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971.
Northern and Spotted Wolffishes (Anarhichas denticulatus and A. minor) are demersal marine fishes listed as “threatened” in Canadian waters. Both species have unusually large benthic eggs and
large size at hatch, which should reduce passive dispersal. We examined population differentiation with microsatellite and
AFLP loci across the ranges of both species in the North Atlantic Ocean. Although significant population structure was documented,
differentiation was less than expected based on knowledge of life history characteristics. Significant differentiation was
found in Northern Wolffish between the Barents Sea and other samples based on both microsatellite and AFLP data. In contrast,
population structure in the Spotted Wolffish was notably weaker, particularly with microsatellites. Both species were characterized
by low genetic diversity for marine fishes and had significantly lower genetic diversity than the congeneric Atlantic Wolffish.
This finding was consistent with the conservation status of these three species and suggests potential vulnerability to over-exploitation
in Northern and Spotted Wolffishes. 相似文献
972.
The feeding ecology of Merluccius hubbsi was investigated in 2 regions of SE Brazil. The major food sources for the hakes were fish, crustaceans, and squid. In the
upwelling system of Cabo Frio, the diet was very similar in the summers of 2001/2002 and spring 2002; fish were the most important
prey followed by crustaceans. In Ubatuba, euphausiids were an important prey during the winter 2001 (100 m), while in the
summer 2002, fish and amphipods predominated in the diet in the shallower site (40 m) and squid in the deeper site (100 m).
The hakes showed temporal differences in stable isotope signatures in both regions, while C:N ratios varied only in Cabo Frio.
δ15N and δ13C (bulk and corrected for lipid content) increased with fish length, which seems to be related to the increasing importance
of fish and decreasing importance of euphausiids and amphipods in the diet of larger hakes. The mean trophic level of 3.7
for M. hubbsi was estimated using δ15N of bivalves as baseline and the fractionation of 3.4‰ between trophic levels. 相似文献
973.
Anthony J. Gaston Paul A. Smith Laura McFarlane Tranquilla William A. Montevecchi David A. Fifield H. Grant Gilchrist April Hedd Mark L. Mallory Gregory J. Robertson Richard A. Phillips 《Marine Biology》2011,158(9):1929-1941
The non-breeding movements of marine birds were poorly known until recently, but this information is essential to understanding
the risk to different geographical populations from events on the wintering grounds. We tracked the migration routes and wintering
areas of Thick-billed Murre Uria lomvia from two breeding colonies in eastern Canada: Coats Island in northern Hudson Bay and The Minarets, Baffin Island, during
the period August 2007–May 2008 using geolocation loggers. Birds from The Minarets moved south rapidly post-breeding and wintered
principally off Newfoundland and southern Labrador, or between Newfoundland and southern Greenland, remaining south of 55°N
until at least the spring equinox. Those from Coats Island remained in Hudson Bay until at least mid-November, after which
they moved rapidly through Hudson Strait to winter in southern Davis Strait and the northern Labrador Sea, mostly north of
55°N. Many individuals stayed throughout the winter in areas of heavy ice cover. Adults from the two colonies appear to be
completely segregated in winter and those from Coats Island probably did not enter the area of the winter hunt in Newfoundland.
Unexpectedly, some birds from The Minarets wintered in waters beyond the continental slope and outside the distribution of
pack ice, demonstrating that particular individuals can be wholly pelagic throughout the winter. Coats Island birds returned
through Hudson Strait as soon as open water areas became available in spring. Their sojourn in Hudson Bay coincided very closely
with the occurrence of areas with <90% ice cover. In spite of the relatively large error in positions obtained from geolocation
loggers, our results demonstrated the value of these devices by uncovering a number of previously unknown aspects of Thick-billed
Murre non-breeding ecology in the Northwest Atlantic. Comparison of the non-breeding ecology based on SST experienced in winter
show that the winter niche is broader than hitherto assumed, demonstrating that separate populations may experience different
selection in the face of climate change. 相似文献
974.
Species interactions can induce morphological changes in organisms that affect their subsequent growth and survival. In Moorea,
French Polynesia, epibiotic gammaridean amphipods induce the formation of long, branch-like coral “fingers” on otherwise flat,
encrusting, or plating Montipora coral colonies. The fingers form as corals encrust tubes built by the amphipods and lead to significant changes in colony
morphology. This study examines the costs and benefits of this association to the amphipods and corals and demonstrates that
the interaction is a mutualism. Amphipods gain protection from predators by living within corals, and corals benefit by enhanced
growth and survival. Benefits to the coral arise through direct effects due to the amphipods’ presence as well as through
benefits derived from the altered colony morphology. This study demonstrates that induced morphological plasticity can be
a mechanism for facilitation, adding to our knowledge of the roles mutualism, and phenotypic plasticity play in ecology. 相似文献
975.
The ascidian Styela clava, native to the north-west Pacific, is an invasive species affecting New Zealand’s marine ecosystems, biodiversity and aquaculture
operations. To provide detailed information on the reproductive biology of S. clava in New Zealand for post-border biosecurity management, long-term seasonal patterns of gametogenesis were determined from
May 2006 to May 2008 in Auckland’s Waitemata Harbour (36°49′20″S, 174°45′85″E). Of particular interest was whether the critical
15°C threshold spawning temperature for reproduction observed in the Northern Hemisphere applied here to the first Southern
Hemisphere study. S. clava gametogenesis followed a regular seasonal cycle with ripe gametes appearing as early as September and persisting to June;
this time frame corresponds to the period when sea surface temperatures in the region first reach 15°C and with spawning occurring
mainly during late summer to early autumn. From photoperiod manipulation, it was determined that spawning occurred at approximately
18:20. The extended reproductive period and a short generation time in the Waitemata Harbour provides a lengthy opportunity
for S. clava to spread. Findings are discussed in relation to S. clava’s post-border management. 相似文献
976.
In this paper, we argue that understanding marine ecosystem functioning requires a thorough appreciation of the role of intraguild
predation to system dynamics. The theoretical predictions of intraguild predation models might explain some of the community
features observed in marine ecosystems such as low diversity in upwelling and productive systems and species alternation in
response to moderate external forcing. Finally, we argue that an ecosystem approach to fisheries requires that the size–structure
of fish populations should be taken into account and that it is extremely important to account for the predators of early
stages (eggs and larvae) to gain a thorough understanding of the key interactions between species. 相似文献
977.
Gloria Massamba-N’Siala Roberto Simonini Piero Cossu Ferruccio Maltagliati Alberto Castelli Daniela Prevedelli 《Marine Biology》2011,158(7):1523-1535
The spatial scale of life-history and demographic variation was investigated in the opportunistic polychaete Ophryotrocha labronica La Greca and Bacci. Individuals were collected along the Italian coasts from three thermally different biogeographical regions
of the Mediterranean Sea. For each region, populations from four harbours were considered, and for each harbour, two sites
were examined. Life-history and demographic traits were investigated after one generation under a common garden experiment,
and their variation at the three spatial scales was assessed. All the traits showed high variability with regard to site.
A number of life-history and all demographic traits also varied according to the biogeographical region. Conversely, no differences
were found between harbours, suggesting that geographical isolation did not contribute to phenotypic variation. Results confirmed
the central role of local conditions for the evolution of life history in species colonizing heterogeneous environments, but
they also pointed to the importance of large-scale factors in shaping the phenotypic responses of O. labronica, demonstrating the need for a multi-scale approach for obtaining a good measure of natural variation in widespread opportunistic
species. 相似文献
978.
This study explores the relationship between energy budgeting and prey choice of Octopus rubescens. Seventeen male Octopus rubescens were collected between June 2006 and August 2007 from Admiralty Bay, Washington. Prey choices made by individuals in the
laboratory deviated widely from those expected from a simple optimal foraging model. O. rubescens chose the crab Hemigrapsus nudus over the clam Nuttallia obscurata as prey by a ratio of 3:1, even though prey energy content and handling times suggested that this octopus could obtain 10
times more energy intake per unit time when choosing the latter compared to the former prey species. Octopus energy budgets
were similar when consuming either of the prey species except for lipid extraction efficiency that was significantly higher
in octopuses consuming H. nudus. This suggests that lipid digestibility may play an important role in the prey choice of O. rubescens. 相似文献
979.
Jelle S. van Zweden Christoph Grüter Sam M. Jones Francis L.W. Ratnieks 《Behavioral ecology and sociobiology》2011,65(6):1277-1282
Social insects need to defend their nest against robbery, parasitism and predation. The stingless bee Tetragonisca angustula is unique in that it has guards that hover near the nest entrance in addition to guards that stand at the entrance. We tested
both the general hypothesis that hovering guards increase the effectiveness with which flying intruders are detected and the
specific hypothesis that hovering guards improve the detection of workers of the obligate robber bee, Lestrimellita limao. In an intraspecific study comparing colonies, we found a strong positive relationship between the number of hovering guards
and the distance at which a dummy robber bee or L. limao worker, experimentally moved towards the nest entrance, was detected. These results were mirrored in an interspecific study
showing that four species of stingless bees with similar population colonies but which lacked hovering guards, detected L. limao only at the nest entrance, in contrast to T. angustula. In addition, we found that a greater number of attacks by guards occurred when dummies were impregnated with citral, a major
component of L. limao mandibular gland odour. Our results support the hypothesis that T. angustula hovering guards increase the detection perimeter for flying intruders, especially L. limao. 相似文献
980.
Harshinie Karunarathna 《Journal of Coastal Conservation》2011,15(4):499-507
The long-term morphodynamic response of the Clyde Estuary to any possible change in environmental forcing associated with
global climate change and human interference is examined here using a model based on a systems approach. The model, which
uses Boolean Algebra as its formal mathematical language, provides a qualitative insight into the long term morphodynamic
behaviour of the estuarine system, at this level without the need for detailed and quantitative hydrodynamic and morphodynamic
process knowledge or extensive data resources. The model predictions suggest that the long-term morphological changes in the
Clyde Estuary largely depend on the fluvial flow of the River Clyde. Salt marshes in the upper reaches of the estuary were
found to be the most vulnerable morphological feature of the estuary. In the event of increased river flow in the future,
a likely situation according to climate change scenarios, saltmarshes will deplete or disappear altogether, irrespective of
the sediment influx into the estuary. Changes to waves and tides will also contribute to the evolution by taking the estuary
through significantly different intermediate morphological states whilst evolving towards a stable end state. 相似文献