全文获取类型
收费全文 | 416篇 |
免费 | 12篇 |
国内免费 | 6篇 |
专业分类
测绘学 | 46篇 |
大气科学 | 42篇 |
地球物理 | 84篇 |
地质学 | 133篇 |
海洋学 | 7篇 |
天文学 | 109篇 |
综合类 | 5篇 |
自然地理 | 8篇 |
出版年
2022年 | 7篇 |
2021年 | 2篇 |
2020年 | 7篇 |
2019年 | 6篇 |
2018年 | 19篇 |
2017年 | 25篇 |
2016年 | 24篇 |
2015年 | 20篇 |
2014年 | 36篇 |
2013年 | 29篇 |
2012年 | 20篇 |
2011年 | 28篇 |
2010年 | 14篇 |
2009年 | 21篇 |
2008年 | 14篇 |
2007年 | 4篇 |
2006年 | 14篇 |
2005年 | 5篇 |
2004年 | 4篇 |
2003年 | 13篇 |
2002年 | 11篇 |
2001年 | 6篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1998年 | 9篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有434条查询结果,搜索用时 62 毫秒
131.
Basic Oxygen Furnace (BOF) slag is a major waste product generated during the steelmaking process. In India and in most industrial countries, the use of BOF slag as a road ballast and land filler has had a very long history. This being a low end use, a study was conducted to examine the possibility of converting the slag into a hydraulic binder. This paper describes the effect of cooling rate on mineralogy and cementing characteristics of normal BOF slag as well as iron oxide-devoid BOF slag. Specifically, the mineralogy and compressive strengths of heat-treated slags were compared with a conventional ordinary Portland cement. It was found that the slowly cooled slags did not show any cementing properties. The iron oxide-devoid slag, on slow cooling, disintegrated into fine powder. The water-cured cubic specimens of quenched slag products were tested for their compressive strengths. The cementing properties of the quenched slag products were improved by formation of hydraulic phases and showed considerable strength after 28 days of water curing. 相似文献
132.
It is shown that a two-dimensional lower-hybrid wave structure can parametrically trigger the growth of VLF and ULF noises in a plasma. Analytical expressions for the increment and threshold of the instability are obtained. Application of our work to the auroral zones of the topside ionosphere is discussed. 相似文献
133.
A magnetograph is an instrument which makes measurement of solar magnetic field by measuring Zeeman induced polarization in
solar spectral lines. In a typical filter based magnetograph there are three main modules namely, polarimeter, narrow-band
spectrometer (filter), and imager(CCD camera). For a successful operation of magnetograph it is essential that these modules
work in synchronization with each other. Here, we describe the design of instrument control system implemented for the Solar
Vector Magnetograph under development at Udaipur Solar Observatory. The control software is written in Visual Basic and exploits
the Component Object Model (COM) components for a fast and flexible application development. The user can interact with the
instrument modules through a Graphical User Interface (GUI) and can program the sequence of magnetograph operations. The integration
of Interactive Data Language (IDL) ActiveX components in the interface provides a powerful tool for online visualization,
analysis and processing of images. 相似文献
134.
N. Bhandari S. V. S. Murty P. N. Shukla A. D. Shukla R. R. Mahajan M. M. Sarin G. Srinivasan K. M. Suthar M. S. Sisodia S. Jha A. Bischoff 《Meteoritics & planetary science》2002,37(4):549-563
Abstract— A stony meteorite fell at Itawa Bhopji, Rajasthan, India on 2000 May 30. This is the fifth recorded fall in a small area of Rajasthan during the past decade. The meteorite is an ordinary chondrite with light clasts in a dark matrix, consisting of a mixture of equilibrated (mainly type 5) and unequilibrated components. Olivine is Fa24–26 and pyroxene Fs20–22 but, within the unequilibrated components, olivine (Fa5–29) and low calcium pyroxene (Fs5–37) are highly variable. Based on petrographic studies and chemical analyses, it is classified as L(3–5) regolith breccia. Studies of various cosmogenic records, including several gamma‐emitting radionuclides varying in half‐life from 5.6 day 52Mn to 0.73 Ma 26Al, tracks and rare gases have been carried out. The exposure age of the meteorite is estimated from cosmogenic components of rare gases to be 19.6 Ma. The track density varies by a factor of ?3 (from 4 to 12 times 106/cm2) within the meteorite, indicating a preatmospheric body of ?9 cm radius (corresponding to a meteoroid mass of ?11 kg) and small ablation (1.5 to 3.6 cm). Trapped components in various rare gases are high and the solar component is present in the dark portion of the meteorite. Large excess of neutron‐produced 82Kr and 128Xe in both the light and the dark lithology but very low 60Co, indicating low neutron fluxes received by the meteoroid in the interplanetary space, are clear signatures of an additional irradiation on the parent body. 相似文献
135.
P. Mukhopadhyay J. Sanjay W. R. Cotton S. S. Singh 《Meteorology and Atmospheric Physics》2005,90(1-2):77-108
Summary An attempt has been made to study the impact of surface meteorological observations on the Regional Atmospheric Modelling System (RAMS) simulation of a monsoon depression and two low pressure systems. The surface observations are blended with the GEWEX Asian Monsoon Experiment (GAME) gridded analyses for these cases. In one set of experiments the model is run in 12 hour nudging mode initially and then in forecast mode using GAME gridded data without incorporating surface observations. In another set of experiments surface data are incorporated to enhance the signature of the systems in the large scale GAME analyses and nudging is applied initially for twelve hours. Subsequently the model is run in forecast mode to see the temporal and spatial evolution of different meteorological features associated with the systems. It is found that inclusion of the surface data has in general enhanced the signature of the systems in the analysis and subsequently shows improvement in the forecast of sea-level pressure, geopotential, wind field, etc. and the associated forecast of heavy rainfall, in particular. To make a quantitative comparison of the predicted rainfall with the observed one, equitable threat score and bias are calculated for different threshold values of rainfall. It is clearly noted that inclusion of surface data has improved the precipitation forecast over the Indian land mass as indicated by the equitable threat score and bias for all the threshold rainfall categories. 相似文献
136.
Agricultural management impacts on groundwater: simulations of existing and alternative management options in Peninsular India
下载免费PDF全文
![点击此处可从《水文研究》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Daniel R. Dourte Sanjay Shukla Dorota Z. Haman M. Devender Reddy M. Uma Devi Adusumilli Mani 《水文研究》2014,28(19):5021-5033
Understanding the principal causes and possible solutions for groundwater depletion in India is important for its water security, especially as it relates to agriculture. A study was conducted in an agricultural watershed in Andhra Pradesh, India to assess the impacts on groundwater of current and alternative agricultural management. Hydrological simulations were used as follows: (1) to evaluate the recharge benefits of water‐harvesting tillage through a modified Soil and Water Assessment Tool (SWAT) model and (2) to predict the groundwater response to changing extent and irrigation management of rice growing areas. The Green–Ampt infiltration routine was modified in SWAT was modified to represent water‐harvesting tillage using maximum depression storage parameter. Water‐harvesting tillage in rainfed croplands was shown to increase basin‐scale groundwater recharge by 3% and decrease run‐off by 43% compared with existing conventional tillage. The groundwater balance (recharge minus irrigation withdrawals), negative 11 mm/year under existing management changed to positive (18–45 mm/year) when rice growing areas or irrigation depths were reduced. Groundwater balance was sensitive to changes in rice cropland management, meaning even small changes in rice cropland management had large impacts on groundwater availability. The modified SWAT was capable of representing tillage management of varying maximum depression storage, and tillage for water‐harvesting was shown to be a potentially important strategy for producers to enhance infiltration and groundwater recharge, especially in semi‐arid regions where rainfall may be becoming increasingly variable. This enhanced SWAT could be used to evaluate the landscape‐scale impacts of alternative tillage management in other regions that are working to develop strategies for reducing groundwater depletion. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
137.
138.
Stability analysis of multi-directional anchored rock slope subjected to surcharge and seismic loads
Sanjay Kumar Shukla Md. Monir Hossain 《Soil Dynamics and Earthquake Engineering》2011,31(5-6):841-844
More than one set of anchors with different orientations can be an economical solution to completely stabilize the rock slope. In this note, a general analytical expression for the factor of safety of a multi-directional anchored rock slope (MDARS) against plane failure is derived, incorporating most of the practically occurring destabilizing forces under surcharge and seismic loading conditions. Several special cases of this expression are found to be similar to those reported in the literature. A graphical presentation shows that for any specific inclination of one set of anchors to the normal at failure plane, the variation in the inclination of the second set of anchors to the normal at failure plane, when greater than approximately 60°, does not cause a significant change in the factor of safety of the MDARS. 相似文献
139.
The eddy covariance (EC) method was used in a 30‐month study to quantify evapotranspiration (ET) and vegetation coefficient (KCW) for a wetland on a ranch in subtropical south Florida. To evaluate the errors in ET estimates, the EC‐based ET (ETC‐EC) and the Food and Agricultural Organization (FAO) Penman–Monteith (PM) based ET (ETC‐PM) estimates (with literature crop coefficient, KC) were compared with each other. The ETC‐EC and FAO‐PM reference ET were used to develop KCW. Regression models were developed to estimate KCW using climatic and hydrologic variables. Annual and daily ETC‐EC values were 1152 and 3.27 mm, respectively. The FAO‐PM model underestimated ET by 25% with ETC‐EC being statistically higher than ETC‐PM. The KCW varied from 0.79 (December) to 1.06 (November). The mean KCW for the dry (November–April) season (0.95) was much higher than values reported for wetlands in literature; whereas for the wet (May–October) season, KCW (0.97) was closer to literature values. Higher than expected KCW values during the dry season were due to higher temperature, lower humidity and perennial wetland vegetation. Regression analyses showed that factors affecting the KCW were different during the dry (soil moisture, temperature and relative humidity) and wet (net radiation, inundation and wind speed) seasons. Separate regression models for the dry and wet seasons were developed. Evapotranspiration and KCW from this study, one of the first for the agricultural wetlands in subtropical environment, will help improve the ET estimates for similar wetlands. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献