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951.
952.
Durana N Navazo M Alonso L García JA Ilardia JL Gómez MC Gangoiti G 《Journal of the Air & Waste Management Association (1995)》2002,52(10):1176-1185
This paper presents results of the processing and validation of data collected by an automatic gas chromatograph (AGC). This system was used to monitor 62 volatile organic compounds (VOCs) in urban air in the Basque Country, Spain. The nonpolar compounds (C2-C10) identified-paraffins, olefins, aromatics, and chlorinated compounds-accounted for 88% of the mass of total non-methane hydrocarbons (TNMHCs) in ambient air. The evaluation of linearity, precision, detection limits (DLs), and stability of retention times (RTs) indicates that the equipment is suitable for measuring ambient air automatically for prolonged periods (6 months). The calibration of the equipment using response factors calculated on the basis of the effective carbon number (ECN) showed variations of over 10% for acetylene, isoprene, and n-hexane. The results provided by the automatic chromatograph correlated significantly with simultaneous results from other widely used techniques for determining VOCs in ambient air: (1) portable GC, equipped with photoionization detector (PID), and (2) active adsorption on Tenax-TA followed by thermal desorption and chromatographic analysis. 相似文献
953.
Interaction of limestone grains and acidic solutions from the oxidation of pyrite tailings 总被引:1,自引:0,他引:1
Simón M Martín F García I Bouza P Dorronsoro C Aguilar J 《Environmental pollution (Barking, Essex : 1987)》2005,135(1):65-72
To characterise the coatings formed and to analyse element partitioning between the aqueous and solid phase, suspensions were prepared with four grain sizes of limestone and three different amounts of acidic solution from oxidized pyrite tailings. In all cases, red coatings with three different layers covered the grain surface, sealing off the acidic solution. The inner layer was composed mainly of basaluminite, the middle layer of schwertmannite, and the outer layer of gypsum and jarosite. Zn, Cd and Tl were co-precipitated by Fe and Al; As and Pb were co-precipitated almost completely by Fe; and Cu formed mainly Cu sulphates. All trace elements reached almost total precipitation at pH 6.3, but the precipitation of As and Pb tended to decrease as the pH rose. Consequently, liming should be calculated so that the soil pH does not exceed 6.3. This calculation should take into account that the armouring of the limestone grains can cause underestimations in the amount of liming material needed. 相似文献
954.
Guerra-García JM García-Gómez JC 《Environmental pollution (Barking, Essex : 1987)》2005,135(2):281-291
Generally, harbours are polluted zones characterised by low values of hydrodynamism and oxygen in the water column and high concentrations of pollutants in sediments. The harbour of Ceuta, North Africa, has an unusual structure; it is located between two bays connected by a channel, which increases the water movement and exchange in the harbour, maintaining moderate oxygen levels in the water-sediment interface. Nevertheless, high concentration of organic matter, nutrients and heavy metals were measured in sediments from this harbour. Under these unusual conditions (high levels of pollution but total saturation of oxygen in the water column) we studied the responses of soft-bottom macrobenthic communities using uni and multivariate analyses. The number of species was similar inside and outside the harbour but the species composition differed between internal and external stations; oxygen levels seem to control the "quantity" of species whereas pollutants control the "quality" of them. 相似文献
955.
Jaimes-López JL Sandoval-Fernández J González-Ortíz E Vázquez-García M González-Macías U Zambrano-García A 《Journal of the Air & Waste Management Association (1995)》2005,55(6):841-846
Leakages of liquefied petroleum gas (LPG) are suspected to contribute greatly to ozone (O3) formation in Mexico City. We tested such a hypothesis by outdoor captive-air irradiation (CAI) experiments in the two largest Mexican metropolitan areas: Guadalajara (GMA) in 1997 and Mexico City (MCMA) in 2000. O3 was monitored in each city for 20 days (8:00 a.m.-6:00 p.m.) in smog chambers containing unaltered morning air or morning air enriched with either commercial LPG or LPG synthetic mixture 60/40 (propane and butane). Tested additions of both components were 35% (by volume) in GMA and 60% (by volume) in MCMA. The addition effects on O3 (max) were compared with effects from diluting LPG components or total nonmethane hydrocarbons (tNMHCs) by 50%. Diluting tNMHCs had the greatest absolute effect at both cities: it lowered O3 (max) by 24% in GMA and 55% in MCMA. Adding commercial LPG increased O3 (max) by 6% in GMA and 28% in MCMA; whereas adding LPG synthetic mixture 60/40 caused a similar increase in O3 (max), 4 and 21% in GMA and MCMA, respectively. Compared with dilution of tNMHCs, dilution of LPG-associated compounds had a smaller decreasing effect on O3 (max), only 4% in GMA and 15% in MCMA. These results show that commercial LPG and LPG synthetic mixture 60/40 affect O3 formation to a lesser extent than estimated previously. 相似文献
956.
Lacal J da Silva MP García R Sevilla MT Procopio JR Hernández L 《Environmental pollution (Barking, Essex : 1987)》2003,124(2):291-305
Sludge from mining exploitation can be a source of land and water contamination in the adjacent zone. Accidents such as the break of waste mining pools in the Aznalcollar Mine (Seville, Spain) in 1998 produce important ecological disasters. In this work is presented a study of the evolution of aqua regia leachable concentration and mobility of metals in sediment samples of Guadiamar River basin from the accident date up to 2001. The application of BCR standard extraction procedures provides valuable information about the mobility and toxicity of the spill and the metal mobility in Guadiamar River polluted sediments. As a rule, themobility of several metals in the initial sludge (sulphides) is low, except for copper. Otherwise, the results of aqua regia leachable concentration and mobility of metal obtained for sediments samples indicate that the cleaning and inertisation works carried out in the zone have been adequate but insufficient, being the metal levels observed in the zone are higher than natural levels. To establish the initial impact of the spill and the mobility changes with time, mineralogical composition of the pyritic sludge and its evolution after the natural weathering and after the induction, of accelerated ageing processes by light and temperature was studied in the laboratory. Oxidation of initial sulphides to sulphates was observed. Both environmental and laboratory oxidation of the metallic sulphides increase the mobility of all metals, especially of copper, zinc and lead. The proposed laboratory procedure allows to predict the changes in mobility and therefore in toxicity that can occur at short or long term after exposure of sludge at environ-mental conditions. The mobility results in sludge and sediment samples are interpreted in terms of the mineral composition of the samples. 相似文献
957.
Green lacewings in the carnea group of Chrysoperla engage in species-specific heterosexual duets using low-frequency substrate-borne signals. Within each species, both sexes sing nearly identical songs. Songs are the principal barriers to hybridization between sympatric species in the complex. Here, we investigated the responsiveness of males and females of Chrysoperla plorabunda to synthesized, prerecorded songs that differed from the species mean in the period between repeated volleys of abdominal vibration. We tested 15–16 males and 15–16 females using playbacks of two signals that gradually increased or decreased in volley period, starting at the species mean. We found that (1) duets during courtship are accurate, interactive, and adjustable by each participant; (2) in staged duets, both sexes respond best to song tempos near the mean volley period of their population, but can nonetheless maintain duets with signals of nearly twice, or half, the normal volley period; (3) individuals fine-tune their adjustments to signals of different volley periods by changing their own volley duration and latent period, or less often by inserting extra volleys or skipping every other volley; (4) males are significantly better at matching signals of changing tempo than females; and (5) the range of song responsiveness of C. plorabunda does not overlap the natural range of volley periods found in Chrysoperla adamsi, an acoustically similar sibling species, thus reaffirming strong behavioral isolation. In sum, the precise, almost unbreakable heterosexual duets characteristic of song species of the carnea group result from tight mutual feedback between partners. Effective reproductive isolation between species can be based on song differences alone. 相似文献
958.
J. R. García-March A. M. García-Carrascosa A. L. Peña Cantero Y.-G. Wang 《Marine Biology》2007,150(5):861-871
An investigation to characterize the causes of Pinna nobilis population structure in Moraira bay (Western Mediterranean) was developed. Individuals of two areas of the same Posidonia meadow, located at different depths (A1, −13 and A2, −6 m), were inventoried, tagged, their positions accurately recorded
and monitored from July 1997 to July 2002. On each area, different aspects of population demography were studied (i.e. spatial
distribution, size structure, displacement evidences, mortality, growth and shell orientation). A comparison between both
groups of individuals was carried out, finding important differences between them. In A1, the individuals were more aggregated
and mean and maximum size were higher (A1, 10.3 and A2, 6 individuals/100 m2; A1, x = 47.2 ± 9.9; A2, x = 29.8 ± 7.4 cm, P < 0.001, respectively). In A2, growth rate and mortality were higher, the latter concentrated on the largest individuals,
in contrast to A1, where the smallest individuals had the higher mortality rate [A1, L = 56.03(1 − e−0.17t
); A2, L = 37.59(1 − e−0.40t
), P < 0.001; mean annual mortality A1: 32 dead individuals out of 135, 23.7% and A2: 16 dead individuals out of 36, 44.4%, and
total mortality coefficients (z), z
A1(−30) = 0.28, z
A1(31–45) = 0.05, z
A1(46−) = 0.08; z
A2(−30) = 0.15, z
A2(31–45) = 0.25]. A common shell orientation N–S, coincident with the maximum shore exposure, was observed in A2. Spatial distribution
in both areas showed not enough evidence to discard a random distribution of the individuals, despite the greater aggregation
on the deeper area (A1) (A1, χ
2 = 0.41, df = 3, P > 0.5, A2, χ
2 = 0.98, df = 2 and 0.3 < P < 0.5). The obtained results have demonstrated that the depth-related size segregation usually shown by P. nobilis is mainly caused by differences in mortality and growth among individuals located at different depths, rather than by the
active displacement of individuals previously reported in the literature. Furthermore, dwarf individuals are observed in shallower
levels and as a consequence, the relationship between size and age are not comparable even among groups of individuals inhabiting
the same meadow at different depths. The final causes of the differences on mortality and growth are also discussed. 相似文献
959.
Mean predation rates (± SD) on egg cases of the skates Bathyraja macloviana, B. albomaculata, Amblyraja doellojuradoi, and Psammobatis spp. from the southwestern Atlantic were estimated to be 0.151 (±0.230), 0.423 (±0.344), 0.254 (±0.390), and 0.150 (±0.288), respectively. These estimates are within the ranges reported earlier (14–40%). Egg cases of B. albomaculata were preyed on in higher proportion than expected from their abundance and suffered a heavier predation rate where the snail Trophon acanthodes was present. Predation rates were not correlated with the thickness of the egg case wall, which indicates that other factors (ecological or chemical) could explain this pattern. Five types of boreholes were found in the egg cases: one was attributable to muricid gastropods, one to naticid gastropods, and a third type to an unknown gastropod (probably Fusitriton magellanicus); the remaining were of unknown origin. Cladistic analyses showed that skates are secondarily oviparous and have maximized adaptations for living in deep water. We suggest that oviparity in skates appeared as an adaptation to maximize fecundity (40–160 eggs per year, as compared to 2–18 pups annually or biannually in viviparous guitarfishes, the plesiomorphic sister clade of skates). If a predation rate of 24% (the mean of predation rates of all skate species studied to date) is applied to the range of fecundities reported for skates, the result is that 18–114 viable pups are produced annually per female skate. Even with a high mortality rate of 64% (the only direct estimate of natural mortality for any elasmobranch), each female skate produces 17–54 eggs annually. These values are higher than most elasmobranch fecundities. This maximization of fecundity is possible mainly because the fecundity of oviparous species is not limited by body size, as in viviparity. The protracted egg-laying season (4–12 months) of most skates (as in many other deep-sea fishes) maximizes the number of eggs laid.Communicated by P.W. Sammarco, Chauvin 相似文献
960.
K. Różański 《Environment international》1979,2(3):139-143
For over 20 years the radioactive noble gas 85Kr, the product of nuclear industry, has been released to the environment mainly from nuclear fuel reprocessing plants. Owing to its relatively long half-life and the absence of other appreciable sinks, a cumulative buildup of 85Kr in the atmosphere is observed. The mean 85Kr surface air activity in the northern hemisphere has increased from about 20 dpm/mmol Kr in 1950 to about 750 dpm/mmol Kr in 1977. In recent years, a substantial slow-down of the 85Kr emission rate to the atmosphere has been observed. The published data indicate rather good mixing of 85Kr in the northern hemisphere, but a gradient is observed in the southern hemisphere due to the fact that all nuclear fuel reprocessing plants are situated in the northern hemisphere and due to poor mixing of the atmosphere in the meridional direction.This paper summarizes nearly all of the data on 85Kr activity in the atmosphere published up to the middle of 1978. The spatio-temporal distribution of 85Kr atmospheric activity is discussed. Some forecasts of future 85Kr concentration in the atmosphere and its possible ecological consequences are also presented. 相似文献