全文获取类型
收费全文 | 352篇 |
免费 | 6篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 68篇 |
地球物理 | 51篇 |
地质学 | 105篇 |
海洋学 | 18篇 |
天文学 | 66篇 |
综合类 | 4篇 |
自然地理 | 48篇 |
出版年
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 4篇 |
2018年 | 8篇 |
2017年 | 8篇 |
2016年 | 5篇 |
2015年 | 3篇 |
2014年 | 6篇 |
2013年 | 12篇 |
2012年 | 6篇 |
2011年 | 15篇 |
2010年 | 7篇 |
2009年 | 13篇 |
2008年 | 7篇 |
2007年 | 12篇 |
2006年 | 12篇 |
2005年 | 10篇 |
2004年 | 17篇 |
2003年 | 10篇 |
2002年 | 7篇 |
2001年 | 12篇 |
2000年 | 10篇 |
1999年 | 9篇 |
1998年 | 6篇 |
1997年 | 8篇 |
1996年 | 10篇 |
1995年 | 9篇 |
1994年 | 15篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 9篇 |
1990年 | 8篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 9篇 |
1983年 | 7篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1972年 | 2篇 |
1971年 | 9篇 |
排序方式: 共有362条查询结果,搜索用时 31 毫秒
221.
利用俄罗斯堪察加地区1995~2005年的GPS观测数据,研究了该区现今地壳水平运动速度场特征.在球坐标系中解算了各应变率分量,分析了应变率场的空间分布特征,并与地震学和地质学研究结果进行了综合对比分析.结果表明,堪察加半岛北部的微板块边界并不明显,堪察加南部测站运动速度大于中部和北部地区,愈靠近东部板块汇聚区,测站速度越大.从东海岸到西海岸,测站水平速度存在明显的梯度衰减特征,水平运动方向与太平洋板块向西北的俯冲方向基本一致.各应变率分量具有东部海岸大于中部和西海岸、从东至西呈梯度衰减的特点.堪察加大部分地区处于EW和NS向压缩状态,局部存在拉张.面应变率结果显示绝大部分为压缩区;刚性转动结果表明大部分地区表现为顺时针转动,北部地区和南端顺时针旋转性明显.东部有效应变率明显大于西部地区,东西向梯度衰减关系明显.主压应变率明显大于主张应变率,特别是在东海岸地区.主压应变率方向与中等以上地震的主压应力轴在水平方向的投影方向基本一致.地壳变形场在空间分布上的不一致性主要与太平洋板块在堪察加半岛东南侧的俯冲深度、俯冲方位角、俯冲倾角和俯冲带的耦合强度有关. 相似文献
222.
Jayde N. Hirniak Eugene I. Smith Racheal Johnsen Minghua Ren Jamie Hodgkins Caley Orr Fabio Negrino Julien Riel-Salvatore Shelby Fitch Christopher E. Miller Andrea Zerboni Guido S. Mariani Jacob A. Harris Claudine Gravel-Miguel David Strait Marco Peresani Stefano Benazzi Curtis W. Marean 《第四纪科学杂志》2020,35(1-2):199-212
Chemical characterization of cryptotephra is critical for temporally linking archaeological sites. Here, we describe cryptotephra investigations of two Middle–Upper Paleolithic sites from north-west Italy, Arma Veirana and Riparo Bombrini. Cryptotephra are present as small (<100 µm) rhyolitic glass shards at both sites, with geochemical signatures rare for volcanoes in the Mediterranean region. Two chemically distinct shard populations are present at Arma Veirana (P1 and P2). P1 is a high silica rhyolite (>75 wt.%) with low FeO (<1 wt.%) and a K2O/Na2O > 1 and P2 is also a high silica rhyolite (>75 wt.%) but with higher FeO (2.33–2.65 wt.%). Shards at Riparo Bombrini (P3) are of the same composition as P1 shards at Arma Veirana, providing a distinct link between deposits at both sites. Geochemical characteristics suggest three possible sources for P1 and P3: eruptions from Lipari Island (56–37.7 ka) in Italy, the Acigöl volcanic field (200–20 ka) in Turkey and the Miocene Kirka-Phrigian caldera (18 Ma) in Turkey. Eruptions from Lipari Island are the most likely source for P1,3 cryptotephra. This study highlights how cryptotephra can benefit archaeology, by providing a direct link between Arma Veirana and Riparo Bombrini as well as other deposits throughout the Mediterranean. 相似文献
223.
A comprehensive model for the prediction of concentration fluctuations in plumes dispersing in the complex and highly disturbed
wind flows in an urban environment is formulated. The mean flow and turbulence fields in the urban area are obtained using
a Reynolds-averaged Navier-Stokes (RANS) flow model, while the standard k-ϵ turbulence model (k is the turbulence kinetic energy and ϵ is the viscous dissipation rate) is used to close the model. The RANS model provides a specification of the velocity statistics
of the highly disturbed wind flow in the urban area, required for the solution of the transport equations for the mean concentration
and concentration variance (both of which are formulated in the Eulerian framework). A physically-based formulation for the scalar dissipation time
scale t
d
, required for the closure of the transport equation for , is presented. This formulation relates t
d
to an inner time scale corresponding to “internal” concentration fluctuation associated with relative dispersion, rather
than an outer time scale associated with the entire portion of the fluctuation spectrum. The two lowest-order moments of concentration
( and ) are used to determine the parameters of a pre-chosen functional form for the concentration probability density function
(clipped-gamma distribution). Results of detailed comparisons between a water-channel experiment of flow and dispersion in
an idealized obstacle array and the model predictions for mean flow, turbulence kinetic energy, mean concentration, concentration
variance, and concentration probability density function are presented. 相似文献
224.
En-Ping Huang Eugene Huang Shu-Cheng Yu Yen-Hua Chen Jiann-Shing Lee Jiann-Neng Fang 《Physics and Chemistry of Minerals》2010,37(9):593-600
Kerogen samples were treated at temperatures and pressures up to 25–600°C and ~9 GPa, respectively. In situ micro-Raman spectroscopy
was used to measure the systematic changes in the first-order Raman spectral features during the process of temperature or
pressure increment. Three Raman bands, D1, D2, and G bands, were examined to characterize the structural and chemical changes
of kerogen at high temperatures and pressures. We found that the wavenumbers of D1, D2 and G bands showed a linear variation
with both temperature and pressure. Therefore, a correlation between R1 and R2 and the peak temperature in regionally metamorphosed
rocks cannot be applied to this work. This result implies that the G band may serve as a temperature or pressure indicator
during the promotion of maturation of kerogen. Kerogen possesses reversible properties in contrast with the natural samples
recovered from the field suffered from prolonged thermal history during regional metamorphism. 相似文献
225.
Erik Velasco Shelley Pressley Rasa Grivicke Eugene Allwine Luisa T. Molina Brian Lamb 《Theoretical and Applied Climatology》2011,103(3-4):501-517
The parameterization of the energy balance from a residential and commercial neighborhood of Mexico City was investigated using direct measurements of radiative and heat fluxes carried out during the MILAGRO/MCMA-2006 field campaign as a reference. The measured fluxes were used to evaluate different models of the energy balance based on parameterizations that require standard meteorological observations: ambient temperature, relative humidity, atmospheric pressure and cloudiness. It was found that these models reproduce with reasonable accuracy the diurnal features of the radiative and heat fluxes. The largest differences between modeled and observed fluxes correspond to the incoming longwave radiation, mainly due to errors in the cloudiness data. This paper contributes to the understanding of the energy partitioning in (sub)tropical urban environments, particularly in the developing world, where energy balance models have not been evaluated. 相似文献
226.
David Morrill Anderson Bruce A. Bauer Charles R. Buckner Edward Gille Wendy S. Gross Michael Hartman Carrie Morrill Anju M. Shah Eugene R. Wahl 《Earth Science Informatics》2011,4(4):161-167
Reducing uncertainty in global temperature reconstructions of the past millennium remains the key issue in applying this record
to society’s pressing climate change problem. Reconstructions are collaborative, built on the research of hundreds of scientists
who apply their diverse scientific expertise and field and laboratory skill to create the individual proxy reconstructions
that underlie the multi-proxy, global average temperature time series. Web 2.0 features have enabled collaborative efforts
that improve the characterization of uncertainty. Raw data shared via a repository (the World Data Center for Paleoclimatology)
enable new reconstructions from the collection of user-generated data. Standards propagated by expert communities facilitate
quality control and interoperability. Open access to data and computer code promote transparency and make the science accessible
to a broader audience. Blogs, wikis, and listservs share background information and highlight contentious as well as unique
aspects of paleo science. A novel approach now underway, titled the Paleoclimate Reconstruction Challenge, and based on the
sharing of simulated data (pseudo-proxies) and reconstruction results, seeks to facilitate method development, further reducing
uncertainty. Broadly-useful aspects of the Challenge may find application in other fields. 相似文献
227.
R. Eugene Turner 《Estuaries and Coasts》2011,34(5):1084-1093
Although the broadly observed increase in nutrient loading rates to coastal waters in the last 100 years may increase aboveground
biomass, it also tends to increase soil metabolism and lower root and rhizome biomass—responses that can compromise soil strength.
Fourteen different multiyear field combinations of nutrient amendments to salt marshes were made to determine the relationship
between soil strength and various nitrogen, phosphorus, and nitrogen+phosphorus loadings. There was a proportional decline
in soil strength that reached 35% in the 60- to 100-cm soil layer at the highest loadings and did not level off. These loading
rates are equivalent to those in the flow path of the Caernarvon river diversion, a major wetland restoration project near
New Orleans; 12% of the wetlands in the flow path were converted to open water in 2005. The increased nutrient loading from
the Mississippi River watershed this century has also driven the formation of the low oxygen zone (the “Dead Zone”) that forms
off the Louisiana–Texas shelf each summer. These results suggest that improving water quality in the watershed will aid the
restoration of both offshore waters and coastal wetland ecosystems. 相似文献
228.
Eugene H. Guillian 《Earth, Moon, and Planets》2006,99(1-4):309-330
The result of a study on the use of an array of large anti-neutrino detectors for the purpose of monitoring rogue nuclear activity is presented. Targeted regional monitoring of a nation bordering large bodies of water with no pre-existing legal nuclear activity may be possible at a cost of about several billion dollars, assuming several as-yet-untested schemes pan out in the next two decades. These are: (1) the enabling of a water-based detector to detect reactor anti-neutrinos by doping with GdCl3; (2) the deployment of a KamLAND-like detector in a deep-sea environment; and (3) the scaling of a Super-Kamiokande-like detector to a size of one or more megatons. The first may well prove feasible, and should be tested by phase-III Super-Kamiokande in the next few years. The second is more of a challenge, but may well be tested by the Hanohano collaboration in the coming decade. The third is perhaps the least certain, with no schedule for construction of any such device in the foreseeable future. In addition to the regional monitoring scheme, several global, untargeted monitoring schemes were considered. All schemes were found to fail benchmark sensitivity levels by a wide margin, and to cost at least several trillion dollars. 相似文献
229.
The Antarctic Peninsula is one of the most sensitive regions of Antarctica to climate change. Here, ecological and cryospheric systems respond rapidly to climate fluctuations. A 4.4 m thick laminated diatom ooze deposited during the last deglaciation is examined from a marine sediment core (ODP Site 1098) recovered from Basin I, Palmer Deep, western Antarctic Peninsula. This deglacial laminated interval was deposited directly over a glaciomarine diamict, hence during a globally recognised period of rapid climate change. The ultra‐high‐resolution deglacial record is analysed using SEM backscattered electron imagery and secondary electron imagery. Laminated to thinly bedded orange‐brown diatom ooze (near monogeneric Hyalochaete Chaetoceros spp. resting spores) alternates with blue‐grey terrigenous sediments (open water diatom species). These discrete laminae are interpreted as austral spring and summer signals respectively, with negligible winter deposition. Sub‐seasonal sub‐laminae are observed repeatedly through the summer laminae, suggesting variations in shelf waters throughout the summer. Tidal cycles, high storm intensities and/or intrusion of Circumpolar Deep Water onto the continental shelf introduced conditions which enhanced specific species productivity through the season. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
230.
ABSTRACTPresent global climate models (GCMs) are unable to provide reliable projections of physical oceanographic properties on the continental shelf off Newfoundland and Labrador. Here we first establish linear statistical relationships between oceanographic properties and coastal air temperature based on historical observations. We then use these relationships to project future states of oceanographic conditions under different emission scenarios, based on projected coastal air temperatures from global (Canadian Earth System Model, version 2 (CanESM2), Geophysical Fluid Dynamics Laboratory's Earth System Model, version 2M (GFDL-ESM2M)) and regional (Canadian Regional Climate Model (CRCM)) climate models. Estimates based on CanESM2 agree reasonably well with observed trends, but the trends based on two other models result in substantial underestimates. Projected trends are closer to observations under a high emission scenario than under median-level emission scenarios. Over the next 50 years, the increases in projected sea surface temperature off eastern Newfoundland (Station 27) range from 0.4° to 2.2°C. The increases in bottom ocean temperature over the Newfoundland and Labrador Shelves range from 0.4° to 2.1°C. The area of the cold intermediate layer (<0°C) on the Flemish Cap (47°N) section is projected to decrease by 9–35% of the 1981–2010 average. The decline in sea-ice extent off Newfoundland and Labrador ranges from 20 to 77% of the average (0.4–1.5?×?105?km2), and the reduction in the number of icebergs at 48°N off Newfoundland ranges from 30% to nearly 100% of the norm at this latitude. Despite differences among the models and scenarios, statistical projections indicate that conditions in this region will reach or exceed their maxima (sea surface temperature, bottom ocean temperature) and reach or fall below their minima (sea-ice extent, number of icebergs) that were observed during the course of monitoring activities over the past 30–60 years, possibly as early as 2040. We note, however, that the statistical relationships based on historical data may not hold in the future because of the changing influence of input from Arctic waters and because of large uncertainties in projected air temperatures from GCMs. 相似文献