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   2096篇
  免费   129篇
  国内免费   12篇
测绘学   40篇
大气科学   180篇
地球物理   598篇
地质学   775篇
海洋学   261篇
天文学   250篇
综合类   12篇
自然地理   121篇
  2023年   8篇
  2022年   21篇
  2021年   51篇
  2020年   54篇
  2019年   34篇
  2018年   97篇
  2017年   83篇
  2016年   157篇
  2015年   110篇
  2014年   115篇
  2013年   141篇
  2012年   100篇
  2011年   135篇
  2010年   132篇
  2009年   132篇
  2008年   127篇
  2007年   74篇
  2006年   79篇
  2005年   60篇
  2004年   55篇
  2003年   56篇
  2002年   48篇
  2001年   32篇
  2000年   31篇
  1999年   30篇
  1998年   34篇
  1997年   19篇
  1996年   17篇
  1995年   21篇
  1994年   17篇
  1993年   9篇
  1992年   10篇
  1991年   15篇
  1990年   17篇
  1989年   11篇
  1988年   9篇
  1987年   10篇
  1986年   4篇
  1985年   3篇
  1984年   11篇
  1983年   7篇
  1982年   7篇
  1981年   5篇
  1978年   3篇
  1974年   6篇
  1973年   7篇
  1972年   3篇
  1957年   3篇
  1956年   3篇
  1954年   3篇
排序方式: 共有2237条查询结果,搜索用时 15 毫秒
101.
The Salar de Atacama Basin holds important information regarding the tectonic activity, sedimentary environments and their variations in northern Chile during Cretaceous times. About 4000 m of high‐resolution stratigraphic columns of the Tonel, Purilactis and Barros Arana Formations reveal braided fluvial and alluvial facies, typical of arid to semi‐arid environments, interrupted by scarce intervals with evaporitic, aeolian and lacustrine sedimentation, displaying an overall coarsening‐upward trend. Clast‐count and point‐count data evidence the progressive erosion from Mesozoic volcanic rocks to Palaeozoic basement granitoids and deposits located around the Cordillera de Domeyko area, which is indicative of an unroofing process. The palaeocurrent data show that the source area was located to the west. The U/Pb detrital zircon geochronological data give maximum depositional ages of 149 Ma for the base of the Tonel Formation (Agua Salada Member), and 107 Ma for its middle member (La Escalera Member); 79 Ma for the lower Purilactis Formation (Limón Verde Member), and 73 Ma for the Barros Arana Formation. The sources of these zircons were located mainly to the west, and comprised from the Coastal Cordillera to the Precordillera. The ages and pulses record the tectonic activity during the Peruvian Phase, which can be split into two large events; an early phase, around 107 Ma, showing uplift of the Coastal Cordillera area, and a late phase around 79 Ma indicating an eastward jump of the deformation front to the Cordillera de Domeyko area. The lack of internal deformation and the thicknesses measured suggest that deposition of the units occurred in the foredeep zone of an eastward‐verging basin. This sedimentation would have ended with the K‐T phase, recognized in most of northern Chile.  相似文献   
102.
103.
104.
105.
106.
107.
108.
Hydrocarbon reservoir modelling and characterisation is a challenging subject within the oil and gas industry due to the lack of well data and the natural heterogeneities of the Earth’s subsurface. Integrating historical production data into the geo-modelling workflow, commonly designated by history matching, allows better reservoir characterisation and the possibility of predicting the reservoir behaviour. We present herein a geostatistical-based multi-objective history matching methodology. It starts with the generation of an initial ensemble of the subsurface petrophysical property of interest through stochastic sequential simulation. Each model is then ranked according the match between its dynamic response, after fluid flow simulation, and the observed available historical production data. This enables building regionalised Pareto fronts and the definition of a large ensemble of optimal subsurface Earth models that fit all the observed production data without compromising the exploration of the uncertainty space. The proposed geostatistical multi-objective history matching technique is successfully implemented in a benchmark synthetic reservoir dataset, the PUNQ-S3, where 12 objectives are targeted.  相似文献   
109.
International Journal of Earth Sciences - The Juchatengo complex (JC) suite is located between the Proterozoic Oaxacan complex to the north and the Xolapa complex to the south, and was amalgamated...  相似文献   
110.
Due to its harmful impact on human health, the presence of heavy metals, metalloids and other toxic pollutants in drinking or irrigation water is a major concern. Recent studies have proved that nanosized adsorbents are significantly more effective than their microsized counterparts. Particular attention has been given to nanocomposites with nanoadsorbents embedded in matrixes that could provide stability to the material and contribute to eliminating problems that may appear when using conventional granular systems. This study presents the preparation of a novel hybrid filter from a commercially available polypropylene (PP) non-woven fabric matrix modified with multiwall carbon nanotubes (MWCNT) and iron oxy(hydroxide) nanoparticles, and its use in the removal of As(III). A Box–Behnken statistical experimental design has been chosen to explore relevant variables affecting the filter performance: (1) As(III) concentration, (2) pH and (3) sorbent dose. From an As(III) concentration of 10 mg L?1, at pH 6.5 and with a sorbent dose of 5 g L?1, the PP filter modified with MWCNT removes 10% of the initial metalloid concentration, reaching a capacity of 0.27 mg g?1. After modification with iron oxy(hydroxide), the performance of the material is largely enhanced. The filter, under the same conditions, removes 90% of the initial As(III) concentration, reaching a capacity almost tenfold higher (2.54 mg g?1). This work demonstrates that the developed hybrid filter is effective toward the removal of As(III) in a wide range of pHs. A cubic regression model to compute the removal of the filter as a function of pH and sorbent dose is provided.  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