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Lower Cretaceous red sedimentary rocks from the depositional basin of East Qilian fold belt have been collected for a paleomagnetic study. Stepwise thermal demagnetization reveals two or three components of magnetization from dark red sandstones. Low-temperature magnetic component is consistent with the present Earth Field direction in geographic coordinates. High-temperature magnetic components are mainly carried by hematite. The mean pole of 19 sites for high-temperature magnetic components after tilt-correction is λ=62.2°N, φ=193.4°E, A95=3.2°, and it passes fold tests at 99% confidence level and reversal tests at 95% confidence level. The paleopole is insignificantly different from that of Halim et al. (1998) from the same sampling area at the 95% confidence level. Compared with paleomagnetic results for North China, South China, and Eurasia, our results suggest that no significant relative latitudinal displacement has taken place between Lanzhou region and these blocks since Cretaceous time. Remarkably, the pole of Lanzhou shows a 20° clockwise rotation with respect to those of North China, South China, and Eurasia. Geological information indicates that the crustal shortening in the western part of Qilian is greater than that in eastern part. In this case, the clockwise rotation of sampling area was related to India/Eurasia collision, and this collision resulted in a left-lateral strike-slip motion of the Altun fault in north Tibetan Plateau after the Cretaceous. 相似文献
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西安翠华山山崩地质遗迹资源保护 总被引:5,自引:3,他引:5
文论述了西安翠华山山崩地质遗迹资源保护的目的,进行了保护分区,将其分为核心保护区、缓冲区和视域保护区三个区,重点分析了核心保护区的保护现状,并在此基础上提出了相应的保护内容和对策,以实现山崩地质遗迹资源的可持续利用和发展。 相似文献
26.
《The Professional geographer》2002,54(3):454-478
Books Reviewed Colbert C. Held, Middle East Patterns: Places, People, and Politics Barbara A. Weightman, Dragons and Tigers: A Geography of South, East, and Southeast Asia Henry J. Bruman, Alcohol in Ancient Mexico Brian W. Blouet, Geopolitics and Globalization in the Twentieth Century M. A. B. Siddique (ed.), International Migration into the 21st Century: Essays in Honour of Reginald Appleyard Michael R. Haines and Richard H. Steckel (eds.), A Population History of North America Emilio Moran, Human Adaptability: An Introduction to Ecological Anthropology Jeremy Leggett, The Carbon War: Global Warming and the End of the Oil Era Susan B. Marriott and Jan Alexander (eds.), Floodplains: Interdisciplinary Approaches William S.Logan, Hanoi: Biography of a City Alex Krieger and David Cobb (eds.) with Amy Turner, Mapping Boston Eric Sandweiss, St. Louis: The Evolution of an American Urban Landscape Carl Abbott, Greater Portland: Urban Life and Landscape in the Pacific Northwest Arthur D. Murphy, Colleen Blanchard and Jennifer A. Hill (eds.), Latino Workers in the Contemporary South Yanek Mieczkowski, The Routledge Historical Atlas of Presidential Elections 相似文献
27.
海南省五指山土壤中的重金属元素含量 总被引:6,自引:0,他引:6
海南省地处热带地区,山地面积占25.4%,五指山是海南山地的核心,也是海南最高峰,从下而上依次分布着砖红壤、赤红壤、黄壤、灌丛草甸土。五指山土壤普遍遍缺,而Zn、Ni、Pb、Cd、Cr、Co含量属正常值。在成土过程中,Cd有一定积累,其他元素有明显淋溶。在自下而上的垂直带谱中,Zn、Co含量呈现递减,Cd则相反,Ni、Pb、Cu、Cr含量呈现波浪式变化。气候因素是影响五指山土壤重金属元素含量及分布的主导因素。 相似文献
28.
南岳衡山自然景观资源及其开发利用探讨 总被引:1,自引:2,他引:1
谢莉 《云南地理环境研究》2003,15(2):54-59
南岳衡山是中国南方唯一的一座五岳名山,也是中国历史上南方最大的文化、宗教活动中心,素享“五岳独秀”、“文明奥区”、“宗教圣地”、“抗战名山”等盛名,是中国第一批国家级风景名胜区,具有独特的景观美学价值、丰富的科学艺术内容、多彩的景观景目。经数千年人类文明洗礼,又使其积淀了深厚的历史文化,衡山的景观资源开发潜力巨大,但必须坚持可持续发展战略,开发与保护并重,加强规划,合理布局,进一步优化自然生态环境,推出南岳特色生态旅游精品系列,以满足当代旅游者回归自然、绿色消费的心理需求。 相似文献
29.
W. Andrew Marcus Carl J. Legleiter Richard J. Aspinall Joseph W. Boardman Robert L. Crabtree 《Geomorphology》2003,55(1-4):363
This article evaluates the potential of 1-m resolution, 128-band hyperspectral imagery for mapping in-stream habitats, depths, and woody debris in third- to fifth-order streams in the northern Yellowstone region. Maximum likelihood supervised classification using principal component images provided overall classification accuracies for in-stream habitats (glides, riffles, pools, and eddy drop zones) ranging from 69% for third-order streams to 86% for fifth-order streams. This scale dependency of classification accuracy was probably driven by the greater proportion of transitional boundary areas in the smaller streams. Multiple regressions of measured depths (y) versus principal component scores (x1, x2,…, xn) generated R2 values ranging from 67% for high-gradient riffles to 99% for glides in a fifth-order reach. R2 values were lower in third-order reaches, ranging from 28% for runs and glides to 94% for pools. The less accurate depth estimates obtained for smaller streams probably resulted from the relative increase in the number of mixed pixels, where a wide range of depths and surface turbulence occurred within a single pixel. Matched filter (MF) mapping of woody debris generated overall accuracies of 83% in the fifth-order Lamar River. Accuracy figures for the in-stream habitat and wood mapping may have been misleadingly low because the fine-resolution imagery captured fine-scale variations not mapped by field teams, which in turn generated false “misclassifications” when the image and field maps were compared.The use of high spatial resolution hyperspectral (HSRH) imagery for stream mapping is limited by the need for clear water to measure depth, by any tree cover obscuring the stream, and by the limited availability of airborne hyperspectral sensors. Nonetheless, the high accuracies achieved in northern Yellowstone streams indicate that HSRH imagery can be a powerful tool for watershed-wide mapping, monitoring, and modeling of streams. 相似文献
30.
The Nanga Parbat Himalaya presents some of the greatest relief on Earth, yet sediment production and denudation rates have only been sporadically addressed. We utilized field measurements and computer models to estimate bank full discharge, sediment transport, and denudation rates for the Raikot and Buldar drainage basins (north slope of Nanga Parbat) and the upper reach of the Rupal drainage basin (south slope).The overall tasks of determining stream flow conditions in such a dynamic geomorphic setting is challenging. No gage data exist for these drainage basins, and the overall character of the drainage basins (high relief, steep flow gradients, and turbulent flow conditions) does not lend itself to either ready access or complete profiling.Cross-sectional profiles were surveyed through selected reaches of these drainage basins. These data were then incorporated into software (WinXSPRO) that aids in the characterization (stage, discharge, velocity, and shear stress) of high altitude, steep mountain stream conditions.Complete field measurements of channel depths were rarely possible (except at several bridges where the middle of the channel could actually be straddled and probed) and, when coupled with velocity measurements, provided discrete points of field-measured discharge calculations. These points were then used to calibrate WinXSPRO results for the same reach and provided a confidence level for computer-generated results.Flow calculations suggest that under near bank full conditions, the upper Raikot drainage basin produces discharges of 61 cm and moves about 11,000 tons day−1 (9980 tons day−1) of sediment through its channel. Bank full conditions on the upper portion of the Rupal drainage basin generate discharges of 84 cm and moves only about 3800 tons day−1 (3450 tons day−1) of sediment. Although the upper Rupal drainage basin moves more water, the lower slope of the drainage basin (0.03) generates a much smaller shear stress (461 Pa) than does the higher slope (0.12) of the upper Raikot drainage basin (1925 Pa).Dissolved and suspended sediment loads were measured from water/sediment samples collected throughout the day and night over a period of 10 days at the height of the summer melt season but proved to be a minor variable in transport flux. Channel bed loads were measured using a pebble count method of bank material and then used to generate ratings curves of bed loads relative to discharge volumes. When coupled with discharge data and basin area, mean annual sediment yield and denudation rates for Nanga Parbat are produced. Denudation rates calculated in this fashion range from 0.2 mm year−1 in the slower, more sluggish Rupal drainage basin to almost 6 mm year−1 in the steeper, faster flowing Raikot and Buldar drainage basins. 相似文献