全文获取类型
收费全文 | 157篇 |
免费 | 16篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 10篇 |
大气科学 | 14篇 |
地球物理 | 33篇 |
地质学 | 94篇 |
海洋学 | 8篇 |
天文学 | 4篇 |
自然地理 | 15篇 |
出版年
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 6篇 |
2019年 | 2篇 |
2018年 | 11篇 |
2017年 | 7篇 |
2016年 | 12篇 |
2015年 | 11篇 |
2014年 | 5篇 |
2013年 | 15篇 |
2012年 | 8篇 |
2011年 | 17篇 |
2010年 | 5篇 |
2009年 | 4篇 |
2008年 | 7篇 |
2007年 | 9篇 |
2006年 | 6篇 |
2005年 | 6篇 |
2004年 | 3篇 |
2003年 | 4篇 |
2002年 | 8篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
排序方式: 共有178条查询结果,搜索用时 703 毫秒
31.
32.
Iron-hydroxide clogging of public supply wells receiving artificial recharge: near-well and in-well hydrological and hydrochemical observations 总被引:2,自引:2,他引:0
Diego A. Bustos Medina Gerard A. van den Berg Boris M. van Breukelen Maria Juhasz-Holterman Pieter J. Stuyfzand 《Hydrogeology Journal》2013,21(7):1393-1412
Clogging of water wells by iron-hydroxide incrustations due to mixing of anoxic and oxic groundwater is a common well-ageing problem. The relation between well operation (on and off), the spatial and temporal variations in hydrochemistry outside and inside a supply well, and the distribution of clogging iron-hydroxides were studied in an artificial recharge well field in the Netherlands. Camera inspection, high-resolution multi-level water sampling outside the well and detailed in-well pH/EC/O2 profiles revealed remarkable patterns. During pumping, the top of the upper well screen abstracted oxic filtrate, although the larger part of the in-well water column was anoxic. The column rapidly turned oxic after shutdown due to a downward short-circuiting of oxic water via the well. Within 15 d it became anoxic due to the slow advance of anoxic lake filtrate created by local changes in flow direction as the neighboring wells continued to pump. Severe clogging occurred where the oxic filtrate entered the well, while half-clogging of the upper well screen occurred due to less inflow of oxic filtrate on the lake side. Transport of iron flocs and bacterial slimes after shutdown seemed to clog the lower part of the well screen. Frequent on/off switching should be avoided in iron-clogged wells. 相似文献
33.
Identification of potential sites for aquifer storage and recovery (ASR) in coastal areas using ASR performance estimation methods 总被引:1,自引:0,他引:1
Koen G. Zuurbier Mark Bakker Willem Jan Zaadnoordijk Pieter J. Stuyfzand 《Hydrogeology Journal》2013,21(6):1373-1383
Performance of freshwater aquifer storage and recovery (ASR) systems in brackish or saline aquifers is negatively affected by lateral flow, density effects, and/or dispersive mixing, causing ambient groundwater to enter ASR wells during recovery. Two recently published ASR performance estimation methods are applied in a Dutch coastal area, characterized by brackish-to-saline groundwater and locally high lateral-flow velocities. ASR performance of existing systems in the study area show good agreement with the predicted performance using the two methods, provided that local vertical anisotropy ratios are limited (<3). Deviations between actual and predicted ASR performance may originate from simplifications in the conceptual model and uncertainties in the hydrogeological and hydrochemical input. As the estimation methods prove suitable to predict ASR performance, feasibility maps are generated for different scales of ASR to identify favorable ASR sites. Successful small-to-medium-scale ASR varies spatially in the study area, emphasizing the relevance of reliable a priori spatial mapping. 相似文献
34.
Results-based funding (RBF) is a governance concept that is rapidly becoming the mainstream paradigm for international collaborations in the environmental sector. While portrayed as a compromise solution between market-based mechanisms and unconditional donations, the implementation of RBF is revealing new conflicts and contradictions of its own. This paper explores the application of RBF for Reducing Emissions from Deforestation and Forest Degradation (REDD+) by describing the discursive conflicts between recipient (i.e., Brazil) and donor (i.e., Norway and Germany) countries of the Amazon Fund about what constitutes “results” or “performance.” Although all parties agree that the financial transfers to RBF should be based on past emission reductions in relation to a historical baseline, they hold clashing interpretations about temporal (i.e., past or future) and epistemological (i.e., how to measure) aspects of the results these payments are intended for. Firstly, while Brazil emphasizes that it deserves a reward of USD 21 billion for results achieved between 2006 and 2016, donor countries have indicated an interest in paying only for most recent results as a way to incentivize further reductions. Secondly, while all parties believe that Amazon Fund should support policies to reduce deforestation, donor countries have revealed concerns that the performance of the Amazon Fund projects in generating further reductions has not been measured in a rigorous manner. This suggests that donor countries may consider making changes to current RBF mechanisms or getting involved in new forms of finance. 相似文献
35.
Stela Cuna Elise Pendall John B. Miller Pieter P. Tans Ed Dlugokencky James W.C. White 《Applied Geochemistry》2008
The Danube Delta-Black Sea region of Romania is an important wetland, and this preliminary study evaluates the significance of this region as a source of atmospheric CH4. Measurements of the mixing ratio and δ13C in CH4 are reported from air and water samples collected at eight sites in the Danube Delta. High mixing ratios of CH4 were found in air (2500–14,000 ppb) and dissolved in water samples (∼1–10 μmol L−1), demonstrating that the Danube Delta is an important natural source of CH4. The intercepts on Keeling plots of about −62‰ show that the main source of CH4 in this region is microbial, probably resulting primarily from acetate fermentation. Atmospheric CH4 and CO data from the NOAA/ESRL (National Oceanic and Atmospheric Administration/Earth System Research Laboratory) were used to make a preliminary estimate of biogenic CH4 at the Black Sea sampling site at Constanta (BSC). These data were used to calculate ratios of CH4/CO in air samples, and using an assumed CH4/CO anthropogenic emissions ratio of 0.6, fossil fuel emissions at BSC were estimated. Biogenic CH4 emissions were then estimated by a simple mass balance approach. Keeling plots of well-mixed air from the BSC site suggested a stronger wetland source in summer and a stronger fossil fuel source in winter. 相似文献
36.
Mohamad?Asrul?MustafarEmail authorView authors OrcID profile Wim?J.?F.?Simons Felix?Tongkul Chalermchon?Satirapod Kamaludin?Mohd?Omar Pieter?N.?A.?M.?Visser 《Journal of Geodesy》2017,91(10):1241-1259
The existence of intra-plate deformation of the Sundaland platelet along its eastern edge in North Borneo, South-East Asia, makes it an interesting area that still is relatively understudied. In addition, the motion of the coastal area of North-West Borneo is directed toward a frontal fold-and-thrust belt and has been fueling a long debate on the possible geophysical sources behind it. At present this fold-and-thrust belt is not generating significant seismic activity and may also not be entirely active due to a decreasing shelfal extension from south to north. Two sets of Global Positioning System (GPS) data have been used in this study; the first covering a time period from 1999 until 2004 (ending just before the Giant Sumatra–Andaman earthquake) to determine the continuous Sundaland tectonic plate motion, and the second from 2009 until 2011 to investigate the current deformations of North Borneo. Both absolute and relative positioning methods were carried out to investigate horizontal and vertical displacements. Analysis of the GPS results indicates a clear trend of extension along coastal regions of Sarawak and Brunei in North Borneo. On the contrary strain rate tensors in Sabah reveal that only insignificant and inconsistent extension and compression occurs throughout North-West Borneo. Moreover, station velocities and rotation rate tensors on the northern part of North Borneo suggest a clockwise (micro-block) rotation. The first analysis of vertical displacements recorded by GPS in North-West Borneo points to low subsidence rates along the western coastal regions of Sabah and inconsistent trends between the Crocker and Trusmadi mountain ranges. These results have not been able to either confirm or reject the hypothesis that gravity sliding is the main driving force behind the local motions in North Borneo. The ongoing Sundaland–Philippine Sea plate convergence may also still play an active role in the present-day deformation (crustal shortening) in North Borneo and the possible clockwise rotation of the northern part of North Borneo as a micro-block. However, more observations need to be collected to determine if the northern part of North Borneo indeed is (slowly) moving independently. 相似文献
37.
Christian Beck Pieter Van Rensbergen Marc De Batist Fernand Berthier Serge Lallier Frédéric Manalt 《Journal of Paleolimnology》2001,25(2):149-161
The sedimentary fill of Lake Annecy (northwestern Alps) - related to the last glacial/post-glacial episode - was investigated through high resolution (sparker) and very high resolution (2.5 kHz) seismic-reflection surveys. A seismostratigraphic approach led to subdivision of a 150 m-thick pile (maximum thickness in axial part) into five units. Basal units (1 and 2) represent an imbrication of subglacial and glacio-lacustrine deposits, close to the grounding line of the glaciers' fronts (respectively at the northern and southern terminations of the lake). The first acoustically well-stratified unit (3) developed during a fast retreat of the glaciers fronts far from the lake basin, and a progradational alluvial regime, with abundant underflows, in a lake larger than the present one. Unit 4 represents the progressive decrease of this clastic input mixed with the progressive development of in situ bio-induced production. As in many other alpine lakes, a topmost unit (5), relatively thin (about 8-10 m) and with a conspicuous drape configuration, is the signature of the Holocene interglacial climatic conditions with a sedimentation rate of about 1 mm/yr. On the lacustrine basin slopes, slumps and debris flow occurred mainly within Unit 3; they may be due to, either climate-induced high rate terrigenous sedimentation, or/and to a period of increased seismo-tectonic activity. 相似文献
38.
Pieter Glasbergen 《Global Environmental Change》2010,20(1):130-141
Global action networks (GANs) are civil society initiated multi-stakeholder arrangements that aim to fulfill a leadership role for systemic change in global governance for sustainable development. The paper develops a network approach to study some of these GANs as motivators of global collective action and investigates how in their interaction processes the actors involved create the organizational capacity for collective change. Based on a variety of case studies, the paper highlights crucial factors determining the performance of GANs; among them the characteristics of the issue field and the development stage of the GAN. The analysis also shows how GANs play two crucial roles, sometimes in combination, sometimes successively. These are labelled as the broker and entrepreneur role. The paper concludes with some conditions for collective action that are underexposed in collective action theory. 相似文献
39.
Jinglang Feng Ron Noomen Xiyun Hou Pieter Visser Jianping Yuan 《Celestial Mechanics and Dynamical Astronomy》2017,127(1):67-93
Using a gravitational field truncated at the 4th degree and order, the 1:1 ground-track resonance is studied. To address the main properties of this resonance, a 1-degree of freedom (1-DOF) system is firstly studied. Equilibrium points (EPs), stability and resonance width are obtained. Different from previous studies, the inclusion of non-spherical terms higher than degree and order 2 introduces new phenomena. For a further study about this resonance, a 2-DOF model which includes a main resonance term (the 1-DOF system) and a perturbing resonance term is studied. With the aid of Poincaré sections, the generation of chaos in the phase space is studied in detail by addressing the overlap process of these two resonances with arbitrary combinations of eccentricity (e) and inclination (i). Retrograde orbits, near circular orbits and near polar orbits are found to have better stability against the perturbation of the second resonance. The situations of complete chaos are estimated in the \(e-i\) plane. By applying the maximum Lyapunov Characteristic Exponent (LCE), chaos is characterized quantitatively and similar conclusions can be achieved. This study is applied to three asteroids 1996 HW1, Vesta and Betulia, but the conclusions are not restricted to them. 相似文献
40.
Pieter M Grootes Eric J Steig Minze Stuiver Edwin D Waddington David L Morse Marie-Jose Nadeau 《Quaternary Research》2001,56(3)
The 18O/16O profile of a 554-m long ice core through Taylor Dome, Antarctica, shows the climate variability of the last glacial–interglacial cycle in detail and extends at least another full cycle. Taylor Dome shares the main features of the Vostok record, including the early climatic optimum with later cool phase of the last interglacial period in Antarctica. Taylor Dome δ18O fluctuations are more abrupt and larger than those at Vostok and Byrd Station, although still less pronounced than those of the Greenland GISP2 and GRIP records. The influence of the Atlantic thermohaline circulation on regional ocean heat transport explains the partly “North Atlantic” character of this Antarctic record. Under full glacial climate (marine isotope stage 4, late stage 3, and stage 2), this marine influence diminished and Taylor Dome became more like Vostok. Varying degrees of marine influence produce climate heterogeneity within Antarctica, which may account for conflicting evidence regarding the relative phasing of Northern and Southern Hemisphere climate change. 相似文献