首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   153篇
  免费   10篇
  国内免费   1篇
测绘学   3篇
大气科学   41篇
地球物理   33篇
地质学   48篇
海洋学   12篇
天文学   10篇
综合类   1篇
自然地理   16篇
  2024年   1篇
  2023年   2篇
  2022年   2篇
  2021年   2篇
  2020年   3篇
  2019年   4篇
  2018年   11篇
  2017年   5篇
  2016年   11篇
  2015年   5篇
  2014年   16篇
  2013年   17篇
  2012年   9篇
  2011年   9篇
  2010年   12篇
  2009年   6篇
  2008年   7篇
  2007年   7篇
  2006年   7篇
  2005年   1篇
  2004年   2篇
  2003年   3篇
  2002年   4篇
  1999年   2篇
  1998年   4篇
  1997年   3篇
  1996年   2篇
  1995年   1篇
  1994年   1篇
  1989年   1篇
  1988年   1篇
  1987年   1篇
  1978年   1篇
  1973年   1篇
排序方式: 共有164条查询结果,搜索用时 15 毫秒
81.
The deduction of a regularly spaced gravity anomaly grid from scattered survey data is studied, addressing mainly two aspects: reduction of gravity to anomalies and subsequent interpolation by various methods. The problem is illustrated in a heterogeneous study area and contrasting test areas including mountains, low terrains, and a marine area. Provided with realistic error estimates, Least Squares Collocation interpolation of Residual Terrain Model anomalies yields the highest quality gravity grid. In most cases, the Bouguer reduction and other interpolation methods tested are equally viable. However, spline-based interpolation should be avoided in marine areas with trackwise survey data.  相似文献   
82.
Tropical cyclone hazard assessment using model-based track simulation   总被引:3,自引:1,他引:2  
A method is introduced for assessing the probabilities and intensities of tropical cyclones at landfall and applied to data from the North Atlantic. First, a recently developed model for the basin-wide Monte-Carlo simulation of tropical cyclone tracks is enhanced and transferred to the North Atlantic basin. Subsequently, a large number of synthetic tracks is generated by means of an implementation of this model. This synthetic data is far more comprehensive than the available historical data, while exhibiting the same basic characteristics. It, thus, creates a more sound basis for assessing landfall probabilities than previously available, especially in areas with a low historical landfall frequency.  相似文献   
83.
We have developed a lidar to study the temperature structure of the nighttime mesopause region over the Arecibo Observatory (18.35°N, 66.75°W) by measuring the lineshape of the fluorescence spectrum of atomic potassium that is deposited in the mesosphere and lower thermosphere (MLT) by meteors. To demonstrate how the potassium lidar can enhance MLT studies at Arecibo, we show recent results for: (1) comparisons with airglow temperature measurements; (2) simultaneous operations with stratospheric and mesospheric temperature profiling by Rayleigh lidar; (3) simultaneous observations of K, Ca+, and E-region electron density profiles; and (4) occurrences of sporadic K layers, and relationships to sporadic E layers.  相似文献   
84.
夏季自然水体与大气界面间气态总汞的交换通量   总被引:10,自引:0,他引:10  
利用动力学通量箱法与高时间分辨率大气测汞仪的联用技术, 在瑞典西南的Kristineberg海洋观测站(KMRS)和Knobesholm的Hovgårdsån河分别测定了夏季海水和河水表面与大气间汞的交换通量. 在夏季, 河水和海水都是大气汞的源. 河水和海水表面与大气间汞的交换通量在夏季具有一致的昼夜变化规律, 白天由水体向大气排汞且在正午达到最大值; 夜间排汞量相对较小且有时会出现大气汞向水体沉降. 河水与大气间汞的交换通量与光照强度呈线性正相关关系, 与大气相对湿度呈线性负相关性, 同时还与水体温度存在指数相关性. 海水与大气间汞交换通量只与光照强度存在良好的线性正相关关系. 水体中溶解态气汞的过饱和是水体汞向大气释放的驱动力.  相似文献   
85.
In search for a suitable and fast analytical method for assessing kinds of activated carbon for water purification there were carried out investigations with hydrogen peroxide. According to their catalytic activity, the various kinds of activated carbon are capable of decomposing hydrogen peroxide to different degrees and at different rates. The released oxygen can be determined volumetrically. The results of investigation obtained on always fresh carbon samples with acid and basic groups were discussed on the basis of the velocity constants of the oxygen development. An assessment of quality would be possible, in principle, but the surface characteristic of the kinds of carbon is considerably superimposed by influences of morphology, so that applying this method is advised against.  相似文献   
86.
We present two Lagrange multiplier-based domain decomposition methods for solving iteratively a non-linear sedimentary basin problem. Both methods are Uzawa-type algorithms derived from saddle point equations of Lagrangian and augmented Lagrangian functionals. Numerical experiments show that both methods are scalable with respect to the mesh size.  相似文献   
87.
Geoid and quasigeoid modelling from gravity anomalies by the method of least squares modification of Stokes’s formula with additive corrections is adapted for the usage with gravity disturbances and Hotine’s formula. The biased, unbiased and optimum versions of least squares modification are considered. Equations are presented for the four additive corrections that account for the combined (direct plus indirect) effect of downward continuation (DWC), topographic, atmospheric and ellipsoidal corrections in geoid or quasigeoid modelling. The geoid or quasigeoid modelling scheme by the least squares modified Hotine formula is numerically verified, analysed and compared to the Stokes counterpart in a heterogeneous study area. The resulting geoid models and the additive corrections computed both for use with Stokes’s or Hotine’s formula differ most in high topography areas. Over the study area (reaching almost 2 km in altitude), the approximate geoid models (before the additive corrections) differ by 7 mm on average with a 3 mm standard deviation (SD) and a maximum of 1.3 cm. The additive corrections, out of which only the DWC correction has a numerically significant difference, improve the agreement between respective geoid or quasigeoid models to an average difference of 5 mm with a 1 mm SD and a maximum of 8 mm.  相似文献   
88.
Lower Cretaceous early syn‐rift facies along the eastern flank of the Eastern Cordillera of Colombia, their provenance, and structural context, reveal the complex interactions between Cretaceous extension, spatio‐temporal trends in associated sedimentation, and subsequent inversion of the Cretaceous Guatiquía paleo‐rift. South of 4°30′N lat, early syn‐rift alluvial sequences in former extensional footwall areas were contemporaneous with fan‐delta deposits in shallow marine environments in adjacent hanging‐wall areas. In general, footwall erosion was more pronounced in the southern part of the paleorift. In contrast, early syn‐rift sequences in former footwall areas in the northern rift sectors mainly comprise shallow marine supratidal sabkha to intertidal strata, whereas hanging‐wall units display rapid transitions to open‐sea shales. In comparison with the southern paleo‐rift sector, fan‐delta deposits in the north are scarce, and provenance suggests negligible footwall erosion. The southern graben segment had longer, and less numerous normal faults, whereas the northern graben segment was characterized by shorter, rectilinear faults. To the east, the graben system was bounded by major basin‐margin faults with protracted activity and greater throw as compared with intrabasinal faults to the west. Intrabasinal structures grew through segment linkage and probably interacted kinematically with basin‐margin faults. Basin‐margin faults constitute a coherent fault system that was conditioned by pre‐existing basement fabrics. Structural mapping, analysis of present‐day topography, and balanced cross sections indicate that positive inversion of extensional structures was focused along basin‐bounding faults, whereas intrabasinal faults remained unaffected and were passively transported by motion along the basin‐bounding faults. Thus, zones of maximum subsidence in extension accommodated maximum elevation in contraction, and former topographic highs remained as elevated areas. This documents the role of basin‐bounding faults as multiphased, long‐lived features conditioned by basement discontinuities. Inversion of basin‐bounding faults was more efficient in the southern than in the northern graben segment, possibly documenting the inheritance and pivotal role of fault‐displacement gradients. Our observations highlight similarities between inversion features in orogenic belts and intra‐plate basins, emphasizing the importance of the observed phenomena as predictive tools in the spatiotemporal analysis of inversion histories in orogens, as well as in hydrocarbon and mineral deposits exploration.  相似文献   
89.
Numerical simulations of unsaturated solute transport from point sources were carried out using HYDRUS-1D. Three different soil types cropped with spring wheat were considered at three different locations in Sweden: Malmö, Norrköping and Petisträsk. Two types of rainfall data were used, point-scale raingauge measurements and a gauge-adjusted weather radar product at four spatial resolutions, 2 × 2, 6 × 6, 10 × 10 and 14 × 14 km2. The results showed that differences in the mean solute transport depths were small and not significant, with the exception of Petisträsk. Maximum transport depths were in most cases significantly larger using raingauge data compared to radar data. The results showed that using areal-averaged rainfall input will give solute transport estimations close to those using point-measured data. This shows the great potential in using radar-measured rainfall data in small-scale hydrological applications.  相似文献   
90.
The Tissint meteorite fell on July 18, 2011 in Morocco and was quickly recovered, allowing the investigation of a new unaltered sample from Mars. We report new high‐field strength and highly siderophile element (HSE) data, Sr‐Nd‐Hf‐W‐Os isotope analyses, and data for cosmogenic nuclides in order to examine the history of the Tissint meteorite, from its source composition and crystallization to its irradiation history. We present high‐field strength element compositions that are typical for depleted Martian basalts (0.174 ppm Nb, 17.4 ppm Zr, 0.7352 ppm Hf, and 0.0444 ppm W), and, together with an extended literature data set for shergottites, help to reevaluate Mars’ tectonic evolution in comparison to that of the early Earth. HSE contents (0.07 ppb Re, 0.92 ppb Os, 2.55 ppb Ir, and 7.87 ppb Pt) vary significantly in comparison to literature data, reflecting significant sample inhomogeneity. Isotope data for Os and W (187Os/188Os = 0.1289 ± 15 and an ε182W = +1.41 ± 0.46) are both indistinguishable from literature data. An internal Lu‐Hf isochron for Tissint defines a crystallization age of 665 ± 74 Ma. Considering only Sm‐Nd and Lu‐Hf chronometry, we obtain, using our and literature values, a best estimate for the age of Tissint of 582 ± 18 Ma (MSWD = 3.2). Cosmogenic radionuclides analyzed in the Tissint meteorite are typical for a recent fall. Tissint's pre‐atmospheric radius was estimated to be 22 ± 2 cm, resulting in an estimated total mass of 130 ± 40 kg. Our cosmic‐ray exposure age of 0.9 ± 0.2 Ma is consistent with earlier estimations and exposure ages for other shergottites in general.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号