全文获取类型
收费全文 | 607篇 |
免费 | 43篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 15篇 |
大气科学 | 44篇 |
地球物理 | 174篇 |
地质学 | 198篇 |
海洋学 | 84篇 |
天文学 | 105篇 |
综合类 | 2篇 |
自然地理 | 32篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 4篇 |
2021年 | 18篇 |
2020年 | 20篇 |
2019年 | 18篇 |
2018年 | 32篇 |
2017年 | 34篇 |
2016年 | 35篇 |
2015年 | 29篇 |
2014年 | 28篇 |
2013年 | 42篇 |
2012年 | 33篇 |
2011年 | 54篇 |
2010年 | 30篇 |
2009年 | 48篇 |
2008年 | 47篇 |
2007年 | 35篇 |
2006年 | 19篇 |
2005年 | 19篇 |
2004年 | 15篇 |
2003年 | 15篇 |
2002年 | 14篇 |
2001年 | 6篇 |
2000年 | 8篇 |
1999年 | 10篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1986年 | 1篇 |
1983年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1973年 | 2篇 |
1971年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有654条查询结果,搜索用时 15 毫秒
271.
Ulrich Grossmann-Doerth Franz Kneer Marina V. Uexküll Guy E. Artzner Jean Claude Vial 《Solar physics》1980,66(1):3-12
The line profiles of L, Ca ii K and Mg iik were measured with the spectrometer of the Laboratoire de Physique Stellaire et Planétaire on board of OSO-8. The results of these measurements are presented.Mitteilungen aus dem Kiepenheuer-Institut Nr. 181. 相似文献
272.
Julio R. Gutiérrez Francisco López-Cortes Pablo A. Marquet 《Journal of Arid Environments》1998,40(4):383-399
Six sites between 0 m and 4000 m were sampled for plant and soil chemical characteristics along the Río Loa, Atacama Desert, Chile. Sites located between 0 m and 1500 m showed lower species richness, higher plant cover and higher herbaceous productivity than the upper part of the altitudinal gradient. The number of species varied non-linerly with precipitation along the altitudinal gradient. Plant cover and herbaceous productivity in the lowlands is characterized by thePluchea absinthioides Distichlis spicataassociation of anthropic origin. We propose that vegetation structure along the altitudinal gradient has been affected by past and present human activities, and climatic and edaphic factors. 相似文献
273.
Pablo Fosalba & Enrique Gaztañaga 《Monthly notices of the Royal Astronomical Society》1998,301(2):503-523
We present a simple and intuitive approximation for solving the perturbation theory (PT) of small cosmic fluctuations. We consider only the spherically symmetric or monopole contribution to the PT integrals, which yields the exact result for tree-graphs (i.e. at leading order). We find that the non-linear evolution in Lagrangian space is then given by a simple local transformation over the initial conditions, although it is not local in Euler space. This transformation is found to be described by the spherical collapse (SC) dynamics, as it is the exact solution in the shearless (and therefore local) approximation in Lagrangian space. Taking advantage of this property, it is straightforward to derive the one-point cumulants, ξJ , for both the unsmoothed and smoothed density fields to arbitrary order in the perturbative regime. To leading-order this reproduces, and provides us with a simple explanation for, the exact results obtained by Bernardeau. We then show that the SC model leads to accurate estimates for the next corrective terms when compared with the results derived in the exact perturbation theory making use of the loop calculations. The agreement is within a few per cent for the hierarchical ratios S J = ξ J /ξ J −1 2 . We compare our analytic results with N -body simulations, which turn out to be in very good agreement up to scales where σ ≈ 1. A similar treatment is presented to estimate higher order corrections in the Zel'dovich approximation. These results represent a powerful and readily usable tool to produce analytical predictions that describe the gravitational clustering of large-scale structure in the weakly non-linear regime. 相似文献
274.
Enrique Gaztañaga & Pablo Fosalba 《Monthly notices of the Royal Astronomical Society》1998,301(2):524-534
In Paper I of this series, we introduced the spherical collapse (SC) approximation in Lagrangian space as a way of estimating the cumulants ξ J of density fluctuations in cosmological perturbation theory (PT). Within this approximation, the dynamics is decoupled from the statistics of the initial conditions, so we are able to present here the cumulants for generic non-Gaussian initial conditions, which can be estimated to arbitrary order including the smoothing effects. The SC model turns out to recover the exact leading-order non-linear contributions up to terms involving non-local integrals of the J -point functions. We argue that for the hierarchical ratios S J , these non-local terms are subdominant and tend to compensate each other. The resulting predictions show a non-trivial time evolution that can be used to discriminate between models of structure formation. We compare these analytic results with non-Gaussian N -body simulations, which turn out to be in very good agreement up to scales where σ ≲ 1. 相似文献
275.
José?ángel?Sánchez Navarro Pablo?Coloma LópezEmail author Antonio?Perez-Garcia 《Hydrogeology Journal》2004,12(5):601-609
The geothermal flow which emerges by convection at the springs in Aragón is evaluated, and compared with the theoretical heat flow which permeates the surface of the region by conduction. The geological materials through which the convection takes place are defined (geothermal formations), and the areas where thermal convection appears most intensely are related.
Resumen En el presente trabajo se evalúa el flujo geotérmico que emerge por convección en los principales manantiales de aguas termales de Aragón (España), comparándolo con el flujo geotérmico que penetra en la corteza terrestre por conducción. Se definen las formaciones geotérmicas y se estudian las áreas en las que se concentra de forma preferente ese flujo termal por convección.
Résumé Le flux géothermique qui émerge par convection à la source Aragon est évalué, et comparé avec le flux de chaleur théorique par conduction. Le matériel géologique dans lequel la convection prend place est défnit (formations géothermiques) et les zones qui manifestent les plus importantes convections thermiques sont relatés.相似文献
276.
277.
Temporal variability and population structure of planktonic ostracods were investigated for the first time in the South Adriatic Sea during 1996. The maximal total ostracod abundance (1167 ind·100 m−3; 69% juveniles, 18% females and 13% males) was recorded in February. Thirteen species of marine planktonic ostracods were identified. Porroecia spinirostris and Archiconchoecia striata dominated the ostracod assemblage, accounting respectively for 62% and 18% of the total abundance. Their annual peaks were recorded during the cold season, which was the period of their intense reproduction, with favourable temperature conditions and lack of predators. The females surpassed the males in abundance in most species. The presence of the mesopelagic species indicated a strong influence of intermediate layer water masses from the Eastern Mediterranean Sea. 相似文献
278.
The taxonomic sufficiency approach has been proposed as a surrogate for the typical analysis of speciesabundance data, especially
in conditions involving prominent pollution gradients. Here, we evaluate the use of taxonomic sufficiency with infralittoral
macrobenthic data derived from samples taken in a moderate polluted subtropical environment in southeastern Brazil, analysing
five taxonomic levels and including two functional levels throughout polychaete feeding guilds and trophic groups. The data
were collected seasonally at nine stations and studied for two abundance data series (0.5 and 1.0 mm sieve mesh-size). The
results showed a similar ordination pattern between the two sieve mesh-size, but with the 0.5 mm sieve data a different pattern
was observed during austral summer. A slight loss of information was detected using genus, family, polychaete species and
their feeding guilds as taxonomic/ functional units. These results together with those of the cost/ benefit ratio, suggested
that the family level seemed to be sufficient to detect the impact caused by moderate pollution in this shallow-water, subtropical
environment. In additional, through the use of feeding guilds, similar patterns are obtained. Correlation analysis showed
that chlorophyll a, total organic matter, zinc, and chromium sediment content were the variables that best explained the biological
pattern observed and not always the best correlation coefficient occurring at the species level. The feeding guild approach
seems to be useful and generates interpretable results similar to those obtained with the species level of the whole macroinfauna.
The results showed an important cost reduction in the sample processing, suggesting that it is possible to adopt a coarser
taxonomic level monitoring program even in species-rich communities. 相似文献
279.
280.
Pablo?L.?AnticoEmail authorView authors OrcID profile Vicente?R.?Barros 《Theoretical and Applied Climatology》2017,129(1-2):171-176
Long-term variability of El Niño (EN) cycle has been the topic of several studies, mainly because of its impacts on climate around the globe. This variability has been mainly described by changes in the intensity and frequency of EN events. In this study, interdecadal changes in the zonal evolution of EN-related sea surface temperature anomalies (SSTA) and their possible link with a well-known mode of Pacific interdecadal variability are analyzed. EN events are classified according to the sense of zonal propagation of SSTA along the equatorial Pacific during the period 1900–2012. As a result, two types of EN are defined: eastward-directed and westward-directed EN. It is found that EN-related SSTA preferably evolves to the east (west) during the warm (cold) phase of the Pacific Decadal Oscillation. Hence, this study offers new insights into the possible causes of long-term EN changes. 相似文献