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1.
A water quality assessment was conducted on three Appalachian streams polluted by coal mining at the Big South Fork National River and Recreation Area, Tennessee and Kentucky. Results showed that sulfate was an excellent parameter for detecting the effects of coal mining and that sulfate analyses used in conjunction with conductivity readings provided the best detection index. Acidity and pH readings were relatively insensitive indicators, reflecting the mining pollution only after sulfate concentrations already indicated severe pollution levels.Hydrologist, Big South Fork NRRA, during the study; presently at Cape Lookout National SeashoreHydrologist, NPS, during the study; presently with USDA-Forest Service, Washington, DC. 相似文献
2.
Grant R. Sutherland Elizabeth Baker Stuart Purvis-Smith Athel Hockey Ed Krumins Sam Z. Eichenbaum 《黑龙江环境通报》1987,7(3):197-202
Eleven pregnancies in ten patients at risk for the fragile X were monitored by amniocentesis or chorion villus biopsy and induction of the fragile site using thymidine, methotrexate and FUdR. Three female fetuses and one male fetus were found to have the fragile X. The results obtained using thymidine induction were superior to those using methotrexate induction and probably better than those obtained using FUdR induction. 相似文献
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A case of confined placental mosaicism (CPM) and maternal uniparental isodisomy 14 identified after placental karyotype revealed trisomy 14 in a newborn with intrauterine growth restriction (IUGR) and minor dysmorphic features is reported. During the second trimester of the pregnancy, multiple marker screening revealed an increased risk for Down syndrome of >1 in 10. The maternal serum human chorionic gonadotrophin (MShCG) was markedly elevated at 4.19 MoM. Amniocentesis revealed a normal 46,XX karyotype. Fetal growth restriction has been associated with elevated MShCG and placental aneuploidy with CPM for chromosomes 2, 7, 9 and 16. The present case of CPM for chromosome 14 was also associated with fetal growth restriction and elevated second trimester MShCG, suggesting a common link. Further studies need to be done to determine if indeed elevation of second trimester MShCG is associated with increased risk of CPM. The present case again demonstrates the need to perform placental karyotype in unexplained fetal growth restriction. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
6.
James L. Gould 《Behavioral ecology and sociobiology》1982,10(1):53-56
Summary The indication of distance in the honey bee dance-the number of meters signified by each waggle-varies by more than a factor of ten among geographic races. Experiments in which artificial swarms were offered a choice of nest boxes indicate that A. m. carnica, the long-distance German race, clearly prefers larger and more distant cavities than the intermediate-dialect Italian race, ligustica. From these results on preferred dispersal distance and cavity size, combined with a general trend among the many races of honey bee toward dialects adapted for indicating longer distances occurring in colder latitudes, I propose that the dialect is probably an adaptation to each race's typical foraging range. That range is in large part a necessary consequence of population size, which in turn is determined by the thermal load imposed on clusters by winters in different climates. 相似文献
7.
Sam Provoost M. Laurence M. Jones Sally E. Edmondson 《Journal of Coastal Conservation》2011,15(1):207-226
In coastal dunes, landscape changes are a rule, rather than an exception. This paper gives an overview of changes in landscape
and vegetation with a focus on the past century. The history of dunes is characterised by phases of sand drift, alternated
with geomorphological stability. The historical development of dune woodland during these stable phases has been documented
for sites all over Europe. Vegetation reconstructions of historical open dune habitats however is very difficult due to limited
preservation of fossil remains. People have drastically altered coastal dune landscapes through centuries of exploitation
and more recently development of the coast. Historical land use has generally pushed vegetation back into a semi-natural state.
During roughly the past century a tendency of increasing fixation and succession is observed on coastal dunes throughout northwest
Europe. Six causes of change are discussed. 1) Changes in land use, mainly abandonment of agricultural practices, have led
to the development of late successional stages such as scrub and woodland. 2) Crashing rabbit populations due to myxomatosis
in the 1950s caused vigorous grass growth and probably stimulated scrub development. 3) A general tendency of landscape fixation
is observed due to both natural and anthropogenic factors. 4) Eutrophication, mainly due to atmospheric nitrogen deposition
is clearly linked to grass encroachment on acidic but also on some calcareous dunes. 5) The impact of climate change on vegetation
is still unclear but probably lengthening of growing season and maybe enhanced CO2 concentrations have led to an acceleration of succession. 6) A general anthropogenisation of the landscape occurs with rapid
spread of non-native species as an important consequence. The reconstruction of a natural reference landscape is considered
largely unattainable because of irreversible changes and the long tradition of human impact, in many cases since the development
of the dunes. Two contradictory elements need reconciliation. First, the general acceleration of succession and scrub and
woodland development in particular is partly caused by a decreased anthropogenic interference in the landscape and deserves
more appreciation. Second, most biodiversity values are largely linked to open, early succession dune habitats and are threatened
by the same tendency. Apart from internal nature management, in which grazing plays an important part, re-mobilisation of
stable, senescent dunes is an important challenge for dune management. 相似文献
8.
Michael J. Miller Sam Wouthuyzen Gen Minagawa Jun Aoyama Katsumi Tsukamoto 《Marine Biology》2006,148(5):1101-1111
A survey for leptocephali around Sulawesi Island in the central Indonesian Seas during May 2001 found that the leptocephali
of the congrid eel, Ariosoma scheelei, were present in all seven areas that were sampled. A total of 551 leptocephali (22–166 mm TL) were collected, and A. scheelei was by far the most abundant species of leptocephali collected during the survey. The wide range of sizes in most areas indicated
that spawning had occurred during a period of several months in many different areas, although the exact spawning locations
were not determined. The larger size classes were more abundant in all areas except in Tomini Bay on the northeast side of
Sulawesi Island. The highest catch rates were observed at the eastern edge of the Java Sea and to the north in the Celebes
Sea near Makassar Strait. Premetamorphic leptocephali were also collected in surface samples at 11 stations (N=62), but metamorphosing leptocephali (N=86) were only caught in IKMT tows that fished from the surface to about 200 m. Metamorphosing leptocephali were collected
primarily at two stations in the Java Sea and Makassar Strait where a surface layer of lower-salinity water was detected.
Their total lengths (105.3–153.3 mm) and the largest premetamorphic individuals suggested that this species can reach maximum
sizes of about 165 mm before beginning to metamorphose. It is hypothesized that this species may be abundant in the Indonesian
Seas region and that it has ecological traits such as large size at recruitment and a small size at reproduction that have
made it successful in many regions of the Indo-Pacific. 相似文献
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