三维几何结构基础上,建立起东亚西太平洋岩石圈八种三维几何结构型式:克拉通陆根状结构、高原陆根状结构、造山带楔状结构、碎块状结构、香肠状结构、哑铃状结构、藕节状结构和板状结构,以及岩石圈形成与构造演化四种构造类型:克拉通型岩石圈、增厚型岩石圈、减薄型岩石圈和大洋型岩石圈。文章在详细论述岩石圈各结构构造类基本特征的基础上,认为全球最大的青藏高原具有增厚型岩石圈特性,存在大陆根,并且大陆根正在增厚过程中;地震层析成像显示,研究区存在全球最大的东亚大陆巨型裂谷体系,具有减薄型岩石圈特性,新生代晚期东亚大陆巨型裂谷体系被西太平洋沟弧盆体系叠加与改造。根据岩石圈三维结构型式,探讨了岩石圈形成机制与演化模式,东亚大陆边缘岩石圈大规模伸展拆沉减薄作用以及软流圈和地幔物质上涌加热作用与青藏高原岩石圈大规模俯冲碰撞?入增厚作用是东亚大陆及边缘海晚中生代以来地幔动力学最基本的表现型式,从而形成全球最大的青藏高原和全球最大的东亚大陆巨型裂谷体系。 相似文献
962.
基于ArcEngine的三维地形可视化系统的研究与开发 总被引:1,自引:0,他引:1
ArcGIS Engine是ESRI公司在ArcGIS 9.O版本中发布的一个面向开发人员的产品,主要用来构建桌面的GIS应用.本文阐述了建立地形三维可视化系统的方法、技术途径及其关键技术,基于ArcEngine平台开发了一套三维地形可视化软件,实现了三维浏览、信息查询、地形分析等功能. 相似文献
963.
Coseismic water level oscillation and correlated deep water temperature changes have been observed in a water well at Tangshan City by high sensitivity measurement. Amount of water temperature changes depend on ampli-tude of water level oscillation. Coseismic water temperatures always decrease as water level oscillates, drop of temperature ranges from 0.001 °C to 0.01 °C corresponding to amplitude of water level oscillation from several centimeters to about one meter. Temperatures usually recover one to several hours after the oscillation. We suggest that the temperature drop is produced by dispersive transfer of heat as the water oscillates, and follow-up thermal conduction makes temperature recovery. Our finite element calculations support quantitatively the idea. High ac-curacy measurements of water temperature at different depths in the future may test our interpretation. 相似文献
964.
Tectono-chronologic constraints on a Mesozoic slip and thrust belt in the eastern Jiaodong Peninsula 总被引:1,自引:0,他引:1
A major slip and thrust belt within the eastern Jiaodong Peninsula is located at the eastern terminal of the Qinling-Dabie-Sulu orogenic belt between the Sino-Korea Block and Yangtze Block. Although a lot of isotope chronologic data have been obtained regionally, little structural chronological research has been conducted in this region and this paper corrects that. Syn-deformational minerals were system-atically selected from samples of the NE-ENE trending transpressional shear zones and transpres-sional nappes and carefully analysed using 40Ar/39Ar methods. Two tectonic events were defined with the first event resulting from early movement of transpressional nappes around 190 Ma ago. This ac-cords with the period of syn-orogenic sinistral slip of the Tan-Lu faults and clockwise shear in the Eastern Qinling-Tongbaishan part of the Qinling-Dabie-Sulu orogenic belt. The second event involved strikeslip thrust movement of deep shear zones between 130Ma and 120Ma. This resulted from the onset of Mesozoic tectonic conversion in the eastern Jiaodong Peninsula. The sinistral strikeslip-thrusting in Jiaodong Peninsula and the extensional tectonism (toward ESE) in Liaodong Peninsula probably resulted in the clockwise rotation of Korea Peninsula in late Mesozoic. 相似文献
965.
Spatial patterns of terrestrial net ecosystem productivity in China during 1981–2000 总被引:1,自引:0,他引:1
Tao Bo Cao MingKui Li KeRang Gu FengXue Ji JinJun Huang Mei Zhang LeiMing 《中国科学D辑(英文版)》2007,50(5):745-753
As the third largest country in the world, China has highly variable environmental condition and ecological pattern in both
space and time. Quantification of the spatial-temporal pattern and dynamic of terrestrial ecosystem carbon cycle in China
is of great significance to regional and global carbon budget. In this study, we used a high-resolution climate database and
an improved ecosystem process-based model to quantify spatio-temporal pattern and dynamic of net ecosystem productivity (NEP)
in China and its responses to climate change during 1981 to 2000. The results showed that NEP increased from north to south
and from northeast to southwest. Positive NEP (carbon sinks) occurred in the west of Southwest China, southeastern Tibet,
Sanjiang Plain, Da Hinggan Mountains and the mid-west of North China. Negative NEP (carbon sources) were mainly found in Central
China, the south of Southwest China, the north of Xinjiang, west and north of Inner Mongolia, and parts of North China. From
the 1980s to 1990s, the increasing trend of NEP occurred in the middle of Northeast China Plain and the Loess Plateau and
decreasing trends mainly occurred in a greater part of Central China. In the study period, natural forests had minimal carbon
uptake, while grassland and shrublands accounted for nearly three fourths of the total carbon terrestrial uptakes in China
during 1981–2000.
Supported by the Ministry of Science and Technology of China (G2002CB412507), the Major Program of the National Natural Science
Foundation of China (Grant No.30590384), the “Hundred Talent” Program of the Chinese Academy of Sciences, and K C WONE Education
Foundation 相似文献
966.
中国大陆黑碳气溶胶排放清单 总被引:1,自引:0,他引:1
The detailed high-resolution emission inventory of black carbon (BC) from China in the year 2000 was calculated. The latest fuel consumption data including fossil and biomass fuels, and socio-economic statistics used were obtained from government agencies, mostly at the county level, and some new emission factors (Efs) from local measurements were also used. National and regional summaries of emissions were presented at 0.2°×0.2°resolution. Total BC emission was 1499.4 Gg in 2000, mainly due to the burning of coal and biomass. The BC emission estimated here is higher than those in previous studies, mainly because the emissions from coal burning by rural industries and residences were previously underestimated. More BC aerosols were emitted from eastern China than western China. A strong seasonal dependence was observed for BC emissions, with peaks in January and December and low emissions in July and August; and this seasonality is mainly due to patterns in residential heating and the open burning of crop residues. 相似文献
967.
Cao Jian Hu WenXuan Yao SuPing Zhang YiJie Wang XuLong Zhang YueQian Tang Yong Shi XinPu 《中国科学D辑(英文版)》2007,50(12):1796-1809
Electronic probe microanalysis(EPMA) results of reservoir calcite cement from fourteen core samples in the Junggar Basin show that Mn-content varies largely between different samples from below the detect limitation to 4.14%,while it displays a generally good correlation with oil-gas shows.This,therefore,likely indicates that concentration of the Mn-content of the calcite cement has a close rela-tion to the intensity of petroleum fluid charging during hydrocarbon secondary migration.In order to assess this hypothesis,oxygen and strontium isotopic measurements on sixteen calcite veins host in source sequences were carried out to investigate the feature of the oil-source petroleum fluid.Analytical results imply that during hydrocarbon generation and migration,deep hot fluid has dissolved volcanic minerals interlined between mudstone source rocks.As Mn is a kind of typical trace element enriched in volcanic rocks,it is reasonable to conclude that the petroleum fluid formed in the source sequences would be Mn-rich.Consequently,calcite cements precipitated from such Mn-rich petroleum fluid would be Mn-rich accordingly.Due to the geologic chromatographic effect during migration along reservoir rocks,the decreasing of the Mn-content of the reservoir calcite cements indicates the migration direction.Then,this novel geotracer was further successfully applied in the study of hydrocarbon migration in the Junggar Basin in combination with organic geochemical analyses during the hydrocarbon migration.The Mn content of the reservoir calcite cement appears promising as a novel inorganic geotracer for the petroleum migration.This paper represents a search for novel indicators of secondary petroleum migration in tectonically complex basins based on fundamentals of the reservoir fluid-rock interactions. 相似文献
968.
自动气象站维护及操作技巧 总被引:1,自引:0,他引:1
对自动气象站软件、硬件及网络通信三个方面的主要故障现象进行了总结,介绍了使用维护注意事项和技巧,提出了故障排除方法。 相似文献
969.
科学计算可视化是20世纪80年代后期随着计算机图形学应用的拓广而发展起来的一个新的研究分支,受其推动,数字信息的可视化成为20世纪90年代研究的前缘。随着“数字地球”、“数字城市”、“数字油田”等概念的提出,气象工作者迫切需要更加精确地了解各种气象数据和地形实体。而对于这些复杂的数据资料,目前人们已不能满足于等线图那样的平面描述,更需要建立三维图像,用更接近实际的方式去描述它,从各个不同角度观察它,三维可视化就是实现以上目标的有效手段。实体三维可视化技术是描绘和理解三维实体的一种重要计算机技术,它可以帮助使用者快速、准确理解和描述三维实体,并能协助快速选定感兴趣的目标,为分析、理解数据提供了有利工具。 相似文献
970.