全文获取类型
收费全文 | 1145篇 |
免费 | 187篇 |
国内免费 | 454篇 |
专业分类
大气科学 | 23篇 |
地球物理 | 113篇 |
地质学 | 1520篇 |
海洋学 | 9篇 |
天文学 | 70篇 |
综合类 | 46篇 |
自然地理 | 5篇 |
出版年
2024年 | 8篇 |
2023年 | 10篇 |
2022年 | 26篇 |
2021年 | 28篇 |
2020年 | 23篇 |
2019年 | 38篇 |
2018年 | 35篇 |
2017年 | 34篇 |
2016年 | 47篇 |
2015年 | 48篇 |
2014年 | 55篇 |
2013年 | 54篇 |
2012年 | 58篇 |
2011年 | 49篇 |
2010年 | 44篇 |
2009年 | 75篇 |
2008年 | 47篇 |
2007年 | 69篇 |
2006年 | 76篇 |
2005年 | 96篇 |
2004年 | 68篇 |
2003年 | 74篇 |
2002年 | 54篇 |
2001年 | 67篇 |
2000年 | 71篇 |
1999年 | 62篇 |
1998年 | 75篇 |
1997年 | 55篇 |
1996年 | 56篇 |
1995年 | 43篇 |
1994年 | 55篇 |
1993年 | 43篇 |
1992年 | 29篇 |
1991年 | 27篇 |
1990年 | 22篇 |
1989年 | 14篇 |
1988年 | 17篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1978年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有1786条查询结果,搜索用时 191 毫秒
181.
182.
S. W. FARYAD 《Journal of Metamorphic Geology》1995,13(6):701-714
Abstract Blueschists occurring as layers in calcite marbles of the Meliata unit occur along the so-called Roznava tectonic line situated in the southern part of the Gemericum, Slovakia. Mineral assemblages and compositions from seven blueschists localities and one occurrence of amphibolite facies rocks overprinted by blueschist metamorphism were investigated. The most common minerals in the blueschists are blue amphibole, epidote and albite. Some Fe2+ - and Al-rich rocks also contain garnet and chloritoid, respectively. Na-pyroxene with a maximum 50% jadeite component was also found. The blue amphiboles correspond mostly to crossite and also to glaucophane and ferroglaucophane in some samples. Almandine- and spessartine-rich garnet has very low MgO content (<3 wt%). The Si content in phengite ranges between 3.3 and 3.5 pfu calculated on the basis of 11 oxygens. The zoning patterns of blue amphibole, garnet and chloritoid suggest their formation during a prograde stage of metamorphism. The P-T conditions of metamorphism are estimated to be about 380–460° C and 10–13 kbar. Pressures of 7.5–8.5 kbar and temperatures of 350–370° C were obtained for some actinolite- and aegirine-rich rocks. Apart from chlorite, other mafic minerals formed during retrograde metamorphism are biotite and occasionally also actinolite. 相似文献
183.
J. R. De Laeter B. J. Allen G. C. Lowenthal J. W. Boldeman 《Journal of Astrophysics and Astronomy》1988,9(1):7-15
In an endeavour to resolve reported discrepancies in the value of the branching ratio of176Lu at astrophysical energies, a new determineation of the175Lu (nγ)176mLu capture cross section has been measured as 958 ± 58 mb. This gives a value of the branching ratio of 0.21 ±0.05. This result
indicates that some reequilibration of the ground and isomeric states of176Lu occurs in stellar environments undergoing s-process nucleosynthesis, and confirms that176Lu is not a reliable cosmochronometer. However the very existence of176Lu in the solar system implies that the ground state of176Lu was not completely depopulated, and provides the possibility of using this nuclide as a sensitive thermometer for stellar
processes. 相似文献
184.
Abstract. Plagioclase porphyroblasts from silvergrey schists belonging to the Nevado Filabride Complex in the Sierra Alhamilla (Betic Zone, SE Spain) are interpreted as having been formed preand synkinematically with respect to the second phase of deformation. Different types of inclusion patterns represent 'snap-shots'(high growth-rate/strain-rate ratio features) of the formation of a diffentiated crenulation cleavage during this second phase of deformation, by the processes of kinking, crenulation and associated differentiation.
Regional considerations indicate an Alpine age for this tectono-metamorphic event, which can be explained by the'hot emplacement'of the higher Nevado Filabride units. The observed structural evolution is not consistent with a pre-Alpine polyphase deformation history. 相似文献
Regional considerations indicate an Alpine age for this tectono-metamorphic event, which can be explained by the'hot emplacement'of the higher Nevado Filabride units. The observed structural evolution is not consistent with a pre-Alpine polyphase deformation history. 相似文献
185.
A. J. ZINGG 《Journal of Metamorphic Geology》1995,13(3):431-443
Abstract End-member, continuous and degenerate reactions are derived for the multisystem with the six components Na2O, CaO, (Mg/Fe)O, Al2O3, SiO2, H2O among the phases plagioclasess, garnetss, amphiboless, cpx, opx, olivine, spinel, quartz and an aqueous fluid. The chemography of this system is degenerate due to the co-linearity 2Opx = Ol + Qtz. This co-linearity has its implications both on reaction space and phase equilibria. From a total of 28 reaction systems, reaction space is derived for nine subsystems (phases in parentheses are absent): Case A1: (Cpx,Ol) (Cpx,Opx) and (Cpx,Qtz), Case A2: (Spl,Ol) (Spl,Opx) and (Spl,Qtz), Case B: (Ol,Opx) (Ol,Qtz) and (Opx,Qtz). In the absence of either cpx or spl (case A), three reactions form an invariant point, either [Cpx] or [Spl], where the co-linear phases olivine, opx and quartz coexist on the transformation line 2Opx = Ol + Qtz. Changing mineral compositions force invariant points to move along the line with the different reaction curves changing their relative position according to Schreinemakers’rules. Zero contours, i.e. the location where (a) phase(s) disappear(s) in reaction space correspond to singular points in phase diagrams. Two types are distinguished; singular points of indispensable and of substitutable phases. In the first case the phase disappears from the entire bundle while in the second it disappears from a single reaction. In the specific case where the substitutable phases are also the co-linear ones, two of the three co-linear phases disappear simultaneously. Two of the three reaction curves coincide. In the system including Cpx and Spl (Case B) three reactions, (Ol,Opx) (Ol,Qtz) and (Opx,Qtz), oppose three invariant points, [Ol], [Opx] and [Qtz]. Invariant points no longer move along the line 2Opx = Ol + Qtz. The coincidence of the zero contours of all three co-linear phases in reaction space-the result of the chemographic degeneracy-causes the respective singular points to coincide in the phase diagrams. This is the location where curves must be rearranged in a bundle to conform Schreinemakers’rules. The reaction Grs1Prp2= 2 Ol + An is fourth order degenerate and part of all nine subsystems (cases A and B). It can be used to relate the different phase diagrams to one another. 相似文献
186.
B. LEVI L. AGUIRRE J. O. NYSTRÖM H. PADILLA M. VERGARA 《Journal of Metamorphic Geology》1989,7(5):487-495
ABSTRACT All the Mesozoic and Cenozoic volcanic rocks of the Central Andes (from southern Ecuador to central Chile), except Recent ones, have been affected by episodes of regional metamorphism, without change in texture and structure. The metamorphism, which ranges from low zeolite to greenschist facies, can be classified as burial metamorphism because there is an overall increase in metamorphic grade with stratigraphic depth in the individual volcanic sequences separated by regional unconformities. Some sequences display metamorphic patterns transitional to ocean-floor and to geothermal field types, reflecting variations along and across the Andes in tectonic setting and thermal gradients. Volcanism was closely followed by metamorphism during each cycle characterizing the geological history of the Central Andes. The episodic nature of the metamorphism has led to breaks in metamorphic grade at regional unconformities and repetition of facies series, where strata of higher grade may even overlie those of lower grade. The existence of permeability-controlled distribution patterns of secondary minerals within individual flows shows that gradients of chemical activity, rate of reaction and Pfluid were acting, in addition to temperature and P,tot overall gradients, during the regional metamorphism. The alteration is accompanied by chemical changes and disturbances of the K-Ar and Rb-Sr isotope systems. Similarities between Mesozoic facies series in the western and eastern flanks of the Andes are consistent with a mechanism of ensialic spreading-subsidence. 相似文献
187.
Solubility of Anhydrite, CaSO4, in NaCl-H2O Solutions at High Pressures and Temperatures: Applications to Fluid-Rock Interaction 总被引:1,自引:0,他引:1
Anhydrite solubility in H2ONaCl solutions was measuredat 614 kbar, 600800°C and NaCl mole fractions(XNaCl) of 00·3 in pistoncylinder apparatus.Solubilities were determined by weight changes of natural anhydritein perforated Pt envelopes confined with fluid in larger Ptcapsules. In initially pure H2O at 10 kbar and 800°C, CaSO4concentration is low (0·03 molal), though much largerthan at the same temperature and 1 kbar. Hematite-buffered experimentsshowed slightly lower solubilities than unbuffered runs. CaSO4solubility increases enormously with NaCl activity: at 800°Cand 10 kbar and XNaCl of 0·3, CaSO4 molality is 200 timeshigher than with pure H2O. Whereas CaSO4 solubility in pureH2O decreases with rising T at low T and P, the high-P resultsshow that anhydrite solubility increases with T at constantP at all XNaCl investigated. The effects of salinity and temperatureare so great at 10 kbar that critical mixing between sulfate-richhydrosaline melts and aqueous salt solutions is probable at900°C at XNaCl 0·3. Recent experimental evidencethat volatile-laden magmas crystallizing in the deep crust mayevolve concentrated salt solutions could, in light of the presentwork, have important implications regarding such diverse processesas Mount Pinatubo-type S-rich volcanism, high-f O2 regionalmetamorphism, and emplacement of porphyry CuMo ore bodies,where anhydritehematite alteration and fluid inclusionsreveal the action of very oxidized saline solutions rich insulfur. KEY WORDS: anhydrite; sulfur; solubility; metamorphic brines; granulites 相似文献
188.
PESQUERA A.; TORRES-RUIZ J.; GIL-CRESPO P. P.; JIANG S.-Y. 《Journal of Petrology》2005,46(5):1013-1044
Tourmaline in the Martinamor antiform occurs in tourmalinites(rocks with >1520% tourmaline by volume), clasticmetasedimentary rocks of the Upper Proterozoic Monterrubio formation,quartz veins, pre-Variscan orthogneisses and Variscan graniticrocks. Petrographic observations, back-scattered electron (BSE)images, and microprobe data document a multistaged developmentof tourmaline. Overall, variations in the Mg/(Mg + Fe) ratiosdecrease from tourmalinites (0·360·75),through veins (0·380·66) to granitic rocks(0·230·46), whereas Al increases in thesame order from 5·846·65 to 6·226·88apfu. The incorporation of Al into tourmaline is consistentwith combinations of xAl(NaR)1 and AlO(R(OH))1exchange vectors, where x represents X-site vacancy and R is(Mg + Fe2+ + Mn). Variations in x/(x + Na) ratios are similarin all the types of tourmaline occurrences, from 0·10to 0·53, with low Ca-contents (mostly <0·10apfu). Based on field and textural criteria, two groups of tourmaline-richrocks are distinguished: (1) pre-Variscan tourmalinites (probablyCadomian), affected by both deformation and regional metamorphismduring the Variscan orogeny; (2) tourmalinites related to thesynkinematic granitic complex of Martinamor. Textural and geochemicaldata are consistent with a psammopelitic parentage for the protolithof the tourmalinites. Boron isotope analyses of tourmaline havea total range of 11B values from 15·6 to 6·8;the lowest corresponding to granitic tourmalines (15·6to 11·7) and the highest to veins (1·9to 6·8). Tourmalines from tourmalinites have intermediate11B values of 8·0 to +2·0. The observedvariations in 11B support an important crustal recycling ofboron in the Martinamor area, in which pre-Variscan tourmaliniteswere remobilized by a combination of mechanical and chemicalprocesses during Variscan deformation, metamorphism and anatexis,leading to the formation of multiple tourmaline-bearing veinsand a new stage of boron metasomatism. KEY WORDS: tourmalinites; metamorphic and granitic rocks; mineral chemistry; whole-rock chemistry; boron isotopes 相似文献
189.
FERRY JOHN M.; RUMBLE DOUGLAS III; WING BOSWELL A.; PENNISTON-DORLAND SARAH C. 《Journal of Petrology》2005,46(8):1725-1746
Progress () of the infiltration-driven reaction, 4olivine +5CO2 + H2O = talc + 5magnesite, that occurred during Barrovianregional metamorphism, varies at the cm-scale by a factor of3·5 within an 3 m3 volume of rock. Mineral and stableisotope compositions record that XCO2, 18Ofluid, and 13Cfluidwere uniform within error of measurement in the same rock volume.The conventional interpretation of small-scale variations in in terms of channelized fluid flow cannot explain the uniformityin fluid composition. Small-scale variations in resulted insteadbecause (a) reactant olivine was a solid solution, (b) initiallythere were small-scale variations in the amount and compositionof olivine, and (c) fluid composition was completely homogenizedover the same scale by diffusiondispersion during infiltrationand subsequent reaction. Assuming isochemical reaction, spatialvariations in image variations in the (Mg + Fe)/Si of the parentrock rather than the geometry of metamorphic fluid flow. Ifinfiltration-driven reactions involve minerals fixed in composition,on the other hand, spatial variations in do directly imagefluid flow paths. The geometry of fluid flow can never be determinedfrom geochemical tracers over a distance smaller than the oneover which fluid composition is completely homogenized by diffusiondispersion. KEY WORDS: Alpine Barrovian metamorphism; diffusion; metamorphic fluid composition; metamorphic fluid flow; reaction progress 相似文献
190.
In the Chilean Coastal Cordillera, two units, the Western andEastern Series, constitute coeval parts of a Late Palaeozoicpaired metamorphic belt dominated by siliciclastic metasediments.The Western Series also contains rocks from the upper oceaniccrust and represents an accretionary prism. Omnipresent high-pressureconditions are reflected by NaCa-amphibole and phengitein greenschists. Peak PT conditions of 7·09·3kbar, 380420°C point to a metamorphic gradient of1116°C/km. Three unique occurrences of blueschistyield deviating conditions of 9·510·7 kbar,350385°C and are interpreted as relics from the lowermostpart of the basal accretion zone preserving the original gradientof 911°C/km along the subducting slab. Pervasiveductile deformation related to basal accretion occurred nearpeak PT conditions. Deformation and PT evolution of the metapsammopeliticrocks is similar to that of the metabasites. However, a raregarnet mica-schist yields peak PT conditions of 9·614·7kbar, 390440°C reflecting a retrograde stage aftercooling from a high-temperature garnet-forming stage. It isconsidered to be an exhumed relic from the earliest siliciclasticrocks subducted below a still hot mantle wedge. A retrogradeoverprint of all rock types occurred at 300380°C.Continuous reactions caused crystal growth and recrystallizationwith abundant free water mostly under strain-free conditions.They record a pressure release of 34 kbar without erasingpeak metamorphic mineral compositions. The Eastern Series lacksmetabasite intercalations and represents a less deformed retro-wedgearea. In the study area it was entirely overprinted at a uniformdepth at 3 ± 0·5 kbar with temperatures progressivelyrising from 400°C to 720°C towards the coeval Late Palaeozoicmagmatic arc batholith. The interrelated pattern of PT datapermits a conceptual reconstruction of the fossil convergentmargin suggesting a flat subduction angle of 25° with continuousbasal accretion at a depth of 2540 km and a short mainintrusion pulse in the magmatic arc. The latter was accompaniedby the formation of a thermal dome in the retro-wedge area,which remained stable relative to the vertically growing accretionaryprism characterized by cyclic mass flow. KEY WORDS: paired metamorphic belt; greenschist; blueschist; central Chile; thermobarometry 相似文献