全文获取类型
收费全文 | 570篇 |
免费 | 34篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 19篇 |
大气科学 | 21篇 |
地球物理 | 201篇 |
地质学 | 212篇 |
海洋学 | 16篇 |
天文学 | 99篇 |
综合类 | 6篇 |
自然地理 | 32篇 |
出版年
2023年 | 4篇 |
2022年 | 8篇 |
2021年 | 7篇 |
2020年 | 11篇 |
2019年 | 12篇 |
2018年 | 30篇 |
2017年 | 33篇 |
2016年 | 40篇 |
2015年 | 37篇 |
2014年 | 35篇 |
2013年 | 31篇 |
2012年 | 29篇 |
2011年 | 21篇 |
2010年 | 24篇 |
2009年 | 36篇 |
2008年 | 27篇 |
2007年 | 24篇 |
2006年 | 15篇 |
2005年 | 17篇 |
2004年 | 6篇 |
2003年 | 6篇 |
2002年 | 13篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1996年 | 8篇 |
1995年 | 4篇 |
1994年 | 6篇 |
1992年 | 7篇 |
1991年 | 4篇 |
1990年 | 7篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1970年 | 2篇 |
1968年 | 2篇 |
1962年 | 2篇 |
排序方式: 共有606条查询结果,搜索用时 15 毫秒
151.
Trends in water quality variations in the Odra River the day before implementation of the Water Framework Directive 总被引:1,自引:0,他引:1
This paper contains an account of UN/EEC-sponsored research on water quality monitoring and assessments in the catchments areas of Europe's 10 transboundary rivers. In this context, water quality assessments established on the basis of monitoring data for Poland's rivers are discussed. Consideration is also given to the water quality assessment methods recommended by the EU Directives. The problem has been exemplified by the analysis of water quality variations in the transboundary river Odra in the time span of 1973–2003. For the years 1993–2003, the trends in water quality variations are calculated and the rates of variation are analysed. The points in time when the water quality will have attained the second class purity values are predicted, taking into account the requirements specified in Polish, Czech and German standards. Analysis of the trends in the variations of pollution parameters has revealed that the achievability of good water quality depends on the limit values adopted for the assessment. 相似文献
152.
Aleksandra Stachowska Maciej Łoziński Michał Śmigielski Anna Wysocka Leszek Jankowski Piotr Ziółkowski 《Sedimentology》2020,67(7):3783-3808
The anisotropy of magnetic susceptibility is a well-known geological proxy in revealing the directional tectonic and sedimentological features of rocks, although it can be ambiguous in situations where these two factors co-occur. This paper demonstrates the usefulness of the anisotropy of magnetic susceptibility in determining palaeotransport directions in turbiditic rocks that underwent subsequent thrusting and folding. This study demonstrates that the magnetic lineation is largely unsuitable as a palaeocurrent direction proxy, and suggests that the imbrication of magnetic foliation is better in such cases. Moreover, the anisotropy of magnetic susceptibility results were analyzed in reference to a joint and fold study within the framework of the regional structural geology. Magnetic fabric investigations were conducted in the eastern part of the Outer Western Carpathians (south-east Poland). During the study, a total of 191 oriented palaeomagnetic samples were collected from three outcrops (Nasiczne, Dwernik and Hoczew) in the Krosno Beds, Silesian Unit. For the purpose of sedimentological analysis, 121 m of turbidite successions were documented and 126 directional sedimentary structures were measured. The magnetic anisotropy of sandstones revealed typical sedimentary fabrics, often overprinted by variably intense tectonic deformation. Oblate susceptibility ellipsoids from Nasiczne showed tilt coherent with the palaeoflow direction, whereas the rocks from Dwernik and Hoczew contained triaxial magnetic fabric developed during compressional palaeostress. This paper suggests that medium-grained and coarse-grained sandstones, preferably with high mica content, are the most suitable for palaeotransport reconstructions among the studied lithologies. 相似文献
153.
154.
M. Siarkowski J. Sylwester J. Bąkała Ż. Szaforz M. Kowaliński Z. Kordylewski S. Płocieniak P. Podgórski B. Sylwester W. Trzebiński M. Stȩślicki K. J. H. Phillips O. V. Dudnik E. Kurbatov V. D. Kuznetsov S. Kuzin I. V. Zimovets 《Experimental Astronomy》2016,41(3):327-350
Interhelioprobe (IHP), an analogue to the ESA Solar Orbiter, is the prospective Russian space solar observatory intended for in-situ and remote sensing investigations of the Sun and the inner heliosphere from a heliocentric orbit with the perihelion of about 60 solar radii. One of several instruments on board will be the Bragg crystal spectrometer ChemiX which will measure X-ray spectra from solar corona structures. Analysis of the spectra will allow the determination of the elemental composition of plasma in hot coronal sources like flares and active regions. ChemiX is under development at the Wroc?aw Solar Physics Division of the Polish Academy of Sciences Space Research Centre in collaboration with an international team (see the co-author list). This paper gives an overview of the ChemiX scientific goals and design preparatory to phase B of the instrument development. 相似文献
155.
River pollution data are characterized by high variability. Multivariate statistical methods help to determine a complex set of these multidimensional data and to extract latent information (e.g. differently polluted areas, discharges). The chemometric methods can handle interactions between different pollutants and relationships among various sampling locations. This study presents an application of multivariate data analysis in the field of environmental pollution. The dataset consists of As, Cd, Cr, Cu, Fe, Ni, Mn, Pb and Zn contents of sediment samples collected in the upper and middle Odra River (Poland) in three sampling campaigns (November 1998, June 1999, and May 2000). As chemometric tools cluster analysis (CA), multivariate analysis of variance and discriminant analysis (MVDA) and factor analysis (FA) were used to investigate the matrix of 60 sampling points. 相似文献
156.
A detailed analysis of the short and medium term dynamics of the carbon exchange between the Baltic Sea and the North Sea is presented. To quantify the carbon fluxes distinguishing the Baltic and North Sea water masses, the salinity-based End Members (EM) method was successfully applied. The results of 0.63±0.25×1012 mol C year−1 identify the Baltic Sea as a net source of carbon for the North Sea. Dissolved organic carbon (DOC) was found to contribute significantly (22%) to the bulk of exported carbon. The levels determined suggest the hydrology-dependence of the carbon fluxes in the Danish Straits, which stimulates the high variability of carbon fluxes at both interseasonal and interannual scales. 相似文献
157.
In the mid-mountains of Central Europe relict forms of periglacial morphogenesis occur, including debris slope covers. However, the Holocene forest succession limited sediment transfer towards valley systems.The eastern, mid-mountain part of the Sudetes, characterised by a dense stream network and by the local occurrence of metallic and gold ores, was already settled by humans in early medieval times. Timber from the forested slopes was used to produce charcoal and streams acted as energy sources for smelting plants and smithies. Agriculture developed on less inclined slopes. Temporal clearances on steep slopes and replacement of primeval beech forest by spruce trees, influenced water circulation on slopes. The exposed slope covers were transferred to valley floors during high precipitation events. Consequently, they were selectively redeposited within the floodplain, changing the former channel pattern, especially at confluences. The introduction of cultivation on slopes triggered intense soil erosion so that agricultural terraces were built in order to prevent surface wash. The terraces are often strengthened with stone walls up to 4.5 m high. Terraces acted as ‘sediment traps’, storing the washed material within the slope. The layers of fine-grained colluvial sediments, which can be linked with agriculture, cover the older, debris slope covers. The colluvium is especially thick at the terrace edges. Despite the protective role of terracing, part of the washed material was transferred to valleys, often becoming overbank deposits, covering older gravel and boulder alluvium. The decline of iron ore exploitation and processing, at the beginning of the 19th century, together with agricultural withdrawal, which was especially radical after the 2nd World War, resulted in successive renaturalisation of the environment being followed by slope stabilisation and deepening of bigger river channels.The results led to the conclusion that a strong human impact on the slope–valley system in the mid-mountain part of the Eastern Sudetes influenced changes in the dynamics and morphology of small rivers to a much higher extent than the climate variations, especially during the Little Ice Age. 相似文献
158.
Mariusz Majdański 《Acta Geophysica》2012,60(1):59-75
A precise 3D model of the crust is necessary to start any tectonic or geodynamic interpretation. It is also essential for
seismic interpretations of structures lying below as well as for correct analysis of shallow structures using reflection seismics.
During the last decades, a number of wide-angle refraction experiments were performed on the territory of central and eastern
Europe (POLONAISE’97, CELEBRATION 2000, SUDETES 2003), resulting in many high quality 2D models. It is an interesting and
complicated transition zone between Precambrian and Palaeozoic Platforms. This paper presents 3D model of the velocity distribution
in the crust and upper mantle interpolated from 2D models of the structure along 33 profiles. The obtained model extends to
a depth of 50 km and accurately describes the main features of the crustal structures of Poland and surrounding areas. Different
interpolation techniques (Kriging, linear) are compared to assure maximum precision. The final model with estimated uncertainty
is an interesting reference of the area for other studies. 相似文献
159.
New photoelectric observations of CK Bootis (a binary star suspected of a spot activity) obtained in 1988 at Mt. Suhora Observatory are presented. On the basis of the spectroscopic observations made in May 1990 at the Toru University Observatory the spectral class F6V of the primary component was estimated. The physical parameters of the system with a circular spot were derived making use of the Wilson-Devinney code. 相似文献
160.
A 3D Lagrangian model of the saltation of solid spherical particles on the bed of an open channel flow, accounting for turbulence-induced mechanisms, is proposed and employed as the key tool of the study. The differences between conventional 2D models and a proposed 3D saltation model are discussed and the advantages of the 3D model are highlighted. Particularly, the 3D model includes a special procedure allowing generation of 3D flow velocity fields. This procedure is based on the assumption that the spectra of streamwise, vertical and transverse velocity components are known at any distance from the bed. The 3D model was used to identify and quantify effects of turbulence on particle entrainment and saltation. The analysis of particle trajectories focused on their diffusive nature, clarifying: (i) the effect of particle mobility parameter; (ii) the effect of bed topography; and (iii) the effect of turbulence. Specifically, the results of numerical simulations describing the abovementioned effects on the change in time of the variance are presented. In addition, the change in time of the skewness and kurtosis, which are likely to reflect the turbulence influence on the spread of particles, are also shown. Two different diffusion regimes (local and intermediate) for each of the investigated flow conditions are confidently identified. 相似文献