首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   166篇
  免费   1篇
  国内免费   1篇
测绘学   44篇
大气科学   6篇
地球物理   16篇
地质学   63篇
海洋学   4篇
天文学   30篇
综合类   2篇
自然地理   3篇
  2024年   1篇
  2023年   1篇
  2021年   7篇
  2020年   1篇
  2019年   4篇
  2018年   10篇
  2017年   15篇
  2016年   13篇
  2015年   5篇
  2014年   9篇
  2013年   10篇
  2012年   7篇
  2011年   9篇
  2010年   7篇
  2009年   10篇
  2008年   6篇
  2007年   5篇
  2006年   6篇
  2005年   3篇
  2004年   5篇
  2001年   1篇
  2000年   2篇
  1999年   2篇
  1998年   1篇
  1996年   2篇
  1995年   2篇
  1992年   4篇
  1991年   3篇
  1990年   2篇
  1987年   1篇
  1985年   1篇
  1983年   1篇
  1982年   5篇
  1981年   1篇
  1980年   1篇
  1979年   3篇
  1974年   1篇
  1973年   1篇
排序方式: 共有168条查询结果,搜索用时 15 毫秒
41.
A method of seismic zonation based on deterministic modeling of rupture plane is presented in this work. This method is based on the modeling of finite rupture plane along identified lineaments in the region using the semi-empirical technique, of Midorikawa [(1993) Tectonophysics 218:287–295]. The modeling procedure follows ω2 scaling law, directivity effects, and other strong motion parameters. The technique of zonation is applied for technoeconomically important NE part of Brahmaputra valley that falls in the seismic gap region of Himalaya. Zonation map prepared for Brahmaputra valley for earthquakes of magnitude M > 6.0 show that approximately 90,000 km2 area fall in the highly hazardous zone IV, which covers region that can have peak ground accelerations of order more than 250 cm/s2. The zone IV covers the Tezu, Tinsukia, Dibrugarh, Ziro, North Lakhimpur, Itanagar, Sibsagar, Jorhat, Golaghat, Wokha, Senapati, Imphal, and Kohima regions. The Pasighat, Daring, Basar, and Seppa region belong to zone III with peak ground accelerations of the order 200–250 cm/s2. The seismic zonation map obtained from deterministic modeling of the rupture is consistent with the historical seismicity map and it has been found that the epicenter of many moderate and major earthquakes fall in the identified zones.  相似文献   
42.
The fluidity of land-use patterns over the last century in and around the Baroda Urban Complex has been worked out using Survey of India topographic maps (1876–78, 1959–60) and SPOT satellite imagery (1988). The most striking feature of this study was the alarming loss of non-built up areas comprising agricultural land to urban sprawl. In 1876–78, non-built up land constituted 701.30 sq. km out of a total of 714 sq. km whereas in 1988, it was reduced to 625.27 sq. km. This urban growth pattern would not be conducive for sustainable development.  相似文献   
43.
Microwave sensors having all-weather capabilities provide an opportunity to monitor rice grown in monsoon season. An attempt has been made to identify rice crop using multitemporal ERS-1 SAR data in C-band (5.3 GHz). Data acquired on August 15 (D1), September 19 (D2), October 24 (D3) and November 28 (D4) 1993 were taken. Combinations of data acquired on different dates were used for identification of rice crop. Single-date IRS-1B LISS II data in visible and NIR bands acquired on October 23, 1993 was also used for comparison of estimated rice area. Analysis of the results has shown that a combination of SAR data acquired at the tillering (August), booting (September) and heading (October) stages of rice crop enabled identification and area estimation of rice crop grown under lowland conditions. Single-date SAR data acquired in the month of October was found to be better for identification of rice compared to other dates.  相似文献   
44.
The problem of estimating the proportion of lithological (ore) types in volumes of mineral deposits is considered when an auxiliary variable Z(z) is observed along with the lithology L(x) at x. The process {Z(x)} is assumed to be stationary and an assumption on the statistical relationship between {Z(x)} and {L(x)} processes is made. Consequently, the second-order stationarity of {L(x)} is not required. A method using the kriged distribution of the auxiliary variable is proposed. A case study illustrating the procedure is given.  相似文献   
45.
Exhumation has been recognised as a key factor in understanding the dynamics of a mountain belt. Normal faulting, erosion and ductile thinning are the three basic mechanisms to exhume the deeper high grade metamorphic rocks to the surface. Convergent orogenic belts are characterised by over-thickening of the crust due to thrusting and folding. The interplay of uplift due to over-thickening of crust and climatic-erosion is the most plausible mechanism of exhumation as suggested by the numerical models and analogue experiments. The analysis of 534 thermo-chronological dates through 1D-thermal numerical model in the Himalaya suggest that the exhumation is dominantly due to erosion but the pattern of erosion is controlled by local tectonic activities in different sector of the Himalaya since Miocene, indicating that tectonic force as the prime mechanism of exhumation in Himalaya.  相似文献   
46.
Plug-shaped ichnofossils Conichnus conicus, Conostichus broadheadi and C. stouti are found in the intercalated micritic sandstone and sandy allochemic limestone shale sequence of Bagh Group, Narmada district, Gujarat. These ichnospecies occur at two stratigraphic levels and shows distinct morphological features interpreted as resting/dwelling structures of sea anemone. The occurrence of these ichnospecies along with oyster fossils genera like Bosostrea and Indostrea indicate shallow marine environment.  相似文献   
47.
The research presented in this article is based on a new technique governed by three different statistical indicators determined for each causative parameter, viz. highest density, average density and co-efficient of variation of landslides. Each of these indicators was assigned a rank value between 1 and 14 depending upon its variation among the 14 causative parameters. The aggregate of the three types of rank values estimate the total ranking value (TRV) for each causative parameter. The study area is divided into 78,256 spatial units and for each such spatial unit, the influence of the different causative parameters is determined as the product of the experts' weight of the associated sub-category and the TRV of the causative parameter that categorizes the study area into various zones. The efficacy of the proposed technique is demonstrated by the occurrence of significantly high prediction accuracy of 84%.  相似文献   
48.
A study was conducted in the Bathinda district of Punjab state for mapping the cropping pattern and crop rotation, monitoring long term changes in cropping pattern by using the satellite based remote sensing data along other spatial and non-spatial collateral data. Multi-date IRS LISS I and IRS WiFS sensor data have been used for this study. Cropping pattern maps and crop rotation maps were generated for the years 1988-89 and 1998-99. The present study has shown the increase of cropping intensity significantly, mainly due to increase in rice area. However, crop diversity has decreased mainly due to decline in the area under the minor crops like pearl millet, gram, rapeseed/ mustard. There is increase in area coverage of cotton-wheat and rice-wheat rotation, at the expense of the minor crops.  相似文献   
49.
The pelitic schists of the area around Kandra, Singhbhum district, Jharkhand belong to the Chaibasa Formation of the Singhbhum Group, which constitute a part of the youngest Precambrian orogenic cycle of the Singhbhum region. Structurally, the area represents the Singhbhum anticlinorium and is overlain by Dalma traps which form the synclinorium towards the north of the area around Kandra. This area mainly consists of medium to high grade rocks belonging to greenschist and amphibolite facies. These rocks are folded in the E-W trending doubly plunging folds (F1) overturned towards the south with low plunges and superposed by cross-folds (F2). The spatial distribution of the index minerals in the pelitic schists of the area shows Barrovian type of metamorphism. Four isograds, viz. biotite, garnet, staurolite and sillimanite have been delineated by the first appearance of the index minerals and also by isograd reactions. The textural relation suggests that sillimanite is formed from staurolite consumption reaction instead of kyanite consumption.  相似文献   
50.
I he aim of the piesent study was to suggest an approach for national level acreage estimation for wheat using satellite remote sensing data and demonstrate its perfromantee Multi-date moderate resolution (188 m) IRS-IC WiFS data sets were used as the core data Sampie segment approach with stratified random sampling was used for the data analysis For making meaningful comparisons over time, multi-date sets were geometncally registered and radiometrically normalised by extracting pseudo-invariant Features and performing regression analysis on the digital numbers of such features The corrected multi-temporal data sets were used in hierarchical classification scheme. The results of this exercise are presented. It appeals that there is an overestimatoin of wheat acreage The sampling effieieney was also low, indicating need to improve sampling strategy Some of the problems encountered and the corrections planned to overcome them are also discussed  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号