全文获取类型
收费全文 | 9706篇 |
免费 | 1篇 |
专业分类
安全科学 | 5篇 |
废物处理 | 768篇 |
环保管理 | 1216篇 |
综合类 | 944篇 |
基础理论 | 3117篇 |
污染及防治 | 1749篇 |
评价与监测 | 1010篇 |
社会与环境 | 898篇 |
出版年
2022年 | 1篇 |
2021年 | 2篇 |
2019年 | 1篇 |
2018年 | 1475篇 |
2017年 | 1373篇 |
2016年 | 1197篇 |
2015年 | 125篇 |
2014年 | 17篇 |
2013年 | 11篇 |
2012年 | 460篇 |
2011年 | 1346篇 |
2010年 | 693篇 |
2009年 | 604篇 |
2008年 | 880篇 |
2007年 | 1227篇 |
2006年 | 5篇 |
2005年 | 19篇 |
2004年 | 35篇 |
2003年 | 66篇 |
2002年 | 100篇 |
2001年 | 14篇 |
2000年 | 12篇 |
1999年 | 4篇 |
1998年 | 10篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1984年 | 12篇 |
1983年 | 8篇 |
1981年 | 2篇 |
1975年 | 1篇 |
1935年 | 2篇 |
排序方式: 共有9707条查询结果,搜索用时 718 毫秒
981.
Quantification of copepod gut content by differential length amplification quantitative PCR (dla-qPCR) 总被引:1,自引:0,他引:1
Christofer Troedsson Paolo Simonelli Verena Nägele Jens C. Nejstgaard Marc E. Frischer 《Marine Biology》2009,156(3):253-259
Quantification of feeding rates and selectivity of zooplankton is vital for understanding the mechanisms structuring marine
ecosystems. However, methodological limitations have made many of these studies difficult. Recently, molecular based methods
have demonstrated that DNA from prey species can be used to identify zooplankton gut contents, and further, quantitative gut
content estimates by quantitative PCR (qPCR) assays targeted to the 18S rRNA gene have been used to estimate feeding rates
in appendicularians and copepods. However, while standard single primer based qPCR assays were quantitative for the filter
feeding appendicularian Oikopleura dioica, feeding rates were consistently underestimated in the copepod Calanus finmarchicus. In this study, we test the hypothesis that prey DNA is rapidly digested after ingestion by copepods and describe a qPCR-based
assay, differential length amplification qPCR (dla-qPCR), to account for DNA digestion. The assay utilizes multiple primer
sets that amplify different sized fragments of the prey 18S rRNA gene and, based on the differential amplification of these
fragments, the degree of digestion is estimated and corrected for. Application of this approach to C. finmarchicus fed Rhodomonas marina significantly improved quantitative feeding estimates compared to standard qPCR. The development of dla-qPCR represents a
significant advancement towards a quantitative method for assessing in situ copepod feeding rates without involving cultivation-based
manipulation. 相似文献
982.
Young green turtles (Chelonia mydas) spend their early lives as oceanic omnivores with a prevalence of animal prey. Once they settle into neritic habitats (recruitment),
they are thought to shift rapidly to an herbivorous diet, as revealed by studies in the Greater Caribbean. However, the precise
timing of the ontogenic dietary shift and the actual relevance of animal prey in the diet of neritic green turtles are poorly
known elsewhere. Stable isotopes of carbon, sulfur and nitrogen in the carapace scutes of 19 green turtles from Mauritania
(NW Africa), ranging from 26 to 102 cm in curved carapace length (CCLmin), were analyzed to test the hypothesis of a rapid
dietary shift after recruitment. Although the length of residence time in neritic habitats increased with turtle length, as
revealed by a significant correlation between turtle length and the δ13C and the δ34S of the scutes, comparison of the δ15N of the innermost and outermost layers of carapace scutes demonstrated that consumption of macrophytes did not always start
immediately after recruitment, and turtles often resumed an animal-based diet after starting to graze on seagrasses. As a
consequence, seagrass consumption did not increase gradually with turtle size and animal prey largely contributed to the diet
of turtles within the range 29–59 cm CCLmin (76–99% of assimilated nutrients). Seagrass consumption by turtles larger than
59 cm CCLmin was higher, but they still relied largely on animal prey (53–76% of assimilated nutrients). Thus, throughout
most of their neritic juvenile life, green turtles from NW Africa would be better classified as omnivores rather than herbivores.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
983.
April Hedd P. M. Regular W. A. Montevecchi A. D. Buren C. M. Burke D. A. Fifield 《Marine Biology》2009,156(4):741-751
Owing to the necessity of delivering food to offspring at colonies, breeding seabirds are highly constrained in their foraging
options. To minimize constraints imposed by central-place foraging and to optimize foraging behavior, many species exhibit
flexible foraging tactics. Here we document the behavioral flexibility of pursuit-diving common murres Uria aalge when foraging on female capelin Mallotus villosus in the northwest Atlantic. Quite unexpectedly, being visual foragers, we found that common murres dived throughout the day
and night. Twenty-one percent of recorded dives (n = 272 of 1,308 dives) were deep (≥50 m; maximum depth = 152 m, maximum duration = 212 s), bringing murres into sub-0°C water
in the Cold Intermediate Layer (CIL; 40–180 m) of the Labrador Current. Deep dives occurred almost exclusively during the
day when murres would have encountered spatially predictable aggregations of capelin between 100 and 150 m in the water column.
Temperatures within the CIL shaped trophic interactions and involved trade-offs for both predators and prey. Sub-0°C temperatures
limit a fish’s ability to escape from endothermic predators by reducing burst/escape speeds and also lengthening the time
needed to recover from burst-type activity. Thus, while deep diving may be energetically costly, it likely increases certainty
of prey capture. Decreased murre foraging efficiency at night (indicated by an increase in the number of dives per bout) reflects
both lower light conditions and changing prey behavior, as capelin migrate to warmer surface waters at night where their potential
to escape from avian predators could increase. 相似文献
984.
Giovanni A. P. dos Santos Sofie Derycke Verônica G. F. Genevois Luana C. B. B. Coelho Maria T. S. Correia Tom Moens 《Marine Biology》2009,156(4):629-640
Accurate prediction of the biodiversity–ecosystem functioning relationship requires adequate understanding of the interactions
among species in a community. Effects of species diversity on ecosystem functioning are usually considered more pronounced
with increasing functional dissimilarity, although species within functional groups may also perform non-identical functions
and interact with each other. Here we present results of a laboratory experimental study aimed at elucidating whether interspecific
interactions among species within a single nematode trophic group, bacterivores, (1) affect population development and community
structure, and (2) depend on food availability. We studied the population growth of Rhabditis (Pellioditis) marina, a rhabditid nematode known to favour very high food densities when in monoculture, and of Diplolaimelloides meyli and D. oschei, congeneric Monhysteridae known to perform better in monocultures at intermediate food availability. Both Diplolaimelloides species showed significantly different patterns of food-density dependence in combination culture compared to monoculture.
At very high food availability, the rhabditid nematode facilitated growth of both monhysterid species, probably as a result
of down-regulation of bacterial density. At the lowest food availabilities, the presence of even low numbers of monhysterid
nematodes lead to exclusion of the rhabditid, which at such low food availability has a very inefficient food uptake. At intermediate
food availabilities, abundances of both Diplolaimelloides species were strongly depressed in the combination culture, as a result of food depletion by the rhabditid, indirect inhibitory
interactions between the two congeneric species, or both. The complexity of the species interactions render predictions on
the outcome and functional consequences of changes in within-trophic-group diversity highly problematic. 相似文献
985.
986.
Pedro Daleo Tomás Luppi Agustina Mendez Casariego Mauricio Escapa Pablo Ribeiro Paola Silva Oscar Iribarne 《Marine Biology》2009,156(3):269-275
Size advantage in male–male competition over mates, combined with male preference over large females, is a common feature
that can drive to size assortative mating and, eventually, sexual selection. In crabs, appendage autotomy can affect assortative
mating and opportunity for sexual selection by affecting size advantage in mating contests. In this work, we evaluate the
effect of size and appendage autotomy in generating assortative mating in the mud crab Cyrtograpsus angulatus. Field observations of guarding pairs in two different populations show a positive correlation between carapace width of
males and females in both the populations. In one of the populations, incidence of appendage autotomy was low and the variability
in the size of reproductive males was lower than the variability in the size of randomly collected males (i.e. only larger
males were successful in getting a female), whereas there was no differences in the other population (i.e. most male sizes
were successful) where the incidence of appendage autotomy was very high, indicating that the importance of size is higher
when the incidence of autotomy is low. In this context, experiments (in both populations) show that, in contests for a female,
larger males outcompete smaller ones only when they had intact appendages. When males had missing chelipeds, winning or loosing
against smaller males was random. This may lead to a decrease in the importance of male size in populations with high incidence
of cheliped autotomy, affecting assortative mating and opportunity for selection and, thus, affecting selective pressures. 相似文献
987.
Positive plant–animal interactions are important in community ecology, but relatively little attention has been paid to their
effect on the production of mangroves, dominant halophytic trees in tropical coastal marshes. Here, the role of fiddler crab
(Uca spp.) burrowing on the growth and production of the white mangrove, Laguncularia racemosa (<2 years old), was examined in a restored marsh in Tampa Bay, Florida (27°41.65 N, 82°30.34 W) with manipulative experiments
from June 2006 to May 2007. Fiddler crab burrowing significantly increased mangrove height by 27%, trunk diameter by 25%,
and leaf production by 15%, compared to mangroves in crab exclusion enclosures. Additionally, the exclusion of fiddler crabs
significantly increased interstitial water salinity from 32.4 to 44.2, and decreased the oxidation–reduction potential of
the low organic sediments, but did not affect soil pH or sulfide concentration. Mangrove height, trunk diameter, and leaf
production along a transect that varied in crab burrow density were positively associated with the number of crab burrows.
Further, the density of sympatric Spartina alterniflora shoots was positively correlated with crab burrow density along the transect. As in temperate marshes, fiddler crabs can
have significant ecological effects on mangrove communities, serving as ecological engineers by modulating the amount of resources
available to marsh plants, and by altering the physical, chemical, and biological state of these soft sediment communities.
In restored coastal systems that typically have very poor sediment quality, techniques such as soil amendment could be used
to facilitate a more natural interaction between crabs and mangroves in ecosystem development. 相似文献
988.
Many benthic colonial invertebrates have the ability to fuse and form chimeras with compatible colonies. Botryllid ascidians
are model organisms for the study of the evolution of and molecular basis for allorecognition, and fusion rates have been
determined for different populations and species by random sampling and fusion testing between individuals. However, natural
fusion rates over time have not been documented. Nine settlement panels were deployed in Salem Harbor, Massachusetts, USA
and Botrylloides violaceus settlement, growth, and fusion monitored from July to mid-August 2007. Seventy-three percent of the recruits observed fused
with at least one other colony, while 4% neither fused nor were overgrown. Multifused colonies were not observed to grow faster
than single colonies when growth was calculated as increase in size beyond the summation of fused entities; however, they
were significantly larger. These results suggest that larvae settle in clumps of compatible individuals, and that large subtidal
colonies may be the result of high numbers of fusions between compatible colonies. 相似文献
989.
Alan M. Piggot Bruce W. Fouke Mayandi Sivaguru Robert A. Sanford H. Rex Gaskins 《Marine Biology》2009,156(11):2379-2389
Results from controlled in situ experimentation conducted on the leeward reef tract of Curaçao, Netherlands Antilles, indicate that the coral Montastraea annularis exhibits a complex, yet consistent, cellular response to increasing sea surface temperature (SST) and decreasing irradiance. This was determined by simultaneously quantifying and tracking the tissue density of zooxanthellae and mucocytes using a novel technique that integrates the lectin histochemical stain wheat germ agglutinin (WGA) with high-resolution (200 nm) optical epifluorescence microscopy. Coral colonies growing at 6-m water depth (WD) and an irradiance of 100.2 ± 6.5 μmol m?2 s?1 were treated with a shading experiment for 11 days that reduced irradiance to 34.9 ± 6.6, 72.0 ± 7.0 and 90.1 ± 4.2 μmol m?2 s?1, respectively. While a significant decrease in the density of both zooxanthellae and mucocytes were observed at all shade levels, the largest reduction occurred between the natural non-shaded control (44,298 ± 3,242 zooxanthellae cm?2; 4,853 ± 346 mucocytes cm?2) and the highest shading level (13,982 ± 1,961 zooxanthallae cm?2; 2,544 ± 372.9 mucocytes cm?2). Colonies were also sampled during a seasonal increase in SST of 1.5°C, where the density of zooxanthellae was significantly lower (from 54,710 ± 1,755 to 34,322 ± 2,894 cells cm?2) and the density of mucocytes was significantly higher (from 6,100 ± 304 to 29,658 ± 3,937 cells cm?2). These observations of coral cellular response to environmental change provide evidence to support new hypotheses for coral survival and the complex role played by mucus in feeding, microbial associations and resilience to increasing SST. 相似文献
990.
Herbivory has a strong impact on algal distribution, abundance and community structure and may influence the establishment
and spread of introduced seaweed species. In this study, we assess the potential regulating role of herbivory on one of the
most invasive brown seaweeds: Sargassum muticum. Multiple choice feeding experiments were conducted with 13 native seaweeds, S. muticum and 5 herbivore species from the Northwest, Southwest and South of Portugal. S. muticum was always the least or among the least preferred seaweeds and attained one of the highest growth rates of the tested seaweeds,
with and without herbivores. The addition of herbivores increased the number of cases by 40% in which the invader had higher
growth rates. Our results suggest that low grazing pressure on S. muticum by the recipient herbivore community may give the invader a competitive advantage over at least part of the native seaweed
community, thereby contributing to the invasiveness of S. muticum along the Portuguese coast. 相似文献