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   473篇
  免费   6篇
  国内免费   6篇
测绘学   34篇
大气科学   25篇
地球物理   69篇
地质学   195篇
海洋学   21篇
天文学   120篇
综合类   5篇
自然地理   16篇
  2022年   8篇
  2021年   10篇
  2020年   10篇
  2019年   8篇
  2018年   25篇
  2017年   24篇
  2016年   23篇
  2015年   17篇
  2014年   23篇
  2013年   35篇
  2012年   26篇
  2011年   26篇
  2010年   21篇
  2009年   17篇
  2008年   20篇
  2007年   18篇
  2006年   28篇
  2005年   12篇
  2004年   10篇
  2003年   12篇
  2002年   8篇
  2001年   6篇
  2000年   9篇
  1999年   3篇
  1998年   9篇
  1997年   8篇
  1996年   5篇
  1995年   5篇
  1994年   6篇
  1993年   4篇
  1992年   5篇
  1991年   5篇
  1990年   2篇
  1989年   3篇
  1988年   1篇
  1987年   4篇
  1986年   1篇
  1985年   1篇
  1984年   2篇
  1983年   1篇
  1982年   4篇
  1981年   3篇
  1980年   4篇
  1979年   3篇
  1978年   3篇
  1976年   3篇
  1975年   1篇
  1973年   1篇
  1972年   1篇
  1970年   1篇
排序方式: 共有485条查询结果,搜索用时 62 毫秒
101.
This paper presents a study for linking remotely sensed data with property tax related issues. First, it discusses the key attributes required for property taxation and evaluates the capabilities of remote sensing technology to measure these attributes accurately at parcel level. Next, it presents a detailed case study of six representative wards of different characteristics in Dehradun, India, that illustrates how measurements of several of these attributes supported by field survey can be combined to address the issues related to property taxation. Information derived for various factors quantifies the property taxation contributed by an average dwelling unit of the different income groups. Results show that the property tax calculated in different wards varies between 55% for the high-income group, 32% for the middle-income group, 12% for the low-income group and 1% for squatter units. The study concludes that higher spatial resolution satellite data and integrates social survey helps to assess the socio-economic status of the population for tax contribution purposes.  相似文献   
102.
The Karakoram Shear Zone (KSZ) is a northwest-southeast trending dextral ductile shear zone that has mylonitized the Tangste and Darbuk granitoids of the southern margin of the Asian plate. Kinematic vorticity (Wk) has been estimated in 6 mylonitized Tangste granite samples, using Porphyroclast Hyperbolic Distribution (PHD) and Shear Band (SB) Analyses methods on well-developed quartz and feldspar porphyroclasts, and synthetic and antithetic shear bands respectively to visualize the overall deformation of the KSZ. The PHD and SB analyses yield Wk values ranging from Wk=0.29 to 0.43 and 0.45 to 0.93, respectively, thus indicating distinct pure and simple shear dominant regimes during different stages of the evolution of the KSZ. Strain has essentially been pure shear when southern edge of the Asian plate was initially juxtaposed against the Indian plate around 70 Ma, and changed to simple shear, possibly during the reactivation of this shear zone during 21-13 Ma to produce the shear bands.  相似文献   
103.
In this study, an integrated multi-channel analysis of Surface Waves (MASW) technique is applied to explore the geotechnical parameters of subsurface layers at the Zafarana wind farm. Moreover, a seismic hazard procedure based on the extended deterministic technique is used to estimate the seismic hazard load for the investigated area. The study area includes many active fault systems along the Gulf of Suez that cause many moderate and large earthquakes. Overall, the seismic activity of the area has recently become better understood following the use of new waveform inversion method and software to develop accurate focal mechanism solutions for recent recorded earthquakes around the studied area. These earthquakes resulted in major stress-drops in the Eastern desert and the Gulf of Suez area. These findings have helped to reshape the understanding of the seismotectonic environment of the Gulf of Suez area, which is a perplexing tectonic domain. Based on the collected new information and data, this study uses an extended deterministic approach to re-examine the seismic hazard for the Gulf of Suez region, particularly the wind turbine towers at Zafarana Wind Farm and its vicinity. Alternate seismic source and magnitude-frequency relationships were combined with various indigenous attenuation relationships, adapted within a logic tree formulation, to quantify and project the regional exposure on a set of hazard maps. We select two desired exceedance probabilities (10 and 20 %) that any of the applied scenarios may exceed the largest median ground acceleration. The ground motion was calculated at 50th, 84th percentile levels for both selected probabilities of exceeding the median.  相似文献   
104.
Stability of an Embankment on Soft Consolidating Soil with Vertical Drains   总被引:1,自引:0,他引:1  
Stability of an embankment constructed on soft consolidating soil improved with pre-fabricated vertical drains is investigated. The factor of safety of the embankment is obtained at various time intervals from the end of construction till the end of consolidation in order to check the embankment stability. Finite element method is used to obtain the effective stresses at required points in soil at various time intervals. Critical slip surface is obtained using two methods. In the first method, the critical slip surface is assumed as an arc of a circle selected among various probable slip circles with minimum factor of safety whereas, in the second method, a random walking type Monte Carlo technique is used to predict the critical slip surface. The effects of providing vertical drains on stability of an embankment is investigated by comparing the factor of safety of slope with vertical drains to the factor of safety of slope without vertical drains. It is concluded from the study that the installation of vertical drains enhances the factor of safety of the embankment from the end of construction till the end of consolidation.  相似文献   
105.
106.
A depth-averaged numerical model has been developed to study tidal circulation and suspended sediment transport in the Gulf of Kachchh including Kandla creek, west coast of India. The resolution of the model is taken as 750 m × 750 m, which is found to be adequate for the gulf region. However, this resolution could not produce the realistic circulation pattern and suspended sediment concentration in the Kandla creek region. There is a major seaport at Kandla which serves as the sea gate to northwest India. Therefore, a 2-D fine resolution (75 m × 75 m) model for Kandla creek has been developed and coupled with the coarser gulf model to compute the flow features in the creek region. The model dynamics and basic formulation remain the same for both the gulf model and the creek model. The models are barotropic, based on shallow water equations, and neglect horizontal diffusion and wind stress terms in the momentum equations. The models are fully nonlinear and use a semiexplicit finite difference scheme to solve mass, momentum, and advection-diffusion equations in a horizontal plane. The tide in the gulf is represented in the model by the semidiurnal M2 constituent mainly. In this study, no fresh water discharge conditions have been considered so the results are appropriate for the dry season. Numerical experiments are carried out to study the circulation and suspended sediment concentrations in the gulf and the creek regions. The computed results are validated with the available observations.  相似文献   
107.
A modified Newton-Raphson iterative technique is formulated for obtaining the static configuration of the Lazy "S" flexible marine riser between the floater and mid-arch buoy under its submerged self weight and the applied top tension. The geometrically non-linear problem is solved by finite difference with the above technique. The problem is formulated as a regular boundary value problem with specified moments and deflections at both ends. Usually the bending stiffness of the flexible riser made of Coflexip pipe is very low. By use of the above analysis, several flexible riser configurations are analyzed and their characteristic behaviors are investigated. Also, changes in the riser characteristics due to quasi-static motion of the floater end are estimated for the safety of the riser layout.  相似文献   
108.
Using a large set of rainfall–runoff data from 234 watersheds in the USA, a catchment area‐based evaluation of the modified version of the Mishra and Singh (2002a) model was performed. The model is based on the Soil Conservation Service Curve Number (SCS‐CN) methodology and incorporates the antecedent moisture in computation of direct surface runoff. Comparison with the existing SCS‐CN method showed that the modified version performed better than did the existing one on the data of all seven area‐based groups of watersheds ranging from 0·01 to 310·3 km2. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   
109.
Sharad K. Jain 《水文研究》2012,26(22):3472-3476
Flow is considered to be the master variable for a river because the fluvial processes and health of its ecosystem critically depend upon flow. Increasing water withdrawals from many rivers of the world are leading to severe degradation in river ecosystems. Water is allocated for environmental needs so that a river can perform its natural functions. This article discusses the concept of environmental flow, methods to assess it, and issues in implementation. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   
110.
We report here results from a study of X-ray bursts from 3 magnetar candidates (SGR 1806-20, SGR 1900+14 and AXP 1E 2259+586). We have searched for a pulse phase dependence of the X-ray burst rate from these sources. X-ray light curves were obtained with the Proportional Counter Array on-board the Rossi X-ray Timing Explorer during the periods of intense burst activity in these sources. On detailed analysis of the three sources, we found a very significant burst rate for all pulsar phases. However, some locations appear to produce bursts slightly more often, rendering the non-isotropic distribution. Only in the case of SGR 1900+14, there is a clear pulse phase dependence of burst rate.  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