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991.
We observed kelp gametophytes endophytic in the cell walls of 17 species of red algae from the San Juan Islands, Washington,
USA. Host algae were collected primarily from three sites dominated by different kelp assemblages, including (1) a subtidal
site dominated by Agarum fimbriatum Harvey, (2) a second subtidal site dominated by Nereocystis luetkeana (Mertens) Postels et Ruprecht, and (3) a floating dock on which the dominant kelp species were Alaria marginata Postels et Ruprecht, Laminaria groenlandica Rosenvinge, and Costaria costata (C. Agardh) Saunders. Most hosts were filamentous [e.g. Pleonosporium vancouverianum (J. Agardh) J. Agardh, Callithamnion acutum Kylin], or polysiphonous [e.g. Polysiphonia paniculata Montagne, Pterosiphonia dendroidea (Montagne) Falkenberg]; however, similar endophytes were also observed in membranous or bladed red algae [e.g. Membranoptera platyphylla (Setchell et Gardner) Kylin, Polyneura latissima (Harvey) Kylin]. Dozens to hundreds of separate kelp gametophytes were associated with single host thalli. In many cases,
the gametophytes developed conspicuous oogonia raised above the thallus surface on characteristic stalks. Presumed zygotes
developed through typical embryonic stages into juvenile sporophytes. We argue that the endophytic habit plays an important
role in the biology of kelp gametophytes.
Received: 5 May 1998 / Accepted: 6 May 1999 相似文献
992.
Results of field experiments using the Virginia Institute of Marine Science' Sea Carousel and tripod system reveal a highly dynamic sediment activity at the Clay Bank site in the York River. At the water-sediment interface, the critical bed shear stress for sediment erosion varied between 0.026 Pa and 0.1 Pa. For the well consolidated sediment below the interface, the critical bed shear stress increased significantly, to more than 0.6 Pa. The seasonal variation of erosion rate for the surficial sediment is significant. For the well consolidated sediment below the surficial sediment, however, the seasonal variation diminished and erosion rate approached a constant. Experimental results from the Carousel deployments imply that the erosion process for quasi-steady tidal flows is always near equilibrium. For this reason, a constant rate erosion model is proposed for the time during tidal acceleration phases. For other times, the erosion rate would be zero. The measured suspended sediment concentration at 10 cm above bed from the VIMS tripod system also Supports this model. 相似文献
993.
994.
Tanya Pankiw Robert E. Page Jr M. Kim Fondrk 《Behavioral ecology and sociobiology》1998,44(3):193-198
Foraging and the mechanisms that regulate the quantity of food collected are important evolutionary and ecological attributes
for all organisms. The decision to collect pollen by honey bee foragers depends on the number of larvae (brood), amount of
stored pollen in the colony, as well as forager genotype and available resources in the environment. Here we describe how
brood pheromone (whole hexane extracts of larvae) influenced honey bee pollen foraging and test the predictions of two foraging-regulation
hypotheses: the indirect or brood-food mechanism and the direct mechanism of pollen-foraging regulation. Hexane extracts of
larvae containing brood pheromone stimulated pollen foraging. Colonies were provided with extracts of 1000 larvae (brood pheromone),
1000 larvae (brood), or no brood or pheromone. Colonies with brood pheromone and brood had similar numbers of pollen foragers,
while those colonies without brood or pheromone had significantly fewer pollen foragers. The number of pollen foragers increased
more than 2.5-fold when colonies were provided with extracts of 2000 larvae as a supplement to the 1000 larvae they already
had. Within 1 h of presenting colonies with brood pheromone, pollen foragers responded to the stimulus. The results from this
study demonstrate some important aspects of pollen foraging in honey bee colonies: (1) pollen foragers appear to be directly
affected by brood pheromone, (2) pollen foraging can be stimulated with brood pheromone in colonies provided with pollen but
no larvae, and (3) pollen forager numbers increase with brood pheromone as a supplement to brood without increasing the number
of larvae in the colony. These results support the direct-stimulus hypothesis for pollen foraging and do not support the indirect-inhibitor,
brood-food hypothesis for pollen-foraging regulation.
Received: 5 March 1998 / Accepted after revision: 29 August 1998 相似文献
995.
Modeling of road traffic noise and estimated human exposure in Fulton County, Georgia, USA 总被引:1,自引:0,他引:1
Seong JC Park TH Ko JH Chang SI Kim M Holt JB Mehdi MR 《Environment international》2011,37(8):1336-1341
Environmental noise is a major source of public complaints. Noise in the community causes physical and socio-economic effects and has been shown to be related to adverse health impacts. Noise, however, has not been actively researched in the United States compared with the European Union countries in recent years. In this research, we aimed at modeling road traffic noise and analyzing human exposure in Fulton County, Georgia, United States. We modeled road traffic noise levels using the United States Department of Transportation Federal Highway Administration Traffic Noise Model implemented in SoundPLAN?. After analyzing noise levels with raster, vector and fa?ade maps, we estimated human exposure to high noise levels. Accurate digital elevation models and building heights were derived from Light Detection And Ranging survey datasets and building footprint boundaries. Traffic datasets were collected from the Georgia Department of Transportation and the Atlanta Regional Commission. Noise level simulation was performed with 62 computers in a distributed computing environment. Finally, the noise-exposed population was calculated using geographic information system techniques. Results show that 48% of the total county population [N=870,166 residents] is potentially exposed to 55 dB(A) or higher noise levels during daytime. About 9% of the population is potentially exposed to 67 dB(A) or higher noises. At nighttime, 32% of the population is expected to be exposed to noise levels higher than 50 dB(A). This research shows that large-scale traffic noise estimation is possible with the help of various organizations. We believe that this research is a significant stepping stone for analyzing community health associated with noise exposures in the United States. 相似文献
996.
Seong-Wan Kang Jong-In Dong Jong-Min Kim Woo-Chan Lee Won-Gu Hwang 《Journal of Material Cycles and Waste Management》2011,13(3):180-185
Various research has attempted to determine the proper treatment of sewage sludge, including thermal technologies. Efficient
thermal technologies have been focused on because of their energy saving/energy recovery. Gasification technology can be considered
one of these approaches. In this study, the characteristics of gasification reactions were investigated with the aim of finding
fundamental data for utilizing sewage sludge as an energy source. For the experiments on sewage sludge gasification reaction
characteristics, a laboratory-scale experimental apparatus was set up with a fluidizing bed reactor of 70-mm inner diameter
and 600-mm total height using an electric muffle furnace. The experimental materials were prepared from a sewage treatment
plant located in Seoul. The reaction temperature was varied from 630 to 860°C, and the equivalence ratio from 0.1 to 0.3.
The gas yields, compositions of product gas, and cold gas efficiencies of product gas were analyzed by GC/TCD and GC/FID installed
with a carboxen-1000 column. The experimental results indicated that 800°C, ER 0.2 was an optimum condition for sewage sludge
gasification. The maximum yield of product gas was about 44%. Producer gas from experiments was mainly composed of hydrogen,
carbon monoxide, carbon dioxide, and methane. The cold gas efficiency of sewage sludge gasification was about 68%. The H2/CO ratio and CO/CO2 ratio were about 1.1 and 1.4, respectively, in optimum reaction conditions. Gaseous pollutants such as SO2, HCl, NH3, H2S, and NO2 were also analyzed at various gasification/combustion conditions, and their gaseous products were compared, showing significantly
different oxidized product distributions. 相似文献
997.
Sieratowicz A Stange D Schulte-Oehlmann U Oehlmann J 《Environmental pollution (Barking, Essex : 1987)》2011,159(10):2766-2774
An OECD initiative for the development of mollusc-based toxicity tests for endocrine disrupters and other chemicals has recommended three test species with respective test designs for further standardisation. Preparing a subsequent pre-validation study we performed a reproduction test with Potamopyrgus antipodarum, determining the concentration range of the selected test substances, bisphenol A (BPA) and cadmium (Cd). At 16 °C, the recommended test temperature, the number of embryos in the brood pouch was increased by BPA and decreased by Cd (NOEC: 20 μg BPA/L and 1 μg Cd/L). Coinstantaneous BPA tests at 7 °C and 25 °C demonstrated a temperature dependency of the response, resulting in lower NOECs (5 μg/L respectively). As expected, reproduction in control groups significantly varied depending on temperature. Additional observations of the brood stock showed seasonal fluctuations in reproduction under constant laboratory conditions. The recommended temperature range and test conditions have to be further investigated. 相似文献
998.
Yankovich TL Kim SB Baumgärtner F Galeriu D Melintescu A Miyamoto K Saito M Siclet F Davis P 《Journal of environmental radioactivity》2011,102(1):26-34
To improve understanding of environmental tritium behaviour, the International Atomic Energy Agency (IAEA) included a Tritium and C-14 Working Group (WG) in its EMRAS (Environmental Modelling for Radiation Safety) program. One scenario considered by the WG involved the prediction of time-dependent tritium concentrations in freshwater mussels that were subjected to an abrupt increase in ambient tritium levels. The experimental data used in the scenario were obtained from a study in which freshwater Barnes mussels (Elliptio complanata) were transplanted from an area with background tritium concentrations to a small Canadian Shield lake that contains elevated tritium. The mussels were then sampled over 88 days, and concentrations of free-water tritium (HTO) and organically-bound tritium (OBT) were measured in the soft tissues to follow the build-up of tritium in the mussels over time.The HTO concentration in the mussels reached steady state with the concentration in lake water within one or two hours. Most models predicted a longer time (up to a few days) to equilibrium. All models under-predicted the OBT concentration in the mussels one hour after transplantation, but over-predicted the rate of OBT formation over the next 24 h. Subsequent dynamics were not well modelled, although all participants predicted OBT concentrations that were within a factor of three of the observation at the end of the study period. The concentration at the final time point was over-predicted by all but one of the models. The relatively low observed concentration at this time was likely due to the loss of OBT by mussels during reproduction. 相似文献
999.
Distribution of perfluorochemicals between sera and milk from the same mothers and implications for prenatal and postnatal exposures 总被引:1,自引:0,他引:1
Kim SK Lee KT Kang CS Tao L Kannan K Kim KR Kim CK Lee JS Park PS Yoo YW Ha JY Shin YS Lee JH 《Environmental pollution (Barking, Essex : 1987)》2011,159(1):169-174
The levels of six perfluorocarboxylates (PFCAs), four perfloroalkylsulfonates (PFASs), and one sulfonamide were measured in paired samples of maternal serum, umbilical cord serum, and breast milk. The maternal and cord sera were strongly correlated with each other for all measured compounds (r > 0.5 and p < 0.01). Nevertheless, there was a significant difference in compound composition profile between the two sera matrices, with a more depletion of the longer chain compounds in cord serum. The transfer efficiency values from maternal to cord serum (TFCS/MS) decreased by 70% with each increasing unit of -CF2 chain within a PFCA group, and for perfluorooctanesulfonate (PFOS), by a half compared to perfluorooctanoate (PFOA). In contrast to the strong correlation in concentrations between the two sera matrices, the pattern of compounds in breast milk differed considerably with those in sera. Accordingly, compound- and matrix-specific transfer must be considered when assessing prenatal and postnatal exposure. 相似文献
1000.
Lee C Kim Y Nagajyothi PC Thammalangsy S Goung SJ 《Environmental science and pollution research international》2011,18(5):743-755