全文获取类型
收费全文 | 93篇 |
免费 | 4篇 |
国内免费 | 7篇 |
专业分类
地球物理 | 20篇 |
地质学 | 2篇 |
海洋学 | 70篇 |
天文学 | 6篇 |
综合类 | 5篇 |
自然地理 | 1篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 2篇 |
2015年 | 9篇 |
2014年 | 4篇 |
2013年 | 15篇 |
2012年 | 2篇 |
2011年 | 6篇 |
2010年 | 2篇 |
2009年 | 6篇 |
2008年 | 4篇 |
2007年 | 7篇 |
2006年 | 1篇 |
2005年 | 7篇 |
2004年 | 4篇 |
2002年 | 1篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1988年 | 1篇 |
排序方式: 共有104条查询结果,搜索用时 62 毫秒
1.
A Santa Marta JG Ferreira GC Pitcher J Lencart e Silva 《African Journal of Marine Science》2020,42(2):151-166
The carrying capacity for bivalve shellfish culture in Saldanha Bay, South Africa, was analysed through the application of the well-tested EcoWin ecological model, in order to simulate key ecosystem variables. The model was set up using: (i) oceanographic and water-quality data collected from Saldanha Bay, and (ii) culture-practice information provided by local shellfish farmers. EcoWin successfully reproduced key ecological processes, simulating an annual mean phytoplankton biomass of 7.5 µg Chl a l–1 and an annual harvested shellfish biomass of about 3 000 tonnes (t) y–1, in good agreement with reported yield. The maximum annual carrying capacity of Small Bay was estimated as 20 000 t live weight (LW) of oysters Crassostrea gigas, or alternatively 5 100 t LW of mussels Mytilus galloprovincialis, and for Big Bay as 100 000 t LW of oysters. Two production scenarios were investigated for Small Bay: a production of 4 000 t LW y–1 of mussels, and the most profitable scenario for oysters of 19 700 t LW y–1. The main conclusions of this work are: (i) in 2015–2016, both Small Bay and Big Bay were below their maximum production capacity; (ii) the current production of shellfish potentially removes 85% of the human nitrogen inputs; (iii) a maximum-production scenario in both Big Bay and Small Bay would result in phytoplankton depletion in the farmed area; (iv) increasing the production intensity in Big Bay would probably impact the existing cultures in Small Bay; and (v) the production in Small Bay could be increased, resulting in higher income for farmers. 相似文献
2.
Mussel Periostracum from Deep-Sea Redox Communities as a Microbial Habitat: 3. Secondary Inhabitants
Abstract. Vacated microborings in periostracum of live mussels of the Florida Escarpment redox community (depth of 3266 m) become a habitat for a prolific secondary microbiota consisting of a variety of prokaryotic and a few eukaryotic organisms. Periostracum surface is also colonized by diverse microorganisms, dominated by presumed chemolithotrophic bacteria with stacks of intracellular lamellae. Unlike sheltered microflora within borings, the surface community is heavily grazed upon by numerous archaeogastropods and ciliates. 相似文献
3.
《Limnologica》2015
Changes in the vegetation cover associated with intensive forest extermination may have a strong effect on the riverine environment, including the chances of survival for bivalve mollusc populations in small streams and rivers. In order to check this hypothesis, drainage area properties of the rivers with extinct and existing pearl mussel populations in the Russian section of the Baltic Sea basin were compared. Preservation of forest vegetation along the river banks of the studied rivers was correlated with the presence of pearl mussel populations. Traditional agriculture turned out to be, in some cases, more harmful for river ecosystems than urbanization and industrialization. 相似文献
4.
Laser line scan imaging and chirp sub-bottom profiling were used to detail the morphology of a submarine mud volcano and brine-filled crater at 652 m water depth in the northern Gulf of Mexico. The mud volcano has a relief of 6 m and a basal diameter of about 80 m. The feature comprises a central, brine-filled crater (253 m2) surrounded by a continuous bed of methanotrophic mussels (Bathymodiolus childressi) covering 434 m2 and a patchy bed covering an additional 214 m2 of the periphery. The brine pool was mostly <2 m deep, but there were two holes of >28 m and 12 m deep, respectively at the northern end of the pool which emitted continual streams of small clear bubbles. Sub-bottom profiles indicated three distinct strata beneath the present surface of the mud volcano. Integration of 17 profiles shows that the mud volcano has been built in at least three successive stages: the lowest stage deposited 35,400 m3, while the middle and upper stages deposited 7700 and 20,400 m3, respectively. Piston cores were taken at the northern edge of the mussel bed and a site ∼100 m southwest of the pool. Mussel and lucinid shells were recovered from the closer core, lucinid shells from the distant core. A mussel shell from 3.4 m sub-bottom had a Δ14C age of 16.2 ka. Mixture of modern carbon with “carbon dead” reservoir material would produce actual ages ∼2 ka less than the radiocarbon ages. 相似文献
5.
The Chilean lake district includes diverse lentic ecosystems along ca. 700 km of the country (36°–43°S), including the “Nahuelbutan lakes”, “Araucanian lakes” and “Chiloe lakes”. This area is recognized as an important “hot spot” of benthic freshwater biodiversity in Southern South America. In Chilean temperate lakes, increased nutrient loads of P and N caused eutrophication, particularly in the Nahuelbutan Lakes. The freshwater Hyriidae mussel Diplodon chilensis (Gray, 1828) which is one of the most abundant species in Chilean temperate lakes, is known to be very susceptible to eutrophication. This species presents a clear reduction in its geographic ranges and is considered to be a threatened species in many Chilean lakes. In this study, we used a correlative approach to determine how eutrophication-driven changes in the food supply and in geographical parameters of different Chilean lakes affected the shell growth rates of D. chilensis. The results obtained from sclerochronological analyses of the mussel shells suggest an association with a group of environmental variables, including geographical types (negative), such as latitude and altitude, and limnological types (positive), especially phosphorous and turbidity. However, the D. chilensis populations under extreme conditions of turbidity in eutrophic and hypertrophic lakes are extinct or nearly so. The high positive correlation of the mean D. chilensis growth rates with orthophosphate (R=0.76; P<0.05), in relation to dissolved inorganic nitrogen, suggests that P is the major limiting factor of the primary productivity in Chilean temperate lakes. We discuss some implications of our results in terms of the conservation of biodiversity in temperate lake ecosystems at different taxonomic levels. 相似文献
6.
A mechanism of damped oscillations of a coronal loop is investigated. The loop is treated as a thin toroidal flux rope with
two stationary photospheric footpoints, carrying both toroidal and poloidal currents. The forces and the flux-rope dynamics
are described within the framework of ideal magnetohydrodynamics (MHD). The main features of the theory are the following:
i) Oscillatory motions are determined by the Lorentz force that acts on curved current-carrying plasma structures and ii) damping is caused by drag that provides the momentum coupling between the flux rope and the ambient coronal plasma. The
oscillation is restricted to the vertical plane of the flux rope. The initial equilibrium flux rope is set into oscillation
by a pulse of upflow of the ambient plasma. The theory is applied to two events of oscillating loops observed by the Transition Region and Coronal Explorer (TRACE). It is shown that the Lorentz force and drag with a reasonable value of the coupling coefficient (c
d
) and without anomalous dissipation are able to accurately account for the observed damped oscillations. The analysis shows
that the variations in the observed intensity can be explained by the minor radial expansion and contraction. For the two
events, the values of the drag coefficient consistent with the observed damping times are in the range c
d
≈2 – 5, with specific values being dependent on parameters such as the loop density, ambient magnetic field, and the loop
geometry. This range is consistent with a previous MHD simulation study and with values used to reproduce the observed trajectories
of coronal mass ejections (CMEs). 相似文献
7.
从前期构建的短蛸(Octopus ocellatus)c DNA文库中克隆获得了一个短蛸酪氨酸蛋白激酶(Oo Btk)基因的c DNA全长,其c DNA全长1191 bp,包括5’非编码区(UTR)259 bp,3’UTR 227 bp,开放阅读框(ORF)705 bp,编码234个氨基酸,预测理论等电点为8.50,分子量为27.7 k Da。运用实时荧光定量PCR法分析了在健康短蛸的不同组织以及鳗弧菌和藤黄微球菌刺激后血细胞中Oo Btk的表达规律,结果表明:Oo Btk在肌肉、外套膜、鳃、鳃心、系统心脏、肝胰脏、肾囊、胃、性腺和血细胞等各检测组织中均有表达,其中在肝胰脏的表达量最高;短蛸经鳗弧菌和藤黄微球菌刺激后,Oo Btk在血细胞中的表达量呈现出了明显的被诱导表达趋势,在鳗弧菌和藤黄微球菌刺激后6 h表达即增强,并分别在鳗弧菌刺激后48 h和藤黄微球菌刺激后12 h达到最高。Oo Btk参与短蛸对于鳗弧菌和藤黄微球菌刺激的应答过程。 相似文献
8.
P. Foster 《新西兰海洋与淡水研究杂志》2013,47(4):369-379
Ultraviolet absorption spectra of fresh and marine waters along the southern coast of Viti Levu, Fiji, are recorded. Variations in the magnitude of the absorption from streams deyoid of human influence limit the use of such measurements as a sensitive index of organic pollution. However, where there is a significant difference between the absorption magnitudes of adjacent streams, these can be individually identified in coastal waters by concurrent absorption and salinity measurements. Such measurements characterise water masses in inshore waters, and indicate the origin of their freshwater components. Consequently the method has particular relevance in sea areas influenced by fresh waters with enhanced ultraviolet absorbance due to organic pollution. 相似文献
9.
ThisworksupportedbytheScienceandTechnologyCommitteeofShandongProvince.Grant(95)50.INTRODUCTIONManyinvestigationsindicatalthatsupplementation0fsuitableseleniumleveIstolowordefidentinseleniumdietcanpreventoccurrenceofvarioustumots(Chen,l990),enhanceorganisminimneability(Wu,l992),maintainthenormalfunCtion0fheart,liv-er,lungandstomach(Schwarzetal,l957),andisgoodpareuti0nsagainstcardiovascularandcerebrovascu1arproblemsinoldpeople.Seleniumisanessentialtraeeelernentfornonnalhumanlife(Balassa… 相似文献
10.
So MK Zhang X Giesy JP Fung CN Fong HW Zheng J Kramer MJ Yoo H Lam PK 《Marine pollution bulletin》2005,51(8-12):677-687
Concentrations of persistent organic pollutants including polychlorinated biphenyls (PCBs), organochlorine (OC) pesticides and dioxin-like compounds were measured in green-lipped mussels, Perna viridis, collected from seven mariculture zones in Hong Kong between September and October in 2002 in order to evaluate the status, spatial distribution and potential sources of pollution in these areas. Concentrations ranged from 300 to 4400 ng/g lipid weight for total OCs and 170–1000 ng/g lipid weight for total PCBs (based on 28 congeners). Relatively smaller DDT concentrations in mussels compared with previous studies suggest reduced discharges of DDTs from nearby regions into Hong Kong waters. Detection of a mixture of HCH isomers in the mussels indicated that Hong Kong waters were predominantly contaminated by technical HCHs rather than lindane. Mussel samples from all sampling locations elicited significant dioxin-like activity in the H4IIE-luc bioassay. The greatest magnitude of dioxin-like response (39 pg TEQ/g wet wt.) was detected in mussels from Ma Wan in the western waters of Hong Kong, which is strongly influenced by the Pearl River discharge. Human health risk assessment was undertaken to evaluate potential risks associated with the consumption of the green-lipped mussels. Risk quotient (RQ) for dioxin-like compounds was greater than unity suggesting that adverse health effects may be associated with high mussel consumption. 相似文献