全文获取类型
收费全文 | 365篇 |
免费 | 12篇 |
国内免费 | 7篇 |
专业分类
测绘学 | 22篇 |
大气科学 | 37篇 |
地球物理 | 81篇 |
地质学 | 180篇 |
海洋学 | 18篇 |
天文学 | 33篇 |
自然地理 | 13篇 |
出版年
2018年 | 4篇 |
2015年 | 7篇 |
2014年 | 9篇 |
2013年 | 18篇 |
2012年 | 6篇 |
2011年 | 9篇 |
2010年 | 11篇 |
2009年 | 14篇 |
2008年 | 18篇 |
2007年 | 17篇 |
2006年 | 14篇 |
2005年 | 6篇 |
2004年 | 10篇 |
2003年 | 9篇 |
2002年 | 13篇 |
2001年 | 6篇 |
2000年 | 7篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1994年 | 10篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 8篇 |
1989年 | 7篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1977年 | 4篇 |
1976年 | 9篇 |
1975年 | 5篇 |
1974年 | 3篇 |
1973年 | 7篇 |
1971年 | 5篇 |
1970年 | 6篇 |
1968年 | 5篇 |
1966年 | 3篇 |
1963年 | 3篇 |
1962年 | 7篇 |
1961年 | 3篇 |
1960年 | 4篇 |
1954年 | 3篇 |
排序方式: 共有384条查询结果,搜索用时 609 毫秒
91.
92.
Thirty-one rock samples from a Western Canada Basin well have been analysed for aromatics, using glass capillary gas chromatography with simultaneous flame ionization and sulfur-selective flame photometric detection. A uniform aromatic distribution pattern with a marked predominance of di- and tricyclic aromatic hydrocarbons was observed throughout a depth interval of 3000 meters comprising Cretaceous and Jurassic sediments. The very high relative abundance of sulfur aromatics at two narrow intervals in the Triassic and Mississippian is attributed to a major change in facies. Gradual changes with increasing depth have been observed for a series of compound ratios, which had been calculated from the isomers of methyl- and dimethylphenanthrene, and their parent compounds. These changes reflect the increasing thermal maturation of the sedimentary organic matter. A Methylphenanthrene Index (MPI) has been introduced, which exhibited a very good correlation with vitrinite reflectance data. The MPI is the first maturity parameter which is based on a series of aromatic hydrocarbons. This hydrocarbon internal maturity parameter permits the recognition and definition of maturity levels in extracts which can be compared to the maturity (e.g. vitrinite reflectance) of source rocks. 相似文献
93.
94.
Inhalt Optische und röntgenographische Untersuchungen zeigen, daß die Quarzstengel im Schriftgranit von Zwiesel über mehrere Zentimeter in ihrem optischen Drehvermögen und in der Orientierung konstant bleiben.Mit 1 Textabbildung 相似文献
95.
Prof. Dr. Helmut G. F. Winkler 《Contributions to Mineralogy and Petrology》1954,4(1-2):233-242
Ohne ZusammenfassungHerrn Professor Dr.Carl W. Correns zum 60. Geburtstag gewidmet. 相似文献
96.
Dr. Achim Hirschberg Helmut G. F. Winkler 《Contributions to Mineralogy and Petrology》1968,18(1):17-42
The stability relations between cordierite and almandite in rocks, having a composition of CaO poor argillaceous rocks, were experimentally investigated. The starting material consisted of a mixture of chlorite, muscovite, and quartz. Systems with widely varying Fe2+/Fe2++Mg ratios were investigated by using two different chlorites, thuringite or ripidolite, in the starting mixture. Cordierite is formed according to the following reaction: $${\text{Chlorite + muscovite + quartz}} \rightleftharpoons {\text{cordierite + biotite + Al}}_{\text{2}} {\text{SiO}}_{\text{5}} + {\text{H}}_{\text{2}} {\text{O}}$$ . At low pressures this reaction characterizes the facies boundary between the albite-epidotehornfels facies and the hornblende-hornfels facies, at medium pressures the beginning of the cordierite-amphibolite facies. Experiments were carried out reversibly and gave the following equilibrium data: 505±10°C at 500 bars H2O pressure, 513±10°C at 1000 bars H2O pressure, 527±10°C at 2000 bars H2O pressure, and 557±10°C at 4000 bars H2O pressure. These equilibrium data are valid for the Fe-rich starting material, using thuringite as the chlorite, as well as for the Mg-rich starting mixture with ripidolite. At 6000 bars the equilibrium temperature for the Mg-rich mixture is 587±10°C. In the Fe-rich mixture almandite was formed instead of cordierite at 6000 bars. The following reaction was observed: $${\text{Thuringite + muscovite + quartz}} \rightleftharpoons {\text{almandite + biotite + Al}}_{\text{2}} {\text{SiO}}_{\text{5}} {\text{ + H}}_{\text{2}} {\text{O}}$$ . Experiments with the Fe-rich mixture, containing Fe2+/Fe2++Mg in the ratio 8∶10, yielded three stability fields in a P,T-diagram (Fig.1):
- Above 600°C/5.25 kb and 700°C/6.5 kb almandite+biotite+Al2SiO5 coexist stably, cordierite being unstable.
- The field, in which almandite, biotite and Al2SiO5 are stable together with cordierite, is restricted by two curves, passing through the following points:
- 625°C/5.5 kb and 700°C/6.5 kb,
- 625°C/5.5 kb and 700°C/4.0 kb.
- At conditions below curves 1 and 2b, cordierite, biotite, and Al2SiO5 are formed, but no garnet.
97.
Reactions which occur at the lower boundary of the hornblende-hornfels facies and in the so-called pyroxene-hornfels facies were experimentally investigated for an ultrabasic rock at 500, 1000 and 2000 bars H2O pressure.The starting material used was a mixture of natural chlorite, talc, tremolite and quartz such that its composition, except for surplus quartz, corresponded to that of an ultrabasic rock. The atomic ratio Fe2++Fe2+/Mg+Fe3++Fe3+ in the system was 0.16.The lower boundary of the hornblende-hornfels facies was defined by the formation of the orthorhombic amphibole anthophyllite and hornblende according to the following idealized reaction: chlorite+talc+tremolite+quartz hornblende+anthophyllite+H2O In effect, this reaction consists of the two bivariant reactions: chlorite+tremolite+quartz hornblende+anthophyllite+H2O talc+chlorite anthophyllite+quartz+H2OThe equilibrium temperatures obtained for the two reactions in the given system are practically the same and are as follows: 535±10°C at 500 bars H2O pressure 550±20°C at 1000 bars H2O pressure 560±10°C at 2000 bars H2O pressure 580±10°C at 4000 bars H2O pressureAt 2000 bars and higher temperatures within the hornblende-hornfels facies, anorthite is formed in addition to hornblende and anthophyllite, probably according to the following reaction: hornblende1+quartz hornblende2+anthophyllite+anorthite+H2O; because of the formation of anorthite it is to be expected that the hornblende in this case is poorer in aluminium than the hornblende at 500 and 1000 bars. Winkler (1967) suggests renaming the pyroxene-hornfels facies as K-feldspar-cordierite-hornfels facies which, in turn, is subdivided into a lower-temperature orthoamphibole subfacies without orthopyroxene and a higher-temperature orthopyroxene subfacies without orthoamphibole. The orthopyroxene subfacies itself may in its lower temperature part still carry hornblende which finally disappears in the higher temperature part.The appearance of orthopyroxene characterizes the transition from the orthoamphibole to the orthopyroxene subfacies of the K-feldspar-cordierite hornfels facies. The following reaction takes place at pressures lower than 2000 bars: hornblende1+anthophyllite hornblende2+enstatite+anorthite+H2OSince at 2000 bars an Al-poor hornblende already exists in the hornblende-hornfels facies, it is very likely that here only anthophyllite breaks down to give enstatite+quartz+H2O.The equilibrium temperatures for these reactions which give rise to enstatite are: 650±10°C at 250 bars H2O pressure 690±10°C at 500 bars H2O pressure 715±10°C at 1000 bars H2O pressure 770±10°C at 2000 bars H2O pressureOnly after an increase in temperature to about 710°C at 500 bars and about 770°C at 1000 bars does hornblende in the system investigated here break down completely according to the reaction: hornblende = enstatite+anorthite+diopside+H2OExcept at very small H2O-pressures (see Fig. 3), there exists, therefore, a region within the orthopyroxene subfacies where hornblende, enstatite and anorthite coexist. As a result we have, as mentioned above, a lower-temperature and a higher-temperature part of the orthopyroxene subfacies, and it is only in the latter part that the parageneses correspond to the pyroxene-hornfels facies as stated by Eskola (1939).Summing up, the starting material consisting of chlorite, talc, tremolite plus quartz remains unchanged in the albite-epidote-hornfels facies; this gives rise in the hornblende-hornfels facies to the paragenesis hornblende+anthophyllite, or — at higher pressures — to hornblende+anthophyllite+anorthite. For the particular composition of the starting material, however, no reactions take place at the transition of the hornblende-hornfels facies to the orthoamphibole subfacies of the K-feldspar-cordierite-hornfels facies as this transition is typified by the breakdown of muscovite in the presence of quartz. However, at the end of the orthoamphibole subfacies the breakdown of anthophyllite, by which orthopyroxene is formed, heralds the onset of the orthopyroxene subfacies. In this subfacies — at
greater than about 300 bars — hornblende is still present and coexists with enstatite and anorthite, but with rising temperature hornblende breaks down to give way to the paragenesis enstatite+anorthite+diopside. The experimentally determined parageneses confirm known petrographic occurrences.
Für die Förderung dieser Arbeit danken wir der Deutschen Forschungsgemeinschaft vielmals. Der Dank von Choudhuri gilt dem Akademischen Auslandsamt der Universität Göttingen für ein Stipendium, das ihm den Abschluß seiner Studien an der Universität Göttingen ermöglichte. 相似文献
Für die Förderung dieser Arbeit danken wir der Deutschen Forschungsgemeinschaft vielmals. Der Dank von Choudhuri gilt dem Akademischen Auslandsamt der Universität Göttingen für ein Stipendium, das ihm den Abschluß seiner Studien an der Universität Göttingen ermöglichte. 相似文献
98.
99.
Helmut Höller 《Contributions to Mineralogy and Petrology》1970,27(1):80-94
Zusammenfassung Im Temperaturbereich zwischen 100–180° C wurde experimentell die Umwandlung einiger natürlicher Silikate und silikatischer Gesteine in Analcim untersucht. Der Analcim bildete sich im alkalischen Milieu nach Abbau der einzelnen Ausgangssubstanzen direkt und ohne das Auftreten irgendeiner Zwischenphase. Die Entstehung des Analcims zeigte sich dabei abhängig von der Art und der Konzentration der einwirkenden Lösungen, von der Temperatur und von den Ausgangssubstanzen. Bei geringeren Konzentrationen der Lösungen war die Reaktion bedeutend langsamer als bei größeren. Der Analcim bildete sich nur in einem bestimmten Konzentrationsbereich der alkalischen Lösungen, wobei dieser für die einzelnen Substanzen unterschiedlich war. In Abhängigkeit von der Ausgangssubstanz entstanden bei geringeren Alkalikonzentrationen an Stelle des Analcims Zeolithe und bei größeren Alkallkonzentrationen SiO2-Mineralien.
Herrn Prof. Dr. H. Heritsch danke ich für sein dauerndes Interesse an dieser Arbeit, für Ratschläge und kritische Bemerkungen sowie für die Zurverfügungstellung der Mittel des Institutes für Mineralogie und Petrographie der Universität Graz.
Herrn Prof. Dr. C. W. Correns möchte ich auch an dieser Stelle für die Möglichkeit, die experimentelle Technik in Göttingen kennenzulernen, meinen Dank sagen. 相似文献
Investigations on the formation of analcite from natural silicates
The transformation of some natural silicates and silicatic rocks into analcite was experimentally investigated over a temperature range of 100° C to 180° C. Analcite was directly formed in alkaline surroundings after reduction of the various starting substances without any intermediate phases. The formation of analcite depended on the kind and concentration of the reacting solutions, on the temperature and on the starting substance. At lower concentrations of the solutions the reaction was considerably slower than at higher ones. Analcite was formed only within a certain concentration range of the alkaline solutions, this range being different for the different substances. Depending on the starting substance, zeolites were formed at lower alkali concentrations. At higher alkali concentrations SiO2 minerals were formed.
Herrn Prof. Dr. H. Heritsch danke ich für sein dauerndes Interesse an dieser Arbeit, für Ratschläge und kritische Bemerkungen sowie für die Zurverfügungstellung der Mittel des Institutes für Mineralogie und Petrographie der Universität Graz.
Herrn Prof. Dr. C. W. Correns möchte ich auch an dieser Stelle für die Möglichkeit, die experimentelle Technik in Göttingen kennenzulernen, meinen Dank sagen. 相似文献
100.
Helmut Schäfer Wolfgang Friedrich Müller Ulrich Hornemann 《Physics and Chemistry of Minerals》1983,9(6):248-252
Shock recovery experiments on synthetic MgAl2O4-spinel samples in the pressure range 25.5 to 50.5 GPa have been performed in order to examine the effects of shock waves on this material. The shocked samples were subsequently studied in the transmission electron microscope. All samples showed shock-induced dislocations with the Burgers vector 1/2 〈110〉 and twin lamellae of the twin-law {111}. In addition, samples, which had experienced the higher pressures, showed lamellar areas of a crystalline phase that we have not yet been able fully to characterize. It is probably not ε-MgAl2O4. 相似文献