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排序方式: 共有68条查询结果,搜索用时 600 毫秒
41.
Alan W. Gertler William G. Coulombe John G. Watson John L. Bowen Richard T. Egami Stan Marsh 《Environmental monitoring and assessment》1993,24(1):13-25
The USEPA replaced TSP with PM10 as the National Ambient Air Quality Standard for particulate matter. The commercially available PM10 sampler is a high-volume model using quartz fiber filters. In certain investigations, such as source apportionment studies, chemical analysis of the filter is necessary, however, many analyses cannot be run on quartz filters. An alternate filter such as Teflon is amenable to XRF and ion chemical analyses but is not amenable to analysis for carbon. To overcome these problems DRI constructed a medium-volume PM10 sampler that is capable of collecting particulates on both Teflon and quartz fiber filters simultaneously. This paper describes the design of the DRI medium-volume PM10 sampler, discusses a method for determining equivalence of two samplers, the results of applying the method to test the equivalence of the medium-volume sampler and a commerical high-volume sampler, and examines differences between PM10 and TSP measurements in a southwestern desert. 相似文献
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44.
Peter B. S. Spencer Alan B. Horsup Helene D. Marsh 《Behavioral ecology and sociobiology》1998,43(1):1-9
The reason why a female who is socially paired to one particular male seeks extra-pair copulations (EPCs) with others has
important implications in life history models and to the study of behaviour. The Allied rock-wallaby, Petrogale assimilis, lives in spatially isolated colonies in tropical north Queensland, Australia. Extensive observations of a colony at Black
Rock showed that intense behavioural bonding occurs between pairs of adult males and females; about two-thirds of males paired
with one female, the remainder paired with two females simultaneously. Single-locus microsatellite profiling determined the
paternity of 63 offspring from 21 females for which long-term behavioural data were available. One-third of the young were
fathered by males which were not paired socially with the mother. The mating system was heterogeneous: (1) all offspring of
11 females were fathered by the mother's partner, (2) all young of 5 females were fathered by extra-pair males, and (3) only
some of the young of 5 females were fathered by their regular consort. Analysis of individual longitudinal demographic records
showed that females whose young were always fathered by their consort had higher reproductive success than those whose young
were always fathered as a result of (EPCs). However, females with some offspring fathered by their regular consort and others
via EPCs had the highest probability of raising young to independence. These females were significantly more likely to have
an offspring fathered as a result of an EPC if their previous young had failed to survive to pouch emergence. These results
are consistent with the hypothesis that females choose mates for their genetic quality. Comparison of the males with which
these females sought EPCs and the regular consorts suggested that arm length rather than body weight or testes size was used
as the index of genetic quality. Results from a second colony of rock-wallabies in which the reproductive rate was accelerated
were also consistent with the genetic-quality hypothesis. These results imply that by choosing better-quality fathers irrespective
of social pairing, females are able to maximise their overall lifetime reproductive success, and presumably, those of their
offspring.
Received: 8 June 1997 / Accepted after revision: 28 February 1998 相似文献
45.
Natal site and offshore swimming influence fitness and long-distance ocean transport in young sea turtles 总被引:1,自引:1,他引:0
Nathan F. Putman Rebecca Scott Philippe Verley Robert Marsh Graeme C. Hays 《Marine Biology》2012,159(10):2117-2126
Although long-distance transport of marine organisms is constrained by numerous oceanic and biological factors, some species have evolved life-histories reliant on such movements. We examine the factors that promote long-distance transport in a transoceanic migrant, young loggerhead sea turtles (Caretta caretta), from the southeastern U.S. Empirical data from near-surface buoys and simulations in two ocean circulation models indicated that passive drifters are often retained for long periods shoreward of oceanic fronts that delineate coastal and offshore waters. Further simulations revealed that offshore swimming aided newly hatched turtles in moving past fronts and increased turtles’ probability of survival, reaching distant foraging grounds, and encountering favorable temperatures. Swimming was most beneficial in regions that were more favorable under scenarios assuming passive drift. These results have broad implications for understanding the movement processes of many marine species, highlighting likely retention of more planktonic species and potential for dispersal in more nektonic species. 相似文献
46.
Polybrominated diphenyl ethers (PBDEs) are a class of brominated flame retardants (BFRs) which have become widespread environmental pollutants due to their persistence and bioaccumulativeness. Pure authentic PBDE congeners are required for chemical analysis, assessments of their chemical/physical properties and toxicological studies. We here report an improved method for synthesis of authentic PBDE congeners applying bromophenols and symmetrical brominated diphenyliodonium salts as building blocks. Altogether, 13 PBDEs were synthesized of which seven are new. The improved coupling reaction between the bromophenol and the brominated diphenyliodonium salts resulted in enhanced yields for PBDEs substituted with more than six bromine atoms. Also, improvements in iodonium salt synthesis made it possible to synthesize symmetrical hexabromodiphenyliodonium salts for the first time, i.e. 2,2',3,3',4,4'-, 2,2',4,4',5,5'- and 2,2',4,4',6,6'-hexabromodiphenyliodonium salts and they made it possible to prepare octabrominated PBDEs via the actual coupling method. All synthesized compounds were characterized by (1)H NMR, (13)C NMR spectra and by their melting points. Also, all products except for the diphenyliodonium salts were characterized by mass spectra in electron ionization mode. 相似文献
47.
Is avian humoral immunocompetence suppressed by testosterone? 总被引:2,自引:2,他引:0
Dennis Hasselquist James A. Marsh Paul W. Sherman John C. Wingfield 《Behavioral ecology and sociobiology》1999,45(3-4):167-175
A key issue in sexual selection theory is how a correlation between male secondary sexual characters and male genetic quality
can be maintained. The immunocompetence-handicap hypothesis proposes that testosterone-dependent male characters remain honest
signals because of the immunosuppressive effect of elevated steroid hormone levels. The hypothesis requires that physiological
levels of testosterone depress immune system function. We quantified testosterone titers and humoral immunocompetence of captive
male and female red-winged blackbirds (Agelaius phoeniceus) at three points in the annual cycle (autumn, prebreeding, and breeding). We also conducted an implant experiment on the
males to assess the effects of prolonged, above-normal testosterone titers on humoral immune responses. Humoral immunocompetence
was measured as secondary antibody production to a non-pathogenic protein antigen, keyhole limpet hemocyanin, using an enzyme-linked
immunosorbent assay we developed for A. phoeniceus. Secondary antibody responses of individuals were highly repeatable between sampling periods. Neither physiological nor above-normal
levels of plasma testosterone suppressed secondary antibody production. In paired tests of the same individuals between prebreeding
and breeding, and between breeding and implant, plasma testosterone increased significantly but secondary antibody responses
were unaffected. We are confident in these results because with 80% power, an 11–14% difference in antibody titers would have
been detected. There was no relationship between plasma testosterone levels and humoral immunocompetence in free-ranging males
tested at the peak of breeding. These results cast doubt on a key assumption of the immunocompetence-handicap hypothesis.
Received: 13 April 1998 / Accepted after revision: 7 October 1998 相似文献
48.
Marine mammals from Queensland, Australia, are bioaccumulating elevated concentrations of a range of polybrominated natural products. In this study, we detected three new polybrominated dimethoxybiphenyls (PBDMBs) in the blubber of selected marine mammal samples which were identified as 2,6'-dimethoxy-3,3',5-tribromobiphenyl (2,6'-diMeO-BB 36), 2,2'-dimethoxy-3,3'-dibromobiphenyl (2,2'-diMeO-BB 36), and 6,6'-dimethoxy-3,3'-dibromobiphenyl (6,6'-diMeO-BB 11). These three PBDMBs are structurally related to the known natural product 2,2'-dimethoxy-3,3',5,5'-tetrabromobiphenyl (2,2'-diMeO-BB 80). In the first part of this study, 2,2'-diMeO-BB 80 was photochemically debrominated under UV irradiation. This resulted in seven of eight possible mono- to triBDMBs as debromination products. In the second part of this study, the structure of all PBDMBs debromination products was investigated. This was supported by synthesis of two diBDMB and one triBDMB via bromination and subsequent methylation of 2,2'-biphenyldiol. Structures of the remaining PBDMBs were tentatively assigned by considering the retention times, mass spectra and amounts formed during UV irradiation of 2,2'-diMeO-BB 80 . In the third part of this study, blubber of marine mammals from Australia was analysed for PBDMBs using gas chromatography in combination with electron ionization mass spectrometry (GC/EI-MS) in the selected ion monitoring mode. In these samples, 2,2'-diMeO-BB 80 was found at concentrations of 200-1800ngg(-1) lipid weight (lw). The latter represents the highest concentration reported for this compound in environmental samples. 6,6'-diMeO BB 11, 2,2'-diMeO BB 36, and 2,6'-diMeO BB 36 were present at approximately 7ngg(-1) lipids, or 0.43-1.5% of diMeO-BB 80. No further PBDMBs were detected in the samples. The di- and triBDMBs identified in marine mammal blubber have not been reported as natural products. They may represent either new natural products or transformation products of 2,2'-diMeO-BB 80. 相似文献
49.
In human-dominated landscapes, interactions and perceptions towards wildlife are influenced by multidimensional drivers. Understanding these drivers could prove useful for wildlife conservation. We surveyed the attitudes and perceptions of fishers towards threatened Irrawaddy dolphins (Orcaella brevirostris) at Chilika Lagoon India. To validate the drivers of fisher perceptions, we : (1) observed dolphin foraging behavior at stake nets, and (2) compared catch per unit effort (CPUE) and catch income of fishers from stake nets in the presence and absence of foraging dolphins. We found that fishers were mostly positive towards dolphins, believing that dolphins augmented their fish catch and using culture to express their perceptions. Foraging dolphins were observed spending half their time at stake nets and were associated with significantly higher catch income and CPUE of mullet (Liza sp.), a locally preferred food fish species. Wildlife conservation efforts should use the multidimensional drivers of human–wildlife interactions to involve local stakeholders in management. 相似文献
50.
Hydroxylated polybrominated diphenyl ethers (OH-PDBEs) are exogenous, bioactive compounds that originate, to a large extent, from anthropogenic activities, although they are also naturally produced in the environment. In the present study nine new authentic OH-PBDE reference standards and their corresponding methyl ether derivatives (MeO-PBDEs) were synthesised and characterised by NMR spectroscopy and mass spectrometry. Seven of the authentic reference standards prepared were thereafter tentatively identified in a pooled human blood sample. The tentatively identified OH-PBDEs were 3-hydroxy-2,2',4,4',6-pentabromodiphenyl ether, 3'-hydroxy-2,2',4,4',6-pentabromodiphenyl ether, 3-hydroxy-2,2',4,4',5-pentabromodiphenyl ether, 3-hydroxy-2,2',4,4',5,6'-hexabromodiphenyl ether, 3'-hydroxy-2,2',4,4',5,6'-hexabromodiphenyl ether, 3-hydroxy-2,2',4,4',5,5'-hexabromodiphenyl ether and 4-hydroxy-2,2',3,4',5,5',6-heptabromodiphenyl ether. An additional seven OH-PBDEs were tentatively identified in the pooled human blood sample, of which one OH-PBDE, 4'-hydroxy-2,2',4,5,5'-pentabromodiphenyl ether, has not been identified in human blood before. The identification was performed using gas chromatography-mass spectrometry (GC-MS) recording the bromine ions m/z 79, 81. The tentative identification was supported by the peaks relative retention times (RRTs) compared to authentic references on two GC columns of different polarities for the hexa-, and heptabrominated OH-PBDEs, and three different GC columns for the pentabrominated OH-PBDEs. The OH-PBDE congeners most likely originate from human metabolism of a flame retardant, i.e. polybrominated diphenyl ethers (PBDEs), due to the relatively high concentrations of PBDEs in the same human blood sample and the fact that these PBDEs could form the tentatively identified OH-PBDEs via metabolic direct hydroxylation or via 1,2-shift. 相似文献