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91.
Temperate estuaries are indispensable as refuelling areas for long-distance shorebirds, where they depend on intertidal benthic fauna, such as bivalves, as food source. Bivalve recruitment is thought to be, at least partly, top-down regulated by epibenthic predators (the shrimp Crangon crangon and the crab Carcinus maenas) but this interaction is part of a complex predator–prey system since various fish species prey upon the crustaceans. 相似文献
92.
Eduardo Alves de Almeida Afonso Celso Dias Bainy Ana Paula de Melo Loureiro Glaucia Regina Martinez Sayuri Miyamoto Janice Onuki Lívea Fujita Barbosa Camila Carrio Machado Garcia Fernanda Manso Prado Graziella Eliza Ronsein Carlos Alexandre Sigolo Cludia Barbosa Brochini Ana Maria Gracioso Martins Marisa Helena Gennari de Medeiros Paolo Di Mascio 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2007,146(4):588
Oxidative stress can take place in marine bivalves under a series of environmental adverse conditions. The study of different systems related to oxidative stress in these organisms can give important information about their physiological status and also about environmental health. Bivalves have been proposed as good sentinel organisms in pollution monitoring studies through the analysis of biochemical biomarkers, and most of the biomarkers analyzed are those related to oxidative stress. However, it is very important to know how other environmental factors not associated to the presence of pollutants might affect these parameters. We have studied a series of mechanisms related to oxidative stress in mussels which inhabit the Brazilian coast, especially in Perna perna species, subjected to different stress conditions, such as the exposure to different contaminants in the laboratory and in the field, the exposure of mussels to air and re-submersion, simulating the tidal oscillations, and in mussels collected at different seasons. Both oxidative damage levels and antioxidant defense systems were strongly affected by the different environmental stress. This review summarizes the data obtained in some studies carried out in bivalves from the Brazilian coast. 相似文献
93.
Adam Tomašových 《Palaeogeography, Palaeoclimatology, Palaeoecology》2006,235(4):355-381
Although actualistic live/dead comparisons lead to robust estimates of fidelity of modern death assemblages, quantitative evaluation of fidelity of fossil assemblage remains uncertain. In this paper, effects of storm reworking on compositional fidelity of the Upper Triassic shell concentrations (Eastern Alps, Austria) are evaluated. An exploratory approach is based on comparison of reworked and non-reworked assemblages in ordination analyses. Non-reworked assemblages of one or more communities provide a baseline for evaluation of fidelity of reworked assemblages. In siliciclastic-rich intervals of the Kössen Formation, shell concentrations are represented by (1) packstones with small, shallow infaunal bivalves, (2) floatstones and pavements with large semi-infaunal bivalves, and (3) bioclastic marlstones. In carbonate-rich intervals, bioclastic floatstones with bivalves and brachiopods occur. Analyzing all shell concentrations, eight sample groups sharing similar species composition are discriminated. Limited effect of storm reworking on composition of shell concentrations is indicated by (1) a general persistence of six sample groups when only non-reworked assemblages are analyzed, (2) similarity in composition between reworked and non-reworked assemblages within sample groups, and (3) compositional segregation between non-reworked assemblages of distinctive sample groups, mostly without any reworked assemblages of intermediate composition.Depth-related variations in dead-shell production, shell destruction and body size governed preservation and distribution of the shell concentrations along onshore-offshore gradient in the Kössen Basin. First, at times when environmental conditions were unfavorable for shell producers, coupled with high background shell destruction rates, limestone beds formed during storm events were shell-poor. Second, less common shell concentrations in upper than in lower parts of siliciclastic intervals can be related to higher environmental stress in shallower habitats. Third, the difference between shell concentrations dominated by small and large bivalves is driven by between-habitat differences in body size and is not due to a differential sorting of small and large shells. Combining community analysis based on species abundances with taphonomic analysis can thus be helpful in tracking fidelity of fossil assemblages. 相似文献
94.
Disseminated neoplasia (DN) was one of the most important pathological conditions found in cultured flat oysters (Ostrea edulis) from different geographical origins grow in Galicia (NW Spain), during a two years selective breeding programme to produce oysters less susceptible to bonamiosis. Histological characteristics observed in oysters affected by DN included intense infiltration of connective tissue of various organs (gills, stomach, digestive gland and gonad) by large undifferentiated cells, with a large nucleus and a high nucleus-to-cytoplasm ratio. The main ultrastructural features were predominance of euchromatin over heterochromatin that was arrayed in small clumps in the nucleus, prominent granular nucleolus, swollen mitochondria with few cristae and high number of free ribosomes in the cytoplasm. A seasonal pattern of DN prevalence was detected, with higher values in spring-summer, but there were no significant differences between geographic origins or families within these origins. However, the intensity of the disease was significantly different between origins; oysters originating outside of Galicia (particularly those originating from Ireland) were more susceptible to develop advanced DN. DN (8%) and bonamiosis (4.9%) were found concurrently in oysters. The nature and significance of this association warrants more investigation to determine its importance, if any. 相似文献
95.
G. van den Thillart G. van Lieshout K. Storey P. Cortesi A. de Zwaan 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1992,162(4):297-304
Summary The oxygen consumption rate of Scapharca inaequivalvis measured under normoxic conditions over 48 h showed a significant daily cycle with lowest values occurring shortly after the dark period; all hypoxia exposure experiments were carried out during the declining part of the cycle. Animals were exposed to a constant level of hypoxia for a 12-h period in a series of 14 experiments, each at a different oxygen tension. The oxygen consumption was measured continuously, and the extent of accumulation of end-products (succinate and propionate), and the inhibitory effect of adenosine triphosphate on phosphofructokinase were determined at the end of exposures. All three parameters (oxygen consumption, end-product accumulation, phosphofructokinase inhibition) showed a remarkable correlation with major changes occurring between 2.5 and 1.5 ppm (7 and 4 kPa) O2. The oxygen consumption rates showed a drop to 6% of the normoxic rate, but a consistent low consumption remained below 2 ppm (5.5 kPa) which partly recovered over the 12-h exposure period by about three-fold. Succinate and propionate accumulated progressively between 2.5 and 1.5 ppm (7 and 4 kPa); at [O2]<1.5 ppm (4kPa) the concentration did not increase further, indicating that anaerobic metabolism had reached a maximum. Over the same range, phosphofructokinase showed an increased sensitivity for adenosine triphosphate, the lower inhibitor concentration at 50% V
max value pointing to depression of glycolytic rate. Despite the activation of anaerobic metabolism and the evident depression of aerobic metabolism, simple calculation demonstrates that Scapharca inaequivalvis relies mainly on aerobic metabolism even during severe hypoxia. It is assumed that the occurrence of haemoglobin in this species is essential for its capacity to survive long periods of hypoxia.Abbreviations ATP
adenosine triphosphate
- I50
inhibitor concentration at 50% V
max
- PFK
phosphofructokinase
-
P
c
critical PO2
- SEM
standard error of mean
-
VO2
oxygen consumption rate
- ww
wet weight 相似文献
96.
Nabil A. Bayakly Lewis E. Deaton 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1992,162(5):463-468
Summary The ventricle of the mussel Geukensia demissa is inhibited by 5-hydroxytryptamine and excited by the molluscan neuropeptide FMRFamide. Supra-threshold doses of amide result in marked positive chronotropy and inotropy within 5–15 s. 5-Hydroxytryptamine at 10-8
M produces diastolic arrest within 10 s. A 1-min exposure to FMRFamide (5 · 10-8
M) results in a small increase in the cytoplasmic levels of adenosine 3,5-cyclic monophosphate; shorter or longer exposures have no effect. The cAMP content of ventricles incubated in 5 · 10-8
M 5-hydroxytryptamine for 1 min decreases by 2.3 pmol/mg protein; longer or shorter incubations have no effect. Treatment with forskolin results in 3-or 4-fold increases in adenosine 3,5-cyclic monophosphate, but forskolin has no effect on the mechanical activity of the ventricle. The levels of inositol monophosphate, inositol 1,4-diphosphate, and inositol 1,4,5-triphosphate in tissues exposed to 5-hydroxytryptamine are not different from levels in control tissues. FMRFamide decreases the levels of these phosphoinositides by 50% or more. Lower concentrations of phorbol 12,13-diacetate (10-8 to 10-7
M) and phorbol 12-myristate, 13-acetate (10-6
M) cause positive chronotropy in the isolated ventricle; higher concentrations induce systolic arrest. These results suggest that the effects of 5HT on the ventricle are not mediated by adenosine 3,5-cyclic monophosphate or inositol 1,4,5-triphosphate. The effects of FMRFamide may involve a decrease in inositol 1,4,5-triphosphate. The effects of amide may involve a decrease in inositol 1,4,5-triphosphate. The response of the ventricles to phorbol esters suggest that protein kinase C may be involved in the regulation of cardiac contractility.Abbreviations cAMP
adenosine 3,5-cyclic monophosphate
- DMA
dimethylformamide
- DMSO
dimethylsulfoxide
- FMRFamide
Phenylalanyl-methionyl-arginyl-phenylalanylamide
- 5HT
5-hydroxytryptamine
- IP
inositol monophosphate
- IP2
inositol 1,4-diphosphate
- IP3
inositol 1,4,5-triphosphate
- PDA
phorbol 12,13-diacetate
- PMA
phorbol 12-myristate, 13-acetate
- SW
sea water
Present address: MSU; E.M. Center, Memphis, TN 38152, USA 相似文献
97.
Zhang P. Q. Wang W. Q. Lu X. L. Chen C. Y. Dong J. H. 《Biological trace element research》1999,(1):317-323
The content of 34 elements was determined in tissue samples of several marine bivalve species collected from various sites
in the Jiaozhou Bay. The scope of the study was to determine the most suitable bivalve species to be used for environmental
biomonitoring and to evaluate the environmental status of the bay. Clams exhibited higher elemental contents than oysters
and they are the major marine bivalve species in the Jiaozhou Bay; therefore, we consider clams to be more suitable than oysters
as bioindicators for evaluating the environmental status of the area. Increased elemental levels in clam tissues indicate
polluted sites. Also, increased elemental levels in mussels point to possible pollution from tourism development at one selected
site. 相似文献
98.
The oxygen and carbon isotopic compositions of 108 modern shells of various bivalve species collected from cold seeps and hydrothermal vents were investigated in order to evaluate whether these parameters can provide information on environmental geochemical variability as well as on bivalve species and on the type of symbiotic bacteria present in their gills. The results show that the carbonate of bivalve shells from hydrothermal vents is characterized by abnormal positive δ13C values due to kinetic isotope effects, whereas the carbonate of bivalve shells from cold seeps exhibits positive as well as negative δ13C values suggesting that oxidized methane emitted by the seeping fluids may be incorporated in the shell. Comparison of the δ18O and δ13C values of bivalve shells hosting different chemosymbiotic bacteria suggests that each type of symbiosis is associated with a specific environment and bivalve species, indicating that there is a strong physiological/metabolic control on the incorporation of stable isotopes during the biomineralization process. 相似文献
99.
文蛤微卫星DNA的筛选及其特性分析 总被引:5,自引:0,他引:5
采用磁珠富集分离法从文蛤(Meretrix meretrix)的基因组中筛选得到49条微卫星DNA序列,其中两碱基重复有3种类型36个序列,四碱基重复有14种类型26个序列.重复次数在5~30之间的序列占75.6%,30次以上重复的序列占24.4%,最高重复次数为100.根据重复单元的排列特点,完美型、非完美型及混合型序列所占比例分别为61.2%、14.5%和24.5%.本研究中构建的文蛤微卫星文库将在文蛤种质资源评价及分子遗传学研究中发挥作用. 相似文献
100.
Bioclastic accumulations often occur on top of Tethysian carbonate platforms and crinoids are a common constituent of these
bioclastic deposits on Lower and Middle Liassic carbonate platforms. In contrast, the relevant literature contains few examples
in which the main constituent of the lumachels is thin-shelled bivalves (filaments). This paper presents a study of a filament
lumachelle cropping out on top of a Middle Jurassic carbonate platform. The carbonate platform is represented by the Jabalcuz
Formation, found in one of the northernmost Subbetic units (south of Jaén city). The lumachelle marks the demise of the carbonate
platform and has special features that characterize the drowning phase. This process has been related with the syn-rift extensional
tectonics associated to the opening of the Tethys westwards. Stratigraphically, the lumachelle occurs on top of shallow-water
oolite limestones (Middle Jurassic) and is overlain by radiolarian-rich pelagic and resedimented deposits (Latest Callovian–Oxfordian).
It occurs as a body (about 1.5 km wide and up to 8 m thick) made up entirely of densely packed thin bivalve shells. A remarkable
feature of the bivalve shell beds is stromatolite-like crumpled lamination at the outcrop. The observations made at the outcrop
scale, by microscope under transmitted light, and by cathodoluminiscence favor a diagenetic origin for this striking structure.
Other hypotheses, such as its possible relation with seismicity, cannot be confirmed. The filaments would have filled one
of the former basins that originated in relation with syn-rift fault-block tectonics leading to the demise of the carbonate
platform. Tectonics was one of the main factors setting in motion a carbonate productivity crisis and the inhibition of a
diverse benthic community. Once production failed in the carbonate factory, storms and probably hurricanes as well, swept
shell deposits from the shallowest areas of the shallow-water carbonate platform and accumulated them in a coevally formed
small half-graben basin. At least three main depositional stages can be differentiated in the fill of this half-graben basin,
which was a sediment trap for the accumulation and preservation of the tiny bivalve shells against ebb surges. The massive
accumulation of valves, the shortage of micrite around the filaments, outcrop morphology and facies relationships, along with
regional geology, are among the arguments supporting this interpretation. 相似文献