全文获取类型
收费全文 | 67篇 |
免费 | 2篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 1篇 |
地球物理 | 20篇 |
地质学 | 8篇 |
海洋学 | 12篇 |
天文学 | 29篇 |
自然地理 | 1篇 |
出版年
2020年 | 2篇 |
2018年 | 4篇 |
2017年 | 8篇 |
2015年 | 3篇 |
2013年 | 1篇 |
2012年 | 1篇 |
2011年 | 5篇 |
2010年 | 1篇 |
2009年 | 5篇 |
2008年 | 4篇 |
2007年 | 1篇 |
2005年 | 1篇 |
2004年 | 10篇 |
2003年 | 5篇 |
2002年 | 4篇 |
2001年 | 2篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1989年 | 2篇 |
1986年 | 2篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有71条查询结果,搜索用时 375 毫秒
41.
Levels and spatial distribution of polycyclic aromatic hydrocarbons (PAHs) in sediments from Lenga Estuary, central Chile 总被引:1,自引:0,他引:1
Pozo K Perra G Menchi V Urrutia R Parra O Rudolph A Focardi S 《Marine pollution bulletin》2011,62(7):1572-1576
The Lenga Estuary is a small brackish wetland located southwest of San Vicente Bay, Region VIII, Chile. Surface sediment from nine sites in the estuary were analysed for PAHs and compared to Sediment Quality Guidelines (SQG). Sediment samples were freeze dried and soxhlet extracted for 16 h using DCM. Identification and quantification was carried out by HPLC. Organic carbon was also determined. Results showed total PAH concentrations ranged from 290 to 6118 (2025 ± 1975) ng g−1 d.w. (2025 ± 1975). Results for organic carbon percentages ranged from 1% to 7%. Statistical analysis showed a significant positive correlation (Pearson test) between organic carbon percentage PAHs. Comparison of contaminant levels and international Sediment Quality Guidelines (SQG) (ERL and ER) suggested that sediment of the Lenga estuary did not show any ecotoxicologial risk for benthic organisms where high levels of PAHs were detected. Monitoring of this and other contaminants is recommended in Chile. 相似文献
42.
Gianluigi Bodo Claudio Zanni Giuseppe Murante Paola Rossi Silvano Massaglia Attilio Ferrari 《Astrophysics and Space Science》2004,293(1-2):247-254
We study, by numerical simulations, the propagation of an axisymmetric supersonic jet in an isothermal King atmosphere and we analyse the evolution of the resulting X-ray properties and their dependence on the jet physical parameters. We show the existence of two distinct regimes of interaction, with strong and weak shocks. In the first case shells of enhanced X-ray emission are to be expected, whereas in the second case we expect deficit of X-ray emission coincident with the cocoon. Analysing the results of our simulations we find that the jet kinetic power is the main parameter controlling the transition between the two regimes. We also discuss, in the same scheme, the ICM heating induced by the jet propagation, considering its effects on the observed relations between the cluster X-ray luminosity and temperature and between cluster entropy and temperature. 相似文献
43.
44.
Paola Rossi Gianluigi Bodo Silvano Massaglia Attilio Ferrari Andrea Mignone 《Astrophysics and Space Science》2004,293(1-2):149-155
Extragalactic radio sources are separated in two classes according to their specific luminosity: Fanaroff-Riley I and II. The origin of this dichotomy can be due either to intrinsec different properties of the AGN or to interaction of the jet with different enviroments. We assume that jets are always relativistic and supersonic close to their source, as recent observations suggest, and we explore the conditions in which the jets decelerate assuming FR I morphology. We have carried out high resolution 3D simulations for a set of parameters and in this paper we concentrate our discussion on two extreme cases. 相似文献
45.
Biochemical markers and ovarian histology were investigated in prespawning females of grass goby (Zosterisessor ophiocephalus) and grey mullet (Mugil cephalus) collected, respectively, in late spring and summer 2000 in four sites of a highly eutrophic brackish ecosystem of central Italy, the Orbetello Lagoon. Exposure to chlorinated and aromatic hydrocarbons was evaluated in fish livers by the somatic liver index (SLI) and by measuring 7-ethoxyresorufin-O-deethylase (EROD) and benzo(a)pyrene monooxygenase (BaPMO) activities. Acetylcholinesterase (AChE) activity was measured in brain and gills to evaluate exposure to organophosphates (OPs) and carbamates (CBs). The gonad somatic index (GSI) was used to confirm ovarian maturation and ovarian histology was investigated as a potential biomarker for environmental effects. Samples from the Western Basin, near a sewage treatment plant (STP) off the town of Orbetello, showed higher SLI values and higher EROD and BaPMO activities than those collected from the Ansedonia Canal (AC) in the Eastern Basin (p<0.05) and respect to those from reference sites: the Albegna River (AR) Delta for grass goby and the Nassa Canal (NC), connected with the sea, for grey mullet both located in the Western Basin as well. Low brain AChE activity was observed in both species from the reference sites (AR and NC) in association with the presence of anomalies in developing oocytes: unexpectedly small in grass goby and irregular disintegrated cytoplasm in grey mullet. The results indicate that the Western Basin is more polluted than the Eastern Basin particularly in the Orbetello where the sewage treatment plant may be a source of aromatic and chlorinated compounds while the Albegna River and the Nassa Canal may be sources of OPs and CBs. 相似文献
46.
Giovanardi Tommaso Girardi Vicente A. V. Correia Ciro T. Sinigoi Silvano Tassinari Colombo C. G. Mazzucchelli Maurizio 《Mineralogy and Petrology》2017,111(2):291-314
Mineralogy and Petrology - The Cana Brava complex is the northernmost of three layered complexes outcropping in the Goiás state (central Brasil). New field and geochemical evidences suggest... 相似文献
47.
The cardiac activity of three limpets (Patella rustica, P. caerulea and P. aspera), having a different vertical zonation on the Mediterranean rocky shores, was monitored using a non-invasive technique, during 6 h exposure to copper solutions (0.1 and 0.5 ppm), and after return to copper-free conditions. At 0.1 ppm no significant variation of heart rate was observed in the three species with respect to control conditions, while after 3 h at 0.5 ppm a consistent bradycardia was evident in P. caerulea and P. aspera, but not in P. rustica. After 6 h at 0.5 ppm most of the specimens of the three species were acardic but still reactive to mechanical stimulation. Tests on the resumption of cardiac activity after 6 h exposure to 0.5 ppm showed that even after a prolonged cessation of cardiac activity, limpets quickly resumed heartbeating once returned to clean seawater. However, recovery of heartbeating was faster in the mid- and high-shore species (P. caerulea and P. rustica, respectively) than in the lower-shore P. aspera. Moreover, the cardiac pattern upon recovery was definitely bradycardic in P. aspera, while the other two species showed a significant overshooting in heartbeating rate. Measurement of body burdens of copper showed that P. rustica and P. caerulea were faster in removing the excess of copper than the lower-shore P. aspera. In conclusion, this study showed that taxonomically close and syntopic species having a different zonal distribution exhibit different cardiac responses to waterborne copper and stresses the importance of comparative studies on physiological responses of organisms to metal pollution. 相似文献
48.
49.
Removal of Pb2 ,Cu~(2 ),Zn~(2 )and Cd~(2 )from aqueous solutions by sorption on a natural phosphate rock(FAP)was investigated.The effects of the contact time and initial metal concentration were examined in the batch method.The percentage sorption of heavy metals from solution ranges generally between 50% and 99%.The amount of sorbed metal ions follows the order Cu>Pb>Cd>Zn. Heavy metal immobilization was attributed to both surface complexation of metal ions on the surface of FAP grains and partial dissolution and precipitation of a heavy metal-containing phosphate.The very low desorption ratio of heavy metals further supports the effectiveness of FAP as an alternative and low-cost material to remove toxic Pb~(2 ),Cu~(2 ),Zn~(2 )and Cd~(2 )from polluted waters. 相似文献
50.
Rainfall as a trigger of shallow mass movements. A case study in the Dolomites, Italy 总被引:7,自引:0,他引:7
The article presents results of regional analysis on a historical basis correlating the occurrence of shallow mass movements
and disruptive events in time with precipitation trends. For the latter, different time-spans have been considered in an attempt
to find the most typical ones which might have triggered landslides. Research was carried out in the 850 km2 wide basin of the River Cordevole in the Dolomites (NE Italy). Data concerning slope movements and floods, which have affected
the area since the last century, were collected. Events which took place after 1920 have been correlated with the significant
pluviometric events recorded. In spite of the regionally high variability of both geological conditions and spatial distribution
of precipitation, three types of typical pluviometric trends related to an effective rainfall period of 15 days and to a peak
rainfall of 24–48 h preceding the onset of the movements were identified.
Received: 1 November 1996 · Accepted: 25 June 1997 相似文献