全文获取类型
收费全文 | 1492篇 |
免费 | 306篇 |
国内免费 | 441篇 |
专业分类
测绘学 | 129篇 |
大气科学 | 43篇 |
地球物理 | 276篇 |
地质学 | 1558篇 |
海洋学 | 93篇 |
天文学 | 30篇 |
综合类 | 56篇 |
自然地理 | 54篇 |
出版年
2024年 | 14篇 |
2023年 | 34篇 |
2022年 | 75篇 |
2021年 | 80篇 |
2020年 | 88篇 |
2019年 | 101篇 |
2018年 | 102篇 |
2017年 | 99篇 |
2016年 | 141篇 |
2015年 | 97篇 |
2014年 | 98篇 |
2013年 | 93篇 |
2012年 | 117篇 |
2011年 | 101篇 |
2010年 | 90篇 |
2009年 | 102篇 |
2008年 | 95篇 |
2007年 | 82篇 |
2006年 | 74篇 |
2005年 | 78篇 |
2004年 | 74篇 |
2003年 | 75篇 |
2002年 | 58篇 |
2001年 | 40篇 |
2000年 | 53篇 |
1999年 | 26篇 |
1998年 | 22篇 |
1997年 | 32篇 |
1996年 | 24篇 |
1995年 | 18篇 |
1994年 | 15篇 |
1993年 | 7篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1979年 | 1篇 |
1954年 | 3篇 |
排序方式: 共有2239条查询结果,搜索用时 46 毫秒
1.
2.
JÜRGEN TITSCHACK CAMPBELL S. NELSON TIM BECK ANDRÉ FREIWALD ULRICH RADTKE 《Sedimentology》2008,55(6):1747-1776
Autochthonous red algal structures known as coralligène de plateau occur in the modern warm‐temperate Mediterranean Sea at water depths from 20 to 120 m, but fossil counterparts are not so well‐known. This study describes, from an uplifted coastal section at Plimiri on the island of Rhodes, a 450 m long by 10 m thick Late Pleistocene red algal reef (Coralligène Facies), interpreted as being a coralligène de plateau, and its associated deposits. The Coralligène Facies, constructed mainly by Lithophyllum and Titanoderma, sits unconformably upon the Plio‐Pleistocene Rhodes Formation and is overlain by a Maerl Facies (2 m), a Mixed Siliciclastic‐Carbonate Facies (0·2 m) and an Aeolian Sand Facies (2·5 m). The three calcareous facies, of Heterozoan character, are correlated with established members in the Lindos Acropolis Formation in the north of the island, while the aeolian facies is assigned to the new Plimiri Aeolianite Formation. The palaeoenvironmental and genetic‐stratigraphic interpretations of these mixed siliciclastic‐carbonate temperate water deposits involved consideration of certain characteristics associated with siliciclastic shelf and tropical carbonate shelf models, such as vertical grain‐size trends and the stratigraphic position of zooxanthellate coral growths. Integration of these results with electron spin resonance dates of bivalve shells indicates that the Coralligène Facies was deposited during Marine Isotope Stage 6 to 5e transgressive event (ca 135 to 120 ka), in water depths of 20 to 50 m, and the overlying Maerl Facies was deposited during regression from Marine Isotope Stage 5e to 5d (ca 120 to 110 ka), at water depths of 25 to 40 m. The capping Aeolian Sand Facies, involving dual terrestrial subunits, is interpreted as having formed during each of the glacial intervals Marine Isotope Stages 4 (71 to 59 ka) and 2 (24 to 12 ka), with soil formation during the subsequent interglacial periods of Marine Isotope Stages 3 and 1, respectively. Accumulation rates of about 0·7 mm year?1 are estimated for the Coralligène Facies and minimum accumulation rates of 0·2 mm year?1 are estimated for the Maerl Facies. The existence of older red algal reefs in the Plimiri region during at least Marine Isotope Stages 7 (245 to 186 ka) and 9 (339 to 303 ka) is inferred from the occurrence of reworked coralligène‐type lithoclasts in the basal part of the section and from the electron spin resonance ages of transported bivalve shells. 相似文献
3.
4.
5.
长82亚油层组是甘肃庆城地区庄19井区上三叠统延长组中储集砂岩相对富集的层位,但砂岩低渗透性的特点显著,成为影响该区石油储产量增长的主要地质因素。结合前人的相关工作,通过钻井岩心观察、测井曲线分析、储层岩石实验测试等工作,详细地分析了庄19井区长82亚油层组低渗透储层的地质特征,认为沉积微相和压实作用、胶结作用是控制低渗透性储集砂岩发育和分布的主要地质因素,寻找以水下分流河道微相为代表的有利储集相带砂岩体是油气勘探的重要方向。 相似文献
6.
7.
8.
大港油田官142断块巨厚砂岩的储层流动单元 总被引:1,自引:1,他引:0
以黄骅坳陷官142断块中生界油藏为例,探讨巨厚砂岩储层流动单元的研究方法。巨厚砂岩储层流动单元研究包括两个层次,一为确定渗流屏障和连通体的分布,二为连通体内部储层渗流差异分析。研究表明,官142断块渗流屏障主要有泥质屏障、钙质砂岩胶结屏障和钙质砂砾岩胶结屏障3种类型。通过对连通体内部砂体渗流差异性分析,将连通体划分为3类流动单元。其中A类流动单元以粗孔、粗喉类型为主,渗流性能好,吸水强度大;B类流动单元储层为中孔、中喉型,渗流性能中等,吸水强度次之;C类流动单元储层多为粉细砂岩、砂砾岩或钙质胶结稍差的储层,吸水强度较差。通过流动单元的划分与研究,对预测该区的剩余油分布规律和优化调整方案提供依据。 相似文献
9.
10.
Fractal-like adsorption kinetics of Pb^2+ in rocks 总被引:1,自引:0,他引:1
The adsorption kinetics of Pb^2+ in rocks has been studied using ion selective electrodes and atomic absorption spectrophotometer. The results showed that the adsorption process is a fractal-like reaction. The adsorption rate was relatively high before 30 minutes, and then dropped. The saturated adsorption capacity (a) of Pb^2+ and kinetic parameters (b, a, D and k) increased with increasing initial concentrations of Pb^2+. These parameters (except a) decreased while Na^+ was present in the solution. Furthermore, the smaller the rocks were in grain size, the bigger these kinetic parameters would be, though the parameter a was almost constant. 相似文献