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排序方式: 共有61条查询结果,搜索用时 19 毫秒
51.
Thach Ngoc Nguyen Canh Xuan Pham Huy Quoc Nguyen Toan Ngo Bao Dang 《Singapore journal of tropical geography》2019,40(2):312-333
Hoang Su Phi is a mountainous district in Ha Giang province, Vietnam. When the rainy season arrives in these parts, flash floods (besides landslides), frequently occur in many areas, seriously affecting the socio‐economic condition of the district. Therefore, in this paper, we have developed an early warning system for flash floods, established based on a geomorphological and hydrological approach. The basic principle underlying this system is the fact that flash floods will often occur where there is high potential risk with sufficient rainfall. In the model, eight parameters of the basin were used to build a potential flash flood map. Using the spatial processing module in an open source software, early predictions from automatic weather stations were interpolated and processed online to produce a potential risk map. Depending on the threshold of precipitation values, the results determined locations where flash flood may occur at various flash flood risk indices (FFRI). The system may be applied to support provision of early flash flood warning up to 1?6 days in advance in the district, allowing the local government ample time to make appropriate decisions on the prevention and/or mitigation of damages caused by flash flood hazards. 相似文献
52.
The Lateglacial and Holocene in Central Europe: a multi‐proxy environmental record from the Bohemian Forest,Czech Republic
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Klára Vočadlová Libor Petr Pavla Žáčková Marek Křížek Lenka Křížová Simon M. Hutchinson Miroslav Šobr 《Boreas: An International Journal of Quaternary Research》2015,44(4):769-784
The Hercynian mountain ranges were islands of mountain glaciation and alpine tundra in a Central European ice‐free corridor during the Late Pleistocene. Today they are notable areas of glacial landforms, alpine‐forest free areas, peatlands and woodlands. However, our knowledge of the Lateglacial and early Holocene environmental changes in this region is limited. We present a new multi‐proxy reconstruction of a mid‐altitude environment in the Bohemian Forest spanning this period. A core (5.2 m length) in the ?erné Lake cirque (1028 m a.s.l.) was subjected to lithological, geochemical, pollen and macrofossil analysis supplemented by two optically stimulated luminescence (OSL) and 10 AMS radiocarbon dates. We determined the impact of regional and supraregional climate changes on the environment. The two most significant changes in sedimentation during the Lateglacial (17.6 and 15.8–15.5 cal. ka BP) were synchronous with regional glacial chronostratigraphy. Unlike Central European mountain ranges, in the Bohemian Forest the Younger Dryas was not coincident with glacier re‐advance, but was a dry, cold episode with low lake levels, which prevailed until the early Preboreal. Plant macrofossils indicate local establishment of Betula nana and Betula pendula/pubescens at 15.4–13.4 cal. ka BP. Comparison with Holocene records from Central Europe shows a similar immigration history of vegetation at mid and higher altitudes. The tree line exceeded an altitude of ~1000 m a.s.l. around 10.5 cal. ka BP and coincided with rapid geochemical changes in the sediment. The 8.2 ka BP event did not have any response in the sedimentary record, but corresponded to stabilization of the Picea abies population and expansion of Fagus. Fagus colonized the Bohemian Forest earlier than other Hercynian mid‐mountains, but never predominated in the composition of the forest at higher elevations. Abies alba was the last tree species that immigrated to the study area. 相似文献
53.
Landslide susceptibility assessment using SVM machine learning algorithm 总被引:10,自引:0,他引:10
This paper introduces the current machine learning approach to solving spatial modeling problems in the domain of landslide susceptibility assessment. The latter is introduced as a classification problem, having multiple (geological, morphological, environmental etc.) attributes and one referent landslide inventory map from which to devise the classification rules. Three different machine learning algorithms were compared: Support Vector Machines, Decision Trees and Logistic Regression. A specific area of the Fruška Gora Mountain (Serbia) was selected to perform the entire modeling procedure, from attribute and referent data preparation/processing, through the classifiers' implementation to the evaluation, carried out in terms of the model's performance and agreement with the referent data. The experiments showed that Support Vector Machines outperformed the other proposed methods, and hence this algorithm was selected as the model of choice to be compared with a common knowledge-driven method – the Analytical Hierarchy Process – to create a landslide susceptibility map of the relevant area. The SVM classifier outperformed the AHP approach in all evaluation metrics (κ index, area under ROC curve and false positive rate in stable ground class). 相似文献
54.
We present the first ab initio simulations of the low-pressure phase of ammonia dihydrate (NH3 · 2H2O), ADH I, a likely constituent of many volatile-rich solid bodies in the outer Solar System (e.g., Saturn’s moons). Ordered monoclinic (space group P21) and orthorhombic (space group P212121) variants of the experimentally observed cubic cell (space group P213) may be constructed, with fully ordered water molecule orientations that obey the ice rules. Our calculations show that the most stable structure at 0 K is orthorhombic (P212121), the monoclinic variants (P21) being energetically disfavored. We provisionally call this ordered orthorhombic phase ADH III. The, as-yet-unmeasured, bulk modulus, K0, is predicted to be 10.67−0.44+0.56 GPa at 0 K. Our results are also combined with literature data to arrive at a revised coefficient of volume thermal expansion, αv = 2.81 × 10−7 T1.39 (from 0-176 K), with the density at 0 K, ρ0 = 991.7(39) kg m−3. We also present a case, based on literature data, that argues for a gradual transformation from a paraelectrically disordered cubic structure (P213) to the proposed antiferroelectrically ordered orthorhombic structure (P212121) around 130-150 K (cf. ice III → IX), a temperature regime that applies to the surfaces and interiors of many medium-sized (radii ∼500-700 km) icy bodies. 相似文献
55.
Vít Voženílek 《GeoJournal》1994,32(3):241-245
The territory of the Czech Republic has been investigated by geographers for many decades. The Moravian Gate situated in the eastern part of the Czech Republic, became a place of high human concentration due to its geographical location. Geomorphological research in the Czech republic has reached an impressive level in the field of both the morphostructure of the whole territory and the extent of glaciation. The article treats the relationship between the morphostructure and the extent of glaciation in a geographically complicated region. Both of these have been investigated separately. The synthesis of all results brings new knowledge and suggestions for future research in the region close to the main European watershed. The paper is completed on the basis of the author's research including the complex geomorphological analysis, especially morphostructural and morfosculptural analysis, the investigation of the features and genesis of georelief, the digital elevation model of studied area, the detailed geomorphological mapping in 1:10.000 scale and the compilation of denudation chronology. 相似文献
56.
Dr. Maren Voß 《Ocean Dynamics》1991,44(5-6):283-288
Zusammenfassung Bereits im Oktober 1973 wurde von der EG ein Aktionsprogramm für den Umweltschutz verabschiedet, in dem die Definition von Qualitätszielen gefordert wird. Danach sollen Qualitätsziele für den Schutz des Menschen gegen Umweltverschmutzung, aber auch für den Schutz der Umwelt an sich formuliert werden. Die Vorstellungen bezogen das Meerwasser zwar ausdrücklich mit ein, waren jedoch stark funktionsbezogen (Badewasser, Fischzucht). 1986 fanden Qualitätsziele in die Leitlinien Umweltvorsorge Eingang. Die Dritte Internationale Nordseeschutzkonferenz 1991 forderte, Qualitätsziele international zu entwickeln. Im selben Jahr erhielt das Nationalparkamt vom Schleswig-Holsteinischen Umweltministerium den Auftrag, ein Diskussionspapier zu erarbeiten. Dieses Papier liegt inzwischen vor. Es beschreibt ökologische Schäden und schlägt auch Parameter für Qualitätsziele vor.In der aktuellen Diskussion wird z. T. bestritten, daß die Beschreibung ökologischer Ziele von Nutzen sein könnte. Sinnvolles Handeln zum Schutz der Umwelt ist aber nur möglich, wenn Klarheit über die Ziele besteht. Auch in der Umweltpolitik reichen vage Formulierungen nicht aus, zumal dann allzu leicht eine breite, aber folglose Zustimmung erfolgt. Präzise definierte Ziele ermöglichen dagegen eine Kontrolle über den Erfolg von eingeleiteten Maßnahmen.Aus diesen Gründen müssen ökologische Qualitätsziele für den Natur- und Umweltschutz definiert werden. Die dafür benötigten Begriffe sind eindeutig festzulegen und zu verwenden (z. B. Qualitätsstandards, Grenzwerte, Richtwerte). Erst dann ist es möglich, die Ziele von den anzuwendenden Methoden zu unterscheiden, die in der bisherigen Diskussion ständig verwechselt werden. Ohne Beteiligung der Naturwissenschaftler können Qualitätsziele nicht verständlich und präzise formuliert werden.
Veröffentlichung Nr. 32 des Projektes Ökosystemforschung Wattenmeer 相似文献
For and against ecological quality objectives for the North Sea-for
Summary In October 1973 the EC approved environmental protection measures in which a demand was made for a definition of ecological quality objectives. These were to be formulated to ensure that humans were protected against environmental pollution, but aims to protect the environment itself were also to be drawn up. Sea water was included in the programme, but suggestions were strongly oriented towards its various uses (bathing, fish farming). Quality aims were included in the 1986 Leitlinien Umweltvorsorge (Guidelines for environmental precautions). The 3rd International North Sea conference in 1991 requested that ecological quality objectives should be developed internationally. Also in 1991, the Ministry of the Environment in Schleswig-Holstein instructed the Nationalpark agency to draw up a discussion document which has now been presented. It describes ecolgical damage and suggests parameters for ecological quality objectives.In the current discussion, it is partly disputed that describing ecological aims could be useful. But sensible action to protect the environment is only possible if there is no confusion about the aims. In ecological policy, too, vague formulations are not sufficient, particularly if what follows is broad but ineffective agreement. Precisely defined aims, on the other hand, mean that the success of measures taken can be checked.It is for these reasons that ecological quality objectives must be defined for conservation purposes. The terms to be used must be fixed and used unambiguously (e. g. quality standards, limit values, guide values). Only then it will be possible to distinguish between aims and the methods which in previous discussions have always been confused. Ecological quality objectives cannot be formulated intelligibly and precisely without the pariticipation of scientists.
Veröffentlichung Nr. 32 des Projektes Ökosystemforschung Wattenmeer 相似文献
57.
M. Latif K. Sperber J. Arblaster P. Braconnot D. Chen A. Colman U. Cubasch C. Cooper P. Delecluse D. Dewitt L. Fairhead G. Flato T. Hogan M. Ji M. Kimoto A. Kitoh T. Knutson H. Le Treut T. Li S. Manabe O. Marti C. Mechoso G. Meehl S. Power E. Roeckner J. Sirven L. Terray A. Vintzileos R. Voß B. Wang W. Washington I. Yoshikawa J. Yu S. Zebiak 《Climate Dynamics》2001,18(3-4):255-276
An ensemble of twenty four coupled ocean-atmosphere models has been compared with respect to their performance in the tropical Pacific. The coupled models span a large portion of the parameter space and differ in many respects. The intercomparison includes TOGA (Tropical Ocean Global Atmosphere)-type models consisting of high-resolution tropical ocean models and coarse-resolution global atmosphere models, coarse-resolution global coupled models, and a few global coupled models with high resolution in the equatorial region in their ocean components. The performance of the annual mean state, the seasonal cycle and the interannual variability are investigated. The primary quantity analysed is sea surface temperature (SST). Additionally, the evolution of interannual heat content variations in the tropical Pacific and the relationship between the interannual SST variations in the equatorial Pacific to fluctuations in the strength of the Indian summer monsoon are investigated. The results can be summarised as follows: almost all models (even those employing flux corrections) still have problems in simulating the SST climatology, although some improvements are found relative to earlier intercomparison studies. Only a few of the coupled models simulate the El Niño/Southern Oscillation (ENSO) in terms of gross equatorial SST anomalies realistically. In particular, many models overestimate the variability in the western equatorial Pacific and underestimate the SST variability in the east. The evolution of interannual heat content variations is similar to that observed in almost all models. Finally, the majority of the models show a strong connection between ENSO and the strength of the Indian summer monsoon. 相似文献
58.
William Berelson Frank Corsetti Brad Johnson Toan Vo Chris Der 《Journal of Paleolimnology》2009,42(1):25-36
Closed-basin alkaline lakes record climate change particularly well because they generally contain a sedimentary record that
is high in carbonate mineral content from which climate proxies can be determined. Various approaches are used to estimate
paleo-lake level and volume (δ18O, dating of “shoreline” tufas, biotic proxies, etc.), yet all carry certain caveats that limit their usefulness. Ultimately,
the relationship between the chemistry of the lake, the volume of the lake, and the response of the proxy will determine how
well a proxy serves a paleolimnologic purpose. Here, we discuss the use of carbonate-associated sulfate (CAS), the sulfate
contained within the lattice of carbonate minerals that precipitate in lake water, as a proxy for lake water chemistry and
by extension, lake volume. Walker Lake, an alkaline closed-basin lake in western Nevada, has experienced a well-documented
lake-level decline since 1880 and provides a test case for CAS as a lake-level proxy. By extracting the CAS from sedimentary
carbonate and tufas that have been age dated, we can relate these values to lake sulfate content based on historical or other
proxy data. We confirm that CAS tracks lake sulfate. Our study of sedimentary carbonates demonstrates that CAS is a linear
function of lake sulfate through a range of 10–25 mM, which corresponds to a change in lake level of 30 m. As confirmation
of the CAS technique, we analyzed a stromatolitic tufa dated using AMS 14C. The CAS trend in the stromatolite suggested that it grew during a lake-level decline, a result consistent with other proxy
data. Finally, laboratory experiments were conducted that demonstrate CAS is monotonically correlated with sulfate concentration
and that precipitation kinetics are not likely a major control on CAS in alkaline lakes, but that ionic strength of the solution
exerts a strong control on CAS. 相似文献
59.
ShuangHe Shen ShenBin Yang BingBai Li BingXiang Tan ZengYuan Li Thuy Le Toan 《中国科学D辑(英文版)》2009,52(8):1183-1194
Information on rice growing areas and rice production is critical for most rice growing countries to make state and economic
policies. However, the areas where rice crop is cultivated are often cloudy and rainy, which entails the use of radar remote
sensing data for rice monitoring. In this paper, a practical scheme to integrate multi-temporal and multi-polarization ENVISAT
ASAR data into rice crop model for regional rice yield estimation has been presented. To achieve this, rice distribution information
should be obtained first by rice mapping method to retrieve rice fields from ASAR images, and then an assimilation method
is applied to use the observed multi-temporal rice backscattering coefficients which are grouped for each rice pixel to re-initialize
ORYZA2000 to predict rice yield. The assimilation method re-initializes the model with optimal input parameters, allowing
a better temporal agreement between the rice backscattering coefficients retrieved from ASAR data and the rice backscattering
coefficients simulated by a coupled model, i.e., the combination of ORYZA2000 and a semi-empirical rice backscatter model
through LAI. The SCE-UA optimization algorithm is employed to determine the optimal set of input parameters. After the re-initialization,
rice yield for each rice pixel is calculated, and the yield map over the area of interest is produced. The scheme was validated
over Xinghua study area located in the middle of Jiangsu Province of China by using the data set of an experimental campaign
carried out during the 2006 rice season. The result shows that the obtained rice yield map generally overestimates the actual
rice production by 13% on average and with a root mean square error of approximately 1133 kg/ha on validation sites, but the
tendency of rice growth status and spatial variation of the rice yield are well predicted and highly consistent with the actual
production variation.
Supported by the ESA-NRSCC Dragon Cooperation Program (), the Project for Jiangsu Graduate in Scientific Research and Innovation (No. CX07B_048z), and the Special Program for Scientific
Research in Public Welfare Meteorological Services (No. GYHY200806008) 相似文献
60.