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81.
The virtual ecologist approach: simulating data and observers 总被引:3,自引:0,他引:3
Damaris Zurell Uta Berger Juliano S. Cabral Florian Jeltsch Christine N. Meynard Tamara Münkemüller Nana Nehrbass Jörn Pagel Björn Reineking Boris Schröder Volker Grimm 《Oikos》2010,119(4):622-635
Ecologists carry a well‐stocked toolbox with a great variety of sampling methods, statistical analyses and modelling tools, and new methods are constantly appearing. Evaluation and optimisation of these methods is crucial to guide methodological choices. Simulating error‐free data or taking high‐quality data to qualify methods is common practice. Here, we emphasise the methodology of the ‘virtual ecologist’ (VE) approach where simulated data and observer models are used to mimic real species and how they are ‘virtually’ observed. This virtual data is then subjected to statistical analyses and modelling, and the results are evaluated against the ‘true’ simulated data. The VE approach is an intuitive and powerful evaluation framework that allows a quality assessment of sampling protocols, analyses and modelling tools. It works under controlled conditions as well as under consideration of confounding factors such as animal movement and biased observer behaviour. In this review, we promote the approach as a rigorous research tool, and demonstrate its capabilities and practical relevance. We explore past uses of VE in different ecological research fields, where it mainly has been used to test and improve sampling regimes as well as for testing and comparing models, for example species distribution models. We discuss its benefits as well as potential limitations, and provide some practical considerations for designing VE studies. Finally, research fields are identified for which the approach could be useful in the future. We conclude that VE could foster the integration of theoretical and empirical work and stimulate work that goes far beyond sampling methods, leading to new questions, theories, and better mechanistic understanding of ecological systems. 相似文献
82.
Spatial and temporal distribution patterns of the macrozoobenthos assemblage in the salt marshes of Tejo estuary (Portugal) 总被引:1,自引:0,他引:1
The present study focuses on the spatial and temporal distribution of the macroinvertebrate community of the salt marsh areas
of the Tejo estuary, based on surveys conducted from autumn 1998 to summer 2000. Samples were collected quarterly in five
different intertidal areas along an elevation gradient in: mudflats, creek mouths, creeks, pioneer salt marsh areas and middle
marsh areas. A total of 36 benthic invertebrate taxa were identified. Insect larvae were the most well represented group,
with 10 taxa identified. Oligochaetes and ostracods were the most numerically abundant taxa, whereas bivalves dominated in
biomass. Benthic macroinvertebrate assemblages were dominated, both in number and biomass, by deposit feeders. Three distinct
macroinvertebrate assemblages were distinguished along the elevation gradient, based on species presence, density and biomass:
the unvegetated muddy areas with a macrobenthic assemblage composed mostly by infauna; the salt marsh pioneer areas of Spartina maritima in which several epibenthic taxa were found, as well as endobenthic taxa characteristic of muddy sediment; and the creek
margins, with epifauna taxa such as insect larvae and crustaceans and a low abundance of benthic infauna. Total biomass in
the unvegetated and Spartina areas was higher during spring and summer mainly due to the increase in biomass of Scrobicularia plana and Hydrobia ulvae. No decreases in the salt marsh macroinvertebrate biomass values were observed during the highest densities of their potential
nektonic predators (summer). This fact might indicate that macroinvertebrates are not a limiting resource for the nektonic
species, and that the natural biomass increment of these invertebrate species could be masking the predation/disturbance caused
by the nektonic species. 相似文献
83.
The trophic structure of benthic communities in the Tagus estuary and adjacent coastal shelf was characterized according to
a functional guild approach, based on sampling surveys conducted between 1987 and 2000. Macrobenthic organisms were assigned
to seven distinct trophic groups (herbivorous, filter feeders, surface deposit feeders, subsurface deposit feeders, carnivores,
filter feeders/detritivores, carnivores/detritivores) and the dominance of these groups was related to environmental variables
using multivariate ordination techniques. Surface-deposit feeders were numerically dominant in the Tagus estuary, making up
52% of the benthic communities, while in the adjacent coastal shelf the assemblage was dominated by both surface-deposit feeders
and filter feeders (37% and 33%, respectively). When biomass was considered, filter feeders and filter feeders/detritivores
were the dominant groups in the estuary, while for the adjacent coastal shelf filter feeders represented 83% of the total
biomass. Salinity, depth and sediment composition were the main factors structuring spatial distribution. Surface-deposit
feeders were the most abundant macrobenthos of the upper estuary. Surface deposit feeders also dominated the middle and the
lower estuary but the proportion of filter feeders as well as other trophic groups increased with salinity. Generally, a more
even distribution of trophic structure was found at stations with high salinity. In the adjacent coastal shelf, the trophic
diversity decreased with depth. The trophic structure revealed that filter feeders dominated in abundance and biomass in shallow
sandy sediments (<25 m), while in deeper sandy mud and muddy habitats (>50 m to 260 m), deposit feeders and carnivores were
the most important groups in abundance and biomass, respectively. 相似文献
84.
Phytosterols: applications and recovery methods 总被引:5,自引:0,他引:5
Phytosterols, or plant sterols, are compounds that occur naturally and bear close structural resemblance to cholesterol, but have different side-chain configurations. Phytosterols are relevant in pharmaceuticals (production of therapeutic steroids), nutrition (anti-cholesterol additives in functional foods, anti-cancer properties), and cosmetics (creams, lipstick). Phytosterols can be obtained from vegetable oils or from industrial wastes, which gives an added value to the latter. Considerable efforts have been recently dedicated to the development of efficient processes for phytosterol isolation from natural sources. The present work aims to summarize information on the applications of phytosterols and to review recent approaches, mainly from the industry, for the large-scale recovery of phytosterols. 相似文献
85.
Potential mineralization of nitrogen from organic wastes to ryegrass and wheat crops 总被引:8,自引:0,他引:8
Two-pot experiments with ryegrass and wheat plants were conducted in a Cambic Arenosol to test the reliability of N fate predicted by incubation experiments previously performed, with the same soil, to assess potentially mineralizable nitrogen from six organic wastes (municipal solid waste compost, secondary pulp mill sludge, horn meal, poultry manure, solid phase from pig slurry and composted pig manure). Two treatments, corresponding to 80 and 160 kgN/ha were tested, with or without mineral N fertilization. Experimental data obtained in the pot trials was consistent with nitrogen net mineralization trend observed in the aerobic incubations with all the wastes tested. Values of potentially mineralizable nitrogen (N(0)) from the equations obtained by model fitting, to the incubation data, were well correlated to ryegrass and wheat N uptake. Poultry manure was the most efficient N supplier to crops. 相似文献
86.
87.
Dapueto R Castelli R Fernández M Chabalgoity JA Moreno M Gambini JP Cabral P Porcal W 《Bioorganic & medicinal chemistry letters》2011,21(23):7102-7106
Glucose 9 and 2-deoxyglucose 10 were successfully synthesized and radiolabeled with [(99m)Tc(CO)(3)(H(2)0)(3)](+) intermediate in high yield. The complexes were characterized by HPLC and its stability with histidine over time was challenged. Cell uptake and biodistribution studies in melanoma-bearing C57BL/6 mice were performed. Both compounds showed accumulation in tumor tissue with high tumor-to-muscle ratios. Thus, D-glucose- and D-2-deoxyglucose-(99m)Tc complex could be considered as agents for melanoma diagnosis. 相似文献
88.
Kinetics and mechanism of the cutinase-catalyzed transesterification of oils in AOT reversed micellar system 总被引:1,自引:0,他引:1
The kinetics of the enzymatic transesterification between a mixture of triglycerides (oils) and methanol for biodiesel production
in a bis(2-ethylhexyl) sodium sulfosuccinate (AOT)/isooctane reversed micellar system, using recombinant cutinase from Fusarium solani pisi as a catalyst, was investigated. In order to describe the results that were obtained, a mechanistic scheme was proposed,
based on the literature and on the experimental data. This scheme includes the following reaction steps: the formation of
the active enzyme–substrate complex, the addition of an alcohol molecule to the complex followed by the separation of a molecule
of the fatty acid alkyl ester and a glycerol moiety, and release of the active enzyme. Enzyme inhibition and deactivation
effects due to methanol and glycerol were incorporated in the model. This kinetic model was fitted to the concentration profiles
of the fatty acid methyl esters (the components of biodiesel), tri-, di- and monoglycerides, obtained for a 24 h transesterification
reaction performed in a stirred batch reactor under different reaction conditions of enzyme and initial substrates concentration. 相似文献
89.
90.
Lujan Villanueva‐Gomila Alejandro Gatto Karina Cabral Pablo Yorio 《Journal of Field Ornithology》2009,80(4):344-350
ABSTRACT Infanticide and nonfatal aggression by adults toward unfamiliar chicks have been widely reported in colonial birds, and can be an important cause of chick mortality. We studied intraspecific aggression by adults toward chicks at a South American Tern (Sterna hirundinacea) colony in Patagonia, Argentina, during 2005 to characterize this behavior, evaluate its relationship with nesting density, chick age and microhabitat characteristics, and assess its effect on breeding success. Of 111 chicks in the study area, 45% were attacked at least once. Chicks older than 9 d posthatching were more likely to be attacked than younger chicks, and unattended chicks were more likely to be attacked than guarded chicks (88 vs. 12%). Chicks were also attacked more often when in their own territories (76% of cases), but were less likely to be attacked in territories with more vegetation cover and high‐quality shelters (i.e., vegetation with characteristics that prevented adults from reaching chicks). The number of aggression events was not related to nest density. At least 8% of the chicks in our study area died as a result of adult intraspecific aggression. Our results indicate that intraspecific aggression by adult South American Terns toward chicks is relatively common in the Punta Loma colony and should not be underestimated as a factor affecting their breeding success. 相似文献