全文获取类型
收费全文 | 728篇 |
免费 | 144篇 |
国内免费 | 90篇 |
专业分类
测绘学 | 27篇 |
大气科学 | 10篇 |
地球物理 | 229篇 |
地质学 | 504篇 |
海洋学 | 133篇 |
天文学 | 1篇 |
综合类 | 29篇 |
自然地理 | 29篇 |
出版年
2024年 | 2篇 |
2023年 | 11篇 |
2022年 | 22篇 |
2021年 | 7篇 |
2020年 | 20篇 |
2019年 | 15篇 |
2018年 | 6篇 |
2017年 | 45篇 |
2016年 | 32篇 |
2015年 | 23篇 |
2014年 | 45篇 |
2013年 | 41篇 |
2012年 | 26篇 |
2011年 | 58篇 |
2010年 | 66篇 |
2009年 | 54篇 |
2008年 | 37篇 |
2007年 | 52篇 |
2006年 | 40篇 |
2005年 | 24篇 |
2004年 | 37篇 |
2003年 | 31篇 |
2002年 | 44篇 |
2001年 | 21篇 |
2000年 | 45篇 |
1999年 | 11篇 |
1998年 | 25篇 |
1997年 | 15篇 |
1996年 | 26篇 |
1995年 | 16篇 |
1994年 | 13篇 |
1993年 | 10篇 |
1992年 | 8篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 9篇 |
1984年 | 3篇 |
1983年 | 2篇 |
排序方式: 共有962条查询结果,搜索用时 46 毫秒
891.
Polycyclic aromatic hydrocarbons (PAHs) are types of hazardous contaminants, which their ingestion could cause severe consequences on human health. Leakages from storage tanks, underground pipelines, and evaporation ponds are the main sources of soil and groundwater contaminations at the Tehran Oil Refinery area (TOR site), located in south of Tehran, Iran. In this study, soil samples were collected from different locations at and adjacent to a polluted stream in the south of the refinery. The samples were analyzed for two hazardous PAH compounds, namely benzo[a]anthracene and acenaphthene. The clean up levels due to the accidental ingestion of contaminated soils at the site were also investigated in accordance to the U.S.EPA guidelines. Comparing the soil analysis results indicated that the benzo[a]anthracene concentrations in the samples varied from 53 to 299 mg/kg, which were higher than the clean up level of 1.17 mg/kg. Thus, soil remediation is required for this contaminant. The acenaphthene analysis results denoted that the average concentration of this contaminant was below the clean up level of 116.67 mg/kg, indicating that no treatment for this contaminant is necessary at the TOR site. Also, because the slope of the ground extends to the south of the stream, which stimulates the migration of the contaminants in this direction due to advection and dispersion mechanisms, the average of benzo[a]anthracene concentrations in south samples was higher than north samples (i.e., Cavg(S) = 160 ppm, Cavg(N) = 113 ppm). Various treatment techniques such as thermal desorption, soil vapor extraction (SVE), and solidification/stabilization (S/S) were investigated for this site. Due to moderate to high plasticity and relatively low permeability of the soil and low volatility of benzo[a]anthracene, however S/S method is recommended as a practical approach for the remediation of the soil at the site. 相似文献
892.
碳酸盐岩中缝洞方解石成岩环境的矿物地球化学判识——以塔河油田的沙79井和沙85井为例 总被引:1,自引:0,他引:1
摘要在塔里木盆地塔河油田4区沙79井、6区沙85井奥陶系鹰山组岩芯的详细观察基础上,对裂隙、溶洞及巨型洞穴中的方解石晶体的晶胞参数、化学成分、碳、氧同位素、流体包裹体中的氢同位素等分析与研究表明,至少存在两种成岩环境:一是以大气淡水表生环境,方解石中晶胞参数(c)=17.057~17.062,Fe2O3=0.06%~0.07%,Sr=53.3×10-6~96.2×10-6、Ba=19×10-6~28×10-6,Mg/Ca(×103)=1.94~5.14,Sr/Ba=2.12~5.24,δ18OPDB较低(-15‰~-17‰)、较低δ13CPDB(-4‰~-2.0‰),不含或较少含烃类,流体包裹体中氢δDPDB=-94.99‰~-109.54‰为特征;另一是地层混合水埋藏环境为主,方解石中晶胞参数(c)=17.064~17.065(个别达17.212)、Fe2O3=0.06%~0.18%,Sr=111×10-6~208×10-6、Ba=215×10-6~479×10-6,Mg/Ca(×103)=1.53~1.76,Sr/Ba=0.49~0.58,方解石δ18OPDB低(-9.6‰~-13.7‰)、流体包裹体中氢δDPDB=-77.5‰~-88.2‰为特征;另外,在巨型洞穴中方解石中组分的剧烈变化反映了洞穴充填发生于不同的水文地质—地球化学体系。 相似文献
893.
894.
Peroxisomal proteomics was applied to assess possible biological effects after the Prestige’s oil spill. Mussels were sampled in July 2004 and 2005 in four stations in the NW (closest to the spill) and NE coasts of the Iberian Peninsula. Principal components analysis (PCA) suggested differences in protein expression among stations and sampling years. Several proteins were putatively identified by mass spectrometry and immunolocalization. PC1 separated the NW stations in 2004 from the rest of the stations and sampling years mainly due to up-regulation of peroxisomal β-oxidation proteins and PMP70. PC3 separated the NE stations, based on up-regulation of the antioxidant enzyme catalase in 2004 compared to 2005. PC4 separated the stations in the NE and the NW. This work shows that environmental proteomics, together with multivariate data analysis, could provide information to interpret the effects of oil spills at cellular level in mussels. 相似文献
895.
896.
The protection of coastal areas against oil pollution is often addressed with the use of floating booms. These bodies are subject to an empirical design always based on physical models. Indeed, the numerical modelling of a two-phase flow (oil and water) with complicated free surface in the vicinity of a floating body is a challenging issue. The Smoothed Particle Hydrodynamics (SPH) Lagrangian numerical method is appropriate to such simulations since it allows the modelling of complex motions and fluid–structure interactions. In this paper we first study the mechanism of oil leakage by entrainment due to combined turbulent production and buoyancy. Then, we present the main features of the SPH method in a turbulent formalism and apply this model to predict the motion of a boom and an oil spill in an open-channel and a wave flume, for three types of oil (heavy, light and emulsion). Numerical results are compared to experiments and used to depict criteria for oil leakage. It appears that oil leakage by entrainment occurs when the surface water velocity upstream the boom exceeds a critical value which was estimated around 0.5 m/s for a light oil under steady current. A more accurate criterion is derived from theoretical considerations and successfully compared to numerical experiments. In the case of wave flume, no validation from experiments could be made. However, it appears that leakage occurs from a critical wave height between 0.5 and 1.0 m, for the tested wave period of 4 s. A more extended panel of numerical tests would allow a better knowledge of the involved mechanisms and critical parameters. An extensive use of this model should extend our knowledge regarding the mechanisms of oil leakage under a boom and allow a better and easier design of booms in the near future. 相似文献
897.
898.
Jinglan Luo S. Morad Xiaoli Zhang Shike Yan Fuli Wu Yuhong Li Junmin Xue 《中国科学D辑(英文版)》2002,45(7):616-634
The reservoir quality of Jurassic and Triassic fluvial and lacustrine-deltaic sandstones of the Yanchang Oil Field in the
Ordos Basin is strongly influenced by the burial history and facies-related diagenetic events. The fluvial sandstones have
a higher average porosity (14.8%) and a higher permeability (12.7 × 10−3 μm2) than those of the deltaic sandstones (9.8% and 5.8 ×10−3) μm2, respectively). The burial compaction, which resulted in 15% and 20% porosity loss for Jurassic and Triassic sandstones,
respectively, is the main factor causing the loss of porosity both for the Jurassic and Triassic sandstones. Among the cements,
carbonate is the main one that reduced the reservoir quality of the sandstones. The organic acidic fluid derived from organic
matter in the source rocks, the inorganic fluid from rock-water reaction during the late diagenesis, and meteoric waters during
the epidiagenesis resulted in the formation of dissolution porosity, which is the main reason for the enhancement of reservoir-quality. 相似文献
899.
以塔里木盆地北部轮古西奥陶系碳酸盐岩岩溶洞穴型油藏为例,针对几个制约油田高效开发的重要问题,采用了相应的油藏描述技术对策:(1)在分析岩溶成因的基础上,对三维地震数据进行岩溶洞穴分层解释,描述不同洞穴层发育特征;(2)采用岩溶沟谷趋势面法确定油水界面,指导避水开发;(3)通过岩石物理分析,确定了用于识别泥质充填洞穴的泥质指示因子,然后运用地震反演技术,筛选出未被泥质充填的有效储层。通过这三项技术方法的实施,弄清了四层洞穴储层的分布特征以及它们与供油的关系;厘清了油水在洞穴储层中的赋存特征;发现岩溶斜坡的充填程度高于岩溶台地;最后评价出三类残丘含油单元。三项技术对策在岩溶洞穴型油藏描述方面具有较强适用性,可为相同类型油藏的高效开发提供技术借鉴。 相似文献
900.
根据准噶尔盆地及周围山区航空磁测结果,发现了5个沉积盖层厚度大于12km的拗陷,其中3个的盖层厚度可达18km,从而提高了盆地的油气远景评价。盆地内为隆拗相间的格局。 盆地内有一范围比盆地略小的以前寒武系为基底的稳定地块——准噶尔地块,它以断裂为边界。 盆地中部的北西西向长条状正异常,推断是由发育在下古生代裂陷槽中以基性为主的基性超基性杂岩体引起的。 相似文献