全文获取类型
收费全文 | 256篇 |
免费 | 4篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 3篇 |
大气科学 | 18篇 |
地球物理 | 41篇 |
地质学 | 64篇 |
海洋学 | 15篇 |
天文学 | 95篇 |
综合类 | 7篇 |
自然地理 | 19篇 |
出版年
2022年 | 5篇 |
2021年 | 4篇 |
2020年 | 6篇 |
2019年 | 8篇 |
2018年 | 11篇 |
2017年 | 6篇 |
2016年 | 12篇 |
2015年 | 8篇 |
2014年 | 20篇 |
2013年 | 11篇 |
2012年 | 5篇 |
2011年 | 17篇 |
2010年 | 9篇 |
2009年 | 14篇 |
2008年 | 18篇 |
2007年 | 16篇 |
2006年 | 8篇 |
2005年 | 3篇 |
2004年 | 4篇 |
2003年 | 8篇 |
2002年 | 11篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 11篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1979年 | 3篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 3篇 |
1970年 | 1篇 |
排序方式: 共有262条查询结果,搜索用时 15 毫秒
51.
Maria V. Pastor Josep L. Pelegrí Alonso Hernández-Guerra Jordi Font Jordi Salat Mikhail Emelianov 《Continental Shelf Research》2008
A historical data set is used to describe the coastal transition zone off Northwest Africa during spring 1973 and fall 1975, from 17° to 26°N, with special emphasis on the interaction between subtropical (North Atlantic Central Waters) and tropical (South Atlantic Central Waters) gyres. The near-surface geostrophic circulation, relative to 300 m, is quite complex. Major features are a large cyclonic pattern north of Cape Blanc (21°N) and offshore flow at the Cape Verde front. The large cyclone occurs in the region of most intense winds, and resembles a large meander of the baroclinic southward upwelling jet. The Cape Verde frontal system displays substantial interleaving that may partly originate as mesoscale features at the coastal upwelling front. Property–property diagrams show that the front is an effective barrier to all properties except temperature. The analysis of the Turner angle suggests that the frontal system is characterized by large heat horizontal diffusion as a result of intense double diffusion, which results in the smoothing of the temperature horizontal gradients. Nine cross-shore sections are used to calculate along-shore geostrophic water-mass and nutrient transports and to infer exchanges between the coastal transition zone and the deep ocean (import: deep ocean to transition zone; export: transition zone to deep ocean). These exchanges compare well with mean wind-induced transports and actual geostrophic cross-shore transport estimates. The region is divided into three areas: southern (18–21°N), central (21–23.5°N), and northern (23.5–26°N). In the northern area geostrophic import is roughly compensated with wind-induced export during both seasons. In the central area geostrophic import is greater than wind-induced export during spring, resulting in net import of both water (0.8 Sv) and nitrate (14 kmol s−1), but during fall both factors again roughly cancel. In the southern area geostrophy and wind join to export water and nutrients during both seasons, they increase from 0.6 Sv and 3 kmol s−1 during fall to 2.9 Sv and 53 kmol s−1 during spring. 相似文献
52.
Alexei Pozdnoukhov Mikhail Kanevski 《Stochastic Environmental Research and Risk Assessment (SERRA)》2008,22(5):647-660
The algorithmic approach to data modelling has developed rapidly these last years, in particular methods based on data mining
and machine learning have been used in a growing number of applications. These methods follow a data-driven methodology, aiming
at providing the best possible generalization and predictive abilities instead of concentrating on the properties of the data
model. One of the most successful groups of such methods is known as Support Vector algorithms. Following the fruitful developments
in applying Support Vector algorithms to spatial data, this paper introduces a new extension of the traditional support vector
regression (SVR) algorithm. This extension allows for the simultaneous modelling of environmental data at several spatial
scales. The joint influence of environmental processes presenting different patterns at different scales is here learned automatically
from data, providing the optimum mixture of short and large-scale models. The method is adaptive to the spatial scale of the
data. With this advantage, it can provide efficient means to model local anomalies that may typically arise in situations
at an early phase of an environmental emergency. However, the proposed approach still requires some prior knowledge on the
possible existence of such short-scale patterns. This is a possible limitation of the method for its implementation in early
warning systems. The purpose of this paper is to present the multi-scale SVR model and to illustrate its use with an application
to the mapping of Cs137 activity given the measurements taken in the region of Briansk following the Chernobyl accident. 相似文献
53.
Volker Rachold Mikhail N. Grigoriev Felix E. Are Steve Solomon Erk Reimnitz Heidemarie Kassens Martin Antonow 《International Journal of Earth Sciences》2000,89(3):450-460
This article presents a comparison of sediment input by rivers and by coastal erosion into both the Laptev Sea and the Canadian Beaufort Sea (CBS). New data on coastal erosion in the Laptev Sea, which are based on field measurements and remote sensing information, and existing data on coastal erosion in the CBS as well as riverine sediment discharge into both the Laptev Sea and the CBS are included. Strong regional differences in the percentages of coastal erosion and riverine sediment supply are observed. The CBS is dominated by the riverine sediment discharge (64.45᎒6 t a-1) mainly of the Mackenzie River, which is the largest single source of sediments in the Arctic. Riverine sediment discharge into the Laptev Sea amounts to 24.10᎒6 t a-1, more than 70% of which are related to the Lena River. In comparison with the CBS, the Laptev Sea coast on average delivers approximately twice as much sediment mass per kilometer, a result of higher erosion rates due to higher cliffs and seasonal ice melting. In the Laptev Sea sediment input by coastal erosion (58.4᎒6 t a-1) is therefore more important than in the CBS and the ratio between riverine and coastal sediment input amounts to 0.4. Coastal erosion supplying 5.6᎒6 t a-1 is less significant for the sediment budget of the CBS where riverine sediment discharge exceeds coastal sediment input by a factor of ca. 10. 相似文献
54.
Bruno P. Besser Mikhail I. Pudovkin Valentina V. Lebedeva Svetlana A. Zaitseva Claudia-Veronika Meister 《Astrophysics and Space Science》2000,274(1-2):399-405
Variations of the magnetic field and plasma parameters across the Earth's magnetosheath are calculated for an anisotropic
plasma in the Chew-Goldberger-Low approximation. Additionally, proton pitch-angle diffusion is taken into account as the energy
transfer mechanism between the direction perpendicular and parallel to the magnetic field. We discuss the main characteristics
of the magnetic barrier for different temperature relaxation times and their dependence on the interplanetary magnetic field
orientation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
55.
We examine a model for the expected contributions to the soft X-ray background (SXRB) due to bremsstrahlung and re-combination radiation of gas, enriched with heavy elements, located in groups of galaxies taken from Tully'sCatalog of Nearby Groups of Galaxies.
It is shown that the contribution to the SXRB of groups of galaxies can explain up to 20% of the observed flux depending on the chemical composition and ratio of emitting mass to assumed virial mass. 相似文献
56.
Mi-Kyung Yoon Mikhail Baykulov Stefan Dümmong Heinz-Jürgen Brink Dirk Gajewski 《International Journal of Earth Sciences》2008,97(5):887-898
The influence of deep crustal processes on basin formation and evolution and its relation to current morphology is not well
understood yet. A key feature to unravel these issues is a detailed seismic image of the crust. A part of the data recorded
by the hydrocarbon industry in the late 1970s and 1980s in the North German Basin were released to the public recently. The
seismic reflection data were recorded down to 15 s two-way travel time. The mean Common Midpoint fold of about 20 is relatively
low compared to contemporary seismic acquisitions. The processing of the 1980s focussed on the sedimentary structures to explore
the hydrocarbon potential of this area. We applied the Common Reflection Surface stack technique to the data sets, which is
well suited for low-fold data. The reprocessing was focussed on the imaging of the subsedimentary crustal range. The reprocessed
images show enhanced reflections, especially in the mid and lower crustal part. Also, the image of the salt structures in
the graben area was improved. Furthermore, the reprocessed images indicate an almost flat Moho topography in the area of the
Glückstadt Graben and an additional lower crustal structure, which can be correlated with a high-density body found in recent
gravity modeling studies. 相似文献
57.
Mark P. S. Krekeler Julie Morton Jill Lepp Cynthia M. Tselepis Mikhail Samsonov Lance E. Kearns 《Environmental Geology》2008,55(1):123-147
Clay-rich mine tailings from phosphate mine operations in Florida are a major environmental and economic problem. Options
for reclamation and restoration for these tailings are very limited and are fundamentally restricted by poor physical properties
such as low mechanical strength, low hydraulic conductivity, and heavy metal content. The major control on these bulk physical
properties is the mineralogy of the materials. Eight continuous push borings were obtained to investigate stratigraphy, mineralogy,
aspects of geochemistry, and bulk properties of a deposit of clay-rich mine tailings from a phosphate mine near Bartow, Florida
that ceased operations in the early 1970s. Stratigraphy is dominated by laminated clay-rich sediment with minor units of silt
and sand. An intact kaolinite liner occurs near the impoundment walls and the impoundment floor has approximately 4 m of relief.
Moisture content varies from 4.35 to 57.40 wt% and organic content varies from 0.41 to 9.53 wt%. Bulk XRF investigation indicates
that the P2O5 concentrations vary from approximately 4 to 21 wt%. A very strong correlation (r
2 = 0.92) between CaO and P2O5 indicates that apatite is a major control on the phosphate. The strong correlation (r
2 = 0.77) of Al2O3 and TiO2 suggests that the source materials for this deposit are comparatively uniform. A number of heavy metal elements and trace
elements occur. Cr, V, Ni, Cu are interpreted to be in phosphate minerals, largely apatite. Sr and Pb are interpreted to be
in both phyllosilicates and phosphate minerals. Two populations of apatite were observed in the clay-sized fraction, one that
was Fe and Si- bearing and another that was only Si-bearing. Fe-bearing apatite had Fe2O3 contents that varied from 0.38 to 5.32 wt% and SiO2 contents that varied from 0.90 to 3.32 wt%. The other apatite population had a wider range of SiO2 contents that varied from 0.77 to 8.80 wt%. TEM imaging shows that apatite grains are dominantly single crystals with lesser
amounts of aggregates. Wavellite commonly occurs as individual or clusters of lath-like crystals and the chemical composition
differs from the pure aluminium phosphate end member with average concentrations of components being that of CaO (1.57 wt%),
Fe2O3 (1.98 wt%), SiO2 (5.94 wt%). In the clay-sized phosphate minerals investigated no fluorine was found above detection limit (approximately
0.15 wt%), nor was any uranium, radium, heavy metal, or REE element detected. The phyllosilicate mineralogy of the deposit
is dominated by smectite (montmorillonite with lesser amounts of nontronite), palygorskite, illite and kaolinite. No systematic
variation in the relative proportions of phyllosilicates was observed in the clay deposit. Energy dispersive spectroscopy
EDS analysis indicates that chemical compositions of phyllosilicates are somewhat typical but overall are enriched with respect
to Fe compared to theoretical end members. The relative enrichment of Fe is interpreted to be a primary sedimentary feature.
Ca content in smectite minerals is high and may inhibit stabilization using lime or similar methods. The high percentages
of montmorillonite and palygorskite explain the high bulk water contents observed. This investigation provides fundamentally
new details regarding clay tailing deposits from closed phosphate mines in central Florida which can be used in restoration
and reclamation efforts. 相似文献
58.
59.
Svetlana V. Pakhomova Per O.J. Hall Mikhail Yu. Kononets Alexander G. Rozanov Anders Tengberg Andrei V. Vershinin 《Marine Chemistry》2007
Fluxes of dissolved forms of iron and manganese across the sediment–water interface were studied in situ in the Gulf of Finland and the Vistula Lagoon (Baltic Sea), and in the Golubaya Bay (Black Sea) from 2001 to 2005. Fluxes were measured using chamber incubations, and sediment cores were collected and sliced to assess the porewater and solid phase metal distribution at different depths. Measured and calculated benthic fluxes of manganese and iron were directed out of sediment for all sites and were found to vary between 70–4450 and 5–1000 µmole m− 2 day− 1 for manganese and iron, respectively. The behavior of the studied metals at various redox conditions in the near-bottom water and in the sediment was the main focus in this study. Our results show the importance of bottom water redox conditions for iron fluxes. We measured no fluxes at oxic conditions, intermediate fluxes at anoxic conditions (up to 200 μmole m− 2 day− 1) and high fluxes at suboxic conditions (up to 1000 μmole m− 2 day− 1). Total dissolved iron fluxes were generally dominated by iron(II). Contribution of iron(III) to the total iron flux did not exceed 20%. Obtained fluxes of manganese at all studied regions showed a linear correlation (r2 = 0.97) to its concentration in the porewater of the top sediment layer (0–5 mm) and did not depend on dissolved oxygen concentrations of bottom water. Organically complexed iron and manganese were in most cases not involved in the benthic exchange processes. 相似文献
60.
Boris Shustov Mikhail Sachkov Ana I. Gómez de Castro Maohai Huang Klaus Werner Norbert Kappelmann Isabella Pagano 《Astrophysics and Space Science》2009,320(1-3):187-190
The World Space Observatory UltraViolet (WSO–UV) is an international space mission devoted to UV spectroscopy and imaging. The observatory includes a 170 cm aperture telescope capable of high-resolution and long slit low-resolution spectroscopy, and deep UV and optical imaging. The observatory is designed for observations in the ultraviolet domain where most of astrophysical processes can be efficiently studied with unprecedented capability. 相似文献