全文获取类型
收费全文 | 354篇 |
免费 | 16篇 |
国内免费 | 18篇 |
专业分类
测绘学 | 6篇 |
大气科学 | 20篇 |
地球物理 | 109篇 |
地质学 | 137篇 |
海洋学 | 15篇 |
天文学 | 71篇 |
综合类 | 11篇 |
自然地理 | 19篇 |
出版年
2024年 | 2篇 |
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 6篇 |
2020年 | 7篇 |
2019年 | 10篇 |
2018年 | 27篇 |
2017年 | 19篇 |
2016年 | 21篇 |
2015年 | 27篇 |
2014年 | 21篇 |
2013年 | 33篇 |
2012年 | 24篇 |
2011年 | 29篇 |
2010年 | 22篇 |
2009年 | 16篇 |
2008年 | 16篇 |
2007年 | 18篇 |
2006年 | 9篇 |
2005年 | 7篇 |
2004年 | 11篇 |
2003年 | 6篇 |
2002年 | 14篇 |
2001年 | 6篇 |
2000年 | 8篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 6篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1989年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有388条查询结果,搜索用时 31 毫秒
101.
The paper deals with type, age, and climatic conditions of the last vast glaciation in the East Pamir Mountains. The combination of paleobotanic and geomorphological data as well as absolute age dating of the Kara-Kul lake terrace (27,700 ± 700 years old) supports the thesis that maximum glaciation occurred in the Upper Pleistocene, 14–15 thousand years ago. By special calculations it was established that the tectonic factor of glaciation practically did not exist. This confirmed the existing opinion of a number of scientists that by the beginning of the Upper Pleistocene the Pamir Mountains had almost achieved their present altitude. The analysis of paleobotanic literature permitted the assumption that the amount of precipitation was about the same as it is now: 750 mm/year at an altitude of 4950 m (altitude of the present-day firn line). It was established that the Upper Pleistocene glaciation was caused only by general climatic cooling. 相似文献
102.
103.
Measurement of ecological, climatic and anthropogenic changes underpins the formulation of effective management strategies for sustainable use and protection of the marine environment. Sensors are traditionally used in marine studies to determine physical parameters, but there is increasing demand for real-time information about chemical and biological parameters. These parameters are currently measured in samples collected at sea and subsequently analysed in the laboratory. Biosensors fuse the exquisite sensitivity and specificity of living systems with the processing power of microelectronics to deliver simple, inexpensive measurement systems for use in the field or deployment in situ. While their potential for use in the marine environment is enormous, much published work to date has focussed on applications in freshwater and wastewater. Marine applications pose a substantial challenge in the robustness required for remote application, but recent developments in portable medical devices and receptor design suggest that these demands can now be realistically tackled. 相似文献
104.
Sergey R. Kotov 《Mathematical Geology》2003,35(4):477-491
Records from the Greenland Ice Sheet Project Two ice core are considered in terms of dynamical systems theory and nonlinear prediction. Dynamical systems theory allows us to reconstruct some properties of a phenomenon based only on past behavior without any mechanistic assumptions or deterministic models. A near-term prediction of temperature, including a mean estimate and confidence interval, is made for 800 years into the future. The prediction suggests that the present short-time global warming trend will continue for at least 200 years and be followed by a reverse in the temperature trend. 相似文献
105.
Nathaniel W Rutter Dean RokoshMichael E Evans Edward C LittleJiri Chlachula Andrei Velichko 《Quaternary Research》2003,60(1):101-109
Loess-paleosol sequences of the last interglacial-glacial cycle are correlated from European Russia to central Siberia and the Chinese Loess Plateau. During cold periods represented by marine oxygen isotope stages (OIS) 2 and 4, loess deposition dominated in the Russian Plain and the Loess Plateau. In central Siberia, loess deposition took place also, but five to seven thin, weakly developed paleosols are identified in both stages. OIS 3, in the Chinese Loess Plateau near Yangchang, consists of a loess bed that is flanked by two weakly developed paleosols. At Kurtak, Siberia, OIS 3 is represented by two distinct, stacked paleosols with no loess bed separating the paleosols. In the Russian Plain, OIS 3 consists of a single, possibly welded paleosol, representing upper and lower stage-3 climates. Brunisols and Chernozems dominate the profiles in China and Siberia, whereas Regosols, Luvisols, and Chernozems are evident in the northern and southern Russian Plain, respectively. OIS 5 is represented in China and the Russian Plain by pedo complexes in a series of welded soils, whereas in contrast, the Kurtak site consists of six paleosols with interbedded loess. The paleosols consist largely of Brunisols and Chernozems. Although the three areas examined have different climates, geographical settings, and loess source areas, they all had similar climate changes during the last interglacial-glacial cycle. 相似文献
106.
Role of water in the origin of podiform chromitite deposits 总被引:2,自引:0,他引:2
We report experiments in basalt oversaturated with water to duplicate the nodular ore textures of podiform chromitite ores. In immiscible basalt-water systems saturated with olivine and chromite, olivine will reside in the melt while chromite will collect in the fluid phase. Fractionation is physical and is driven by differential wetting properties of melt and fluid against silicate and oxide surfaces. There is no need to suppress olivine from the liquidus of a primitive basaltic melt as suggested by Irvine [Irvine, T.N., Geology 5 (1977) 273-277], to achieve chromite accumulations as observed in natural podiform ore deposits. The results imply that podiform chromitite ores will form where a primitive olivine-chromite-saturated mantle melt is sufficiently water-rich to exsolve a fluid phase during passage through the uppermost mantle. The most likely geodynamic environment for podiform chromite mineralization to take place is a supra-subduction zone setting. 相似文献
107.
Timofey Samsonov Sergey Koshel Dmitry Walther Bernhard Jenny 《International journal of geographical information science》2019,33(10):2072-2093
Supplementary contour lines are placed between regular contour lines to visualize small but important forms that regular contour lines are unable to show. On topographic maps, typical forms are hillcrests, depressions, saddles, terraces, banks, and levees. No automated method for the selection of supplementary contour lines has been described so far. We document cartographic design principles for the selection of supplementary contour lines for topographic maps, and present an automated method for their placement. Results of the automated method are similar to manually placed supplementary contour lines. Our method helps map authors to create contour line maps that more effectively illustrate relevant small details in maps showing terrain elevation or other scalar fields. 相似文献
108.
The “effective” rigidity of a neutron monitor for a ground-level enhancement (GLE) event is defined so that the event-integrated fluence of solar energetic protons with rigidity above it is directly proportional to the integral intensity of the GLE as recorded by a polar neutron monitor, within a wide range of solar energetic-proton spectra. This provides a direct way to assess the integral fluence of a GLE event based solely on neutron-monitor data. The effective rigidity/energy was found to be 1.13?–?1.42 GV (550?–?800 MeV). A small model-dependent, systematic uncertainty in the value of the effective rigidity is caused by uncertainties in the low-energy range of the neutron-monitor yield function, which requires more detailed computations of the latter. 相似文献
109.
Composition and origin of holotype Al‐Cu‐Zn minerals in relation to quasicrystals in the Khatyrka meteorite 下载免费PDF全文
Marina A. Ivanova Cyril A. Lorenz Sergey E. Borisovskiy Andrey A. Burmistrov Dmitriy V. Korost Alexander V. Korochantsev Maria N. Logunova Sergei I. Shornikov Michail I. Petaev 《Meteoritics & planetary science》2017,52(5):869-883
We investigated the khatyrkite–cupalite holotype sample, 1.2 × 0.5 mm across. It consists of khatyrkite (Cu,Zn)Al2, cupalite (Cu,Zn)Al, and interstitial material with approximate composition (Zn,Cu)Al3. All mineral phases of the holotype sample contain Zn and lack Fe that distinguishes them from khatyrkite and cupalite in the Khatyrka meteorite particles (Bindi et al. 2009 , 2011 , 2012 , 2015 ; MacPherson et al. 2013 ; Hollister et al. 2014 ). Neither highly fractionated natural systems nor geo‐ or cosmochemical processes capable of forming the holotype sample are known so far. The bulk chemistry and thermal history of khatyrkite–cupalite assemblage in the holotype sample hint for its possible industrial origin. Likewise, the aluminides in the Khatyrka meteorite particles may also be derived from industrial materials and mixed with extraterrestrial matter during gold prospecting in the Listvenitovy Stream valley. 相似文献
110.
Andrey G. Andreev Maxim V. Budyansky Michael Yu. Uleysky Sergey V. Prants 《Ocean Dynamics》2018,68(11):1503-1514
Large canyons incise the shelf break of the eastern Bering Sea to be preferred sites of the cross-shelf exchange. The mesoscale eddy activity is particularly strong near the shelf-break canyons. To study the mesoscale dynamics in the Navarin Canyon area of the Bering Sea, the time series of velocities derived from AVISO satellite altimetry between 1993 and 2015, drifters, Argo buoys, and ship-borne data are analyzed. We demonstrate that the strength of anticyclonic eddies along the shelf edge in spring and summer is determined by the wind stress in March–April. The increased southward wind stress in the central Bering Sea forced a supply of low-temperature and low-salinity outer shelf water to the deep basin and formation of the anticyclonic mesoscale circulation seaward of the Navarin Canyon. Enhanced northwestward advection of the Bering Slope Current water leads to increase in an ice-free area in March and April and increased bottom-layer temperature at the outer shelf. The strong (weak) northwestward advection of the eastern Bering Sea waters, determined by eastern winds in spring, creates favorable (unfavorable) conditions for the pollock abundance in the western Navarin Canyon area in summer. 相似文献