首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   859篇
  免费   14篇
  国内免费   4篇
安全科学   43篇
废物处理   39篇
环保管理   128篇
综合类   135篇
基础理论   196篇
环境理论   2篇
污染及防治   231篇
评价与监测   68篇
社会与环境   25篇
灾害及防治   10篇
  2023年   6篇
  2022年   14篇
  2021年   26篇
  2020年   15篇
  2019年   23篇
  2018年   41篇
  2017年   28篇
  2016年   38篇
  2015年   26篇
  2014年   43篇
  2013年   67篇
  2012年   41篇
  2011年   56篇
  2010年   46篇
  2009年   46篇
  2008年   49篇
  2007年   51篇
  2006年   39篇
  2005年   29篇
  2004年   23篇
  2003年   14篇
  2002年   26篇
  2001年   13篇
  2000年   13篇
  1999年   11篇
  1998年   12篇
  1997年   3篇
  1996年   9篇
  1995年   8篇
  1994年   6篇
  1993年   5篇
  1992年   7篇
  1991年   6篇
  1990年   4篇
  1988年   5篇
  1987年   4篇
  1986年   3篇
  1984年   4篇
  1983年   2篇
  1982年   2篇
  1972年   1篇
  1965年   1篇
  1963年   1篇
  1962年   1篇
  1961年   1篇
  1958年   1篇
  1956年   1篇
  1943年   1篇
  1940年   1篇
  1934年   1篇
排序方式: 共有877条查询结果,搜索用时 15 毫秒
71.
Organochlorines are highly hydrophobic, synthetic organic pollutants that accumulate in the environment and in food webs. The primary route of human exposure to organochlorines is through food-mainly fat-rich food of animal origin such as meat, fish, and dairy products. Here we determined the presence and concentration of organochlorine residues in pasteurized milk from Mato Grosso do Sul, Brazil, to monitor consumer exposure to these contaminants. Organochlorine pesticides in milk samples were analyzed using solid phase extraction in octadecyl silica-prepacked columns and identified by gas chromatography using an electron capture detector. Of the 100 composite samples analyzed, more than 90% contained residues of organochlorine pesticides: aldrin was present in 44% of the samples, followed by ∑DDT (36%), mirex (34%), endosulfan (32%), chlordane (17%), dicofol (14%), heptachlor (11%) and dieldrin (11%). Compared to the values established by law, the concentration of the compounds in some samples was above the reference values. Given the importance that milk and its products have in the human diet, it is essential to know whether the levels of pesticide residues are kept well below the recommended levels to minimize the risk to human health.  相似文献   
72.
By using dialysis equilibrium experiments, the sorption of a branched nonylphenol isomer [4-(1-ethyl-1,3-dimethylpentyl)-phenol] (NP111) on various humic acids (HAs) isolated from river sediments and two reference HAs was studied. The HAs were characterized by solid-state 13C direct polarization/magic angle spinning nuclear magnetic resonance (13C DP/MAS NMR) spectroscopy. Sorption isotherms of NP111 on HAs were described by a linear model. The organic carbon-normalized sorption coefficient (KOC) ranged from 2.3 × 103 to 1.5 × 104 L kg−1. Interestingly, a clear correlation between KOC value and alkyl C content was observed, indicating that the aliphaticity of HAs markedly dominates the sorption of NP111. These new mechanistic insights about the NP111 sorption indicate that the fate of nonylphenols in soil or sediment depends not only on the content of HA, but also on its structural composition.  相似文献   
73.
Prescribed burning, in combination with mechanical thinning, is a successful method for reducing heavy fuel loads from forest floors and thereby lowering the risk of catastrophic wildfire. However, an undesirable consequence of managed fire is the production of fine particulate matter or PM(2.5) (particles ≤2.5 μm in aerodynamic diameter). Wood-smoke particulate data from 21 prescribed burns are described, including results from broadcast and slash-pile burns. All PM(2.5) samples were collected in situ on day 1 (ignition) or day 2. Samples were analyzed for mass, polycyclic aromatic hydrocarbons (PAHs), inorganic elements, organic carbon (OC), and elemental carbon (EC). Results were characteristic of low intensity, smoldering fires. PM(2.5) concentrations varied from 523 to 8357 μg m(-3) and were higher on day 1. PAH weight percents (19 PAHs) were higher in slash-pile burns (0.21 ± 0.08% OC) than broadcast burns (0.07 ± 0.03% OC). The major elements were K, Cl, S, and Si. OC and EC values averaged 66 ± 7 and 2.8 ± 1.4% PM(2.5), respectively, for all burns studied, in good agreement with literature values for smoldering fires.  相似文献   
74.
75.
We investigated the efficiency of various by-products (sugarbeet lime, biosolid compost and leonardite), based on single or repeated applications to field plots, on the establishment of a vegetation cover compatible with a stabilization strategy on a multi-element (As, Cd, Cu, Pb and Zn) contaminated soil 4-6 years after initial amendment applications. Results indicate that the need for re-treatment is amendment- and element-dependent; in some cases, a single application may reduce trace element concentrations in above-ground biomass and enhance the establishment of a healthy vegetation cover. Amendment performance as evaluated by % cover, biomass and number of colonizing taxa differs; however, changes in plant community composition are not necessarily amendment-specific. Although the translocation of trace elements to the plant biotic compartment is greater in re-vegetated areas, overall loss of trace elements due to soil erosion and plant uptake is usually smaller compared to that in bare soil.  相似文献   
76.
Dissipation curves of azoxystrobin and of the neonicotinoids acetamiprid and thiacloprid in peach; azinphos-methyl and carbaryl in pear and azoxystrobin, chlorfenapyr and chlorpyrifos in high-tunnel tomato crops were studied in the Southern region of Uruguay. An analytical methodology based on solid phase extraction (SPE) and detection by High Performance Liquid Chromatography with Diode Array Detector (HPLC/DAD) was used for acetamiprid and thiacloprid. Coupled SPE and detection by Gas Chromatography with Mass Selective Detector (GC/MSD) was used for the detection of azinphos-methyl, azoxystrobin, carbaryl, chlorfenapyr and chlorpyrifos residues. Curves were modeled mathematically with Solver program of Microsoft Excel. The best fit for acetamiprid and thiacloprid in peach was achieved with the exponential model (r(2)=0.961 and 0.944, respectively). In the case of peach fruits there is not a Maximum Residue Limit (MRL) for acetamiprid in the Codex Alimentarius, while 0.5 mg/kg is the value rated for thiacloprid. The MRLs accepted by the European Union (EU) are 0.1 mg/kg for acetamiprid and 0.3 mg/kg for thiacloprid. According to the curves determined in these experiments, thiacloprid residues 10 to 12 days after application (daa) were below the MRLs established by both sources. In the case of acetamiprid, 25 daa would be required, according to the exponential mathematical model, to get residues levels below the MRL values established by the EU. For azinphos methyl in pear, the residues detected were mathematically fitted to an exponential model (r(2)=0.999). According to it, residue levels under the MRL established by the EU (0.05 mg/kg) are gotten in our conditions in 20 daa. In plastic tunnel tomato chlorfenapyr residues were not detected from 16 daa, having the dissipation curve an exponential trend. In the same condition, there was not a decay of the azoxystrobin concentration during a 24-day trial, being it around 0.40 ± 0.05 mg/kg.  相似文献   
77.
To restore food security to a traditional African cropping system following a sudden loss of seed, genetic diversity must be re-established. This study examines the extent to which Cowpea diversity was reinstated two years after a flood disaster in Gaza Province, Mozambique. The contribution that seed from various sources made to the recovery was assessed using semi-structured interviews and morphological and molecular data. Data suggest that diversity had recovered to some extent yet there was evidence of a narrowing of the genetic base, with fewer rare alleles and differences in the distribution of allele frequencies. Although the main channels for accessing seed after the flood were seed relief and markets, these sources contributed to minimal and different diversity. It appears that diversity was regained primarily through social networking in the form of loans or gifts of seed from friends and relatives. The results of the study are discussed in relation to seed relief approaches.  相似文献   
78.
Sustainable product development is closely related to sustainable consumption. The understanding of consumers' purchase, use and discard behaviours may facilitate the identification of requirements to guide manufacturers in the development of sustainable goods and services. The aim of this paper is to investigate consumers' perception about factors that motivate or discourage the consumption of sustainable products to identify demands and convert them into requirements. South Brazilian green and traditional consumers were asked to complete an exploratory qualitative questionnaire. Their answers were organized and compared to identify differences and similarities between the demands of these two groups. Furthermore, demands were converted into requirements for packages, products, manufactures, stores planning and discard systems. The interpretation of factors that motivate or discourage the purchase of sustainable products given by interviewees led to the creation of a list of possible public policies or programmes, aiming to support sustainable consumption. The results demonstrate the necessity of further quantitative investigation between consumer groups, for validation purposes.  相似文献   
79.
While local food production may be beneficial in terms of developing the local economy and reducing greenhouse gases from transportation, sustainability strategies focused on local food production may generate their own risks due to yield variability. We have developed a robust optimization (RO) model to determine the minimum amount of land (cropland and pasture) required to grow food items that would satisfy a local population’s (accounting for gender and age) calorie and nutrient needs. This model has been applied to Boone County, Missouri, which has a population of approximately 170,000. Boone County is 1790 km2, with 16% of the land defined as cropland and 30% defined as pasture. The model includes 27 nutrients from 17 potential foods that could be produced: six fruits and vegetables, five grains and six animal-sourced foods. Yield estimates are based on the predominate methods of agriculture in the USA. We first run our model assuming no variability, using the midpoint yield estimates. Then, to quantify uncertainty in yield for different food types, we use historical yield data over 10 years to estimate this variability and run our RO model under these variability estimates. We compare the two model results to illustrate the impact of data uncertainty on meeting sustainable local food for communities. Solutions suggest that nutrition needs can be met for the Boone County population within the land area defined.  相似文献   
80.
Aquatic environments are often exposed to toxic heavy metals, which gain access to the food chain via microalgae and may cause severe problems at higher trophic levels. However, such a metabolic specificity can be taken advantage of in bioremediation strategies. The potential of a novel wild strain of Scenedesmus obliquus, previously isolated from a heavy metal-contaminated site in northern Portugal, to remove Zn from aqueous solutions was thus studied, using several initial concentrations. The removal extent reached its maximum by 1 day: 836.5 mg Zn/g biomass, at the initial concentration of 75 mg/L, mainly by adsorption onto the cell surface. Comparative studies encompassing a commercially available strain of the same microalgal species led to a maximum removal extent of only 429.6 mg Zn/g biomass, under identical conditions. Heat-inactivated cells permitted a maximum removal of 209.6 mg Zn/g biomass, at an initial concentration of 50 mg Zn/L. The maximum adsorption capacity of Zn, estimated via Langmuir’s isotherm, was 330 mg Zn/g biomass. Finally, Zn removal was highest at pH 6.0–7.0. It was proven, for the first time, that such a wild microalga can uptake and adsorb Zn very efficiently, which unfolds a particularly good potential for bioremediation. Its performance is far better than similar (reference) species, especially near neutrality, and even following heat-treatment.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号