全文获取类型
收费全文 | 7885篇 |
免费 | 65篇 |
国内免费 | 52篇 |
专业分类
安全科学 | 148篇 |
废物处理 | 481篇 |
环保管理 | 592篇 |
综合类 | 1093篇 |
基础理论 | 1675篇 |
环境理论 | 9篇 |
污染及防治 | 2712篇 |
评价与监测 | 748篇 |
社会与环境 | 519篇 |
灾害及防治 | 25篇 |
出版年
2023年 | 90篇 |
2022年 | 234篇 |
2021年 | 264篇 |
2020年 | 121篇 |
2019年 | 121篇 |
2018年 | 271篇 |
2017年 | 238篇 |
2016年 | 378篇 |
2015年 | 216篇 |
2014年 | 407篇 |
2013年 | 731篇 |
2012年 | 487篇 |
2011年 | 545篇 |
2010年 | 397篇 |
2009年 | 333篇 |
2008年 | 447篇 |
2007年 | 450篇 |
2006年 | 368篇 |
2005年 | 287篇 |
2004年 | 245篇 |
2003年 | 200篇 |
2002年 | 191篇 |
2001年 | 128篇 |
2000年 | 101篇 |
1999年 | 69篇 |
1998年 | 41篇 |
1997年 | 31篇 |
1996年 | 22篇 |
1995年 | 49篇 |
1994年 | 40篇 |
1993年 | 20篇 |
1992年 | 28篇 |
1991年 | 16篇 |
1990年 | 19篇 |
1989年 | 12篇 |
1988年 | 13篇 |
1985年 | 14篇 |
1967年 | 10篇 |
1966年 | 16篇 |
1965年 | 16篇 |
1964年 | 32篇 |
1963年 | 13篇 |
1962年 | 18篇 |
1961年 | 13篇 |
1960年 | 10篇 |
1959年 | 28篇 |
1958年 | 43篇 |
1957年 | 23篇 |
1956年 | 16篇 |
1955年 | 19篇 |
排序方式: 共有8002条查询结果,搜索用时 15 毫秒
21.
In multiphase systems capillary pressures play a significant role on fluid movement and retention. The facility to predict
the effect of different thermal remediation strategies requires the knowledge of the effect of temperature on capillary pressure-saturation
relationships in the soils.
The objective of recent study was (a) to develop a technique for routinely measuring the pressure-saturation curves of soil
samples saturated with a nonpolar liquid at different regulated temperatures (b) to build a database using the measured pressure-saturation
curves and the physical, chemical properties of the model soils (c) to establish the dependence of nonaqueous phase liquid
retention on the soil properties and the temperature.
The retention curves (extraction isotherms) with nonaqueous phase liquid were determined using a modified
pressure plate extractor. The wetting phase was a non-aromatic hydrocarbon distillation product. Pressure plates were designed and constructed in
the laboratory of our department. The temperature was held constant at 20, 40 and 60 ∘C.
Statistical analysis was performed involving selected soil parameters and the measured nonaqueous phase liquid retention data.
The results show that knowing some easily measurable soil parameters (bulk density, particle size distribution, humus and
lime content) we can estimate the nonaqueous phase liquid retention of the soils. The measured “extraction isotherms” provide
essential information about the temperature-dependency of pressure-saturation curves. 相似文献
22.
Montserrat Bacardit Lluís Camarero 《Atmospheric environment (Oxford, England : 1994)》2010,44(4):582-595
The chemistry of high mountain snowpacks is a result of the long-range atmospheric transport and deposition of elements. Pyrenean snowpacks contain information about the fluxes of elements over SW Europe in winter. Here we analysed Al, Ti, Mn, Fe, Ni, Cu, Zn, As, Se, Cd and Pb in the 2004–05 winter snowpack in the Central Pyrenees, at an altitude range of 1820–3200 m a.s.l. Ni, As, Se and Cd were not detected in most cases. The concentrations of the remaining elements were comparable to those found in other high mountain areas in Europe and North America considered representative of regional background of atmospheric deposition in populated areas. In contrast, our measurements were higher than those of polar areas, which represent the global background. Single measurements of concentrations and snow accumulation were subject to considerable spatial variability, which may be attributable to strong wind drift and other post-depositional processes. The major ions chemistry of the snow indicated three possible origins for the solutes: terrigenous dust, sea salt spray and polluting S and N aerosols. We found no association between Cu, Zn and Pb and any of these possible sources. This observation therefore indicates that these elements were not preferentially bound to any particular kind of aerosol. Snow collected at altitudes of up to 2050 m a.s.l. presented higher concentrations of several elements than snow above this altitude, thereby indicating a local influence. Snow collected above 2300 m a.s.l. was therefore more representative of broad regional inputs. At these higher altitudes, snow was not enriched in Al, Ti, Mn, Fe or As compared with the composition of the upper continental crust and the local lithology, and these elements (except Mn) appeared almost exclusively in the particulate fraction. This observation indicates that Al, Ti, Mn, Fe and As were present mainly as part of dust particles of terrigenous origin. In contrast, Cu, Zn, and Pb presented medium to high enrichment factors and showed a higher proportion of soluble forms, thereby indicating their polluting character. 相似文献
23.
Previous research indicates that the use of impression management is related to supervisor ratings of employee likeability and job performance. It has been argued, though, that employees might also use impression management so that their superiors will see them as ‘good soldiers’ who engage in high levels of organizational citizenship behaviors (OCBs). This study investigates the ways in which three types of impression management—namely, job‐focused, self‐focused, and supervisor‐focused tactics of impression management—influence supervisor ratings of OCB. Using a sample of 122 supervisor‐subordinate dyads, the findings indicate that supervisor‐focused tactics of impression management are positively related to OCB ratings, while job‐focused tactics are negatively related to such evaluations. Additionally, citizenship behaviors are positively related to supervisor liking of the employee and overall ratings of job performance. Finally, the results suggest that OCB ratings mediate the relationship between supervisor‐focused tactics of impression management and supervisor evaluations of employee likeability. Some implications of this study and directions for future research are also addressed. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
24.
Antioco López-Molina Richart Vázquez-Román M. Sam Mannan M. Guadalupe Félix-Flores 《Journal of Loss Prevention in the Process Industries》2013,26(5):887-894
An approach to reduce the probability of producing a domino effect in process industry is developed in this work. It is assumed that optimal layouts should include appropriate analysis to reduce risk during the process design stage. The model developed for this approach combines the estimation of probability of damage due to overpressure, proposed by Mingguang and Juncheng (2008), and escalation threshold values defined by Cozzani, Gubinelli, and Salzano (2006). These equations are combined with other typical layout constraints as well as bounding the probability constraint, which has resulted in a highly non-linear MINLP problem. Solving a case study used by other authors provides evidence for reliability of the developed approach. In this way, layouts are designed to reduce the escalation probability yielding safe distributions. 相似文献
25.
Ljiljana Medic Pejic Javier García Torrent Enrique Querol Kazimierz Lebecki 《Journal of Loss Prevention in the Process Industries》2013,26(6):1524-1529
The key objective of this paper is the presentation of a new risk assessment tool for underground coal mines based on a simplified semi-quantitative estimation and assessment method.In order to determine the risk of explosion of any work process or activity in underground coal mines it is necessary to assess the risk. The proposed method is based on a Risk Index obtained as a product of three factors: frequency of each individual scenario Pucm, associated severity consequences Cucm and exposure time to explosive atmospheres Eucm. The influence of exposure time is usually not taken into account up to now. Moreover, the exposure to explosive atmospheres may affect factors of hazardous event probability as much as its consequences. There are many definitions of exposure to explosive atmospheres but in the case of underground coal mines the exposure is defined as frequency risk of firedamp and coal dust. The risk estimation and risk assessment are based on the developed of a risk matrix.The proposed methodology allows not only the estimation of the explosion risk but also gives an approach to decide if the proposal investment is well-justified or not in order to improve safety. 相似文献
26.
Otávio José de Oliveira Camila Roberta Muniz Serra Pinheiro 《Journal of Cleaner Production》2009,17(9):883-885
Among the difficulties found in the implementation of ISO 14001 systems, resistance to change can always be found. It is mainly a consequence of the hurry to change, loss of focus, concentration of decision making at the level of top management, arbitrary imposition of objectives and results, faulty communication, and the absence of motivational and financial incentive for change.Therefore, the main objective of this paper is to present best practices with respect to the management of organizational change due to the implementation of ISO 14001 norms in two industrial companies in the Midwest region of the State of São Paulo – Brazil. 相似文献
27.
Michal Hejcman Michaela Klaudisová Pavla Hejcmanová Vilém Pavlů Martina Jones 《Agriculture, ecosystems & environment》2009,129(1-3):91-96
Calamagrostis villosa has recently expanded in Nardus stricta-dominated sub-alpine grassland of the Giant Mountains (Krkono?e/Karkonosze, the Czech Republic). To investigate whether this expansion has been promoted by high nitrogen deposition or by the cessation of agricultural management, grassland plots dominated by C. villosa were manipulated with four treatments: control (Con), fertilised (Fer), cut (Cut) and cut–fertilised (Cut–Fer). NH4NO3 was used at the rate of 30 kg N ha?1 and fertilisation and cutting were performed once a year after data collection in late July between 2000 and 2006.Plant species composition (analysed by RDA) was significantly influenced by cutting but not by fertilisation. Cutting reduced the cover, biomass, sward height and tiller density of C. villosa. Seedlings of N. stricta and panicles of C. villosa were recorded only in plots with cutting management.To investigate the effect of treatments on the spread of C. villosa, grassland sods dominated by N. stricta were transplanted into the experimental plots. Six years later, the density and cover of C. villosa spreading into the N. stricta sods were highest in Fer treatment.C. villosa was recognised as a defoliation-sensitive species and this sensitivity cannot be overcome by an increase in N supply. Recent expansion of C. villosa in the sub-alpine grassland can by explained by a long-term succession after the cessation of agricultural management and an increase in the N availability in recent decades. 相似文献
28.
Esther del Val Juan Carlos Senar Juan Garrido-Fernández Manuel Jarén Antoni Borràs Josep Cabrera Juan José Negro 《Die Naturwissenschaften》2009,96(7):797-801
Carotenoids may provide numerous health benefits and are also responsible for the integumentary coloration of many bird species. Despite their importance, many aspects of their metabolism are still poorly known, and even basic issues such as the anatomical sites of conversion remain controversial. Recent studies suggest that the transformation of carotenoid pigments takes place directly in the follicles during feather growth, even though the liver has been previously recognised as a storing organ for these pigments with a certain potential for conversion. In this context, we analysed the carotenoid profile of plasma, liver, skin and feathers of male Common Crossbills (Loxia curvirostra). Interestingly, the derivative feather pigment 3-hydroxy-echinenone was detected in the liver and in the bloodstream (i.e. the necessary vehicle to transport metabolites to colourful peripheral tissues). Our results demonstrate for the first time with empirical data that the liver may act as the main site for the synthesis of integumentary carotenoids. This finding contradicts previous assumptions and raises the question of possible inter-specific differences in the site of carotenoid conversion in birds. 相似文献
29.
María del Mar Delgado Vincenzo Penteriani Vilis O. Nams Letizia Campioni 《Behavioral ecology and sociobiology》2009,64(1):35-43
Moving and spatial learning are two intertwined processes: (a) changes in movement behavior determine the learning of the spatial environment, and (b) information plays a crucial role in several animal decision-making processes like movement decisions. A useful way to explore the interactions between movement decisions and learning of the spatial environment is by comparing individual behaviors during the different phases of natal dispersal (when individuals move across more or less unknown habitats) with movements and choices of breeders (who repeatedly move within fixed home ranges), that is, by comparing behaviors between individuals who are still acquiring information vs. individuals with a more complete knowledge of their surroundings. When analyzing movement patterns of eagle owls, Bubo bubo, belonging to three status classes (floaters wandering across unknown environments, floaters already settled in temporary settlement areas, and territory owners with a well-established home range), we found that: (1) wandering individuals move faster than when established in a more stable or fixed settlement area, traveling larger and straighter paths with longer move steps; and (2) when floaters settle in a permanent area, then they show movement behavior similar to territory owners. Thus, movement patterns show a transition from exploratory strategies, when animals have incomplete environmental information, to a more familiar way to exploit their activity areas as they get to know the environment better. 相似文献
30.