全文获取类型
收费全文 | 304篇 |
免费 | 3篇 |
专业分类
测绘学 | 1篇 |
大气科学 | 26篇 |
地球物理 | 94篇 |
地质学 | 142篇 |
海洋学 | 5篇 |
天文学 | 35篇 |
自然地理 | 4篇 |
出版年
2016年 | 4篇 |
2015年 | 7篇 |
2013年 | 6篇 |
2009年 | 6篇 |
2007年 | 7篇 |
2006年 | 6篇 |
2005年 | 5篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2002年 | 9篇 |
2000年 | 4篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1994年 | 5篇 |
1985年 | 4篇 |
1982年 | 3篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1976年 | 7篇 |
1975年 | 6篇 |
1974年 | 4篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1967年 | 3篇 |
1964年 | 3篇 |
1963年 | 3篇 |
1961年 | 3篇 |
1959年 | 3篇 |
1958年 | 4篇 |
1956年 | 4篇 |
1955年 | 3篇 |
1954年 | 8篇 |
1952年 | 5篇 |
1951年 | 7篇 |
1950年 | 6篇 |
1949年 | 10篇 |
1948年 | 8篇 |
1938年 | 3篇 |
1930年 | 4篇 |
1927年 | 3篇 |
1926年 | 4篇 |
1925年 | 3篇 |
1924年 | 3篇 |
1922年 | 3篇 |
1920年 | 4篇 |
1918年 | 3篇 |
1913年 | 3篇 |
1912年 | 4篇 |
1911年 | 3篇 |
排序方式: 共有307条查询结果,搜索用时 15 毫秒
51.
Ohne Zusammenfassung 相似文献
52.
53.
Otto Ludwig 《International Journal of Earth Sciences》1929,20(1):36-65
Ohne Zusammenfassung 相似文献
54.
Ohne ZusammenfassungMit 1 Textabbildungen 相似文献
55.
Brandon G. Watts Marvin E. Bennett Otto C. Kopp Gerald L. Mattingly 《Geoarchaeology》2004,19(1):47-69
Seventeen basalt grindstone fragments from central Jordan's Karak Plateau were studied. Most of these artifacts are vesicular or amygdaloidal with calcite as the dominant mineral filling the voids. The major minerals are olivine (with iddingsite rims), plagioclase, clinopyroxene, magnetite, and apatite. Glass is present in some samples. One basalt fragment is quite different in appearance and composition and may have come from flows closer to the Dead Sea. Grindstone fragment compositions plot in the tephrite‐basanite and basalt fields. A plot of the concentrations of niobium, zirconium, and yttrium reveal that the sample compositions plot in the “within‐plate alkali basalt” and “within‐plate tholeiite” fields. The acquisition of basalts for preparing such implements appears to have been random. Some may have been introduced through trade and migration. Archaeological and environmental studies on the Karak Plateau are urgently needed because Jordan's population growth and economic development are destroying many sites and their environmental contexts. © 2004 Wiley Periodicals, Inc. 相似文献
56.
Contributions of groundwater conditions to soil and water salinization 总被引:23,自引:2,他引:21
Salinization is the process whereby the concentration of dissolved salts in water and soil is increased due to natural or
human-induced processes. Water is lost through one or any combination of four main mechanisms: evaporation, evapotranspiration,
hydrolysis, and leakage between aquifers. Salinity increases from catchment divides to the valley floors and in the direction
of groundwater flow. Salinization is explained by two main chemical models developed by the authors: weathering and deposition.
These models are in agreement with the weathering and depositional geological processes that have formed soils and overburden
in the catchments. Five soil-change processes in arid and semi-arid climates are associated with waterlogging and water. In
all represented cases, groundwater is the main geological agent for transmitting, accumulating, and discharging salt. At a
small catchment scale in South and Western Australia, water is lost through evapotranspiration and hydrolysis. Saline groundwater
flows along the beds of the streams and is accumulated in paleochannels, which act as a salt repository, and finally discharges
in lakes, where most of the saline groundwater is concentrated. In the hummocky terrains of the Northern Great Plains Region,
Canada and USA, the localized recharge and discharge scenarios cause salinization to occur mainly in depressions, in conjunction
with the formation of saline soils and seepages. On a regional scale within closed basins, this process can create playas
or saline lakes. In the continental aquifers of the rift basins of Sudan, salinity increases along the groundwater flow path
and forms a saline zone at the distal end. The saline zone in each rift forms a closed ridge, which coincides with the closed
trough of the groundwater-level map. The saline body or bodies were formed by evaporation coupled with alkaline-earth carbonate
precipitation and dissolution of capillary salts.
Received, May 1998 · Revised, July 1998 · Accepted, September 1998 相似文献
57.
Interaction between crustal-derived felsic and mantle-derived mafic magmas in the Oberkirch Pluton (European Variscides, Schwarzwald, Germany) 总被引:5,自引:1,他引:4
R. Altherr F. Henjes-Kunst C. Langer J. Otto 《Contributions to Mineralogy and Petrology》1999,137(4):304-322
The composite Oberkirch pluton consists of three compositionally different units of peraluminous biotite granite. The northern
unit is relatively mafic (SiO2∼64%) and lacks cordierite. The more felsic central and southern units (SiO2=67.8 to 70.4%) can only be distinguished from each other by the occurrence of cordierite in the former. Mafic microgranular
enclaves of variable composition, texture and size occur in each of these units and are concentrated in their central domains.
Most abundant are large (dm to m) hornblende-bearing enclaves with dioritic to tonalitic compositions (SiO2=50.8 to 56.3 wt%; Mg#=63 to 41) and fine grained doleritic textures that suggest chilling against the host granite magma.
Some of these enclaves are mantled by hybrid zones. Less common are microtonalitic enclaves containing biotite as the only
primary mafic phase (SiO2=53.7 to 64.4%) and small hybrid tonalitic to granodioritic enclaves and schlieren. Synplutonic dioritic dikes (up to 6 m
thick) with hybrid transition zones to the host granite occur in the southern unit of the pluton. In chemical variation diagrams,
samples from unmodified hornblende-bearing mafic enclaves and dikes form continuous trends that are compatible with an origin
by fractionation of olivine, clinopyroxene, hornblende and plagioclase. Chemical and initial isotopic signatures (e.g. high
Mg#, low Na2O, ɛNd=−1.2 to −5.1, 87Sr/86Sr=0.7055 to 0.7080, δ18O=8.0 to 8.8‰) exclude an origin by partial melting from a mafic meta-igneous source but favour derivation from a heterogeneous
enriched lithospheric mantle. Samples from the granitic host rocks do not follow the chemical variation trends defined by
the diorites but display large scatter. In addition, their initial isotopic characteristics (ɛNd=−4.5 to −6.8, 87Sr/86Sr=0.7071 to 0.7115, δ18O=9.9 to 11.9‰) show little overlap with those of the diorites. Most probably, the granitic magmas were derived from metapelitic
sources characterized by variable amounts of garnet and plagioclase. This is suggested by relatively high molar ratios of
Al2O3/(MgO+FeOtot) and K2O/Na2O, in combination with low ratios of CaO/(MgO+FeOtot), variable values of Sr/Nd, Eu/Eu*[=Eucn/(Smcn × Gdcn)0.5] and (Tb/Yb)cn (cn=chondrite-normalized) as well as variable abundances of Sc and Y. Whole-rock initial isotopic signatures of mafic microtonalitic
enclaves (ɛNd=−4.6 to −5.2; 87Sr/86Sr=0.7060 to 0.7073; δ18O ∼8.1‰) are similar to those of the low ɛNd diorites. Plagioclase concentrates from a granite sample and a mafic microtonalitic enclave are characterized by initial
87Sr/86Sr ratios that are significantly higher than those of their bulk rock systems suggesting incorporation of high 87Sr/86Sr crustal material into the magmas. Field relationships and petrographic evidence suggest that the Oberkirch pluton originated
by at least three pulses of granitic magma containing mafic magma globules. In-situ hybridization between the different magmas
was limited. Late injection of dioritic magma into the almost solidified granitic southern unit resulted in the formation
of more or less continuous synplutonic dikes surrounded by relatively thin hybrid zones.
Received: 30 April 1999 / Accepted: 6 August 1999 相似文献
58.
The Relation Between Humidity and Liquid Water Content in Fog: An Experimental Approach 总被引:1,自引:0,他引:1
Stefan Georg Gonser Otto Klemm Frank Griessbaum Shih-Chieh Chang Hou-Sen Chu Yue-Joe Hsia 《Pure and Applied Geophysics》2012,169(5-6):821-833
Microphysical measurements of orographic fog were performed above a montane cloud forest in northeastern Taiwan (Chilan mountain site). The measured parameters include droplet size distribution (DSD), absolute humidity (AH), relative humidity (RH), air temperature, wind speed and direction, visibility, and solar short wave radiation. The scope of this work was to study the short term variations of DSD, temperature, and RH, with a temporal resolution of 3?Hz. The results show that orographic fog is randomly composed of various air volumes that are intrinsically rather homogeneous, but exhibit clear differences between each other with respect to their size, RH, LWC, and DSD. Three general types of air volumes have been identified via the recorded DSD. A statistical analysis of the characteristics of these volumes yielded large variabilities in persistence, RH, and LWC. Further, the data revealed an inverse relation between RH and LWC. In principle, this finding can be explained by the condensational growth theory for droplets containing soluble or insoluble material. Droplets with greater diameters can exist at lower ambient RH than smaller ones. However, condensational growth alone is not capable to explain the large observed differences in DSD and RH because the respective growth speeds are too slow to explain the observed phenomena. Other mechanisms play key roles as well. Possible processes leading to the large observed differences in RH and DSD include turbulence induced collision and coalescence, and heterogeneous mixing. More analyses including fog droplet chemistry and dynamic microphysical modeling are required to further study these processes. To our knowledge, this is the first experimental field observation of the anti-correlation between RH and LWC in fog. 相似文献
59.
Wang XS Neuman SP Strack OD Verruijt A Jamali M Seymour B Bear J Cheng AH 《Ground water》2011,49(2):133-42; discussion 142-3
60.
Jan‐Christoph Otto Lothar Schrott Michel Jaboyedoff Richard Dikau 《地球表面变化过程与地形》2009,34(13):1726-1742
The determination of sediment storage is a critical parameter in sediment budget analyses. But, in many sediment budget studies the quantification of magnitude and time‐scale of sediment storage is still the weakest part and often relies on crude estimations only, especially in large drainage basins (>100 km2). We present a new approach to storage quantification in a meso‐scale alpine catchment of the Swiss Alps (Turtmann Valley, 110 km2). The quantification of depositional volumes was performed by combining geophysical surveys and geographic information system (GIS) modelling techniques. Mean thickness values of each landform type calculated from these data was used to estimate the sediment volume in the hanging valleys and the trough slopes. Sediment volume of the remaining subsystems was determined by modelling an assumed parabolic bedrock surface using digital elevation model (DEM) data. A total sediment volume of 781·3×106–1005·7×106 m3 is deposited in the Turtmann Valley. Over 60% of this volume is stored in the 13 hanging valleys. Moraine landforms contain over 60% of the deposits in the hanging valleys followed by sediment stored on slopes (20%) and rock glaciers (15%). For the first time, a detailed quantification of different storage types was achieved in a catchment of this size. Sediment volumes have been used to calculate mean denudation rates for the different processes ranging from 0·1 to 2·6 mm/a based on a time span of 10 ka. As the quantification approach includes a number of assumptions and various sources of error the values given represent the order of magnitude of sediment storage that has to be expected in a catchment of this size. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献