全文获取类型
收费全文 | 6915篇 |
免费 | 1338篇 |
国内免费 | 1618篇 |
专业分类
测绘学 | 207篇 |
大气科学 | 955篇 |
地球物理 | 1881篇 |
地质学 | 4598篇 |
海洋学 | 802篇 |
天文学 | 80篇 |
综合类 | 438篇 |
自然地理 | 910篇 |
出版年
2024年 | 41篇 |
2023年 | 119篇 |
2022年 | 287篇 |
2021年 | 312篇 |
2020年 | 266篇 |
2019年 | 346篇 |
2018年 | 272篇 |
2017年 | 275篇 |
2016年 | 290篇 |
2015年 | 323篇 |
2014年 | 412篇 |
2013年 | 419篇 |
2012年 | 426篇 |
2011年 | 454篇 |
2010年 | 370篇 |
2009年 | 432篇 |
2008年 | 474篇 |
2007年 | 492篇 |
2006年 | 501篇 |
2005年 | 388篇 |
2004年 | 393篇 |
2003年 | 316篇 |
2002年 | 278篇 |
2001年 | 219篇 |
2000年 | 229篇 |
1999年 | 197篇 |
1998年 | 222篇 |
1997年 | 216篇 |
1996年 | 170篇 |
1995年 | 128篇 |
1994年 | 116篇 |
1993年 | 82篇 |
1992年 | 98篇 |
1991年 | 54篇 |
1990年 | 57篇 |
1989年 | 54篇 |
1988年 | 43篇 |
1987年 | 16篇 |
1986年 | 20篇 |
1985年 | 11篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1982年 | 15篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1954年 | 4篇 |
排序方式: 共有9871条查询结果,搜索用时 15 毫秒
41.
This paper reports a study of the field measurements and monitoring of wastewater discharge in sea water at Bari East (Italy). A wastewater sea outfall system is an integral and fundamental part of each wastewater treatment with ultimate sink in the sea water. The design of a water treatment plant and wastewater outfall must take into account the use of the environmental water, the values of physicochemical parameters to be respected in order to safeguard the use itself and the quality of the environmental water where wastewater is issued. In the present study measurements of sea current velocity components were carried out with a VM-ADP (Vessel-Mounted Acoustic Doppler Profiler). Salinity, wind directions and velocities were assessed with, for one survey, the total faecal coliforms and other biochemical parameters. It was emphasized that the measurements necessary for monitoring cannot be concentrated in the wastewater outfall pipe zone only, but should be extended to a neighbouring area of the outfall pipe, with an extension depending on the wastewater discharge, the polluting charge and the magnitude of the sea currents and the winds typical of the zone of interest. The analyses presented in this paper confirm that the sea zones close to the wastewater outfall pipe are particularly sensitive and vulnerable. Such results must be considered in the planning of a wastewater outfall pipe. 相似文献
42.
闽江口水动力和污染扩散数值模拟 总被引:3,自引:0,他引:3
本文建立了闽江口二维水动力、污染扩散数值模型,模型采用ADI双向隐式求解。在水动力模拟中,对岸界的丁坝有用线性边界进行拟合,并考虑到河口区侧向摩擦作用;在污染扩散模拟中,用动态拟合的方法对浓度水边界进行了较为合理的改进。计算结果表明,本模型是成功的。 相似文献
43.
44.
本文根据1992年夏季对湄洲湾水质环境质量调查资料,对该海区海水中油的含量及分布特征进行了分析研究。结果表明:湄洲湾夏季表层海水油的含量为5-51μg/dm^3,平均值为19.8μg/dm^3。海水的混合系数较小,高潮和低潮时油含量分布的差异,除了与陆源污染源分布有关外,主要是由水文动力学条件所决定。 相似文献
45.
46.
47.
A numerical procedure is described for predicting the motion and structural responses of tension leg platforms (TLPs) in waves. The developed numerical approach, in a TLP is assumed to be flexible instead of rigid, is based on a combination of the three dimensional source distribution method and the finite-element method. The hydrodynamic interactions among TLP members, such as columns and pontoons, are included in the motion and structural response analysis. Numerical results are compared with the experimental and numerical ones. The results of comparison confirmed the validity of the proposed approach. 相似文献
48.
重矿物组合、含量变化和特征矿物的分布及变化规律是沿海泥沙来源和运移趋势判断的重要手段之一。通过对廉州湾南部海域海底表层沉积物的重矿物分析 ,发现该区重矿物分布以北海地角为界 ,其百分含量和特征矿物南北有别 ,可能分别代表不同的物质来源区。其中廉州湾北部南流江流域来沙是该区主要物源 ,运移趋势为自 NE向 SW;地角西南岸段、岭南侧海岸侵蚀及银滩来沙也为该区提供了部分物源 ,运移趋势为绕过冠头岭沿海岸向 N方向运移。由于缺乏北海陆域陆相地层重矿物含量等相关资料 ,暂未做物质来源区的具体判断 相似文献
49.
The tolerance of the oligochaete Monopylephorus rubroniveus and the polychaete Streblospio benedicti to sediment-associated fluoranthene was characterized under normoxic (>80% dissolved oxygen saturation) and moderately hypoxic ( approximately 50% dissolved oxygen saturation) conditions. Under both conditions, M. rubroniveus was highly tolerant of fluoranthene. Streblospio benedicti was considerably less tolerant of fluoranthene compared with M. rubroniveus. In addition, S. benedicti was less tolerant to fluoranthene under moderately hypoxic conditions, although no differences in sensitivity between the two oxygen conditions were observed based upon median lethal tissue residues. Bioaccumulation factors were higher for S. benedicti exposed to moderate hypoxia, suggesting that behavioral adaptations to compensate for the lower dissolved oxygen increased its bioaccumulation of fluoranthene. The results of the present laboratory study demonstrate that (1). changes in annelid tolerance to fluoranthene under varying oxygen conditions is a species-dependent phenomenon and (2). the differential tolerance of these two annelids to these combined stressors is consistent with their relative abundances in the field. 相似文献
50.