全文获取类型
收费全文 | 632篇 |
免费 | 22篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 23篇 |
大气科学 | 28篇 |
地球物理 | 242篇 |
地质学 | 148篇 |
海洋学 | 4篇 |
天文学 | 187篇 |
自然地理 | 27篇 |
出版年
2021年 | 8篇 |
2020年 | 12篇 |
2019年 | 10篇 |
2018年 | 13篇 |
2017年 | 11篇 |
2016年 | 38篇 |
2015年 | 25篇 |
2014年 | 38篇 |
2013年 | 37篇 |
2012年 | 19篇 |
2011年 | 17篇 |
2010年 | 11篇 |
2009年 | 18篇 |
2008年 | 11篇 |
2007年 | 6篇 |
2006年 | 16篇 |
2005年 | 12篇 |
2003年 | 6篇 |
2002年 | 8篇 |
2000年 | 10篇 |
1999年 | 8篇 |
1997年 | 8篇 |
1996年 | 11篇 |
1995年 | 8篇 |
1994年 | 12篇 |
1993年 | 6篇 |
1992年 | 7篇 |
1991年 | 13篇 |
1990年 | 8篇 |
1989年 | 16篇 |
1988年 | 11篇 |
1987年 | 16篇 |
1986年 | 17篇 |
1985年 | 10篇 |
1984年 | 14篇 |
1983年 | 11篇 |
1982年 | 13篇 |
1981年 | 16篇 |
1980年 | 7篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 11篇 |
1973年 | 10篇 |
1972年 | 6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659条查询结果,搜索用时 46 毫秒
51.
Summary The paper deals with the solving of large systems of linear equations which are created when implicit and semi-implicit differential methods are used to solve the primitive equations of the atmosphere. Systems with similar properties are also created in solving boundary problems of multi-level filtered models. First, the specific properties of these systems, which are then used to construct an efficient method of solving them, are described. 相似文献
52.
53.
Rock displacement and thermal expansion study at historic heritage sites in Slovakia 总被引:1,自引:0,他引:1
Jan Vlcko Vladimir Greif Vladimir Grof Michal Jezny Lubomir Petro Martin Brcek 《Environmental Geology》2009,58(8):1727-1740
The paper discusses the results of the research devoted to the preservation of cultural heritage carried out within last two
decades in Slovakia. The aim of the study depended on monitoring of selected castle rocks showing instability problems due
to extremely slow displacements of creep character. Apart from traditional methods of investigation at one test site (Spis
Castle), authors implemented in their work the study of thermal expansion of the rocks as a result of seasonal periodic temperature
changes having potential influence on displacements and numerical modeling in order to understand better the landslide failure
mechanism. The results obtained from all study sites confirmed that even slow movements have to be implemented into preservation
and stabilization works in order to safeguard the sites of great historic value. 相似文献
54.
Josef Bochníček Jaroslav Šubrt Reviewer M. Hvoždara Reviewer J. Podlešák 《Studia Geophysica et Geodaetica》1971,15(1):76-85
Zusammenfassung Es wird eine Methode für experimentelle Untersuchung der Frequenzkennlinien von Induktionsvariometern mit Aufnahmeschleifen nichttraditioneller Ausmasse beschrieben. Die Grundlage des beschriebenen Verfahrens bildet eine genaue Bestimmung jenes Teils des magnetischen Kraftflusses, der durch die Aufnahmeschleife durchgeht. 相似文献
55.
During the last decades, several integrated studies of Tethyan Jurassic/Cretaceous boundary
sections from different countries were published with the objective to indicate problems for the selection
of biological, chemical or physical markers suitable for identification of the Jurassic/Cretaceous
boundary e the only system boundary within the Phanerozoic still not fixed by GSSP. Drawing the
boundary between the Jurassic and Cretaceous systems is a matter of global scale discussions. The
problem of proposing possible J/K boundary stratotypes results from lack of a global index fossils,
global sea level drop, paleogeographic changes causing development of isolated facies areas, as well
as from the effect of Late Cimmerian Orogeny. This contribution summarizes and comments data on
J/K boundary interval obtained from several important Tethyan sections and shows still existing problems
and discrepancies in its determination. 相似文献
56.
Ongonite from Ongon Khairkhan,Mongolia 总被引:2,自引:0,他引:2
Doz. Dr. M. Štemprok 《Mineralogy and Petrology》1991,43(4):255-273
Summary Albite-topaz kerotophyres, termed ongonites, were discovered byV. I. Kovalenko and coworkers at Ongon Khairkhan in Mongolia in 1970. The type area was revisited, described, resampled, the new data is compared with the earlier data and that from similar rocks elsewhere (Beauvoir and Cinovec granites; Macusani glass).Ongonites are fluorine-rich peraluminous sodic two feldspar granitoids with orthoclase and albite phenocrysts, high modal and normative albite content and the presence of topaz as common accessory mineral. They contain variable amounts of lithium micas or muscovite. Chemically, ongonite is similar to highly fractionated S-type or ilmenite series granitoids. In the type area, F-rich water-poor ongonite melts have intruded to a high crustal level.Ongonite displays a long history of subsolidus reactions and hydrothermal alteration. The hydrothermal alteration may be linked to a spatially associated quartz-wolframite stockwork not genetically related to ongonite. Ongonite has a low W content and an elevated Sn content despite a lack of association with Sn deposits.
Ongonite von Ongon Khairkhan, Mongolei
Zusammenfassung Albit-Topas-Keratophyre, auch als Ongonite bezeichnet, wurden 1970 von V. E. Kowalenko und Mitarbeitern bei Ongon Khairkhan in der Mongolei entdeckt. Die TypLokalität wurde beschrieben und beprobt und die neuen Daten werden mit den früher erhaltenen, und denen von ähnlichen Gesteinen in anderen Bereichen (die Granite von Beauvoir und Cinovec, das Glas von Macusani) verglichen.Ongonite sind Fluor- und Aluminiumreiche (Peraluminous), zwei-Feldspat-Natriumgranitoide mit idiomorphen Orthoklasen und Albit, hohem modalem und normativem Albitgehalt, und Topas als verbreitetem Nebenmineral. Sie führen wechselnde Gehalte von Lithiumglimmern oder Muskovit. Chemisch sind Ongonite stark fraktionierten S-Typ Granitoiden vergleichbar oder auch Granitoiden der Ilmenit-Serie. Im Gebiet der Typlokalität sind fluorreiche wasserarme Ongonit-Schmelzen in ein hohes Krustenniveau intrudiert worden.Ongonite zeigen eine lange Geschichte von Subsolidusreaktionen und hydrothermaler Umwandlung. Die hydrothermale Umwandlung kann mit einem räumlich assoziiertem Quarz-Wolframit Stockwerk in Beziehung gesetzt werden, das genetisch nicht mit den Ongoniten zusammenhängt. Ongonit hat einen niedrigen Wolframgehalt und einen erhöhten Zinngehalt, obwohl keine Assoziation mit Zinnlagerstätten zu beobachten ist.相似文献
57.
ELVIRA KOVAČ-ANDRIĆ ALAA SHETA HOSSAM FARIS MARTINA ŠRAJER GAJDOŠIK 《Journal of Earth System Science》2016,125(5):997-1006
Ozone is one of the most significant secondary pollutants with numerous negative effects on human health and environment including plants and vegetation. Therefore, more effort is made recently by governments and associations to predict ozone concentrations which could help in establishing better plans and regulation for environment protection. In this study, we use two Artificial Neural Network based approaches (MPL and RBF) to develop, for the first time, accurate ozone prediction models, one for urban and another one for rural area in the eastern part of Croatia. The evaluation of actual against the predicted ozone concentrations revealed that MLP and RBF models are very competitive for the training and testing data in the case of Kopa?ki Rit area whereas in the case of Osijek city, MLP shows better evaluation results with 9% improvement in the correlation coefficient. Furthermore, subsequent feature selection process has improved the prediction power of RBF network. 相似文献
58.
Biogeochemical processes were investigated in alpine river—Kamni?ka Bistrica River (North Slovenia), which represents an ideal natural laboratory for studying anthropogenic impacts in catchments with high weathering capacity. The Kamni?ka Bistrica River water chemistry is dominated by HCO3 ?, Ca2+ and Mg2+, and Ca2+/Mg2+ molar ratios indicate that calcite weathering is the major source of solutes to the river system. The Kamni?ka Bistrica River and its tributaries are oversaturated with respect to calcite and dolomite. pCO2 concentrations were on average up to 25 times over atmospheric values. δ13CDIC values ranged from ?12.7 to ?2.7 ‰, controlled by biogeochemical processes in the catchment and within the stream; carbonate dissolution is the most important biogeochemical process affecting carbon isotopes in the upstream portions of the catchment, while carbonate dissolution and organic matter degradation control carbon isotope signatures downstream. Contributions of DIC from various biogeochemical processes were determined using steady state equations for different sampling seasons at the mouth of the Kamni?ka Bistrica River; results indicate that: (1) 1.9–2.2 % of DIC came from exchange with atmospheric CO2, (2) 0–27.5 % of DIC came from degradation of organic matter, (3) 25.4–41.5 % of DIC came from dissolution of carbonates and (4) 33–85 % of DIC came from tributaries. δ15N values of nitrate ranged from ?5.2 ‰ at the headwater spring to 9.8 ‰ in the lower reaches. Higher δ15N values in the lower reaches of the river suggest anthropogenic pollution from agricultural activity. Based on seasonal and longitudinal changes of chemical and isotopic indicators of carbon and nitrogen in Kamni?ka Bistrica River, it can be concluded that seasonal changes are observed (higher concentrations are detected at low discharge conditions) and it turns from pristine alpine river to anthropogenic influenced river in central flow. 相似文献
59.
János Kovács Szabolcs Á. Fábián Gábor Varga Karoly Németh Corina Risso Francisco Nullo Gabor Kereszturi Titusz Bugya Szabolcs Á. Fábián Noémi L. Görcs István P. Kovács Bertalan Radvánszky Gabriella Barta Rudolf Musil Alice Ghiselli Marzio Merazzi Andrea Strini Roberto Margutti Michele Mercuriali Rauf Gardashov Daria Gushchina Boris Dewitte Martin Michálek Marián Putiš Christoph A. Hauzenberger Jindřich Šancer Martin Štrejbar Aneta Maleňáková George Migiros George D. Bathrellos Hariklia D. Skilodimou Theodoros Karamousalis 《Central European Journal of Geosciences》2011,3(2):229-229
60.
The paper considers a puff diffusion in its inertial stage when particle separation obeys the laws of the inertial subrange and depends only on eddy energy dissipation rate . The can be determined in the surface layer by the turbulent kinetic energy equation. Similarity equations connect with diffusion measure .A simple analytical model has been deduced to estimate pollutants diffusion during calms. 相似文献