全文获取类型
收费全文 | 160篇 |
免费 | 14篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 3篇 |
大气科学 | 11篇 |
地球物理 | 45篇 |
地质学 | 82篇 |
海洋学 | 5篇 |
天文学 | 26篇 |
自然地理 | 4篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 3篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 12篇 |
2017年 | 11篇 |
2016年 | 19篇 |
2015年 | 5篇 |
2014年 | 13篇 |
2013年 | 7篇 |
2012年 | 5篇 |
2011年 | 12篇 |
2010年 | 5篇 |
2009年 | 9篇 |
2008年 | 2篇 |
2007年 | 9篇 |
2006年 | 7篇 |
2005年 | 4篇 |
2004年 | 3篇 |
2003年 | 1篇 |
2002年 | 1篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1971年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有176条查询结果,搜索用时 234 毫秒
91.
Glyn Williams-Jones Keith A. Horton Tamar Elias Harold Garbeil Peter J. Mouginis-Mark A. Jeff Sutton Andrew J. L. Harris 《Bulletin of Volcanology》2006,68(4):328-332
A fundamental problem with all ground-based remotely sensed measurements of volcanic gas flux is the difficulty in accurately
measuring the velocity of the gas plume. Since a representative wind speed and direction are used as proxies for the actual
plume velocity, there can be considerable uncertainty in reported gas flux values. Here we present a method that uses at least
two time-synchronized simultaneously recording UV spectrometers (FLYSPECs) placed a known distance apart. By analyzing the
time varying structure of SO2 concentration signals at each instrument, the plume velocity can accurately be determined. Experiments were conducted on
Kīlauea (USA) and Masaya (Nicaragua) volcanoes in March and August 2003 at plume velocities between 1 and 10 m s−1. Concurrent ground-based anemometer measurements differed from FLYSPEC-measured plume speeds by up to 320%. This multi-spectrometer
method allows for the accurate remote measurement of plume velocity and can therefore greatly improve the precision of volcanic
or industrial gas flux measurements.
Editorial responsibility: A. Woods 相似文献
92.
Ilias Bertahas Elias Dimitriou Ioannis Karaouzas Sofia Laschou Ierotheos Zacharias 《洁净——土壤、空气、水》2006,34(4):349-359
Trichonis Lake is the largest natural freshwater body in Greece with a surface area of 97 km2. It receives pollutants from numerous anthropogenic activities, especially from intensive agricultural practices, urban sewages, stock grazing land and small industries. In this study, hydrologic and chemical parameters are assessed during two periods (1990–1991) and (2001–2002) to evaluate the effects of the climatic changes on phosphorous trends and consequently on the trophic status of Trichonis Lake. Even though large quantities of fertilizers are applied in the lake's catchment, phosphorus loads are still in the permissible level as estimated according to Vollenweider's relationship based on total phosphorus concentration. Due to relatively higher rainfall precipitation during the last years, an increased amount of the phosphorus entering into the lake system is flushed out, thus keeping the trophic status of the lake in oligotrophic levels. In contrast, lower rainfall rates during the first period (1990–1991) have led to the decrease in phosphorus flush out and its detainment into the lake water and sediment resulting to mesotrophic conditions. As the trophic status of the lake is mainly hydrologically dependent and thus unpredictable, effective management plans targeting the elimination of nutrient pollution loadings are necessary. 相似文献
93.
Geotectonics - The Kighal and Bormolk porphyry copper deposits (PCDs) are known subeconomic deposits and are ~10 km south of Sungun, the world-class copper mine in NW Iran. The deposits are located... 相似文献
94.
Michael E. Böttcher Nadja Neubert Peter Escher Katja von Allmen Elias Samankassou Thomas F. Nägler 《Chemie der Erde / Geochemistry》2018,78(2):241-247
Carbonates formed from hyperalkaline aqueous solutions at the Earth?s surface are known to bear the most extreme disequilibrium isotope signatures reported so far in nature. We present here the results for stable carbon (C), oxygen (O), and barium (Ba) isotope fractionation during the precipitation of witherite (BaCO3) induced by the chemical absorption of atmospheric carbon dioxide (CO2) into an aqueous hyper-alkaline solution (at 4° and 21?°C; 1?atm total pressure). Independent from temperature, the barium carbonate formation was associated with a substantial enrichment of the lighter C and O isotopes in the solid compared to the atmosphere (C, O), close to previous results found in experiments and nature. A new approach is introduced to explain oxygen isotope fractionation upon hydroxylation of CO2. With Ba isotope enrichment factors between ?0.45 and ?0.53‰ (138/134ε) or ?0.34 and ?0.40‰ (137/134ε), respectively, the synthesized BaCO3 displays the highest kinetic enrichment of the light Ba isotope in the carbonate solid reported so far. 相似文献
95.
Chao Huang Hao Wang Jin‐Hui Yang Jahandar Ramezani Chuan Yang Shao‐Bing Zhang Yue‐Heng Yang Xiao‐Ping Xia Lian‐Jun Feng Jie Lin Tian‐Tian Wang Qian Ma Huai‐Yu He Lie‐Wen Xie Shi‐Tou Wu 《Geostandards and Geoanalytical Research》2020,44(1):103-123
A new natural zircon reference material SA01 is introduced for U‐Pb geochronology as well as O and Hf isotope geochemistry by microbeam techniques. The zircon megacryst is homogeneous with respect to U‐Pb, O and Hf isotopes based on a large number of measurements by laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) and secondary ion mass spectrometry (SIMS). Chemical abrasion isotope dilution thermal ionisation mass spectrometry (CA‐ID‐TIMS) U‐Pb isotopic analyses produced a mean 206Pb/238U age of 535.08 ± 0.32 Ma (2s, n = 10). Results of SIMS and LA‐ICP‐MS analyses on individual shards are consistent with the TIMS ages within uncertainty. The δ18O value determined by laser fluorination is 6.16 ± 0.26‰ (2s, n = 14), and the mean 176Hf/177Hf ratio determined by solution MC‐ICP‐MS is 0.282293 ± 0.000007 (2s, n = 30), which are in good agreement with the statistical mean of microbeam analyses. The megacryst is characterised by significant localised variations in Th/U ratio (0.328–4.269) and Li isotopic ratio (?5.5 to +7.9‰); the latter makes it unsuitable as a lithium isotope reference material. 相似文献
96.
The seismic response of two fundamental mechanical configurations of earthquake engineering, the elastic–plastic system and the pounding oscillator, is revisited with the aid of dimensional analysis. Starting from the previous work of the authors which focused on pulse-type excitations, the paper offers an alternative, yet physically motivated, way to present the response of yielding and pounding structures under excitations with arbitrary time history. It is shown, that when the appropriate time and length scales are adopted, dimensional analysis can be implemented and remarkable order emerges in the response. Regardless of the acceleration level and frequency content of the excitation, all response spectra become self-similar and when expressed in dimensionless terms, resulting from dimensional analysis, follow a single master curve. The study proposes such scales together with the associated selection criteria among the available in literature strong ground motion parameters and shows that the proposed approach reduces drastically the scatter in the response. 相似文献
97.
An excavation primarily intended to investigate the Bronze Age deposits at Hautrive‐Champréveyres, Neuchâtel, Switzerland, encountered beneath the Bronze Age levels a sequence of Late‐glacial sediments that were deposited between about 13000 yr BP and 11800 yr BP. Within these deposits Upper Palaeolithic hearths, bones and flint implements were found in a context that left no doubt that they accumulated on the actual living floors. Two separate cultures were involved; an earlier Magdalenian one overlain by a rather later Azilian assemblage. Coleoptera from the associated organic silts and sands provide detailed ecological and climatic information about the time when these people lived in the area. Radiocarbon dates indicate that the Magdalenians lived in the area at about 13000 yr BP. The Coleoptera show that the mean July temperature at this time was about 9°C and mean temperature of the coldest month was about −25°C. The landscape was bare of trees with an open patchy vegetation. Shortly after the area was abandoned by the Magdalenian hunters, the climate became suddenly warmer and mean July temperatures rose abruptly to at least 16°C and winter temperatures rose to levels not much different from those of the present day. There is evidence that at this time, intense slope instability and mud flows may have rendered the locality unsuitable for human occupation. About seven centuries after the episode of sudden climatic warming, namely at about 12300 yr BP, palaeolithic Azilian hunters occupied the area at a time when the climate was thoroughly temperate and the landscape was clothed in birch and willow woodland. This was gradually replaced by pine forest at the top of the sequence and Late‐glacial deposition ceased by about 11800 yr BP. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
98.
Karin Şeşetyan Laurentiu Danciu Mine B. Demircioğlu Tümsa Domenico Giardini Mustafa Erdik Sinan Akkar Levent Gülen Mehdi Zare Shota Adamia Anooshiravan Ansari Avetis Arakelyan Ayşegül Askan Mher Avanesyan Hektor Babayan Tamaz Chelidze Raffi Durgaryan Ata Elias Hossein Hamzehloo Khaled Hessami Doğan Kalafat Özkan Kale Arkady Karakhanyan Muhammad Asif Khan Tahir Mammadli Mahmood Al-Qaryouti Mohammad Sayab Nino Tsereteli Murat Utkucu Otar Varazanashvili Muhammad Waseem Hilal Yalçın Mustafa Tolga Yılmaz 《Bulletin of Earthquake Engineering》2018,16(8):3535-3566
The Earthquake Model of Middle East (EMME) Project aimed to develop regional scale seismic hazard and risk models uniformly throughout a region extending from the Eastern Mediterranean in the west to the Himalayas in the east and from the Gulf of Oman in the south to the Greater Caucasus in the North; a region which has been continuously devastated by large earthquakes throughout the history. The 2014 Seismic Hazard Model of Middle East (EMME-SHM14) was developed with the contribution of several institutions from ten countries. The present paper summarizes the efforts towards building a homogeneous seismic hazard model of the region and highlights some of the main results of this model. An important aim of the project was to transparently communicate the data and methods used and to obtain reproducible results. By doing so, the use of the model and results will be accessible by a wide community, further support the mitigation of seismic risks in the region and facilitate future improvements to the seismic hazard model. To this end all data, results and methods used are made available through the web-portal of the European Facilities for Earthquake Hazard and Risk (www.efehr.org). 相似文献
99.
The trends in annual maximum rainfall (AMR) intensity data in New South Wales, Australia, were examined. Data from 60 stations were used covering three study periods, 1955–2010, 1965–2010 and 1978–2010. Mann-Kendall (MK) and Spearman’s rho (SR) tests were applied to assess trends at local stations. Pre-whitening (PW), trend-free pre-whitening (TFPW) and the variance correction (VC) tests were used to assess the effects of serial correlation on trend results. For regional trend analysis, the regional MK test was employed. The impacts of climatic variability modes on the observed trends in AMR intensity and seasonal maximum rainfall data were investigated. It was found that positive trends were more frequent than the negative ones. The PW, TFPW and VC tests resulted in a slight reduction in the count of stations exhibiting significant positive trends. The number of stations exhibiting significant trends decreased when the impact of climate variability modes was considered. 相似文献
100.
River water quality models usually apply the Fischer equation to determine the longitudinal dispersion coefficient (Dx) in solving the advection–dispersion equation (ADE). Recently, more accurate formulas have been introduced to determine Dx in rivers, which could strongly affect the accuracy of the ADE results. A numerical modelling-based approach is presented to evaluate the performance of various Dx formulas using the ADE. This approach consists of a finite difference approximation of the ADE, a MATLAB code and a MS Excel interface; it was tested against the analytical ADE solution and demonstrated using eight well-known Dx formulas and tracer study data for the Chattahoochee River (USA), the Severn (UK) and the Athabasca (Canada). The results show that Dx has an important effect on tracer concentrations simulated with the ADE. Comparison between the simulated and measured concentrations confirms the appropriate performance of Zeng and Huai’s formula for Dx estimation. Use of the newly proposed equations for Dx estimation could enhance the accuracy of solving the ADE. 相似文献