全文获取类型
收费全文 | 317篇 |
免费 | 6篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 3篇 |
大气科学 | 29篇 |
地球物理 | 26篇 |
地质学 | 196篇 |
海洋学 | 19篇 |
天文学 | 13篇 |
自然地理 | 41篇 |
出版年
2015年 | 2篇 |
2014年 | 4篇 |
2013年 | 28篇 |
2012年 | 8篇 |
2011年 | 9篇 |
2010年 | 6篇 |
2009年 | 8篇 |
2008年 | 9篇 |
2007年 | 5篇 |
2006年 | 7篇 |
2005年 | 17篇 |
2004年 | 2篇 |
2003年 | 5篇 |
2002年 | 8篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 7篇 |
1998年 | 7篇 |
1997年 | 21篇 |
1996年 | 15篇 |
1995年 | 5篇 |
1994年 | 11篇 |
1993年 | 11篇 |
1992年 | 11篇 |
1991年 | 17篇 |
1990年 | 8篇 |
1989年 | 4篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 4篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1968年 | 3篇 |
1967年 | 6篇 |
1966年 | 7篇 |
1963年 | 1篇 |
1962年 | 2篇 |
1933年 | 2篇 |
排序方式: 共有327条查询结果,搜索用时 24 毫秒
1.
2.
VOLKER GREWE MARTIN DAMERIS RALF HEIN ROBERT SAUSEN BENEDIKT STEIL 《Tellus. Series B, Chemical and physical meteorology》2001,53(2):103-121
The development of the future atmospheric chemical composition is investigated with respect to NO y and O3 by means of the off‐line coupled dynamic‐chemical general circulation model ECHAM3/CHEM. Two time slice experiments have been performed for the years 1992 and 2015, which include changes in sea surface temperatures, greenhouse gas concentrations, emissions of CFCs, NO x and other species, i.e., the 2015 simulation accounts for changes in chemically relevant emissions and for a climate change and its impact on air chemistry. The 2015 simulation clearly shows a global increase in ozone except for large areas of the lower stratosphere, where no significant changes or even decreases in the ozone concentration are found. For a better understanding of the importance of (A) emissions like NO x and CFCs, (B) future changes of air temperature and water vapour concentration, and (C) other dynamical parameters, like precipitation and changes in the circulation, diabatic circulation, stratosphere‐troposphere‐exchange, the simulation of the future atmosphere has been performed stepwise. This method requires a climate‐chemistry model without interactive coupling of chemical species. Model results show that the direct effect of emissions (A) plays a major rôle for the composition of the future atmosphere, but they also clearly show that climate change (B and C) has a significant impact and strongly reduces the NO y and ozone concentration in the lower stratosphere. 相似文献
3.
4.
Geochemistry and Intrusive History of the Ashland Pluton, Klamath Mountains, California and Oregon 总被引:3,自引:1,他引:2
GRIBBLE ROBERT F.; BARNES CALVIN G.; DONATO MARY M.; HOOVER JAMES D.; KISTLER RONALD W. 《Journal of Petrology》1990,31(4):883-923
The Ashland pluton is a calc-alkaline plutonic complex thatintruded the western Paleozoic and Triassic belt of the KlamathMountains in late Middle Jurassic time. The pluton comprisesa series of compositionally distinct magma pulses. The oldestrocks are hornblende gabbro and two-pyroxene quartz gabbro withinitial 87Sr/86Sr = 0{dot}7044, 18O = 8{dot}7%, and REE patternswith chondrite normalized La/Lu = 7. These units were followedby a suite of tonalitic rocks (LaN/LuN = 7) and then by a suiteof K2O- and P2O5 rocks of quartz monzodioritic affinity (LaN/LuN= 1321; LaN/SmN = 2{dot}43{dot}) The quartz monzodioriticrocks were then intruded by biotite granodiorite and granitewith lower REE abundances but more fractionated LREE(LaN/LuN= 1319; LaN/SmN = 4{dot}36 and they, in turn,were host to dikes and bosses of hornblende diorite. The latestintrusive activity consisted of aplitic and granitic dikes.Combined phase equilibria and mineral composition data, indicateemplacement conditions of approximately Ptotal = 2{dot}3kb,PH2O between 1{dot}5 and 2{dot}2 kb, and fO2 between the nickel-nickeloxide and hematite-magnetite buffers. Successive pulses of magma display increasing SiO2 togetherwith increasing 18O and decreasing initial 87Sr/86Sr. The isotopicdata are consistent with either (1) combined fractional crystallizationof andesitic magma and concurrent assimilation of crustal materialcharacterized by low Sr1 and high (18O or, more probably, (2)a series of partial melting events in which sources were successivelyless radiogenic but richer in 18O Each intrusive stage displaysevidence for some degree of crystal accumulation and/or fractionalcrystallization but neither process adequately accounts fortheir compositional differences. Consequently, each stage appearsto represent a distinct partial melting or assimilation event. The P2O5-rich nature of the quartz monzodiorite suite suggestsaccumulation of apatite. However, the suite contains abundantmafic microgranitoid enclaves and most apatite in the suiteis acicular. These observations suggest that magma mixing affectedthe compositional variation of the quartz monzodiorite suite.Mass balance calculations are consistent with a simple mixingprocess in which P2O5-rich alkalic basalt magma (representedby the mafic microgranitoid enclaves) was combined with a crystal-poorfelsic magma (represented by the tonalite suite), yielding aquartz monzodioritic magma that then underwent differentiationby crystal fractionation and accumulation. 相似文献
5.
Activity diagrams in the system KAlSi3O8-NaAlSi3O8-Al2SiO5-SiO2-H2O-HClhave been calculated in terms of aK+/aH+ and aN+/aH+ from existingexperimental data. They show the effect of temperature, pressure,and aH2O on the stability fields of the alkali feldspars, micas,and aluminium silicate. These activity diagrams are useful in revealing the bufferingcapacity of mineral assemblages and the chemical potential gradientsestablished by changes in T, P, aH2O, and mineral assemblage.An analysis of mineral paragenesis in terms of these diagramssuggests that mosaic equilibrium, allowing limited metasomatismand internal buffering of chemical potentials, best describemetamorphic systems. Thus the dehydration reaction: muscovite+quartz=K-feldspar+Al2SiO5+H2O which is most important in closed systems, probably fails todescribe in detail the mechanism of natural muscovite decomposition.Rather the decomposition of muscovite is more likely representedby ionic reactions. The replacement of muscovite by feldspar: muscovite+6 SiO2+2 K+=3 K-feldspar+2 H+ muscovite+6 SiO2+3 Na+=3 Albite+K++2 H+ is favored at high temperature and low pressure, and may accountfor the crystallization of some feldspars in metamorphic rocks.The reaction involving aluminium silicate replacement of muscovite: 2 muscovite+2 H+=3 Al2SiO5+3 SiO2+3 H2O+2 K+ is favored at high temperature and pressure and low aH2O, andcould contribute to the development of the aluminium silicates.It is concluded that both activity diagrams and AKNa projectionsshould be used together to more completely evaluate mineralparagenesis in terms of mosaic equilibria. 相似文献
6.
High-resolution seismic reflection profiles (3·5 kHz) have revealed the presence of extensive interstitial gas accumulation within the sedimentary sequences of Loch Tay, Scotland, as identified by acoustic turbidity masking the seismic stratigraphy. Within the central section of the loch, in the deepest water area directly above the zone of the seismically active Loch Tay Fault, focused flows of gas through the sediment pile to the loch bed via chimneys and pockmarks, together with gas seeps within the water column, have been identified. Microbiological observations indicate that the gas is biogenic CH4 , produced by both chemoautotrophic (which use CO2 as a source of carbon and H2 as a source of energy) and aceticlastic species (which use acetate as a source of carbon and energy) of methanogens in the fine-grained, organic rich deposits that have been focused into the zone of accumulation in the deep central part of the loch. The spatial distribution of the gas escape features suggests that earthquake movements along the Loch Tay Fault are responsible for facilitating focused gas escape in this part of the loch, by the creation of new pathways and conduits through the sediment pile, along which gas can migrate upwards and exit into the water column. Relict pockmarks and associated chimneys identified in the seismic records indicate that gas escape has been taking place since Pleistocene times though the precise timings cannot be ascertained. This is the first time that such features have been reported from a lake in the UK. 相似文献
7.
The influence of the organic aerosol component on CCN supersaturation spectra for different aerosol types 总被引:5,自引:0,他引:5
MIHAELA MIRCEA MARIA CRISTINA FACCHINI STEFANO DECESARI SANDRO FUZZI ROBERT J. CHARLSON 《Tellus. Series B, Chemical and physical meteorology》2002,54(1):74-81
Abstract This paper describes the effect of the presence of water-soluble organic compounds (WSOC) in aerosol particles on the aerosol critical supersaturation as defined by the Köhler theory and on cloud condensation nuclei (CCN) number concentration. Taking into account both the soluble mass increase and the surface tension depression due to WSOC, we calculated a substantial decrease of the aerosol critical supersaturation, which results in a large increase in CCN number concentration. CCN supersaturation spectra were computed for three different aerosol types: marine, rural and urban. The increase of CCN number concentration in the presence of WSOC (with respect to the case when only the inorganic aerosol compounds are considered) varies with aerosol type, with an increase up to 13% in the marine case, up to 97% in the rural case, and up to 110% in the urban case, for the supersaturation range typical of atmospheric conditions. 相似文献
8.
Petrogenesis of Early Neogene Magmatism in the Northern Puna; Implications for Magma Genesis and Crustal Processes in the Central Andean Plateau 总被引:4,自引:1,他引:4
CAFFE PABLO J.; TRUMBULL ROBERT B.; COIRA BEATRIZ L.; ROMER ROLF L. 《Journal of Petrology》2002,43(5):907-942
New compositional data and petrogenetic models are presentedfor pre-Upper Miocene volcanism in the northern Puna of Argentina(22°S24°S). Two phases of volcanism producedsmall dome complexes of mainly silicic andesite to low-SiO2rhyolite. The Upper OligoceneLower Miocene phase (UOLM,2017 Ma), produced two distinct groups of rocks. TheUOLM-1 group is metaluminous and mainly andesitic, with isotopiccompositions like those of the recent arc (87Sr/86SrT 相似文献
9.
KEVIN ROBERT GURNEY RACHEL M. LAW A. SCOTT DENNING PETER J. RAYNER DAVID BAKER PHILIPPE BOUSQUET LORI BRUHWILER YU-HAN CHEN PHILIPPE CIAIS SONGMIAO FAN INEZ Y. FUNG MANUEL GLOOR MARTIN HEIMANN KAZ HIGUCHI JASMIN JOHN EVA KOWALCZYK TAKASHI MAKI SHAMIL MAKSYUTOV PHILIPPE PEYLIN MICHAEL PRATHER BERNARD C. PAK JORGE SARMIENTO SHOICHI TAGUCHI TARO TAKAHASHI CHIU-WAI YUEN 《Tellus. Series B, Chemical and physical meteorology》2003,55(2):555-579
10.
Earthquake, flood, and drought data from different sources are combined in a single data set using the same data structure, projection, and scale. The intensity and frequency of each hazard is classified into severe, heavy, modest, and light, producing a classification with 64 combined states for the three kinds of hazard. These classes are then ranked according to severity. The three hazard coverages arc overlaid and the polygons that are produced are coded by the classification system. A map is produced that shows the distribution of these 64 classes in regions and their areas measured from the spatial topological data file in the GIS. Spatial analysis reveals the spatial association among the three hazards and between the three hazards and human factors. There is a brief discussion of the implications of the regionalized map for hazard monitoring. 相似文献