全文获取类型
收费全文 | 427篇 |
免费 | 42篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 10篇 |
大气科学 | 33篇 |
地球物理 | 145篇 |
地质学 | 182篇 |
海洋学 | 36篇 |
天文学 | 31篇 |
综合类 | 3篇 |
自然地理 | 31篇 |
出版年
2022年 | 3篇 |
2021年 | 11篇 |
2020年 | 20篇 |
2019年 | 7篇 |
2018年 | 31篇 |
2017年 | 22篇 |
2016年 | 54篇 |
2015年 | 28篇 |
2014年 | 40篇 |
2013年 | 37篇 |
2012年 | 24篇 |
2011年 | 36篇 |
2010年 | 23篇 |
2009年 | 24篇 |
2008年 | 21篇 |
2007年 | 15篇 |
2006年 | 4篇 |
2005年 | 8篇 |
2004年 | 9篇 |
2003年 | 5篇 |
2002年 | 2篇 |
2001年 | 5篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1989年 | 3篇 |
1987年 | 2篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有471条查询结果,搜索用时 78 毫秒
41.
José María González-Jiménez Carlos Villaseca William L. Griffin Suzanne Y. O’Reilly Elena Belousova Eumenio Ancochea Norman J. Pearson 《Contributions to Mineralogy and Petrology》2014,168(2):1-24
Spinel lherzolite and wehrlite xenoliths from the Cenozoic Calatrava volcanic field carry the geochemical imprint of metasomatic agents that have affected the subcontinental lithospheric mantle beneath Central Iberia. Some xenoliths (mainly wehrlites) were enriched in REE, Sr, P, and CO2 by silicic-carbonate-rich metasomatic melts/fluids, while others record the effects of subduction-related hydrous silicate fluids that have precipitated amphibole and induced high Ti/Eu in primary clinopyroxene. The petrographic observations and geochemical data suggest that interstitial glass in the xenoliths represent the quenched products of Si-rich melts that infiltrated the mantle peridotite shortly before the entrainment of the xenoliths in the host magmas that erupted ca 2 million years ago. During their infiltration, the metasomatic melts reacted with peridotite, resulting in silica enrichment, while remobilizing grains of iron-rich monosulfide solid solution (Fe-rich Mss) initially enclosed in, or intergranular to, primary olivine and pyroxenes. In situ laser ablation inductively coupled plasma-mass spectrometry analysis of single sulfide grains reveals that the Fe-rich Mss in glass shows platinum-group element (PGE) patterns and 187Os/188Os compositions identical to the Fe-rich Mss occurring as inclusions in, or at grain boundaries of primary silicates. Moreover, independent of its microstructural position, Fe-rich Mss exhibits PGE and 187Os/188Os signatures typical of Mss either residual after partial melting or crystallized directly from sulfide melts. Our findings reveal that young metasomatic melt(s)/fluid(s) may carry remobilized sulfides with PGE and Os-isotopic signatures identical to those of texturally older sulfides in the peridotite xenolith. These sulfides thus still provide useful information about the timing and nature of older magmatic events in the subcontinental mantle. 相似文献
42.
María Rosa Zapatero Osorio José Caballero Eduardo L. Martín Víctor J.S. Béjar Rafael Rebolo 《Astrophysics and Space Science》2004,292(1-4):673-679
We have monitored S Ori 45, a young, low-mass (20 M j up) brown dwarf of the σ Orionis cluster (~3 Myr, 352 pc), using optical and near-infrared filters. S Ori 45 (spectral type M8.5) is found to be multi-periodic with a dominant modulation at 2.5–3.5 h, and a short modulation at about 46 min. We ascribe the longer of these modulations to a rotation period. After comparing these results with observations of more massive cluster brown dwarfs and field brown dwarfs, we conclude that substellar objects present rotational and angular momentum evolution. We have also obtained intermediate-resolution near-infrared spectroscopy of S Ori 70, which is a T-class, free-floating planetary candidate member in the σ Orionis cluster. Its observed spectrum has been compared to data of field brown dwarfs of similar types and to theoretical spectra computed for different surface temperatures and gravities. We conclude that S Ori 70 has a significantly cool, low-gravity atmosphere. This supports the young age of this object and its membership in the cluster. From state-of-the-art evolutionary models, the mass of S Ori 70 is estimated at 3 times the Jovian mass (+5 ?2 M j up), challenging current stellar/substellar formation models. S Ori 70 remains the lowest mass object so far identified in any open cluster. 相似文献
43.
44.
Human-induced coastal landslide reactivation. Monitoring by PSInSAR techniques and urban damage survey (SE Spain) 总被引:1,自引:1,他引:0
45.
The existing United Nations Framework Convention on Climate Change (UNFCCC) has failed to deliver the rate of low-carbon technology transfer (TT) required to curb GHG emissions in developing countries. This failure has exposed the limitations of universalism and renewed interest in bilateral approaches to TT. Gaps are identified in the UNFCCC approach to climate change TT: missing links between international institutions and the national enabling environments that encourage private investment; a non-differentiated approach for (developing) country and technology characteristics; and a lack of clear measurements of the volume and effectiveness of TTs. Evidence from econometric literature and business experience on climate change TT is reviewed, so as to address the identified pitfalls of the UNFCCC process. Strengths and weaknesses of different methodological approaches are highlighted. International policy recommendations are offered aimed at improving the level of emission reductions achieved through TT. 相似文献
46.
María Lina Berríos-Salas Margarita Guzmán-Vega José Fernández-Labra Manlio Maldini-Sánchez 《Astrophysics and Space Science》1989,162(2):205-209
This work presents the light curves for rotating spotted stars generated by a computational code developed by us. This code is based in a model of the system and its analytical solution. The work also present an analysis of the photometric curve variations with the changes in the model's parameters.As a first result we have simulated a temporal evolution of the light curve when the photospheric spot varies its size and position and we reproduced some observational light curves of the II Peg star.Work supported by Dirección de Investigación, Universidad de La Serena, Chile. 相似文献
47.
We present an analysis of a regional simulation of present-day climate (1981–1990) over southern South America. The regional
model MM5 was nested within time-slice global atmospheric model experiments conducted by the HadAM3H model. We evaluate the
capability of the model in simulating the observed climate with emphasis on low-level circulation patterns and surface variables,
such as precipitation and surface air mean, maximum and minimum temperatures. The regional model performance was evaluated
in terms of seasonal means, seasonal cycles, interannual variability and extreme events. Overall, the regional model is able
to capture the main features of the observed mean surface climate over South America, its seasonal evolution and the regional
detail due to topographic forcing. The observed regional patterns of surface air temperatures (mean, maxima and minima) are
well reproduced. Biases are mostly within 3°C, temperature being overestimated over central Argentina and underestimated in
mountainous regions during all seasons. Biases in northeastern Argentina and southeastern Brazil are positive during austral
spring season and negative in other seasons. In general, maximum temperatures are better represented than minimum temperatures.
Warm bias is larger during austral summer for maximum temperature and during austral winter for minimum temperature, mainly
over central Argentina. The broad spatial pattern of precipitation and its seasonal evolution are well captured; however,
the regional model overestimates the precipitation over the Andes region in all seasons and in southern Brazil during summer.
Precipitation amounts are underestimated over the La Plata basin from fall to spring. Extremes of precipitation are better
reproduced by the regional model compared with the driving model. Interannual variability is well reproduced too, but strongly
regulated by boundary conditions, particularly during summer months. Overall, taking into account the quality of the simulation,
we can conclude that the regional model is capable in reproducing the main regional patterns and seasonal cycle of surface
variables. The present reference simulation constitutes the basis to examine the climate change simulations resulting from
the A2 and B2 forcing scenarios which are being reported in a separate study. 相似文献
48.
Bernardo Cesare Daniela Rubatto María Teresa Gómez-Pugnaire 《Contributions to Mineralogy and Petrology》2009,157(2):267-279
The high-K calc-alkaline volcanic rocks along the Neogene Volcanic Province of SE Spain represent crustal anatectic melts
mixed with mantle components during the opening of the Alborán Sea. Partially melted metapelitic enclaves, along with the
geochemical signature, provide evidence of their crustal source. U–Pb SHRIMP geochronology on monazite and zircon from enclaves
and their hosting lavas in the localities of El Hoyazo, Mazarrón and Mar Menor reveals variable delays between the melting
at depth and the eruption of the volcanics. These data indicate that: (1) the most important event of anatexis in the Neogene
spanned at least the 3 m.y. interval between 12 and 9 Ma; (2) there is no trend in age of crustal melting; and (3) the delay
between magma generation and extrusion varies from more than 3 m.y. at El Hoyazo to ~0.5 m.y. and possibly 2.5 m.y. at Mar
Menor, with no significant delay measurable at Mazarrón. The variable time delay between anatexis and lava extrusion indicates
that radiometric ages of volcanics may provide misleading information on the timing of magma genesis occurring at depth. This
highlights the pitfall of basing detailed geodynamic models on volcanic extrusion ages alone.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
49.
Anne W. Nolin Eric A. Sproles David E. Rupp Ryan L. Crumley Mariana J. Webb Ross T. Palomaki Eugene Mar 《水文研究》2021,35(6):e14262
Snow is Earth's most climatically sensitive land cover type. Traditional snow metrics may not be able to adequately capture the changing nature of snow cover. For example, April 1 snow water equivalent (SWE) has been an effective index for streamflow forecasting, but it cannot express the effects of midwinter melt events, now expected in warming snow climates, nor can we assume that station-based measurements will be representative of snow conditions in future decades. Remote sensing and climate model data provide capacity for a suite of multi-use snow metrics from local to global scales. Such indicators need to be simple enough to “tell the story” of snowpack changes over space and time, but not overly simplistic or overly complicated in their interpretation. We describe a suite of spatially explicit, multi-temporal snow metrics based on global satellite data from NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) and downscaled climate model output for the U.S. We describe and provide examples for Snow Cover Frequency (SCF), Snow Disappearance Date (SDD), At-Risk Snow (ARS), and Frequency of a Warm Winter (FWW). Using these retrospective and prospective snow metrics, we assess the current and future snow-related conditions in three hydroclimatically different U.S. watersheds: the Truckee, Colorado Headwaters, and Upper Connecticut. In the two western U.S. watersheds, SCF and SDD show greater sensitivity to annual differences in snow cover compared with data from the ground-based Snow Telemetry (SNOTEL) network. The eastern U.S. watershed does not have a ground-based network of data, so these MODIS-derived metrics provide uniquely valuable snow information. The ARS and FWW metrics show that the Truckee Watershed is highly vulnerable to conversion from snowfall to rainfall (ARS) and midwinter melt events (FWW) throughout the seasonal snow zone. In comparison, the Colorado Headwaters and Upper Connecticut Watersheds are colder and much less vulnerable through mid- and late-century. 相似文献
50.
On December 20, 2004 the Minor Planet Center issued the Minor Planet Electronic Circular (MPEC) 2004-Y25 announcing the discovery of a new Near Earth Asteroid (NEA) with designation 2004 MN4. Only two days later, when the Christmas holidays were about to begin, it was already apparent that this asteroid, currently known as Apophis, would be notorious: our close-approach monitoring system, CLOMON2, was already showing a Virtual Impactor (VI) in 2029 reaching the level 2 in the Torino Scale, the first asteroid to reach that level since our monitoring system had been operational. However, this was just the beginning of what it was to come in the subsequent days. In this paper we will give an overview of the NEODyS-CLOMON2 system and provide the details on how Apophis’ collision scenario evolved, the way NEODyS’ team handled it and the crazy 2004’ Christmas holidays we had due to this unexpected guest. 相似文献