全文获取类型
收费全文 | 422篇 |
免费 | 23篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 5篇 |
大气科学 | 45篇 |
地球物理 | 138篇 |
地质学 | 157篇 |
海洋学 | 21篇 |
天文学 | 64篇 |
综合类 | 2篇 |
自然地理 | 18篇 |
出版年
2024年 | 2篇 |
2021年 | 10篇 |
2020年 | 7篇 |
2019年 | 11篇 |
2018年 | 15篇 |
2017年 | 23篇 |
2016年 | 25篇 |
2015年 | 24篇 |
2014年 | 21篇 |
2013年 | 31篇 |
2012年 | 31篇 |
2011年 | 25篇 |
2010年 | 9篇 |
2009年 | 21篇 |
2008年 | 17篇 |
2007年 | 5篇 |
2006年 | 10篇 |
2005年 | 11篇 |
2004年 | 9篇 |
2003年 | 5篇 |
2002年 | 16篇 |
2001年 | 7篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 7篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 6篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1977年 | 3篇 |
1975年 | 2篇 |
1968年 | 2篇 |
1967年 | 5篇 |
1966年 | 4篇 |
1965年 | 6篇 |
1964年 | 4篇 |
1962年 | 2篇 |
1961年 | 4篇 |
1960年 | 5篇 |
1959年 | 5篇 |
1958年 | 3篇 |
1957年 | 2篇 |
1956年 | 3篇 |
1955年 | 3篇 |
1926年 | 2篇 |
1915年 | 1篇 |
排序方式: 共有450条查询结果,搜索用时 15 毫秒
441.
Mehrdad Sardar Abadi Anne-Christine Da Silva Abdolhossein Amini Ali Akbar Aliabadi Frédéric Boulvain Mohammad Hossein Sardar Abadi 《International Journal of Earth Sciences》2014,103(8):2233-2254
The Kashafrud Formation was deposited in the extensional Kopeh-Dagh Basin during the Late Bajocian to Bathonian (Middle Jurassic) and is potentially the most important siliciclastic unit from NE Iran for petroleum geology. This extensional setting allowed the accumulation of about 1,700 m of siliciclastic sediments during a limited period of time (Upper Bajocian–Bathonian). Here, we present a detailed facies analysis combined with magnetic susceptibility (MS) results focusing on the exceptional record of the Pol-e-Gazi section in the southeastern part of the basin. MS is classically interpreted as related to the amount of detrital input. The amount of these detrital inputs and then the MS being classically influenced by sea-level changes, climate changes and tectonic activity. Facies analysis reveals that the studied rocks were deposited in shallow marine, slope to pro-delta settings. A major transgressive–regressive cycle is recorded in this formation, including fluvial-dominated delta to turbiditic pro-delta settings (transgressive phase), followed by siliciclastic to mixed siliciclastic and carbonate shoreface rocks (regressive phase). During the transgressive phase, hyperpycnal currents were feeding the basin. These hyperpycnal currents are interpreted as related to important tectonic variations, in relation to significant uplift of the hinterland during opening of the basin. This tectonic activity was responsible for stronger erosion, providing a higher amount of siliciclastic input into the basin, leading to a high MS signal. During the regressive phase, the tectonic activity strongly decreased. Furthermore, the depositional setting changed to a wave- to tide-dominated, mixed carbonate–siliciclastic setting. Because of the absence of strong tectonic variations, bulk MS was controlled by other factors such as sea-level and climatic changes. Fluctuations in carbonate production, possibly related to sea-level variations, influenced the MS of the siliciclastic/carbonate cycles. Carbonate intervals are characterized by a strong decrease of MS values indicates a gradual reduction of detrital influx. Therefore, the intensity of tectonic movement is thought to be the dominant factor in controlling sediment supply, changes in accommodation space and modes of deposition throughout the Middle Jurassic sedimentary succession in the Pol-e-Gazi section and possibly in the Kopeh-Dagh Basin in general. 相似文献
442.
Maya García-Comas Manuel López-Puertas Bianca M. Dinelli Alberto Adriani Angioletta Coradini 《Icarus》2011,214(2):571-583
After molecular nitrogen, methane is the most abundant species in Titan’s atmosphere and plays a major role in its energy budget and its chemistry. Methane has strong bands at 3.3 μm emitting mainly at daytime after absorption of solar radiation. This emission is strongly affected by non-local thermodynamic equilibrium (non-LTE) in Titan’s upper atmosphere and, hence, an accurate modeling of the non-LTE populations of the emitting vibrational levels is necessary for its analysis. We present a sophisticated and extensive non-LTE model which considers 22 CH4 levels and takes into account all known excitation mechanisms in which they take part. Solar absorption is the major excitation process controlling the population of the v3-quanta levels above 1000 km whereas the distribution of the vibrational energy within levels of similar energy through collisions with N2 is also of importance below that altitude. CH4-CH4 vibrational exchange of v4-quanta affects their population below 500 km. We found that the ν3 → ground band dominates Titan’s 3.3 μm daytime limb radiance above 750 km whereas the ν3 + ν4 → ν4 band does below that altitude and down to 300 km. The ν3 + ν2 → ν2, the 2ν3 → ν3, and the 13CH4ν3 → ground bands each contribute from 5% to 8% at regions below 800 km. The ν3 + 2ν4 → 2ν4and ν2 + ν3 + ν4 → ν2 + ν4 bands each contribute from 2% to 5% below 650 km. Contributions from other CH4 bands are negligible. We have used the non-LTE model to retrieve the CH4 abundance from 500 to 1100 km in the southern hemisphere from Cassini-VIMS daytime measurements near 3.3 μm. Our retrievals show good agreement with previous measurements and model results, supporting a weak deviation from well mixed values from the lower atmosphere up to 1000 km. 相似文献
443.
Reservoir characterization needs the integration of various data through history matching, especially dynamic information
such as production or 4D seismic data. Although reservoir heterogeneities are commonly generated using geostatistical models,
random realizations cannot generally match observed dynamic data. To constrain model realizations to reproduce measured dynamic
data, an optimization procedure may be applied in an attempt to minimize an objective function, which quantifies the mismatch
between real and simulated data. Such assisted history matching methods require a parameterization of the geostatistical model
to allow the updating of an initial model realization. However, there are only a few parameterization methods available to
update geostatistical models in a way consistent with the underlying geostatistical properties. This paper presents a local
domain parameterization technique that updates geostatistical realizations using assisted history matching. This technique
allows us to locally change model realizations through the variation of geometrical domains whose geometry and size can be
easily controlled and parameterized. This approach provides a new way to parameterize geostatistical realizations in order
to improve history matching efficiency. 相似文献
444.
Determination of Trace Element Mass Fractions in Ultramafic Rocks by HR‐ICP‐MS: A Combined Approach Using a Direct Digestion/Dilution Method and Preconcentration by Coprecipitation
下载免费PDF全文
![点击此处可从《Geostandards and Geoanalytical Research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Mathieu Rospabé Mathieu Benoit Frédéric Candaudap 《Geostandards and Geoanalytical Research》2018,42(1):115-129
A procedure is described for the determination of thirty‐seven minor and trace elements (LILE, REE, HFSE, U, Th, Pb, transition elements and Ga) in ultramafic rocks. After Tm addition and acid sample digestion, compositions were determined both following a direct digestion/dilution method (without element separation) and after a preconcentration procedure using a double coprecipitation process. Four ultramafic reference materials were investigated to test and validate our procedure (UB‐N, MGL‐GAS [GeoPT12], JP‐1 and DTS‐2B). Results obtained following the preconcentration procedure are in good agreement with previously published work on REE, HFSE, U, Th, Pb and some of the transition elements (Sc, Ti, V). This procedure has two major advantages: (a) it avoids any matrix effect resulting from the high Mg content of peridotite, and (b) it allows the preconcentration of a larger trace element set than with previous methods. Other elements (LILE, other transition elements Cr, Mn, Co, Ni, Cu, Zn, as well as Ga) were not fully coprecipitated with the preconcentration method and could only be accurately determined through the direct digestion/dilution method. 相似文献
445.
Frédéric Hourdin Marie-Alice Foujols Francis Codron Virginie Guemas Jean-Louis Dufresne Sandrine Bony Sébastien Denvil Lionel Guez François Lott Josefine Ghattas Pascale Braconnot Olivier Marti Yann Meurdesoif Laurent Bopp 《Climate Dynamics》2013,40(9-10):2167-2192
The IPSL-CM5A climate model was used to perform a large number of control, historical and climate change simulations in the frame of CMIP5. The refined horizontal and vertical grid of the atmospheric component, LMDZ, constitutes a major difference compared to the previous IPSL-CM4 version used for CMIP3. From imposed-SST (Sea Surface Temperature) and coupled numerical experiments, we systematically analyze the impact of the horizontal and vertical grid resolution on the simulated climate. The refinement of the horizontal grid results in a systematic reduction of major biases in the mean tropospheric structures and SST. The mid-latitude jets, located too close to the equator with the coarsest grids, move poleward. This robust feature, is accompanied by a drying at mid-latitudes and a reduction of cold biases in mid-latitudes relative to the equator. The model was also extended to the stratosphere by increasing the number of layers on the vertical from 19 to 39 (15 in the stratosphere) and adding relevant parameterizations. The 39-layer version captures the dominant modes of the stratospheric variability and exhibits stratospheric sudden warmings. Changing either the vertical or horizontal resolution modifies the global energy balance in imposed-SST simulations by typically several W/m2 which translates in the coupled atmosphere-ocean simulations into a different global-mean SST. The sensitivity is of about 1.2 K per 1 W/m2 when varying the horizontal grid. A re-tuning of model parameters was thus required to restore this energy balance in the imposed-SST simulations and reduce the biases in the simulated mean surface temperature and, to some extent, latitudinal SST variations in the coupled experiments for the modern climate. The tuning hardly compensates, however, for robust biases of the coupled model. Despite the wide range of grid configurations explored and their significant impact on the present-day climate, the climate sensitivity remains essentially unchanged. 相似文献
446.
Patrick?SchmidtEmail author Ludovic?Bellot-Gurlet Aneta?Slodczyk Fran?ois?Fr?hlich 《Physics and Chemistry of Minerals》2012,39(6):455-464
Chalcedony is a spatial arrangement of hydroxylated nanometre-sized α-quartz (SiO2) crystallites that are often found in association with the silica mineral moganite (SiO2). A supplementary Raman band at 501 cm−1 in the chalcedony spectrum, attributed to moganite, has been used for the evaluation of the quartz/moganite ratio in silica
rocks. Its frequency lies at 503 cm−1 in sedimentary chalcedony, representing a 2 cm−1 difference with its position in pure moganite. We present a study of the 503 cm−1 band’s behaviour upon heat treatment, showing its gradual disappearance upon heating to temperatures above 300 °C. Infrared
spectroscopic measurements of the silanole (SiOH) content in the samples as a function of annealing temperature show a good
correlation between the disappearance of the 503 cm−1 Raman band and the decrease of structural hydroxyl. Thermogravimetric analyses reveal a significant weight loss that can
be correlated with the decreasing of this Raman band. X-ray powder diffraction data suggest the moganite content in the samples
to remain stable. We propose therefore the existence of a hitherto unknown Raman band at 503 cm−1 in chalcedony, assigned to ‘free’ Si–O vibrations of non-bridging Si–OH that oscillate with a higher natural frequency than
bridging Si–O–Si (at 464 cm−1). A similar phenomenon was recently observed in the infrared spectra of chalcedony. The position of this Si–OH-related band
is nearly the same as the Raman moganite band and the two bands may interfere. The actually observed Raman band in silica
rocks might therefore be a convolution of a silanole and a moganite vibration. These findings have broad implications for
future Raman spectroscopic studies of moganite, for the assessment of the quartz/moganite ratio, using this band, must take
into account the contribution from silanole that are present in chalcedony and moganite. 相似文献
447.
Prof. Dr. Fr. Errulat 《Pure and Applied Geophysics》1948,13(3-4):115-123
Ohne Zusammenfassung 相似文献
448.
449.
José C. Aponte Frédéric Séguin Ariel J. Siguelnitzky Jason P. Dworkin Jamie E. Elsila Daniel P. Glavin Harold C. Connolly Jr Dante S. Lauretta 《Meteoritics & planetary science》2024,59(2):286-300
Volatile organic compounds (VOCs) are carbon-containing chemicals that may evaporate rapidly at room temperature and standard pressure. Such organic compounds can be preserved inside carbonaceous chondrite matrices. However, unlike meteoritic soluble organic matter (SOM) and insoluble organic matter (IOM), VOCs are typically lost (at least in part) during sample processing (meteorite crushing) and exposure to terrestrial atmosphere and/or solvents. Like SOM and IOM, VOCs can provide valuable insights into the chemical inventory of the meteorite parent body and even the presolar cloud from which our solar system formed, as well as the composition and processes that occurred during the early formation of our solar system and the asteroidal stage. Thus, in this work, we designed and built an instrument that allowed us to access the VOCs present in samples of the carbonaceous chondrites Murchison and Sutter's Mill after mineral disaggregation by means of freeze–thaw cycling. We simultaneously evaluated the abundances and compound-specific 13C-distributions of the volatiles evolving after meteorite powdering at ~20, 60, and 100°C. Carbon monoxide (CO) and methane (CH4) were released from these meteorites as the most abundant VOCs. They were combusted together for analysis and showed positive δ13C values, indicative of their extraterrestrial origins. Carbon dioxide (CO2) was also an abundant VOC in both meteorites, and its isotopic values suggest that it was mainly formed from dissolved carbonates in the samples. We also detected aldehydes, ketones, and aromatic compounds in low amounts. Contrary to Murchison, which mostly yielded VOCs with positive δ13C values, Sutter's Mill yielded VOCs with negative δ13C values. The less enriched 13C isotope composition of the VOCs detected in Sutter's Mill suggest that they are either terrestrial contaminants, such as VOCs in compressed gas dusters and common laboratory solvents, or compounds disconnected from interstellar sources and/or formed through parent body processing. Understanding the relative abundances and determining the molecular distributions and isotopic compositions of free meteoritic VOCs are key in assessing their extraterrestrial origins and those of chondritic SOM and IOM. Our newly developed technique will be valuable in the study of the samples brought to the Earth from carbonaceous asteroid Bennu by NASA's OSIRIS-REx mission. 相似文献
450.
H.-E. Fröhlich 《Astronomische Nachrichten》2007,328(10):1037-1039
From high-precision MOST photometry spanning 35 days the existence of two spots rotating with slightly differing periods is confirmed. From the marginal probability distribution of the derived differential rotation parameter k its expectation value as well as confidence limits are computed directly from the data. The result depends on the assumed range in inclination i, not on the shape of the prior distributions. Two cases have been considered: (a) The priors for angles, inclination i of the star and spot latitudes β 1,2, are assumed to be constant over i, β 1, and β 2; (b) the priors are assumed to be constant over cos i, sin β 1, and sin β 2. In both cases the full range of inclination is considered: 0° ≤ i ≤ 90°. Scalefree parameters, i. e. periods and spot areas (in case of small spots) are taken logarithmically. Irrespective of the shape of the prior, k is restricted to 0.03 ≤ k ≤ 0.10 (1 σ limits). The inclination i of the star is photometrically ill-defined. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献