全文获取类型
收费全文 | 150篇 |
免费 | 3篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 2篇 |
地球物理 | 22篇 |
地质学 | 66篇 |
海洋学 | 3篇 |
天文学 | 56篇 |
自然地理 | 2篇 |
出版年
2024年 | 1篇 |
2021年 | 1篇 |
2020年 | 3篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2017年 | 9篇 |
2016年 | 13篇 |
2015年 | 3篇 |
2014年 | 2篇 |
2013年 | 14篇 |
2012年 | 10篇 |
2011年 | 13篇 |
2010年 | 1篇 |
2009年 | 3篇 |
2008年 | 4篇 |
2007年 | 2篇 |
2006年 | 2篇 |
2005年 | 4篇 |
2004年 | 1篇 |
2003年 | 1篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 1篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1979年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有153条查询结果,搜索用时 15 毫秒
151.
Hydrochemical and isotopic study of groundwater in Wadi El Hechim–Garaa Hamra basin, Central Tunisia
Hydrochemical and isotopic study of Miocene and Mio-Plio-Quaternary (M-P-Q) aquifers in Wadi El Hechim?CGaraa Hamra basin, Central Tunisia was undertaken in order to investigate recharge mode and processes leading to mineralization of groundwater as well as interaction between both systems. The results revealed striking differences between the two aquifer systems. While the Miocene aquifer contains recently recharged waters with generally low mineralization (around 0.5?g?L?1), stemming mainly from dissolution of carbonate minerals, the M-P-Q aquifer reveals TDS values reaching 3?g?L?1, controlled mainly by dissolution of evaporitic minerals. Isotopic data indicate that the Miocene aquifer contains water recharged in past several decades (bomb tritium and bomb radiocarbon detected). The M-P-Q system appears to be much slower, with time scales of groundwater flow possibly reaching some thousands of years. Sharp discontinuity of hydrochemical and isotope characteristic of groundwater observed across the major tectonic fault separating the Miocene and M-P-Q aquifers supports the idea of very limited (if any) hydraulic interconnection between both studied systems. This in turn calls for revision of existing conceptual models of groundwater flow in the region postulating significant groundwater fluxes crossing the fault in the direction of M-P-Q aquifer and adjacent aquifers in the Wadi al Fakka plain. 相似文献
152.
Weak dust ion-acoustic (DIA) double- layers (DLs) in a dusty plasma with nonextensive electrons are addressed. A generalized Korteweg-de Vries equation with a cubic nonlinearity is derived. It is shown that under certain conditions, the effect of electron nonextensivity can be quite important. In particular, it may be noted that due to the net negative dust charge and electron nonextensivity, the present dusty plasma model may admit compressive as well as rarefactive weak DIA-DLS. Considering the wide relevance of nonlinear oscillations in space dusty plasmas, our investigation may be taken as a prerequisite for the understanding of the nonlinear structures observed in the ionosphere and the auroral acceleration regions. 相似文献
153.
Nadjinangar Gotoum Christophe Nkem Kamel Hammami M. Ahamat?Charfadine L. C. Owono?Owono Nejm-Eddine Jaidane 《Astrophysics and Space Science》2011,332(1):209-217
We report on the calculation of collision induced rotational excitation cross sections and rate coefficients of AlF by He
atom at low temperature. These quantities were obtained by first computing the interaction potential energy surface (PES)
of the AlF(X
1Σ+)-He(1
S) van der Waals complex at the ab initio Coupled Cluster with Single and Double and perturbative Triple excitations [CCSD(T)] level of theory. The aug-cc-pVQZ Gaussian
basis, to which was added a set of bond functions, was used for that purpose. The calculations account for basis set superposition
errors (BSSE). The interaction potential presents a minimum of ∼24 cm−1 below the AlF-He dissociation limit. The PES was fitted on a basis of Legendre polynomial functions to allow for the calculation
of cross sections in the close-coupling (CC) approach. By averaging these cross sections over a Maxwell-Boltzmann velocity
distribution, rate coefficients were inferred at low temperatures (T≤300 K). From our computations, a propensity towards ΔJ=1 transitions is observed. 相似文献