全文获取类型
收费全文 | 2410篇 |
免费 | 253篇 |
国内免费 | 374篇 |
专业分类
测绘学 | 9篇 |
大气科学 | 5篇 |
地球物理 | 465篇 |
地质学 | 1245篇 |
海洋学 | 783篇 |
天文学 | 6篇 |
综合类 | 72篇 |
自然地理 | 452篇 |
出版年
2024年 | 7篇 |
2023年 | 19篇 |
2022年 | 60篇 |
2021年 | 72篇 |
2020年 | 68篇 |
2019年 | 61篇 |
2018年 | 78篇 |
2017年 | 73篇 |
2016年 | 81篇 |
2015年 | 78篇 |
2014年 | 123篇 |
2013年 | 172篇 |
2012年 | 87篇 |
2011年 | 131篇 |
2010年 | 103篇 |
2009年 | 158篇 |
2008年 | 167篇 |
2007年 | 147篇 |
2006年 | 141篇 |
2005年 | 120篇 |
2004年 | 117篇 |
2003年 | 84篇 |
2002年 | 95篇 |
2001年 | 86篇 |
2000年 | 83篇 |
1999年 | 77篇 |
1998年 | 73篇 |
1997年 | 81篇 |
1996年 | 56篇 |
1995年 | 41篇 |
1994年 | 39篇 |
1993年 | 30篇 |
1992年 | 31篇 |
1991年 | 27篇 |
1990年 | 29篇 |
1989年 | 20篇 |
1988年 | 15篇 |
1987年 | 11篇 |
1986年 | 18篇 |
1985年 | 19篇 |
1984年 | 15篇 |
1983年 | 10篇 |
1982年 | 18篇 |
1981年 | 10篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1976年 | 1篇 |
排序方式: 共有3037条查询结果,搜索用时 187 毫秒
31.
A Preliminary Study of Shear Wave in Seafloor Surface Sediments 总被引:1,自引:0,他引:1
This article preliminarily reports and analyses the transmission characteristics and behaviors of shear wave in the offshore seafloor surface sediments in China, discusses the relationships between the physical and mechanical features of the shear wave and the compression wave, and compares the testing results with that of Hamilton and Chen et al. The result shows that the shear wave can be tested if the seafloor surface sediment has tangent modulus. The shear wave velocity ranges from 50-600 m/s and the measuring frequency from 50-200 kHz. The sound velocity rate of shear wave and compression wave can be used to appraise the stress-strain feature of seafloor surface sediments. This study provides a basis for further describing and appraising the seafloor sedimentary acoustic-mechanical feature and building a geological-acoustic model on China's offshore sea area. 相似文献
32.
33.
沉积物对磷酸盐的吸附与释放 总被引:3,自引:0,他引:3
本实验研究黄河口水文站沉积物对黄河水磷的吸附释放过程和东海111号站位沉积物对海水磷的吸附释放过程。并摸拟黄河沉积物在海水中磷的吸附释放过程。结果表明:底沉积物对磷的吸附相当迅速,无论是河泥还是海泥在24h内均能达到吸附平衡。吸附量与沉积物的量和水中原有磷的浓度有关,在不同的pH条件下,沉积物对磷的吸附是有显著差别的 相似文献
34.
Natalia V. Zhukova 《Ocean Science Journal》2005,40(3):34-42
Variation in the microbial biomass and community structure found in sediment of heavily polluted bays and the adjacent unpolluted
areas were examined using phospholipid fatty acid analysis. Total microbial biomass and microbial community structure were
responding to environmental determinants, sediment grain size, depth of sediment, and pollution due to petroleum hydrocarbons.
The marker fatty acids of microeukaryotes and prokaryotes - aerobic, anaerobic, and sulfate-reducing bacteria -were detected
in sediments of the areas studied. Analysis of the fatty acid profiles revealed wide variations in the community structure
in sediments, depending on the extent of pollution, sediment depth, and sediment grain size. The abundance of specific bacterial
fatty acids points to the dominance of prokaryotic organisms, whose composition differed among the stations. Fatty acid distributions
in sediments suggest the high contribution of aerobic bacteria. Sediments of polluted sites were significantly enriched with
anaerobic bacteria in comparison with clean areas. The contribution of this bacterial group increased with the depth of sediments.
Anaerobic bacteria were predominantly present in muddy sediments, as evidenced from the fatty acid profiles. Relatively high
concentrations of marker fatty acids of sulfate-reducing bacteria were associated with organic pollution in this site. Specific
fatty acids of microeukaryotes were more abundant in surface sediments than in deeper sediment layers. Among the microeukaryotes,
diatoms were an important component. Significant amounts of bacterial biomass, the predominance of bacterial biomarker fatty
acids with abundance of anaerobic and sulfate-reducing bacteria are indicative of a prokaryotic consortium responsive to organic
pollution. 相似文献
35.
36.
渤海南部表层沉积的相特征 总被引:1,自引:0,他引:1
通过海上调查及实验室分析,查明渤海南部表层沉积物在结构类型、矿物组合、生物组分及沉积构造等相特征方面具有明显的分区性。渤海南部存在五种沉积相:黄河水下三角洲相、陆架盆地相、海湾相、潮流浅滩相及古滨岸相。黄河水下三角洲相从河口延至水深15—20米处,沉积速率很高,沉积物富含碎屑云母及CaCo_3。陆架盆地相的沉积为粉砂质粘土,具有生物扰动构造。 相似文献
37.
Since the 1997 local ban on ocean dumping of dredged sediments, the States of New York and New Jersey have pursued a policy of environmentally sound solutions to the management of dredged material, including beneficial use of stabilized dredged material (SDM) in transportation applications. A pilot study was initiated in 1998 to evaluate the use of SDM in the construction of highway embankments. Utilizing 80,000 cubic yards of dredged material, two embankments were constructed from SDM on a commercial development area adjacent to the Harbor. Geotechnical properties and handling of SDM were evaluated both during and one year post - construction. This article presents the evaluation of the embankments themselves, including constructability and performance. The results demonstrate that SDM satisfies most of the geotechnical criteria for fill construction, except those for durability, requiring proper coverage and protection similar to that provided for fills constructed on cohesive soils. This same characteristic precludes long term stockpiling of SDM prior to final placement, limiting applications to those that have schedules overlapping with dredging projects. Increased costs for the use of SDM can be as high as $8 per cubic yard over traditional fills; however, this cost may be recouped through management fees collected from dredging projects. 相似文献
38.
Zhang Jinshan Yu Guohua
Research Engineer River Harbour Department Nanjing Hydraulic Research Institute Nanjing Research Senior Engineer River Harbour Department Nanjing Hydraulic Research Institute Nanjing 《中国海洋工程》1995,(3)
- Based on field investigations, this paper analyzes three types of harbour basinns and navigation channel excavated on seabed in Jiaozhou Bay, get a general rule of deposition for excavated trough, it found that pollution is one of crucial factors resulting in the deposition of the excavated trough in the east shore of Jiaozhou Bay. With these results, it predicted the annual deposition thickness for the excavated trough and disclosed the fact that it can't be deposited deadly during one storm. At the same time, with two-dimensional numerical model, it studied the effects of the excavated trough and the reclamation near shore on tidal cureent and said that the excavated trough can decrease the current velocity passing through the trough about 10- 15%, but only limited inside and near the trough and there are no effect on other regions; reclamation can cut off the pollution sources and no obvious effect on the currents of the Jiaozhou Bay. Connecting the deep trough and Cangkou tidal channel with a new 相似文献
39.
本文研究了二层流体系统中波浪的衰减。上层为理想流体,下层为粘弹性Voigt体。导出了色散关系,计算了波浪衰减系数。对于粘性或弹性很大或很小的情况,导出了各种水深情况下近似的显式的衰减系数表示式。与精确的数值结果比较,近似程度很好。可供工程设计参考、使用。 相似文献
40.
北黄海长山群岛海域沉积环境初步研究 总被引:3,自引:0,他引:3
本文在获取1989-1993年黄海北部长山群岛海域沉积物大量数据基础上,借助沉积物粒度分析(Q型),揭示出该海域具有在“岛屿效应”影响下的4种环境能量类型,分析了与其适应的环岛沉积环境及其分布特征。 相似文献