全文获取类型
收费全文 | 609篇 |
免费 | 26篇 |
国内免费 | 3篇 |
专业分类
测绘学 | 44篇 |
大气科学 | 44篇 |
地球物理 | 144篇 |
地质学 | 199篇 |
海洋学 | 20篇 |
天文学 | 113篇 |
综合类 | 5篇 |
自然地理 | 69篇 |
出版年
2023年 | 4篇 |
2022年 | 5篇 |
2021年 | 12篇 |
2020年 | 12篇 |
2019年 | 21篇 |
2018年 | 19篇 |
2017年 | 18篇 |
2016年 | 28篇 |
2015年 | 23篇 |
2014年 | 24篇 |
2013年 | 50篇 |
2012年 | 37篇 |
2011年 | 21篇 |
2010年 | 24篇 |
2009年 | 39篇 |
2008年 | 24篇 |
2007年 | 30篇 |
2006年 | 23篇 |
2005年 | 32篇 |
2004年 | 23篇 |
2003年 | 19篇 |
2002年 | 23篇 |
2001年 | 16篇 |
2000年 | 15篇 |
1999年 | 10篇 |
1998年 | 4篇 |
1997年 | 6篇 |
1996年 | 7篇 |
1995年 | 7篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1987年 | 6篇 |
1986年 | 1篇 |
1984年 | 6篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1970年 | 1篇 |
排序方式: 共有638条查询结果,搜索用时 747 毫秒
131.
Bettina Knig Oliver Kohls Gerhard Holst Ronnie N. Glud Michael Kühl 《Marine Chemistry》2005,97(3-4):262-276
We describe the fabrication of organically modified sol–gel (ORMOSIL) planar optodes for mapping the two-dimensional oxygen distribution in sediments. All sensor foils were based on the use of ruthenium(II)-tris-(4,7-diphenyl-1,10-phenantrolin)-perchlorate, which is a fluorescent dye quenched dynamically by oxygen. Sensors made with different sol–gel immobilisation matrices, different concentrations of precursors and indicator dye, as well as different types of scattering particles co-immobilised in the sensor foil were investigated systematically. Optimal sensor performance was obtained with dye concentrations of 2–10 mmol/kg in an immobilisation matrix made of diphenyldiethoxy-silan and phenyltriethoxy-silan precursors with addition of organically coated TiO2 particles. The sensors exhibited a good mechanical stability and a high sensitivity from 0% to 100% oxygen, which remained constant over at least 36 days. The planar optodes were used with a fluorescent lifetime imaging system for direct mapping of the spatio-temporal variation in oxygen distribution within marine sediment inhabited by the polychaete Hediste diversicolor. The measurements demonstrated the spatio-temporal heterogeneity of the oxygen distribution in bioturbated sediments due to burrow structures and non-constant irrigation activity of the polychaete, which is difficult to resolve with microsensors or with traditional biogeochemical techniques. 相似文献
132.
Rhys Harris Robert McCall Oliver Randall Muhammad Hafiz Bin Tawang Rhys Williams Jonathan G. Fairman David M. Schultz 《Geology Today》2017,33(6):210-215
The transition from the Triassic to Jurassic is associated with dramatic changes in Earth's climate. Pangaea was breaking up as North America rifted away from Africa, the Central Atlantic Magmatic Province erupted, and the concentration of atmospheric carbon dioxide increased dramatically. This article summarises the changes in Earth's climate associated with this transition, including a discussion of the various impacts of the increased carbon dioxide on the Earth system, the question of whether the wet episode in the Carnian was a global or regional event, the formation of bauxite deposits, and how dinosaur distributions changed over time. Palaeoclimate model simulations reveal the spatial changes in climate between the Triassic and Jurassic, illustrating the subtropics becoming slightly cooler and wetter despite the warming trend for the Earth's average temperature. 相似文献
133.
134.
Nicholas J. Clifford Philip J. Soar Oliver P. Harmar Angela M. Gurnell Geoffrey E. Petts Joanne C. Emery 《水文研究》2005,19(18):3631-3648
Output from a three‐dimensional numerical flow model (SSIIM) is used in conjunction with high‐resolution topographic and velocity data to assess such models for eco‐hydraulic applications in river channel design and habitat appraisal. A new methodology for the comparison between field measurement and model output is detailed. This involves a comparison between conventional goodness‐of‐fit approaches applied to a spatially structured (riffle and pool) sample of model and field data, and a ‘relaxation’ method based upon the spatial semivariance of model/field departures. Conventional assessment indicates that the model predicts point‐by‐point velocity characteristics on a 0·45 m mesh to within ±0·1 m s−1 over 80% of the channel area at low flow, and 50% of the area at high in‐bank flow. When a relative criterion of model fit is used, however, the model appears to perform less well: 60–70% of channel area has predicted velocities that depart from observed velocities by more than 10%. Regression analysis of observed and predicted velocities gives more cause for optimism, but all of these conventional indicators of goodness of fit neglect important spatial characteristics of model performance. Spatial semivariance is a means of supplementing model appraisal in this respect. In particular, using the relaxation approach, results are greatly improved: at a high in‐bank flow, the model results match field measurements to within 0·1 m s−1 for more than 95% of the total channel area, provided that model and field comparisons are allowed within a radius of approximately 1 m from the original point of measurement. It is suggested that this revised form of model assessment is of particular relevance to eco‐hydraulic applications, where some degree of spatial and temporal dynamism (or uncertainty) is a characteristic. The approach may also be generalized to other environmental science modelling applications where the spatial attributes of model fits are of interest. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
135.
The first dinosaur tracksite from Xinjiang, NW China (Middle Jurassic Sanjianfang Formation, Turpan Basin) a preliminary report 总被引:1,自引:0,他引:1
A new dinosaur tracksite was discovered in a steeply inclined sandstone layer of the Middle Jurassic Sanjianfang Formation in the Shanshan area of the Turpan Basin. The site is the first record of dinosaur footprints from Xinjiang Province in northwestern China. More than 150 tridactyl theropod dinosaur footprints are preserved as positive hyporeliefs on the lower bedding plane of a fine-grained sandstone body. Most of the footprints are isolated and appear to be randomly distributed. Some show well defined phalangeal pads, heels and rarely indistinct impressions of the distal part of the metatarsus. Two distinct morphotypes are present: a larger type with relatively broad pads shows similarities to Changpeipus and Megalosauripus, and a slightly smaller, slender and gracile type which is similar to Grallator, Eubrontes and Anchisauripus. In both morphotypes, digit III is the longest with a length between 11.4 and 33.6 cm. A single imprint shows prominent scratches, probably formed during slipping of the track maker. 相似文献
136.
137.
Quantifying groundwater–surface water interactions in a proglacial valley,Cordillera Blanca,Peru
下载免费PDF全文
![点击此处可从《水文研究》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Lauren D. Somers Ryan P. Gordon Jeffrey M. McKenzie Laura K. Lautz Oliver Wigmore AnneMarie Glose Robin Glas Caroline Aubry‐Wake Bryan Mark Michel Baraer Thomas Condom 《水文研究》2016,30(17):2915-2929
A myriad of downstream communities and industries rely on streams fed by both groundwater discharge and glacier meltwater draining the Cordillera Blanca, Northern Peruvian Andes, which contains the highest density of glaciers in the tropics. During the dry season, approximately half the discharge in the region's proglacial streams comes from groundwater. However, because of the remote and difficult access to the region, there are few field methods that are effective at the reach scale to identify the spatial distribution of groundwater discharge. An energy balance model, Rhodamine WT dye tracing, and high‐definition kite‐borne imagery were used to determine gross and net groundwater inputs to a 4‐km reach of the Quilcay River in Huascaran National Park, Peru. The HFLUX computer programme ( http://hydrology.syr.edu/hflux.html ) was used to simulate the Quilcay River's energy balance using stream temperature observations, meteorological measurements, and kite‐borne areal photography. Inference from the model indicates 29% of stream discharge at the reach outlet was contributed by groundwater discharge over the study section. Rhodamine WT dye tracing results, coupled with the energy balance, show that approximately 49% of stream water is exchanged (no net gain) with the subsurface as gross gains and losses. The results suggest that gross gains from groundwater are largest in a moraine subreach but because of large gross losses, net gains are larger in the meadow subreaches. These insights into pathways of groundwater–surface water interaction can be applied to improve hydrological modelling in proglacial catchments throughout South America. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
138.
Zaid Bahaeldeen Vollert Florian Gibmeier Jens Mengel Lena Stelzer Oliver Schneider Achim 《Acta Geotechnica》2023,18(2):865-876
Acta Geotechnica - The hole erosion test (HET) was developed to simulate piping erosion and to study the erosion parameters of cohesive soils. The erosion rate in the HET is evaluated by the... 相似文献
139.
Hernandez-Mora Marina Meseguer-Ruiz Oliver Karas Cyrus Lambert Fabrice 《Natural Hazards》2021,109(3):2153-2171
Natural Hazards - Human settlements in coastal areas are highly vulnerable to extreme events, especially in the Mediterranean area, which houses a large number of tourists during the summer and... 相似文献
140.