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181.
本文针对近年来出现在一些变电站SF6电压、电流互感器的液体硅橡胶绝缘护套出现龟裂老化这一现象,对发生老化的硅橡胶材料进行了性能测试和试验,并利用红外光谱分析、XPS分析、热失重等手段分析了其微观结构和物质组成的变化。研究发现老化后的液体硅橡胶中Si-C、Si-O官能团和Si、C、O元素的相对含量发生了变化,且随着老化程度的增加呈现出较为明显的规律,老化越严重,Si-C键含量越少,C元素的含量越少,O元素含量越多。本文认为,用官能团含量、元素相对含量可以准确地表征液体硅橡胶材料的老化程度。通过对不同老化程度的液体硅橡胶进行的憎水性、耐漏电起痕性能的试验也证实了本文的观点。 相似文献
182.
Abstract The Rhône delta is a typical microtidal estuary. River runoff spreads out into the Gulf of Lions as a surface plume influenced by the prevailing N or NW wind and the Liguro-Provençal-Catalan current. in the prodelta, sediments form a filter that traps radionuclides released by the different nuclear installations on the Rhône River and which are associated with fine particles. the horizontal distribution of various artificial radionuclides shows the highest concentrations at the Rhône River mouth. There,137Cs reaches 86.6 and 94.4 Bq·kg?1 dry wt. and is still present 10 miles away (32.5 Bq·kg?1 dry wt.) in the southwestward direction (influence of the general circulation). Data obtained in the sediment at Roustan station between 1980 and 1990 show that in 1990, 137Cs levels were similar to those found previous to the Chernobyl accident. 相似文献
183.
Exploring price effects on the residential water conservation technology diffusion process: a case study of Tianjin city 总被引:1,自引:1,他引:0
Reforms of the water pricing management system and the establishment of a flexible water pricing system are significant for cities in northern China to tackle their critical water issues. The WATAP (Water conservation Technology Adoption Processes) model is developed in order to capture the water conservation technology adoption process under different price scenarios with disaggregate water demands down to the end use level. This model is explicitly characterized by the technological selection process under maximum marginal benefit assumption by different categories of households. In particular, when households need to purchase water devices in the provision market with the consideration of complex factors such as the life span, investment and operating costs of the device, as well as the regulated water price by the government. Applied to Tianjin city, four scenarios of water price evolutions for a long-term perspective (from year 2011 to 2030) are considered, including BAU (Business As Usual), SP1 (Scenario of Price increase with constant annual rate), SP2 (Scenario of Price increase every four years) and SP3 (Scenario of Price increase with affordable constraint), considering many factors such as historic trends, affordability and incentives for conservation. Results show that on aggregate 2.3%, 11.0% and 18.2% of fresh water can be saved in the residential sector in scenario SP1, SP2 and SP3, respectively, compared with the BAU scenario in the year 2030. The water price signals can change the market shares of different water appliances, as well as the water end use structure of households, and ultimately improve water use efficiency. TheWATAP model may potentially be a helpful tool to provide insights for policy makers on water conservation technology policy analysis and assessment. 相似文献
184.
Studying evolutionary mechanisms in natural populations often requires testing multifactorial scenarios of causality involving direct and indirect relationships among individual and environmental variables. It is also essential to account for the imperfect detection of individuals to provide unbiased demographic parameter estimates. To cope with these issues, we developed a new approach combining structural equation models with capture-recapture models (CR-SEM) that allows the investigation of competing hypotheses about individual and environmental variability observed in demographic parameters. We employ Markov chain Monte Carlo sampling in a Bayesian framework to (1) estimate model parameters, (2) implement a model selection procedure to evaluate competing hypotheses about causal mechanisms, and (3) assess the fit of models to data using posterior predictive checks. We illustrate the value of our approach using two case studies on wild bird populations. We first show that CR-SEM can be useful to quantify the action of selection on a set of phenotypic traits with an analysis of selection gradients on morphological traits in Common Blackbirds (Turdus merula). In a second case study on Blue Tits (Cyanistes caeruleus), we illustrate the use of CR-SEM to study evolutionary trade-offs in the wild, while accounting for varying environmental conditions. 相似文献
185.
Jinbiao Ma Manman Du Can Wang Xinwu Xie Hao Wang Qian Zhang 《Frontiers of Environmental Science & Engineering》2021,15(3):47
186.
龙凤山大气气溶胶散射特性观测分析 总被引:1,自引:0,他引:1
利用2018年龙凤山区域大气本底站(简称龙凤山站)气溶胶散射系数、PM10质量浓度及常规气象观测资料,研究了东北本底地区气溶胶散射系数的变化特征.结果表明,2018年龙凤山站3个波长下气溶胶散射系数的均值为(194.1±202.4)Mm-1(450 nm)、(133.4±139.2)Mm-1(550 nm)、(81.8±85.3)Mm-1(700 nm).龙凤山地区散射系数具有明显的日变化特征,且不同季节的日变化特征具有较大区别.龙凤山地区地处相对洁净的背景地区,气溶胶散射系数水平相对较低,春季受局地及长距离风沙的影响散射系数均值较高,冬季东北地区采暖燃烧排放量比较大,大气层相对稳定,不利于气溶胶污染物的扩散,冬季气溶胶散射系数最高.夏秋季受湿沉降与植被条件的影响气溶胶散射系数最低.散射系数与PM10质量浓度相关性较好,相关系数r为0.82.龙凤山PM10的质量散射效率为3.6 m2·g-1(550 nm).2018年龙凤山PM10气溶胶的散射Angstrom指数(SAE)平均值为1.96±0.25,表明在观测期间气溶胶主要是以较小的粒子主导,夏季的SAE最大,秋季的SAE最低,春季和冬季居中. 相似文献
187.
为探讨邻苯二甲酸二(2-乙基己基)酯(di-(2-ethylhexyl)phthalate,DEHP)及其代谢产物邻苯二甲酸单-2-乙基己酯(mono-(2-ethylhexyl)phthalate,MEHP)对H295R细胞类固醇激素合成关键基因表达的影响,本实验将H295R细胞分别暴露于DEHP(0、1、10、100、1 000μmol·L-1)和MEHP(0、1、10、100、1 000μmol·L-1)24 h,用MTT法检测细胞活性,并应用荧光定量PCR法分析细胞类固醇激素合成过程中关键酶的基因表达水平。结果显示,1 000μmol·L-1DEHP和MEHP对H295R细胞染毒24 h显著降低H295R细胞活力,所以本研究采用了较低的染毒浓度(0、1、10和100μmol·L-1)对H295R细胞染毒24 h来评估DEHP和MEHP对H295R细胞类固醇激素合成通路的影响。1、10和100μmol·L-1DEHP显著增加醛固酮合成酶CYP11B2的基因表达水平。10μmol·L-1DEHP显著上调了3-β羟基类固醇脱氢酶(3β-HSD2)的基因表达水平。1、10和100μmol·L-1MEHP显著下调了3-β羟基类固醇脱氢酶(3β-HSD1和3β-HSD2)、17β羟基类固醇脱氢酶17β-HSD4、17α羟化酶/17,20裂解酶CYP17和芳香酶CYP19a的基因表达水平。10和100μmol·L-1MEHP染毒H295R 24 h显著下调了CYP21和STAR的基因表达水平,然而,10和100μmol·L-1MEHP显著上调了CYP11B2的基因表达水平。100μmol·L-1MEHP显著下调了17β-HSD1的基因表达水平。上述研究结果表明,DEHP、MEHP都可不同程度影响H295R细胞类固醇激素合成过程中关键基因的表达。MEHP可以通过抑制STAR基因的表达,从而将影响胆固醇在细胞内的转运;并能显著性抑制类固醇激素合成过程中CYP17、CYP19a、3β-HSD1、3β-HSD2、17β-HSD1、17β-HSD4、CYP21基因的表达,最终将抑制H295R细胞中类固醇激素的合成。与DEHP相比,MEHP对H295R细胞类固醇激素合成关键基因表达的影响较明显。 相似文献
188.
通过田间小区试验,研究了秸秆还田条件下不同氮肥用量对稻田田面水、渗漏水中氮素动态变化和淋失量的影响.结果表明,稻季秸秆还田量为6t/hm2,氮肥用量分别为0,120,180,240,300kg/hm2时,稻季田面水、渗漏水中无机氮(NH4+-N与NO3--N)浓度随氮肥用量的增加而显著增加,秸秆还田显著降低田面水和渗漏水中NH4+-N和NO3--N浓度;田面水中NH4+-N浓度在每次施肥后的第2d、NO3--N在第2~4d达到峰值,渗漏水中NH4+-N在每次施肥后的第2~4d, NO3--N在施基肥后的第20d左右达到峰值;不同处理田面水中NH4+-N、NO3--N的平均浓度及变幅分别为1.23±0.88(0.01~9.89)、1.14±0.18(0.14~2.86)mg/L,渗漏水中分别为1.78±1.60(0.03~22.66)、1.42±0.24(0.22~2.66)mg/L.稻田渗漏量与水稻移栽后天数呈极显著负相关,整个水稻生育期内的总渗漏量为298mm.不同施氮处理稻季NH4+-N、NO3--N的平均净淋失量分别为4.77±4.37 (0.45~12.33)、1.76±1.08(0.49~3.31)kg/hm2,占施氮量的2.57%~4.11%、0.41%~0.56%,氮素损失以NH4+-N为主. 相似文献
189.
Alice Rémy Arnaud Grégoire Philippe Perret Claire Doutrelant 《Behavioral ecology and sociobiology》2010,64(11):1839-1847
Badges of status, usually color patches, are hypothesized to serve as important signals within natural populations by communicating
an individual’s fighting ability or aggressiveness before an interaction ever takes place. These signals, which may evolve
via sexual and/or social selection, mediate intra-specific competition by influencing the outcome or escalation of contests
between individuals. The last 10 years saw the rise of interest in the role of ultraviolet (UV)-based coloration in intra-sexual
communication. However, the rare experimental studies that tested this hypothesis found opposite results, which may originate
from the different methodological procedures used to assess the badge of status theory. We present here the results of an
experiment testing whether male blue tits (Cyanistes caeruleus) respond differently to unfamiliar conspecifics presenting contrasted UV crest coloration. In an aviary, we simultaneously
presented two caged blue tits with enhanced (UV+) or reduced (UV−) crest coloration to a focal bird. We found that focal males
acted more aggressively towards the UV− males than UV+ males. In addition, focal males fed more often close to males that
were similar in brightness or duller than themselves. We conclude that, in blue tits, UV blue crest coloration affects both
social and aggressive responses towards unfamiliar individuals, and thus it has some properties of a badge of status. 相似文献
190.
Anderson Ribeiro Duarte Luiz Duczmal Sabino José Ferreira André Luiz F. Cançado 《Environmental and Ecological Statistics》2010,17(2):203-229
The geographic delineation of irregularly shaped spatial clusters is an ill defined problem. Whenever the spatial scan statistic
is used, some kind of penalty correction needs to be used to avoid clusters’ excessive irregularity and consequent reduction
of power of detection. Geometric compactness and non-connectivity regularity functions have been recently proposed as corrections.
We present a novel internal cohesion regularity function based on the graph topology to penalize the presence of weak links
in candidate clusters. Weak links are defined as relatively unpopulated regions within a cluster, such that their removal
disconnects it. By applying this weak link cohesion function, the most geographically meaningful clusters are sifted through
the immense set of possible irregularly shaped candidate cluster solutions. A multi-objective genetic algorithm (MGA) has
been proposed recently to compute the Pareto-sets of clusters solutions, employing Kulldorff’s spatial scan statistic and
the geometric correction as objective functions. We propose novel MGAs to maximize the spatial scan, the cohesion function
and the geometric function, or combinations of these functions. Numerical tests show that our proposed MGAs has high power
to detect elongated clusters, and present good sensitivity and positive predictive value. The statistical significance of
the clusters in the Pareto-set are estimated through Monte Carlo simulations. Our method distinguishes clearly those geographically
inadequate clusters which are worse from both geometric and internal cohesion viewpoints. Besides, a certain degree of irregularity
of shape is allowed provided that it does not impact internal cohesion. Our method has better power of detection for clusters
satisfying those requirements. We propose a more robust definition of spatial cluster using these concepts. 相似文献