全文获取类型
收费全文 | 205篇 |
免费 | 3篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 11篇 |
大气科学 | 14篇 |
地球物理 | 38篇 |
地质学 | 68篇 |
海洋学 | 10篇 |
天文学 | 63篇 |
综合类 | 3篇 |
自然地理 | 3篇 |
出版年
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 1篇 |
2018年 | 11篇 |
2017年 | 9篇 |
2016年 | 11篇 |
2015年 | 4篇 |
2014年 | 7篇 |
2013年 | 10篇 |
2012年 | 5篇 |
2011年 | 13篇 |
2010年 | 10篇 |
2009年 | 15篇 |
2008年 | 14篇 |
2007年 | 3篇 |
2006年 | 3篇 |
2005年 | 1篇 |
2004年 | 3篇 |
2003年 | 4篇 |
2002年 | 3篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 5篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 10篇 |
1978年 | 4篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1972年 | 3篇 |
1971年 | 2篇 |
1965年 | 1篇 |
1964年 | 2篇 |
排序方式: 共有210条查询结果,搜索用时 62 毫秒
71.
Rabindra Nath Hota 《Journal of the Geological Society of India》2018,92(4):479-483
Cross-association analysis of lithologies and microfacies of two borehole sections of the Barren Measures Formation, Talcher coalfield situated 12 km apart show strikingly dissimilar results. In case of lithologies, one-to-one correlation becomes significant, which suggests continuity of the formation throughout the Barren Measures Formation and prevalence of braided stream depositional environment. However, lack of significant correlation of microfacies suggests existence of different sub-environments at different parts of the Barren Measures Formation during each stage of sedimentation. When channel facies were laid down at one place, homotaxial leeve, floodplain and swamp facies were deposited elsewhere. 相似文献
72.
Prioritization of soil conservation measures using erodibility indices as criteria in Sikkim (India)
Erodibility indices are important parameter that can be used to describe the intensity of the soil erosion problems causing environmental concerns. These indices are convenient to estimate the susceptibility to erosion where physical measurement is very difficult. Sikkim is one such state in India where measuring erosion is a tedious process due to its difficult and inaccessible terrain conditions. In the present study, spatial variation of susceptibility of erosion in East district of Sikkim was estimated by using indices such as clay ratio, dispersion ratio, mod clay ratio and critical level of soil organic matter. The result indicates soils in East district are mostly dominated by sand particles (40.5–81.06%) in majority of soil samples. The dispersion ratio values in most of the soils were >15% indicating very high vulnerability to erosion. The values of clay ratio (3.44–9), modified clay ratio (mean value of 6.9) and critical level of soil organic matter content (<5%) indicated high susceptibility to erosion. The trends of indices were generated by IDW interpolation method to understand the spatial variation of the susceptibility to erosion. The interpolated maps were overlaid on subwatershed maps to prioritize the subwatershed for planning treatment measures. 相似文献
73.
T. M. Patel K. Nath 《International Journal of Environmental Science and Technology》2014,11(5):1237-1248
Nanofiltration of ternary mixtures of sodium chloride and aqueous solutions of Reactive Black-5 was studied in two different modules, namely, flat sheet and spiral wound over a wide range of operating conditions. Hydrophilized polyamide membrane with molecular weight cutoff of 150 was used for the experiments. Combined effect of dye and salt concentration, trans-membrane pressure drop, initial pH of feed solution on the permeate flux, and observed retention were investigated. Extent of color removal, chemical oxygen demand (COD), total dissolved solid (TDS), and conductivity were determined to assess performance of the membrane. The experimental results showed that both the permeate flux and observed retention decreased with increase in dye as well as salt concentration in the feed. Permeate fluxes were lower at higher pH values. Substantial removal of color was achieved in the nanofiltration experiments with a marked reduction in COD and TDS. The process allowed the production of permeate stream with great reutilization possibilities. 相似文献
74.
Swarniv Chandra Sailendra Nath Paul Basudev Ghosh 《Astrophysics and Space Science》2013,343(1):213-219
Using the Quantum hydrodynamic (QHD) model Korteweg-de Vries (KdV) type solitary excitations of electron-acoustic waves (EAWs) have been examined in a two-electron-populated relativistically degenerate super dense plasma. It is shown that relativistic degeneracy parameter significantly influences the conditions of formation and properties of solitary structures. 相似文献
75.
Observations of dust grains in the intergalactic medium (IGM) allow us to study an important aspect in the evolution of galaxies.
Although its existence had been previously speculated upon, direct evidence of the presence of dust in the intergalactic space
has only been available recently. We discuss various issues regarding the presence of dust in the IGM—its sources, transport
mechanisms from galaxies into the IGM, its effect on reddening and on cosmological studies. 相似文献
76.
Assam–Arunachal forest fringed foothill area is endemic for malaria incidence. The present study deals with the temporal analysis of malaria incidence and determines its association with deforestation in 24 villages along the Assam–Arunachal forest fringed foothill area of Sonitpur district of Assam. Malaria epidemiological survey has been carried out in the study area from the year 1994 to 2005. Remote sensing (RS) technique has been used to map the areas of forest changes from the year 2000 to 2005. Geographical information system (GIS) was used to map the malaria incidence and forest cover. The study villages are endemic to malaria infections and there was increasing trend of malaria incidence over the years. The slide positivity rate (SPR) ranged from 5.1% in 1997 to 44.4% in 2005. The percentage forest cover decreased significantly from 23.6% during 2000 to 15.4% during 2005, whereas SPR was increased during 2000–2005. The present study is the first attempt to understand the role of deforestation in malaria incidence using RS and GIS in the north-eastern region of India at a micro-geographic level. The study suggests that the area is endemic to malaria transmission. The decrease in forest cover is a serious ecological concern besides its role in elevating the malaria incidence in the study area. 相似文献
77.
Ground-motion predictions in Shillong region, northeast India 总被引:1,自引:0,他引:1
Sankar Kumar Nath Kiran Kumar Singh Thingbaijam Soumya Kanti Maiti Avinash Nayak 《Journal of Seismology》2012,16(3):475-488
We deliver ground-motion prediction equations for Shillong region, northeast India, based on a database generated by finite-fault stochastic simulations. An examination of the regional seismic source characteristics is carried out beforehand. Micro/minor earthquakes (M W?<?5.0) nucleating at hypocentral depth <21?km in the region recorded at broadband seismic stations are observed to have Brune stress-drop ranging between 2.8 and 99.9?bars. Likewise, macroseismic intensity data for the 1897 Shillong Earthquake that nucleated at a hypocentral depth of ~35?km places the associated stress-drop at 100?200?bars. The apparent variation of the stress-drop parameter with depth is considered with two source zones namely lower-crust and upper-crust. Equations for the lower-crust predict higher ground-motion levels and exhibit affinity to those developed for stable continental region of Eastern North America. The ground-motion levels predicted by the equations for the upper-crust are relatively lower but are still higher compared with those predicted for tectonically active regions, viz., the Himalayas and Western North America. 相似文献
78.
79.
Evaluation of performance of non‐invasive upgrade strategy for beam–column sub‐assemblages of poorly designed structures under seismic type loading
下载免费PDF全文
![点击此处可从《地震工程与结构动力学》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Beam–column sub‐assemblages are the one of the most vulnerable structural elements to the seismic loading and may lead to devastating consequences. In order to improve the performance of the poorly/under‐designed building structures to the critical loading scenarios, introduction of steel bracing at the RC beam–column joint is found to be one of the modern and implementable techniques. In the present work, a diagonal metallic single haunch/bracing system is introduced at the beam–column joints to provide an alternate load path and to protect the joint zone from extensive damage because of brittle shear failure. In this paper, an investigation is reported on the evaluation of tae influence of different parameters, such as angle of inclination, location of bracing and axial stiffness of the single steel bracing on improving the performance through altering the force transfer mechanism. Numerical investigations on the performance of the beam–column sub‐assemblages have been carried out under cyclic loading using non‐linear finite element analysis. Experimentally validated numerical models (both GLD and upgraded specimen) have been further used for evaluating the performance of various upgrade schemes. Cyclic behaviour of reinforcement, concrete modelling based on fracture energy, bond‐slip relations between concrete and steel reinforcement have been incorporated. The study also includes the numerical investigation of crack and failure patterns, ultimate load carrying capacity, load displacement hysteresis, energy dissipation and ductility. The findings of the present study would be helpful to the engineers to develop suitable, feasible and efficient upgrade schemes for poorly designed structures under seismic loading. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
80.
The cyclic arrangement of lithofacies of the Karharbari Formation of the Damuda Group from a part of the Talchir Gondwana
basin has been examined by statistical techniques. The lithologies have been condensed into five facies states viz. coarse-,
medium-, fine-grained sandstones, shale and coal for the convenience of statistical analyses. Markov chain analysis indicates
the arrangement of Karharbari lithofacies in form of fining upward cycles. A complete cycle consists of conglomerate or coarse-grained
sandstone at the base sequentially succeeded by medium-and fine-grained sandstones, shale and coal at the top. The entropy
analysis categorizes the Karharbari cycles into the C-type cyclicity, which is essentially a random sequence of lithologic
states. Regression analysis undertaken in the present study indicates the existence of sympathetic relationship between total
thickness of strata (net subsidence) and number and average thickness of sedimentary cycle and antipathic relationship between
number and average thickness of sedimentary cycle. These observations suggest that cyclic sedimentation of the Karharbari
Formation was controlled by autocyclic process by means of lateral migration of streams activated by intrabasinal differential
subsidence, which operated within the depositional basin and the channels carrying coarse grade clastic sediments, which make
the cycles thicker, tend to be more common in the areas of maximum subsidence. Clastic sediments issued from the laterally
migrating rivers interrupted the cyclic sedimentation of the Karharbari Formation in many instances. 相似文献