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91.
为厘清贵州上二叠统龙潭组煤系地层的物源,以黔西南地区黔普地1井为研究对象,采集了上二叠统龙潭组的岩心进行稀土元素分析。结果表明,龙潭组的稀土总量较高(177.03×10-6~592.58×10-6),轻、重稀土分馏明显,稀土元素配分模式呈轻稀土富集、重稀土相对亏损的右倾型;(La/Sm)_N为2.63~4.72,(Gd/Yb)_N值为1.47~2.218,表明轻稀土分馏较重稀土严重;δEu无异常。研究表明,其形成的构造环境与大陆边缘与大陆弧相近,推测黔普地1井二叠系龙潭组物质来源以玄武岩为主。 相似文献
92.
Flavia Burger Alvaro Ayala David Farias Thomas E. Shaw Shelley MacDonell Ben Brock James McPhee Francesca Pellicciotti 《水文研究》2019,33(2):214-229
We present a field‐data rich modelling analysis to reconstruct the climatic forcing, glacier response, and runoff generation from a high‐elevation catchment in central Chile over the period 2000–2015 to provide insights into the differing contributions of debris‐covered and debris‐free glaciers under current and future changing climatic conditions. Model simulations with the physically based glacio‐hydrological model TOPKAPI‐ETH reveal a period of neutral or slightly positive mass balance between 2000 and 2010, followed by a transition to increasingly large annual mass losses, associated with a recent mega drought. Mass losses commence earlier, and are more severe, for a heavily debris‐covered glacier, most likely due to its strong dependence on snow avalanche accumulation, which has declined in recent years. Catchment runoff shows a marked decreasing trend over the study period, but with high interannual variability directly linked to winter snow accumulation, and high contribution from ice melt in dry periods and drought conditions. The study demonstrates the importance of incorporating local‐scale processes such as snow avalanche accumulation and spatially variable debris thickness, in understanding the responses of different glacier types to climate change. We highlight the increased dependency of runoff from high Andean catchments on the diminishing resource of glacier ice during dry years. 相似文献
93.
Correctly estimating the effect of elevated CO2 (eCO2) on biomass production is paramount for accurately projecting agricultural productivity, global carbon balances and climate changes. Plant physiology suggests that eCO2 should result in a strongly positive CO2 fertilisation effect (CFE) via positive effects on photosynthesis and water use efficiency. However, the CFE in CO2 experiments is often constrained because of other factors of which rainfall pattern is particularly important. Here, we apply a generally applicable, empirically derived relationship between the CFE and an index of seasonal rainfall balance (SRB), to identify how historical and projected future rainfall patterns modify the CFE using 25 native grassland sites in south-eastern (SE) Australia as a test case. We found that historical and projected rainfall produced SRBs that varied widely from year-to-year resulting in a CFE that was only positive in about 40% of years, with no or even negative biomass responses in the remainder of years; a finding that is in marked contrast to other studies that have not taken account of relationships between rainfall seasonality and plant responses to CO2. The dependence of the CFE on SRB also means that using the CFE from a specific eCO2 experiment can be misleading as the result will be heavily influenced by the SRB during the period of experimentation but this problem can be avoided by using a robust general relationship of the kind used in this study. Generalisations of grassland biomass responses to the rising CO2 concentration are contextual in terms of the variability in precipitation seasonality; as such, this provides a new lens by which to view aboveground responses to the rising CO2 concentration and fosters a novel approach for cross-site comparisons among experiments. 相似文献
94.
Nigel W. Arnell Jason A. Lowe Ben Lloyd-Hughes Timothy J. Osborn 《Climatic change》2018,147(1-2):61-76
The 2015 Paris Agreement commits countries to pursue efforts to limit the increase in global mean temperature to 1.5 °C above pre-industrial levels. We assess the consequences of achieving this target in 2100 for the impacts that are avoided, using several indicators of impact (exposure to drought, river flooding, heat waves and demands for heating and cooling energy). The proportion of impacts that are avoided is not simply equal to the proportional reduction in temperature. At the global scale, the median proportion of projected impacts avoided by the 1.5 °C target relative to a rise of 4 °C ranges between 62 and 95% across sectors: the greatest reduction is for heat wave impacts. The 1.5 °C target results in impacts that would be between 27 and 62% lower than with the 2 °C target. For each indicator, there are differences in the proportions of impacts avoided between regions depending on exposure and the regional changes in climate (particularly precipitation). Uncertainty in the proportion of impacts that are avoided for a specific sector depends on the range in the shape of the relationship between global temperature change and impact, and this varies between sectors. 相似文献
95.
Emission reductions improve the chances that dangerous anthropogenic climate change will be averted, but could also cause some firms financial distress. Corporate failures, especially if they are unnecessary, add to the social cost of abatement. Social value can be permanently destroyed by the dissolution of organizational capital, deadweight losses paid to liquidators, and unemployment. This article proposes using measures of corporate solvency as an objective tool for policy makers to calibrate the optimal stringency of climate change policies, so that they can deliver the least loss of corporate solvency for a given level of emission reductions. They could also be used to determine the generosity of any compensation to address losses to corporate solvency. We demonstrate this approach using a case study of the UK’s Carbon Price Support (a carbon tax).
Key policy insights
Solvency metrics could be used to empirically calibrate the optimal stringency of climate policies.
An idealized solvency trajectory for firms affected by climate change policy would cause corporate solvency to initially decline – approaching but not exceeding ‘distressed’ levels – and then gradually improve to a new ‘steady state’ once the low-carbon transition had been achieved.
In terms of the UK’s Carbon Price Support, corporate solvency of energy-intensive industries was found to be stable subsequent to its introduction. Therefore, the available evidence does not support its later weakening.
96.
中国城市群多中心网络的拓扑结构 总被引:6,自引:1,他引:5
在既有理论基础上扩展了城市群多中心网络的度量工具,考察中国12个城市群总部—分支机构的企业关联网络,比较梳理了地级城市空间联系的拓扑结构。实证研究发现:①包括长三角、珠三角和京津冀三大典型城市群在内,中国城市群内部网络系统的拓扑结构依然发育不完善,在联系数据方面均呈现出一定的稀疏矩阵特征,空间组合关系均为树状结构。②总部区位(出度)的层级性差异均高于分支机构区位(入度)的层级性差异,显示出城市群内部空间“流”的不对称性。③针对12个城市群内部网络的拓扑结构聚类分析表明:长三角、珠三角、京津冀、山东半岛、海峡西岸地区的城市群内部网络联系较为紧密,呈现出一定程度的一体化网络特征;其中三大典型城市群存在明显的企业总部集聚核心,其余城市群内部的网络联系松散,跨城企业联系比重较低,在拓扑结构上大多呈现出以省会或副省级城市为指向的向心式联系。 相似文献
97.
98.
Mark A. Rathmell Margaret M. Streepey Eric J. Essene Ben A. van der Pluijm 《Contributions to Mineralogy and Petrology》1999,134(2-3):217-231
The Elzevir Terrane of the Grenville Orogen in southern Ontario contains metapelites and abundant graphitic marbles that
were regionally metamorphosed from the upper greenschist to upper amphibolite facies. Comparative thermometry was undertaken
with widely used calibrations for the systems garnet-biotite, calcite-dolomite, and calcite-graphite. Temperatures that are
obtained from matrix biotites paired with prograde garnet near-rim analyses are usually consistent with those determined using
calcite-graphite thermometry. However, calcite-graphite thermometry occasionally yields low temperatures due to lack of equilibration
of anomalously light graphite. Application of calcite-graphite and garnet-biotite systems may yield temperatures up to 70 °C
higher than calcite-dolomite in amphibolite facies rocks. Calcite-dolomite temperatures most closely approach those from calcite-graphite
and garnet-biotite when the samples contain a single generation of dolomite and calcite grains contain no visible dolomite
exsolution lamellae. However, some of these samples yield temperatures considerably lower than temperatures calculated from
calcite-graphite and garnet-biotite thermometry, indicating that the calcite-dolomite thermometer may have been partially
reset during retrogression. Estimated peak metamorphic temperatures of regional metamorphism between Madoc (upper greenschist
facies) and Bancroft (upper amphibolite facies) range from 500 to 650 °C. These results place the chlorite-staurolite isograd
at 540 °C, the kyanite-sillimanite isograd at 590 °C, and the sillimanite-K-feldspar isograd at 650 °C. Although each thermometer
may have an absolute uncertainty of as much as ±50 °C, the 50 to 60 °C temperature differences between the isograds are probably
accurate to 10 to 20 °C. An incomplete picture of the thermal gradients can result from the application of only one thermometer
in a given area. Simultaneous application of several systems allows one to recognize and overcome the inherent limitations
of each thermometer.
Received: 26 March 1997 / Accepted: 15 April 1998 相似文献
99.
100.
Oussama Abidi Mohamed Hédi Inoubli Kawthar Sebei Adnen Amiri Haifa Boussiga Imen Hamdi Nasr Abdelhamid Ben Salem Mahmoud Elabed 《Surveys in Geophysics》2017,38(3):617-649
The Maastrichtian–Paleocene El Haria formation was studied and defined in Tunisia on the basis of outcrops and borehole data; few studies were interested in its three-dimensional extent. In this paper, the El Haria formation is reviewed in the context of a tectono-stratigraphic interval using an integrated seismic stratigraphic analysis based on borehole lithology logs, electrical well logging, well shots, vertical seismic profiles and post-stack surface data. Seismic analysis benefits from appropriate calibration with borehole data, conventional interpretation, velocity mapping, seismic attributes and post-stack model-based inversion. The applied methodology proved to be powerful for charactering the marly Maastrichtian–Paleocene interval of the El Haria formation. Migrated seismic sections together with borehole measurements are used to detail the three-dimensional changes in thickness, facies and depositional environment in the Cap Bon and Gulf of Hammamet regions during the Maastrichtian–Paleocene time. Furthermore, dating based on their microfossil content divulges local and multiple internal hiatuses within the El Haria formation which are related to the geodynamic evolution of the depositional floor since the Campanian stage. Interpreted seismic sections display concordance, unconformities, pinchouts, sedimentary gaps, incised valleys and syn-sedimentary normal faulting. Based on the seismic reflection geometry and terminations, seven sequences are delineated. These sequences are related to base-level changes as the combination of depositional floor paleo-topography, tectonic forces, subsidence and the developed accommodation space. These factors controlled the occurrence of the various parts of the Maastrichtian–Paleocene interval. Detailed examinations of these deposits together with the analysis of the structural deformation at different time periods allowed us to obtain a better understanding of the sediment architecture in depth and the delineation of the geodynamic evolution of the region. 相似文献