全文获取类型
收费全文 | 958篇 |
免费 | 32篇 |
国内免费 | 8篇 |
专业分类
安全科学 | 52篇 |
废物处理 | 43篇 |
环保管理 | 255篇 |
综合类 | 82篇 |
基础理论 | 256篇 |
环境理论 | 2篇 |
污染及防治 | 199篇 |
评价与监测 | 67篇 |
社会与环境 | 34篇 |
灾害及防治 | 8篇 |
出版年
2023年 | 8篇 |
2022年 | 16篇 |
2021年 | 12篇 |
2020年 | 6篇 |
2019年 | 14篇 |
2018年 | 20篇 |
2017年 | 21篇 |
2016年 | 28篇 |
2015年 | 30篇 |
2014年 | 26篇 |
2013年 | 60篇 |
2012年 | 58篇 |
2011年 | 58篇 |
2010年 | 39篇 |
2009年 | 60篇 |
2008年 | 68篇 |
2007年 | 59篇 |
2006年 | 56篇 |
2005年 | 32篇 |
2004年 | 42篇 |
2003年 | 39篇 |
2002年 | 35篇 |
2001年 | 9篇 |
2000年 | 15篇 |
1999年 | 14篇 |
1998年 | 14篇 |
1997年 | 11篇 |
1996年 | 14篇 |
1995年 | 15篇 |
1994年 | 18篇 |
1993年 | 11篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 9篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1984年 | 4篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1971年 | 1篇 |
1957年 | 2篇 |
排序方式: 共有998条查询结果,搜索用时 31 毫秒
951.
Current taxonomy indicates a single global species of the Great Barracuda (Sphyraena barracuda) despite differences in color and behavior between Atlantic and Pacific forms. To investigate these differences and qualify
the dispersal characteristics of this unique coastal–pelagic teleost (bony fish), we conducted a global phylogeographic survey
of 246 specimens from thirteen sampling locations using a 629-base pair fragment of mtDNA cytochrome b. Data indicate high overall gene flow in the Indo-Pacific over large distances (>16,500 km) bridging several biogeographic
barriers. The West Atlantic population contains an mtDNA lineage that is divergent from the Indo-Pacific (d = 1.9%), while the East Atlantic (N = 23) has two mutations (d = 0.6%) apart from the Indo-Pacific. While we cannot rule out distinct evolutionary partitions among ocean basins based on
behavior, coloration, and near-monophyly between Atlantic and Indo-Pacific subpopulations, more investigation is required
before taxonomic status is revised. Overall, the pattern of high global dispersal and connectivity in S. barracuda more closely resembles those reported for large oceanic predators than reef-associated teleosts. 相似文献
952.
Susan L. Balenger L. Scott Johnson Brian S. Masters 《Behavioral ecology and sociobiology》2009,63(3):403-411
Ornamental traits are thought to evolve because they give individuals an advantage in securing multiple mates. Thus, the presence
of ornamentation among males in many monogamous bird species presents something of a conundrum. Under certain conditions,
extra-pair paternity can increase the variance in reproductive success among males, thus increasing the potential for sexual
selection to act. We addressed this possibility in the mountain bluebird (Sialia currucoides), a socially monogamous songbird in which males possess brilliant ultraviolet (UV)-blue plumage. Specifically, we asked whether
a male’s success at siring offspring within his own nest and within the nests of other males was related to his coloration.
In pairwise comparisons, males that sired extra-pair offspring were not more colorful than the males that they cuckolded.
However, males that sired at least one extra-pair offspring were, on average, brighter and more UV-blue than males that did
not sire extra-pair offspring. Brighter, more UV-blue males sired more offspring both with their own mate and tended to sire
more offspring with extra-pair mates and thus sired more offspring overall. Our results support the hypothesis that the brilliant
UV-blue ornamental plumage of male mountain bluebirds evolved at least in part because it provides males with an advantage
in fertilizing the eggs of multiple females. 相似文献
953.
Despite the important roles played by parasites in local population dynamics and community structure of marine ecosystems,
there is a lack of information on the geographical variation in infection levels displayed by particular host–parasite species
combinations. This study examines geographical variation in infection levels by the metacercarial stages of trematode parasites
in crustacean and bivalve second intermediate hosts. Analyses were based on a dataset compiled from the literature, consisting
of 164 local samples representing 49 host–parasite species pairs for crustaceans, and 338 entries representing 36 host–parasite
species pairs for bivalves. The analyses indicate that for all measures of infection levels [prevalence (percentage of individuals
infected), intensity (mean no. of metacercariae per infected individual), abundance (mean no. of metacercariae across all
individuals in a sample)], there was statistically significant repeatability of infection values within host–parasite species
pairs. However, it is only for values of intensity and abundance of infection in crustacean hosts that the repeatability was
strong; this suggests that infection levels are specific properties of crustacean–trematode species pairs, showing significant
consistency across localities despite spatial variation in abiotic and biotic conditions. Although the magnitude of variation
in infection levels within parasite species pairs (measured as coefficients of variation) was independent of scale in crustacean
hosts, infection levels in bivalves increased in variability at large (>100 km) spatial scales. These results suggest that
there is a considerable geographical consistency in parasite load, especially in crustacean hosts, which should lead to consistent
ecological and ecosystem effects of marine trematodes.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
954.
The aim of this study was to investigate the influence of diesel on the loss and bioavailability of soil-associated [14C]phenanthrene with time. In addition, the temporal development of phenanthrene catabolic activity and the impact of co-contaminant mixtures on the soil microflora were also assessed. With respect to compound fate, the results suggested that competitive effects between dissimilar co-contaminants did influence [14C]phenanthrene loss. Where diesel was present at a concentration of 0, 20, 200 and 2000 mg kg(-1), increased phenanthrene loss was observed with increasing diesel concentrations. In the 20,000 mg kg(-1) diesel treatment, however, a significantly higher amount of the initial [14C]activity remained after 225 days. Furthermore, initial degradation of phenanthrene in this treatment was retarded as a result of repressed phenanthrene catabolic activity. These results were complemented by a 4-fold increase in total culturable bacterial cell numbers in the 20,000 mg kg(-1) treatment when compared with the 2000 mg kg(-1) after 225 days of incubation time. 相似文献
955.
This study aimed to determine the extent to which older drivers can be considered responsible for their crashes, to identify key factors in those crashes for which older drivers have been judged responsible, and to assess the extent to which older drivers' extra crash responsibility contributes to the road toll. Insurance claims from the State of Tasmania, Australia, for 1998-2002 were linked with police records for crashes involving drivers aged either 41-55 years or 65 years or older. Insurance and police data sets contained independent judgments of crash responsibility. There was a high level of agreement between the two sets of judgments, with older drivers judged around 1.5 times more likely to be responsible for their crashes than middle-aged drivers and, conversely, older drivers were around 0.6 as likely to be absolved from crash responsibility. It was concluded that older drivers' additional crash responsibility while valuable in explaining "what went wrong," currently makes only a small contribution to the overall road toll. 相似文献
956.
Reist JD Wrona FJ Prowse TD Power M Dempson JB Beamish RJ King JR Carmichael TJ Sawatzky CD 《Ambio》2006,35(7):370-380
Projected shifts in climate forcing variables such as temperature and precipitation are of great relevance to arctic freshwater ecosystems and biota. These will result in many direct and indirect effects upon the ecosystems and fish present therein. Shifts projected for fish populations will range from positive to negative in overall effect, differ among species and also among populations within species depending upon their biology and tolerances, and will be integrated by the fish within their local aquascapes. This results in a wide range of future possibilities for arctic freshwater and diadromous fishes. Owing to a dearth of basic knowledge regarding fish biology and habitat interactions in the north, complicated by scaling issues and uncertainty in future climate projections, only qualitative scenarios can be developed in most cases. This limits preparedness to meet challenges of climate change in the Arctic with respect to fish and fisheries. 相似文献
957.
Hannah B. Vander Zanden Joseph B. Pfaller Kimberly J. Reich Mariela Pajuelo Alan B. Bolten Kristina L. Williams Michael G. Frick Brian M. Shamblin Campbell J. Nairn Karen A. Bjorndal 《Marine Biology》2014,161(3):585-598
Diet items and habitat constitute some of the environmental resources that may be used differently by individuals within a population. Long-term fidelity by individuals to particular resources exemplifies individual specialization, a phenomenon that is becoming increasingly recognized across a wide range of species. Less is understood about the consequences of such specialization. Here, we investigate the effects of differential foraging ground use on reproductive output in 183 loggerhead sea turtles (Caretta caretta) nesting at Wassaw Island, Georgia (31.89°N, 80.97°W), between 2004 and 2011 with resulting possible fitness effects. Stable isotope analysis was used to assign the adult female loggerheads to one of three foraging areas in the Northwest Atlantic Ocean. Our data indicate that foraging area preference influences the size, fecundity, and breeding periodicity of adult female loggerhead turtles. We also found that the proportion of turtles originating from each foraging area varied significantly among the years examined. The change in the number of nesting females across the years of the study was not a result of uniform change from all foraging areas. We develop a novel approach to assess differential contributions of various foraging aggregations to changes in abundance of a sea turtle nesting aggregation using stable isotopes. Our approach can provide an improved understanding of the influences on the causes of increasing or decreasing population trends and allow more effective monitoring for these threatened species and other highly migratory species. 相似文献
958.
Joseph D. DiBattista John E. Randall Stephen J. Newman Brian W. Bowen 《Marine Biology》2014,161(11):2465-2477
Molecular genetic surveys of marine fishes have revealed that some widely distributed species are actually a composite of multiple evolutionary lineages. This is apparent in the round herrings (genus Etrumeus), wherein a globally distributed taxon (Etrumeus sadina Mitchill 1814) has proven to contain at least seven valid taxa, with more likely awaiting discovery. Here, we survey evolutionary lineages of the nominal E. sadina (formerly E. teres, a junior synonym) across the southern temperate zone of Australia, a marine region divided into three biogeographic provinces based primarily on the distribution of intertidal faunas. Results from morphological and mitochondrial DNA data reveal two evolutionary lineages corresponding to eastern and southwestern provinces (d = 0.007 for cytochrome c oxidase subunit I and d = 0.017 for cytochrome b), possibly initiated by the Bassian Isthmus between Australia and Tasmania during low sea-level stands. The Australian round herring is also genetically distinct from the nearest congeneric forms in the Indian and Pacific Oceans, with a corresponding modal difference in gill-raker counts in most cases. Based on these data, we resurrect the title Etrumeus jacksoniensis for the Australian round herring. While the Bassian Isthmus may have initiated the partition of evolutionary lineages within Australia, additional oceanographic and ecological factors must reinforce this separation in order to maintain diagnostic genetic differences along a continuous temperate coastline. 相似文献
959.
960.
Pinot noir, bastardo, rkaziteli and semillon grapes on vines grown in the Barossa Valley of South Australia were treated with a commercial dithianon formulation. The grapes were harvested by hand eight days later, and made into wine. Grab samples of berries, grape juice and the young wine were analysed for fungicide residues. No dithianon was detected in control grape samples, grape juices or wines. Significant dithianon levels were detected on the skins of treated grape samples. Dithianon is stable on the surface of grapes under the ambient conditions prevalent under the grape canopy for at least two weeks. No dithianon was detected in grape juice, on grape skins after berry crushing, in the lees, or in the young wine. Dithianon is unstable in grape juice and wine. Dithianon half‐life (initial concentration = 1 μg/mL) in semillon grape juice = 2.8 h, semillon wine = 0.58 h, pinot noir grape juice = 4.6 h, and pinot‐noir wine = 0.29 h. Treatment with fining agents or heat does not significantly reduce the rate of degradation. These results suggest that spraying table grapes with dithianon two weeks before harvest would result in exposure to essentially the full dose of active ingredient sprayed, and increase the risk to human health through ingestion of this compound. However, any threat to human health from ingestion through grape juice or wine is limited since any contact with grape juice or wine leads to rapid decomposition of dithianon by some as yet undetermined process. 相似文献