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71.
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
72.
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
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75.
Sanjay K. Srivastava Sameer Saran Rolf A. de By V. K. Dadhwal 《International journal of geographical information science》2014,28(3):427-454
Innumerable forest fire spread models exist for taking a decision, but far less focus is on the real causative factors which initiate/ignite fire in an area. It has been observed that the majority of the forest fires in India are initiated due to anthropogenic factors. In this study, we develop a geo-information system approach for management of forest fire in Mudumalai Wildlife Sanctuary, Tamil Nadu, India, with the objective to develop a forest fire likelihood model, integrating GIS and knowledge-based approach for predicting fire-sensitive initiation areas considering major causative and anti-causative factors. Amongst the various causative factors investigated, it was found that wildlife-dependent factor (antler collection and poaching) contributed significantly to fire occurrence followed by management-dependent factors (uncontrolled tourism and grazing), with much less influence of demographic factors. Similarly, anti-causative factor (stationing of anti-poaching/ fire camps) was considered as quite significant.
The likelihood model so developed, envisaging various factors and flammability, accounted for different scenarios as a result of pair-wise comparison on an ordinal scale in a knowledge matrix. The inferential statistics computed indicated the robustness of the model and its insensitivity to moderate changes. It makes it possible for this forest fire likelihood model to predict and prevent a forest fire in an effective and scientific manner because it can assume forest fire likelihood in real time and present in proper time. 相似文献
76.
Winter fog over the Indo-Gangetic Plains: mapping and modelling using remote sensing and GIS 总被引:1,自引:1,他引:0
Arun K. Saraf Ajoy K. Bora Josodhir Das Vineeta Rawat Kanika Sharma Sanjay K. Jain 《Natural Hazards》2011,58(1):199-220
Almost every year in the winter months (December–February), the vast Indo-Gangetic Plain south of the Himalaya is affected
by dense fog. This fog is considered as radiational fog, and sometime it becomes smog (when it mixes with smoke). The typical
meteorological, topographic and increasing pollution conditions over the Indo-Gangetic Plain are perhaps the common contributing
factors for fog formation. In the present study, the North Indian fog has been successfully mapped and analysed using NOAA-AVHRR
satellite data. In the winter seasons of 2005–06, 2006–07 and 2007–08, the fog-affected area has been found to cover about
575,800 km2, 594,100 km2 and 478,000 km2, respectively. Less fog in 2007–08 may be the consequence of high fluctuations in the meteorological parameters like temperature,
relative humidity and wind speed as related to the prevailing synoptic regime for that season. The dissipation and migration
pattern of fog in the study area has also been interpreted on the basis of the analysis of both meteorological and satellite
data. Further analysis of the fog-affected area allowed identifying more fog-prone regions. Analysis of past fog-affected
days and corresponding meteorological conditions enabled us to identify favourable conditions for fog formation viz. air temperature
3–13°C, relative humidity >87%, wind speed <2 m/s and elevation <300 m. Based on the observations of past fog formation and
corresponding governing parameters, fog for few selected days could be predicted in hind-sight and later verified with NOAA
images. 相似文献
77.
78.
In this paper we present a class of solutions of Einstein's field equations describing two-fluid models of the universe in
a locally rotationally symmetric Bianchi type II space-time. In these models one fluid is the radiation distribution which
represents the cosmic microwave background and the other fluid is the perfect fluid representing the matter content of the
universe. It is found that both the fluids are comoving in the locally rotationally symmetric Bianchi type II space-time.
The behaviour of the radiation density, matter density, the ratio of the matter density to the radiation density and the pressure
has been discussed. A subclass of solutions is found to describe models of a spatially homogeneous and partially isotropic
universe evolving from a radiation dominated era to a pressure free matter dominated era.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
79.
For the GMRT, we calculate the expected signal from red-shifted HI emission at two frequency bands centered at 610 and 325 MHz. The study focuses on the visibility-visibility cross-correlations, proposed earlier as the optimal statistical estimator for detecting and analyzing this signal. These correlations directly probe the power spectrum of density fluctuations at the redshift where the radiation originated, and thereby provide a method for studying the large scale structures at large redshifts. We present detailed estimates of the correlations expected between the visibilities measured at different baselines and frequencies. Analytic fitting formulas representing the salient features of the expected signal are also provided. These will be useful in planning observations and deciding an optimal strategy for detecting this signal. 相似文献
80.
The temporal variation in intermediate-degree-mode frequencies is analysed using helioseismic data which cover the minimum to the maximum phase of the current solar cycle. To study the variation in detail, the measured frequency shifts of f and p modes are decomposed into two components, viz., oscillatory and non-oscillatory. The f-mode frequencies exhibit prominent oscillatory behavior in contrast to p modes where the oscillatory nature of the frequencies is not clearly seen. Also, the oscillatory part contributes significantly to the f-mode frequencies while p-mode frequencies have maximum contribution from the non-oscillatory part. The amplitude of both oscillatory and non-oscillatory parts is found to be a function of frequency. The non-oscillatory part is observed to have a strong correlation with solar activity. 相似文献