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排序方式: 共有606条查询结果,搜索用时 15 毫秒
571.
A groundwater tracing investigation as an aid of locating groundwater monitoring stations on the Mitchell Plain of southern Indiana 总被引:1,自引:0,他引:1
Wanfang Zhou Barry F. Beck Arthur J. Pettit Brad J. Stephenson 《Environmental Geology》2002,41(7):842-851
572.
Barry J. Katz Christopher G.A. Harrison Eugene H. Man 《Earth and Planetary Science Letters》1979,44(2):279-286
The “second region” of the kinetic curve for the racemization (epimerization) of isoleucine in foraminifera is defined from previously published data corrected for the thermal history experienced by the samples. These kinetic parameters are applied to racemization data from Deep Sea Drilling Project Sites 332A and 333 from the Deep Drill Valley, Mid-Atlantic Ridge, and Site 148 from the Aves Ridge, in order to determine whether there are any observable effects due to the geothermal gradient. The data for Site 148 clearly show an increase of temperature with depth. The data for the two sites of the Mid-Atlantic Ridge do not show this clear relationship. When bottom water temperature variations are taken into consideration, the effects of the geothermal gradient become apparent. Since the degree of racemization is dependent upon both age and temperature, a knowledge of the age of a sample places constraints upon its thermal history, and hence on the heat flow at the location since deposition of the sample. The crude heat flow models thus developed are compatible with present geologic and geophysical information. It appears probable that detailed heat flow models may be developed by improving analytical precision. 相似文献
573.
Barry Kean Atkinson 《Physics and Chemistry of Minerals》1978,2(4):305-315
Stress relaxation experiments were performed on hot-pressed cylinders of synthetic, polycrystalline galena at temperatures of 500°, 600°, 700° and 800°C at atmospheric pressure after various levels of axial strain, in the range from 2% to 25%, had been imposed at a constant strain rate (?) of 3×10?4 s?1. For this study a new apparatus was built which can measure small changes in applied stress (σ), better than ±0.5 × 105 Pa, and which incorporates a facility whereby the composition of the test specimen can be fixed through equilibration with a gas atmosphere of controlled composition. Deformation mechanism maps constructed largely on theoretical grounds predict that, under the conditions studied here, high-temperature dislocation creep, for which ?∝σ5, gives way on lowering the applied stress to diffusion creep, for which ?∝σ. The experimental results agree in large measure with these theoretical predictions. However, it is not possible in this preliminary study to conclusively identify the dominant deformation mechanisms. 相似文献
574.
Barry Saltzman 《Pure and Applied Geophysics》1968,69(1):237-259
Summary Equations governing the axially-symmetric time-average state of the atmosphere and the transient departures from this mean state are set down. As a first step toward a solution of this system for seasonal average conditions, a model is formulated based on the thermodynamical energy equation for the vertical average of the mean state, and on the perturbation solutions of the linearized equations governing the baroclinic growth of transient eddies. All forms of non-adiabatic heating within the atmosphere and at the earth's surface are parameterized. The resulting differential equation governing the axially-symmetric mean potential temperature distribution takes the form of a steadystate diffusion equation in surface spherical coordinates, with a variable Austausch coefficient which is to be determined iteratively as a dependent variable.Global solutions, for winter and summer equilibrium conditions, are obtained for the thermal structure, the heat balance components, the transient eddy variances of temperature and meridional wind speed, and the covariance representing the meridional eddy heat transport. These solutions are for different types of surface conditions (ocean, land), and for a successively more complete variety of modes of heat transfer ranging from pure radiation to a combination of radiation, latent heat processes, and conduction and convection within the atmosphere and the subsurface layers. The results for this latter complete case seem to be a reasonable first order approximation to the observed distributions. Suggestions are made for improving and generalizing the study. 相似文献
575.
In July 1971 when approximately 25% of the clams in Long Cove, Searsport, Maine, had been killed by the March 1971 oil spill, collections of surviving clams for histological examination were made. These studies were continued through 1974 and revealed a high incidence of gonadal tumours in clams contaminated by the oil. The area of highest oil impact correlated with the highest per cent of tumours. The tumours were found to be malignant neoplasms. 相似文献
576.
Peter M. D. Bradshaw Ian Thomson Barry W. Smee Jan O. Larsson 《Journal of Geochemical Exploration》1974,3(3):209-225
This paper deals briefly with the principles of geochemical migration in the secondary (soil, sediment) environment, a knowledge of which is essential to a correct interpretation of exploration geochemical data. Examples are given which illustrate that the principles which apply in the more easily interpreted tropical areas, also apply in the more complicated glaciated regions. Any person employing exploration geochemistry in geomorphologically complicated areas, is well advised to study data from strictly residual soil areas where the fundamentals of geochemical migration are more easily observed. From this base it is easier to understand the additional complications of geochemistry in mountainous and glaciated terrain. Of the variety of exploration geochemical techniques which can be used, this paper deals specifically with two: soil profile sampling, and different strengths of acid extraction of metal from samples. Examples from the different environments are compared and contrasted. 相似文献
577.
578.
Presence of springs in karst terranes provides a unique opportunity to study the rather complex, multi-porosity, and multi-permeability
system. When springs are used to evaluate the integrity of storage facilities for hazardous materials or waste disposal facilities
constructed in karst areas, the spatial heterogeneity of karst aquifers makes intra-spring comparisons preferred statistical
tests. One of the commonly used statistical tests is water quality control procedure such as Shewhart-CUSUM control charts.
Appropriate application of the water quality control procedure to intra-spring monitoring depends on whether the assumptions
can be justified about the aquifer that drains to the spring and the dataset collected at the spring. Violation of the assumptions
would render the statistical tests invalid, which may result in a failure of the groundwater monitoring program. In intra-spring
monitoring, it is the temporal variations of water quality at a karst spring need to be addressed, whereas the water quality
at the spring is closely associated with the characteristics of the aquifer. The example datasets presented in the paper indicate
that both false negative and false positive detections can occur if the temporal variation is not well characterized. 相似文献
579.
580.
Milovan Fustic Stephen M. Hubbard Ron Spencer Derald G. Smith Dale A. Leckie Barry Bennett Steve Larter 《Marine and Petroleum Geology》2012,29(1):219-232
The vast Athabasca Oil Sands of Alberta, Canada has an estimated resource of more than 1.7 trillion barrels of bitumen in-place, the majority of which is hosted in the Lower Cretaceous McMurray Formation. Despite its economical significance the depositional environment of the formation, and particularly the middle part that is the primary reservoir in most areas, is still a matter of considerable debate. These strata of interest are widely known to comprise fluvial and estuarine point bar deposits that were subject to varying degrees of marine influence. The orientation of point bar strata from the formation is tabulated and the majority is observed to dip paleo-basinward, to the north. This observation has proven difficult to explain by geologists attempting to build predictive models for the formation over the last two decades. However, the basinward-dipping point bar strata can be attributed to widespread down-valley translation of point bars in confined north-south oriented valleys, which have previously been delineated in the region. Differentiating the deposits of lateral point bar migration and down-valley translation in the rock record is not possible at the facies scale, and thus translated point bars have not been previously recognized or interpreted in the rock record, despite their prevalence in numerous modern fluvial valley systems. Their identification in the McMurray Formation has important implications for the delineation and development of Canada’s economically significant oil sands resources. 相似文献