全文获取类型
收费全文 | 926篇 |
免费 | 64篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 30篇 |
大气科学 | 45篇 |
地球物理 | 344篇 |
地质学 | 330篇 |
海洋学 | 20篇 |
天文学 | 156篇 |
综合类 | 13篇 |
自然地理 | 54篇 |
出版年
2023年 | 6篇 |
2022年 | 10篇 |
2021年 | 13篇 |
2020年 | 17篇 |
2019年 | 18篇 |
2018年 | 58篇 |
2017年 | 58篇 |
2016年 | 77篇 |
2015年 | 64篇 |
2014年 | 61篇 |
2013年 | 64篇 |
2012年 | 46篇 |
2011年 | 38篇 |
2010年 | 39篇 |
2009年 | 50篇 |
2008年 | 37篇 |
2007年 | 36篇 |
2006年 | 30篇 |
2005年 | 21篇 |
2004年 | 10篇 |
2003年 | 11篇 |
2002年 | 17篇 |
2001年 | 8篇 |
2000年 | 11篇 |
1999年 | 11篇 |
1998年 | 13篇 |
1997年 | 4篇 |
1996年 | 16篇 |
1995年 | 8篇 |
1994年 | 8篇 |
1993年 | 6篇 |
1992年 | 7篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 7篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 9篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1974年 | 3篇 |
1973年 | 5篇 |
1971年 | 3篇 |
1970年 | 3篇 |
排序方式: 共有992条查询结果,搜索用时 881 毫秒
231.
232.
Konrad Miotliński 《Aquatic Geochemistry》2008,14(2):117-131
The reactive transport modeling of a complicated suite of reactions apparent in the aquifer during the application of N-containing
fertilizers is reported. The unconfined sandy aquifer can be subdivided into an oxic zone which contains groundwater with
oxygen and nitrate and an anoxic zone characterized by elevated iron and sulfate concentrations in groundwater. Oxygen and
nitrate are being reduced by pyrite and organic matter that commonly apparent in the aquifer. The oxidation of pyrite is modeled
using the local equilibrium approach, whereas decomposition of organic matter, with the adoption of kinetic approach. The
system is buffered by dissolution of aluminum and iron oxides. The modeling process is a two-step procedure. First, the processes
are modeled in the one-dimensional (1D) column using PHREEQC code. Subsequently, the calibrated and verified data were copied
and used in two-dimensional (2D) PHAST model. Prior to the performance of reactive transport modeling operations with PHAST,
a reliable flow model was executed. Finally, predictions are made for the distribution of water chemistry for the year 2008.
Model predicts that sulfate derived from the ongoing pyrite oxidation is reduced by the dissolved organic carbon at the higher
depth and forms pyrite by the reaction with iron. The results of this study highlight the importance of understanding the
interplay between the transport and chemical reactions that occur during the input of nitrate to the aquifer. Reactive transport
modeling incorporating the use of a newly developed code PHAST have proved to be a powerful tool for analyzing and quantifying
such interactions. 相似文献
233.
Bartosz Czernecki Marek Półrolniczak Leszek Kolendowicz Michał Marosz Sebastian Kendzierski Natalia Pilguj 《Journal of Atmospheric Chemistry》2017,74(1):115-139
This study investigates atmospheric conditions’ influence on the mean and extreme characteristics of PM10 concentrations in Poznań during the period 2006–2013. A correlation analysis was carried out to identify the most important meteorological variables influencing the seasonal dynamics of PM10 concentrations. The highest absolute correlation values were obtained for planetary boundary layer height (r = ?0.57), thermal (daily minimum air temperature: r = ?0.51), anemological (average daily wind speed: r = ?0.37), and pluvial (precipitation occurrence: r = ?0.36) conditions, however the highest correlations were observed for temporal autocorrelations (1 day lag: r = 0.70). As regulated by law, extreme events were identified on the basis of daily threshold value i.e. 50 μg m?3. On average, annually there are approximately 71.3 days anywhere in the city when the threshold value is exceeded, 46.6 % of those occur in winter. Additionally, 83.7 % of these cases have been found to be continuous episodes of a few days, with the longest one persisting for 22 days. The analysis of the macro-scale circulation patterns led to the identification of an easy-to-perceive seasonal relations between atmospheric fields that favour the occurrence of high PM10 concentration, as well as synoptic situations contributing to the rapid air quality improvement. The highest PM10 concentrations are a clear reaction to a decrease in air temperature by over 3 °C, with simultaneous lowering of PBL height, mean wind speed (by around 1 m s?1) and changing dominant wind directions from western to eastern sectors. In most cases, such a situation is related to the expansion of a high pressure system over eastern Europe and weakening of the Icelandic Low. Usually, air quality conditions improve along with an intensification of westerlies associated with the occurrence of low pressure systems over western and central Europe. Opposite relations are distinguishable in summer, when air quality deterioration is related to the inflow of tropical air masses originating over the Sahara desert. 相似文献
234.
Theoretical and Applied Climatology - Strong global warming has been observed in the last three decades. Central Europe, including Poland, is not an exception. Moreover, climate projections for... 相似文献
235.
The studied Carboniferous flysch and molasse sediments from the Intra-Sudetic Basin correspond to the period from Middle Visean to Early Autunian. Main magnetic minerals carrying the natural remanent magnetization (NRM) are goethite, magnetite, maghemite and hematite, all usually secondarily formed and/or remagnetized due to several tectonometamorphic events. In most samples several NRM components were isolated. One of them is usually a Jurassic-Triassic overprint. Some others define the Westphalian-Early Permian segment of the declination and inclination trajectory for the Sudetes calculated according to the reference apparent polar wander path for the Baltica plate. The Sudetic path is slightly shifted to the east compared to the reference path, suggesting the possibility of independent movements of the Sudetes during this time. The majority of isolated NRM components are secondary and related to the Sudetic orogenic phase and later tectonometamorphic activity. 相似文献
236.
237.
Summary Pre-Variscan basement in southern Poland is poorly exposed and thus known mostly from subsurface data. The availability of the latter is reviewed for terrains located between the Sudetes and the East European Platform. In these terrains the following relationships have been documented: Cadomian granitoids capped by Variscan flysch, Palaeozoic platform strata, Palaeozic folded and partly thermally altered successions, and low-grade metamorphic rocks overlain by Middle Cambrian strata. In view of their interrelationships the location of the Avalonia-Baltica suture in southeastern Poland is uncertain. 相似文献
238.
There are about 50 galactic planetary nebulae know to have [WR] type nuclei. We have compared their nebular properties with those of the other planetary nebulae in the Galaxy. We have found that the nebular morphological types are similarly distributed in the two groups. Bipolar nebulae constitute only 20% of the total in each group. The distribution of the nebular electron densities and abundance ratios N/O, He/H and C/O are the same in the two groups. The only marked difference is that nebular expansion velocities are larger in the group of planetary nebulae with [WR] central stars. We argue that the WR phenomenon does not preferentially occur in more massive central stars of planetary nebulae, contrary to what has been suggested in some former studies. We demonstrate that, for most of the observed [WR] type objects, the WR phenomenon cannot be triggered by a late helium shell flash event.The results of our investigation are published inAstronomy & Astrophysics
303, 893 (1995) and in the proceedings of the 2nd International Colloquium on Hydrogen-deficient Stars, C.S. Jeffery & U. Heber (eds), Astronomical Society of the Pacific Conference Series, Vol. 96, p. 209 (1996). 相似文献
239.
Mining in the Upper Silesian Coal Basin, Poland, induces tremors with magnitudes ranging up to 4.3. The recordings of mining tremors from the near-wave fiel and the far-wave field show different characteristics of ground motion.Knowledge of these characrteristics, has an enormous practical importance when solving the problems of resistance of underground workings against seismic impacts. The near-wave field is characterized by a domination of the high frequency components of motion, and the seismograms often are a single pulse Geomechanical interpretation of them leads to the conclusion that this pulse corresponds to a single exciting force. This fact is also reflected in the rockbursts: the potentially damaging ground motion which is restricted to the seismic source region.The seismometric data have shown that the peak particle velocities from a hypocentral distance of 200–300 m, resulted in more than 3 cm/s. The peak ground velocities appear to be dependent on stress drop , and peak particle velocities reaching 5 m/s may occur. The computational example proves that in a thick coal seam the pulse with the stress =1.8 MPa from the tremor at the short source distance can generate the rockburst. 相似文献
240.