全文获取类型
| 收费全文 | 1578篇 |
| 免费 | 724篇 |
| 国内免费 | 1291篇 |
专业分类
| 测绘学 | 53篇 |
| 大气科学 | 167篇 |
| 地球物理 | 758篇 |
| 地质学 | 2244篇 |
| 海洋学 | 72篇 |
| 天文学 | 91篇 |
| 综合类 | 137篇 |
| 自然地理 | 71篇 |
出版年
| 2021年 | 1篇 |
| 2020年 | 2篇 |
| 2015年 | 3篇 |
| 2014年 | 1篇 |
| 2013年 | 10篇 |
| 2012年 | 4篇 |
| 2011年 | 219篇 |
| 2010年 | 119篇 |
| 2009年 | 195篇 |
| 2008年 | 50篇 |
| 2007年 | 136篇 |
| 2006年 | 260篇 |
| 2005年 | 287篇 |
| 2004年 | 553篇 |
| 2003年 | 342篇 |
| 2002年 | 279篇 |
| 2001年 | 203篇 |
| 2000年 | 142篇 |
| 1999年 | 97篇 |
| 1998年 | 125篇 |
| 1997年 | 139篇 |
| 1996年 | 82篇 |
| 1995年 | 61篇 |
| 1994年 | 48篇 |
| 1993年 | 118篇 |
| 1992年 | 68篇 |
| 1991年 | 18篇 |
| 1990年 | 2篇 |
| 1989年 | 13篇 |
| 1988年 | 1篇 |
| 1987年 | 8篇 |
| 1986年 | 2篇 |
| 1984年 | 1篇 |
| 1982年 | 1篇 |
| 1979年 | 1篇 |
| 1950年 | 2篇 |
排序方式： 共有3593条查询结果，搜索用时 15 毫秒
1.
2.
3.
4.
5.
通过动力学和等温吸附实验,研究了不同初始氨氮浓度下水溶铵、交换铵和固定铵在中砂上的吸附规律。结果表明,吸附平衡时各种形态铵含量随初始氨氮浓度增加而增大。3种形态铵吸附行为符合准二级动力学方程。吸附速率常数K大小顺序为：固定铵〉交换铵〉水溶铵,初始速率：固定铵〈交换铵〈水溶铵。随着初始氨氮浓度的增加,水溶铵占总铵的比重由40%上升到65%,其吸附的主要限制步骤为颗粒间扩散。交换铵对总铵的贡献率维持在25%左右,吸附饱和后有所降低,初始氨氮浓度为交换铵吸附的主要限制步骤。固定铵达到饱和时,吸附量只有26.18 mg/kg,对总铵的贡献率由33%下降到9%。 相似文献
6.
In this article,the backstripping technique was used in studying the subsidence charac-ters of the Qiongdongnan(琼东南) basin(QDNB) in order to understand its dynamic mechanism of formation and evolution.Meanwhile,the geothermal characteristics of this area were summarized,and the stretching factors(β) of the upper crust,the whole crust,and the whole lithosphere were calculated.The QDNB is characterized by high subsidence rate,high geothermal gradient,high geothermal heat flow,and the lithosphere stretching an... 相似文献
7.
The Huimin (惠民) depression is a third-level tectonic element of the Bohai (渤海) Bay basin in eastern China. The central uplift belt is the most important oil and gas accumulation zone in the depression, but the lack of adequate geological studies in the area has greatly hindered exploration and development. In this article, using seismic data, fracture mechanics, and a combination of data on fault growth indices and fault throws, we present an analysis of tectonic activity in the central uplift belt and adja... 相似文献
8.
High quality marine source rock (HQMSR) is the key prerequisite for medium to large hydrocarbon accumulations. However, the forming mechanism remains unclear. On the basis of the in-vestigation for the geodynamic setting of the Middle-Upper Yangtze during the Early Cambrian in dif-ferent spatial scales and the analysis of trace elements, the main controlling factors of the development of high quality marine source rock are discussed, with specific consideration of the burial rate of the organic matter. The ... 相似文献
9.
Mixed carbonate-siliciclastic sedimentation is common in the Upper Permian-Lower Tri-assic in the western Sichuan(四川) basin.The extensional movement was strong in the Late Permian,resulting in differential uplifting of fault blocks.During this period,there was an extensive retrogres-sion.The Kangdian(康滇) ancient land progressive uplifted and enlarged,forming the major prove-nance of terrigenous clastics.In Changxingian age,mixed terrigenous-carbonate sedimentation was dis-tributed in the area between Dafeis... 相似文献
10.
A 1.2 m snow pit was recovered on July 29th, 2009 from the Bogda Glacier, eastern Tianshan (天山). The sample site temperature of -9.6 ℃ indicates that the unique glaciochemical re-cord was well preserved and suitable for the reconstruction of air pollution levels in this previously un-explored region. Samples were analyzed for major ions (Na+, K+, Ca2+, Mg2+, NH4+, Cl-, SO42-, NO3-, HCOO-, and CH3COO-). NO3- and SO42- were characterized by significant high levels of pollution con-centration. Most air masses ... 相似文献