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901.
Many of the products of the reaction of naphthalene (Naph) with the OH radical in a reaction chamber were identified. Previously unidentified products included 1,2-naphthoquinone (NQ), oxygenated indenes and benzopyrones. Possible pathways for the formation of 1,2-NQ and 1,4-NQ are proposed. In the chamber reactions, more 1,2-NQ than 1,4-NQ partitioned to the particle phase. From this result we infer that, in the atmosphere, the percentage of 1,2-NQ in the particle phase should be greater than that for the 1,4-NQ. Because both of these compounds are considered to be toxic, and since they appear in both the gas and particle phases in the reaction chamber, and by implication in the atmosphere, it is considered important that both the gas and particle phases of these two compounds should be measured to assess their impact on human health. 相似文献
902.
Omphalocele is one of the most common abdominal wall defects seen in the prenatal period. Once this diagnosis is confirmed, it is important to check the fetal karyotype and thoroughly assess the fetus for other malformations. Prenatal management involves serial assessment of fetal growth and prenatal testing to ensure fetal well-being. Closure of the abdominal wall and replacement of organs into the abdominal cavity can be done directly if the omphalocele is small or in a staged manner if the omphalocele is large. Successful outcomes for these neonates can be optimized with a multidisciplinary team approach to prenatal and postnatal management. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
903.
R. Douglas Wilson 《黑龙江环境通报》2008,28(7):619-625
Fetal thoracic lung anomalies are rare. The specific diagnosis can be made by utilizing ultrasound, magnetic resonance imaging (MRI), and Doppler studies. Perinatal surveillance is required for large lesions and mediastinal shift regardless of the pathological diagnosis. These can cause physiological changes in the cardiovascular system with resulting hydrops. In utero therapies are variable but with no large randomized trials to compare risks and benefits. In most cases of fetal lung lesions, continued observation with postnatal therapy is the outcome. When fetal hydrops is present or impending, in utero fetal therapy is required to try to reverse that pathological course associated with fetal or neonatal death. Maternal morbidity is increased with the development of MIRROR syndrome following the presence of long-standing fetal hydrops and possible surgical procedures. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
904.
Douglas M. Leahey Mervyn J.E. Davies L.A. Panek 《Journal of the Air & Waste Management Association (1995)》2013,63(3):257-259
Airborne particulate and soil materials sampled in the vicinity of a lead/zinc smelter and subsequently digested In nitric-perchloric acids have been analyzed using an inductively coupled plasma-atomic emission spectrometer (ICP/AES). The samples were collected in two communities; a study community situated immediately adjacent to the smelter complex and a control community some 50 kilometers distant. Enrichment of airborne as well as soil materials is discussed and there is evidence of lead, zinc, copper, cadmium, arsenic, and antimony enrichment from the smelting processes. In addition, an aqueous extraction of the airborne materials isolated sulfate, nitrate, fluoride, and ammonia and gave evidence of enrichment due to fugitive SO x , NO x , HF, and NH3 gaseous emissions. 相似文献
905.
Margaret E. M. Tolbert Johnson A. Kamalu Garnette D. Draper 《Journal of environmental science and health. Part. B》2013,48(5):575-585
Abstract The effects of divalent cations on gluconeogenesis in enzy‐matically isolated rat hepatic parenchymal cells were examined. Cadmium, zinc and copper decreased glucose production from lactate (10 mM). However, manganese at 0.05 to 1.0 mM levels stimulated gluconeogenesis by the cells and reduced the effects of the Cd+2, Zn+2 and Cu+2 on gluconeogenesis. The results indicate that under these in vitro conditions the cations altered an aspect of hepatic function—gluconeogenesis from lactate. 相似文献
906.
An experiment was conducted to determine the influence the time of brush-cutting can have on plant regrowth and attractiveness
to herbivores that browse in linear corridors. The influence of cutting time on leaf flush and senescence, shoot morphometry,
and biomass was measured for 3 consecutive years after initial brush-cutting. Results indicate that morphological and phenological
attributes of three woody deciduous plants were influenced by the timing of brush-cutting for up to 3 years after initial
cutting. Brush-cutting generally stimulated plants to produce larger than normal shoots and delay leaf senescence. The degree
to which plants were affected, however, varied with the timing of initial cutting and the species in question. Generally,
plants cut later in the year resprouted more vigorously and were taller in the third year after cutting but produced less
overall biomass than when cut earlier. In the years following brush-cutting, plants cut earlier flushed leaves earlier in
the spring but delayed leaf senescence in the fall when compared to uncut controls. Results of these trials suggest that brush-cutting
time influences plant response and several plant attributes known to influence plant attractiveness to moose and other herbivores.
We therefore recommend that roadside and railside vegetation management plans consider the influence of cutting time on plant
regrowth. Such considerations can ensure that brush is cut to reduce the attractiveness of plant regrowth in these linear
corridors, reduce the utilization of such brush by herbivores, and, as such, mitigate collision risk between motorists and
herbivores such as moose. 相似文献
907.
Land and water resource development can independently eliminate riparian plant communities, including Fremont cottonwood forest (CF), a major contributor to ecosystem structure and functioning in semiarid portions of the American Southwest. We tested whether floodplain development was linked to river regulation in the Upper Colorado River Basin (UCRB) by relating the extent of five developed land-cover categories as well as CF and other natural vegetation to catchment reservoir capacity, changes in total annual and annual peak discharge, and overall level of mainstem hydrologic alteration (small, moderate, or large) in 26 fourth-order subbasins. We also asked whether CF appeared to be in jeopardy at a regional level. We classified 51% of the 57,000 ha of alluvial floodplain examined along >2600 km of mainstem rivers as CF and 36% as developed. The proportion developed was unrelated to the level of mainstem hydrologic alteration. The proportion classified as CF was also independent of the level of hydrologic alteration, a result we attribute to confounding effects from development, the presence of time lags, and contrasting effects from flow alteration in different subbasins. Most CF (68% by area) had a sparse canopy (50% canopy cover occupied <1% of the floodplain in 15 subbasins. We suggest that CF extent in the UCRB will decline markedly in the future, when the old trees on floodplains now disconnected from the river die and large areas change from CF to non-CF categories. Attention at a basinwide scale to the multiple factors affecting cottonwood patch dynamics is needed to assure conservation of these riparian forests. 相似文献
908.
Degradation of warmwater streams in agricultural landscapes is a pervasive problem, and reports of restoration effectiveness
based on monitoring data are rare. Described is the outcome of rehabilitation of two deeply incised, unstable sand-and-gravel-bed
streams. Channel networks of both watersheds were treated using standard erosion control measures, and aquatic habitats within
1-km-long reaches of each stream were further treated by addition of instream structures and planting woody vegetation on
banks (“habitat rehabilitation”). Fish and their habitats were sampled semiannually during 1–2 years before rehabilitation,
3–4 years after rehabilitation, and 10–11 years after rehabilitation. Reaches with only erosion control measures located upstream
from the habitat measure reaches and in similar streams in adjacent watersheds were sampled concurrently. Sediment concentrations
declined steeply throughout both watersheds, with means ≥40% lower during the post-rehabilitation period than before. Physical
effects of habitat rehabilitation were persistent through time, with pool habitat availability much higher in rehabilitated
reaches than elsewhere. Fish community structure responded with major shifts in relative species abundance: as pool habitats
increased after rehabilitation, small-bodied generalists and opportunists declined as certain piscivores and larger-bodied
species such as centrarchids and catostomids increased. Reaches without habitat rehabilitation were significantly shallower,
and fish populations there were similar to the rehabilitated reaches prior to treatment. These findings are applicable to
incised, warmwater streams draining agricultural watersheds similar to those we studied. Rehabilitation of warmwater stream
ecosystems is possible with current knowledge, but a major shift in stream corridor management strategies will be needed to
reverse ongoing degradation trends. Apparently, conventional channel erosion controls without instream habitat measures are
ineffective tools for ecosystem restoration in incised, warmwater streams of the Southeastern U.S., even if applied at the
watershed scale and accompanied by significant reductions in suspended sediment concentration. 相似文献
909.
Yanca CA Barth DC Petterson KA Nakanishi MP Cooper JA Johnsen BE Lambert RH Bivins DG 《Journal of the Air & Waste Management Association (1995)》2006,56(12):1733-1742
Three new methods applicable to the determination of hazardous metal concentrations in stationary source emissions were developed and evaluated for use in U.S. Environmental Protection Agency (EPA) compliance applications. Two of the three independent methods, a continuous emissions monitor-based method (Xact) and an X-ray-based filter method (XFM), are used to measure metal emissions. The third method involves a quantitative aerosol generator (QAG), which produces a reference aerosol used to evaluate the measurement methods. A modification of EPA Method 301 was used to validate the three methods for As, Cd, Cr, Pb, and Hg, representing three hazardous waste combustor Maximum Achievable Control Technology (MACT) metal categories (low volatile, semivolatile, and volatile). The modified procedure tested the methods using more stringent criteria than EPA Method 301; these criteria included accuracy, precision, and linearity. The aerosol generation method was evaluated in the laboratory by comparing actual with theoretical aerosol concentrations. The measurement methods were evaluated at a hazardous waste combustor (HWC) by comparing measured with reference aerosol concentrations. The QAG, Xact, and XFM met the modified Method 301 validation criteria. All three of the methods demonstrated precisions and accuracies on the order of 5%. In addition, correlation coefficients for each method were on the order of 0.99, confirming the methods' linear response and high precision over a wide range of concentrations. The measurement methods should be applicable to emissions from a wide range of sources, and the reference aerosol generator should be applicable to additional analytes. EPA recently approved an alternative monitoring petition for an HWC at Eli Lilly's Tippecanoe site in Lafayette, IN, in which the Xact is used for demonstrating compliance with the HWC MACT metal emissions (low volatile, semivolatile, and volatile). The QAG reference aerosol generator was approved as a method for providing a quantitative reference aerosol, which is required for certification and continuing quality assurance of the Xact. 相似文献
910.
Douglas W. Dockery John D. Spengler Margaret P. Reed James Ware 《Environment international》1981,5(2):101-107
Using integrating NO2 diffusion dosimeters, personal, indoor and outdoor exposures were measured for nine families in Topeka, Kansas. NO2 exposures in homes that used gas for cooking were clearly different from those in homes that used electricity. The gas-cooking homes had indoor levels three times the outdoor levels. Members of the gas-cooking households had levels twice those of electric-cooking families and twice the outdoor levels. A linear model that includes outdoor concentrations and stove types explains 77% of the variance in observed NO2 exposure. The differential NO2 exposures in homes with and without gas stoves should be considered in epidemiologic studies of the health effects of air pollution. 相似文献