全文获取类型
收费全文 | 205篇 |
免费 | 7篇 |
专业分类
测绘学 | 11篇 |
大气科学 | 16篇 |
地球物理 | 43篇 |
地质学 | 83篇 |
海洋学 | 18篇 |
天文学 | 12篇 |
自然地理 | 29篇 |
出版年
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 4篇 |
2018年 | 9篇 |
2017年 | 5篇 |
2016年 | 9篇 |
2015年 | 9篇 |
2014年 | 12篇 |
2013年 | 9篇 |
2012年 | 4篇 |
2011年 | 15篇 |
2010年 | 11篇 |
2009年 | 15篇 |
2008年 | 14篇 |
2007年 | 18篇 |
2006年 | 15篇 |
2005年 | 10篇 |
2004年 | 6篇 |
2003年 | 4篇 |
2002年 | 7篇 |
2001年 | 5篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有212条查询结果,搜索用时 15 毫秒
61.
Bernard Aumont Sasha Madronich Isabelle Bey Geoffrey S. Tyndall 《Journal of Atmospheric Chemistry》2000,35(1):59-75
Measurements show that 20–60% of the carbon mass present in fine atmospheric particulate matter consists of water soluble organic compounds (WSOC). However, only 5–20% of this WSOC has been identified, mainly as dicarboxylic acids. Because of their high solubility in water, multifunctional secondary compounds derived from the gas-phase oxidation of volatile organic compounds (VOC) are suspected to be key contributors to the WSOC. To test this assumption, an estimate of aqueous uptake of secondary VOC was included in a highly detailed gas-phase mechanism which treats explicitly the formation of the secondary VOC from a set of representative primary species. Simulations were conducted for 2 scenarios, representing typical rural and urban areas. It was observed that the uptake of secondary VOC can lead to WSOC mass concentrations in the range of a few C m–3, in fairly good agreement with typical WSOC mass concentrations measured. Speciation of WSOC was found to be mainly as tri- or higher multifunctional hydroxy-carbonyl species and hydroxy-hydroperoxide-carbonyl species, in urban and rural environments, respectively. However, it was also found that taking into account only the absorption of secondary VOC does not bring the carboxylic acids mass concentration in agreement with measurements. An attempt was made to explain this discrepancy by introducing chemistry occurring within deliquescent aerosols. 相似文献
62.
63.
64.
65.
Dust formation processes are investigated in the hot hydrogen-deficient wind of carbon-rich Wolf-Rayet (WC) stars. Results
show that dust precursors (small linear carbon chains) form in large quantities only at high gas densities. This suggests
that a clumpy wind or an equatorial disc are necessary to trigger dust formation in WC stars.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
66.
Rey Vincent Dufresne Christiane Fuda Jean-Luc Mallarino Didier Missamou Tathy Paugam Caroline Rougier Gilles Taupier-Letage Isabelle 《Ocean Dynamics》2020,70(7):913-933
Ocean Dynamics - A dense network of instruments has been deployed within harbors along the Mediterranean coast, in the Toulon Metropole area, between the Hyères islands and the Sanary Bay in... 相似文献
67.
In the eastern boreal forest of Quebec, Canada, harvesting strategies try to mimic the effects of fire on forest ecosystems,
assuming that both disturbances have similar impacts. However impacts of both types of perturbations on lacustrine ecosystems,
especially on chironomids (non-biting midges), are still poorly understood. The objectives of this study were to determine
if logging and fire resulted in chironomid assemblages significantly different than pre-disturbance states and to see if the
harvesting strategy (careful logging around advanced growth (CLAAG) and buffer zones) protect lakes from logging effects in
the boreal forest. Three statistical tests were used to study the difference between pre- and post-disturbance assemblages:
a principal component analysis (PCA), analysis of similarity (ANOSIM) and a non-metric multi-dimensional scaling (MDS) ordination.
All statistical analyses suggested that fire did not have any effects on chironomid assemblages. The PCA analysis showed that
two logging events in Lac aux Huards created chironomid assemblages slightly outside the pre-disturbance variability. However,
ANOSIM showed that these differences were not significant at the 0.5% level of significance. These results suggest that the
presence of a buffer zone probably limited the impacts of logging on lakes in this area. 相似文献
68.
Benoît Flahaut Marie‐Alexandre Laurent Isabelle Thomas 《The Professional geographer》2002,54(1):67-82
This article demonstrates the operation of a simple optimal location‐allocation technique for solving the problem of locating one or several community recycling center(s) within a residential area. The article attempts to measure both transportation and externality costs in comparable units, and to incorporate them into the model. A sensitivity analysis of the results at the level of the nuisance provides further insight into the operation of the model and the relative importance of the quantification of pollution in applied location‐allocation problems. 相似文献
69.
Émilie Gaudry Philippe Sainctavit Farid Juillot Federica Bondioli Philippe Ohresser Isabelle Letard 《Physics and Chemistry of Minerals》2006,32(10):710-720
The best known cause for colors in insulating minerals is due to transition metal ions as impurities. As an example, Cr3+ is responsible for the red color of ruby (α-Al2O3:Cr3+) and the green color of eskolaite (α-Cr2O3). Using X-ray absorption measurements, we connect the colors of the Cr
x
Al2−x
O3 series with the structural and electronic local environment around Cr. UV–VIS electronic parameters, such as the crystal field and the Racah parameter B, are related to those deduced from the analysis of the isotropic and XMCD spectra at the Cr L2,3-edges in Cr0.07Al1.93O3 and eskolaite. The Cr–O bond lengths are extracted by EXAFS at the Cr K-edge in the whole Cr
x
Al2−x
O3 (0.07≤x< 2) solid solution series. The variation of the mean Cr–O distance between Cr0.07Al1.93O3 and α-Cr2O3 is evaluated to be 0.015 Å (≈1%). The variation of the crystal field in the Cr
x
Al2−x
O3 series is discussed in relation with the variation of the averaged Cr–O distances. 相似文献
70.
Evaporation of intercepted rain by a canopy is an important component of evapotranspiration, particularly in the humid boreal forest, which is subject to frequent precipitation and where conifers have a large surface water storage capacity. Unfortunately, our knowledge of interception processes for this type of environment is limited by the many challenges associated with experimental monitoring of the canopy water balance. The objective of this study is to observe and estimate canopy storage capacity and wet canopy evaporation at the sub-daily and seasonal time scales in a humid boreal forest. This study relies on field-based estimates of rainfall interception and evapotranspiration partitioning at the Montmorency Forest, Québec, Canada (mean annual precipitation: 1600 mm, mean annual evapotranspiration: 550 mm), in two balsam fir-white birch forest stands. Evapotranspiration was monitored using eddy covariance sensors and sap flow systems, whereas rainfall interception was measured using 12 sets of throughfall and six stemflow collectors randomly placed inside six 400-m2 plots. Changes in the amount of water stored on the canopy were also directly monitored using the stem compression method. The amount of water intercepted by the forest canopy was 11 ± 5% of the total rainfall during the snow-free (5 July–18 October) measurement periods of 2017 and 2018. The maximum canopy storage estimated from rainfall interception measurements was on average 1.6 ± 0.7 mm, though a higher value was found using the stem compression method (2.2 ± 1.6 mm). Taking the average of the two forest stands studied, evaporation of intercepted water represented 21 ± 8% of evapotranspiration, while the contribution of transpiration and understory evapotranspiration was 36 ± 9% and 18 ± 8%. The observations of each of the evapotranspiration terms underestimated the total evapotranspiration observed, so that 26 ± 12% of it was not attributed. These results highlight the importance to account for the evaporation of rain intercepted by humid boreal forests in hydrological models. 相似文献