全文获取类型
收费全文 | 661篇 |
免费 | 55篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 13篇 |
大气科学 | 60篇 |
地球物理 | 218篇 |
地质学 | 250篇 |
海洋学 | 8篇 |
天文学 | 129篇 |
综合类 | 10篇 |
自然地理 | 29篇 |
出版年
2024年 | 2篇 |
2023年 | 3篇 |
2022年 | 7篇 |
2021年 | 13篇 |
2020年 | 16篇 |
2019年 | 13篇 |
2018年 | 48篇 |
2017年 | 41篇 |
2016年 | 60篇 |
2015年 | 50篇 |
2014年 | 52篇 |
2013年 | 48篇 |
2012年 | 32篇 |
2011年 | 25篇 |
2010年 | 32篇 |
2009年 | 29篇 |
2008年 | 26篇 |
2007年 | 21篇 |
2006年 | 29篇 |
2005年 | 12篇 |
2004年 | 12篇 |
2003年 | 14篇 |
2002年 | 9篇 |
2001年 | 8篇 |
2000年 | 14篇 |
1999年 | 5篇 |
1998年 | 11篇 |
1997年 | 3篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1973年 | 3篇 |
1971年 | 2篇 |
1970年 | 1篇 |
1969年 | 2篇 |
排序方式: 共有717条查询结果,搜索用时 15 毫秒
71.
72.
Abstract— Bison LL6 chondrite is an impact breccia. The meteorite consists of unmolten clasts and accessory melt-breccia clasts incorporated into a host of the same parentage. 相似文献
73.
G. A. Galazutdinov F. A. Musaev M. R. Schmidt J. Kreowski 《Monthly notices of the Royal Astronomical Society》2001,323(2):293-300
The paper presents a survey of profiles of reasonably strong diffuse interstellar bands (DIBs) based on the extensive set of high-resolution spectra acquired with the aid of echelle spectrographs installed at the 2-m Terskol, 2-m Pic du Midi and 1-m SAO telescopes. The surveyed diffuse interstellar bands cover the spectral ranges of blue and near-infrared, i.e the DIBs not surveyed by Krełowski & Schmidt . The possible modifications caused by stellar and telluric lines are discussed. The very broad features such as 4430 are not discussed because the shapes of their profiles, extracted from echelle spectra, are very uncertain. The signal-to-noise (S/N) ratios of the spectra are not high enough to enable discussion of the profiles of numerous weak interstellar features discovered recently. 相似文献
74.
A. Megier S. Aiello B. Barsella S. Casu J. Kreowski 《Monthly notices of the Royal Astronomical Society》2001,326(3):1095-1100
We relate the equivalent widths of the major diffuse interstellar bands (DIBs) near 5797 and 5780 Å with different colour excesses, normalized by E ( B − V ) , which characterize the growth of interstellar extinction in different wavelength ranges. It is demonstrated that the two DIBs correlate best with different parts of the extinction curve, and the ratio of these diffuse bands is best correlated with the far-ultraviolet (UV) rise. A number of peculiar lines of sight are also found, indicating that the carriers of some DIBs and the far-UV extinction can be separated in certain environments, e.g. towards the Per OB2 association. 相似文献
75.
Periglacial and Fluvial Factors Controlling the Sedimentation of Pleistocene Breccia in NW Poland
下载免费PDF全文
![点击此处可从《Geografiska Annaler: Series A, Physical Geography》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Piotr Weckwerth Małgorzata Pisarska‐Jamroży 《Geografiska Annaler: Series A, Physical Geography》2015,97(2):415-430
Breccias were investigated on the terrace of the Toruń‐Eberswalde ice‐marginal valley at Rozwarzyn (NW Poland). Breccia layers include soft‐sediment clasts with diameters between 2 and 256 mm and soft‐sediment megaclasts with diameters from 256 mm to 7 m. The shape of the soft‐sediment clasts and megaclasts (derived from frozen sediments) in the breccia is diverse: from angular and irregular in the case of debris‐flow breccias to slightly rounded and tabular in fluvial breccias. These two types of breccias were developed during the Late Weichselian when the periglacial climate favored extensive lateral erosion by currents of frozen braided channels in the ice‐marginal valley. The dual presence of breccias of fluvial and debris‐flow origin in channel deposits is unique for Quaternary sediments. Zones of breccias existed in the channels where scours and obstacle marks related to megaclasts developed. The study of breccias shed new light on the fluvial processes in ice‐marginal valleys during the Pleistocene and can be considered as diagnostic for fluvio‐periglacial conditions. 相似文献
76.
77.
Krzysztof Fortuniak Włodzimierz Pawlak Mariusz Siedlecki 《Boundary-Layer Meteorology》2013,146(2):257-276
Atmospheric measurements over 5 years (2005–2010) at two sites in ?ód?, central Poland have been analyzed to develop a better understanding of turbulence in urban areas. Fast response wind velocity, temperature, humidity and CO2 concentration were measured using sonic anemometers and gas analyzers, placed on narrow masts at 37 and 42 m above the ground. The measurements were used to calculate standard deviations of each parameter, and were then normalized according to local Monin–Obukhov similarity theory and plotted as a function of stability parameter ζ = z′/L. Results for the wind components show typical scaling with a power law with exponent ±1/3 in the free convection limit, and that approaches a constant value close to neutral stratification. For stable conditions, the constant value in the neutral limit remains the same for stability parameters lower than 0.1–0.2, then increases. The normalized standard deviation of temperature fits the ?1/3 law in the free convection limit, approaching a constant value within a stable limit. However, it exhibits hyperbolic characteristics for close to neutral stratification. The normalized standard deviations for humidity and CO2 concentration exhibit scaling similar to the wind components in the unstable regime and remain constant in the stable domain. The results for the wind components and for temperature are in the range of various functions found in other studies. The absolute values for humidity and CO2 concentration seem to be slightly higher, but only single examples of such investigations can be found in the literature. 相似文献
78.
Modeling of changes in thermal bioclimate: examples based on urban spaces in Freiburg, Germany 总被引:2,自引:2,他引:0
The Place of the Old Synagogue is a popular place in the city center of Freiburg, a medium-sized city in southwest Germany. It is going to be redesigned soon. In this paper the impact of urban street design and surface material on human thermal comfort is analyzed using the example of the Place of the Old Synagogue. The models SkyHelios, RayMan, and ENVI-met were applied to quantify and qualify the changes. All three models are freely available. Their combination allows analysis of development in long-term conditions, as well as changes in spatial distribution of thermal comfort, as well as of heat stress in summer. Results show that the models can provide valuable information. About the Place of the Old Synagogue, quantitative results show that the period with heat stress will become longer, while the intensity of heat stress increases. The spatial results show that the most significant changes are due to changes in shading. Nevertheless, an increase in thermal stress up to 10 °C is calculated for areas, where ground coverage changes from grass to pavement. 相似文献
79.
Continuous flow centrifugation (CFC) is a well‐established technique used in natural surface water studies to collect large amounts of suspended solids, thus allowing a broad spectrum of measurements. However, a potential contamination or changes in the particle size distribution during the centrifugation may restrain the use of CFC effluents for element analysis in the colloidal and dissolved fractions. In this paper we evaluate the possibility of using the effluent of a Westfalia centrifuge (type KA2‐06‐075, 9700 rpm) for such analysis. This evaluation is based on two laboratory experiments with deionized and tap water and two field experiments in rivers. Elemental concentration changes across the CFC were assessed from the CFC influent and effluent after a filtration at 0·45 µm. Significant increases were found, mainly in the field experiments at a high suspended solids level and a slightly acid pH. A hypothesis was made on the origin of these increases as a superposition of a centrifuge intrinsic contamination and a particle fragmentation effect. A numerical model based on elemental concentration measurements (inductively coupled plasma mass spectrometry) gave a particle fragmentation level of 0·55% (mass percentage of particles broken up into smaller fragments during centrifugation). In another experiment, a direct particle counting (single particle counter) shows an excess of particles smaller than 500 nm in the CFC effluent, corresponding to a fragmentation level of 0·11%. In consequence, the use of CFC effluent for element analysis is possible in low‐turbidity river or lake waters, but should be carefully considered in waters with high suspended matter contents. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
80.
Sławomir Breiter 《Celestial Mechanics and Dynamical Astronomy》1997,67(3):237-249
The analytical solution for the perturbations of an artificial satellite due to the zonal part of the geopotential is presented.
The Hamiltonian is fully normalized up to the second order by a single averaging transformation and the generating function
is given explicitly. The formulas allow an arbitrarily high degree of geopotential harmonics to be included. The transformation
from mean to osculating variables or vice versa is performed by means of a numerical method proposed by the author in a previous
paper (Breiter,1997): periodic perturbations are computed by means of a Runge-Kutta method of order 2 instead of being explicitly
derived from a generator.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献