全文获取类型
收费全文 | 1219篇 |
免费 | 39篇 |
国内免费 | 7篇 |
专业分类
测绘学 | 33篇 |
大气科学 | 81篇 |
地球物理 | 297篇 |
地质学 | 389篇 |
海洋学 | 113篇 |
天文学 | 178篇 |
综合类 | 4篇 |
自然地理 | 170篇 |
出版年
2020年 | 13篇 |
2019年 | 16篇 |
2018年 | 31篇 |
2017年 | 23篇 |
2016年 | 20篇 |
2015年 | 24篇 |
2014年 | 26篇 |
2013年 | 57篇 |
2012年 | 45篇 |
2011年 | 51篇 |
2010年 | 38篇 |
2009年 | 45篇 |
2008年 | 53篇 |
2007年 | 40篇 |
2006年 | 47篇 |
2005年 | 41篇 |
2004年 | 30篇 |
2003年 | 31篇 |
2002年 | 40篇 |
2001年 | 28篇 |
2000年 | 24篇 |
1999年 | 16篇 |
1998年 | 25篇 |
1997年 | 18篇 |
1996年 | 13篇 |
1995年 | 18篇 |
1994年 | 17篇 |
1993年 | 24篇 |
1992年 | 18篇 |
1991年 | 11篇 |
1990年 | 19篇 |
1989年 | 15篇 |
1988年 | 13篇 |
1987年 | 18篇 |
1986年 | 20篇 |
1985年 | 28篇 |
1984年 | 22篇 |
1983年 | 28篇 |
1982年 | 21篇 |
1981年 | 15篇 |
1980年 | 23篇 |
1979年 | 20篇 |
1978年 | 22篇 |
1977年 | 16篇 |
1976年 | 20篇 |
1975年 | 9篇 |
1974年 | 14篇 |
1973年 | 15篇 |
1972年 | 7篇 |
1971年 | 6篇 |
排序方式: 共有1265条查询结果,搜索用时 31 毫秒
91.
Controls on Spatial Variability of Uranium in Sandstone Aquifers 总被引:1,自引:0,他引:1
92.
Giovanni Muttoni Dennis V. Kent James E.T. Channell 《Earth and Planetary Science Letters》1996,140(1-4):97-112
A new early Late Triassic paleopole for Adria has been obtained from the Val Sabbia Sandstone in the Southern Alps. As Early Permian and Jurassic-Cretaceous paleomagnetic data from para-autochthonous regions of Adria such as the Southern Alps are consistent with ‘African’ APWPs[1–2], paleomagnetic data from this region can be used to bolster the West Gondwana APWP in the poorly known Late Permian-Triassic time interval. The Southern Alpine paleopoles are integrated with the West Gondwana and Laurussia APWPs of Van der Voo [1] and used to generate a tectonic model for the evolution of Pangea. The Early Permian overall mean paleopole for West Gondwana and Adria, in conjunction with the coeval Laurussia paleopole, support Pangea B of Morel and Irving [3]. The Late Permian/Early Triassic and the Middle/Late Triassic paleopoles from Adria and Laurussia support Pangea A-2 of Van der Voo and French [4]. The phase of transcurrent motion between Laurasia and Gondwana[5] that caused the Pangea B to A-2 transition occurred essentially in the Permian (at the end of Variscan orogeny) with an average relative velocity of approximately 10 cm/yr. Finally, the Late Triassic/Early Jurassic paleopoles from West Gondwana and Laurussia agree with Pangea A-1 of Bullard et al. [6], the widely accepted Pangea configuration at the time of the Jurassic breakup. 相似文献
93.
94.
95.
96.
Lamprophyric dikes, mainly of camptonite/monchiquite affinities occur in the Wiedemanns Fjord area. One example contains a complex assemblage of olivine-orthopyroxene-chrome spinel nodules, megacrysts of kaersutite, diopside, strongly reverse-zoned green salite and various spinel phases. Microprobe analyses are presented for all these phases and for the lilac-coloured titansalites and strongly-coloured kaersutites of the groundmass. It is concluded that these minerals record evolution under various P, T and oxidation regimes during the formation of a lamprophyric parent magma. The nodules provide evidence for deep fractures in this area supposedly associated with early rifting in the North Atlantic. 相似文献
97.
Concentrations of the (n, γ)-produced radionuclide60Co were measured in lunar samples at various depths from the surface down to 360 g/cm2. By comparing the data obtained to calculated production rates (based on the work of Lingenfelter et al. [8]) we determined the present day lunar neutron production rate, which was found to be (12 ± 3)neutrons/cm2sec (E < 10MeV). 相似文献
98.
When reference frames and diffusing components are properly selected, the flux equations for diffusion of the major components in natural garnets may often be approximated by: J DC. In such cases it is shown that, for reasonable diffusion coefficients and boundary conditions, observed zoning profiles in natural garnets may be explained with pure diffusion models. These models allow for original inhomogeneities in the host rock and may be used to explain why single hand specimens may show such a variety of zoning profiles within a single mineral species. 相似文献
99.
The sorption of silver by poorly crystallized manganese oxides was studied using synthesized samples of three members of the manganous manganite (birnessite) group, of different chemical composition and crystallinity, and a poorly organized γ-MnO2. All four oxides sorbed significant quantities of silver. The manganous manganites showed the greatest sorption (up to 0.5 moles silver/mole MnOx at pH 7) while the γ-MnO2 showed the least (0.3 moles silver/ mole MnOx at pH 7). Sorption of silver was adequately described by the Langmuir equation over a considerable concentration range. The relationship failed at low pH values and high equilibrium silver concentrations. The sorption capacity showed a direct relationship with pH. However, the rate of increase of sorption capacity decreased at the higher pH values.Silver sorption maxima. were not directly related to surface area but appeared to vary with the amount of occluded sodium and potassium present in the manganese oxide. The important processes involved in the uptake of silver by the four poorly crystallized manganese oxides ara considered to be surface exchange for manganese, potassium and sodium as well as exchange for structural manganese, potassium and sodium. 相似文献
100.
The significance of the inorganic removal of dissolved silica from estuarine zones was investigated at three river mouths: the Orinoco, the Savannah and the Mississippi. Particular attention was given to the Mississippi river plume, where extensive inorganic silica uptake had been reported. Mixing curves and laboratory dilution experiments provided little evidence that the phenomenon was widespread. Because of an uncertain fresh water tie point, some inorganic uptake could not be completely ruled out for the Orinoco, but, in the plumes of the Savannah and Mississippi rivers, no inorganic silica removal was indicated. In contrast to published experiments on river sediments, laboratory dilution studies on suspended matter from the Mississippi river showed release of dissolved silica instead of uptake. 相似文献