全文获取类型
收费全文 | 1001篇 |
免费 | 62篇 |
国内免费 | 13篇 |
专业分类
测绘学 | 50篇 |
大气科学 | 160篇 |
地球物理 | 222篇 |
地质学 | 432篇 |
海洋学 | 47篇 |
天文学 | 91篇 |
综合类 | 2篇 |
自然地理 | 72篇 |
出版年
2023年 | 6篇 |
2022年 | 7篇 |
2021年 | 23篇 |
2020年 | 29篇 |
2019年 | 24篇 |
2018年 | 54篇 |
2017年 | 30篇 |
2016年 | 54篇 |
2015年 | 35篇 |
2014年 | 51篇 |
2013年 | 67篇 |
2012年 | 54篇 |
2011年 | 64篇 |
2010年 | 54篇 |
2009年 | 81篇 |
2008年 | 60篇 |
2007年 | 41篇 |
2006年 | 50篇 |
2005年 | 39篇 |
2004年 | 39篇 |
2003年 | 33篇 |
2002年 | 16篇 |
2001年 | 18篇 |
2000年 | 16篇 |
1999年 | 13篇 |
1998年 | 18篇 |
1997年 | 13篇 |
1996年 | 7篇 |
1995年 | 9篇 |
1994年 | 5篇 |
1993年 | 8篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1987年 | 6篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1974年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1969年 | 5篇 |
1968年 | 3篇 |
1967年 | 4篇 |
1964年 | 1篇 |
排序方式: 共有1076条查询结果,搜索用时 15 毫秒
831.
832.
Alexa M. Hinzman Ylva Sjöberg Steve W. Lyon Stefan W. Ploum Ype van der Velde 《水文研究》2020,34(19):3894-3909
The Arctic is warming at an unprecedented rate. We hypothesis that as seasonally frozen soils thaw and recede in extent as a response to this warming, flow path diversity and thus hydrologic connectivity increases. This enhanced hydrologic connectivity then increases the non-linearity of the storage-discharge relationship in a catchment. The objective of this study is to test this hypothesis by quantifying trends and spatio-temporal differences in the degree of linearity in the storage-discharge relationships for 16 catchments within Northern Sweden from 1950 to 2018. We demonstrate a clear increase in non-linearity of the storage-discharge relationship over time for all catchments with 75% showing a statistically significant increase in non-linearity. Spring has significantly more linear storage-discharge relationships than summer for most catchments (75%) supporting the idea that seasonally frozen soils with a low degree of hydrological connectivity have a linear storage-discharge relationship. For the period considered, spring also showed greater change in storage-discharge relationship trends than summer signifying that changes in recessions are primarily occurring during the thawing period. Separate storage-discharge analyses combined with preceding winter conditions demonstrated that especially cold winters with little snow yielded springs and summers with more linear storage-discharge relationships. We show that streamflow recession analysis reflects ongoing hydrological change of an arctic landscape as well as offering new metrics for tracking change across arctic and sub-arctic landscapes. 相似文献
833.
Lenstra Klaas J. H. Pluis Stefan R. P. M. Ridderinkhof Wim Ruessink Gerben van der Vegt Maarten 《Ocean Dynamics》2019,69(4):409-425
Ocean Dynamics - Ebb-tidal deltas are shallow features seaward of tidal inlets, acting as a wave filter for the nearby barrier island and a source of sediment for the landward tidal basin. On many... 相似文献
834.
Vertical–vertical controlled-source electromagnetic is an alternative to other techniques for providing three-dimensional resistivity images of the subsurface. It utilizes a large and powerful vertical dipole transmitter and arrays of E-field receivers with vertical and horizontal dipole sensors. The necessary instrumentation and acquisition procedures which differ strongly from other controlled-source electromagnetic methods are described in the paper. 相似文献
835.
J. Douglas Zechar Warner Marzocchi Stefan Wiemer 《Bulletin of Earthquake Engineering》2016,14(9):2459-2469
Is Europe-wide operational earthquake forecasting (OEF) possible? We discuss the myriad problems that prevent it today, many of which relate to heterogeneities in earthquake recording, processing, and reporting. We contemplate the difficulty of building models that cross political boundaries, and we consider the prospect of European OEF in light of recent efforts to harmonize long-term seismic hazard assessment among several nations. Emphasizing the Strategies and Tools for Real-time Earthquake Risk Reduction (REAKT) project, we report achievements related to short-term seismicity forecasting in Iceland and Italy that could apply elsewhere in Europe. In Iceland, collaboration fostered by REAKT resulted in a revised earthquake catalog and a prototype OEF system. We report results from an experiment conducted with this prototype; these results suggest ensemble models provide an information gain, updating models more frequently improves their forecast skill, and that OEF is computationally feasible. In Italy, REAKT supported the creation of an ensemble model that now issues weekly hazard forecasts. We present examples of these forecasts, highlighting the problem that OEF often yields low probabilities, which are difficult to interpret and convert into actionable decisions. Motivated by such low hazard probabilities, we highlight Europe’s pioneering efforts in operational earthquake loss forecasting and mention solutions to problems that currently prevent OEF at the European scale. 相似文献
836.
The 2013 European Seismic Hazard Model: key components and results 总被引:11,自引:5,他引:6
Jochen Woessner Danciu Laurentiu Domenico Giardini Helen Crowley Fabrice Cotton Gottfried Grünthal Gianluca Valensise Ronald Arvidsson Roberto Basili Mine Betül Demircioglu Stefan Hiemer Carlo Meletti Roger W. Musson Andrea N. Rovida Karin Sesetyan Massimiliano Stucchi The SHARE Consortium 《Bulletin of Earthquake Engineering》2015,13(12):3553-3596
837.
A video-based technique for mapping intertidal beach bathymetry 总被引:2,自引:0,他引:2
Stefan G. J. Aarninkhof Ian L. Turner Thomas D. T. Dronkers Mark Caljouw Leann Nipius 《Coastal Engineering》2003,49(4):275
Measuring the location of the shoreline and monitoring foreshore changes through time are core tasks carried out by coastal engineers for a wide range of research, monitoring and design applications. With the advent of digital imaging technology, shore-based video systems provide continuous and automated data collection, encompassing a much greater range of time and spatial scales than were previously possible using field survey methods.A new video-based technique is presented that utilises full-colour image information, which overcomes problems associated with previous grey-scale methods, which work well at steep (reflective) sites, but are less successful at flatter (dissipative) sites. Identification of the shoreline feature is achieved by the automated clustering of sub-aqueous and sub-aerial pixels in ‘Hue–Saturation–Value’ (HSV) colour space, and applying an objective discriminator function to define their boundary (i.e., ‘shoreline’) within a time-series of consecutive geo-referenced images. The elevation corresponding to the detected shoreline features is calculated on the basis of concurrent tide and wave information, which is incorporated in a model that combines the effects of wave set-up and swash, at both incident and infragravity frequencies.Validation of the technique is achieved by comparison with DGPS survey results, to assess the accuracy of the detection and elevation methods both separately and together. The uncertainties associated with the two sub-components of the model tend to compensate for each other. The mean difference between image-based and surveyed shoreline elevations was less than 15 cm along 85% of the 2-km study region, which corresponded to an horizontal offset of 6 m. The application of the intertidal bathymetry mapping technique in support of CZM objectives is briefly illustrated at two sites in The Netherlands and Australia. 相似文献
838.
We calculate the transport coefficients of low-density nuclear matter, especially the nuclear pasta phase, using quantum molecular dynamics simulations. The shear viscosity as well as the thermal and electrical conductivities are determined by calculating the static structure factor of protons for all relevant density, temperature and proton fractions, using simulation data. It is found that all the transport coefficients have similar orders of magnitude as found earlier without considering the pasta phase. Our results are thus in contrast to the common belief that the pasta layer is highly resistive and therefore have important astrophysical consequences. 相似文献
839.
Hannes Taubenböck Michael Wurm Christian Geiß Stefan Dech Stefan Siedentop 《International Journal of Digital Earth》2019,12(6):679-698
Measuring spatial patterns is a crucial task in spatial sciences. Multiple indicators have been developed to measure patterns in a quantitative manner. However, most comparative studies rely on relative comparisons, limiting their explanatory power to specific case studies. Motivated by advancements in earth observation providing unprecedented resolutions of settlement patterns, this paper suggests a measurement technique for spatial patterns to overcome the limits of relative comparisons. We design a model spanning a feature space based on two metrics – largest patch index and number of patches. The feature space is defined as ‘dispersion index’ and covers the entire spectrum of possible two-dimensional binary (settlement) patterns. The model configuration allows for an unambiguous ranking of each possible pattern with respect to spatial dispersion. As spatial resolutions of input data as well as selected areas of interest influence measurement results, we test dependencies within the model. Beyond, common other spatial metrics are selected for testing whether they allow unambiguous rankings. For scenarios, we apply the model to artificially generated patterns representing all possible configurations as well as to real-world settlement classifications differing in growth dynamics and patterns. 相似文献
840.
Ingo Leya Jean‐Christophe David Thomas Faestermann Michaela Froehlich Niko Kivel Dominik Koll Gunther Korschinek Sarah McIntyre Silke Merchel Stefan Pavetich Georg Rugel Dorothea Schumann Thomas Smith Anton Wallner 《Meteoritics & planetary science》2020,55(4):818-831
We measured specific activities of the long‐lived cosmogenic radionuclides 60Fe in 28 iron meteorites and 53Mn in 41 iron meteorites. Accelerator mass spectrometry was applied at the 14 MV Heavy Ion Accelerator Facility at ANU Canberra for all samples except for two which were measured at the Maier‐Leibnitz Laboratory, Munich. For the large iron meteorite Twannberg (IIG), we measured six samples for 53Mn. This work doubles the number of existing individual 60Fe data and quadruples the number of iron meteorites studied for 60Fe. We also significantly extended the entire 53Mn database for iron meteorites. The 53Mn data for the iron meteorite Twannberg vary by more than a factor of 30, indicating a significant shielding dependency. In addition, we performed new model calculations for the production of 60Fe and 53Mn in iron meteorites. While the new model is based on the same particle spectra as the earlier model, we no longer use experimental cross sections but instead use cross sections that were calculated using the latest version of the nuclear model code INCL. The new model predictions differ substantially from results obtained with the previous model. Predictions for the 60Fe activity concentrations are about a factor of 2 higher, for 53Mn, they are ~30% lower, compared to the earlier model, which gives now a better agreement with the experimental data. 相似文献