全文获取类型
收费全文 | 985篇 |
免费 | 26篇 |
国内免费 | 14篇 |
专业分类
测绘学 | 26篇 |
大气科学 | 95篇 |
地球物理 | 196篇 |
地质学 | 449篇 |
海洋学 | 57篇 |
天文学 | 147篇 |
综合类 | 3篇 |
自然地理 | 52篇 |
出版年
2022年 | 5篇 |
2021年 | 6篇 |
2020年 | 8篇 |
2019年 | 8篇 |
2018年 | 13篇 |
2017年 | 17篇 |
2016年 | 23篇 |
2015年 | 15篇 |
2014年 | 34篇 |
2013年 | 45篇 |
2012年 | 45篇 |
2011年 | 37篇 |
2010年 | 39篇 |
2009年 | 50篇 |
2008年 | 30篇 |
2007年 | 43篇 |
2006年 | 36篇 |
2005年 | 33篇 |
2004年 | 36篇 |
2003年 | 33篇 |
2002年 | 40篇 |
2001年 | 30篇 |
2000年 | 18篇 |
1999年 | 24篇 |
1998年 | 19篇 |
1997年 | 17篇 |
1996年 | 29篇 |
1995年 | 16篇 |
1994年 | 15篇 |
1993年 | 11篇 |
1992年 | 14篇 |
1991年 | 13篇 |
1990年 | 14篇 |
1989年 | 21篇 |
1988年 | 11篇 |
1987年 | 12篇 |
1986年 | 8篇 |
1985年 | 6篇 |
1984年 | 13篇 |
1983年 | 9篇 |
1982年 | 8篇 |
1981年 | 12篇 |
1980年 | 11篇 |
1979年 | 11篇 |
1978年 | 12篇 |
1975年 | 10篇 |
1973年 | 6篇 |
1968年 | 4篇 |
1966年 | 5篇 |
1958年 | 5篇 |
排序方式: 共有1025条查询结果,搜索用时 296 毫秒
151.
Measures of Parameter Uncertainty in Geostatistical Estimation and Geostatistical Optimal Design 总被引:4,自引:2,他引:2
Wolfgang Nowak 《Mathematical Geosciences》2010,42(2):199-221
Studies of site exploration, data assimilation, or geostatistical inversion measure parameter uncertainty in order to assess
the optimality of a suggested scheme. This study reviews and discusses measures for parameter uncertainty in spatial estimation.
Most measures originate from alphabetic criteria in optimal design and were transferred to geostatistical estimation. Further
rather intuitive measures can be found in the geostatistical literature, and some new measures will be suggested in this study.
It is shown how these measures relate to the optimality alphabet and to relative entropy. Issues of physical and statistical
significance are addressed whenever they arise. Computational feasibility and efficient ways to evaluate the above measures
are discussed in this paper, and an illustrative synthetic case study is provided. A major conclusion is that the mean estimation
variance and the averaged conditional integral scale are a powerful duo for characterizing conditional parameter uncertainty,
with direct correspondence to the well-understood optimality alphabet. This study is based on cokriging generalized to uncertain
mean and trends because it is the most general representative of linear spatial estimation within the Bayesian framework.
Generalization to kriging and quasi-linear schemes is straightforward. Options for application to non-Gaussian and non-linear
problems are discussed. 相似文献
152.
Turbulent flux observations and modelling over a shallow lake and a wet grassland in the Nam Co basin,Tibetan Plateau 总被引:2,自引:1,他引:1
Tobias?BiermannEmail author Wolfgang?Babel Weiqiang?Ma Xuelong?Chen Elisabeth?Thiem Yaoming?Ma Thomas?Foken 《Theoretical and Applied Climatology》2014,116(1-2):301-316
The Tibetan Plateau plays an important role in the global water cycle and is strongly influenced by climate change. While energy and matter fluxes have been more intensely studied over land surfaces, a large proportion of lakes have either been neglected or parameterised with simple bulk approaches. Therefore, turbulent fluxes were measured over wet grassland and a shallow lake with a single eddy-covariance complex at the shoreline in the Nam Co basin in summer 2009. Footprint analysis was used to split observations according to the underlying surface, and two sophisticated surface models were utilised to derive gap-free time series. Results were then compared with observations and simulations from a nearby eddy-covariance station over dry grassland, yielding pronounced differences. Observations and footprint integrated simulations compared well, even for situations with flux contributions including grassland and lake. The accessibility problem for EC measurements on lakes can be overcome by combining standard meteorological measurements at the shoreline with model simulations, only requiring representative estimates of lake surface temperature. 相似文献
153.
Cindy Mora-Stock Martin Thorwart Tina Wunderlich Stefan Bredemeyer Thor H. Hansteen Wolfgang Rabbel 《International Journal of Earth Sciences》2014,103(7):2015-2028
Llaima and Villarrica are two of the most active volcanoes in the Chilean Southern Volcanic Zone and presently show contrasting types of activity. Llaima is a closed vent edifice with fumarolic activity, while Villarrica has an open vent with a lava lake, continuous degassing and tremor activity. This study is focused on characterizing the relationships between volcanic and seismic activity in the months before and after the 2010 M8.8 Maule earthquake, which was located in NNW direction from the volcanoes. Time series for tremors, long-period and volcano-tectonic events were obtained from the catalogue of the Volcanic Observatory of the Southern Andes (OVDAS) and from the SFB 574 temporary volcanic network. An increase in the amount of tremor activity, long-period events and degassing rates was observed at Villarrica weeks before the mainshock and continued at a high level also after it. This increase in activity is interpreted to be caused by enhanced magma influx at depth and may be unrelated to the Maule event. In Llaima, an increase in the volcano-tectonic activity was observed directly after the earthquake. The simultaneous post-earthquake activity at both volcanoes is consistent with a structural adjustment response. Since this enhanced activity lasted for more than a year, we suggest that it is related to a medium-term change in the static stress. Thus, the Maule earthquake may have affected both volcanoes, but did not trigger eruptions, from which we assume that none of the volcanoes were in a critical state. 相似文献
154.
Philippe Besson Jefferson Degboe Benjamin Berge Valérie Chavagnac Sébastien Fabre Gilles Berger 《Geostandards and Geoanalytical Research》2014,38(3):355-362
We report a measurement procedure to determine simultaneously the major cation concentrations (Na, Ca, K and Mg) of seawater‐derived solutions by inductively coupled plasma‐atomic emission spectrometry. The best results were obtained when the IAPSO (‘standard’) seawater reference material was diluted by thirty times with Milli‐Q® water. We obtained an average reference value rK (the ratio of the mass fraction of potassium to that of chlorine, i.e., (g kg?1)/(g kg?1)) for IAPSO seawater of 0.0205 ± 0.0006 (2.9% RSD), not significantly different from 0.0206 ± 0.0005 (2.4% RSD) for seawater composition reported in the literature. The measured Na, Ca and Mg concentrations correspond to rNa, rCa and rMg values of 0.5406 ± 0.0026 (0.5% RSD), 0.02192 ± 0.00048 (2.2% RSD) and 0.06830 ± 0.00047 (0.7% RSD), respectively, in line with previous values measured by wet‐chemistry and atomic absorption spectrophotometry or wet‐chemical titration. Our measurement procedure was used successfully on synthetic seawater solutions and high‐temperature hydrothermal fluids. 相似文献
155.
We derive the magnetic helicity for configurations formed by flux tubes contained fully or only partially in the spatial domain
considered (called closed and open configurations, respectively). In both cases, magnetic helicity is computed as the sum
of mutual helicity over all possible pairs of magnetic flux tubes weighted by their magnetic fluxes. We emphasize that these
mutual helicities have properties which are not those of mutual inductances in classical circuit theory. For closed configurations, the mutual helicity of two closed flux
tubes is their relative winding around each other (known as the Gauss linkage number). For open configurations, the magnetic
helicity is derived directly from the geometry of the interlaced flux tubes so it can be computed without reference to a ground
state (such as a potential field). We derive the explicit expression in the case of a planar and spherical boundary. The magnetic
helicity has two parts. The first one is given only by the relative positions of the flux tubes on the boundary. It is the
only part if all flux tubes are arch-shaped. The second part counts the integer number of turns each pair of flux tubes wind
about each other. This provides a general method to compute the magnetic helicity with discrete or continuous distributions
of magnetic field. The method sets closed and open configurations on an equal level within the same theoretical framework. 相似文献
156.
Arnaud M. Aubourg E. Bareyre P. Br';ehin S. Caridroit R. de Kat J. Dispau G. Djidi K. Gros M. Lachièze-Rey M. Laigneau Y. Laurent B. Lesquoy E. Lavocat Ph. Magneville C. Mazeau B. Milsztajn A. Moscoso L. Pasquaud J. Paul B. Perrin P. Petibon J. Piret Y. Queinnec F. Rich J. Spiro M. de Trogoff J. Vigroux L. Zylberajch S. Ansari R. Cavalier F. Moniez M. Beaulieu J. P. Ferlet R. Grison Ph. Vidal-Madjar A. Adrianzyk G. Berger J. P. Burnage R. Delclite J. C. Kohler D. Magnan R. Richaud A. Guibert J. Moreau O. Tajahmady F. Baranne A. Maurice E. Prévôt L. Gry C. 《Experimental Astronomy》1994,4(3-4):279-296
Conclusion To summarize, the readout and the control system of the CCD mosaic camera are running since December 1991 at the La Silla Observatory (ESO). The overall performance of the camera has been good. About 12000 pictures (data and flat-fields) have been successfully registered up to now. We will report in the near future preliminary scientific results of the EROS experiment. 相似文献
157.
Wolfgang Hillebrandt 《Astrophysics and Space Science》2002,281(1-2):173-182
Recent developments in theoretical model-calculations for the synthesis of the chemical elements during late stages of stellar
evolution are reviewed. Special emphasis is put on a discussion of various astrophysical sites, including core-collapse and
thermonuclear supernovae, and the physics of turbulent reactive fluids. Results of numerical simulations are presented and
discussed, together with new results concerning solar-system abundances as well as abundances observed in very metal-poor
stars, in the context of searches for constraints on the still rather uncertain nuclear physics data and astrophysical models.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
158.
159.
160.