全文获取类型
收费全文 | 413篇 |
免费 | 23篇 |
专业分类
测绘学 | 39篇 |
大气科学 | 43篇 |
地球物理 | 110篇 |
地质学 | 89篇 |
海洋学 | 16篇 |
天文学 | 118篇 |
综合类 | 1篇 |
自然地理 | 20篇 |
出版年
2021年 | 7篇 |
2020年 | 14篇 |
2019年 | 9篇 |
2018年 | 17篇 |
2017年 | 19篇 |
2016年 | 24篇 |
2015年 | 18篇 |
2014年 | 21篇 |
2013年 | 41篇 |
2012年 | 20篇 |
2011年 | 24篇 |
2010年 | 17篇 |
2009年 | 27篇 |
2008年 | 21篇 |
2007年 | 15篇 |
2006年 | 12篇 |
2005年 | 13篇 |
2004年 | 7篇 |
2003年 | 4篇 |
2002年 | 3篇 |
2001年 | 4篇 |
2000年 | 7篇 |
1998年 | 7篇 |
1997年 | 5篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1992年 | 2篇 |
1990年 | 3篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1970年 | 2篇 |
1969年 | 2篇 |
1968年 | 3篇 |
1961年 | 1篇 |
1958年 | 1篇 |
1933年 | 1篇 |
1931年 | 1篇 |
排序方式: 共有436条查询结果,搜索用时 31 毫秒
241.
The time-dependent response of climate changes to changing atmospheric concentration of carbon dioxide is modeled using an
energy balance atmospheric model coupled to a one-dimensional upwelling diffusion model of the deep ocean. Such a model introduces
time delays so that the calculated globally-averaged temperature lags that which would be predicted by assuming radiative
equilibrium. The climate model is coupled to a simple carbon cycle model and a ‘social’ model that simulates decreasing emission
in response to increasing global temperatures. The thermal inertia of the system is such that temperatures continue to increase
after carbon dioxide concentrations are decreasing.
Consultant to BNL from New York University.
Semester Student, Fall 1979, Alcorn State College.
This research was performed under the auspices of the United States Department of Energy under Contract No. DE-AC02-76CH00016.
By acceptance of this article, the publisher and/or recipient acknowledges the U.S. Government’s right to retain a nonexclusive,
royalty-free license in and to any copyright covering this paper. 相似文献
242.
243.
Why does a sunspot look the way it does? Steven Tobias and Nigel Weiss find answers to this question, by relating new high-resolution observations to recent theoretical studies of the spot's magnetic field. 相似文献
244.
Freezing of rainwater on a surface is often caused by nocturnal clearing after precipitation, which goes along with radiative cooling. Forecasting cloudiness, and especially the risk of clearing, on a scale of 1 to 3 h is of interest in the domains of road weather, agriculture, or water management.Cloud amount and the difference between air and surface temperature are important parameters of the radiation balance. In this contribution, we show the relationship between them, proved at several stations all over Switzerland. We found a correlation coefficient of 0.88 and improved it considering other meteorological parameters like wind speed. We conclude that temperature difference is a signature for nocturnal cloudiness.We investigated nocturnal cloudiness for a case from winter 2001/02 in northern Switzerland. An ultra-dense combination of two networks with 70 stations in total is operated, measuring air and surface temperature, wind and other parameters. With the aid of our equations, these measurements where converted into cloud maps, including also precipitation seen by radar. We identified a frontal precipitation area, postfrontal clearing, freezing, and the first clouds of a following frontal passage.All these findings will contribute to a better observation and predictability of surface state and other risks connected with radiative cooling. 相似文献
245.
Some effects of lateral heterogeneities in the upper mantle on postglacial land uplift close to continental margins 总被引:2,自引:0,他引:2
We investigate the effects of lateral heterogeneities in the upper mantle on the calculation of postglacial land uplift. For the model calculations we use a commercial finite-element code, which enables us to solve the equations governing a layered, isotropic. incompressible, Maxwell-viscoelastic half-space with laterally varying layer thicknesses and physical properties. Following previous investigations performed by Sabadini. Yuen & Portney (1986) and Gasperini & Sabadini (1989), we extend their results using a more realistic loading history and different earth models. We then focus our attention on the question whether lateral heterogeneities in the upper mantle can be modelled correctly using a set of homogeneous earth models. To this end, a comparison of model calculations using both laterally homogeneous and heterogeneous earth models is performed.
We find that lateral heterogeneities in the upper mantle significantly influence the calculated postglacial land uplift. The resolving power of relative sea-level observations for the prescribed lateral heterogeneities used in this study is mainly focused on observations around the load margin and outside the glaciated areas, where differences in predicted land uplift between individual models are large enough to be resolved by observations.
We can qualitatively determine lateral heterogeneities in the upper mantle using a set of laterally homogeneous earth models, if the geological structure, for example a continental margin, is known. However, in order to infer the correct values of lithospheric thickness and asthenospheric viscosity, we need to use laterally heterogeneous models. 相似文献
We find that lateral heterogeneities in the upper mantle significantly influence the calculated postglacial land uplift. The resolving power of relative sea-level observations for the prescribed lateral heterogeneities used in this study is mainly focused on observations around the load margin and outside the glaciated areas, where differences in predicted land uplift between individual models are large enough to be resolved by observations.
We can qualitatively determine lateral heterogeneities in the upper mantle using a set of laterally homogeneous earth models, if the geological structure, for example a continental margin, is known. However, in order to infer the correct values of lithospheric thickness and asthenospheric viscosity, we need to use laterally heterogeneous models. 相似文献
246.
Comparing statistical estimates for the long-run temperature effect of doubled CO2 with those generated by climate models begs the question, is the long-run temperature effect of doubled CO2 that is estimated from the instrumental temperature record using statistical techniques consistent with the transient climate response, the equilibrium climate sensitivity, or the effective climate sensitivity. Here, we attempt to answer the question, what do statistical analyses of the observational record measure, by using these same statistical techniques to estimate the temperature effect of a doubling in the atmospheric concentration of carbon dioxide from seventeen simulations run for the Coupled Model Intercomparison Project 2 (CMIP2). The results indicate that the temperature effect estimated by the statistical methodology is consistent with the transient climate response and that this consistency is relatively unaffected by sample size or the increase in radiative forcing in the sample. 相似文献
247.
An understanding of the formation of shear fractures is important in many rock engineering design problems. Laboratory experiments
have been performed to determine the Mode II fracture toughness of Mizunami granite rock samples using a cylindrical `punch-through'
testing device. In this paper we attempt to understand and interpret the experimental results by numerical simulation of the
fundamental shear fracture initiation and coalescence processes, using a random array of displacement discontinuity crack
elements. It is found that qualitative agreement between the experimental and numerical results can be established, provided
that shear-like micro-scale failure processes can be accommodated by the failure initiation rules that are used in the numerical
simulations. In particular, it is found that the use of an exclusively tension-driven failure initiation rule does not allow
the formation of macro-shear structures. It is apparent, also, that further investigation is required to determine how consistent
rules can be established to link micro-failure criteria to equivalent macro-strength and toughness properties for a macro-shear
slip surface. 相似文献
248.
The Helios spacecraft zodiacal light photometers are used to observe the earthward-directed solar mass ejection transient of 27 November, 1979 described by Howard et al. (1982) that completely circles the Sun in coronagraph observations. At this time, Helios B was situated 30° east of the Sun-Earth line at 0.5 AU. The brightness increase moved outward directly along the Sun-Earth line over a period of approximately 24 hr, indicating a strong collimation of the ejection. The outward motion and mass estimates of the ejected material from the photometers compared with near-Earth observations from IMP spacecraft show that at least a portion of the density increase observed at Earth on 29 and 30 November was associated with this ejection. 相似文献
249.
Some relationships between solar X-ray bursts and SPA's produced on VLF propagation in the lower ionosphere 总被引:1,自引:0,他引:1
This paper discusses SPA's measured at long VLF propagation paths in the lower ionosphere and their association with solar X-ray bursts observed by USNRL satellites in the 0–3 Å, 0–8 Å and 8–20 Å bands. Excellent correlations were found between the SPA importances (in degrees per Mm) and the logarithm of the X-ray burst peak intensities. A hardening of the X-ray burst spectra is evident for increasing importance of SPA's; the threshold energy required for the occurrence of such anomalies was estimated, it is 4.3×10?5 ergs cm?2 sec?1 in the main ionizing band of 0–3 Å. It was also possible to derive the effective recombination coefficient at the normal D-region height of 70 km, this beingα r≈6×10?6 cm3 sec?1; furthermore ion production rates were estimated during SPA's at heights below the reference level. 相似文献
250.
Tobias Diehl John Clinton Nicolas Deichmann Carlo Cauzzi Philipp Kästli Toni Kraft Irene Molinari Maren Böse Clotaire Michel Manuel Hobiger Florian Haslinger Donat Fäh Stefan Wiemer 《Swiss Journal of Geoscience》2018,111(1-2):221-244
This report summarizes the seismicity in Switzerland and surrounding regions in the years 2015 and 2016. In 2015, the Swiss Seismological Service detected and located 735 earthquakes in the region under consideration. With a total of 20 earthquakes of magnitude ML ≥ 2.5, the seismic activity of potentially felt events in 2015 was close to the average of 23 earthquakes over the previous 40 years. Seismic activity was above average in 2016 with 872 located earthquakes of which 31 events had ML ≥ 2.5. The strongest event in the analyzed period was the ML 4.1 Salgesch earthquake, which occurred northeast of Sierre (VS) in October 2016. The event was felt in large parts of Switzerland and had a maximum intensity of V. Derived focal mechanisms and relative hypocenter relocations of aftershocks image a SSE dipping reverse fault, which likely also hosted an ML 3.9 earthquake in 2003. Another remarkable earthquake sequence in the Valais occurred close to Sion with four felt events (ML 2.7–3.2) in 2015/16. We associate this sequence with a system of WNW-ESE striking fault segments north of the Rhône valley. Similarities with a sequence in 2011, which was located about 10 km to the NE, suggest the existence of an en-echelon system of basement faults accommodating dextral slip along the Rhône-Simplon line in this area. Another exceptional earthquake sequence occurred close to Singen (Germany) in November 2016. Relocated hypocenters and focal mechanisms image a SW dipping transtensional fault segment, which is likely associated with a branch of the Hegau-Bodensee Graben. On the western boundary of this graben, micro-earthquakes close to Schlattingen (TG) in 2015/16 are possibly related to a NE dipping branch of the Neuhausen Fault. Other cases of earthquakes felt by the public during 2015/16 include earthquakes in the region of Biel, Vallorcine, Solothurn, and Savognin. 相似文献