全文获取类型
收费全文 | 686篇 |
免费 | 25篇 |
国内免费 | 8篇 |
专业分类
测绘学 | 16篇 |
大气科学 | 25篇 |
地球物理 | 218篇 |
地质学 | 234篇 |
海洋学 | 9篇 |
天文学 | 170篇 |
自然地理 | 47篇 |
出版年
2020年 | 8篇 |
2017年 | 9篇 |
2016年 | 32篇 |
2015年 | 19篇 |
2014年 | 36篇 |
2013年 | 38篇 |
2012年 | 12篇 |
2011年 | 16篇 |
2010年 | 19篇 |
2009年 | 17篇 |
2008年 | 14篇 |
2007年 | 7篇 |
2006年 | 16篇 |
2005年 | 19篇 |
2003年 | 9篇 |
2002年 | 7篇 |
2001年 | 6篇 |
2000年 | 9篇 |
1999年 | 14篇 |
1998年 | 9篇 |
1997年 | 17篇 |
1996年 | 11篇 |
1995年 | 15篇 |
1994年 | 16篇 |
1993年 | 13篇 |
1992年 | 10篇 |
1991年 | 15篇 |
1990年 | 13篇 |
1989年 | 20篇 |
1988年 | 13篇 |
1987年 | 26篇 |
1986年 | 16篇 |
1985年 | 15篇 |
1984年 | 14篇 |
1983年 | 13篇 |
1982年 | 14篇 |
1981年 | 22篇 |
1980年 | 9篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1976年 | 11篇 |
1975年 | 6篇 |
1973年 | 10篇 |
1972年 | 8篇 |
1971年 | 10篇 |
1969年 | 6篇 |
1968年 | 5篇 |
1967年 | 7篇 |
1963年 | 6篇 |
排序方式: 共有719条查询结果,搜索用时 15 毫秒
91.
HANS PIRLET LAURA M. WEHRMANN BENJAMIN BRUNNER NORBERT FRANK JAN DEWANCKELE DAVID VAN ROOIJ ANNELEEN FOUBERT RUDY SWENNEN LIEVEN NAUDTS MATTHIEU BOONE VEERLE CNUDDE JEAN‐PIERRE HENRIET 《Sedimentology》2010,57(3):786-805
Authigenic gypsum was found in a gravity core, retrieved from the top of Mound Perseverance, a giant cold‐water coral mound in the Porcupine Basin, off Ireland. The occurrence of gypsum in such an environment is intriguing, because gypsum, a classic evaporitic mineral, is undersaturated with respect to sea water. Sedimentological, petrographic and isotopic evidence point to diagenetic formation of the gypsum, tied to oxidation of sedimentary sulphide minerals (i.e. pyrite). This oxidation is attributed to a phase of increased bottom currents which caused erosion and enhanced inflow of oxidizing fluids into the mound sediments. The oxidation of pyrite produced acidity, causing carbonate dissolution and subsequently leading to pore‐water oversaturation with respect to gypsum and dolomite. Calculations based on the isotopic compositions of gypsum and pyrite reveal that between 21·6% and 28·6% of the sulphate incorporated into the gypsum derived from pyrite oxidation. The dissolution of carbonate increased the porosity in the affected sediment layer but promoted lithification of the sediments at the sediment‐water interface. Thus, authigenic gypsum can serve as a signature for diagenetic oxidation events in carbonate‐rich sediments. These observations demonstrate that fluid flow, steered by environmental factors, has an important effect on the diagenesis of coral mounds. 相似文献
92.
B. Balabanova T. Stafilov R. Šajn K. Bačeva 《International Journal of Environmental Science and Technology》2014,11(2):517-528
Different sampling media (moss, lichen and attic dust) were used for monitoring the distribution of 15 elements, including certain trace elements, in the vicinity of an intensively exploited copper mine in the east of the Republic of Macedonia. Moss species (Hypnum cupressiforme and Campothecium lutescens), epiphytic lichens (Hypogymnia physodes and Evernia prunastri) and attic dust were collected for comparative analysis for monitoring air pollution. In both cases (lithological and anthropogenic affected areas) for the distribution of elements, the sampling media follows the expression capabilities: attic dust > moss > lichens. Enrichment factors M/L—moss vs. lichen, for plant response to elements distribution and D/L—attic dust vs. lichen, for historical response of elements distribution were significant for Cu and Ni, which were singled out as the main markers for anthropogenic and geogenic distribution. The factor analysis highlighted geogenic (F1: Ni-Cr-Cd-Fe-Al-K-Mn-Zn) and anthropogenic (F2: As-Cu-Pb) association of elements from three types of media samples. For anthropogenic affected areas, T value and F value for Cu content were significant at p < 0.05 and higher enrichment factors were obtained for lichen, moss and attic dust media (3.8, 5.0 and 5.7, respectively). Spatial distribution for element deposition (with emphasis on Cu and Ni) is not disturbed by the significant differences in the sampling media matrix. Treated sample materials (attic dust, moss, lichen) are shown to be useful in determining an anthropogenic impact, as well as the chemical properties or geological background on orographic diverse terrain in the presence of complex geological structure. 相似文献
93.
Integral transformations of gravitational gradients onto a Gravity Recovery And Climate Experiment (GRACE) type of observable are derived in this article. The gravitational gradients represent components of the gravitational tensor in the local north-oriented frame. The GRACE type of observable corresponds to a difference between two gravitational vectors as projected onto the line of sight between the two GRACE satellites. In total, three integral transformations relating vertical–vertical, vertical–horizontal and horizontal–horizontal gravitational gradients with the GRACE type of observable are provided. Spectral and closed forms of corresponding isotropic kernels are derived for each transformation. Special cases show that the integral transformations are general and relate gravitational gradients to many other quantities of the gravitational field, such as the gravitational vector, and its radial and tangential components. Correctness of the mathematical derivations is validated in a closed-loop simulation using synthetic data. 相似文献
94.
Eclipsing binary TX UMa was observed with the D.A.O. high-dispersion spectrographs in 1969–1970, with emphasis on the detailed coverage of the primary minimum. One spectrum was taken exclusively within totality, thus exhibiting an uncontaminated spectrum of the secondary component. This leads to spectral reclassification of the secondary (F6 IV). The narrowing of the line profile of the H-line in totality is interpreted in terms of synchronous rotation of the secondary (v sini80 km s–1) while the primary rotates faster (v sini130 km s–1) than synchronously (v sini50 km s–1). Although the secondary does not fill in its Roche lobe fully, the system exhibits pronounced indications of rather strong physical interaction. This is now supported also by the profound changes of the line profiles of the H-line with phase. 相似文献
95.
KROON NORRIS KLAUS IAN T. ALEXANDER LEON PAUL BARDOT CHARLES E. BARKER JEAN-PIERRE BELLIER CHARLES D. BLOME LEON J. CLARKE JOCHEN ERBACHER KRISTINA L. FAUL MARY ANNE HOLMES BRIAN T. HUBER MIRIAM E. KATZ KENNETH G. MACLEOD SANDRA MARCA FRANCISA C. MARTINEZ-RUIZ ISAO MITA MUTSUMI NAKAI JAMES G. OGG DOROTHY K. PAK THOMAS K. PLETSCH JEAN M. SELF-TRIAL NICHOLAS J. SHACKLETON JAN SMIT WILLIAM USSLERIII DAVID K. WATKINS JOEN WIDMARK & PAUL A. WILSON 《Geology Today》1998,14(6):222-226
96.
Wenjuan Zheng Anna Lamačová Xuan Yu Pavel Krám Jakub Hruška Pavel Zahradníček Petr Štěpánek Aleš Farda 《水文研究》2021,35(9):e14281
Climate warming is having profound effects on the hydrological cycle by increasing atmospheric demand, changing water availability, and snow seasonality. Europe suffered three distinct heat waves in 2019, and 11 of the 12 hottest years ever recorded took place in the past two decades, which will potentially change seasonal streamflow patterns and long-term trends. Central Europe exhibited six dry years in a row since 2014. This study uses data from a well-documented headwater catchment in Central Europe (Lysina) to explore hydrological responses to a warming climate. We applied a lumped parameter hydrologic model Brook90 and a distributed model Penn State Integrated Hydrologic Model (PIHM) to simulate long-term hydrological change under future climate scenarios. Both models performed well on historic streamflow and in agreement with each other according to the catchment water budget. In addition, PIHM was able to simulate lateral groundwater redistribution within the catchment validated by the groundwater table dynamics. The long-term trends in runoff and low flow were captured by PIHM only. We applied different EURO-CORDEX models with two emission scenarios (Representative Concentration Pathways RCP 4.5, 8.5) and found significant impacts on runoff and evapotranspiration (ET) for the period of 2071–2100. Results from both models suggested reduced runoff and increased ET, while the monthly distribution of runoff was different. We used this catchment study to understand the importance of subsurface processes in projection of hydrologic response to a warming climate. 相似文献
97.
JAN‐PIETER BUYLAERT SÉBASTIEN HUOT ANDREW S. MURRAY PETER VAN DEN HAUTE 《Boreas: An International Journal of Quaternary Research》2011,40(1):46-56
Buylaert, J.‐P., Huot, S., Murray, A.S. & Van den haute, P.: Infrared stimulated luminescence dating of an Eemian (MIS 5e) site in Denmark using K‐feldspar. Boreas, 10.1111/j.1502‐3885.2010.00156.x. ISSN 0300‐9483. Infrared stimulated luminescence (IRSL) dating of K‐feldspars may be an alternative to quartz optically stimulated luminescence (OSL) dating when the quartz OSL signal is too close to saturation or when the quartz luminescence characteristics are unsuitable. In this paper, Eemian (MIS 5e) coastal marine sands exposed in a cliff section on the coast of southern Jutland (Denmark) are used to test the accuracy and precision of IRSL dating using K‐feldspars. This material has been used previously to test quartz OSL dating ( Murray & Funder 2003 ): a small systematic underestimation of <10% compared to the expected age of ~130 ka was reported. In our study, a single‐aliquot regenerative‐dose (SAR) IRSL protocol is used to determine values of equivalent dose (De) and the corresponding fading rates (g values). A significant age underestimation (of up to ~35%) is observed; this is attributed to anomalous fading. Using a single site‐average fading rate of 3.66 ± 0.09%/decade to correct the IRSL ages for all samples provides good agreement between the average fading‐corrected K‐feldspar age (119 ± 6 ka) and the independent age control (132–125 ka). This is despite the reservations of Huntley & Lamothe (2001) that their fading correction method is not expected to work on samples older than ~20–50 ka. This fading‐corrected feldspar result is not significantly different from the overall revised quartz age (114 ± 7 ka) also presented here. We conclude that fading‐corrected IRSL ages measured using K‐feldspar may be both precise and accurate over a greater age range than might be otherwise expected. 相似文献
98.
JAN PIOTROWSKI 《Boreas: An International Journal of Quaternary Research》1997,26(2):157-158
Branson, J., Brown, A. G. & Gregory, K. J. (cds.) 1996: Glubai Continental Changes: The Context of Palaeohydrology 相似文献
99.
Velocity determination of 131 head echoes recorded during Perseid meteor shower observations by the Canadian 2 MW radar, has
been performed under the assumption of either their constant velocity or of its linear change with time. Even though the constant
velocities concentrated at 60 km s-1 generally accepted for the Perseids, a substantial number of echoes had velocities either
lower than 60 km s-1 or greater than this value. The inclusion of variable velocity into considerations led to surprising
result that a great portion of the head echoes accelerated (3 possibly decelerating echoes in comparison with 33 accelerating
cases on the level of relative standard deviations of output parameters not exceeding 10%). It seems that the allocation of
the ionization responsible for the head echo is not entirely identical with the instantaneous meteoroid position. As a consequence,
the velocity derived from the measured head echo coordinates can differ from the velocity of parent body. We are not able
to explain this finding at present.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
100.