首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   132篇
  免费   3篇
  国内免费   1篇
测绘学   4篇
大气科学   8篇
地球物理   30篇
地质学   44篇
海洋学   12篇
天文学   34篇
自然地理   4篇
  2023年   1篇
  2021年   2篇
  2020年   3篇
  2019年   4篇
  2018年   8篇
  2017年   4篇
  2016年   7篇
  2015年   7篇
  2014年   9篇
  2013年   5篇
  2012年   4篇
  2011年   8篇
  2010年   7篇
  2009年   8篇
  2008年   4篇
  2007年   9篇
  2006年   3篇
  2005年   3篇
  2004年   3篇
  2003年   3篇
  2002年   3篇
  2001年   3篇
  2000年   1篇
  1999年   1篇
  1998年   3篇
  1997年   1篇
  1996年   1篇
  1995年   1篇
  1992年   1篇
  1991年   4篇
  1989年   1篇
  1988年   1篇
  1984年   1篇
  1983年   2篇
  1982年   2篇
  1981年   1篇
  1980年   2篇
  1977年   1篇
  1976年   1篇
  1973年   1篇
  1970年   1篇
  1969年   1篇
排序方式: 共有136条查询结果,搜索用时 15 毫秒
81.
In the present study we compare performances of the prediction of hourly tidal level variations at Puerto Belgrano, a coastal site in the Bahia Blanca Estuary (Argentina), by means of the MOHID model, which is a numerical model designed for coastal and estuarine shallow water applications, and of an artificial neural network (ANN). It was shown that the ANN model is able to predict the hourly tidal levels over long term duration with at least seven days of observations and with a better performance in respect to the numerical model. Our findings can be useful to implement ANN-based tools for future studies of the hydrodynamics of Bahía Blanca estuary.  相似文献   
82.
Gravity field and interior of Rhea from Cassini data analysis   总被引:1,自引:0,他引:1  
The Cassini spacecraft encountered Rhea on November 26, 2005. Analysis of the Doppler data acquired at and around closest approach yields the mass of Rhea and the quadrupole moments of its gravity field with unprecedented accuracy. We obtained which corresponds to a density of . Our results for J2 and C22 are (7.947±0.892)×10−4 and (2.3526±0.0476)×10−4, respectively. These values are consistent with hydrostatic equilibrium. From the value of C22, we infer the non-dimensional moment of inertia C/MR2=0.3721±0.0036. Our models of Rhea's interior based on the gravity data favor an almost undifferentiated satellite. A discontinuity between a core and a mantle is possible but not required by the data. Models with a constant silicate mass fraction throughout the body cannot account for the determined quadrupole coefficients. The data exclude fully differentiated models in which the core would be composed of unhydrated silicates and the mantle would be composed of pure ice. If the mantle contains 10% in mass of silicates, the core extends to 630 km in radius and has a silicate mass fraction of 40%. A continuous model in which the silicates are more concentrated toward the center of the body than in the outer layers is allowed by the gravity data but excluded by thermal evolution considerations. The one model that fits the gravity data and is self-consistent when energy transport and ice melting are qualitatively considered is an “almost undifferentiated” Rhea, in which a very large uniform core is surrounded by a relatively thin ice shell containing no rock at all.  相似文献   
83.
We investigated the dynamics of the continuous seismic signal recorded before and during the 2011–2012 El Hierro eruption (Canary Islands) using the innovative approach of the Fisher–Shannon method, a suitable statistical tool for detecting dynamic changes in complex systems. Our findings identify dynamic changes in the seismic signal that can be correlated with different stress states of the magmatic setting and the plumbing system in the volcano at El Hierro. The results contribute to the understanding of the fracturing pattern in the crust during a new intrusion and eruption of an overpressurized batch of magma.  相似文献   
84.
The incidental capture in fisheries is probably the main conservation problem affecting seabirds. While the capture of albatrosses and petrels on longline hooks is well-known worldwide, the bycatch of diving seabirds in gillnets is an overlooked conservation problem. During a winter coastal fishing trip, the capture of Magellanic penguins (Spheniscus magellanicus) was recorded in driftnet and bottom setnet fisheries for the first time in southern Brazil. The highest captures rates were found in driftnets, from 146.5 to 545.5 penguins/km2 of net and a total of 56 dead penguins were recorded. In the bottom gillnet, a total of 12 birds were killed and the capture rates varied from 41.7 to 125.0 penguins/km2 of net. Although preliminary, the results presented in this paper were consistent between sets. If we consider the magnitude of driftnet and setnet fishing fleets, and that most dead penguins were adults, the impact upon Magellanic penguin populations is probably significant.  相似文献   
85.
Artificial macrophytes were experimentally deployed in Boadella Reservoir (NE Spain) and assessed for fish use throughout the first 3 months of the 2007 summer drawdown. In total, 1,832 individuals of seven fish species were recorded through visual censuses, with introduced perch Perca fluviatilis being the prevalent species. Fish richness and abundance were significantly higher in artificial macrophytes than in rocky shores and sandy beaches, displaying a unimodal variation through time. P. fluviatilis, Rutilus rutilus and Abramis brama were significantly more abundant in artificial macrophytes than in the other two naturally submersed habitats, where no individuals of these species were recorded. The abundances of Squalius laietanus, Lepomis gibbosus, Micropterus salmoides and Cyprinus carpio were overall greater in artificial macrophytes than in rocky shores but displayed significant habitat × time interactions. A decrease in predation risk was apparently the key-factor of the intensive use of artificial macrophytes by small fish (≤100 mm TL) in Boadella Reservoir, since most species reduced drastically or completely the use of submerged structures when body size increased. This study demonstrates that adding artificial structures mimicking aquatic macrophytes can be an interesting tool to mitigate the adverse effects of water level fluctuations on fish assemblages in structure-less and homogeneous ecosystems, and to understand the mechanisms affecting habitat use and species replacement.  相似文献   
86.
87.
The development and widespread use of statistical learning models have brought the need for tools that help analysts diagnose, build, and refine those models. In this work, in particular, we focus on interpolation models, which spatially predict the value of a variable based on the values of its neighborhood. Investigating these results spatially or comparing them with other models at different levels of granularity is still a challenge for the analysts trying to understand and refine their models. To deal with that, we propose a visual analytics model-agnostic tool for facilitating the comparison and refinement of spatial models at different levels of granularity using interactive visualization techniques. The tool was built in collaboration with specialists who used it to diagnose and improve a spatial model for predicting residential real estate prices.  相似文献   
88.
A mathematical model of the biological process occurring in a modified biofilm airlift suspension reactor is presented. When compared with a traditional wastewater treatment plant, a biofilm airlift suspension process has major advantages, such as higher oxygen levels in the bulk fluid and lower space requirements. The limited volumes obtained with this technique generally do not allow to reach the high times of contact required for an efficient removal of nitrogen that normally are characterized by a slower kinetics than carbonaceous compounds. To avoid this problem, supports for attached biomass growth were inserted in the reactor. Both physical and biological aspects were incorporated into the presented model to simulate the removal processes of the substrates. A sensitivity analysis was performed, and the model was validated using experimental results obtained at a lab-scale plant. This model can accurately estimate the removal rate in different boundary conditions providing the details of the water quality profiles through the reactor and in the attached biomass. The model thus represents a valid aid for design purposes and for the management of treatment plants that use these uncommon reactors. The model also provides the required hydraulic retention time for a complete nitrification and the appropriate recirculation ratio. The results have shown the full-scale applicability of this treatment due to its efficiencies coupled to the advantages of its low impact, low space requirement and low sludge production.  相似文献   
89.
List of papers from other journals  相似文献   
90.
List of papers from other journals  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号