全文获取类型
收费全文 | 79篇 |
免费 | 3篇 |
专业分类
测绘学 | 1篇 |
大气科学 | 10篇 |
地球物理 | 16篇 |
地质学 | 22篇 |
海洋学 | 13篇 |
天文学 | 11篇 |
自然地理 | 9篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 1篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 5篇 |
2015年 | 3篇 |
2014年 | 3篇 |
2013年 | 4篇 |
2012年 | 1篇 |
2011年 | 3篇 |
2010年 | 4篇 |
2009年 | 6篇 |
2008年 | 4篇 |
2007年 | 5篇 |
2006年 | 6篇 |
2005年 | 3篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2002年 | 3篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1984年 | 1篇 |
1978年 | 1篇 |
1968年 | 1篇 |
1961年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有82条查询结果,搜索用时 31 毫秒
71.
Hurai Vratislav Huraiová Monika Gajdošová Michaela Konečný Patrik Slobodník Marek Siegfried Pete R. 《Mineralogy and Petrology》2018,112(3):279-296
Mineralogy and Petrology - Zirconolite is documented from the Evate apatite-magnetite-carbonate deposit in the circular Monapo Klippe (eastern Mozambique)—a relic of Neoproterozoic nappe... 相似文献
72.
Marco Conedera Willy Tinner Christophe Neff Manfred Meurer Angela F. Dickens Patrik Krebs 《Quaternary Science Reviews》2009,28(5-6):555-576
Biomass burning and resulting fire regimes are major drivers of vegetation changes and of ecosystem dynamics. Understanding past fire dynamics and their relationship to these factors is thus a key factor in preserving and managing present biodiversity and ecosystem functions. Unfortunately, our understanding of the disturbance dynamics of past fires is incomplete, and many open questions exist relevant to these concepts and the related methods. In this paper we describe the present status of the fire-regime concept, discuss the notion of the fire continuum and related proxies, and review the most important existing approaches for reconstructing fire history at centennial to millennial scales. We conclude with a short discussion of selected directions for future research that may lead to a better understanding of past fire-regime dynamics. In particular, we suggest that emphasis should be laid on (1) discriminating natural from anthropogenic fire-regime types, (2) improving combined analysis of fire and vegetation reconstructions to study long-term fire ecology, and (3) overcoming problems in defining temporal and spatial scales of reference, which would allow better use of past records to gain important insights for landscape, fire and forest management. 相似文献
73.
O. Karlsson 《Astronomische Nachrichten》2011,332(6):562-579
An investigation is carried out looking at correlations between the orbital elements of collisional targets and projectiles, estimating the number of interlopers in Trojan collisional families, and at the possibility of determining the ages of the Jupiter Trojan families by orbital integration. Real Trojans are integrated and close encounters are recorded in order to evaluate collisional circumstances between Trojans. Fictitious collisional families are created and integrated for 10 MJyr (million Julian years) forward in time and back again to the time of the collision in order to check the performance of the integrator, and the behaviour of the fictitious collisional fragments. Proper elements are calculated for the detection of family clustering using the hierarchically clustering method. This method presents little difficulty finding fictitious families in the Trojan swarms even in areas with densely populated backgrounds. However, even when the background is relatively sparse in objects, several interlopers can be connected to the family at velocity differences below 100 m s–1. On the other hand, in densely populated backgrounds the contamination of interlopers should be less than 30%. Providing gravity is the only significant force acting on the Trojans and resonance effects are weak, the shape the collision fragments create in the proper element space are preserved on the GJyr scale, and collisions can be tracked with orbital integrations for ages of at least 100 MJyr. However, the shape of artificial families does not correspond to suggested real families. This points to the need of including non‐gravitational forces such as the Yarkovsky effect in order to simulate the family evolution. As a consequence age determination by orbital integration might be severely restricted and previous investigations involving long term orbital integrations might have tobe recalculated (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
74.
75.
Chloride retention in forest soil by microbial uptake and by natural chlorination of organic matter 总被引:2,自引:0,他引:2
David Bastviken Frida Thomsen Susanne Karlsson George Shaw Gunilla Öberg 《Geochimica et cosmochimica acta》2007,71(13):3182-3192
Inorganic chlorine (i.e. chloride; Clin) is generally considered inert in soil and is often used as a tracer of soil and ground water movements. However, recent studies indicate that substantial retention or release of Clin can occur in soil, but the rates and processes responsible under different environmental conditions are largely unknown. We performed 36Cl tracer experiments which indicated that short-term microbial uptake and release of Clin, in combination with more long-term natural formation of chlorinated organic matter (Clorg), caused Clin imbalances in coniferous forest soil. Extensive microbial uptake and release of Clin occurred over short time scales, and were probably associated with changes in environmental conditions. Up to 24% of the initially available Clin within pore water was retained by microbial uptake within a week in our experiments, but most of this Clin was released to the pore water again within a month, probably associated with decreasing microbial populations. The natural formation of Clorg resulted in a net immobilization of 4% of the initial pore water Clin over four months. If this rate is representative for the area where soil was collected, Clorg formation would correspond to a conversion of 25% of the yearly wet deposition of Clin. The study illustrates the potential of two Clin retaining processes in addition to those previously addressed elsewhere (e.g. uptake of chloride by vegetation). Hence, several processes operating at different time scales and with different regulation mechanisms can cause Clin imbalances in soil. Altogether, the results of the present study (1) provide evidence that Clin cannot be assumed to be inert in soil, (2) show that microbial exchange can regulate pore water Clin concentrations and (3) confirm the controversial idea of substantial natural chlorination of soil organic matter. 相似文献
76.
Vratislav Hurai Klaus Simon Uwe Wiechert Jochen Hoefs Patrik Konečný Monika Huraiová Jacques Pironon Jozef Lipka 《Contributions to Mineralogy and Petrology》1998,133(1-2):12-29
Globules of iron-dominated (59–69 wt% FeOtot) and titanium-dominated (43.5 wt% TiO2) oxide melts have been detected in igneous xenoliths from Pliocene-to-Pleistocene alkali basalts of the Western Carpathians.
Fluid inclusion and mineral composition data indicate immiscible separation of the high-iron-oxide melt (HIM) at magmatic
temperatures. The HIM separation occurred during clinopyroxene (augite) accumulation in an alkali trachybasalt and continued
during crystallization of amphibole (kaersutite) and K-feldspar (anorthoclase), the latter coexisting with trachyte and alkalic
rhyolite residual melts. Some HIM was also expelled from sub-alkalic rhyolite (70–77% SiO2), coexisting with An27–45 plagioclase and quartz in granitic (tonalite-trondhjemite) xenoliths. Oxygen fugacities during HIM separation range from
−1.4 to +0.6 log units around the QFM buffer. A close genetic relationship between HIM-hosted xenoliths and mantle-derived
basaltic magma is documented by mineral 18O values ranging from 4.9 to 5.9‰ V-SMOW. δD values of gabbroic kaersutite between −61 and −86‰ V-SMOW are in agreement with
a presumed primary magmatic water source. Most trace elements, except Li, Rb and Cs, have preferentially partitioned into
the HIM. The HIM/Si-melt partition coefficients for transition elements (Sc, V, Cr, Co, Ni) and base metals (Zn, Cu, Mo) are
between 2–160, resulting in extreme enrichment in the HIM. La and Ce also concentrate in the silicic melt, whereas Tb-Tm in
the HIM. Hence, the immiscible separation causes REE fractionation and produces residual silicic melt enriched in LREE and
depleted in HREE. The weak fractionation among Tb-Tm and Yb, Lu can be attributed to recurrent extraction of the HIM from
the magmatic system, while flat HREE chondrite-normalized patterns are interpreted to indicate no or little loss of the HIM.
Received: 30 September 1997 / Accepted: 23 March 1998 相似文献
77.
M. Wallgren C. Skarpe R. Bergström K. Danell A. Bergström T. Jakobsson K. Karlsson T. Strand 《Journal of Arid Environments》2009,73(3):314-321
Human land use such as pastoralism may be a key determinant of wildlife populations. We studied the influence of land use on wildlife and livestock in south-western Kalahari, Botswana, during the wet and dry seasons. We included two types of livestock areas and two types of wildlife protection areas. Wild and domestic mammals >0.2 kg were sampled by distance technique. Small mammals <0.2 kg were trapped and a vegetation survey was performed. Livestock and some medium-sized wildlife species were most abundant in livestock areas, while large-sized wildlife species were mainly restricted to wildlife areas. Most red-listed species were confined to the national park. The influence of land use on abundances changed moderately between seasons. However, cattle moved into wildlife areas during the wet season. Differences in species richness and diversity were most pronounced during the dry season. The trapping frequency of small mammals was highest in the national park. Differences in vegetation structure included sparser field layer and higher cover of an invasive shrub in livestock areas. Our study shows the importance of protected areas for many wildlife species in the Kalahari. It also shows the value of a multi-species approach for investigating the effects of land use on wildlife communities. 相似文献
78.
G. Hahn C.‐I. Lagerkvist O. Karlsson T. Oja R. M. Stoss 《Astronomische Nachrichten》2006,327(1):17-20
The newly discovered periodic comet P/2004 A1 (LONEOS) is found to have experienced a recent capture into its present orbit, following a close approach to Saturn in 1992 to within 0.032 AU. This induced orbital change transfered the comet into an orbit tangent to that of Jupiter, which will, after a close passage in 2026, gain control by further decoupling it from the influence of Saturn. A long‐term orbital investigation yields support that the comet is on its first sojourn into the inner solar system. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
79.
Marco Eimermann Svante Karlsson 《Norsk geografisk tidsskrift. Norwegian journal of geography》2018,72(2):82-96
The main purpose of the article is to connect rural immigrants’ business ventures and development in Sweden to relational perspectives on their proximate and distant family and co-ethnic networks at structural and individual levels. Accordingly, the authors employ a relational approach and draw on in-depth interviews. In the context of urban–rural relationships’ meanings for the restaurateurs’ business benefits and constraints, they address two questions: (1) What does embeddedness in proximate and distant family and co-ethnic networks mean for the interviewed restaurateurs and for their businesses? and (2) How do previous and anticipated transitions in the restaurateurs’ families influence their business decisions and migration trajectories? The results suggest that the interviewees employed transnational dimensions in their social embeddedness and that they maintained material and emotional relationships with their countries of origin. This relational approach thus contributes to a better understanding of what the studied businesses mean for the entrepreneurs and the selected localities. The restaurateurs contribute to a globalisation of Swedish countrysides, but their socio-economic potential for countering rural depopulation in Sweden is not fully realised. Additionally, the study illuminates how individuals influence, and are influenced by, place-to-place mobilities on a daily basis and during their life course. 相似文献
80.
Andrej Osterman Lucas Benedičič Patrik Ritoša 《International journal of geographical information science》2014,28(11):2304-2327
A rapid and flexible parallel approach for viewshed computation on large digital elevation models is presented. Our work is focused on the implementation of a derivate of the R2 viewshed algorithm. Emphasis has been placed on input/output (IO) efficiency that can be achieved by memory segmentation and coalesced memory access. An implementation of the parallel viewshed algorithm on the Compute Unified Device Architecture (CUDA), which exploits the high parallelism of the graphics processing unit, is presented. This version is referred to as r.cuda.visibility. The accuracy of our algorithm is compared to the r.los R3 algorithm (integrated into the open-source Geographic Resources Analysis Support System geographic information system environment) and other IO-efficient algorithms. Our results demonstrate that the proposed implementation of the R2 algorithm is faster and more IO efficient than previously presented IO-efficient algorithms, and that it achieves moderate calculation precision compared to the R3 algorithm. Thus, to the best of our knowledge, the algorithm presented here is the most efficient viewshed approach, in terms of computational speed, for large data sets. 相似文献