全文获取类型
收费全文 | 622篇 |
免费 | 12篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 17篇 |
大气科学 | 49篇 |
地球物理 | 283篇 |
地质学 | 113篇 |
海洋学 | 2篇 |
天文学 | 151篇 |
综合类 | 1篇 |
自然地理 | 20篇 |
出版年
2018年 | 11篇 |
2017年 | 13篇 |
2016年 | 17篇 |
2015年 | 12篇 |
2014年 | 21篇 |
2013年 | 22篇 |
2012年 | 17篇 |
2011年 | 29篇 |
2010年 | 21篇 |
2009年 | 14篇 |
2008年 | 12篇 |
2007年 | 16篇 |
2006年 | 17篇 |
2005年 | 16篇 |
2004年 | 8篇 |
2003年 | 8篇 |
2002年 | 9篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1999年 | 16篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1996年 | 16篇 |
1995年 | 16篇 |
1994年 | 15篇 |
1993年 | 7篇 |
1992年 | 12篇 |
1991年 | 10篇 |
1990年 | 16篇 |
1989年 | 22篇 |
1988年 | 11篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 11篇 |
1984年 | 12篇 |
1983年 | 9篇 |
1982年 | 8篇 |
1981年 | 11篇 |
1980年 | 10篇 |
1978年 | 11篇 |
1976年 | 7篇 |
1975年 | 6篇 |
1974年 | 6篇 |
1973年 | 6篇 |
1971年 | 10篇 |
1970年 | 7篇 |
1969年 | 8篇 |
1963年 | 5篇 |
1960年 | 5篇 |
1957年 | 5篇 |
排序方式: 共有636条查询结果,搜索用时 265 毫秒
591.
Vladimír Čermák Louise Bodri Jan Šafanda Milan Krešl Petr Dědeček 《Studia Geophysica et Geodaetica》2014,58(3):403-424
Long-term observations of air, near-surface (soil) and ground temperatures, collected between 1994 and 2011, monitored in the Geothermal Climate Change Observatory at Spo?ilov, Prague (GCCO) are analyzed to better understand the relationship between these quantities and to describe the mechanism of heat transport at the land-atmosphere boundary layer. The 17 years long monitoring series provided a surprisingly small mean ground-air temperature offset of only 0.31 K with no clear annual course and with the offset value changing irregularly even on a daily scale. Such value is substantially lower than similar values (1–2 K and more) found elsewhere, but it may be well characteristic for a mild temperate zones, when all so far available information referred rather to more southern locations. As many other observed geophysical data, temperature time series consist of a systematic pattern (usually a set of identifiable components) contaminated by random noise, which makes the identification of the proper pattern difficult. To identify the existing systematic patterns (cycles) of the temperature-time series at several depth levels in the investigated depth interval 0–40 m, the observed data were processed with the help of the Fast Fourier Transform (FFT) and Recurrence Quantification Interval (RQI) analysis. The latter represents recently developed powerful technique to uncover hidden periodicities in a noisy time environment. At low frequency band the RQI may provide far finer resolution than the conventional FFT technique. The results proved considerable similarity for all investigated depth levels. In addition to the annual wave all measured series proved to have a more complex pattern including predominantly 8-year and 11 years long periodicities. The results were compared with similar analysis of the meteorological air temperature series as well as with the results of other similar studies. The potential dynamics explaining the occurrence of the 8-year wave is briefly discussed. 相似文献
592.
Eva Holtanová Jaroslava Kalvová Jiří Mikšovský Petr Pišoft Martin Motl 《Studia Geophysica et Geodaetica》2010,54(3):513-528
In this study we present results of uncertainty analysis in eight regional climate model (RCM) outputs over the area of the
Czech Republic. The RCM simulations come from the EU 5th Framework program project PRUDENCE (Prediction of Regional scenarios
and Uncertainties for Defining EuropeaN Climate change risks and Effects). Using the analysis of variance we have found that
the main source of uncertainty in projected changes of mean seasonal air temperature is the driving global climate model.
In case of precipitation changes, the RCM is the largest source of uncertainty in all seasons except for the spring. With
the second method, the Reliability Averaging method, we have focused on the uncertainty coming from the RCM itself. The results
of both methods showed that the relative contribution of the regional climate model to the uncertainty of simulated mean seasonal
air temperature and precipitation changes is largest in summer and smallest in winter. 相似文献
593.
Petr Pruner Nadja Zupan Hajna Andrej Mihevc Pavel Bosák Otakar Man Petr Schnabl Daniela Venhodová 《Studia Geophysica et Geodaetica》2010,54(1):27-48
Clastic and chemogenic cave sediments were sampled and analyzed from Račiška pečina and Pečina v Borštu caves of southwestern
Slovenia. Samples were subjected to both thermal and alternating field demagnetization; specimens belonging to the same sample
of the same layer produce identical results. Unblocking temperatures of 540 to 560°C on average suggests magnetite as the
principal carrier of magnetization. These directions also pass a reversals test indicating the demagnetization results are
free of secondary overprints and have adequately averaged out paleosecular variation. Normally magnetized clays containing
fauna belonging to the MN17 mammal biozone at a depth of ∼ 4 m in Račiška pecina cave indicate these clays were deposited
at the beginning of the Olduvai subchron (1.95 Ma). Correlation with the Geomagnetic Polarity Time Scale (GPTS) indicates
the base of the speleothems in Račiška pečina terminate in the upper part of subchron C2An.3n with numerous breaks in deposition,
lasting up to 250 ka and more. Therefore rates of speleothem growth cannot be calculated. Fold tests on dome-like stalagmites
of differing sizes and ages (Pleistocene, Pliocene) from the two caves indicate the domelike structures are primary. 相似文献
594.
595.
Zbyněk Engel Grzegorz Skrzypek Debajyoti Paul Wojciech Drzewicki Daniel Nývlt 《Journal of Paleolimnology》2010,43(4):609-624
This study presents detailed lithostratigraphy and stable carbon and nitrogen isotopic variations in a 520-cm-long sediment
core from a cirque basin in the Labsky důl Valley, Krkonoše Mountains, Czech Republic. Detailed study of the core reveals
five major periods of sedimentation during the last 7600 years: silt and sand deposition during ~7.6–5.1 ka cal BP, Sphagnum peat accumulation during ~5.1–4.0 ka cal BP, sandy silt and sand during ~4.0–2.8 ka cal BP, raised peat bog during ~2.8–2.0 ka cal
BP (Sphagnum peat), and sedimentation of sandy silt since ~2.0 ka cal BP. The δ13C values of the organic matter in the core vary in the range typical for C3 plants, from −24.35 to −27.68‰, whereas the δ15N values vary from −2.65 to +4.35‰. Core sections having ash contents ≥70% have δ15N > 1‰ and δ13C < −26‰, whereas those having ≤70% ash content have δ15N < 1‰ and δ13C > −26‰. Strong linear correlations are observed between δ13C and δ15N values as well as between C:N ratios and δ15N values in the horizons with ash content >10%, primarily for sand and silt horizons. On the other hand, poor correlations
between δ13C and C:N ratio, as well as δ15N and C:N ratio, were observed in Sphagnum peat layers (45–125 and 185–265 cm). We conclude that the primary stable isotope variations are not preserved in the layers
where significant correlation between δ15N and C:N ratio is observed. The relatively small δ13C variation in the uppermost Sphagnum peat layer suggests stable temperature during ~2.8–2.0 ka cal BP. 相似文献
596.
The first results of the almost one year drop size distribution (DSD) measurement in the Czech Republic are summarised in this study. The ESA-ESTEC 2D videodistrometer was used to measure the rain drop parameters. The average DSD is shown to be of the gamma type. One minute DSDs were evaluated to test the accuracy of analytical DSD models. Parameters of gamma distribution and exponential distribution functions were evaluated for the whole data set as well as for the various rain rate intervals. Regression technique and the method of moments were applied to estimate the parameters of DSD. It is shown that the parameter value strongly depends on the method of computation as well as on the rain type. Its average value is about 0.59 for the average (smooth) one minute DSD while an average value of un-smoothed DSD is 11.0 (moment method) or 5.4 (regression technique). The Joss's shape parameter and the Tokay-Short's parameter CS estimating roughly the rain type are also discussed (if CS>1, the event should be convective). The tendency of increasing numerical value of the CS parameter with the increasing rain rate was observed (the DSDs were distributed into classes respecting the rain rate value) and thus the idea of the convectivity occurrence bounded with the higher CS parameter value was supported. The study also compares the parameters of the average DSD with the averages of parameter values of all 4 183 one minute DSDs. 相似文献
597.
S. Ferraz-Mello J. C. Klafke T. A. Michtchenko D. Nesvorný 《Celestial Mechanics and Dynamical Astronomy》1996,64(1-2):93-105
The utilization of chaotic dynamics approaches allowed the identification of many modes of motion in resonant asteroidal dynamics. As these dynamical systems are not integrable, the motion modes are not separated and one orbit may transit from one mode to another. In some cases, as in the \31 resonance, these transitions may lead, in a relatively short time scale, to eccentricities so high that the asteroid may approach the Sun and be destroyed. In the \21 and \32 resonances these transitions are much slower and only indirect estimations of the time which is needed for a generic asteroid to leave the resonance are possible. It may reach hundreds of million years in the more robust regions of the \21 resonance and a time of the order of billions of years in those of the \32 resonance. These values are consistent with the observed depletion of the \21 resonance (only a few asteroids known while almost 60 asteroids are known in the \32 resonance). 相似文献
598.
599.
600.
The north-south (N-S) asymmetry of the solar activity (A), which reflects differences in the behavior of the northern and southern hemispheres of the Sun, is studied using data on the brightness of the coronal green line, the total number and area of sunspots, and the net magnetic flux. The spatial and temporal distributions and correlations between the A values represented by these indices are considered. The characteristic time variations in A are similar for all the indices, on both long and short time scales. Quasibiennial oscillations (QBOs) can be traced in the asymmetries of all four indices. A detailed study of the QBOs is carried out based on spectral-variation and wavelet analyses. Long-term increases and decreases occur synchronously in the asymmetries of various indices and are much more pronounced in A than in the indices themselves. A negative correlation between the power of the QBOs and the asymmetry of A can be traced; it is most clearly manifest as a substantial diminishing of the QBOs during the mid-1960s, which coincided with an especially strong increase in A. Our analysis shows that the N-S asymmetry is probably a fundamental property that controls the coupling and degree of coincidence between the magnetic-field-generation mechanisms operating in the northern and southern hemispheres. 相似文献