全文获取类型
收费全文 | 705篇 |
免费 | 20篇 |
国内免费 | 10篇 |
专业分类
测绘学 | 68篇 |
大气科学 | 48篇 |
地球物理 | 202篇 |
地质学 | 261篇 |
海洋学 | 34篇 |
天文学 | 102篇 |
综合类 | 10篇 |
自然地理 | 10篇 |
出版年
2022年 | 12篇 |
2021年 | 11篇 |
2020年 | 9篇 |
2019年 | 15篇 |
2018年 | 48篇 |
2017年 | 42篇 |
2016年 | 33篇 |
2015年 | 30篇 |
2014年 | 40篇 |
2013年 | 56篇 |
2012年 | 34篇 |
2011年 | 29篇 |
2010年 | 25篇 |
2009年 | 35篇 |
2008年 | 33篇 |
2007年 | 30篇 |
2006年 | 25篇 |
2005年 | 20篇 |
2004年 | 13篇 |
2003年 | 16篇 |
2002年 | 13篇 |
2001年 | 10篇 |
2000年 | 4篇 |
1999年 | 9篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 11篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 9篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1972年 | 2篇 |
1970年 | 3篇 |
排序方式: 共有735条查询结果,搜索用时 15 毫秒
201.
Anil V. Kulkarni Sunil Dhar B. P. Rathore Babu Govindha Raj K. Rajeev Kalia 《Journal of the Indian Society of Remote Sensing》2006,34(1):39-46
Himalayas possess one of the largest resources of snow, ice and glaciers that act as a huge freshwater reservoir. Monitoring
the glaciers is important to assess the overall reservoir health of the Himalayas. Samudra Tapu is one of the largest glaciers
in Chandra basin of district Lahaul and Spiti, Himachal Pradesh. Based on the field investigations and the remote sensing
techniques. features such as accumulation area, ablation area snowline/equilibrium line, moraine-dammed lakes and permanent
snowfields were mapped. The glacial terminus was identified using moraine-dammed lake, as lake is located at down streamside
of the terminus. The total recession of glacier during the period of 38 years (1962–2000) is about 742 m with an average rate
of 19.5 m/yr. In addition, glacial extent is reduced from 73 to 65 km2 between 1962 and 2000. suggesting overall deglaciation of 11%. During field investigation. three stages of glaciation using
terminal moraine were identified. These moraines were mapped by merging LISS-II1 and PAN data. At the peak of glaciation.
the glacial terminus was extended 3.18 km downstream of terminus position in year 2000. Total area during peak of glaciation
period has been observed to be 77.67 km2, which is 12.67 km2 higher than the present glacier extent. 相似文献
202.
The STARE system (Scandinavian Twin Auroral Radar Experiment) provides estimates of electron drift velocities, and hence also of the electric field in the high-latitude E-region ionosphere between 65 and 70 degrees latitude. The occurrence of drift velocities larger than about 400 m/s (equivalent to an electric field of 20 mV/m) have been correlated with the magnitude of the Interplanetary Magnetic Field (IMF) components Bz and By at all local times. Observation days have been considered during which both southward (Bz<0) and northward (Bz>0) IMF occurred. The occurrence of electric fields larger than 20 mV/m increases with increases in Bz magnitudes when Bz<0. It is found that the effects of southward IMF continue for some time following the northward turnings of the IMF. In order to eliminate such residual effects for Bz<0, we have, in the second part of the study, considered those days which were characterized by a pure northward IMF. The occurrence is considerably lower during times when Bz>0, than during those when Bz is negative. These results are related to the expansion and contraction of the auroral oval. The different percentage occurrences of large electric field for By>0 and By<0 components of the IMF during times when Bz>0, clearly display a dawn-dusk asymmetry of plasma flow in the ionosphere. The effects of the time-varying solar-wind speed, density, IMF fluctuations, and magnetospheric substorms on the occurrence of auroral-backscatter observations are also discussed. 相似文献
203.
Anil Kumar Y J Bhaskar Rao V M Padma Kumari A M Dayal K Gopalan 《Journal of Earth System Science》1988,97(1):107-114
Palaeomagnetic, geochemical and geochronological studies have been conducted on a set of dolerite dykes intruding the Peninsular
gneisses near Huliyurdurga town, Karnataka, as a reconnaissance survey indicated a Cretaceous age for them. The dykes are
mainly tholeiitic in composition with their 87Sr/86Sr ratios tightly clustered around 0·7045. Their palaeomagnetic data (D
m
=329°,I
m
=−55°) and the corresponding palaeopole coordinates (λ
p
= 34°S,L
p
=108°E) are strikingly close to those of the Deccan Traps to the north. Whole rock K-Ar ages of these dykes ranging between
69 and 84 Ma are also similar to the range of K-Ar ages of the Deccan basalts. The chemical, palaeomagnetic and temporal coherence
between the dykes and the Deccan basalts indicate that they may indeed be tectonically related events. 相似文献
204.
An effective procedure is summarized without derivation for estimating the maximum response of a class of torsionally-coupled, multi-storey buildings due to earthquake ground motion characterized by response spectra. The analysis procedure is shown to be efficient and to provide insight into torsional coupling effects because the maximum response of such a torsionally-coupled, N-storey building in its njth mode of vibration is determined exactly by analysing (i) the response in the jth vibration mode (j = 1,2, N) of the corresponding torsionally-uncoupled, N-storey system; and (ii) the response in the nth vibration mode (n = 1, 2 for a one-way symmetric plan) of an associated torsionally-coupled, one-storey system. It is also demonstrated that an earlier, simpler approach in which the total (considering all vibration modes) response of the building is determined from the total response of the two simpler systems is strictly valid only under restrictive conditions, which are identified, but the simpler approach leads to results that are accurate to a useful degree. 相似文献
205.
A. P. Subudhi N. D. Sharma Debajit Mishra 《Journal of the Indian Society of Remote Sensing》1989,17(3):85-99
Visual interpretation of Landsat Thematic Mapper data coupled with ground checking has been used to extract information for urban areas. The emphasis has been given on development of land use/land cover scheme and image interpretation keys for interpretation and delineation purposes using satellite remote sensing data. Lucknow city and its surroundings have been studied to evaluate the usefulness and potentiality of satellite data particularly Landsat Thematic Mapper for urban area studies. This study has demonstrated that remote sensing can provide a valuable tool for urban data acquisition. 相似文献
206.
Man has had to live with floods since the very inception of his existence. Fury of flood causes heavy damages to both life and property. Accurate flood inundation data is one of the essential requirements for effective management of flood problem. Remote Sensing methods are well suited for acquiring flood inundation data because of synoptic, repetitive coverage of the satellite data. This paper briefs on an attempt to map flood inundated areas in a part of Mahanadi river basin using remote sensing data. 相似文献
207.
The mechanical properties of particulate systems are studied from a micromechanics point of view. Two approaches, namely, computer simulation and micro-structural continuum modelling are used. The computer simulation method is used to study the uniformity of the strain field and effect of particle rotations. These results are then used to evaluate the applicability of the micro-structural continuum model. Potential applications of the micro-structural continuum model in the study of mechanical properties of soils are discussed. 相似文献
208.
Drought is a temporary, random and regional climatic phenomenon, originating due to lack of precipitation leading to water deficit and causing economic loss. Success in drought alleviation depends on how well droughts are defined and their severity quantified. A quantitative definition identifies the beginning, end, spatial extent and the severity of drought. Among the available indices, no single index is capable of fully describing all the physical characteristics of drought. Therefore, in most cases it is useful and necessary to consider several indices, examine their sensitivity and accuracy, and investigate for correlation among them. In this study, the geographical information system‐based Spatial and Time Series Information Modeling (SPATSIM) and Daily Water Resources Assessment Modeling (DWRAM) software were used for drought analysis on monthly and daily bases respectively and its spatial distribution in both dry and wet years. SPATSIM utilizes standardized precipitation index (SPI), effective drought index (EDI), deciles index and departure from long‐term mean and median; and DWRAM employs only EDI. The analysis of data from the Kalahandi and Nuapada districts of Orissa (India) revealed that (a) droughts in this region occurred with a frequency of once in every 3 to 4 years, (b) droughts occurred in the year when the ratio of annual rainfall to potential evapotranspiration (Pae/PET) was less than 0·6, (c) EDI better represented the droughts in the area than any other index; (d) all SPI, EDI and annual deviation from the mean showed a similar trend of drought severity. The comparison of all indices and results of analysis led to several useful and pragmatic inferences in understanding the drought attributes of the study area. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
209.
Cosmic-ray intensity data recorded with the ground-based neutron monitor at Deep River have been investigated taking into
account the associated interplanetary magnetic field and solar-wind plasma data during 1981 – 1994. A large number of days
having abnormally high or low amplitudes for five or more successive days as compared to the annual average amplitude of diurnal
anisotropy have been taken as high- or low-amplitude anisotropic wave-train events. The amplitude of the diurnal anisotropy
of these events is found to increase on days with a magnetic cloud as compared to the days prior to the event, and it is found
to decrease during the later period of the event as the cloud passes the Earth. The high-speed solar-wind streams do not play
any significant role in causing these types of events. However, corotating solar-wind streams produce significant deviations
in cosmic-ray intensity during high- and low-amplitude events. The interplanetary disturbances (magnetic clouds) are also
effective in producing cosmic-ray decreases. Hα solar flares have a good positive correlation with both the amplitude and
direction of the anisotropy for high-amplitude events, while the principal magnetic storms have a good positive correlation
with both amplitude and direction of the anisotropy for low-amplitude events. The source responsible for these unusual anisotropic
wave trains in cosmic rays has been proposed. 相似文献
210.
B. Mishra C.S. Saravanan A. Bhattacharya S. Goon S. Mahato H.J. Bernhardt 《Gondwana Research》2007,11(4):504-515
A combined fluid inclusion and mineral thermobarometric study in groups of synchronous inclusions in quartz within weakly foliated granites from the Chottanagpur Gneissic Complex, India, reveals super dense carbonic (CO2 with minor CH4 and H2O) inclusions and hypersaline (H2O–NaCl ± NaHCO3) inclusions, with halite- and nahcolite daughter phases. This study documents the highest density (1.115 g cm− 3) CO2 fluids ever reported in granites. Fluid isochores, constructed from CO2 (± CH4) and halite-bearing inclusions, coupled with two-feldspar thermometry constrain the minimum P–T at 8 kbar/ 750 °C for fluid entrapment in granites. By contrast, the carbonic inclusions in quartz from granite-hosted metapelite enclaves contain substantial CH4 (up to 30 mol%), and the entrapment pressure ( 4.3 kbar/600 °C) is considerably lower compared to those in the granites. By implication, the sillimanite-free granites were not derived from the metapelitic enclaves, and instead were formed by partial melting of fluid-heterogeneous lower crustal protoliths, with fluid entrapment at magmatic conditions. 相似文献