全文获取类型
收费全文 | 253篇 |
免费 | 4篇 |
国内免费 | 3篇 |
专业分类
测绘学 | 9篇 |
大气科学 | 8篇 |
地球物理 | 35篇 |
地质学 | 122篇 |
海洋学 | 7篇 |
天文学 | 69篇 |
综合类 | 1篇 |
自然地理 | 9篇 |
出版年
2022年 | 2篇 |
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 4篇 |
2018年 | 12篇 |
2017年 | 11篇 |
2016年 | 9篇 |
2015年 | 5篇 |
2014年 | 16篇 |
2013年 | 17篇 |
2012年 | 13篇 |
2011年 | 12篇 |
2010年 | 8篇 |
2009年 | 11篇 |
2008年 | 7篇 |
2007年 | 9篇 |
2006年 | 2篇 |
2005年 | 4篇 |
2004年 | 7篇 |
2003年 | 4篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 8篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1971年 | 5篇 |
1970年 | 3篇 |
1967年 | 1篇 |
1966年 | 2篇 |
1964年 | 2篇 |
1963年 | 2篇 |
1962年 | 2篇 |
1929年 | 1篇 |
排序方式: 共有260条查询结果,搜索用时 218 毫秒
111.
Timothy Paulsen Chad Deering Jakub Sliwinski Snehamoy Chatterjee Olivier Bachmann Marcel Guillong 《地学学报》2021,33(1):12-20
Orogenic crustal thickening leads to increased continental elevation and runoff into the oceans, but there are fundamental uncertainties in the temporal patterns of thickening through Earth history. U‐Pb age and trace element data in detrital zircons from Antarctica are consistent with recent global analyses suggesting two dominant peaks in average crustal thickness from ~2.6 to 2.0 Ga and ~0.8 to 0.5 Ga. Shifts in marine carbonate 87Sr/86Sr ratios show two primary peaks that post‐date these crustal thickness peaks, suggesting significant weathering and erosion of global continental relief. Both episodes correlate well with zircon trace element and isotope proxies indicating enhanced crustal and fluid input into subduction zone magmas. Increased crustal thickness correlates with increased passive margin abundance and overlaps with snowball Earth glaciations and atmospheric oxygenation, suggesting a causal link between continental rift‐drift phases and major transitions in Earth's atmospheric and oceanic evolution. 相似文献
112.
Ansar Khan Soumendu Chatterjee Hashem Akbari Saad Saleem Bhatti Apurba Dinda Chandana Mitra 《国际地球制图》2019,34(5):504-527
The extraction of urban built-up areas is an important aspect of urban planning and understanding the complex drivers and biophysical mechanism of urban climate processes. However, built-up area extraction using Landsat data is a challenging task due to spatio-temporal dynamics and spatially intermixed nature of Land Use and Land Cover (LULC) in the cities of the developing countries, particularly in tropics. In the light of advantages and drawbacks of the Normalized Difference Built-up Index (NDBI) and Built-up Area Extraction Method (BAEM), a new and simple method i.e. Step-wise Land-class Elimination Approach (SLEA) is proposed for rapid and accurate mapping of urban built-up areas without depending exclusively on the band specific normalized indices, in order to pursue a more generalized approach. It combines the use of a single band layer, Normalized Difference Vegetation Index (NDVI) image and another binary image obtained through Logit model. Based on the spectral designation of the satellite image in use, a particular band is chosen for identification of water pixels. The Double-window Flexible Pace Search (DFPS) approach is employed for finding the optimum threshold value that segments the selected band image into water and non-water categories. The water pixels are then eliminated from the original image. The vegetation pixels are similarly identified using the NDVI image and eliminated. The residual pixels left after elimination of water and vegetation categories belong either to the built-up areas or to bare land categories. Logit model is used for separation of the built-up areas from bare lands. The effectiveness of this method was tested through the mapping of built-up areas of the Kolkata Metropolitan Area (KMA), India from Thematic Mapper (TM) images of 2000, 2005 and 2010, and Operational Land Imager (OLI) image of 2015. Results of the proposed SLEA were 95.33% accurate on the whole, while those derived by the NDBI and BAEM approaches returned an overall accuracy of 83.67% and 89.33%, respectively. Comparisons of the results obtained using this method with those obtained from NDBI and BAEM approaches demonstrate that the proposed approach is quite reliable. The SLEA generates new patterns of evidence and hypotheses for built-up areas extraction research, providing an integral link with statistical science and encouraging trans-disciplinary collaborations to build robust knowledge and problem solving capacity in urban areas. It also brings landscape architecture, urban and regional planning, landscape and ecological engineering, and other practice-oriented fields to bear together in processes for identifying problems and analyzing, synthesizng, and evaluating desirable alternatives for urban change. This method produced very accurate results in a more efficient manner compared to the earlier built-up area extraction approaches for the landscape and urban planning. 相似文献
113.
Nilanjan Chatterjee Kirsten Nicolaysen 《Contributions to Mineralogy and Petrology》2012,163(5):789-806
The Kerguelen Plateau is a submarine, Cretaceous Large Igneous Province in the southern Indian Ocean. Drilling on Elan Bank,
a western salient of the Kerguelen Plateau, yielded a ~26 m section of fluvial conglomerate intercalated with basalt. Chemical
dating of monazite within garnet and matrix monazite in metapelitic clasts from the conglomerate indicates that high-grade
metamorphism of the pelitic protolith occurred between 785 ± 12 and 694 ± 18 Ma. A calculated P–T pseudosection indicates
that the observed core-to-inner rim compositional zoning in garnet is consistent with P/T decrease from 10.2 kb/760°C to 6.2 kb/560°C.
In an Early Cretaceous paleogeographic reconstruction, the Elan Bank drill site is located on a SSW continuation of the Eastern
Indian Tectonic Zone (EITZ), a 876–784 Ma, NNE–SSW metamorphic belt with sinistral shear zones in eastern India. The retrograde
P–T path of the Elan Bank metapelitic clast overlaps with that of the EITZ metapelite, and the Elan Bank monazite chemical
dates and previously determined 824–675 Ma U–Pb isotope monazite dates by the TIMS method are remarkably similar to the monazite
chemical dates from the EITZ metapelites and high-grade metamorphic rocks from the eastern margin of the Eastern Ghats Belt.
Based on the demonstrable affinity of metamorphic, geochronologic, and spatial data, this study concludes that the EITZ was
likely a continuous, ~1,800–km-long tectono-metamorphic belt in the Rodinia supercontinent stretching from eastern India through
the Eastern Ghats to the basement of Elan Bank and probably to the Rayner Complex of East Antarctica. 相似文献
114.
Sudip Jyoti Sahu Bibhash Nath Sharmi Roy Biswapati Mandal Debashis Chatterjee 《Environmental Earth Sciences》2012,65(3):813-821
Groundwater contaminated with arsenic (As), when extensively used for irrigation, causes potentially long-term detrimental
effects to surface soils. Such contamination can also directly affect human health when irrigated crops, such as rice, vegetable
and fruits, are used for human consumption. Therefore, an understanding of the leaching behavior of As in surface soils is
of high importance, because such behavior may increase the bioavailability of As in the soil horizon. In this study, we have
investigated the role of phosphate ions in leaching and bioavailability of As in the soil horizon, where drinking groundwater
contains elevated levels of As (≥50 μg/L). Soil and groundwater samples were characterized in the laboratory and measured
for physical and chemical constituents. The soils are generally neutral to slightly alkaline in character (pH range 7.5–8.1)
with low to moderate levels of free Fe2O3, Al2O3, CaCO3, organic carbon, and clay content. The measured electrical conductivity (mean 599 μS/cm) of the soils demonstrates their
non-saline nature. The Eh values (range −37 to −151 mV) of the groundwater indicate anoxic condition with low to moderate
levels of bicarbonate (range 100–630 mg/L) and phosphate (range 0.002–4.0 mg/L). The arsenic content (range 50–690 μg/L; mean
321 μg/L) in groundwater has exceeded both WHO recommended guideline values (10 μg/L) and the National safe drinking water
limit (50 μg/L). Regression analyses demonstrate that the bioavailability of As in the soil horizon is mainly controlled by
the composition of free Fe2O3 and CaCO3 content of the soils. However, application of P could increase bioavailability of As in the soil horizon and become available
to plants for uptake. 相似文献
115.
116.
Linda T. Elkins‐Tanton Nilanjan Chatterjee Timothy L. Grove 《Meteoritics & planetary science》2003,38(4):515-527
Abstract— Phase equilibrium experiments on the most magnesian Apollo 15C green picritic glass composition indicate a multiple saturation point with olivine and orthopyroxene at 1520°C and 1.3 GPa (about 260 km depth in the moon). This composition has the highest Mg# of any lunar picritic glass and the shallowest multiple saturation point. Experiments on an Apollo 15A composition indicate a multiple saturation point with olivine and orthopyroxene at 1520°C and 2.2 GPa (about 440 km depth in the moon). The importance of the distinctive compositional trends of the Apollo 15 groups A, B, and C picritic glasses merits the reanalysis of NASA slide 15426,72 with modern electron microprobe techniques. We confirm the compositional trends reported by Delano (1979, 1986) in the major element oxides SiO2, TiO2, Al2O3, Cr2O3, FeO, MnO, MgO, and CaO, and we also obtained data for the trace elements P2O5, K2O, Na2O, NiO, S, Cu, Cl, Zn, and F. Petrogenetic modeling demonstrates that the Apollo 15 A‐B‐C glass trends could not have been formed by fractional crystallization or any continuous assimilation/fractional crystallization (AFC) process. The B and C glass compositional trends could not have been formed by batch or incremental melting of an olivine + orthopyroxene source or any other homogeneous source, though the A glasses may have been formed by congruent melting over a small pressure range at depth. The B compositional trend is well modeled by starting with an intermediate A composition and assimilating a shallower, melted cumulate, and the C compositional trend is well modeled by a second assimilation event. The assimilation process envisioned is one in which heat and mass transfer were separated in space and time. In an initial intrusive event, a picritic magma crystallized and provided heat to melt magma ocean cumulates. In a later replenishment event, the picritic magma incrementally mixed with the melted cumulate (creating the compositional trends in the green glass data set), ascended to the lunar surface, and erupted as a fire fountain. A barometer created from multiple saturation points provides a depth estimate of other glasses in the A‐B‐C trend and of the depths of assimilation. This barometer demonstrates that the Apollo 15 A‐B‐C trend originated over a depth range of ?460 km to ?260 km within the moon. 相似文献
117.
Uday Narayan Ghosh Pankaj Kumar Mandal Prasanta Chatterjee 《Astrophysics and Space Science》2014,349(2):765-771
Cylindrical Zakharov–Kuznestov equation for ion-acoustic waves comprising of ions and electrons featuring non-extensive distribution are derived from the fluid equations through reductive perturbation technique. System of first order ordinary differential equations is obtained from Zakharov–Kuznestov equation through dynamical system approach and ultimately it is solved using numerical method. It is found that the electron to positron ratio parameter and the non-extensive distributed parameter due to electron play crucial role on the solution. 相似文献
118.
Kaushik Roy Tapas Kumar Maji Malay Kumar Ghorui Prasanta Chatterjee Rajkumar Roychoudhury 《Astrophysics and Space Science》2014,352(1):151-157
Theoretically the propagation of two ion acoustic soliton interaction in a three component collisionless unmagnetized plasma which consists of electrons, positrons and cold ions, has been investigated here by employing reductive perturbation technique. In this study, q distributed electrons and Maxwell-Boltzmann distributed positrons are considered and Korteweged-de Vries (KdV) equation is derived. The KdV equation is solved to get two soliton solution by using Hirota bilinear method. The effects of the q distributed electrons on the profiles of two soliton structures and the corresponding phase shifts are investigated. It is observed that both the nonextensive parameter (q) and the ratio of positrons density and electron density (p=n p0/n e0), play a significant role in the formation and existence of two soliton and also in the nature of their phase shifts. 相似文献
119.
120.
By introducing an asymmetry between the two hemispheres, we study whether the solar dynamo solutions in the two hemispheres
remain coupled with each other. Our calculations are based on the solar dynamo code SURYA, which incorporates the helioseismically-determined
solar-rotation profile, a Babcock–Leighton α effect concentrated near the surface, and a meridional circulation. When the magnetic coupling between the hemispheres is
enhanced by either increasing the diffusion or introducing an α effect distributed throughout the convection zone, we find that the solutions in the two hemispheres evolve together with
a single period even when we make the meridional circulation or the α effect different in the two hemispheres. On the other hand, when the hemispheric coupling is weaker for other values of parameters,
an asymmetry between the hemispheres can make solutions in the two hemispheres evolve independently with different periods. 相似文献