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   376篇
  免费   1篇
  国内免费   9篇
安全科学   15篇
废物处理   26篇
环保管理   25篇
综合类   47篇
基础理论   51篇
污染及防治   149篇
评价与监测   43篇
社会与环境   26篇
灾害及防治   4篇
  2023年   8篇
  2022年   27篇
  2021年   25篇
  2020年   10篇
  2019年   7篇
  2018年   14篇
  2017年   21篇
  2016年   21篇
  2015年   13篇
  2014年   23篇
  2013年   67篇
  2012年   15篇
  2011年   16篇
  2010年   12篇
  2009年   10篇
  2008年   12篇
  2007年   16篇
  2006年   9篇
  2005年   7篇
  2004年   9篇
  2003年   8篇
  2002年   8篇
  2001年   2篇
  1998年   1篇
  1997年   2篇
  1996年   1篇
  1995年   1篇
  1989年   1篇
  1988年   1篇
  1987年   1篇
  1985年   2篇
  1984年   1篇
  1983年   2篇
  1979年   1篇
  1975年   1篇
  1970年   1篇
  1969年   1篇
  1967年   1篇
  1965年   2篇
  1964年   1篇
  1963年   2篇
  1962年   1篇
  1956年   1篇
  1955年   1篇
排序方式: 共有386条查询结果,搜索用时 15 毫秒
91.
Abstract

Phosphorylation is an indispensable process for energy and signal transduction in biological systems. AlCl3 at 10 nM to 10 uM range activated in‐vitro [γ‐32P)ATP phosphorylation of the brain (tau) T protein in both normal human or E.coli expressed T forms; in the presence of the kinases P34, PKP, and PKC. However, higher concentrations of ALCl3 inhibited the T phosphorylation with P34, PKP, and PKC to a maximum at 1 mM level. AlCl3 at 100 uM to 500 uM range induced non‐enzymatic phosphorylation of T with γ‐ATP, γ‐GTP, and α‐GTP. AlCl3 activated histone phosphorylation by P34 in a similar pattern. The hyperphosphorylation of T by Al3+ was accompanied by molecular shift and mobility retardation in SDS‐PAGE. This may demonstrate the mechanism of the longterm neurological effect of Al3+ in human brain leading to the formation of the neurofibrillary tangles related to Alzeheimer's disease.  相似文献   
92.
93.
Sequential UV-biological degradation of chlorophenols   总被引:2,自引:0,他引:2  
Tamer E  Hamid Z  Aly AM  Ossama el T  Bo M  Benoit G 《Chemosphere》2006,63(2):277-284
The sequential UV-biological degradation of a mixture of 4-chlorophenol (CP), 2,4-dichlorophenol (DCP), 2,4,6-trichlorophenol (TCP), and pentachlorophenol (PCP) was first tested with each pollutant supplied at an initial concentration of 50 mg l(-1). Under these conditions, the chlorophenols were photodegraded in the following order of removal rate: PCP>TCP>DCP>CP with only CP and DCP remaining after 40 h of irradiation. The remaining CP (41 mg l(-1)) and DCP (13 mg l(-1)) were then completely removed by biological treatment with an activated sludge mixed culture. Biodegradation did not occur in similar tests conducted with a non-irradiated mixture due to the high microbial toxicity of the solution. UV treatment lead to a significant reduction of the phytotoxicity to Lipedium sativum but no further reduction of phytotoxicity was observed after biological treatment. Evidence was found that the pollutants were partially photodegraded into toxic and non-biodegradable products. When the pollutants were tested individually (initial concentration of 50 mg l(-1)), PCP, TCP, DCP, 4-CP were photodegraded according to first order kinetic model (r2>99) with half-lives of 2.2, 3.3, 5.7, and 54 h, respectively. The photoproducts were subsequently biodegraded. This study illustrates the potential of UV as pre-treatment for biological treatment in order to remove toxicity and enhance the biodegradability of organic contaminants. However, it also shows that UV treatment must be carefully optimized to avoid the formation of toxic and/or recalcitrant photoproducts and results from studies conducted on single contaminants cannot be extrapolated to mixtures.  相似文献   
94.
ABSTRACT: The northern regions of Iraq, an area comprised of mountains and undulating plains, has for centuries been the main granary for the country. Its agricultural production is largely dependent upon natural rainfall which ranges from about 300 to 1,000 mm/yr. Grain yields can be greatly improved by use of improved varieties and management practices. Equations are developed to show relationships between various hydrologic and meteorologic parameters with yields of wheat and barley. The amount of supplementary water needed to maximize grain yields is also shown.  相似文献   
95.
Two different microbial communities able to degrade atrazine (atz) were inoculated in four different soils. The most critical factor affecting the success of inoculation was the soil pH and its organic matter (OM) content. In two alkaline soils (pH > 7), some inoculations led immediately to a strong increase of the biodegradation rate. In a third slightly acidic soil (pH = 6.1), only one inoculum could enhance atz degradation. In a soil amended with organic matter and straw (pH = 5.7, OM = 16.5%), inoculation had only little effect on atz dissipation on the short as well as on the long-term. Nine months after the microflora inoculations, atz was added again and rapid biodegradation in all alkaline inoculated soils was recorded, indicating the long-term efficiency of inoculation. In these soils, the number of atz degraders was estimated at between 6.5 × 103 and 1.5 × 106 (g of soil)-1, using the most probable number (MPN) method. Furthermore, the presence of the atz degraders was confirmed by the detection of the gene atzA in these soils. Denaturing gradient gel electrophoresis (DGGE) analysis of the 16S rDNA genes indicated that the inoculated bacterial communities had little effect on the patterns of the indigenous soil microflora.  相似文献   
96.
BACKGROUND: This study investigated the impact of subjective reports of drowsy driving and non-driving duties on the falling asleep responses and road crash involvement of professional drivers in Crete. An attempt was also made to elucidate other driving parameters, such as freight transportation, which could be potential predictors of risky driving, after controlling for lifestyle patterns. METHOD: A sample of 317 professional drivers was studied through personal interviews. The interview questionnaire included items about sleep and fatigue as contributing factors to falling asleep probability and crash risk. In addition, the drivers reported the type of freight they carried in their last trip, as well as practices such as smoking and alcohol consumption. RESULTS: The first logistic regression analysis showed that the most significant predictors of falling asleep at the wheel were transportation of fruits/vegetables and livestock, non-driving hours of work, insufficient hours of sleep, and smoking. The second logistic regression analysis revealed all the previous items as powerful factors of crash probability, including the transportation of express freight and freezer. IMPACT: The findings of the current study are discussed as they pertain to directions for future studies and for the development of fatigue countermeasures.  相似文献   
97.
Waste by-pass cement dust was added in different percentages ranging from 2% to 10% to a standard mix for sewer pipes manufacture, as a substitute for expensive feldspar. It was found that a mix consisting of 45% kaolin, 36% ball clay, 9% grog and 10% by-pass dust and fired at a temperature of 1300 degrees C for 4 h yielded samples that meet the standards. It was possible to reach a water absorption of 4%, a modulus of rupture of 7.8 MPa and a resistance to acids and alkalis conforming with standard values. A test pipe was fabricated by vacuum extrusion using the suggested composition and was found to withstand a hydraulic pressure of 14 MPa for one minute without the appearance of any cracks.  相似文献   
98.
This paper summarises the behaviour of major and trace elements during hydrothermal alteration processes in the Vareilles albite deposit, Saint-Chély d' Apcher area (Lozère, France). Sampling focused mainly on fine- to medium-grained two-mica granite facies surrounding albitite veins in two open pits. The primary chemical variability inherent in sampling parent rock and analytical uncertainties can seriously affect element mobility calculations. Here we present a simple model that allows to discriminate between magmatic and alteration effects and to make a proper evaluation of the chemical changes that have caused the alteration. For this reason, a range of unaltered granites and albitites were sampled to evaluate the degree of parent rock heterogeneity. Duplicate measurements were performed by epithermal neutron activation analysis (ENAA) to obtain a reliable mean concentration for trace elements and to evaluate results reproducibility. ENAA measurements are completed by analysis of major elements by inductively coupled plasma-mass spectrometry (ICP-MS). The enrichment or depletion of an element during alteration, relative to its concentration in fresh parent rock, can be calculated on the basis of the assumed immobility of some elements during the process. In this study, we have assumed Ta as immobile element on the basis for his inert behaviour. The distinct differences in chemical change between altered and unaltered granite suggest the need to consider alteration event as an important parameter in evaluating granitic rocks for nuclear waste disposal.  相似文献   
99.
Agricultural crops are affected by climate change due to the relationship between crop development, growth, yield, CO2 atmospheric concentration and climate conditions. In particular, the further reduction in existing limited water resources combined with an increase in temperature may result in higher impacts on agricultural crops in the Mediterranean area than in other regions. In this study, the cropping system models CERES-Wheat and CROPGRO-Tomato of the Decision Support System for Agrotechnology Transfer (DSSAT) were used to analyse the response of winter durum wheat (Triticum aestivum L.) and tomato (Lycopersicon esculentum Mill.) crops to climate change, irrigation and nitrogen fertilizer managements in one of most productive areas of Italy (i.e. Capitanata, Puglia). For this analysis, three climatic datasets were used: (1) a single dataset (50?km?×?50?km) provided by the JRC European centre for the period 1975–2005; two datasets from HadCM3 for the IPCC A2 GHG scenario for time slices with +2°C (centred over 2030–2060) and +5°C (centred over 2070–2099), respectively. All three datasets were used to generate synthetic climate series using a weather simulator (model LARS-WG). Adaptation strategies, such as irrigation and N fertilizer managements, have been investigated to either avoid or at least reduce the negative impacts induced by climate change impacts for both crops. Warmer temperatures were primarily shown to accelerate wheat and tomato phenology, thereby resulting in decreased total dry matter accumulation for both tomato and wheat under the +5°C future climate scenario. Under the +2°C scenario, dry matter accumulation and resulting yield were also reduced for tomato, whereas no negative yield effects were observed for winter durum wheat. In general, limiting the global mean temperature change of 2°C, the application of adaptation strategies (irrigation and nitrogen fertilization) showed a positive effect in minimizing the negative impacts of climate change on productivity of tomato cultivated in southern Italy.  相似文献   
100.
Wildlife subsistence hunting is a major source of protein for tropical rural populations and a prominent conservation issue. The intrinsic rate of natural increase. (rmax) of populations is a key reproductive parameter in the most used assessments of hunting sustainability. However, researchers face severe difficulties in obtaining reproductive data in the wild, so these assessments often rely on classic reproductive rates calculated mostly from studies of captive animals conducted 30 years ago. The result is a flaw in almost 50% of studies, which hampers management decision making. We conducted a 15‐year study in the Amazon in which we used reproductive data from the genitalia of 950 hunted female mammals. Genitalia were collected by local hunters. We examined tissue from these samples to estimate birthrates for wild populations of the 10 most hunted mammals. We compared our estimates with classic measures and considered the utility of the use of rmax in sustainability assessments. For woolly monkey (Lagothrix poeppigii) and tapir (Tapirus terrestris), wild birthrates were similar to those from captive populations, whereas birthrates for other ungulates and lowland‐paca (Cuniculus paca) were significantly lower than previous estimates. Conversely, for capuchin monkeys (Sapajus macrocephalus), agoutis (Dasyprocta sp.), and coatis (Nasua nasua), our calculated reproductive rates greatly exceeded often‐used values. Researchers could keep applying classic measures compatible with our estimates, but for other species previous estimates of rmax may not be appropriate. We suggest that data from local studies be used to set hunting quotas. Our maximum rates of population growth in the wild correlated with body weight, which suggests that our method is consistent and reliable. Integration of this method into community‐based wildlife management and the training of local hunters to record pregnancies in hunted animals could efficiently generate useful information of life histories of wild species and thus improve management of natural resources.  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