全文获取类型
收费全文 | 427篇 |
免费 | 28篇 |
国内免费 | 7篇 |
专业分类
测绘学 | 5篇 |
大气科学 | 29篇 |
地球物理 | 76篇 |
地质学 | 203篇 |
海洋学 | 20篇 |
天文学 | 59篇 |
综合类 | 3篇 |
自然地理 | 67篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 11篇 |
2021年 | 15篇 |
2020年 | 19篇 |
2019年 | 16篇 |
2018年 | 12篇 |
2017年 | 16篇 |
2016年 | 22篇 |
2015年 | 18篇 |
2014年 | 16篇 |
2013年 | 34篇 |
2012年 | 25篇 |
2011年 | 38篇 |
2010年 | 23篇 |
2009年 | 18篇 |
2008年 | 28篇 |
2007年 | 11篇 |
2006年 | 21篇 |
2005年 | 16篇 |
2004年 | 17篇 |
2003年 | 8篇 |
2002年 | 11篇 |
2001年 | 9篇 |
2000年 | 6篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1983年 | 2篇 |
1980年 | 1篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1973年 | 4篇 |
1969年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有462条查询结果,搜索用时 15 毫秒
211.
Sébastien Picaud Emmanuel Chereul Annie C. Robin Francisco Garzón 《Astrophysics and Space Science》2003,284(2):523-526
We present the results of two studies of the inner Galaxy : on the one hand, a maximum likelihood fitting method using the Besançon model of Galaxy to constrain the density laws of the outer bulge and the holed disc; on the other hand, the comparison of Besançon simulations with infrared data on fields near longitude 20–27 degrees to verify the existence of a long and thin in-plane bar. These two parallel studies seem to show the co-existence of a structure (the bar) in addition with a very oblate outer bulge. 相似文献
212.
Jehin Emmanuel Boehnhardt Hermann Sekanina Zdenek Bonfils Xavier Schütz Oliver Beuzit Jean-Luc Billeres Malvina Garradd Gordon J. Leisy Pierre Marchis Franck Más Antonio Origlia Livia Scarpa Daniel Thomas Daniel Tozzi Gian Paolo 《Earth, Moon, and Planets》2002,90(1-4):147-151
Comet C/2001 A2 experienced several splitting events duringits 2001 perihelion passage. The first break-upevent was observed
in March 2001 (IAUC 7616).In this paper we report the first results of ourextensive imaging and spectroscopic monitoring campaignwith
ESO telescopes over several weeks before andafter the perihelion passage on May 25 2001. 相似文献
213.
Zhang Shuai Carranza Emmanuel John M. Xiao Keyan Wei Hantao Yang Fan Chen Zhenghui Li Nan Xiang Jie 《Natural Resources Research》2022,31(4):1981-1999
Natural Resources Research - Known mineralized locations and randomly chosen non-mineralized locations are used traditionally as training samples in data-driven mineral prospectivity mapping (MPM).... 相似文献
214.
215.
216.
Bastian Joachim Anke Wohlers Nicholas Norberg Emmanuel Gardés Elena Petrishcheva Rainer Abart 《Physics and Chemistry of Minerals》2013,40(1):19-27
Cylinders of synthetic periclase single crystals were annealed at 0.15–0.5 GPa and 900–1200 °C under water-saturated conditions for 45 min to 72 h. Infrared spectra measured on the quenched products show bands at 3,297 and 3,312 cm?1 indicating V OH ? centers (OH-defect stretching vibrations in a half-compensated cation vacancy) in the MgO structure as a result of proton diffusion into the crystal. For completely equilibrated specimens, the OH-defect concentration, expressed as H2O equivalent, was calculated to 3.5 wt ppm H2O at 1,200 °C and 0.5 GPa based on the calibration method of Libowitzky and Rossmann (Am Min 82:1111–1115, 1997). This value was confirmed via Raman spectroscopy, which shows OH-defect-related bands at identical wavenumbers and yields an H2O equivalent concentration of about 9 wt ppm using the quantification scheme of Thomas et al. (Am Min 93:1550–1557, 2008), revised by Mrosko et al. (Am Mineral 96:1748–1759, 2011). Results of both independent methods give an overall OH-defect concentration range of 3.5–9 (+4.5/?2.6) ppm H2O. Proton diffusion follows an Arrhenius law with an activation energy E a = 280 ± 64 kJ mol?1 and the logarithm of the pre-exponential factor logDo (m2 s?1) = ?2.4 ± 1.9. IR spectra taken close to the rims of MgO crystals that were exposed to water-saturated conditions at 1,200 °C and 0.5 GPa for 24 h show an additional band at 3,697 cm?1, which is related to brucite precipitates. This may be explained by diffusion of molecular water into the periclase, and its reaction with the host crystal during quenching. Diffusion of molecular water may be described by logDH2O (m2 s?1) = ?14.1 ± 0.4 (2σ) at 1,200 °C and 0.5 GPa, which is ~ 2 orders of magnitude slower than proton diffusion at identical P-T conditions. 相似文献
217.
Thomas Hainschwang Stefanos Karampelas Emmanuel Fritsch Franck Notari 《Mineralogy and Petrology》2013,107(3):393-413
The methods of luminescence spectroscopy and microscopy are widely used for the analysis of gem materials. This paper gives an overview of the most important applications of the analysis of laser and UV excited luminescence by spectroscopy and visually by microscopy with emphasis on diamond, and specifically natural type Ib diamond, little studied so far. Luminescence based techniques are paramount to the gemmological analysis of diamond, in order to determine whether it is natural, treated or synthetic. The great sensitivity of luminescence helps detect some emitting centres that are undetectable by any other analytical method. Hence, especially for diamond, luminescence is an enabling technology, as illustrated by its pioneering use of imagery for the separation of natural and synthetic diamond, and of spectroscopy for the detection of High Pressure–High Temperature treatment. For all other gemstones the applications are at the moment less numerous, but nevertheless they remain highly important. They provide quickly information on the identification of a gem material, and its treatment. Besides the study of broad band emissions caused by various colour centres, the typical PL-causing trace elements (amongst others) are chromium, manganese, uranium and rare earth elements. In pearls the study of broad band luminescence can be useful, and particularly the study of pink to red porphyrin luminescence in pearls from certain species such as Pinctada and Pteria and others can help identify the pearl-producing mollusc, or if a pearl has been dyed or not. Type Ib diamonds are representative of the importance and complexity of the analysis of luminescence by microscopy and spectroscopy. They show a wide range of sometimes very complex emissions that result in luminescence colours from green to yellow to orange or red. These emissions show generally very inhomogeneous distribution. They are caused by a range of defects, however only a few of them are well characterized. 相似文献
218.
Alexander Vandenbohede Ilka Wallis Emmanuel Van Houtte Eric Van Ranst 《Hydrogeology Journal》2013,21(6):1307-1321
Managed artificial recharge (MAR) is a well-established practice for augmentation of depleted groundwater resources or for environmental benefit. At the St-André MAR site in the Belgian dune area, groundwater resources are optimised through re-use of highly treated wastewater by means of infiltration ponds. The very high quality of the infiltration water sets this system apart from other MAR systems. The low total dissolved solid (TDS) content in the infiltration water (less than 50 mg/L) compared to the dune aquifer (500 mg/L) triggers a number of reactions, increasing the TDS through soil-aquifer passage. Multi-component reactive transport modelling was applied to analyse the geochemical processes that occur. Carbonate dissolution is the main process increasing the TDS of the infiltration water. Oxic aquifer conditions prevail between the infiltration ponds and the extraction wells. This is driven by the high flow velocities, leaving no time to consume O2 between the ponds and extraction wells. Cation exchange is important when infiltration water is replaced by native dune water or when significant changes in infiltration-water quality occur. The seasonal variation of O2 and temperature in the infiltration water are the main drivers for seasonal changes in the concentration of all major ions. 相似文献
219.
Evaluation of unconfined aquifer parameters from flow to partially penetrating wells in Tailan River basin, China 总被引:1,自引:1,他引:0
Emmanuel Kwame Appiah-Adjei Longcang Shu Kwaku Amaning Adjei Minjing Deng Xiaohui Wang 《Environmental Earth Sciences》2013,69(3):799-809
Effective evaluation, management and abstraction of groundwater resources of any aquifer require accurate and reliable estimates of its hydraulic parameters. This study, therefore, looks at the determination of hydraulic parameters of an unconfined aquifer using both analytical and numerical approaches. A long-duration pumping test data obtained from an unconfined aquifer system within the Tailan River basin in Xinjiang Autonomous Region in the northwest of China is used, in this study, to investigate the best method for estimating the parameters of the aquifer. The pumping test was conducted by pumping from a radial collector well and measuring the response in nine observation wells; all the wells used in the test were partially penetrating. Using two well-known tools, namely AquiferTest and MODFLOW, as an aid for the analytical and numerical approaches, respectively, the parameters of the aquifer were determined and their outputs compared. The estimated horizontal hydraulic conductivity, vertical hydraulic conductivity, and specific yield for the analytical approach are 38.1–50.30 m/day, 3.02–9.05 m/day and 0.204–0.339, respectively, while the corresponding numerical estimates are 20.50–35.24 m/day, 0.10–3.40 m/day, and 0.27–0.31, respectively. Comparing the two, the numerical estimates were found to be more representative of the aquifer in the study area since it simulated the groundwater flow conditions of the pumping test in the aquifer system better than the analytical solution. 相似文献
220.
The Nine-Year WMAP results combined with other cosmological data seem to indicate an enhanced favor for the phantom regime, comparing to previous analyses. This behavior, unless reversed by future observational data, suggests to consider the phantom regime more thoroughly. In this work we provide three modified gravitational scenarios in which we obtain the phantom realization without the appearance of ghosts degrees of freedom, which plague the naive approaches on the subject, namely the Brans-Dicke type gravity, the scalar-Einstein-Gauss-Bonnet gravity, and the F(R) gravity, which are moreover free of perturbative instabilities. The phantom regime seems to favor the gravitational modification instead of the universe-content alteration. 相似文献