全文获取类型
收费全文 | 348篇 |
免费 | 5篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 25篇 |
大气科学 | 22篇 |
地球物理 | 54篇 |
地质学 | 183篇 |
海洋学 | 13篇 |
天文学 | 48篇 |
综合类 | 2篇 |
自然地理 | 8篇 |
出版年
2022年 | 7篇 |
2021年 | 6篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 16篇 |
2017年 | 20篇 |
2016年 | 21篇 |
2015年 | 10篇 |
2014年 | 16篇 |
2013年 | 29篇 |
2012年 | 13篇 |
2011年 | 24篇 |
2010年 | 24篇 |
2009年 | 15篇 |
2008年 | 7篇 |
2007年 | 7篇 |
2006年 | 11篇 |
2005年 | 8篇 |
2004年 | 3篇 |
2003年 | 9篇 |
2002年 | 5篇 |
2001年 | 7篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 6篇 |
1995年 | 8篇 |
1994年 | 3篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1967年 | 1篇 |
1966年 | 2篇 |
1965年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有355条查询结果,搜索用时 31 毫秒
11.
Irene Sarkar 《Journal of Asian Earth Sciences》2004,22(5):529
The moderate magnitude Chamoli earthquake that occurred in the Garhwal Higher Himalaya, in the early hours of March 29, 1999, caused intense damage to the ground and mountain slopes of the Alaknanda–Mandakini river valley and adjoining region. A systematic survey of this induced damage was conducted immediately after the earthquake occurred. Prominent shallow cracks of significant length, negligible width and indeterminate vertical extent, conspicuously tensile in nature, with little or no slip across the crack planes, were observed in the ground at several places along the surveyed route. These cracks had formed in the dynamic phase of the Chamoli earthquake process that is in the period of time during which the earthquake-generated seismic waves were passing through the geographic region of interest. However, we use the theory of earthquake-induced static (or long time) stress changes to visualize such cracks at some selected sites where ground damage was relatively more intense and varied to suggest lower bound estimates of the dynamic stress contributions of the main shock for their formation.Based on the results of our analysis we conclude that, just prior to the earthquake occurrence, under the influence of the local ambient stress field, the ground at these sites was already near failure in tension. To this, in its dynamic phase, the Chamoli earthquake induced stress perturbations, having, across the planes of the cracks, (i) shear components which were nearly equal and opposite to similar components of the ambient stress field and (ii) normal (tensile) components, necessary for triggering tensile failure of the ground. The σ3 (or minimum principal stress) component of the resultant perturbed failure stress field thus became sufficiently tensile while the transverse stresses became sufficiently insignificant. This facilitated formation of major tensile cracks in the ground there. Our static estimates of the tensile stress changes at the different sites are, in essence, estimates of the minimal triggering stress perturbations that was provided by the Chamoli earthquake in the dynamic state for the formation of the tensile cracks there. 相似文献
12.
Prasanta Kumar Behera Kripamoy Sarkar Ashok Kumar Singh A. K. Verma T. N. Singh 《Journal of the Geological Society of India》2016,88(6):725-735
In opencast mining operation, the stability of waste materials stands at high priority from the safety and economic perspective. Poor management of overburden (OB) dump results the instability of slope in an opencast mine. The present paper deals with the stability analysis of dump material of an opencast coal mine at Talcher coal field, Angul district, Odisha, by means of different geotechnical parameters and mineralogical composition affecting the dump slope. The prolonged rainfall in the mining area causes dump failure and loss of valuable life and property. A recent dump failure that occurred in 2013 at Basundhara mines of Mahanadi Coalfields Limited (MCL), Odisha, took 14 lives, and created problems for the mining industry. Most of the dump failure that occurs in the study area are mainly due to increase in pore water pressure as a result of rainfall infiltration. The stability of the waste dump was investigated using the limit equilibrium analysis to suggest an economical, sustainable and safe disposal of the dump in the study area. 相似文献
13.
14.
Subhadeep Banerjee Minu Joy Debdeep Sarkar 《Geotechnical and Geological Engineering》2016,34(6):1899-1908
This paper examines seismic effects on fixed-head, end-bearing piles installed through soft clay. The numerical analyses were conducted using ABAQUS with a hypoelastic constitutive model for the clay. The dimensionless parameters involving the major parameters such as pile modulus, soil modulus, slenderness ratio, natural frequencies of clay layer and pile–raft, superstructure mass, density of the soil and peak ground acceleration were obtained from the parametric studies. The relationships for the amplification of ground motions and the maximum bending moment in the pile were developed based on regression of the numerical data. The computed results from the proposed relationships were compared with the results reported in the past studies. 相似文献
15.
16.
17.
The Cretaceous(Albian-Cenomanian) Dalmiapuram Formation is one of the economically significant constituents in the hydrocarbon-producing Cauvery rift basin, SE India that opened up during the Late Jurassic e Early Cretaceous Gondwanaland fragmentation. The fossil-rich Dalmiapuram Formation,exposed at Ariyalur within the Pondicherry sub-basin of Cauvery Basin, rests in most places directly on the Archean basement and locally on the Lower Cretaceous(Barremian-Aptian) Basal Siliciclastic Formation. In the Dalmiapuram Formation, a facies association of tectonically-disturbed phase is sandwiched between two drastically quieter phases. The early syn-rift facies association(FA 1), records the first carbonate marine transgression within the basin, comprising a bar-lagoon system with occasionally storms affecting along the shore and a sheet-like non-recurrent biomicritic limestone bed on the shallow shelf that laterally grades into pyrite e glauconite-bearing dark-colored shale in the deeper shelf. Spectacular breccias together with varied kinds of mass-flow products comprise the syn-rift facies association(FA 2). While the breccias occur at the basin margin area, the latter extend in the deeper inland sea. Clast composition of the coarse clastics includes large, even block-sized limestone fragments and small fragments of granite and sandstone from the basement.Marl beds of quieter intervals between tectonic pulses occur in alternation with them. Faulted basal contact of the formation, and small grabens filled by multiple mass-flow packages bear the clear signature of the syntectonic activity localized contortions, slump folds, and pillow beds associated with mega slump/slide planes and joints, which corroborates this contention further. This phase of tectonic intervention is followed by another relatively quieter phase and accommodates the late syn-rift facies association(FA 3). A tidal bar-interbar shelf depositional system allowed a transgressive systems tract motif to grow eventually passing upwards into the Karai Shale Formation, whose contact with the Dalmiapuram Formation is gradational. 相似文献
18.
Prakash Abhishek Piazolo Sandra Saha Lopamudra Bhattacharya Abhijit Pal Durgesh Kumar Sarkar Saheli 《International Journal of Earth Sciences》2018,107(6):2265-2292
International Journal of Earth Sciences - In the present study we investigate the microstructural development in mullite, quartz and garnet in an anatectic migmatite hosted within a Grenvillian-age... 相似文献
19.
Chris?HarrisEmail authorView authors OrcID profile Kwenidyn?Mulder Saheli?Sarkar Benjamin?Whitehead Sherissa?Roopnarain 《Contributions to Mineralogy and Petrology》2018,173(4):30
This paper investigates the origin of low-δ18O quartz porphyry dykes associated with the 144–133 Ma Koegel Fontein Igneous Complex, which was intruded during the initial phase of breakup of Africa and South America. The 25-km diameter Rietpoort Granite is the largest and youngest phase of activity, and is roofed by a 10-km diameter pendant of gneiss. Quartz porphyry (QP) dykes, up to 15 m in width, strike NW–SE across the complex. The QP dykes that intruded outside the granite have similar quartz phenocryst δ18O values (average 8.0‰, ± 0.7, n?=?33) to the granite (average 8.3?±?1.0, n?=?7). The QP dykes that intruded the roof pendant have quartz phenocrysts with more variable δ18O values (average 1.6‰, ± 2.1, n?=?55). In some cases quartz phenocrysts have δ18O values as low as ? 2.5‰. The variation in δ18O value within the quartz crystal population of individual dykes is small relative to the overall range, and core and rim material from individual quartz phenocrysts in three samples are identical within error. There is no evidence that quartz phenocryst δ18O values have been affected by fluid–rock interaction. Based on a ?quartz?magma value of 0.6‰, magma δ18O values must have been as low as ? 3.1‰. Samples collected along the length of the two main QP dykes that traverse the roof pendant have quartz phenocryst δ18O values that range from +?1.1 to +?4.6‰, and ? 2.3 to +?5.6‰, respectively. These δ18O values correlate negatively (r = ? 0.96) with initial 87Sr/86Sr, which can be explained by the event that lowered δ18O values of the source being older than the dykes. We suggest that the QP dykes were fed by magma produced by partial melting of gneiss, which had been variably altered at high temperature by 18O-depleted meteoric water during global glaciation at ~?550 Ma. The early melts had variable δ18O value but as melt pockets interconnected during melting, the δ18O values approached that of average gneiss. Variable quartz phenocryst δ18O values in the same dyke can be explained by vertical emplacement, at variable rates of ascent along the dyke. The lateral variation in quartz, and hence magma δ18O value at a particular point along a single dyke would depend on the rate of ascent of magma at that point along the dyke, and the ‘age’ of the particular magma batch. 相似文献
20.
GeoJournal - Using a cross-sectional survey, the study aims to understand scarcity of nutrition consumption among rural households in West Bengal. Most of the research related to nutrition and... 相似文献