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991.
Ann Curtis Lisa Strain Moira Mennie Susan Holloway J. A. Raeburn G. T. N. Besley D. J. H. Brock 《黑龙江环境通报》1988,8(8):625-628
First-trimester prenatal diagnosis of cystic fibrosis (CF) using linked DNA markers is usually only possible if there is an index affected child to establish the haplotype of the parental chromosomes. We describe a prenatal diagnosis where fibroblasts, cultured from the skin of a deceased affected child and then held in frozen storage for 3 years, were used as the starting point for tracking the CF gene. The fetus was diagnosed as a homozygous normal and the diagnosis confirmed by immunoreactive trypsin testing after birth. It was also possible to establish heterozygosity in the aunt of the affected child. 相似文献
992.
The atherinid fish Craterocephalus capreoli Rendahl is abundant in the Houtman Abrolhos Islands, 70 km off the Western Australia coast and 250 km south of the southern limit of the range of the species along the mainland. Electrophoretic examination of 7 allozyme loci at 17 sites in the Houtman Abrolhos revealed a substantially lower level of polymorphism than found in an earlier study of the species in its mainland distribution, with many of the uncommon alleles and some common ones missing. There is a very high degree of genetic subdivision among the populations in the Houtman Abrolhos, measured by a mean F
ST
of 0.437 over a distance of 35 km. This F
ST
(standardized variance in allelic frequencies) is six times that found previously among populations along the mainland coast over distances up to 850 km. The subdivision of populations in the Houtman Abrolhos is similar within one island group on a scale up to 12 km, and between two groups that are separated by 15 km of deep water. Significant differences in allelic frequencies were found between populations from the open shore and enclosed lagoons less than 800 m apart, but the overall levels of subdivision were similar for the two types of environment. Previous work had shown high levels of genetic subdivision in the Houtman Abrolhos for a gastropod with direct development. The results for C. capreoli demonstrate that the archipelago favours subdivision even for a species with potentially much greater mobility and different life history. 相似文献
993.
Mikhail Goltsman Elena P. Kruchenkova Sergei Sergeev Paul J. Johnson David W. Macdonald 《Behavioral ecology and sociobiology》2005,59(2):198-206
Since the Pleistocene, Arctic foxes, Alopex lagopus, on Mednyi Island in the North Pacific have been isolated in a small area with rich food resources and no other terrestrial carnivores. This situation provides an unusually simple system within which the effect of food dispersion on demography and social organisation was examined. We studied the composition, location and dispersal of 67 Arctic fox groups and mapped their major food resources (seabird colonies) during 1994–2000 on Mednyi. We compared our observations with the predictions of models of sex-ratio determination. Our observations are most consistent with the predictions of Julliard's (2000) model, where mothers are expected to produce more offspring of the most dispersing sex in low-quality habitats, and more offspring of the most philopatric sex in high-quality habitats. The polygynous foxes on Mednyi Island lived where the principal food resources were patchily distributed (present on 11% of the shoreline), and cub survival to dispersal age or reproductive adult was higher in rich (25/45) than in poor (24/79) home ranges. Furthermore, dispersal was strongly sex-biased: most females (60%) remained on their natal ranges, whereas very few males (9%) did so. Significantly more female than male cubs (54 compared with 24) emerged from dens in resource rich ranges, whereas the sex ratio on poor ranges was approximately equal (51 females and 56 males). While our observations are also to some extent consistent with the local resource enhancement (LRE) hypothesis (which predicts a bias towards the sex most likely to cooperate with parents), this does not account for the observed spatial variability. 相似文献
994.
Simulating forest structure, timber production, and socioeconomic effects in a multi-owner province.
K Norman Johnson Pete Bettinger Jeffrey D Kline Thomas A Spies Marie Lennette Gary Lettman Brian Garber-Yonts Tad Larsen 《Ecological applications》2007,17(1):34-47
Protecting biodiversity has become a major goal in managing coastal forests in the Pacific Northwest--an area in which human activities have had a significant influence on landscape change. A complex pattern of public and private forest ownership, combined with new regulations for each owner group, raises questions about how well and how efficiently these policies achieve their biodiversity goals. To develop a deeper understanding of the aggregate effect of forest policies, we simulated forest structures, timber production, and socioeconomic conditions over time for the mixture of private and public lands in the 2.3-million-ha Coast Range Physiographic Province of Oregon. To make these projections, we recognized both vegetative complexity at the stand level and spatial complexity at the landscape level. We focused on the two major factors influencing landscape change in the forests of the Coast Range: (1) land use, especially development for houses and cities, and (2) forest management, especially clearcutting. Our simulations of current policy suggest major changes in land use on the margins of the Coast Range, a divergence in forest structure among the different owners, an increase in old-growth forests, and a continuing loss of the structural elements associated with diverse young forests. Our simulations also suggest that current harvest levels can be approximately maintained, with the harvest coming almost entirely from private lands. A policy alternative that retained live trees for wildlife would increase remnant structures but at a cost to landowners (5-7% reduction in timber production). Another alternative that precluded thinning of plantations on federal land would significantly reduce the area of very large diameter (>75 cm dbh) conifer forests 100 years into the future 相似文献
995.
Economics: Theory versus Practice in Wildlife Management 总被引:1,自引:0,他引:1
One of the most controversial issues in wildlife management in North America is the trend towards the commercialization of wildlife. The sale of hunting privileges and game ranching are forms of wildlife commercialization that have not been unanimously accepted, and widely opposing views exist on the merits and drawbacks of the use of economic incentives for the management of wild animals. In this essay the use of economics is explored from a theoretical "free market" perspective and from a more practical point of view. The issue of market failure is addressed and potential solutions are offered, such as tax incentives and government farm programs. Also the question of when market-oriented solutions are applicable to wildlife is discussed. We conclude that polarization of the issue is counterproductive and that some of the more innovative solutions to current wildlife management problems can be found between the opposite extremes of public ownership and the profit-motivated incentives offered by the market. 相似文献
996.
Suspended particulates in the Jamaican atmosphere 总被引:1,自引:0,他引:1
M. Davis C. Grant G. Ho-Yorck-Krui A. Johnson G. C. Lalor H. Robotham M. Vutchkov 《Environmental geochemistry and health》1997,19(1)
The results of a survey of air particulates at 23 sites across Jamaica for total suspended particulates (TSP), Al, Br, Cl, Na, Pb, and V, by instrumental neutron activation analysis (INAA) and X-ray fluorescence analysis (XRF) are reported. The geometric mean of TSP values, 35 g m-3, is well within the World Health Organisation's standard of 60 g m-3 for TSP, but in areas of high vehicular traffic density the TSP values exceeded this limit. The correlation coefficient between Br and Pb concentrations in the particulates was 0.92 and the Br/Pb ratio of 0.38 compares well with a ratio of 0.39 found in commercial petrol indicating that the exhaust from vehicular traffic is the major source of Pb in atmospheric particulate matter in Jamaica. 相似文献
997.
Valérie Fournier Jay A Rosenheim Jacques Brodeur Joselito M Diez Marshall W Johnson 《Ecological applications》2006,16(6):2382-2398
The combined impact of multiple plant parasites on plant performance can either be additive (the total damage equals the sum of the individual effects) or nonadditive (synergistic or antagonistic damage). Two statistical models are available for testing the independent (=additive) effects of two factors. Here we suggest that the natural history of the plant-parasite system should motivate the choice of a statistical model to test for additivity. Using in-field, manipulative experiments, we examined the interactions between the herbivorous mite Calacarus flagelliseta Fletchmann, De Moraes and Barbosa (Acari: Eriophyidae), the fungal pathogen Oidium caricae F. Noack (a powdery mildew), and their host plant Carica papaya L. in Hawaii. First, we found that herbivorous mites had a moderate negative effect on powdery mildew: when mites were absent, powdery mildew colonies were larger and more numerous. Second, we showed that each plant parasite, when evaluated alone, significantly reduced several measures of plant performance. Third, we found that the combined impact of mites and mildew on plant performance is mostly additive and, for a few variables, less than additive. Finally, we explored compensatory responses and found no evidence for nonlinearities in the relationship between plant performance and cumulative parasite impact. Plants are almost universally subject to attack by multiple herbivores and pathogens; thus a deeper understanding of how multiple plant parasites shape each other's population dynamics and plant performance is essential to understanding plant-parasite interactions. 相似文献
998.
999.
Mature female stages of Tanais cavolinii Milne Edwards are described according to degree of oostegite development. Sexual dimorphism of the chelipeds of copulatory males is explained functionally. An aberrant marsupium consisting of two closed ovisacs with a small slit for sperm transfer protects the brood from sudden unpredictable changes in salinity. Behavioural traits, courtship, copulation, and parental care are described and compared to those of Heterotanais oerstedi Kröyer. The different habitats selected by the two species are reflected by several adaptations in their morphology and behaviour as tube dwellers. A phenomenon unique among invertebrates is that the female T. cavolinii supplies additional yolk to the larvae just before their release. The production and timing of this food supply is described and its adaptive significance is discussed. 相似文献
1000.