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91.
G. M. Marion A. E. Murray B. Wagner C. H. Fritsen F. Kenig P. T. Doran 《Aquatic Geochemistry》2013,19(2):135-145
Perennial ice covers on many Antarctic lakes have resulted in high lake inorganic carbon contents. The objective of this paper was to evaluate and compare the brine and CO2 chemistries of Lake Vida (Victoria Valley) and West Lake Bonney (Taylor Valley), two lakes of the McMurdo Dry Valleys (East Antarctica), and their potential consequences during global warming. An existing geochemical model (FREZCHEM-15) was used to convert measured molarity into molality needed for the FREZCHEM model, and this model added a new algorithm that converts measured DIC into carbonate alkalinity needed for the FREZCHEM model. While quite extensive geochemical information exists for ice-covered Taylor Valley lakes, such as West Lake Bonney, only limited information exists for the recently sampled brine of >25 m ice-thick Lake Vida. Lake Vida brine had a model-calculated pCO2 = 0.60 bars at the field pH (6.20); West Lake Bonney had a model-calculated pCO2 = 5.23 bars at the field pH (5.46). Despite the high degree of atmospheric CO2 supersaturation in West Lake Bonney, it remains significantly undersaturated with the gas hydrate, CO2·6H2O, unless these gas hydrates are deep in the sediment layer or are metastable having formed under colder temperatures or greater pressures. Because of lower temperatures, Lake Vida could start forming CO2·6H2O at lower pCO2 values than West Lake Bonney; but both lakes are significantly undersaturated with the gas hydrate, CO2·6H2O. For both lakes, simulation of global warming from current subzero temperatures (?13.4 °C in Lake Vida and ?4.7 °C in West Lake Bonney) to 10 °C has shown that a major loss of solution-phase carbon as CO2 gases and carbonate minerals occurred when the temperatures rose above 0 °C and perennial ice covers would disappear. How important these Antarctic CO2 sources will be for future global warming remains to be seen. But a recent paper has shown that methane increased in atmospheric concentration due to deglaciation about 10,000 years ago. So, CO2 release from ice lakes might contribute to atmospheric gases in the future. 相似文献
92.
B. Wagner R. Sulpizio G. Zanchetta S. Wulf M. Wessels G. Daut N. Nowaczyk 《Journal of Volcanology and Geothermal Research》2008
A 1075 cm long core (Lz1120) was recovered in the south-eastern part of the Lake Ohrid (Republics of Macedonia and Albania) and sampled for identification of tephra layers. Magnetic susceptibility investigations show rather high magnetic values throughout the core, with peaks unrelated to the occurrence of tephra layers but instead to the relative abundance of detrital magnetic minerals in the sediment. Naked-eye inspection of the core allowed us to identify of two tephra layers, at 896–897 cm and 1070–1075 cm. Laboratory inspection of the grain-size fraction > 125 μm allowed for the identification of a third cryptotephra at 310–315 cm. Major element analyses on glass shards of the tephra layers at 896–897 cm and 1070–1075 cm show a trachytic composition, and indicate a correlation with the regionally dispersed Y-3 and Y-5 tephra layers, dated at ca 30 and 39 cal ka BP. The cryptotephra at 310–315 cm has a mugearitic–benmoreitic composition, and was correlated with the FL eruption of Mt. Etna, dated at 3370 ± 70 cal yr BP. These ages are in agreement with five 14C AMS measurements carried out on plant remains and macrofossils from the lake sediments at different depths along the core. 相似文献
93.
Wagner José Barreto Dilson Norio Ishikawa Ieda Spacino Scarminio João de Souza Costa Paulo dos Santos Nora Miriam de Fatima Soares Romilaine Mansano Nicolau Adriana Celeste Esteves Gonçalves Sonia Regina Giancoli Barreto 《洁净——土壤、空气、水》2008,36(4):353-359
The conservation of large water resources is essential for the preservation of human life. The quantification and, more importantly, the speciation of chemical substances that indicate the presence of anthropogenic contamination in water resources are of great importance. This paper presents the results of analysis for the determination of organic, inorganic and total phosphorus, pseudo‐sulfur, and iron and manganese, in five fractions, in water sediments collected from the Capivara Hydroelectric Power Plant, Brazil. A study on the seasonal variation of these parameters was conducted, with data having been collected in the winter and in the summer, at two sites along the dam, 5 km apart, close to the city of Primeiro de Maio. Phosphorous was found in sediments and adjacent soil in the organic form (OP), and was used as an indicator of anthropogenic influence on the reservoir banks. Speciation of potentially toxic Mn showed that it is present in the exchangeable fraction of the 0–5 cm depth layer (sediment/water interface), making its transfer to the water column possible. Results from this study showed that domestic and industrial effluent treatment measures are needed for the preservation of the quality of aquatic environments. 相似文献
94.
Valentin N. Mitkin 《Geostandards and Geoanalytical Research》2000,24(2):157-170
A novel method is described for the rapid dissolution of various geological, geochemical and related reference samples for the determination of Au and the platinum-group elements. The decomposition procedure is based on reaction with the fluoroxidants, liquid bromine trifluoride or molten potassium tetrafluorobromate. Results by this novel procedure are compared with data obtained by traditional methods of sample decomposition, including fire assay, autoclave techniques and an aqua regia leach. The oxidative fluorination procedure with the subsequent conversion of fluorocomplexes into the chloride form was found to be an effective and rapid method for the quantification of all the precious metals in a range of sample types. 相似文献
95.
Valentin V. Kalenichenko 《Astrophysics and Space Science》2000,274(3):489-502
The electronic version of an extensive catalogue of the results of the fireball physics inverse problem solution for the precise
observational data of the Prairie Network Fireballs (DTHM-values) obtained by local-ballistic method of a variably-sliding
path-segment contains a set of the physical parameters for the 480 fireball images of the 248 cosmic body entries into the
Earth's atmosphere (PNVK-values). The parameters are: the fireball velocity with the corresponding values of the mass to cross-section
area ratio for the fireball-generating body a teach measured point of the fireball path, the ablation factor and the ratio
of the luminous fireball energy to the drag work for the body in the Earth's atmosphere using a factor inversely proportional
to the density of the body. The catalogue of all PNVK-values, about 3.1 Mbytes in ASCII is accessible from ftp://ftp2.mao.kiev.ua/pub/astro/pnvk,
files pnvk.cat and pnvks.cat
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
96.
97.
Daqing Yang Barry E. Goodison John R. Metcalfe Valentin S. Golubev Esko Elomaa Thilo Gunther Roy Bates Timothy Pangburn Clayton L. Hanson Douglas Emerson Voilete Copaciu Janja Milkovic 《水文研究》1995,9(8):877-895
The Tretyakov non-recording precipitation gauge has been used historically as the official precipitation measurement instrument in the Russian (formerly the USSR) climatic and hydrological station network and in a number of other European countries. From 1986 to 1993, the accuracy and performance of this gauge were evaluated during the WMO Solid Precipitation Measurement Intercomparison at 11 stations in Canada, the USA, Russia, Germany, Finland, Romania and Croatia. The double fence intercomparison reference (DFIR) was the reference standard used at all the Intercomparison stations in the Intercomparison. The Intercomparison data collected at the different sites are compatible with respect to the catch ratio (measured/DFIR) for the same gauge, when compared using mean wind speed at the height of the gauge orifice during the observation period. The Intercomparison data for the Tretyakov gauge were compiled from measurements made at these WMO intercomparison sites. These data represent a variety of climates, terrains and exposures. The effects of environmental factors, such as wind speed, wind direction, type of precipitation and temperature, on gauge catch ratios were investigated. Wind speed was found to be the most important factor determining the gauge catch and air temperature had a secondary effect when precipitation was classified into snow, mixed and rain. The results of the analysis of gauge catch ratio versus wind speed and temperature on a daily time step are presented for various types of precipitation. Independent checks of the correction equations against the DFIR have been conducted at those Intercomparison stations and a good agreement (difference less than 10%) has been obtained. The use of such adjustment procedures should significantly improve the accuracy and homogeneity of gauge-measured precipitation data over large regions of the former USSR and central Europe. 相似文献
98.
It is found, by means of particle simulations, that the field-aligned scale length of the V-potential along auroral-field lines depends on the convergence of the magnetic-field lines. In a uniform magnetic field, the potential drop is localized in a double layer with a field-aligned scale length of the order of the Debye length. In a converging magnetic field, the potential drop is shown to be extended with a field-aligned scale length much greater than the Debye length. The converging magnetic field appears to contribute to the retention of trapped electrons confined between the magnetic mirror and the electrostatic potential-barrier. When a background plasma is included in the simulation, the potential structure is shown to detach from the ionospheric boundary. 相似文献
99.
Markus Wagner 《GeoJournal》2005,62(3-4):91-113
In semi-arid orographic left tributaries of the Kali Gandaki at the northern and western flank of the Nilgiri Himal, glacio-geomorphological
and pedological investigations were carried out on prehistoric moraines. Geomorphological relief analysis was derived from
other literature and the own fieldwork of the author. The resulting glacial chronology was used as benchmark to explore the
limits of different pedological dating methods regarding the degree of soil development. These methods are based on iron fractionation,
total element contents and particle size distribution. In general the different glacial stages are mirrored correctly in the
relative graduation of soil development. The ratio of well crystallised pedogenic iron-oxides to the total iron content and
the ratio fine clay to total clay are most suitable, because they are almost independent from existing changes in the lithological
composition. The total element based weathering indices are less suitable, because they react highly sensitive to the geology
dependent shift to higher carbonate contents. Most of the grain size based weathering indices are inapplicable because of
the typically high textural variability within till deposits. 相似文献
100.
Wagner Monika Trutschnig Wolfgang Bathke Arne C. Ruprecht Ulrike 《Theoretical and Applied Climatology》2018,131(3-4):1397-1415
Theoretical and Applied Climatology - For testing the hypothesis that macroclimatological factors determine the occurrence, biodiversity, and species specificity of both symbiotic partners of... 相似文献