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541.
铜锈环棱螺作为一种新兴的潜在生态毒理学模式生物,适宜实验条件是开展其室内毒理学研究的基础。在人为控制条件下,初步探讨了饵料、水深、底质、密度和钙离子浓度养殖条件对铜锈环棱螺成体生长的影响,并进一步对麻醉条件进行了筛选(Mg Cl2·2H2O、乙醇、丁香酚、盐酸普鲁卡因和MS-222)。结果表明:当投喂冰鲜小球藻、密度6个·L-1水体积、水深10~15cm、泥土底质并且水中钙离子浓度30 mg·L-1时,铜锈环棱螺的体重增长最为明显。麻醉效果表明,Mg Cl2·2H2O对成螺的麻醉时间短并且伤害小,可作为实验用麻醉剂首选。以上研究结果为发展以铜锈环棱螺为模式生物开展环境(生态)毒理学研究奠定了基础。 相似文献
542.
基于社会技术系统理论,将事故成因要素分为社会干预和技术控制两方面,并结合突变理论构建企业安全生产系统的尖点突变模型,分析事故可能发生的突变点及演变路径,为事故防控提供有针对性的决策依据。 相似文献
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545.
An M. Michelsen J. Thomas. McGuckin Donna Stumpf 《Journal of the American Water Resources Association》1999,35(3):593-602
ABSTRACT: Water providers nationwide are implementing nonprice conservation measures such as education, public information, appliance retrofit and ordinances, with the expectation that these programs will reduce residential water demand. However, little empirical information exists on the effectiveness of nonprice conservation programs in reducing water demand. Previous econometric studies indicate these programs have had minimal impact. We examine the types and number of major nonprice conservation programs that have been implemented during an 11-year period in seven cities in the southwestern United States. A cross sectional, monthly time series residential water demand model, with parameters to control for variation in prices, temperature, precipitation and other factors, was used to empirically investigate the effectiveness of nonprice conservation programs in reducing water demand. We found significant reductions in use ranging between 1.1 percent and 4.0 percent per program. Because of the lack of information, we were unable to distinguish the effectiveness of individual or specific types of programs. Beyond finding that nonprice programs can be effective in reducing demand, questions regarding the efficiency and benefits to be achieved by conservation remain. As a step towards separating and evaluating the effects of individual programs, program benefits and efficiency, we recommend that utilities maintain more detailed and consistent information regarding the implementation of their nonprice programs. 相似文献
546.
本文介绍了应用彩红外航片,黑白航片分析呼和浩特市城市居民区、工业区、商业贸易区布局结构的技术。 相似文献
547.
In order to evaluate the influence of particle size and particle concentration on the coagulation process, two kinds of particle suspensions, nanoparticles and microparticles,were employed to investigate the effect of particle size on coagulation mechanisms with varying coagulation parameters. Results showed that it is easier for nanoparticles to cause self-aggregation because of Brownian motion, while interception and sedimentation are the mainly physical processes affecting particle transport for microparticles, so they are more stable and disperse more easily. The particle size distribution and particle concentration had distinct influence on the coagulation mechanisms. Under neutral conditions, as the amount of coagulant increased, the coagulation mechanism for nanoparticles changed from charge neutralization to sweep flocculation and the nanoparticles became destabilized, re-stabilized and again destabilized. For microparticles, although the coagulation mechanism was the same as that of nanoparticles, the increased rate of aluminum hydroxide precipitation exceeded the adsorption of incipiently formed soluble alum species, resulting in the disappearance of the re-stabilization zone. Under acidic conditions, Brownian motion dominates for nanoparticles at low particle concentrations, while sweep flocculation is predominant at high particle concentrations. As for microparticles, charge neutralization and sweep flocculation are the mechanisms for low and high particle concentrations respectively.Under alkaline condition, although the mechanisms for both nano-and microparticles are the same, the morphology of flocs and the kinetics of floc formation are different. At low particle concentrations, nanoparticles have larger growth rate and final size of flocs, while at high particle concentrations, nanoparticles have higher fractal dimension and recovery factors. 相似文献
548.
Yuanyuan Sun Guiying Li Wanjun Wang Wenquan Gu Po Keung Wong Taicheng An 《环境科学学报(英文版)》2019,31(10):69-79
There is an urgent need for developing cost-effective methods for the treatment of perfluorooctanoic acid(PFOA)due to its global emergence and potential risks.In this study,taking surface-defective BiOCl as an example,a strategy of surface oxygen vacancy modulation was used to promote the photocatalytic defluorination efficiency of PFOA under simulated sunlight irradiation.The defective BiOCl was fabricated by a fast microwave solvothermal method,which was found to induce more surface oxygen vacancies than conventional solvothermal and precipitation methods.As a result,the asprepared BiOCl showed significantly enhanced defluorination efficiency,which was 2.7 and33.8 times higher than that of BiOCl fabricated by conventional solvothermal and precipitation methods,respectively.Mechanistic studies indicated that the defluorination of PFOA follows a direct hole(h~+)oxidation pathway with the aid of·OH,while the oxygen vacancies not only promote charge separation but also facilitate the intimate contact between the photocatalyst surface and PFOA by coordinating with its terminal carboxylate group in a bidentate or bridging mode.This work will provide a general strategy of oxygen vacancy modulation by microwave-assisted methods for efficient photocatalytic defluorination of PFOA in the environment using sunlight as the energy source. 相似文献
549.
An Notenbaert Stanley Nganga Karanja Mario Herrero Maute Felisberto Siboniso Moyo 《Regional Environmental Change》2013,13(2):459-470
Recent studies have projected significant climate change impacts in Africa. In order to understand what this means in terms of human well-being at local level, we need to understand how households can cope and adapt. This need has led many authors to argue for approaches to adaptation that are based on vulnerability analysis. Vulnerability is one of the key terms in the climate change literature, but little progress has been made in the field of its quantification. Typically, indicators are combined according to a weighing scheme, with the identification of indicators and the weighing schemes based on expert judgment rather than empirical evidence. In addition, most quantitative assessments are applied to countries or other administrative units, whereas managing climate risk has traditionally been the responsibility of households. We therefore focus on the adaptive capacity of households. We analyze the coping strategies and vulnerability to climatic stresses of agro-pastoralists in Mozambique and test the validity of a number of commonly used vulnerability indicators. We derive a household-level vulnerability index based on survey data. We find that only 9 out of 26 indicators tested exhibit a statistically significant relationship with households’ vulnerability. In total, they explain about one-third of the variation in vulnerability between households, confirming the need for more research on underlying determinants and processes of vulnerability. With inclusion of local knowledge, our study findings can be used for local targeting, priority setting and resource allocation. Complemented with studies analyzing climate change impacts and findings from country-level adaptive capacity studies, governmental policy can be informed. 相似文献
550.