全文获取类型
收费全文 | 422篇 |
免费 | 26篇 |
国内免费 | 7篇 |
专业分类
测绘学 | 17篇 |
大气科学 | 22篇 |
地球物理 | 137篇 |
地质学 | 130篇 |
海洋学 | 12篇 |
天文学 | 116篇 |
综合类 | 7篇 |
自然地理 | 14篇 |
出版年
2022年 | 1篇 |
2021年 | 11篇 |
2020年 | 10篇 |
2019年 | 13篇 |
2018年 | 20篇 |
2017年 | 16篇 |
2016年 | 22篇 |
2015年 | 28篇 |
2014年 | 29篇 |
2013年 | 22篇 |
2012年 | 20篇 |
2011年 | 31篇 |
2010年 | 18篇 |
2009年 | 22篇 |
2008年 | 15篇 |
2007年 | 21篇 |
2006年 | 14篇 |
2005年 | 11篇 |
2004年 | 10篇 |
2003年 | 9篇 |
2002年 | 11篇 |
2001年 | 8篇 |
2000年 | 7篇 |
1999年 | 5篇 |
1998年 | 10篇 |
1997年 | 2篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 9篇 |
1988年 | 1篇 |
1987年 | 10篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1976年 | 2篇 |
1973年 | 1篇 |
1971年 | 2篇 |
1970年 | 1篇 |
1967年 | 1篇 |
1963年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有455条查询结果,搜索用时 31 毫秒
181.
Qualitative geological acceptance criteria and quantitative seismological acceptance criteria for radioactive waste disposals are developed. The background material for the initiation of site selection and for its earthquake hazard assessment is discussed. The recent movements of the Earth's surface as well as the other mechanical properties of geological media, hydrological conditions of geological blocks, their groundwater chemistry, geochemical rheology, petrological analyses of rocks, etc., have to be taken into account. A new comprehensive integrated safety analysis of the final underground disposal of spent nuclear fuel has been underway in the Czech Republic since 1991. In accordance with these seismogeological acceptance criteria regions for building underground final radioactive waste disposals are singled out in the Czech Republic. 相似文献
182.
We present observations of optical spectra of a flare in which blue line asymmetry was seen for more than 4 min close to the flare onset. The maximum blue asymmetry coincided with the maximum of a hard X-ray and microwave burst. We discuss possible interpretations of the blue asymmetry and conclude that the most plausible one is electron-beam heating with return current. Although this process predicts downflows in the lower transition region and upper chromosphere, its ultimate effect on the line profiles can be blue asymmetry: the upper layers moving away from us absorb the radiation of the red peak thus lowering its intensity in comparison to the blue one. 相似文献
183.
Muha Abdullah Al Pavel Sharif A. Mukul Mohammad Belal Uddin Kazuhiro Harada Mohammed A. S. Arfin Khan 《山地科学学报》2016,13(6):1085-1095
We investigated the effect of tree cover, forest patch and disturbances on tree species richness in a highly diverse conservation area of northeast Bangladesh. A systematic sampling protocol was adopted and 80 sub-plots from twenty five 1 ha plots were used for the vegetation survey. Linear regression analysis was performed to understand the effect of patch area, disturbances and tree cover on tree species richness. Ordination using Redundancy analysis (RDA) and Non-metric Multi Dimensional Scaling (NMDS) were also performed to explore the tree species compositional similarities along the stand characteristics gradient and locations of the sample plots. Our study revealed that, forest patch size has greater influence on species richness. Areas with medium level of disturbances have shown greater species richness. In constrained ordination the selected explanatory variables regulated the richness of common species. Our findings can be useful for better forest management and restoration of landscapes of conservation needs using ecologically important species. 相似文献
184.
Guzel Danukalova Anatoly Yakovlev Liliana Alimbekova Tatyana Yakovleva Evgenija Morozova Andrey Eremeev Pavel Kosintsev 《Quaternary International》2008,190(1):38
Numerous caves and terraces with late Late Pleistocene (Upper Neopleistocene according to the Russian stratigraphic scale)–Holocene deposits are located in the Lemeza River valley in the surroundings of the Atysh waterfall, the native reserve territory of the Bashkortostan Republic. Lemeza River runs in the southern part of the western slope of the Urals and belongs to the Belaya River valley system (Russian Federation). A summary of the biostratigraphical investigations between 1992 and 2007 in this area is given. Deposits of cave and fluvial origin are characterized in the framework of the regional stratigraphy. The results of mammalian investigations and radiocarbon dating provide the basis for the stratigraphical subdivision. Palynology, mollusca, fishes, amphibian and reptiles are used for the reconstruction the palaeoenvironments. The Southern Urals stratigraphic subdivisions are correlated with Western European (Weichselian-Holocene), Eastern European (Russia) (Leningrad–Ostashkov–Shuvalov) and Uralian (Nevyansk–Polar Urals–Gorbunovsky) stratigraphic schemes. 相似文献
185.
186.
187.
Anomalous drip in the Punkva caves (Moravian Karst): relevant implications for paleoclimatic proxies 下载免费PDF全文
The anomalous drip in the Punkva caves (Moravian Karst) shows specific hydrogeochemical properties such as low SIcalcite ~ 0.14 ± 0.11 (standard deviation), low mineralization (4.53 ± 0.42) × 10?3 mol l?1, and enhanced values of δ13C (?7.85 to ?8.35‰ VPDB), Mg/Ca × 1000 ratio (45.7 ± 3.3), and Sr/Ca × 1000 ratio (0.65 ± 0.06). By these properties, the anomalous drip significantly differs from other regular drips in the same cave and other caves in the region. The study suggests that the anomalous drip properties are a consequence of prior calcite precipitation or/and water mixing along the water flow path. As the former processes are spatially controlled, the knowledge of dripwater flow path seems to be necessary for correct paleoclimatic/paleoenvironmental reconstructions. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
188.
Martin Novak Alexandre Andronikov Pavel Kram Jan Curik Frantisek Veselovsky Marketa Stepanova Eva Prechova Ondrej Sebek Leona Bohdalkova 《水文研究》2021,35(4):e14116
Data on temporal variability in Mg isotope ratios of atmospheric deposition and runoff are critical for decreasing the uncertainty associated with construction of isotope mass balances in headwater catchments, and statistical evaluation of isotope differences among Mg pools and fluxes. Such evaluations, in turn, are needed to distinguish between biotic and abiotic contributions to Mg2+ in catchment runoff. We report the first annual time-series of δ26Mg values simultaneously determined for rainfall, canopy throughfall, soil water and runoff. The studied 55-ha catchment, situated in western Czech Republic, is underlain by Mg-rich amphibolite and covered by mature spruce stands. Between 1970 and 1996, the site received extremely high amounts of acid deposition and fly ash form nearby coal-burning power plants. The δ26Mg values of open-area precipitation (median of −0.79‰) at our study site were statistically indistinguishable from the δ26Mg values of throughfall (−0.73‰), but significantly different from the δ26Mg values of soil water (−0.55‰) and runoff (−0.55‰). The range of δ26Mg values during the observation period decreased in the order: open-area precipitation (0.57‰) > throughfall (0.27‰) > runoff (0.21‰) > soil water (0.16‰). The decreasing variability in δ26Mg values of Mg2+ from precipitation to soil water and runoff reflected an increasing homogenization of atmospheric Mg in the catchment and its mixing with geogenic Mg. In addition to atmospheric Mg, runoff also contained Mg mobilized from the three major solid Mg pools, bedrock (δ26Mg of −0.32‰), soil (−0.28‰), and vegetation (−0.31‰). The drought of summer 2019 did not affect the nearly constant δ26Mg value of runoff. Collectively, our data show that within-catchment processes buffer the Mg isotope variability of the atmospheric input. 相似文献
189.
Dmitry Ponomarev Andrey Puzachenko Olga Bachura Pavel Kosintsev Johannes van der Plicht 《Boreas: An International Journal of Quaternary Research》2013,42(3):779-797
The paper summarises materials on the mammal remains in northeastern Europe, dated by radiocarbon. Altogether, 23 local faunas of small mammals and 47 local faunas of large mammals were analysed. Multidimensional statistical analysis shows a strong correlation between changes in small mammal fauna composition and climate changes throughout time. The correlations with the spatial gradients, however, are less pronounced. The faunas are classified into three groups: (1) faunas of Holocene age; (2) Late Pleistocene ‘stadial’ assemblages; and (3) Late Pleistocene ‘interstadial’ assemblages. In some cases, changes in species abundance are better understood in terms of biotic interrelations rather than of climatic effects. The most pronounced change in small mammal fauna composition and structure occurred at the Preboreal/Boreal boundary, and a less conspicuous alteration took place at the LGM/Lateglacial transition. The most noticeable transformation in the large mammal fauna composition is dated to the early Holocene. Less significant changes are observed at the Middle Weichselian/LGM transition and at the LGM/Lateglacial transition. It is safely concluded that variations in the faunas of small and large mammals recorded in NE Europe during the last 35 000 years occurred synchronously and unidirectionally. 相似文献
190.
Daniel N. Baker Dusan Odstrcil Brian J. Anderson C. Nick Arge Mehdi Benna George Gloeckler Haje Korth Leslie R. Mayer Jim M. Raines David Schriver James A. Slavin Sean C. Solomon Pavel M. Trávní?ek Thomas H. Zurbuchen 《Planetary and Space Science》2011,59(15):2066-2074
The second and third flybys of Mercury by the MESSENGER spacecraft occurred, respectively, on 6 October 2008 and on 29 September 2009. In order to provide contextual information about the solar wind properties and the interplanetary magnetic field (IMF) near the planet at those times, we have used an empirical modeling technique combined with a numerical physics-based solar wind model. The Wang–Sheeley–Arge (WSA) method uses solar photospheric magnetic field observations (from Earth-based instruments) in order to estimate the inner heliospheric radial flow speed and radial magnetic field out to 21.5 solar radii from the Sun. This information is then used as input to the global numerical magnetohydrodynamic model, ENLIL, which calculates solar wind velocity, density, temperature, and magnetic field strength and polarity throughout the inner heliosphere. WSA-ENLIL calculations are presented for the several-week period encompassing the second and third flybys. This information, in conjunction with available MESSENGER data, aid in understanding the Mercury flyby observations and provide a basis for global magnetospheric modeling. We find that during both flybys, the solar wind conditions were very quiescent and would have provided only modest dynamic driving forces for Mercury's magnetospheric system. 相似文献