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排序方式: 共有162条查询结果,搜索用时 15 毫秒
51.
Ernesto A. Lacomba 《Celestial Mechanics and Dynamical Astronomy》1980,21(1):45-53
In this work we will describe the sets in the rigid body phase space where the energy and angular momentum are constant, and it will turn out that in nontrivial cases they will simply take the form of cartesian products of the polhodes byS
1. These sets are important for the global study of said geodesic mechanical system for being invariant under Euler's equations (energy and momentum are constant along their solutions).To motivate from something more familiar in celestial mechanics, we will begin to relate the problem to Smale's study of the planarn-body problem (Smale, 1970) and Easton's study of the planar 3-body problem (Easton, 1971), exemplifying in particular with the central force problem.In the last Sections 4 and 5, we extent our methods to give results for generalized solids on Lie groups, mentioning the further extensions to transitive mechanical systems.Proceedings of the Sixth Conference on Mathematical Methods in Celestial Mechanics held at Oberwolfach (West Germany) from 14 to 19 August, 1978.This work was partially supported by the Consejo Nacional de Ciencia y Tecnología (México) under grant PNCB-049. 相似文献
52.
Simulated Urban Climate Response to Historical Land Use Modification in the Basin of Mexico 总被引:4,自引:0,他引:4
Numerical simulations of thermal field variation due to land use changes, such as the reduction of the lacustrine system and the growth of the urban area, in the Basin of Mexico are presented. It is shown that the historically recorded warming in the basin could be attributed, not only to the growth of the urban area, but more importantly to the drastic reduction in the lacustrine system that existed in the basin. 相似文献
53.
54.
Climatic conditions that affect the interannual variability of Caribbean hurricanes are studied. Composite meteorological and oceanographic reanalysis fields are constructed for active and inactive seasons since 1979, and differences are calculated for spring and summer periods to provide guidance in statistical analysis. Predictors are extracted for areas exhibiting high contrast between active and inactive seasons, and intercomparisons are made. Zonal winds north of Venezuela exhibit westerly anomalies prior to active years, so coastal upwelling and the north Brazil current are diminished. Rainfall increases in the Orinoco River basin, creating a fresh warm plume north of Trinidad. The predictor time series are regressed onto an index of Caribbean hurricanes, and multivariate algorithms are formulated. It is found that atmospheric kinematic and convective predictors explain only ??20% of hurricane variance at 3?C5-month lead time. Subsurface ocean predictors offer higher levels of explained hurricane variance (42%) at 3?C5-month lead time, using 1?C200-m-depth-averaged temperatures in the east Pacific and southern Caribbean. We place the statistical results in a conceptual framework to better understand climatic processes anticipating Caribbean hurricanes. 相似文献
55.
Antonio Geraldo Ferreira Emilio Soria-Olivas Antonio Jos�� Serrano L��pez Ernesto Lopez-Baeza 《Theoretical and Applied Climatology》2011,106(1-2):263-279
This study describes the results of artificial neural network (ANN) models to estimate net radiation (R n), at surface. Three ANN models were developed based on meteorological data such as wind velocity and direction, surface and air temperature, relative humidity, and soil moisture and temperature. A comparison has been made between the R n estimates provided by the neural models and two linear models (LM) that need solar incoming shortwave radiation measurements as input parameter. Both ANN and LM results were tested against in situ measured R n. For the LM ones, the estimations showed a root mean square error (RMSE) between 34.10 and 39.48?W?m?2 and correlation coefficient (R 2) between 0.96 and 0.97 considering both the developing and the testing phases of calculations. The estimates obtained by the ANN models showed RMSEs between 6.54 and 48.75?W?m?2 and R 2 between 0.92 and 0.98 considering both the training and the testing phases. The ANN estimates are shown to be similar or even better, in some cases, than those given by the LMs. According to the authors?? knowledge, the use of ANNs to estimate R n has not been discussed earlier, and based on the results obtained, it represents a formidable potential tool for R n prediction using commonly measured meteorological parameters. 相似文献
56.
Senal MI Jacinto GS San Diego-McGlone ML Siringan F Zamora P Soria L Cardenas MB Villanoy C Cabrera O 《Marine pollution bulletin》2011,63(5-12):195-200
Submarine groundwater discharge (SGD) on the reef flat of Bolinao, Pangasinan (Philippines) was mapped using electrical resistivity, 222Rn, and nutrient concentration measurements. Nitrate levels as high as 126 μM, or 1-2 orders of magnitude higher than ambient concentrations, were measured in some areas of the reef flat. Nutrient fluxes were higher during the wet season (May-October) than the dry season (November-April). Dissolved inorganic nitrogen (DIN=NO3+NO2+NH4) and soluble reactive phosphorus (SRP) fluxes during the wet season were 4.4 and 0.2 mmoles m(-2) d(-1), respectively. With the increase population size and anthropogenic activities in Bolinao, an enhancement of SGD-derived nitrogen levels is likely. This could lead to eutrophic conditions in the otherwise oligotrophic waters surrounding the Santiago reef flat. 相似文献
57.
58.
Equilibrium Points and Central Configurations for the Lennard-Jones 2- and 3-Body Problems 总被引:1,自引:1,他引:0
Montserrat Corbera Jaume Llibre Ernesto Pérez-Chavela 《Celestial Mechanics and Dynamical Astronomy》2004,89(3):235-266
In this paper we study the relative equilibria and their stability for a system of three point particles moving under the
action of a Lennard-Jones potential. A central configuration is a special position of the particles where the position and
acceleration vectors of each particle are proportional, and the constant of proportionality is the same for all particles.
Since the Lennard-Jones potential depends only on the mutual distances among the particles, it is invariant under rotations.
In a rotating frame the orbits coming from central configurations become equilibrium points, the relative equilibria. Due
to the form of the potential, the relative equilibria depend on the size of the system, that is, depend strongly of the momentum
of inertia I. In this work we characterize the relative equilibria, we find the bifurcation values of I for which the number of relative equilibria is changing, we also analyze the stability of the relative equilibria.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
59.
Malcolm L. Spaulding Saul B. Saila Ernesto Lorda Henry Walker Eric Anderson J.Craig Swanson 《Estuarine, Coastal and Shelf Science》1983,16(5):511-541
An oil-spill fishery impact assessment model composed of an oil-spill fates model, a shelf hydrodynamics model, an ichthyoplankton transport and fate model, and a fishery population model originally developed by Reed & Spaulding, has been improved and applied to the Georges Bank-Gulf of Maine region to assess the probable impact of oil spills on several key fisheries. The model addresses direct impacts of oil on the commercial fishery through hydrocarbon-induced egg and larval mortality. This early life stage hydrocarbon-induced mortality is estimated by assuming a toxicity threshold approach and by mapping the spatial/temporal interaction between the subsurface oil concentrations caused by the spill and the developing eggs and larvae. Model output is given in terms of differential catch, with a comparison made of hydrocarbon-impacted fisheries.Simulations of tanker and blowout spills at two separate locations for each season of the year in the Outer Continental Shelf lease areas have been completed for Atlantic herring, haddock, and Atlantic cod. Results to date suggest a complex interaction among spill location and timing, the spatial and temporal spawning distribution of the species, and the hydrodynamics of the area. The largest impacts occur for spring and winter spills. 相似文献
60.
Jesús Arturo Robles-Gutiérrez Ernesto Lacomba Zamora Jesús Martiniano Arturo Robles-Domínguez Cinna Lomnitz María Eugenia Robles-Gutiérrez 《Geofísica Internacional》2013,52(2):153-157
Experimental data in fluids suggest that nonadditive electromagnetic forces between 3 or more molecules account for the existence of critical points, triple states and phase transitions (Robles-Domínguez et al., 2007; Robles-Gutiérrez et al., 2010). Similar nonadditive forces between 3 or more molecules in the gravitational field incorporated into Newton’s universal gravitational law may also explain the existence of dark matter. 相似文献