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291.
Conventional development theory and practice have often failed to recognise the centrality of women in sustainable resource management. A conceptual shift in environment and resource policies, planning and programmes is required to affirm that women are active participants rather than passive recipients of change. To address the need for enhanced women's participation in community-based forestry development, this paper focuses on the policy and programme elements important in the design and implementation of successful community forestry projects. Consequently, the intention of this paper is to increase the awareness of planners and decision-makers regarding methods of operationalising women's participation in community-based forestry. Building upon previous work from aid agencies and other researchers, a range of institutional, organisational, socio-cultural and project elements are identified. These elements provide a comprehensive framework of the policy and programme issues requiring consideration when promoting women's participation in successful community-based forestry activities. 相似文献
292.
293.
Derek V. Ellis 《Marine pollution bulletin》1988,19(12):656-661
294.
Gilbert Fraud Philippe Lo Bello Chris M. Hall Jean-Marie Cantagrel Derek York Michel Bernat 《Journal of Volcanology and Geothermal Research》1990,40(1)
K-feldspars separated from Plio-Quaternary pumice flows of the Monts-Dore massif (Massif Central, France) give 40Ar/39Ar saddle-shaped age spectra. Laser-probe analysis of hand-picked single grains gives ages in agreement with those of overlying and underlying lava flows previously dated by the conventional K-Ar method. The laser-probe ages are lower than the minimum ages measured on the populations of grains by the step-heating method. As previously suggested by Lo Bello and co-workers for the pumice flow of Neschers belonging to the same volcanic massif, the saddle-shaped age spectra are ascribed to the different Ar-release patterns of two populations of K-feldspars: (1) young sanidine phenocrysts of the pumices; and (2) old K-feldspars plucked from the Hercynian basement during the explosive eruption. Measurements of both the granitic rocks from surrounding areas and the granitic xenoliths included in pumices give ages around 330 Ma and show that most of the xenocrysts included in the pumices did not lose significant amounts of argon during the eruption. With the 40Ar/39Ar step-heating method, we were able to detect contamination of Quaternary K-feldspars by Hercynian K-feldspars as low as 0.25. Because pumice flows of the Monts-Dore massif crop out over large areas, these new ages will be useful for establishing a precise stratigraphy of the European Plio-Quaternary. 相似文献
295.
Derek B. Booth 《Quaternary Research》1986,25(3)
An estimate of the sliding velocity and basal meltwater discharge of the Puget lobe of the Cordilleran ice sheet can be calculated from its reconstructed extent, altitude, and mass balance. Lobe dimensions and surface altitudes are inferred from ice limits and flow-direction indicators. Net annual mass balance and total ablation are calculated from relations empirically derived from modern maritime glaciers. An equilibrium-line altitude between 1200 and 1250 m is calculated for the maximum glacial advance (ca. 15,000 yr B.P.) during the Vashon Stade of the Fraser Glaciation. This estimate is in accord with geologic data and is insensitive to plausible variability in the parameters used in the reconstruction. Resultant sliding velocities are as much as 650 m/a at the equilibrium line, decreasing both up- and downglacier. Such velocities for an ice sheet of this size are consistent with nonsurging behavior. Average meltwater discharge increases monotonically downglacier to 3000 m3/sec at the terminus and is of a comparable magnitude to ice discharge over much of the glacier's ablation area. Palcoclimatic inferences derived from this reconstruction are consistent with previous, independently derived studies of late Pleistocene temperature and precipitation in the Pacific Northwest. 相似文献
296.
Fifty-eight chondrules were separated from the Dhajala H3.8 chondrite and their thermoluminescence properties were measured. Chips from 30 of the chondrules were examined petrographically and with electron-microprobe techniques; the bulk compositions of 30 chondrules were determined by the fused bead technique. Porphyritic chondrules, especially 5 which have particularly high contents of mesostasis, tend to have higher TL (mass-normalized) than non-porphyritic chondrules. Significant correlations between log(TL) and the bulk CaO, Al2O3 and MnO content of the chondrules, and between log(TL) and the CaO, Al2O3, SiO2 and normative anorthite content of the chondrule glass, indicate an association between TL and the abundance and composition of mesostasis. Unequilibrated chondrules ( i.e. those whose olivine is compositionally heterogeneous and high in Ca) have low TL, whereas equilibrated chondrules have a wide range of TL, depending on their chemical and petrographic properties.We suggest that the TL level in a given chondrule is governed by its bulk composition (which largely determined the abundance and composition of constituent glass) and by metamorphism (which devitrfied the glass in those chondrules with high Ca glass to produce the TL phosphor). We also suggest that one reason why certain chondrules in type 3 ordinary chondrites are unequilibrated, while others are equilibrated, is that the mesostasis of the unequilibrated chondrules resisted the devitrification. This devitrification is necessary for the diffusive communication between chondrule grains and matrix that enables equilibration. 相似文献
297.
298.
Stochastic and deterministic upscaling techniques are developed that upscale saturated conductivity at the support of 0.04 m2 to representative actual infiltration (Ib) for support units (blocks) of 101–104 m2, as a function of steady state rainfall and runon to the block, under Hortonian runoff (infiltration excess overland flow). Parameters in the upscaling techniques represent the surface runoff flow pattern and the spatial probability distribution of saturated conductivity within the 101–104 m2 block. The stochastic upscaling technique represents the spatial process of infiltration and runoff using a simple process-imitating model, estimating Ib using Monte Carlo simulation. The deterministic upscaling technique aggregates these processes by a deterministic function relating rainfall and runon to Ib. The stochastic upscaling technique is shown to be capable to upscale saturated conductivity derived from ring infiltrometers to Ib values of plots (1 m2) corresponding to measured Ib values using rainfall simulators. It is shown that both upscaling techniques can be used to estimate Ib for each time step and each block in transient rainfall–runoff models, giving better estimates of cumulative runoff from a hillslope and a small catchment than model runs that do not use upscaling techniques. 相似文献
299.
Derek Ford 《Environmental Geology》2007,51(5):675-684
Jovan Cviji? was born in western Serbia and studied widely in the Dinaric Kras. His publication of Das Karstphänomen (1893) established that rock dissolution was the key process and that it created most types of dolines, “the diagnostic karst landforms”. The Dinaric Kras thus became the type area for dissolutional landforms and aquifers; Germanicised as “karst”, the regional name is now applied to modern and paleo-dissolutional phenomena worldwide. Cviji? related the complex behaviour of karstic aquifers to development of solutional conduit networks and linked it to a cycle of landform evolution. He is recognized as “the father of karst geomorphology”. 相似文献
300.