全文获取类型
收费全文 | 400篇 |
免费 | 17篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 12篇 |
大气科学 | 37篇 |
地球物理 | 152篇 |
地质学 | 115篇 |
海洋学 | 40篇 |
天文学 | 50篇 |
自然地理 | 16篇 |
出版年
2022年 | 6篇 |
2021年 | 6篇 |
2020年 | 5篇 |
2019年 | 4篇 |
2018年 | 10篇 |
2017年 | 14篇 |
2016年 | 18篇 |
2015年 | 17篇 |
2014年 | 27篇 |
2013年 | 34篇 |
2012年 | 19篇 |
2011年 | 27篇 |
2010年 | 20篇 |
2009年 | 42篇 |
2008年 | 22篇 |
2007年 | 14篇 |
2006年 | 13篇 |
2005年 | 13篇 |
2004年 | 8篇 |
2003年 | 7篇 |
2002年 | 10篇 |
2001年 | 6篇 |
2000年 | 6篇 |
1999年 | 4篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 7篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1983年 | 4篇 |
1981年 | 2篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1958年 | 3篇 |
1956年 | 2篇 |
1955年 | 3篇 |
1954年 | 1篇 |
1953年 | 2篇 |
1952年 | 2篇 |
1951年 | 3篇 |
1950年 | 3篇 |
1949年 | 1篇 |
1948年 | 1篇 |
1946年 | 2篇 |
1945年 | 1篇 |
1944年 | 3篇 |
排序方式: 共有422条查询结果,搜索用时 359 毫秒
141.
On the equations of the dynamics of the attracting point masses 相似文献
142.
We evaluate the expected level of foreground contamination to the cosmic microwave background (CMB) polarised radiation, focusing on the diffuse emission from our own Galaxy. In particular, we perform a first attempt to simulate an all sky template of polarised emission from thermal dust. This study indicates that the foreground contamination to CMB B-modes is likely to be relevant on all frequencies, and even at high Galactic latitudes. We review the recent developments in the design of data analysis techniques dedicated to the separation of CMB and foreground emissions in multi-frequency observations, exploiting their statistical independence. We argue that the high quality and detail of the present CMB observations represent an almost ideal statistical dataset where these algorithms can operate with excellent performance. We explicitly show that the recovery of CMB B-modes is possible even if they are well below the foreground level, working at the arcminute resolution at an almost null computational cost. This capability well represents the great potentiality of these new data analysis techniques, which should be seriously taken into account for implementation in present and future CMB observations. 相似文献
143.
Parolai Stefano Lai Carlo G. Dreossi Ilaria Ktenidou Olga-Joan Yong Alan 《Journal of Seismology》2022,26(4):823-862
Journal of Seismology - Seismic attenuation and the associated quality factor (Q) have long been studied in various sub-disciplines of seismology, ranging from observational and engineering... 相似文献
144.
Cauzzi Carlo Fäh Donat Wald David J. Clinton John Losey Stéphane Wiemer Stefan 《Natural Hazards》2018,92(2):1211-1235
Natural Hazards - In Switzerland, nearly all historical Mw?~?6 earthquakes have induced damaging landslides, rockslides and snow avalanches that, in some cases, also resulted in damage... 相似文献
145.
Is the westerly rotation of the lithosphere an ephemeral accidental recent phenomenon or is it a stable process of Earth's geodynamics? The reason why the tidal drag has been questioned as the mechanism determining the lithospheric shift relative to the underlying mantle is the apparent too high viscosity of the asthenosphere. However, plate boundaries asymmetries are a robust indication of the ‘westerly’ decoupling of the entire Earth's outer lithospheric shell and new studies support lower viscosities in the low-velocity layer (LVZ) atop the asthenosphere. Since the solid Earth tide oscillation is longer in one side relative to the other due to the contemporaneous Moon's revolution, we demonstrate that a non-linear rheological behavior is expected in the lithosphere mantle interplay. This may provide a sort of ratchet favoring lowering of the LVZ viscosity under shear, allowing decoupling in the LVZ and triggering the westerly motion of the lithosphere relative to the mantle. 相似文献
146.
Investigating the association between streetscapes and human walking activities using Google Street View and human trajectory data 总被引:1,自引:0,他引:1 下载免费PDF全文
Xiaojiang Li Paolo Santi Theodore K. Courtney Santosh K. Verma Carlo Ratti 《Transactions in GIS》2018,22(4):1029-1044
Having an active lifestyle is recognized to positively contribute to public health. Creating more walkable streets and neighborhoods is an important way to promote an active lifestyle for urban residents. It is therefore important to understand how the urban built environment can influence human walking activities. In this study, we investigated the interaction of human walking activities and physical characteristics of streetscapes in Boston. A large number of anonymous pedestrian trajectories collected from a smartphone application were used to estimate human walking activities. Publicly accessible Google Street View images were used to estimate the amount of street greenery and the enclosure of street canyons, both of which were used to indicate the physical characteristics of streetscapes. The Walk Score and population were also added in the statistical analyses to control the influence of nearby urban facilities and population on human walking activities. Statistical analysis results show that both the street greenery and the enclosure of the street canyons are significantly associated with human walking activities. The associations between the streetscape variables and human walking activities vary in different land use types. The results of this study have implications for designing walkable and healthy cities. 相似文献
147.
Waldo Sven Lavado Casimiro Josyane Ronchail David Labat Jhan Carlo Espinoza Jean Loup Guyot 《水文科学杂志》2013,58(4):625-642
Abstract We present a procedure for estimating Q95 low flows in both gauged and ungauged catchments where Q95 is the flow that is exceeded 95% of the time. For each step of the estimation procedure, a number of alternative methods was tested on the Austrian data set by leave-one-out cross-validation, and the method that performed best was used in the final procedure. To maximise the accuracy of the estimates, we combined relevant sources of information including long streamflow records, short streamflow records, and catchment characteristics, according to data availability. Rather than deriving a single low flow estimate for each catchment, we estimated lower and upper confidence limits to allow local information to be incorporated in a practical application of the procedure. The components of the procedure consist of temporal (climate) adjustments for short records; grouping catchments into eight seasonality-based regions; regional regressions of low flows with catchment characteristics; spatial adjustments for exploiting local streamflow data; and uncertainty assessment. The results are maps of lower and upper confidence limits of low flow discharges for 21 000 sub-catchments in Austria. 相似文献
148.
Observations and box model analysis of radon-222 in the atmospheric surface layer at L’Aquila,Italy: March 2009 case study 总被引:1,自引:1,他引:0
Giovanni Pitari Eleonora Coppari Natalia De Luca Piero Di Carlo 《Environmental Earth Sciences》2014,71(5):2353-2359
Two years of radon-222 observations collected at L’Aquila (Italy) in the atmospheric surface layer during 2004–2006 were analyzed in correlation with meteorological data and other atmospheric tracers. A box model was developed to better understand the mechanisms of diurnal and seasonal variability of the tracer and to indirectly assess the magnitude of the monthly averaged radon soil flux in the L’Aquila measurement site. The model was successfully validated with measurements, with a 0.8 average correlation coefficient between hourly values for the whole period of radon observations. Measurements taken during March 2009 were analyzed to find possible signs of perturbation due to the ongoing seismic activity that would have reached its peak on the 6 April 2009 destructive earthquake. Contrary to the professed (and unpublished) dramatic increases of radon activity unofficially announced to the inhabitants at that time, the study presented here shows that no radon activity increase took place in L’Aquila with respect to a previous ‘seismically unperturbed’ year (same month with similar meteorological conditions), but that an average 30 % decrease was experienced. This conclusion is reached from a direct comparison of observed data and also as a result of the previously validated radon box model constrained by actual meteorological data, from which an indirect estimate of a 17 % reduction of the radon soil flux is obtained. 相似文献
149.
Sara Cristina Teresa Trianni Carlo Giovanni Lai Erio Pasqualini 《Natural Hazards》2014,74(3):1683-1705
Probabilistic seismic hazard analysis (PSHA) along the route of an offshore pipeline for the transport of oil in the Bay of Bengal has been performed, in order to set up design parameters and identify possible geohazards. The complexity of geological and seismotectonic setting of the region where the pipeline is planned to be installed is the result of the interaction of the Indian, Eurasian and Burmese tectonic plates. In order to properly account for the intricate way by which these plates interact, a large area extending 450 km from the pipeline route has been considered for the compilation of a comprehensive earthquake catalogue, spanning the period 1663–2012 AD. Differently from earlier PSHA analyses conducted in the region based on assuming two-dimensional polygons as seismogenic provinces, this study adopted a seismotectonic source model which also includes for the first time a linear tectonic lineament representing the northward extension of the Sunda mega thrust, responsible for the large Sumatra–Andaman earthquake of 26 December 2004. Hazard computations have been performed over a grid of sites spaced 0.045° covering a rectangular area which contains the pipeline. Epistemic uncertainty in the hazard computations has been taken into account by a logic tree framework, incorporating different seismotectonic source models, maximum cut-off magnitude and ground-motion prediction equations. Horizontal median uniform hazard spectra and median uniform hazard spectra plus and minus one sigma on stiff ground have been calculated at the selected sites for different return periods. Peak ground acceleration with 10 % probability of exceedance in 50 years has been compared with values from previous hazard studies available for Bangladesh. 相似文献
150.
Abstract The present stalemate in climate negotiations between the USA and the other Annex I countries has led policy analysts and economists to explore the possible emergence of alternative climate regimes that may be applied after 2012. This article explores the idea of replacing international cooperation on greenhouse gas emission control with international cooperation on climate-related technological innovation and diffusion. This idea—recently proposed among others by Barrett (2001) and Benedick (2001)—is based on the insight that incentives to free-ride are much smaller in the case of technological cooperation than in the case of cooperation on emission control. This article provides a first applied game theory analysis of a technology-based climate protocol by assessing: (i) the self-enforcingness (namely, the absence of incentives to free-ride) of the coalition that would form when countries negotiate on climate-related technological cooperation; (ii) the environmental effectiveness of a technology-based climate protocol. The analysis is carried out by using a model in which endogenous and induced technical change are explicitly modelled. The results of our analysis partly support Barrett's and Benedick's conjectures. On the one hand, a self-enforcing agreement is more likely to emerge when countries cooperate on environmental technological innovation and diffusion than when they cooperate on emission abatement. However, technological cooperation—without any commitment to emission control—may not lead to a sufficient abatement of greenhouse gas concentrations. 相似文献