全文获取类型
收费全文 | 133篇 |
免费 | 6篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 14篇 |
大气科学 | 12篇 |
地球物理 | 39篇 |
地质学 | 46篇 |
海洋学 | 2篇 |
天文学 | 19篇 |
自然地理 | 11篇 |
出版年
2022年 | 3篇 |
2021年 | 7篇 |
2020年 | 4篇 |
2019年 | 5篇 |
2018年 | 8篇 |
2017年 | 4篇 |
2016年 | 10篇 |
2015年 | 10篇 |
2014年 | 11篇 |
2013年 | 8篇 |
2012年 | 14篇 |
2011年 | 8篇 |
2010年 | 1篇 |
2009年 | 14篇 |
2008年 | 3篇 |
2007年 | 2篇 |
2006年 | 3篇 |
2005年 | 2篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1996年 | 4篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1991年 | 3篇 |
1988年 | 2篇 |
1986年 | 2篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有143条查询结果,搜索用时 15 毫秒
131.
Gianluca Marino Eelco J. Rohling Francesca Sangiorgi Angela Hayes James L. Casford André F. Lotter Michal Kucera Henk Brinkhuis 《Quaternary Science Reviews》2009,28(27-28):3246-3262
Changes in the orbital parameters, solar output, and ocean circulation are widely considered as main drivers of the Holocene climate. Yet, the interaction between these forcings and the role that they play to produce the pattern of changes observed in different domains of the climate system remain debated. Here, we present new early to middle Holocene season-specific sea surface temperature (SST) and δ18Oseawater results, based on organic-walled dinoflagellate cyst and planktonic foraminiferal data from two sediment cores located in the central (SL21) and south-eastern (LC21) Aegean Sea (eastern Mediterranean). Today, this region is affected by high to mid latitude climate in winter and tropical/subtropical climate in summer. The reconstructed δ18Oseawater from LC21 displays a marked (~1.3%) negative shift between 10.7 and 9.7 ka BP, which represents the regional expression of the orbitally driven African monsoon intensification and attendant freshwater flooding into the eastern Mediterranean. A virtually contemporaneous shift, of the same sign and magnitude, is apparent in the δ18Ospeleothem record from Soreq Cave (Northern Israel), an important part of which may therefore reflect a change in the isotopic composition of the moisture source region (Aegean and Levantine Seas). Our SST reconstructions show that Aegean winter SSTs decreased in concert with intensifications of the Siberian High, as reflected in the GISP2 nss [K+] record. Specifically, three distinct sea surface cooling events at 10.5, 9.5–9.03 and 8.8–7.8 ka BP in the central Aegean Sea match increases in GISP2 nss [K+]. These events also coincide with dry interludes in Indian monsoon, hinting at large (hemispheric) scale teleconnections during the early Holocene on centennial timescales. A prominent short-lived (~150 years) cooling event in core SL21 – centred on 8.2 ka BP – is coeval to the ‘8.2 ka BP event’ in the Greenland δ18Oice, which is commonly linked to a melt-water related perturbation of the Atlantic Meridional Overturning Circulation and associated ocean heat transport. By deciphering the phasing between a recently published record of reduced overflow from the Nordic Seas into the northern North Atlantic, the Greenland δ18Oice ‘8.2 ka BP event’ anomaly, and the short-lived cooling in SL21, we demonstrate severe far-field impacts of this North Atlantic event in the Aegean Sea. The Aegean is isolated from the North Atlantic oceanic circulation, so that signal transmission must have been of an atmospheric nature. 相似文献
132.
Jana Ticha Milos Tichy Michal Kocer Michaela Honkova 《Meteoritics & planetary science》2009,44(12):1889-1895
Abstract— Near‐Earth object (NEO) research plays an increasingly important role not only in solar system science but also in protecting our planetary environment as well as human society from the asteroid and comet hazard. Consequently, interest in detecting, tracking, cataloguing, and the physical characterizing of these bodies has steadily grown. The discovery rate of current NEO surveys reflects progressive improvement in a number of technical areas. An integral part of NEO discovery is astrometric follow‐up crucial for precise orbit computation and for the reasonable judging of future close encounters with the Earth, including possible impact solutions. The KLENOT Project of the Klet Observatory (South Bohemia, Czech Republic) is aimed especially at the confirmation, early follow‐up, long‐arc follow‐up, and recovery of near‐Earth objects. It ranks among the world's most prolific professional NEO follow‐up programs. The 1.06 m KLENOT telescope, put into regular operation in 2002, is the largest telescope in Europe used exclusively for observations of minor planets and comets, and full observing time is dedicated to the KLENOT team. In this paper, we present the equipment, technology, software, observing strategy, and results of the KLENOT Project obtained during its first phase from March 2002 to September 2008. The results consist of thousands of precise astrometric measurements of NEOs and also three newly discovered near‐Earth asteroids. Finally, we also discuss future plans reflecting also the role of astrometric follow‐up in connection with the modus operandi of the next generation surveys. 相似文献
133.
Michal Shatkay David A. Anati Joel R. Gat 《International Journal of Salt Lake Research》1993,2(2):93-110
Measurements of dissolved oxygen, density and temperature were con ducted in the Dead Sea between August 1987 and December
1989. Oxygen concentrations were found to vary around an average value of 0.8 mlSTP (standard temperature and pressure) per
kg. Dissolved oxygen variations were found to reflect both physical processes (a deepening of the epilimnion, a turnover etc.)
and chemical processes (oxidation reduction). Transport coefficients for the oxygen exchange across the air/sea interface
were found to be generally low compared to expected values based on laboratory experiments; the presence of surface films
which inhibit the gas exchange rates under calm weather conditions is suspected. During stormy weather, the exchange rates
were considerably higher, suggesting that the entrainment of bubbles was involved in the gas exchange process.
Contribution No. 95, Department of Environmental Sciences and Energy Research. The Weizmann Institute of Science 相似文献
134.
3-D network ray tracing 总被引:15,自引:0,他引:15
135.
At the end of March 2006, the Czech Republic (CZ) witnessed a fast thawing of an unusually thick snow cover in conjunction with massive rainfall. Most watercourses suffered floods, and more than 90 shallow landslides occurred in the Moravian region of Eastern CZ, primarily in non-forested areas. This region, geologically part of the Outer Western Carpathians, is prone to landslides because the bedrock is highly erodible Mesozoic and Tertiary flysch.The available meteorological data (depth of snow, water equivalent of the snow, cumulative rainfall, air and soil temperatures) from five local weather stations were used to construct indices quantitatively describing the snow thaw. Among these, the Total Cumulative Precipitation (TCP) combines the amount of water from both thawing snow and rainfall. This concurrence of rain and runoff from snow melt was the decisive factor in triggering the landslides in the spring.The TCP index was applied to data of snow thaw periods for the last 20 years, when no landslides were recorded. This was to establish the safe threshold of TCP without landslides. The calculated safe threshold value for the region is ca. 100 mm of water delivered to the soil during the spring thaw (corresponding to ca. 11 mm day− 1). In 2006, 10% of the landslides occurred under or at 100 mm of TCP. The upper value of 155 mm covered all of the landslides. 相似文献
136.
137.
Iterative Spherical Downward Continuation Applied to Magnetic and Gravitational Data from Satellite 总被引:1,自引:0,他引:1
Josef Sebera Michal Šprlák Pavel Novák Aleš Bezděk Miloš Vaľko 《Surveys in Geophysics》2014,35(4):941-958
In the last few decades, satellites have acquired various potential data sets hundreds of kilometers above the Earth’s surface. Conventionally, these global magnetic and gravitational data sets are approximated by using spherical harmonics that allow straightforward work with both fields outside the Earth’s mass. In this article, we present an alternative approach for working with potential data in mass-free space given over a regular coordinate grid on a spherical surface. The algorithm is based on an iterative scheme and the Poisson integral equation for the sphere. With help from the Fourier transform, global potential (magnetic or gravitational) data can efficiently be continued from a mean orbital sphere down to a reference surface without using the spherical harmonics. This is illustrated both with simulated magnetic field data and with real data from the satellite gradiometry mission GOCE. In the case of simulated magnetic data and the downward continuation for 450 km, we have achieved a root mean square at the level of 0.05 nT, while it was <1 E (eotvos) for real GOCE data continued for 250 km. The crucial point is to apply the algorithm twice as a large part of noise can be removed from the input data. 相似文献
138.
Effects of vegetation on channel morphodynamics: results and insights from laboratory experiments 总被引:1,自引:0,他引:1
A series of laboratory experiments demonstrates that riparian vegetation can cause a braided channel to self‐organize to, and maintain, a dynamic, single‐thread channel. The initial condition for the experiments was steady‐state braiding in non‐cohesive sand under uniform discharge. From here, an experiment consisted of repeated cycles alternating a short duration high flow with a long duration low flow, and uniform dispersal of alfalfa seeds over the bed at the end of each high flow. Plants established on freshly deposited bars and areas of braidplain that were unoccupied during low flow. The presence of the plants had the effect of progressively focusing the high flow so that a single dominant channel developed. The single‐thread channel self‐adjusted to carry the high flow. Vegetation also slowed the rate of bank erosion. Matching of deposition along the point bar with erosion along the outer bend enabled the channel to develop sinuosity and migrate laterally while suppressing channel splitting and the creation of new channel width. The experimental channels spontaneously reproduced many of the mechanisms by which natural meandering channels migrate and maintain a single dominant channel, in particular bend growth and channel cutoff. In contrast with the braided system, where channel switching is a nearly continuous process, vegetation maintained a coherent channel until wholesale diversion of flow via cutoff and/or avulsion occurred, by which point the previous channel tended to be highly unfavorable for flow. Thus vegetation discouraged the coexistence of multiple channels. Varying discharge was key to allowing expression of feedbacks between the plants and the flow and promoting the transition from braiding to a single‐thread channel that was then dynamically maintained. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
139.
Masanobu?ShinozukaEmail author Yuko?Murachi Xuejiang?Dong Youwei?Zhou Michal?J.?Orlikowski 《地震工程与工程振动(英文版)》2003,2(2):169-179
The objective of this research is to determine the effect earthquakes have on the performance of transportation network systems. To do this, bridge fragility curves, expressed as a function of peak ground acceleration (PGA) and peak ground velocity (PGV), were developed. Network damage was evaluated under the 1994 Northridge earthquake and scenario earthquakes. A probabilistic model was developed to determine the effect of repair of bridge damage on the improvement of the network performance as days passed after the event. As an example, the system performance degradation measured in terms of an index, “Drivers Delay,“ is calculated for the Los Angeles area transportation system, and losses due to Drivers Delay with and without retrofit were estimated. 相似文献
140.
The δ18O of mammalian bone-phosphate varies linearly with δ18O of environmental water, but is not in isotopic equilibrium with that water. This situation is explained by a model of δ18O in body water in which the important fluxes of exchangeable oxygen through the body are taken into account. Fractionation of oxygen isotopes between body and environmental drinking water is dependent on the rates of drinking and respiration. Isotopic fractionation can be estimated from physiological data and the estimates correlate very well with observed fractionation. Species whose water consumption is large relatively to its energy expenditure is sensitive to isotopic ratio changes in environmental water. 相似文献