全文获取类型
收费全文 | 443篇 |
免费 | 32篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 13篇 |
大气科学 | 29篇 |
地球物理 | 115篇 |
地质学 | 197篇 |
海洋学 | 44篇 |
天文学 | 56篇 |
综合类 | 2篇 |
自然地理 | 23篇 |
出版年
2022年 | 8篇 |
2021年 | 12篇 |
2020年 | 13篇 |
2019年 | 4篇 |
2018年 | 16篇 |
2017年 | 26篇 |
2016年 | 25篇 |
2015年 | 19篇 |
2014年 | 37篇 |
2013年 | 45篇 |
2012年 | 30篇 |
2011年 | 36篇 |
2010年 | 34篇 |
2009年 | 40篇 |
2008年 | 20篇 |
2007年 | 7篇 |
2006年 | 16篇 |
2005年 | 15篇 |
2004年 | 10篇 |
2003年 | 6篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 6篇 |
1999年 | 1篇 |
1998年 | 7篇 |
1997年 | 6篇 |
1995年 | 2篇 |
1994年 | 8篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 4篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1968年 | 1篇 |
1962年 | 1篇 |
1960年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有479条查询结果,搜索用时 62 毫秒
441.
Galliski Miguel Ángel Márquez-Zavalía María Florencia Škoda Radek Novák Milan Čopjaková Renata Pagano Diego Sebastián 《Mineralogy and Petrology》2019,113(5):687-701
Mineralogy and Petrology - An assemblage of tantalite-(Mn), tantalian rutile, tapiolite-(Fe), titanowodginite, ferrotitanowodginite, and hydroxycalciomicrolite occurs in the Nancy granitic... 相似文献
442.
Áslaug Geirsdóttir Gifford H. Miller Thorvaldur Thordarson Kristín B. Ólafsdóttir 《Journal of Paleolimnology》2009,41(1):95-115
The sediment fill of Haukadalsvatn, a lake in northwest Iceland, preserves a record of environmental change since deglaciation,
13 ka ago. The rapid sedimentation rate over the past 2 ka (ca. 4 m ka−1) provides a high-resolution archive of late Holocene environmental change. Physical and chemical environmental proxies extracted
from cores from the Haukadalsvatn sediment fill provide a reconstruction of sub-decadal-scale climate variability in Iceland
over the past 2 ka. Over this interval biogenic silica (BSi) reflects warm April–May temperatures, whereas total organic carbon
(TOC) peaks represent an increased flux of carbon to the lake from eolian-derived soil erosion following periods of cold summers
accompanied by dry, windy winters. The proxy-based temperature reconstructions show a broad interval of warmth through Medieval
times, but this warmth is punctuated by multi-decadal cold intervals. The transition into the Little Ice Age occurred in two
steps, with initial summer cooling 1250–1300 AD, and a more severe drop in summer temperatures between 1450 and 1500 AD; both
are periods of severe explosive volcanism. Multi-decadal patterns of cold and warm conditions have some characteristics of
a North Atlantic Oscillation (NAO)-like signal, but instrumental records and proxy-based reconstructions of the NAO index
contain little power in the frequencies most strongly expressed in our data set. Although severe soil erosion in Iceland is
frequently equated with settlement, our reconstructions indicate that soil erosion began several centuries before settlement,
whereas for several centuries after settlement, when summer temperatures were relatively high, there was little or no soil
erosion. Only during the transition into and during the Little Ice Age did soil erosion become a major feature of the record.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
相似文献
Kristín B. ólafsdóttirEmail: |
443.
This study develops a lattice Boltzmann method (LBM) with a two-relaxation-time collision operator (LTRT) to solve saltwater intrusion problems. A directional-speed-of-sound (DSS) technique is introduced to take into account the hydraulic conductivity heterogeneity and discontinuity, as well as the velocity-dependent dispersion coefficient. The forcing terms in the LTRT model are customized in order to recover the density-dependent groundwater flow and mass transport equations. Using the LTRT with the squared DSS achieves at least second-order accuracy. The LTRT results are verified with Henry’s analytical solution as well as compared with several numerical examples and modified Henry problems that consider heterogeneous hydraulic conductivity and velocity-dependent dispersion. The numerical results show good agreement with the Henry analytical solution and with the numerical solutions obtained by other numerical methods. 相似文献
444.
445.
The use of benthic indicators in Europe: from the Water Framework Directive to the Marine Strategy Framework Directive 总被引:1,自引:0,他引:1
Van Hoey G Borja A Birchenough S Buhl-Mortensen L Degraer S Fleischer D Kerckhof F Magni P Muxika I Reiss H Schröder A Zettler ML 《Marine pollution bulletin》2010,60(12):2187-2196
The Water Framework Directive (WFD) and the Marine Strategy Framework Directive (MSFD) are the European umbrella regulations for water systems. It is a challenge for the scientific community to translate the principles of these directives into realistic and accurate approaches. The aim of this paper, conducted by the Benthos Ecology Working Group of ICES, is to describe how the principles have been translated, which were the challenges and best way forward. We have tackled the following principles: the ecosystem-based approach, the development of benthic indicators, the definition of ‘pristine’ or sustainable conditions, the detection of pressures and the development of monitoring programs. We concluded that testing and integrating the different approaches was facilitated during the WFD process, which led to further insights and improvements, which the MSFD can rely upon. Expert involvement in the entire implementation process proved to be of vital importance. 相似文献
446.
Heliana Teixeira Ángel Borja J. Ananda Ranasinghe Daniel M. Dauer Steven Degraer Antoine Grémare Roberto J. Llansó João C. Marques Anna Occhipinti-Ambrogi Rafael Sardá Ronald G. Velarde 《Marine pollution bulletin》2010,60(4):589-600
Benthic indices are typically developed independently by habitat, making their incorporation into large geographic scale assessments potentially problematic because of scaling inequities. A potential solution is to establish common scaling using expert best professional judgment (BPJ). To test if experts from different geographies agree on condition assessment, sixteen experts from four regions in USA and Europe were provided species-abundance data for twelve sites per region. They ranked samples from best to worst condition and classified samples into four condition (quality) categories. Site rankings were highly correlated among experts, regardless of whether they were assessing samples from their home region. There was also good agreement on condition category, though agreement was better for samples at extremes of the disturbance gradient. The absence of regional bias suggests that expert judgment is a viable means for establishing a uniform scale to calibrate indices consistently across geographic regions. 相似文献
447.
Ana Da Silva Vincenzo Costanzo-Álvarez Nuri Hurtado Milagrosa Aldana Germán Bayona Oswaldo Guzmán Diego López-Rodríguez 《Studia Geophysica et Geodaetica》2010,54(4):607-631
In this work we have assessed the hybrid algorithm of NeuroFuzzy logic (NFL), to establish a correlation between global climatic
changes (benthic foraminiferal δ18O data), experimental S-ratio (factor characterizing stability of remanent magnetization) and magnetic susceptibility (κ).
Magnetic proxies have been measured in 44 samples of the Colombian stratigraphic well Saltarín 1A (distal Llanos foreland
basin). κ and Sratios were linked to global δ18O data assuming a constant accumulation rate for a 305 meters thick stratigraphic interval flanked by the two palynological
age constrains available. This interval encompasses, from top to base, the bottom of the Guayabo formation, the León, and
the upper unit of the Carbonera formations (lower to middle Miocene). The best inference is accomplished applying a Takagi-Sugeno-Kan
(TSK) fuzzy model with four fuzzy rules and the δ18O, S-ratios and κ data used in a linear form to train the system. These results are interpreted as the outcome of a significant
influence of global climatic changes upon magnetic proxies. A stronger correlation is perhaps prevented by the likely influence
of local and regional tectonic events and climatic changes that could have affected the distal segment of the Colombian Llanos
foreland basin during Miocene times. We argue that late diagenesis of primary magnetic minerals and the assumption of a constant
accumulation rate might have a minor influence on these results. 相似文献
448.
Hammad Tariq JANJUHAH José Antonio GáMEZ VINTANED Ahmed Mohamed AhmedSALIM Ibrahima FAYE Mumtaz Muhammad SHAH Deva Prasad GHOSH 《《地质学报》英文版》2017,91(5):1778-1796
The Luconia Province – offshore Sarawak – is a key geological unit for understanding the distribution of hydrocarbon resources in Malaysia. Nevertheless, little effort has been made to address the palaeoenvironmental characteristics of the Tertiary carbonates in the key sector of Central Luconia. We study the sedimentology and petrography of core samples from a well in Central Luconia, for which thirteen microfacies have been identified reflecting different depositional settings. This is the first microfacies scheme elaborated for Luconian carbonates. Lithofacies and microfacies distribution are compatible with deposition in a reef complex, originating around a framework reef, within the euphotic zone. Sediments were deposited in environments of backreef, reef crest, and forereef. The fair weather wave base is marked by the presence of coralline red algae, foraminifera, decreasing degree of bioclast fragmentation and other microfacies features. As a result, a depositional-environmental model is constructed, depicting a reef complex built around a framework reef developed on the margin of an isolated platform. In addition, an innovative, preliminary time series analysis of facies, microfacies and depositional environment data reveal the existence of seasonal cycles in the stacking patterns of facies and microfacies. 相似文献
449.
Vincenzo Costanzo-Álvarez Rosa Devesa-Rey Milagrosa Aldana María Teresa Barral Diego López-Rodríguez Belkys Andrade 《Environmental Earth Sciences》2017,76(13):454
A study of surface sediments from the Anllóns riverbed (northwestern Spain) was conducted to assess the use of their magnetic properties as proxies of recent trace element contamination (i.e., As, Zn, Pb, Cr, Ni and Cu). Thermomagnetic curves, hysteresis parameters, specific magnetic susceptibility χ, frequency-dependent magnetic susceptibility κ FD%, magnetic remanence and saturation isothermal remanent magnetization ratios (i.e., S and SIRM/χ) reveal the presence of mostly fine-grained magnetite and maghemite in these samples. The Tomlinson Pollution Load Index (PLI), as well as the magnetic parameters χ, κ FD%, SIRM/χ and S-ratios, vary more or less in agreement to each other when they are sequentially arranged throughout a 30-km-long transect that goes from the town of Carballo to the river mouth in Ponteceso. From that profile, it is possible to identify an anomaly of χ that lies between two small peaks of the PLI and seems to define a contaminated area probably linked to a diffuse low-impact source of pollution. There is also a conspicuous peak of the PLI that is likely associated to a nearby gold mine. The variations of the κ FD%’s along the transect are the ones that best reflect the changes in the PLI values, regardless of the level of contamination. This result suggests that adsorption is the main mechanism of trace elements removal by Fe oxides in these samples. Direct signal analyses, used to decompose the isothermal remanent magnetization curves, reveal the presence of four magnetic fractions, with varying relative concentrations all over the profile, namely single-domain magnetite, close to the superparamagnetic threshold (SD/SP) and/or maghemite (\(\log B_{1/2}\) ca 1.2), single-domain magnetite (\(\log B_{1/2}\) ca 2), hematite (\(\log B_{1/2}\) ca 2.5) and goethite (\(\log B_{1/2}\) ca 3.5). Integrating all the available information, it was sketched out a likely sequence of events that included magnetic minerals neoformation in parent soils, their subsequent chemical transformations and the contamination episodes that affected the region. 相似文献
450.
G. Asencio–Cortés S. Scitovski R. Scitovski F. Martínez–Álvarez 《Earth Science Informatics》2017,10(3):303-320
The prediction of earthquakes is a task of utmost difficulty that has been addressed in many different ways. However, an initial definition of the area of interest is needed, with adequate catalogs. In this work, different seismogenic zones proposals in the Republic of Croatia are studied, in terms of predictability. Such zones have been characterized with widely used seismicity parameters. Later, studies based on training and test sets properties as well as the quality of the data involved are carried out. The studies presented in this work analyze the prediction performance across the earthquake magnitude time series of the target seismogenic zones. Results show that specific prediction techniques could be used in some zones to improve earthquake magnitude prediction. 相似文献