全文获取类型
收费全文 | 1000篇 |
免费 | 18篇 |
国内免费 | 8篇 |
专业分类
测绘学 | 138篇 |
大气科学 | 62篇 |
地球物理 | 168篇 |
地质学 | 394篇 |
海洋学 | 45篇 |
天文学 | 177篇 |
综合类 | 12篇 |
自然地理 | 30篇 |
出版年
2022年 | 20篇 |
2021年 | 22篇 |
2020年 | 14篇 |
2019年 | 24篇 |
2018年 | 51篇 |
2017年 | 42篇 |
2016年 | 64篇 |
2015年 | 38篇 |
2014年 | 47篇 |
2013年 | 79篇 |
2012年 | 49篇 |
2011年 | 34篇 |
2010年 | 45篇 |
2009年 | 33篇 |
2008年 | 31篇 |
2007年 | 30篇 |
2006年 | 22篇 |
2005年 | 19篇 |
2004年 | 18篇 |
2003年 | 10篇 |
2002年 | 5篇 |
2001年 | 13篇 |
2000年 | 28篇 |
1999年 | 14篇 |
1998年 | 14篇 |
1997年 | 3篇 |
1996年 | 12篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 13篇 |
1992年 | 14篇 |
1991年 | 25篇 |
1990年 | 9篇 |
1989年 | 12篇 |
1988年 | 10篇 |
1987年 | 19篇 |
1986年 | 12篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1983年 | 16篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 10篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1976年 | 10篇 |
1974年 | 6篇 |
1973年 | 4篇 |
1966年 | 4篇 |
排序方式: 共有1026条查询结果,搜索用时 31 毫秒
941.
Chandra S Rai Shiv K Sharma David W Muenow Dean W Matson Charles D Byers 《Geochimica et cosmochimica acta》1983,47(5):953-958
The temperature dependence of carbon dioxide solubility in glasses of diopside composition, quenched from 20 kbar, has been investigated using a combination of high-temperature mass spectrometry and Raman spectroscopy.CO2-charged diopside glasses were synthesized in a piston-cylinder apparatus. Because of diffusion of hydrogen through the platinum capsules, significant amounts of H2O, CH4 and CO were detected along with CO: in the diopside glasses. All three carbon species show a bimodal release pattern in the mass pyrograms. The CO2 solubility shows a linear and negative temperature dependence. We do not observe any maxima in the solubility curve as was reported previously (Mysen and virgo, 1980a).None of the additional bands observed in Raman spectra of CO2-charged diopside glasses compared to those in the spectrum of diopside glass can be assigned to molecular CO2. These bands are caused by CO?23 ions and indicate that the physical solubility of molecular carbon dioxide is negligible. The bimodal release pattern observed for CO2 in the mass pyrograms, is consistent with the Raman data which strongly suggests that CO?23 ions are present in at least two distinct sites in the glass. 相似文献
942.
943.
Forecasts of runoff volumes are required in order to maximize the utility of water-supply sources. In remote areas where hydrologic and land-use data are sparse, forecast models are needed; such models should be conceptually rational so they can be transferred to remote watersheds where data are sparse. A series of models were calibrated for a large watershed in India. A spatially-distributed seasonally-varying model having a structure similar to the rational method was found to provide precise, unbiased estimates of 10-day streamflow volumes. The model was tested on a watershed that was not used for calibration, with the results indicating a high correlation between the observed and measured streamflow. Thus, the model should provide good estimates of streamflow volumes on other ungaged watersheds. 相似文献
944.
ABSTRACT Use of granular pile as a ground improvement technique in case of soft soils is one of the reliable and economic options. Analysis of a partially stiffened group of granular floating piles has been numerically assessed and presented here. Partial stiffening simply means that instead of using conventional material for making the granular pile (GP) in its full length, top region is replaced partially by some suitable material, having better mechanical properties, i.e. higher deformation modulus. Various normalised parameters like settlement influence factor for top of GP, settlement interaction factor, settlement reduction factor, percentage load shared by the base and shear stress distribution along the length of the granular pile are evaluated. The settlement influence factor for top of GP is found to decrease with the increase in the values of the stiffening parameters. The interfacial shear stresses get redistributed along the length of the granular pile. 相似文献
945.
A new scheme is put forward based on the shape function concept of finite element approximation to compute regional gravity
anomaly. The uniqueness of this approach is that excepting eight (or twelve) discrete gravity measurements coinciding with
the eight (or twelve) nodes of a quadratic (or cubic) isoparametric element superimposing the map space, often very large,
no other observed gravity data are invoked to compute the regional. Tests on two Bouguer gravity fields, an oil prospect and
a rift valley confirmed better resolution by this approach. This technique is straight forward, uses simple mathematics to
be easily automated and yields repeatable results. 相似文献
946.
T. I. Harrold A. Sharma S. Sheather 《Stochastic Environmental Research and Risk Assessment (SERRA)》2001,15(4):310-324
Mutual information is a generalised measure of dependence between any two variables. It can be used to quantify non-linear
as well as linear dependence between any two variables. This makes mutual information an attractive alternative to the use
of the correlation coefficient, which can only quantify the linear dependence pattern. Mutual information is especially suited
for application to hydrological problems, because the dependence between any two hydrologic variables is seldom linear in
nature. Calculation of the mutual information score involves estimation of the marginal and joint probability density functions
of the two variables. This paper uses nonparametric kernel density estimation methods to estimate the probability density
functions. Accurate estimation of the mutual information score using kernel methods requires selection of appropriate smoothing
parameters (bandwidths) for use with the kernels. The aim of this paper is to obtain a practical method for bandwidth selection
for calculation of the mutual information score. In this paper, the lag-one dependence structures of several autocorrelated
time series are analysed using mutual information (note that this produces the lag-one auto-MI score, the analog of the lag-one
autocorrelation). Empirical trials are used to select appropriate bandwidths for a range of underlying autoregressive and
autoregressive-moving average models with normal or near-normal parent distributions. Expressions for reasonable bandwidth
choices under these conditions are proposed. 相似文献
947.
R Chaurasia D C Loshali S S Dhaliwal Minakshi P K Sharma M Kudrat A K Tiwari 《Journal of the Indian Society of Remote Sensing》1996,24(2):115-123
Remote sensing applications have been operationalised in most of the natural resources management themes and at present the trend is on integrated surveys to arrive at sustainable developmental packages. In accordance with the IMSD project, the Tehsil Talwandi Sabo in district Bathinda has been selected for integrated survey and resource management analysis. In the present study multidate remote sensing data has been analysed to map existing land use and temporal changes. The study in Talwandi Sabo suggests that land use pattern in the tehsil is not similar to that of general land use pattern prevailing in the State. The area under settlements show many fold increase while there is no increase in forest land. Sandy areas comprising sand dunes (levelled and unlevelled) require suitable management for proper ecosystem balance. 相似文献
948.
Ram Krishan Sharma 《Astrophysics and Space Science》1987,135(2):271-281
This paper deals with the stationary solutions of the planar restricted three-body problem when the more massive primary is a source of radiation and the smaller primary is an oblate spheroid with its equatorial plane coincident with the plane of motion. The collinear equilibria have conditional retrograde elliptical periodic orbits around them in the linear sense, while the triangular points have long- or short-periodic retrograde elliptical orbits for the mass parameter 0 < crit, the critical mass parameter, which decreases with the increase in oblateness and radiation force. Through special choice of initial conditions, retrograde elliptical periodic orbits exist for the case = crit, whose eccentricity increases with oblateness and decreases with radiation force for non-zero oblateness. 相似文献
949.
R R Navalgund V Jayaraman A S Kiran Kumar Tara Sharma Kurien Mathews K K Mohanty V K Dadhwal M B Potdar T P Singh R Ghosh V Tamilarasan T T Medhavy 《Journal of the Indian Society of Remote Sensing》1996,24(4):207-237
Although data available from various earth observation systems have been routinely used in many resource applications, however there have been gaps, and data needs of applications at different levels of details have not been met. There is a growing demand for availability of data at higher repetivity, at higher spatial resolution, in more and narrower spectral bands etc. Some of the thrust areas of applications particularly in the Indian context are;
- Management of natural resources to ensure sustainable increase in agricultural production,
- Study the state of the environment, its monitoring and assessment of the impact of. various development actions on the environment,
- Updating and generation of large scale topographical maps.
- Exploration/exploitation of marine and mineral resources and
- Operational meteorology and studying various land and oceanic processes to understand/predict global climate changes.
- Moderate spatial resolution (l50-300m), high repetivity (2 Days), minimum set of spectral bands (VIS, NIR, MIR. TIR) full coverage.
- Moderate to high spatial resolution (20-40m), high repetivity (4-6 Days), spectral bands (VIS, MR, MIR, TIR) full coverage.
- High spatial resolution (5-10m) muitispectral data with provision for selecting specific narrow bands (VIS, N1R. MIR), viewing from different angles.
- Synthetic aperture radar operating in at least two frequencies (C, X, Ku), two incidence angles/polarizations, moderate to high spatial resolution (20-40m), high repetivity (4-6 Days).
- Very high spatial resolution (1-2m) data in panchromatic band to provide terrain details at cadastral level (1:10,000).
- Stereo capability (1-2m height resolution) to help planning/execution of development plans.
- Moderate resolution sensor operating in VIS, NIR, MIR on a geostationary platform for observations at different sun angles necessary for the development of canopy reflectance inversion models.
- Diurnal (at least two i.e. pre-dawn and noon) temperature measurements of the earth surface.
- Ocean colour monitor with daily coverage.
- Multi-frequency microwave radiometer, scatterometer. altimeter, atmospheric sounder, etc.
950.
P. Vallabh Sharma 《Pure and Applied Geophysics》1966,65(1):48-53
Summary A simple method is designed for programming the gravity and magnetic calculations of a right circular cylinder (vertical or horizontal) by treating it as a combination of thin rectangular slabs. It takes only a few seconds to compute a profile of each kind and the accuracy is comparable to that obtained by using exact expressions (involving complete elliptic integrals) instead. The method is also applicable to cylindrical bodies of arbitrary cross-section and could as well be used for rapid computation of derivatives of gravity and magnetic anomalies. 相似文献