全文获取类型
收费全文 | 383篇 |
免费 | 7篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 14篇 |
大气科学 | 25篇 |
地球物理 | 78篇 |
地质学 | 157篇 |
海洋学 | 12篇 |
天文学 | 91篇 |
自然地理 | 17篇 |
出版年
2023年 | 2篇 |
2020年 | 3篇 |
2019年 | 7篇 |
2018年 | 8篇 |
2017年 | 5篇 |
2016年 | 7篇 |
2015年 | 12篇 |
2014年 | 21篇 |
2013年 | 14篇 |
2012年 | 11篇 |
2011年 | 17篇 |
2010年 | 18篇 |
2009年 | 29篇 |
2008年 | 20篇 |
2007年 | 22篇 |
2006年 | 21篇 |
2005年 | 18篇 |
2004年 | 11篇 |
2003年 | 28篇 |
2002年 | 17篇 |
2001年 | 7篇 |
2000年 | 8篇 |
1999年 | 10篇 |
1998年 | 7篇 |
1997年 | 7篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1988年 | 2篇 |
1986年 | 4篇 |
1984年 | 3篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1975年 | 2篇 |
1971年 | 3篇 |
1970年 | 2篇 |
1967年 | 3篇 |
1958年 | 2篇 |
1956年 | 2篇 |
1953年 | 1篇 |
1952年 | 1篇 |
1951年 | 1篇 |
1950年 | 2篇 |
1949年 | 1篇 |
1948年 | 1篇 |
1942年 | 1篇 |
1940年 | 1篇 |
1939年 | 1篇 |
排序方式: 共有394条查询结果,搜索用时 468 毫秒
191.
192.
193.
Vertical deformations from homogeneously processed GRACE and global GPS long-term series 总被引:3,自引:1,他引:2
Volker Tesmer Peter Steigenberger Tonie van Dam Torsten Mayer-Gürr 《Journal of Geodesy》2011,85(5):291-310
Temporal variations in the geographic distribution of surface mass cause surface displacements. Surface displacements derived
from GRACE gravity field coefficient time series also should be observed in GPS coordinate time series, if both time series
are sufficiently free of systematic errors. A successful validation can be an important contribution to climate change research,
as the biggest contributors to mass variability in the system Earth include the movement of oceanic, atmospheric, and continental
water and ice. In our analysis, we find that if the signals are larger than their precision, both geodetic sensor systems
see common signals for almost all the 115 stations surveyed. Almost 80% of the stations have their signal WRMS decreased,
when we subtract monthly GRACE surface displacements from those observed by GPS data. Almost all other stations are on ocean
islands or small peninsulas, where the physically expected loading signals are very small. For a fair comparison, the data
(79 months from September 2002 to April 2009) had to be treated appropriately: the GPS data were completely reprocessed with
state-of-the-art models. We used an objective cluster analysis to identify and eliminate stations, where local effects or
technical artifacts dominated the signals. In addition, it was necessary for both sets of results to be expressed in equivalent
reference frames, meaning that net translations between the GPS and GRACE data sets had to be treated adequately. These data
sets are then compared and statistically analyzed: we determine the stability (precision) of GRACE-derived, monthly vertical
deformation data to be ~1.2 mm, using the data from three GRACE processing centers. We statistically analyze the mean annual
signals, computed from the GPS and GRACE series. There is a detailed discussion of the results for five overall representative
stations, in order to help the reader to link the displayed criteria of similarity to real data. A series of tests were performed
with the goal of explaining the remaining GPS–GRACE residuals. 相似文献
194.
On the crystal structure and compressional behavior of talc: a mineral of interest in petrology and material science 总被引:1,自引:1,他引:0
G. Diego Gatta Marco Merlini Giovanni Valdrè Hanns-Peter Liermann Gwilherm Nénert André Rothkirch Volker Kahlenberg Alessandro Pavese 《Physics and Chemistry of Minerals》2013,40(2):145-156
The crystal structure of a natural triclinic talc (1Tc polytype) [with composition: (Mg2.93Fe0.06)Σ2.99(Al0.02Si3.97)Σ3.99O10(OH)2.10] has been investigated by single-crystal X-ray diffraction at 223 and 170 K and by single-crystal neutron diffraction at 20 K. Both the anisotropic X-ray refinements (i.e. at 223 and 170 K) show that the two independent tetrahedra are only slightly distorted. For the two independent Mg-octahedra, the bond distances between cation-hydroxyl groups are significantly shorter than the others. The ditrigonal rotation angle of the six-membered ring of tetrahedra is modest (α ~ 4°). The neutron structure refinement shows that the hydrogen-bonding scheme in talc consists of one donor site and three acceptors (i.e. trifurcated configuration), all the bonds having O···O ≤ 3.38 Å, H···O ~ 2.8 Å, and O–H···O ~ 111–116°. The three acceptors belong to the six-membered ring of tetrahedra juxtaposed to the octahedral sheet. The vibrational regime of the proton site appears being only slightly anisotropic. The elastic behavior of talc was investigated by means of in situ synchrotron single-crystal diffraction up to 16 GPa (at room temperature) using a diamond anvil cell. No evidence of phase transition has been observed within the pressure range investigated. P–V data fit, with an isothermal third-order Birch-Murnaghan equation of state, results as follows: V 0 = 454.7(10) Å3, K T0 = 56(3) GPa, and K′ = 5.4(7). The “Eulerian finite strain” versus “normalized stress” plot yields: Fe(0) = 56(2) GPa and K′ = 5.3(5). The compressional behavior of talc is strongly anisotropic, as reflected by the axial compressibilities (i.e. β(a):β(b):β(c) = 1.03:1:3.15) as well as by the magnitude and orientation of the unit-strain ellipsoid (with ε 1:ε 2:ε 3 = 1:1.37:3.21). A comparison between the elastic parameters of talc obtained in this study with those previously reported is carried out. 相似文献
195.
Abdolnaser Fazlnia Volker Schenk Peter Appel Abouzar Alizade 《International Journal of Earth Sciences》2013,102(5):1403-1426
The Chah-Bazargan gabbroic intrusions are located in the south of Sanandaj–Sirjan zone. Precise U–Pb zircon SHRIMP ages of the intrusions show magmatic ages of 170.5 ± 1.9 Ma. These intrusions consist primarily of gabbros, interspersed with lenticular bodies of anorthosite, troctolite, clinopyroxenite, and wehrlite. The lenticular bodies show gradational or sharp boundaries with the gabbros. In the gradational boundaries, gabbros are mineralogically transformed into anorthosites, wehrlites, and/or clinopyroxenites. On the other hand, where the boundaries are sharp, the mineral assemblages change abruptly. There is no obvious deformation in the intrusions. Hence, the changes in mineral compositions are interpreted as the result of crystallization processes, such as fractionation in the magma chamber. Rock types with sharp boundaries show abrupt chemical changes, but the changes exhibit the same patterns of increasing and decreasing elements, especially of rare earth elements, as the gradational boundaries. Therefore, it is possible that all parts of the intrusions were formed from the same parental magma. Parts showing signs of nonequilibrium crystallization, such as cumulate features and sub-solidification, underwent fracturing and were interspersed throughout the magma chamber by late injection pulses or mechanical movements under mush conditions. The geological and age data show that the intrusions were formed from an Al-, Sr-, Fe-enriched and K-, Nb-depleted tholeiitic magma. The magma resulted from the partial melting of a metasomatized spinel demonstrated by negative Nb, P, Hf, and Ti, and positive Ba, Sr, and U anomalies typical of subduction-related magmas. 相似文献
196.
Gunnar Luderer Volker Krey Katherine Calvin James Merrick Silvana Mima Robert Pietzcker Jasper Van Vliet Kenichi Wada 《Climatic change》2014,123(3-4):427-441
This paper uses the EMF27 scenarios to explore the role of renewable energy (RE) in climate change mitigation. Currently RE supplies almost 20 % of global electricity demand. Almost all EMF27 mitigation scenarios show a strong increase in renewable power production, with a substantial ramp-up of wind and solar power deployment. In many scenarios, renewables are the most important long-term mitigation option for power supply. Wind energy is competitive even without climate policy, whereas the prospects of solar photovoltaics (PV) are highly contingent on the ambitiousness of climate policy. Bioenergy is an important and versatile energy carrier; however—with the exception of low temperature heat—there is less scope for renewables other than biomass for non-electric energy supply. Despite the important role of wind and solar power in climate change mitigation scenarios with full technology availability, limiting their deployment has a relatively small effect on mitigation costs, if nuclear and carbon capture and storage (CCS)—which can serve as substitutes in low-carbon power supply—are available. Limited bioenergy availability in combination with limited wind and solar power by contrast, results in a more substantial increase in mitigation costs. While a number of robust insights emerge, the results on renewable energy deployment levels vary considerably across the models. An in-depth analysis of a subset of EMF27 reveals substantial differences in modeling approaches and parameter assumptions. To a certain degree, differences in model results can be attributed to different assumptions about technology costs, resource potentials and systems integration. 相似文献
197.
Damage identification using inverse analysis in coupled thermo‐hydro‐mechanical problems applied to masonry dams
下载免费PDF全文
![点击此处可从《国际地质力学数值与分析法杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In this paper, we propose a method to detect the damage and estimate the degree of damage by means of a multifield‐based inverse analysis. The fields being considered are displacement, temperature, and water pressure. Furthermore, the uncertainties due to the size of the damage, the errors in the measurement data, and the errors in the model parameters are also investigated. The uncertainty due to the measurements is quantified by assuming different sources of noise in the measurements. The inverse problem is solved repeatedly by a sampling process. The uncertainties in the inverse solutions can be quantified by their probability distributions. This method can be applied to identify damages in masonry dams using coupled nonlinear thermo‐hydro‐mechanical problems. 相似文献
198.
Raphael Gromig Bernd Wagner Volker Wennrich Grigory Fedorov Larisa Savelieva Elodie Lebas Sebastian Krastel Dominik Brill Andrei Andreev Dmitry Subetto Martin Melles 《Boreas: An International Journal of Quaternary Research》2019,48(2):330-348
Lake Ladoga in northwestern Russia is Europe's largest lake. The postglacial history of the Ladoga basin is for the first time documented continuously with high temporal resolution in the upper 13.3 m of a sediment core (Co1309) from the northwestern part of the lake. We applied a multiproxy approach including radiographic imaging, (bio‐)geochemical and granulometric analyses. Age control was established combining radiocarbon dating with varve chronology, the latter anchored to a correlated radiocarbon age from a lake close by. The age‐depth model reveals the onset of glacial varve sedimentation at 13 910±140 cal. a BP, when Lake Ladoga was part of the Baltic Ice Lake. Linear extrapolation of published retreat rates of the Scandinavian Ice Sheet provides a formation age of the Luga moraine close to Lake Ladoga's southern shore of 14.5–15.9 cal. ka BP, older than previously assumed. Varve sedimentation covers the Bølling/Allerød interstadial, the Younger Dryas stadial and the Early Holocene. Varve‐thickness variations, conjoined with grain‐size and geochemical variations, inform about the relative position of the Scandinavian Ice Sheet and the climate during the deglaciation phase. The upper limit of the varved succession marks the change from glaciolacustrine to normal lacustrine sedimentation and post‐dates the drainage of the Baltic Ice Lake as well as the formation of the Salpausselkä II moraine north of Lake Ladoga, by c. 250 years. The Holocene sediment record is divided into three periods in the following order: (i) a lower transition zone between the Holocene boundary and c. 9.5 cal. ka BP, characterized by mostly massive sediments with low organic content, (ii) a phase with increased organic content from c. 9.5 to 4.5 cal. ka BP corresponding to the Holocene Thermal Maximum, and (iii) a phase with relatively stable sedimentation in a lacustrine environment from c. 4.5 cal. ka BP until present. 相似文献
199.
We show the numerical applicability of a multiresolution method based on harmonic splines on the 3-D ball which allows the regularized recovery of the harmonic part of the Earth's mass density distribution out of different types of gravity data, for example, different radial derivatives of the potential, at various positions which need not be located on a common sphere. This approximated harmonic density can be combined with its orthogonal anharmonic complement, for example, determined out of the splitting function of free oscillations, to an approximation of the whole mass density function. The applicability of the presented tool is demonstrated by several test calculations based on simulated gravity values derived from EGM96. The method yields a multiresolution in the sense that the localization of the constructed spline basis functions can be increased which yields in combination with more data a higher resolution of the resulting spline. Moreover, we show that a locally improved data situation allows a highly resolved recovery in this particular area in combination with a coarse approximation elsewhere which is an essential advantage of this method, for example, compared to polynomial approximation. 相似文献
200.