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991.
The effects of light exposure on the photosynthetic activity of kleptoplasts were studied in the sacoglossan mollusc Elysia viridis. The photosynthetic activity of ingested chloroplasts was assessed in vivo by non-destructively measuring photophysiological
parameters using pulse amplitude modulation (PAM) fluorometry. Animals kept under starvation were exposed to two contrasting
light conditions, 30 μmol photons m−2 s−1 (low light, LL), and 140 μmol photons m−2 s−1 (high light, HL), and changes in photosynthetic activity were monitored by measuring the maximum quantum yield of photosystem
II (PSII), F
v/F
m, the minimum fluorescence, F
o, related to chlorophyll a content, and by measuring rapid light-response curves (RLC) of relative electron transport rate (rETR). RLCs were characterised
by the initial slope of the curve, αRLC, related to efficiency of light capture, and the maximum rETR level, rETRm,RLC, determined by the carbon-fixation metabolism. Starvation induced the decrease of all photophysiological parameters. However,
the retention of photosynthetic activity (number of days for F
v/F
m > 0), as well as the rate and the patterns of its decrease over time, varied markedly with light exposure. Under HL conditions,
a rapid, exponential decrease was observed for F
v/F
m, αRLC and rETRm,RLC, F
o not showing any consistent trend of variation, and retention times ranged between 6 and 15 days. These results suggested
that the retention of chloroplast functionality is limited by photoinactivation of PSII reaction center protein D1. In contrast,
under LL conditions, a slower decrease in all parameters was found, with retention times varying from 15 to 57 days. F
v/F
m, αRLC and rETRm,RLC exhibited a bi-phasic pattern composed by a long phase of slow decrease in values followed by a rapid decline, whilst F
o decayed exponentially. These results were interpreted as resulting from lower rates of D1 photoinactivation under low light
and from the gradual decrease in carbon provided by photosynthesis due to reduction of functional photosynthetic units. 相似文献
992.
Classical sampling methods often miss important components of coral reef biodiversity, notably organisms that remain sheltered
within the coral matrix. Recent studies using sea kraits (sea snakes) as bio-indicators suggest that the guild of predators
represented by anguilliform fish (Congridae, Muraenidae, Ophichthidae, henceforth “eels” for simplicity) were far more abundant
and diverse than previously suspected. In the current study, eel diversity (similarity and species richness indices) estimated
via sea snake sampling (SSS) was compared among six areas of one of the main oceanic biodiversity hotspot of the Pacific Ocean
(southwest lagoon of New Caledonia). Based on the eel diversity in the snakes’ diet, the results obtained in six areas, in
two snake species, and using different estimates (ANOSIM, Shannon index…) were consistent, suggesting that SSS provided robust
information. Analyses also suggested subtle, albeit significant, differences in the eel assemblages among islets. Such spatial
differences are discussed in light of local management practices. As SSS is easy to use, cost-effective, and provides the
best picture of eel assemblages to date, it can be employed to monitor the eel assemblages in addition to the snakes themselves
in many areas of the Indo-Pacific Ocean, thereby providing an index of the top predator biodiversity of many coral reefs. 相似文献
993.
Most marine benthic macroinvertebrate species reproduce via a larval phase but attempts to explain the occurrence of different
larval strategies (feeding or non-feeding, pelagic or benthic) in different habitats have been largely inconclusive. There
have been very few year-round surveys of meroplankton at any latitude and in consequence fundamental data on the diversity,
abundance, and timings of larval life history phases are lacking. There has been considerable debate regarding the viability
of pelagic larvae in cold waters with highly seasonal primary production but there has been only one year-round study of meroplankton
in the Southern Ocean, and that was outside of the Antarctic Circle. We present data from the first year-round survey of meroplankton
assemblages at a location within the Antarctic Circle. We surveyed abundances of meroplanktonic larvae over 1.5 year at Rothera
Point, West Antarctic Peninsula (67°34′S, 68°07′W). Larvae were collected in monthly diver-towed net samples close to the
seabed at 20 and 6 m total water depths at each of three locations and were identified and counted live immediately after
sampling. A total of 99 operationally defined taxonomic types representing 11 phyla were recorded but this is likely to be
an underestimate of true diversity because of inherent difficulties of identification. Larvae were present in all months of
the year and although planktotrophic larvae were more abundant in summer, both feeding and non-feeding types were present
in all months. Comparisons of seasonal larval abundances with data from a settlement study at the same sites and from the
literature show that larvae of mobile adults settle in summer regardless of developmental type, whereas sessile taxa settle
in all seasons. We suggest that this is a consequence of differences in the food requirements of mobile and sessile fauna
and that the availability of food for post-larval juveniles is more critical for survival than factors affecting the larval
stage itself. 相似文献
994.
A series of experiments investigated the potential role of microbial mats in nutrition of the early settlement stages of Penaeus semisulcatus. From 3 days post-metamorphosis, the microbial mat supported high growth and survival rates in postlarvae, equivalent to
that supported by a control diet of Artemia nauplii and mussel. Examination of gut contents indicated that benthic postlarvae feed indiscriminately on the microbial
mat. However, when postlarvae were fed separated size-fractions of the microbial mat, only the fraction containing a high
concentration of infauna (mainly nematodes) was able to support the same growth as intact microbial mat. This appears to be
due to the low nitrogen content (0.4–0.9 mmol g−1) of the various size-fractions, compared to that of infauna (4.0 mmol g−1). The stable isotope composition of the dietary size-fractions and postlarval shrimp tissue supports the hypothesis that
the shrimp assimilated C and N primarily from the associated infauna. This may be due to selective feeding that is not apparent
from stomach contents, due to rapid digestion of fauna soft tissues, or to differential assimilation of infaunal prey relative
to other microbial mat components. The results demonstrate that microbial mats may support survival and growth in early-stage
penaeid shrimp postlarvae on intertidal mud flats. 相似文献
995.
Genetic diversity and population structure of the Chinese mitten crab <Emphasis Type="Italic">Eriocheir sinensis</Emphasis> in its native range 总被引:1,自引:0,他引:1
Liying Sui Fumin Zhang Xiaomei Wang Peter Bossier Patrick Sorgeloos Bernd Hänfling 《Marine Biology》2009,156(8):1573-1583
The Chinese mitten crab Eriocheir sinensis is an indigenous and economically important species in China, but can also be found as invasive species in Europe and America.
Mitten crabs have been exploited extensively as a food resource since the 1990s. Despite its ecological and economic importance,
the genetic structure of native mitten crab populations is not well understood. In this paper, we investigated the genetic
structure of mitten crab populations in China by screening samples from ten locations covering six river systems at six microsatellite
loci. Our results provide further evidence that mitten crabs from the River Nanliujiang in Southern China are a genetically
differentiated population within the native range of Eriocheir, and should be recognized as a separate taxonomic unit. In contrast, extremely low levels of genetic differentiation and
no significant geographic population structure were found among the samples located north of the River Nanliujiang. Based
on the reproductive biology of mitten crabs and the geography of their habitat we argue that both natural and human-mediated
gene flow are unlikely to fully account for the similar allele frequency distributions at microsatellite loci. Large population
sizes of mitten crabs suggest instead that a virtual absence of genetic drift and significant homoplasy of microsatellite
alleles have contributed to the observed pattern. Furthermore, a coalescent-based maximum likelihood method indicated a more
than two-fold lower effective population size of the Southern population compared to the Northern Group and low but significant
levels of gene flow between both areas. 相似文献
996.
Physical shelter features (e.g. shape, size and substrate slope) were tested in the laboratory to evaluate the preferences
of juveniles of European spiny lobster, Palinurus elephas. Tethering experiments to assess whether substrate slope affects the vulnerability of juveniles to predation were also performed.
Our results showed that: (1) semi-circular dens were significantly preferred over square and circular shapes; (2) when not
disturbed by a predator, lobsters sheltered in holes with a diameter closely related to their own size, while in the presence
of a potential predator lobsters showed no significant preference for a particular shelter size; (3) lobsters significantly
preferred dens excavated on sub-vertical (35°) substrates over those excavated on vertical ones (90°); (4) individual lobsters
tethered on vertical substrates were subject to greater predation activity than those tethered on horizontal structures. In
conclusion, the present study contributes to the understanding of how physical properties of shelters affect the choice of
P. elephas juveniles, enhancing their protection and survival rate. 相似文献
997.
Coral sand beaches harbor gobiid sand darts (genus Kraemeria), the only fish known to live in the sand throughout their adult life. Despite the uniqueness of sand-dwelling habitat as
a vertebrate, the biology of this fish remains unclear. To explore how this unique fish utilize an unusual habitat, we investigated
diurnal patterns of microhabitat use and prey consumption by the transparent sand dart, Kraemeria cunicularia, at a sandy beach on Iriomote Island, the Ryukyu Archipelago, Japan. Sand darts were found in sediment in the lower intertidal
zone throughout the daytime regardless of changes in tidal level, whereas at nighttime these fish were found swimming. Gut
content analyses revealed that the sand dart diet was dominated by harpacticoid copepods throughout the day. Analyses of meiobenthic
distribution indicated that these copepods were most abundant at lower intertidal zones where highest numbers of sand darts
were found during the daytime; thus, it is possible that microhabitat use of the fish is largely determined by food availability.
An extensive distributional survey throughout the Ryukyu Archipelago further indicated that sand darts prefer sandy beaches
with well-sorted, coarse sand. These results provide novel insights into how sand darts respond to the tidal rhythm and highlight
putative key environmental factors that determine their distribution at both regional and microhabitat scales.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
998.
Simon Anthony Morley Koh Siang Tan Robert W. Day Stephanie M. Martin Hans-O. Pörtner Lloyd S. Peck 《Marine Biology》2009,156(10):1977-1984
The upper thermal limits for burrowing and survival were compared with micro-habitat temperature for anomalodesmatan clams:
Laternula elliptica (Antarctica, 67°S); Laternula recta, (temperate Australia, 38°S) and Laternula truncata (tropical Singapore, 1°N). Lethal limits (LT50) were higher than burrowing limits (BT50) in L. elliptica (7.5–9.0 and 2.2°C) and L. recta (winter, 32.8–36.8 and 31.1–32.8°C) but the same range for L. truncata (33.0–35.0 and 33.4–34.9°C). L. elliptica and L. truncata had a BT50 0.4 and 2.4–3.9°C, respectively, above their maximum experienced temperature. L. recta, which experience solar heating during midday low tides, had a BT50 0.7–2.4°C below and a range for LT50 that spanned their predicted environmental maximum (33.5°C). L. recta showed no seasonal difference in LT50 or BT50. Our single genus comparisons contrast with macrophysiological studies showing that temperate species cope better with elevated
temperatures.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
999.
Network structure and parasite transmission in a group living lizard,the gidgee skink, <Emphasis Type="Italic">Egernia stokesii</Emphasis> 总被引:1,自引:1,他引:0
Stephanie S. Godfrey C. Michael Bull Richard James Kris Murray 《Behavioral ecology and sociobiology》2009,63(7):1045-1056
Gidgee skinks (Egernia stokesii) form large social aggregations in rocky outcrops across the Flinders Ranges in South Australia. Group members share refuges
(rock crevices), which may promote parasite transmission. We measured connectivity of individuals in networks constructed
from patterns of common crevice use and observed patterns of parasitism by three blood parasites (Hemolivia, Schellackia and Plasmodium) and an ectoparasitic tick (Amblyomma vikirri). Data came from a 1-year mark-recapture study of four populations. Transmission networks were constructed to represent possible
transmission pathways among lizards. Two lizards that used the same refuge within an estimated transmission period were considered
connected in the transmission network. An edge was placed between them, directed towards the individual that occupied the
crevice last. Social networks, a sub-set of same-day only associations, were small and highly fragmented compared with transmission
networks, suggesting that non-synchronous crevice use leads to more transmission opportunities than direct social association.
In transmission networks, lizards infested by ticks were connected to more other tick-infested lizards than uninfected lizards.
Lizards infected by ticks and carrying multiple blood parasite infections were in more connected positions in the network
than lizards without ticks or with one or no blood parasites. Our findings suggest higher levels of network connectivity may
increase the risk of becoming infected or that parasites influence lizard behaviour and consequently their position in the
network.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
This contribution is part of the special issue “Social Networks: new perspectives” (Guest Editors: J. Krause, D. Lusseau and
R. James). 相似文献
1000.
Hierarchical perception of fertility signals and nestmate recognition cues in two dolichoderine ants
Laurent Cournault Jean-Christophe de Biseau 《Behavioral ecology and sociobiology》2009,63(11):1635-1641
In social insects, queens are likely to “honestly” inform their nestmates of their presence and fertility status through pheromonal
communication. Cuticular hydrocarbons (CHCs) have been reported to be effective nestmate discriminators and strongly suspected
to act as fertility signals, at least in some species. The use of the same chemical bouquet (i.e., the CHC profile) to convey
two fundamentally different information seems puzzling. However, a recent threshold model proposes a hierarchy in the discriminating
processes, i.e., fertility signals can only be perceived if nestmate recognition has been reached (Le Conte and Hefetz, Annu
Rev Entomol 53:523–542, 2008). Here, we developed a simple behavioral bioassay based on chemical recruitment toward a queen placed outside the nest in
two dolichoderine ants (Linepithema humile and Tapinoma erraticum), which allowed us to investigate the interplay between fertility signaling and colonial recognition. Using queen corpses
of various origins (nestmates or aliens) and physiological states (fertile or infertile; mated or unmated), we demonstrated
that nestmate recognition cues clearly override fertility signals under our experimental conditions. Indeed, while nestmate
infertile queens were largely ignored by the workers, nestmate fertile queens (mated or not) induced worker recruitment, whereas
alien fertile queens did not and were aggressed by the workers. 相似文献