全文获取类型
收费全文 | 1127篇 |
免费 | 56篇 |
国内免费 | 282篇 |
专业分类
测绘学 | 51篇 |
大气科学 | 119篇 |
地球物理 | 535篇 |
地质学 | 422篇 |
海洋学 | 160篇 |
天文学 | 80篇 |
综合类 | 26篇 |
自然地理 | 72篇 |
出版年
2024年 | 4篇 |
2023年 | 16篇 |
2022年 | 9篇 |
2021年 | 13篇 |
2020年 | 9篇 |
2019年 | 13篇 |
2018年 | 16篇 |
2017年 | 12篇 |
2016年 | 13篇 |
2015年 | 17篇 |
2014年 | 21篇 |
2013年 | 26篇 |
2012年 | 40篇 |
2011年 | 88篇 |
2010年 | 23篇 |
2009年 | 28篇 |
2008年 | 73篇 |
2007年 | 61篇 |
2006年 | 56篇 |
2005年 | 71篇 |
2004年 | 71篇 |
2003年 | 55篇 |
2002年 | 42篇 |
2001年 | 34篇 |
2000年 | 63篇 |
1999年 | 34篇 |
1998年 | 32篇 |
1997年 | 38篇 |
1996年 | 27篇 |
1995年 | 33篇 |
1994年 | 27篇 |
1993年 | 48篇 |
1992年 | 30篇 |
1991年 | 41篇 |
1990年 | 33篇 |
1989年 | 28篇 |
1988年 | 23篇 |
1987年 | 35篇 |
1986年 | 16篇 |
1985年 | 23篇 |
1984年 | 14篇 |
1983年 | 14篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 17篇 |
1979年 | 4篇 |
1937年 | 5篇 |
1935年 | 5篇 |
1934年 | 4篇 |
1923年 | 4篇 |
排序方式: 共有1465条查询结果,搜索用时 156 毫秒
541.
Schroeder T Devlin MJ Brando VE Dekker AG Brodie JE Clementson LA McKinna L 《Marine pollution bulletin》2012,65(4-9):210-223
Riverine freshwater plumes are the major transport mechanism for nutrients, sediments and pollutants into the Great Barrier Reef (GBR) lagoon and connect the land with the receiving coastal and marine waters. Knowledge of the variability of the freshwater extent into the GBR lagoon is relevant for marine park management to develop strategies for improving ecosystem health and risk assessments. In this study, freshwater extent has been estimated for the entire GBR lagoon area from daily satellite observations of the Moderate Resolution Imaging Spectroradiometer (MODIS) between 2002 and 2010. To enable a reliable mapping of freshwater plumes we applied a physics-based coastal ocean colour algorithm, that simultaneously retrieves chlorophyll-a, non-algal particulate matter and coloured dissolved organic matter (CDOM), from which we used CDOM as a surrogate for salinity (S) for mapping the freshwater extent. 相似文献
542.
The geographical distributions of polyaromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), hexachlorobenzene, and 1,1-dichloro-2,2-bis(4-chlorophenyl)ethene (4,4'-DDE) were studied in the Berau delta (East Kalimantan, Indonesia), using sediment sampling and passive water sampling with semipermeable membrane devices. High concentrations of perylene were observed in sediments (54-580 ng g(-1) dry weight), and water (1-680 pg L(-1)). Perylene accounted for about 60% of the total concentrations of PAHs in the sediment. The relative abundance of the other PAHs was indicative of petrogenic sources. Concentrations of PCBs, hexachlorobenzene, and 4,4'-DDE in sediments were below or close to the detection limit (~ 0.02 ng g(-1)). The analysis of a sediment core revealed no appreciable changes in the concentration of target compounds over the past three decades. We show that sediment sampling and passive water sampling are complementary techniques, and propose to bring the results of both methods to the same concentration scale, using locally derived sediment-water partition coefficients. 相似文献
543.
Real-time PCR and NASBA for rapid and sensitive detection of Vibrio cholerae in ballast water 总被引:2,自引:0,他引:2
Fykse EM Nilsen T Nielsen AD Tryland I Delacroix S Blatny JM 《Marine pollution bulletin》2012,64(2):200-206
Transport of ballast water is one major factor in the transmission of aquatic organisms, including pathogenic bacteria. The IMO-guidelines of the Convention for the Control and Management of Ships' Ballast Water and Sediments, states that ships are to discharge <1 CFU per 100 ml ballast water of toxigenic Vibrio cholerae, emphasizing the need to establish test methods. To our knowledge, there are no methods sensitive and rapid enough available for cholera surveillance of ballast water. In this study real-time PCR and NASBA methods have been evaluated to specifically detect 1 CFU/100ml of V. cholerae in ballast water. Ballast water samples spiked with V. cholerae cells were filtered and enriched in alkaline peptone water before PCR or NASBA detection. The entire method, including sample preparation and analysis was performed within 7 h, and has the potential to be used for analysis of ballast water for inspection and enforcement control. 相似文献
544.
In the study, we establish centennial records of anthropogenic lead pollution at different locations in the North Atlantic (Iceland, USA, and Europe) by means of lead deposited in shells of the long-lived bivalve Arctica islandica. Due to local oceanographic and geological conditions we conclude that the lead concentrations in the Icelandic shell reflect natural influxes of lead into Icelandic waters. In comparison, the lead profile of the US shell is clearly driven by anthropogenic lead emissions transported from the continent to the ocean by westerly surface winds. Lead concentrations in the European North Sea shell, in contrast, are dominantly driven by local lead sources resulting in a much less conspicuous 1970s gasoline lead peak. In conclusion, the lead profiles of the three shells are driven by different influxes of lead, and yet, all support the applicability of Pb/Ca analyses of A. islandica shells to reconstruct location specific anthropogenic lead pollution. 相似文献
545.
The European Atlantic area has been the scene of a number of extensive shipping incidents with immediate and potential long-term impacts to marine ecosystems. The occurrence of accidental spills at sea requires an effective response that must include a well executed monitoring programme to assess the environmental contamination and damage of the affected marine habitats. Despite a number of conventions and protocols developed by international and national authorities that focused on the preparedness and response to oil and HNS spills, much remains to be done, particularly in relation to the effectiveness of the environmental monitoring programmes implemented after oil and HNS spills. Hence, the present study reviews the status of the environmental monitoring programmes established following the major spill incidents over the last years in European waters, aiming at identifying the key monitoring gaps and drawing priorities for an effective environmental monitoring of accidental spills. 相似文献
546.
Forty-two surface sediment samples collected from the southern coastal East China Sea (ECS) were analyzed for organochlorine pesticides (OCPs). The results showed high concentrations of DDTs and parent DDT fractions in the nearshore area, suggesting that there is still a fresh input of these species from non-point sources, probably due to the recent usage of relevant products. However, for HCHs, the high concentrations with elevated β-HCH fraction were focused at the local major river estuaries, indicating that soils-released HCH input was mainly from the major river runoffs. The distribution and composition of OCPs in the coastal ECS could be more prominently controlled by the direct regional inputs rather than the general natural sorption process on particulate organic carbon. DDTs and chlordane are more important for their potential ecotoxicological risk on neighboring benthic community in the nearshore region and the local major river estuaries. 相似文献
547.
V.T.Trofimov 《地学前缘》2005,12(4):607-613
在地球各大陆上工程地质条件水平和垂直上的变化反映出它们的区域性,它受控于该地区的热量、湿度及其比率。这就是在类似地质结构的地区中,不同的纬度和海拔高度形成了不同的工程地质条件的原因。引入工程地质区这个概念的目的在于说明工程地质条件的区域性。工程地质区一词的意义是指一个大的工程地质地区或省,在其中主要由水的形态决定的岩土状态是均一的并从工程地质观点来看具有区域稳定性。已经确定了以下工程地质区类型:永久性的多年冻土区域、多年冻土和融化沉积共存区域,以及融化和不冻岩石区域,它们再细分为亚区。工程地质条件区域性概念要考虑的主要问题有:分区原则、工程地质区域的类型和种类、地球各大陆上工程地质区域的空间分布规律性、“理想”大陆上的分布模型。 相似文献
548.
在很长一段时间,地磁场的来源,行为,乃至它的本质属性都是高深莫测的.地磁场通过罗盘指示方向,向航海家提供了一种有用且复杂的工具,因而被人们所熟悉.虽然罗盘最早是中国人发明的,但欧洲人进行了地磁学的系统化早期研究,他们最早把罗盘的精致和实用结合在一起,进而发展了大部分罗盘定向的早期理论. 相似文献
549.
断层强度是孕震带的一个基本性质,它随时间的变化特性可以增加或减小断层破坏的可能性并最终触发地震。虽然断层强度变化可以用来解释诸如地震活动的远程触发(Hilland Prejean,2007)等多种现象,但至今还没有切实的方法对这个重要性质进行现场监测。文中我们认为,通过对圣安德烈斯断层帕克菲尔德地区近20年(1987~2008)的观测,揭示了一种监测断层强度的方法。 相似文献
550.
To simulate the dynamic interaction between a saline lagoon and a ground water system, a numerical model for two-dimensional, variable-density, saturated-unsaturated, and coupled flow and solute transport (saltwater intrusion by finite elements and characteristics [SIFEC]) was modified to allow the volume of water and mass of salt in the lagoon to vary with each time step. The modified SIFEC allows the stage of a lagoon to vary in accordance with a functional relation between the stage and water volume of the lagoon, and also allows the salt concentration of the lagoon to vary in accordance with the salt budget of the lagoon including chemical precipitation and dissolution of salt. The updated stage and salt concentration of the lagoon are in turn used as transient boundary conditions for the coupled flow and solute transport model. The utility of the modified model was demonstrated by applying it to the eastern Mediterranean coastal region of Turkey for assessing impacts of climate change on the subsurface environment under scenarios of sea level rise, increased evaporation, and decreased precipitation. 相似文献