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91.
Liu W Kaufman SL Osmondson BL Sem GJ Quant FR Oberreit DR 《Journal of the Air & Waste Management Association (1995)》2006,56(4):444-455
TSI Inc. (Shoreview, MN) has introduced three new water-based condensation particle counters (WCPCS) that were designed to detect airborne particles larger than 2.5 nm (model 3786), 5 nm (model 3785), and either 10 or 20 nm (model 3782). These WCPCs are well suited for real-time, environmental monitoring of number concentration of airborne ultrafine particles. Their unique design incorporates the use of water as the working fluid instead of alcohol. Water is odor free, readily available, and eliminates the problem of water condensation and absorption into alcohol working fluids during operation in humid environments. In this study, the performance of three TSI WCPCs was characterized for several aerosol compositions, including sucrose, salt (NaCl), dioctyl sebacate (DOS), dioctyl phthalate (DOP), emery oil (poly-alpha-olefin), silver, impurity residue particles, and ambient aerosol particles. All particles were size selected using a nano differential mobility analyzer (nano-DMA; model 3085, TSI Inc.) to create monodisperse challenge aerosols. The challenge aerosol was mixed uniformly with clean makeup flow and split into a WCPC and a reference instrument to determine the counting efficiency of the WCPC. For the model 3785 WCPC, the D50 (i.e., the particle diameter with 50% counting efficiency) was determined to be 3.1 nm for salt particles, 4.7 nm for sucrose and ambient particles, 5.6 nm for silver particles, and >50 nm for ultrapure oil particles. The sensitivity to oil droplets increased dramatically (D50 < 10 nm) when the oil was slightly contaminated. The D50 of model 3786 ultrafine water-based CPC (UWCPC) was 2.4 nm for impurity residue particles. The D50 of the model 3782 WCPC was 10.8 (with a nominal setting of 10 nm) or 19.8 nm (with a nominal setting of 20 nm) for sucrose particles. All three WCPCs have response times of less than 2 or 3 sec and are therefore able to detect fast-changing events. 相似文献
92.
Abstract: Different deforestation agents, such as small farmers and large agricultural businesses, create different spatial patterns of deforestation. We analyzed the proportion of deforestation associated with different‐sized clearings in the Brazilian Amazon from 2002 through 2009. We used annual deforestation maps to determine total area deforested and the size distribution of deforested patches per year. The size distribution of deforested areas changed over time in a consistent, directional manner. Large clearings (>1000 ha) comprised progressively smaller amounts of total annual deforestation. The number of smaller clearings (6.25–50.00 ha) remained unchanged over time. Small clearings accounted for 73% of all deforestation in 2009, up from 30% in 2002, whereas the proportion of deforestation attributable to large clearings decreased from 13% to 3% between 2002 and 2009. Large clearings were concentrated in Mato Grosso, but also occurred in eastern Pará and in Rondônia. In 2002 large clearings accounted for 17%, 15%, and 10% of all deforestation in Mato Grosso, Pará, and Rondônia, respectively. Even in these states, where there is a highly developed agricultural business dominated by soybean production and cattle ranching, the proportional contribution of large clearings to total deforestation declined. By 2009 large clearings accounted for 2.5%, 3.5%, and 1% of all deforestation in Mato Grosso, Pará, and Rondônia, respectively. These changes in deforestation patch size are coincident with the implementation of new conservation policies by the Brazilian government, which suggests that these policies are not effectively reducing the number of small clearings in primary forest, whether these are caused by large landholders or smallholders, but have been more effective at reducing the frequency of larger clearings. 相似文献
93.
J. A. Brink JR. B. B. crocker 《Journal of the Air & Waste Management Association (1995)》2013,63(11):449-454
“Rules of thumb” for stack design have been developed for use on problems where extensive studies cannot be justified or where quantitative design data are unavailable. The application of these rules to a practical stack design problem is discussed. The IBM 704 computer has been used for rapid yet rigorous stack design studies. The computer procedures for design are discussed and its application to a practical problem is described in detail. 相似文献
94.
M. R. Timmins D. F. Gilmore N. Lotti M. Scandola R. C. Fuller R. W. Lenz 《Journal of Polymers and the Environment》1997,5(1):1-15
An assay method has been developed for monitoring the enzymatic degradation of thin films of translucent polymers. The method
was based on the observation that when a solution-cast film of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was exposed
to a solution of a depolymerase fromPseudomonas lemoignei, the surface of the film roughened and the film became visibly turbid. This increase in turbidity could be measured spectrophotometrically
and was reproducible during the initial stage of degradation. Turbidity correlated very closely with film weight loss early
in the degradation but reached a maximum value before extensive degradation had taken place. For a given set of films, this
correlation was independent of the concentration of the enzyme used, although it did vary with the mode of enzyme exposure.
The turbidity was associated with the exposure of crystalline domains due to the removal of amorphous material from the film
surface. The increase in crystallinity at the surface was verified by attenuated total reflectance infrared spectroscopy (ATRIR).
In conjunction with SEM, weight loss, and ATRIR, the film turbidity assay provided much semiquantitative insight into the
mechanism of the enzymatic degradation reaction. This assay was used to study the enzymatic degradation of films of PHBV solution
blended with cellulose acetate esters (CAE). The presence of only 25% of CAE of degree of substitution 2.9 severely hampered
the enzymatic degradability of PHBV, a result which is consistent with the environmental degradation of these same samples
exposed to activated sludge. 相似文献
95.
Taxodium distichum (L.) Rich.]. The study site, a swamp in St. Martin Parish, Louisiana, has received municipal wastewater for the last 40 years.
Growth chronologies from 1920 to 1992 were developed from cross-dated tree core samples taken from treated and control sites
with similar size and age classes. Mean diameter increment (DINC) and mean basal area increment (BAI) chronologies were constructed
separately for each stand. These chronologies were then summarized by tree and stand into seven nine-year intervals resulting
in three pretreatment intervals from 1926 to 1952 and four treatment intervals from 1953 to 1988. Significant differences
in growth response between sites showed a consistent pattern of growth enhancement in the treated site coincident with the
onset of effluent discharge. The ratio of treated to control baldcypress growth rates (computed from DINC) averaged 0.74 during
the pretreatment period and 1.53 during the treatment period. Over the period of study, control DINC decreased from 77 mm
to 29 mm/nine-year interval, while treatment DINC increased slightly from 40 mm to 47 mm/nine-year interval. Control BAI did
not increase significantly and averaged 192 cm2/nine-year interval. There was a significant increase in treatment BAI from 129 to 333 cm2/nine-year interval over the period of record. These results clearly demonstrate sustained long-term baldcypress growth enhancement
throughout 40 years of municipal effluent discharge. 相似文献
96.
Trisorny 18 mosaicism was found in multiple primary cultures of amniotic fluid cells and subsequently confirmed by chromosome analysis of several tissues derived from the aborted fetus. The overall frequency of the minority cell line was 25 per cent in the amniotic fluid cultures and 28 per cent in the fetal tissues although much intertissue variations were noted. 相似文献
97.
Paul E. Bibbins JR. Robert L. Anderson Dr. Jack M. Rary Howard W. Jones JR. 《黑龙江环境通报》1982,2(2):123-125
A 48,XXYY fetus was diagnosed prenatally in a 34-year old female who was seen at 18-5 weeks of pregnancy for genetic counselling and amniocentesis for advanced maternal age. The pregnancy was terminated, and skin and peripheral blood samples were obtained at the time of delivery. These samples also exhibited the 48,XXYY chromosomal complement. 相似文献
98.
Changing the Course of Biodiversity Conservation in the Caatinga of Northeastern Brazil 总被引:3,自引:0,他引:3
INARA R. LEAL§ JOSÉ MARIA CARDOSO DA SILVA† MARCELO TABARELLI THOMAS E. LACHER JR. ‡ 《Conservation biology》2005,19(3):701-706
Abstract: The 735,000-km2 Caatinga is a mosaic of thorn scrub and seasonally dry forests, with more than 2000 species of vascular plants, fishes, reptiles, amphibians, birds, and mammals. Endemism in these groups varies from 7% to 57%. Inappropriate land use has already caused serious environmental damage and accelerating desertification, which is currently threatening about 15% of the region. Moreover, the rich and diversified biota of the Caatinga is poorly protected: only 11 reserves (<1% of the region) are strictly protected areas. A conservation strategy for the Caatinga biota should be designed to (1) avoid further habitat loss and desertification, (2) maintain key ecological services necessary for improving the living standards of the rural population, and (3) promote the sustainable use of the region's natural resources. Implementing an effective conservation agenda for the Caatinga is not an easy task but, with creativity and consistent financial support, it should be possible to nurture this unique biome and guarantee the preservation of its rich and diversified fauna and flora, and, with this, the well-being of its rural populations. 相似文献
99.
Effects of the Interaction between Genetic Diversity and UV-B Radiation on Wood Frog Fitness 总被引:1,自引:0,他引:1
Abstract: Genetic diversity may buffer amphibian populations against environmental vicissitudes. We hypothesized that wood frogs ( Rana sylvatica ) from populations with lower genetic diversity are more susceptible to ultraviolet-B (UV-B) radiation than those from populations with higher diversity. We used RAPD markers to obtain genetic diversity estimates for 12 wood frog populations. We reared larval wood frogs from these populations and exposed experimental groups of eggs and larvae to one of three treatments: unfiltered sunlight, sunlight filtered through a UV-B-blocking filter (Mylar), and sunlight filtered through a UV-B-transmitting filter (acetate). In groups exposed to UV-B, larval mortality and deformity rates increased significantly, but egg mortality did not. We found a significant negative relationship between genetic diversity and egg mortality, larval mortality, and deformity rates. Furthermore, the interaction between UV-B treatment and genetic diversity significantly affected larval mortality. Populations with low genetic diversity experienced higher larval mortality rates when exposed to UV-B than did populations with high genetic diversity. This is the first time an interaction between genetic diversity and an environmental stressor has been documented in amphibians. Differences in genetic diversity among populations, coupled with environmental stressors, may help explain patterns of amphibian decline. 相似文献
100.
A pilot study of the relationship between multiple sclerosis and the physical environment in northwest Ireland 总被引:1,自引:0,他引:1
Multiple sclerosis (MS) is a neurological disease of unknown origin, but it is thought likely to have an environmental component in addition to genetic predisposition. It appears common in areas with underlying radon-producing granites. Radon exposure before the age of 15 years is postulated as a contributory cause in genetically susceptible individuals. Pilot studies were undertaken, with results which indicate that radon exposure may be a factor, and that the hypothesis warrants further investigation. 相似文献