全文获取类型
收费全文 | 25052篇 |
免费 | 222篇 |
国内免费 | 920篇 |
专业分类
测绘学 | 1419篇 |
大气科学 | 2028篇 |
地球物理 | 4652篇 |
地质学 | 11843篇 |
海洋学 | 1093篇 |
天文学 | 1710篇 |
综合类 | 2163篇 |
自然地理 | 1286篇 |
出版年
2022年 | 4篇 |
2021年 | 16篇 |
2020年 | 13篇 |
2019年 | 11篇 |
2018年 | 4776篇 |
2017年 | 4051篇 |
2016年 | 2609篇 |
2015年 | 264篇 |
2014年 | 104篇 |
2013年 | 86篇 |
2012年 | 1024篇 |
2011年 | 2767篇 |
2010年 | 2050篇 |
2009年 | 2353篇 |
2008年 | 1919篇 |
2007年 | 2388篇 |
2006年 | 79篇 |
2005年 | 228篇 |
2004年 | 416篇 |
2003年 | 429篇 |
2002年 | 265篇 |
2001年 | 59篇 |
2000年 | 61篇 |
1999年 | 21篇 |
1998年 | 28篇 |
1997年 | 5篇 |
1996年 | 6篇 |
1995年 | 5篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 9篇 |
1987年 | 4篇 |
1986年 | 8篇 |
1985年 | 3篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 25篇 |
1980年 | 22篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1976年 | 8篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1970年 | 3篇 |
1969年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Anne Marie de Grosbois 《Environmental Geology》2008,54(5):1121-1126
62.
Controlling of landsides safely and economically is a great challenge to mine operators because landslides are major geological
problems especially in open-pit mines. In this paper, a case history at Panluo open-pit mine is presented in detail to share
the experiences and lessons with mine operators. Panluo open-pit mine is located in the southwestern Fujian province of China.
It is the largest open-pit iron mine in the Fujian province and was planned in 1965 and is in full operation from 1978. In
July 1990, an earthquake of magnitude 5.3 in Taiwan Strait and big rainstorms impacted the mine slope, causing tension cracks
and rather large-scale failures, and forming a U-shaped landslide. Total potential volume was estimated to be up to 1.0 × 106 m3. This directly threatened the mine production. In order to protect the mine production and the dwellers’ safety around, a
dynamic comprehensive method was implemented including geotechnical investigations, in-situ testing and monitoring, stability
analysis, and many mitigation and preventive measures. These measures slowed down the development and further occurrence of
the landslide. The results showed that the landslides were still active, it was slowed with the control measures and moved
rapidly with rainfall and mining down. However, no catastrophic accidents occurred and the pit mining was continued till it
was closed at the elevation of 887 m in 2000. As a successful case of landslide control at an open-pit mine for 10 years,
this paper reports the controlling measures in details. These experiences of landslide control may be beneficial to other
similar mines for landslide control. 相似文献
63.
The largest karst cave discovered in a tunnel during motorway construction in Slovenia’s Classical Karst (Kras) 总被引:1,自引:0,他引:1
Karst researchers of the Karst Research Institute ZRC SAZU are regularly consulted during the planning of Slovenia’s motorways
and invited to observe and monitor construction in the karst areas. More than 350 caves have been discovered in the course
of building 60 km of new motorways over the past decade. Access to the most important caves is preserved by concrete tubes
closed with metal covers at the roadside. The largest cave system in a tunnel, named LC-S647, is almost entirely preserved.
The protection of this cave will serve as a good example for the preservation of natural heritage in the future. Construction
work for the motorway uncovered a high degree of karstification. In particular, the discovery of this cave in the Kastelec
tunnel LC-S647 showed the existence of a major cave system in the geological and speleological past. A number of unconnected
passages have also been found. Caves discovered during highway construction have brought new knowledge about the cavernosity
and the geological history of this part of the karst. 相似文献
64.
Soil contamination from urban and industrial activity: example of the mining district of Linares (southern Spain) 总被引:1,自引:0,他引:1
J. Martínez J. F. Llamas E. de Miguel J. Rey M. C. Hidalgo 《Environmental Geology》2008,54(4):669-677
The Linares region (southern Spain) has been subjected to two important sources of pollution: the intensive mining works and
the urban-industrial activity. To obtain a geochemical characterisation of the soil, 31 trace elements were analysed and 669
soil samples were collected. By means of clustering analysis, we identified groups of elements and grid squares in which relations
could be established concerning soil lithology, urban and industrial activities and the degree of pollution impact; in addition,
we were able to characterise the geochemical background of the study area. The multivariate study led us to identify four
factors. Particularly important was factor 2, which represented the elements associated with mineral paragenesis (Cu, Pb,
As, Co, Mn, Zn, Sn, Ba). This factor also contains elements related with an urban-industrial activity, such as Pb, Cu, Zn,
As and Ba. Furthermore, we identified factor 4, associating Ni, V and Cr, and which is related to the use of fuels. 相似文献
65.
Cengiz Kuzu 《Environmental Geology》2008,54(5):1075-1080
Ground vibrations generated by commercial explosives in tunnel construction may cause structural damage in urban areas. Therefore,
suppressing the vibration effects and mitigating the possible hazard after blasting is important. We present a new method
of controlled blasting that is environmentally friendly, and easy to utilize for tunnel construction. Small charges in this
method are detonated sequentially to produce minimum side effects. The efficiency of the charges may be increased based on
the previously monitored shots. This method is utilized in a tunnel construction in Istanbul with five experimental shots.
In these experiments, the duration and also the quantity of explosives were carefully controlled. We were able to obtain better
results with short durations (480 ms) instead of long durations (9,000 ms) although the vibration levels defined as peak particle
velocity (PPV) became bigger while the quantity of the explosive charge increased from 3.088 to 9.264 kg. 相似文献
66.
A detailed characterization of the site is crucial to designing an efficient method of managing the risks associated with
tailings from abandoned mines. Therefore, samples collected from various depths within tailings in Guryong mine, Korea, were
analyzed for their chemical, physical and mineralogical characteristics. All samples of the Guryong tailings had acid-generating
potential. However, in the oxidation zone, the net acid generation (NAG) was low (30 kg H2SO4 t−1) although the acid neutralization potential (ANP) was less than zero. The ANP values in the unoxidation zone were higher
(> −56.0 kg CaCO3 t−1) than in the other zones. As a result, the amount of alkali ions that are needed to neutralize the acid needs to be considered.
In this experiment G3, G4 and G6 drill cores containing fine tailings particles near the unoxidation zone were observed to
contain calcite (CaCO3) with acid-neutralizing capacity. A low pH (2−4) in the oxidation zone of the tailings changed to a neutral pH in the unoxidation
zone of the tailings. These results suggest that the acid-neutralizing capacity of the tailings was controlled by particle
and mineral composition of tailings. 相似文献
67.
Trace elements contamination of agricultural soils affected by sulphide exploitation (Iberian Pyrite Belt,Sw Spain) 总被引:1,自引:0,他引:1
Agricultural soils of the Riotinto mining area (Iberian Pyrite Belt) have been studied to assess the degree of pollution by
trace elements as a consequence of the extraction and treatment of sulphides. Fifteen soil samples were collected and analysed
by ICP-OES and INAA for 51 elements. Chemical analyses showed an As–Cu–Pb–Zn association related with the mineralisation of
the Iberian Pyrite Belt. Concentrations were 19–994 mg kg−1 for As, 41–4,890 mg kg−1 for Pb, 95–897 mg kg−1 for Zn and of 27–1,160 mg kg−1 for Cu. Most of the samples displayed concentrations of these elements higher than the 90th percentile of the corresponding
geological dominium, which suggests an anthropogenic input besides the bedrock influence. Samples collected from sediments
were more contaminated than leptosols because they were polluted by leachates or by mining spills coming from the waste rock
piles. The weathering of the bedrock is responsible for high concentrations in Co, Cr and Ni, but an anthropogenic input,
such as wind-blown dust, seems to be indicative of the high content of As, Cu, Pb and Zn in leptosols. The metal partitioning
patterns show that most trace elements are associated with Fe amorphous oxy-hydroxides, or take part of the residual fraction.
According to the results obtained, the following mobility sequence is proposed for major and minor elements: Mn, Pb, Cd, > Zn,
Cu > Ni > As > Fe > Cr. The high mobility of Pb, Cu and Zn involve an environmental risk in this area, even in soils where
the concentrations are not so high. 相似文献
68.
Daniel Bernard Jamal El Khattabi Emilie Lefevre Hani Serhal Sabine Bastin-Lacherez Isam Shahrour 《Environmental Geology》2008,53(5):1129-1138
In the north of France, high registers of nickel are sometimes recorded within the chalk aquifer. In a confined context, the
presence of pyrite in the covering clays or in the marcasite nodules encrusted in the clay may constitute a natural source
of trace metals. With an objective of sanitary control, the limits of chemical contents regulating the quality of water destined
for human consumption have been lowered by the European Framework Directive in the field of water policy (2000/60/EC). As
a result, nickel limits have been reduced from 50 to 20 μg/l. The analyses, carried out on three water catchment fields in
our area of study, were centred on variable parameters (Eh, O2(d), pH, Conductivity, T°), major elements (SO4, NO3) and metals (Fe, Ni, Mn, Co). The acquired data enabled us to identify from one hand, the conditions which are presented
within the site, special thanks to the evolution of nitrate and iron contents and on the other hand, the natural origin (geological)
of nickel for two of the three sites studied based essentially on the evaluation of the Nickel/Cobalt ratio. Thus, on the
first site, the evolution of nickel content and nitrate content showed the influence of the phenomenon of denitrification
on the re-mobilisation of the nickel. Whereas on the second site, a high variation of total iron content and oxygen dissolved
in solution highlighted a particular phenomenon of oxidation of the pyrite through molecular oxygen. Finally, the correlation
with the sulphates clearly showed behaviour of the nickel, once released, that was entirely dependent on the phenomenon of
adsorption on the iron and manganese hydroxides. 相似文献
69.
Mahmoud M. El Banna 《Environmental Geology》2008,54(6):1291-1299
Types, distribution, and origin of recent sand dunes between Rosetta and Idku, in the western sector of the Nile Delta, Egypt
were investigated. Sand samples from the dunes, beach, and seafloor were studied for grain size distribution and mineralogical
composition. It has been found that most of the dunes in the study area have been subjected to deterioration and removal due
to the construction of buildings and the International Coastal Highway. The remnant constitutes a damaged belt of foredunes
that extends from El Bouseily village to the west of Idku town. The dune’s origin is interpreted to be the result of coastal
drifting and the subsequent transport of sediments of the former Canopic Nile branch eastward by the predominant longshore
current and by aeolian processes. The blown sand grains accumulated to form a belt of coastal sand dunes of original longitudinal
and crescentic forms. Urbanization of the coast has severely altered the landscape. The study area is considered vulnerable
to the impacts of climate change and the expected rise in sea level. The outcome of potential sea level rise is serious; erosion
problems are expected to be exacerbated and vast areas from land and property would be lost. Thus, protection and preservation
the remaining dunes in the study area are vital requirements for shore protection. 相似文献
70.
N. Nur Ozyurt 《Environmental Geology》2008,54(4):731-736
Salinity and temperature variations in groundwater discharge from the Altug submarine karst cave have been observed at 28 m
below sea level for every 10 min between November 2004 and August 2005 to determine the drivers that govern the salinization.
Comparisons between temporal trends of salinity and temperature with those of precipitation, air pressure, sea level and wind
velocity revealed an apparent dominance of precipitation regime on the salinity and temperature variations. Spectral analyses
applied to observations showed that the air pressure and sea level oscillations are affected by sun and moon tides which do
not have an appreciable impact on the salinity and temperature variations. Annual rate of salinization in Altug cave seems
inversely related to the inland groundwater head so that the maximum and minimum fresh water contributions occur at mid-spring
and late-summer, respectively. 相似文献