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731.
Aquatic organisms can use many methods of dispersal among discrete freshwater habitats, and phoresy is an important but poorly understood mechanism. Tank bromeliads are small and unconnected habitats used by many animals, and some of them use phoresy for dispersal. Ostracods living in bromeliads used treefrogs as phoretic hosts for dispersal. We investigated the distribution of phoretic ostracods among body parts of treefrogs (Scinax littoreus and Scinax perpusillus), the prevalence and intensity of ostracods (Elpidium sp.) between Scinax species, and the prevalence and mean intensity of ostracods among the frogs in wet vs. dry seasons in two inselbergs areas at Rio de Janeiro State (Brazil). There were significant differences among the body parts occupied by ostracods and between the Scinax species. Seasonal differences were found only for S. littoreus showing greater abundance during the wet season. Additionally, we record Scinax cuspidatus and Thoropa miliaris as new phoretic hosts for Elpidium sp. to use phoresy. 相似文献
732.
733.
Carlos Rosas Edwin L. Cooper Cristina Pascual Roberto Brito Rolando Gelabert Teresa Moreno Ariadna Sánchez 《Marine Biology》2007,152(4):929-938
To assess the health status of aquatic ecosystems, specialized tools and strategies are needed to study the changes induced
in oceanic systems by human activity. The Gulf of Mexico has a tremendous ecological importance because of its biological
diversity. The present paper defines baseline levels of blood metabolites and immune components for wild tropical populations
of F. duorarum: an important shrimp species of the Gulf of Mexico. Osmotic pressure (OP), osmotic capability (OC), oxy hemocyanin (OxyHc),
glucose, digestive gland glycogen, proteins, cholesterol, lactate, acylglycerols (AG) were used as indicators of physiological
and nutritional status; phenoloxidase activity, quantification of hemocytes, as well as respiratory burst, were used to assess
the immunological status. There were no differences between sexes in either live weight or physiological and nutritional conditions.
Only total blood protein, oxy hemocyanin, and digestive gland glycogen showed normally distributed data. All the remaining
blood parameters were right- or left-skewed. A median live weight of 9.5 g was registered for the sampled population. Median
values of 955 and −91.85 mOsm/kg (OP and OC, respectively) were obtained, indicating that shrimp were slightly hypo-osmotic
in relation to sea water. A proportion of 27% of OxyHc of the total protein (OxyHc/Prot) was calculated for the F. duorarum population. ProPO and PO showed no normal distribution and were not different between sexes. A right-skewed distribution was
observed. Total hemocytes, hyaline (HC) and granular cells (GC) showed differences between sexes, with higher values in females
than males. A similar proportion of HC (69%) and GC (30%) of total cells were observed between sexes. Basal and activated
respiratory burst showed differences between sexes with higher values for females than for males. The current results provide
indicators of the nutritional and immune status of F. duorarum that can be used to detect changes in trophic relations and health at a population level. 相似文献
734.
735.
Norma A. Estrada Nestor Lagos Carlos García Alfonso N. Maeda-Martínez Felipe Ascencio 《Marine Biology》2007,151(4):1205-1214
Juvenile Pacific giant lions-paw scallops Nodipecten subnodosus were fed the toxic dinoflagellate Gymnodinium catenatum, a producer of paralytic shellfish poison (PSP), supplied with Isochrysis galbana (a nontoxic microalgae). Short-term (<24 h) experiments were performed to determine clearance and ingestion rates of G. catenatum. Kinetics of PSP was examined in longer-term experiments (>2 days). At high food concentrations, juvenile scallops showed
production of pseudofeces, partial shell valve closure, and reduction in feeding. According to HPLC analysis, the only toxins
present in the dinoflagellate G. catenatum and in the scallops were the gonyautoxins (GTXs), except in the labial palps and digestive gland, where trace amounts of
saxitoxin (STX) were present in scallops. These tissues could play an important role in toxin biotransformation. The ranking
of toxin concentration in tissues was: digestive gland > labial palps > intestine > gills > mantle > adductor muscle, where
the total contribution of viscera was more than 80% of the total toxin body burden. Juvenile scallops exhibited no apparent
detrimental physiological responses during the long-term feeding experiment. The dinoflagellate may contribute nutrients to
the scallop, in addition to the microalgae I. galbana. The dinoflagellate may enhance cell uptake and byssus production. Once PSP accumulated during the first 12 days, it was
slowly eliminated. The limited capacity for accumulating toxins in the adductor muscle favors domestic marketing of scallops. 相似文献
736.
Ulises Diéguez-Aranda Fernando Castedo Dorado Juan Gabriel Álvarez González Alberto Rojo Alboreca 《Ecological modelling》2006
In this study we developed a dynamic growth model for Scots pine (Pinus sylvestris L.) plantations in Galicia (north-western Spain). The data used to develop the model were obtained from a network of permanent plots, of between 10 and 55-year-old, which the Unidade de Xestión Forestal Sostible (Sustainable Forest Management Unit) of the University of Santiago de Compostela has set up in pure plantations of this species of pine in its area of distribution in Galicia. In this model, the initial stand conditions at any point in time are defined by three state variables (number of trees per hectare, stand basal area and dominant height), and are used to estimate stand volume, classified by commercial classes, for a given projection age. The model uses three transition functions expressed as algebraic difference equations of the three corresponding state variables used to project the stand state at any point in time. In addition, the model incorporates a function for predicting initial stand basal area, which can be used to establish the starting point for the simulation. This alternative should only be used when the stand is not yet established or when no inventory data are available. Once the state variables are known for a specific moment, a distribution function is used to estimate the number of trees in each diameter class, by recovering the parameters of the Weibull function, using the moments of first and second order of the distribution (arithmetic mean diameter and variance, respectively). By using a generalized height–diameter function to estimate the height of the average tree in each diameter class, combined with a taper function that uses the above predicted diameter and height, it is then possible to estimate total or merchantable stand volume. 相似文献
737.
Juan Carlos Alonso Luis M. Bautista Javier A. Alonso 《Behavioral ecology and sociobiology》1997,40(6):401-408
We studied the behavior of 13 radiotagged cranes dispersing from a communal roost over days when they changed their main
daily foraging area between consecutive days during two winter seasons. Individuals went to a new foraging zone when on the
previous day their morning food intake had fallen below their mean morning food intake measured over the whole winter. Food
intake on the day before a change in foraging area was positively correlated with dominance rank. Dominant cranes changed
to new zones with higher numbers of birds and food density, while subordinate cranes went to new zones with lower numbers
of birds. As a result, all birds increased their food intake over that of the previous day. Dominant cranes remained more
faithful to their most preferred foraging zone, where they spent 69% of the mornings, while subordinate birds were more mobile,
switching among zones frequently. Dominant birds left the roost later than subordinate birds on the days they changed to a
new zone, which could be used to track the main departing flows. The results suggest that the dynamics that led to a truncated
phenotype-limited distribution were determined by social dominance and food abundance, with dominant cranes shifting to a
new zone to maintain their high intake levels and subordinates changing more frequently whenever their daily intake did not
reach the minimum metabolic requirements.
Received: 16 December 1996 / Accepted after revision: 22 February 1997 相似文献
738.
Carlos Molinet Edwin Niklitschek Carlos A. Moreno Alejandra Arévalo 《Marine Biology》2008,153(5):779-787
The transport of marine invertebrate larvae is strongly influenced by their distribution in the water column, which could
be affected by the biological features of the larvae and environmental variables. Larvae can modify their swimming behavior
throughout their planktonic cycle, thereby changing the observed distributional patterns. This ability, coupled with oceanographic
features, could induce landward or seaward transport. We studied the vertical distribution of C. concholepas larval stages in two differently stratified systems in Chilean inland seas; Refugio Channel (a strongly stratified channel,
where previously has been described as a frontal system) and Guaitecas (a gently stratified system). Combinations of 12–24 h
larval collection experiments were done simultaneously with fixed temperature and salinity profiles; meteorological data were
also obtained. The results suggest that both salinity and day period influence the C. concholepas distributional patterns in the water column. Early veliger and competent larvae are concentrated in different parts of the
water column, probably related to their transport capacities. The upper layer of the water column at the Refugio site, unlike
the Guaitecas site, showed a stratified regime, which could affect larval density and larval length between the two sites.
Finally, our results suggest that Refugio may be a sink habitat for C. concholepas. 相似文献
739.
740.
Maurizio Pettine Silvio Capri Maria Giuseppina Farrace Maura Manganelli Luisa Patrolecco Alberto Puddu Annamaria Zoppini 《Chemistry and Ecology》2002,18(1):13-25
The results obtained in the four seasonal cruises planned in the PRISMA II project are reported. These concern dissolved and colloidal organic carbon, free amino acids and total dissolved carbohydrates and heterotrophic activity. Main factors controlling organic matter degradation, resulting from laboratory tests not planned in the above project, are also discussed. Dissolved organic matter shows seasonal accumulation, which may be markedly different from year to year, and large contributions by colloidal and saccharide components. Heterotrophic activities play an important role in the carbon cycle, although laboratory runs highlight limitations caused by aging of organic matter and phosphorus deficiency. 相似文献