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631.
632.
本文对北大别西部的湖北英山万家老屋、罗田七道河尹家店和安徽金寨丁埠乡李集3个片麻岩样品中锆石进行了BSE显微结构分析,并在此基础上对锆石进行了离子探针U-Pb年龄测定。结果表明北大别存在两种类型的片麻岩,它们的原岩分别形成于晋宁期和燕山期,其中英山万家老屋片麻岩的形成年龄为794Ma,后期地质事件对其锆石U-Pb年龄造成的影响较小;七道河尹家店片麻岩的形成年龄为730Ma,并可能受到燕山期岩浆事件的影响,得到了140Ma左右的变质年龄;丁埠乡李集片麻岩的形成年龄为140Ma。结合已有的年代学结果,北大别地体广泛存在晋宁期的岩浆事件,表明其可能为扬子板块的北缘。 相似文献
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Current Trends and Demands in Visualization in the Geosciences 总被引:1,自引:0,他引:1
Geosciences, along with many other disciplines in science and engineering, faces an exponential increase in the amount of
data generated from observation, experiment and large-scale, high-resolution 3-D numerical simulations. In this communication
we describe the fundamentals of visualization necessary to meet these challenges. We present several alternative methodologies
such as 2D/3D feature extraction, segmentation methods, and flow topology, to help better understand the physical structure
of the data. We use AMIRA from TGS to demonstrate our concepts. Examples are drawn from fields in computational fluid dynamics,
3-D mantle convection and seismic tomography. Finally, we present our perspective on the future of visualization. 相似文献
635.
The Koyna River basin in India drew the attention of geoscientists after an earthquake (magnitude 7) in 1967. Since then,
detailed geological, tectonic, and seismic investigations of this river basin have been carried out by several workers. However,
very little study has been done on its hydrogeological framework. The present work aims at filling this gap. Basalts, laterites,
alluvium, soils, and talus deposits form shallow unconfined aquifers, with transmissivity of 27–135 m2/d and a regional specific yield of 0.012. In shallow basaltic aquifers, the lower part of the highly weathered and highly
jointed horizon above, and the poorly weathered and highly jointed horizon below, form the most potential zone for groundwater
occurrence. Well yields in the deeper basaltic aquifers are directly related to the occurrence of lineaments, whereas at a
shallower level they are related to geomorphic features. Spring discharges are highly dependent on their source aquifers and
areas of recharge. They have a mean winter discharge of 46 m3/d and a summer discharge of 28 m3/d.
Chemically, groundwaters are dominated by alkaline earths (Ca2+, Mg2+) and weak acids (HCO3
–, CO3
–); they are calcium-bicarbonate type (53%) and calcium-magnesium-bicarbonate type (27%) at shallower levels; and calcium-magnesium-bicarbonate
type (29%), sodium-bicarbonate type (24%), calcium-bicarbonate type (19%), and calcium-magnesium-sodium-bicarbonate type (19%)
in deeper aquifers. The Koyna River basin is characterized by both scarcity and abundance of groundwater. In the water-scarce
areas in the dissected plateaus, artificial recharge of aquifers through construction of several recharge structures at suitable
locations is highly recommended. In the water-abundant areas in the central valley, on the other hand, expanded consumptive
use of water resources is encouraged.
Electronic Publication 相似文献
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GIS中的地形可视化与地形模型简化 总被引:3,自引:0,他引:3
地形可视化是一门以研究数字地形模型或数字高程域的显示、简化、仿真等内容的学科 ,属于计算机图形学的一个分支。GIS中的地形可视化有助于用户对空间数据相互关系以及分析结果的直观理解。文中分析了GIS中地形建模的基本问题 ,研究了地形模型简化与多分辨率地形模型的发展 相似文献
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639.
The use of the metaphors of general fitness and N-K spaces can assist in the understanding of the development of the physical landscape. Different modes of change can be viewed as different types of movement in, and distortions of, these phase spaces. Visualized in this manner landscape change can be viewed as both channelized, constrained and random. 相似文献
640.
There is a growing interest in investigating the accuracy of digital elevation model (DEM). However people usually have an unbalanced view on DEM errors. They emphasize DEM sampling errors, but ignore the impact of DEM resolution and terrain roughness on the accuracy of terrain representation. This research puts forward the concept of DEM terrain representation error (Et) and then investigates the generation, factors, measurement and simulation of DEM terrain representation errors. A multi-resolution and multi-relief comparative approach is used as the major methodology in this research. The experiment reveals a quantitative relationship between the error and the variation of resolution and terrain roughness at a global level. Root mean square error (RMS Et) is regressed against surface profile curvature (V) and DEM resolution (R) at 10 resolution levels. It is found that the RMS Et may be expressed as RMS Et = (0.0061 × V+ 0.0052) × R - 0.022 × V + 0.2415. This result may be very useful in forecasting DEM accuracy, as well as in determining the DEM resolution related to the accuracy requirement of particular application. 相似文献