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141.
142.
By means of an integrated multifunctional experimental pilot plant there were tested several process variants for the treatment of carbonic-acid-aggressive and manganese-enriched model water. Deacidification and oxidation of iron- and manganese-constituents are effected by gas exchange with atmospheric oxygen. The hydrated-oxide particles formed are held back by two layers of foamed polyurethane and a sand bed lying uppermost. The process of neutralization and oxidation as well as flocculation is accelerated by the use of chalk, lime or soda. The effectiveness of the process technology investigated is illustrated by a table of results of small-scale experiments with model waters prepared from drinking water. 相似文献
143.
Summary This article presents the results of an experimental study of creep behaviour of a rock salt under uniaxial compression as a function of prestrain, simulating sampling disturbance. The prestrain was produced by radial compressive loading of the specimens prior to creep testing. The tests were conducted on an artifical salt to avoid excessive scattering of the results.The results obtained from several series of single-stage creep tests show that, at short-term, the creep response of salt is strongly affected by the preloading history of samples. The nature of this effect depends upon the intensity of radial compressive preloading, and its magnitude is a function of the creep stress level. The effect, however, decreases with increasing plastic deformation, indicating that large creep strains may eventually lead to a complete loss of preloading memory. 相似文献
144.
The natural nuclear reactors were geological arrangements of uranium and water where, like the 2 Ga-old uranium deposits discovered in Oklo (Gabon, Africa), uranium chain fission processes took place. Ten years after its discovery the phenomenon of Oklo is still neglected in Precambrian evolutionary studies. We consider some probable reasons for this and show that natural reactors might have been important, specific, localized sources of ionizing radiation during both the criticality and shut-down periods. Some of the long-lived fission products which migrated from the reactor core could also have been effective radiation energy sources after fixation in the environment or upon uptake by the earliest forms of living matter. The results presented here concern the examination of conditions for nuclear criticality on the Precambrian Earth, the dose-rates of ionizing radiation available and the estimate of the number of natural nuclear reactors that could have been active in the past. 相似文献
145.
146.
This study is concerned with the influence of the glacial-isostatic adjustment caused by the last Pleistocene deglaciation
on the present-day sea level. The viscoelastic deformation caused by the time-variable ice and ocean loads is simulated by
computing the resulting perturbations for a spherical, self-gravitating, incompressible, Maxwell-viscoelastic earth model.
The associated variation of the earth rotation is described in terms of the Liouville equation, which is solved by means of
the MacCullagh formulae. This allows the determination of the vertical displacement and geoid height and, thus, the solution
of the sea-level equation. We test several viscosity and ice models and evaluate them by comparison of the computed response
with the Holocene relative sea-level record. Using the optimum combination of viscosity and ice models, we then estimate the
influence of the last Pleistocene deglaciation on the tide-gauge measurements. A comparison between the observational and
residual linear trends for the tide-gauge measurements shows a significant reduction of the variance and geographical variability
for the latter, in particular for the formerly ice-covered regions of North America and Scandinavia. The favoured value determined
for the global mean sea-level rise is (1.46±0.2) mm a−1. 相似文献
147.
代内公平、国际贸易与可持续发展 总被引:5,自引:0,他引:5
现阶段,不同国家或区域之间商品交流的种类与数量日益增大。由于发达国家与发展中国家在国际贸易中所扮演的角色不同,因此,在等经济价值交换规律的作用下,发展中国家的环境状况逐渐恶化。文章通过构建开放经济的物质流模型,探讨了物质交换行为对系统内部的自然环境的影响,并对1987年日本的物质流动状况进行了案例研究。分析表明,发达国家的经济发展水平在很大程度上依赖于其它国家内部自然资源与环境的支撑作用。 相似文献
148.
149.
150.
Z. Mrz 《国际地质力学数值与分析法杂志》1980,4(1):45-55
A comparative discussion of constitutive rate equations generated by using the hypoelasticity and plasticity theories is presented. If is shown that these two approaches are equivalent for the loading process but differ essentially in defining the unloading (or reverse loading) paths. The multisurface plasticity formulation proves to be more convenient in incorporating memory rules of particular loading events, whereas loading-unloading criteria used in hypoelasticity may result in an unrealistic prediction of material response for some loading paths, and in particular, for cyclic loading. The violation of the continuity condition between loading–unloading domains in proposed constitutive relations3,4 limits their applicability to some particular classes of loading paths. 相似文献