全文获取类型
收费全文 | 784篇 |
免费 | 24篇 |
国内免费 | 7篇 |
专业分类
测绘学 | 11篇 |
大气科学 | 108篇 |
地球物理 | 189篇 |
地质学 | 261篇 |
海洋学 | 54篇 |
天文学 | 133篇 |
综合类 | 4篇 |
自然地理 | 55篇 |
出版年
2022年 | 11篇 |
2021年 | 16篇 |
2020年 | 14篇 |
2019年 | 13篇 |
2018年 | 15篇 |
2017年 | 20篇 |
2016年 | 33篇 |
2015年 | 24篇 |
2014年 | 13篇 |
2013年 | 43篇 |
2012年 | 33篇 |
2011年 | 28篇 |
2010年 | 32篇 |
2009年 | 42篇 |
2008年 | 39篇 |
2007年 | 30篇 |
2006年 | 29篇 |
2005年 | 32篇 |
2004年 | 16篇 |
2003年 | 21篇 |
2002年 | 18篇 |
2001年 | 10篇 |
2000年 | 9篇 |
1999年 | 12篇 |
1998年 | 12篇 |
1997年 | 20篇 |
1996年 | 13篇 |
1995年 | 15篇 |
1994年 | 11篇 |
1993年 | 10篇 |
1991年 | 10篇 |
1990年 | 13篇 |
1989年 | 7篇 |
1988年 | 9篇 |
1987年 | 7篇 |
1986年 | 11篇 |
1985年 | 12篇 |
1984年 | 9篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1976年 | 8篇 |
1975年 | 11篇 |
1974年 | 5篇 |
1973年 | 6篇 |
1969年 | 4篇 |
排序方式: 共有815条查询结果,搜索用时 15 毫秒
71.
The solution to the problem of the motion of the Moon relative to spatial irregularities in the interplanetary magnetic field is found. The lunar electrical conductivity is modeled by a two-layer conductivity profile. For the interaction of the Moon with the corotating sector structure of the interplanetary magnetic field it is found that the magnetic field in the lunar shell is the superposition of an oscillatory uniform field, an oscillatory dipole field and anoscillatory field that is toroidal about the axis of the motional electric field. With various lunar conductivity models and the theory of this paper, lunar surface magnetometer data can be quantitatively interpreted to yield information on the conductivity and consequently the temperature of the lunar core.Presently visiting the Max-Planck-Institut für Physik und Astrophysik, München, Germany. 相似文献
72.
Quantifying Organization of Atmospheric Turbulent Eddy Motion Using Nonlinear Time Series Analysis 总被引:3,自引:0,他引:3
Using three methods from nonlinear dynamics, we contrast the level of organization inthe vertical wind velocity (w) time series collected in the atmospheric surface layer(ASL) and the canopy sublayer (CSL) for a wide range of atmospheric stability ()conditions. The nonlinear methods applied include a modified Shannon entropy, waveletthresholding, and mutual information content. Time series measurements collected overa pine forest, a hardwood forest, a grass-covered forest clearing, and a bare soil, desertsurface were used for this purpose. The results from applying all three nonlinear timeseries measures suggest that w in the CSL is more organized than that in the ASL, and that as the flows in both layers evolve from near-neutral to near-convective conditions, the level of organization increases. Furthermore, we found that the degree of organization in w associated with changes in is more significant than the transition from CSL to ASL. 相似文献
73.
74.
Vyacheslav M. Zobin Carlos J. Navarro-Ochoa Gabriel A. Reyes-Dávila 《Bulletin of Volcanology》2006,69(2):141-147
In July–August 2003, the andesitic lava dome at Volcán de Colima, México, was destroyed by a sequence of explosions that replaced the 2×106 m3 dome with a crater 200 m across and 30 m deep. The two strongest explosions occurred on July 17 and August 28. The initial low-frequency impulses that they produced, which were recorded on broadband seismic records, allowed an estimation of the counter forces of the initiating process as being equal to 0.3×1011 N and 1×1011 N for the July and August events, respectively. The seismic characteristics follow the Nishimura-Hamaguchi scaling law for volcanic explosions, reflecting self-similarity in the processes initiating explosive events. The results also show that counter forces can discriminate between the sizes of explosive eruptions that are assigned the same magnitude by conventional methods of classification such as the Volcanic Explosivity Index. The increasing use of broadband seismometers may therefore provide the basis for using counter forces to determine the magnitude of explosive eruptions. 相似文献
75.
Gradient theory (GT), a form of density functional theory (DFT), was applied to water, methanol, and ethanol using the cubic perturbed hard body (CPHB) equation of state (EOS). Compared to the standard form of classical nucleation theory (CNT), the GT results for water showed an improved temperature dependence, but the supersaturation dependence was slightly poorer. GT and several forms of CNT were also found to be in good agreement with a single high T molecular dynamics rate for TIP4P water. The rates predicted by GT for methanol and ethanol were improved by several orders of magnitude compared to CNT, but no improvement in the predicted temperature dependence of the rates was found. 相似文献
76.
Nikolaus Gussone Gerald Langer Markus Geisen Blair A. Steel Ulf Riebesell 《Earth and Planetary Science Letters》2007,260(3-4):505-515
Four species of marine calcifying algae, the coccolithophores Calcidiscus leptoporus, Helicosphaera carteri, Syracosphaera pulchra and Umbilicosphaera foliosa were grown in laboratory cultures under temperatures varying between 14 and 23 °C, and one species, C. leptoporus, under varying [CO32−], ranging from 105 to 219 μmol/kg. Calcium isotope compositions of the coccoliths resemble in both absolute fractionation and temperature sensitivity previous calibrations of marine calcifying species e.g. Emiliania huxleyi (coccolithophores) and Orbulina universa (planktonic foraminifera) as well as inorganically precipitated CaCO3, but also reveal small species specific differences. In contrast to inorganically precipitated calcite, but similar to E. huxleyi and O. universa, the carbonate ion concentration of the medium has no statistically significant influence on the Ca isotope fractionation of C. leptoporus coccoliths; however, combined data of E. huxleyi and C. leptoporus indicate that the observed trends might be related to changes of the calcite saturation state of the medium. Since coccoliths constitute a significant portion of the global oceanic CaCO3 export production, the Ca isotope fractionation in these biogenic structures is important for defining the isotopic composition of the Ca sink of the ocean, one of the key parameters for modelling changes to the marine Ca budget over time. For the present ocean our results are in general agreement with the previously postulated and applied mean value of the oceanic Ca sink (Δsed) of about − 1.3‰, but the observed inter- and intra-species differences point to possible changes in Δsed through earth history, due to changing physico-chemical conditions of the ocean and shifts in floral and faunal assemblages. 相似文献
77.
Since 1988, three separate anti-gay rights referenda have been placed on the ballot in the state of Oregon. While in 1988 Oregon voters passed the first measure (subsequently found unconstitutional), they rejected similar referenda in 1992 and 1994. This paper examines the electoral geography of these three referenda both cartographically and quantitatively. It finds patterns of support for the referenda were closely associated with voting patterns for the Republican Party in gubernatorial and presidential elections, and with sociodemographic indicators reflective of traditionalist areas. 相似文献
78.
A petrologic problem of fundamental importance is to determine whether 2 or more mineral assemblages can be related to one another by continuous or discontinuous facies changes, or whether their bulk compositions occupy non-overlapping regions of composition space. A general method is developed by which 2 regions of n-dimensional space whose vertices are defined by the phases present are tested for compositional overlap. This is accomplished by generating mass balance equations of the type: where Ai is the ith phase in one region and Bj is the th phase in the other. If any such equation satisfies the requirement that the sign of each ai is the same, and that the sign of each bj is the opposite for all i, j such that: k + m = n + 1 then the 2 regions overlap in phase space.By eliminating all overlapping assemblages in a given set, the bivariant fields bounded by univariant equilibria in n-dimensional systems are completely specified. All bulk compositions are considered within the space defined by the phases that participate in the bounding reactions. An extension of the method generates in sequence all bivariant fields and associated reactions about any invariant point. A further extension is applied to multi-system analysis. 相似文献
79.
80.