全文获取类型
收费全文 | 877篇 |
免费 | 13篇 |
国内免费 | 12篇 |
专业分类
安全科学 | 37篇 |
废物处理 | 46篇 |
环保管理 | 144篇 |
综合类 | 143篇 |
基础理论 | 179篇 |
污染及防治 | 228篇 |
评价与监测 | 86篇 |
社会与环境 | 36篇 |
灾害及防治 | 3篇 |
出版年
2023年 | 7篇 |
2022年 | 20篇 |
2021年 | 18篇 |
2020年 | 15篇 |
2019年 | 13篇 |
2018年 | 19篇 |
2017年 | 26篇 |
2016年 | 38篇 |
2015年 | 26篇 |
2014年 | 47篇 |
2013年 | 69篇 |
2012年 | 59篇 |
2011年 | 71篇 |
2010年 | 42篇 |
2009年 | 38篇 |
2008年 | 57篇 |
2007年 | 43篇 |
2006年 | 50篇 |
2005年 | 34篇 |
2004年 | 34篇 |
2003年 | 29篇 |
2002年 | 23篇 |
2001年 | 6篇 |
2000年 | 9篇 |
1999年 | 7篇 |
1998年 | 6篇 |
1997年 | 5篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 8篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1963年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有902条查询结果,搜索用时 15 毫秒
871.
Patricia Prado Catherine J. Collier Javier Romero Teresa Alcoverro 《Marine Biology》2011,158(7):1473-1482
Herbivory is now recognized as an important structuring agent in seagrass meadows but the attack pattern and tissue damage
of consumers are highly variable. Nutritional preferences of herbivores and/or easy access to resources may cause differences
in biomass loss among tissues that damage the plant in functionally distinctive ways. The two main Mediterranean herbivores,
the fish Sarpa salpa (L.) and the sea urchin Paracentrotus lividus (Lmk.), remove higher amounts of intermediate and external shoot leaves, respectively. To test whether this selective feeding
can have different consequences on the allocation patterns of nutrient within plants, we simulated the effect of both herbivores
by clipping external and intermediate leaves (plus unclipped controls) of Posidonia oceanica (L.) and we measured plant tolerance in terms of shoot growth and leaf nutrient supply to new tissue using isotopic markers.
As expected, control treatments displayed high carbon and nutrient supply from external leaves (83% of the total 15N and 84% of the total 13C incorporated by the shoot). When subjected to clipping, the remaining leaves enhanced carbon and nitrogen supply compared
with the control by 16% of N and 36% of C—in the intermediate clipping—and by over 100% of N and 200% of C—in the external
clipping—to compensate for the nutrient lost. However, only in the case of fish herbivory (intermediate clipping), enhanced
supply alone was able to fully compensate for the nutrient losses. In contrast, this mechanism is not completely effective
when external leaves are clipped (urchin herbivory). Yet, the consequences of this nutrient loss under sea urchin herbivory
are not apparent from the nutrient content of the new tissue, suggesting that there are other sources of nitrogen income (uptake
or reallocation from rhizomes). Our study does not only confirm the tolerance of P. oceanica to herbivory, but also constitutes the first evidence of leaf-specific, compensatory nutrient supply in seagrasses. 相似文献
872.
Comparing Hydrogeomorphic Approaches to Lake Classification 总被引:1,自引:1,他引:0
A classification system is often used to reduce the number of different ecosystem types that governmental agencies are charged with monitoring and managing. We compare the ability of several different hydrogeomorphic (HGM)—based classifications to group lakes for water chemistry/clarity. We ask: (1) Which approach to lake classification is most successful at classifying lakes for similar water chemistry/clarity? (2) Which HGM features are most strongly related to the lake classes? and, (3) Can a single classification successfully classify lakes for all of the water chemistry/clarity variables examined? We use univariate and multivariate classification and regression tree (CART and MvCART) analysis of HGM features to classify alkalinity, water color, Secchi, total nitrogen, total phosphorus, and chlorophyll a from 151 minimally disturbed lakes in Michigan USA. We developed two MvCART models overall and two CART models for each water chemistry/clarity variable, in each case comparing: local HGM characteristics alone and local HGM characteristics combined with regionalizations and landscape position. The combined CART models had the highest strength of evidence (ωi range 0.92–1.00) and maximized within class homogeneity (ICC range 36–66%) for all water chemistry/clarity variables except water color and chlorophyll a. Because the most successful single classification was on average 20% less successful in classifying other water chemistry/clarity variables, we found that no single classification captures variability for all lake responses tested. Therefore, we suggest that the most successful classification (1) is specific to individual response variables, and (2) incorporates information from multiple spatial scales (regionalization and local HGM variables). 相似文献
873.
Karla Patricia Oliveira-Esquerre Mario Cezar Mattos 《Resources, Conservation and Recycling》2011,55(3):316-324
A methodology for water use minimization has been developed by the Clean Technology Network of Bahia over a 10 year period in joint cooperative programs with the chemical, petrochemical and copper metallurgy industries located in the largest Industrial Complex in Latin America, in Camaçari, Bahia, Brazil. The methodology comprises a set of tools including reconciled aqueous stream balances, database of aqueous streams; large scale training leading to the identification of water minimization alternatives in the processes, water reuse optimization approaches; geographical information systems as well as, consideration of the region's hydro and hydro-geological characteristics. The results of a study carried out to assess the possibility of using storm and wastewaters for industrial use is presented in this paper. The inorganic system is composed by three water reservoirs (basins) receiving stormwater contaminated with inorganic effluents, and occasionally with organics. These basins have been operated to control water flow inputs according to the capacity of the pumping outlet systems before their discharge to a submarine outfall. A mass balance was performed with historical updated data to assess water availability from the basins based on the daily volume variation and flow rate of inorganic effluent from 2001 to 2007. The study identified the possibility of recovering about 1140 m3/h of the overall 5400 m3/h consumed by the Industrial Complex at the moment. Organizational changes in the present effluent disposal and stormwater harvest systems will be required in order to maximize water recovery for industrial use. 相似文献
874.
Richard N. C. Milner Michael D. Jennions Patricia R. Y. Backwell 《Behavioral ecology and sociobiology》2011,65(7):1419-1424
Non-independent mate selection occurs when the choice behavior of a female is altered by the interactions between other females
and males. In the fiddler crab Uca mjoebergi, males court mate-searching females by waving their one greatly enlarged claw. When a female approaches a male, he initiates
high-intensity waving. We conducted one natural mate choice experiment and two mate choice experiments using custom-built
robotic crabs. We show that the decision of one female to approach a group of males increases the probability that another
female will approach and visit a male from the same group. We suggest that this behavior is best explained by the ‘stimulus
enhancement’ hypothesis, where the presence of a female near a group of males makes them more likely to be detected by other
females due to an increase in male display rate. 相似文献
875.
Assessing landscape structure and pattern fragmentation in semiarid ecosystems using patch-size distributions 总被引:4,自引:0,他引:4
Spatial vegetation patterns are recognized as sources of valuable information that can be used to infer the state and functionality of semiarid ecosystems, particularly in the context of both climate and land use change. Recent studies have suggested that the patch-size distribution of vegetation in drylands can be described using power-law metrics, and that these scale-free distributions deviate from power-law linearity with characteristic scale lengths under the effects of increasing aridity or human disturbance, providing an early sign of desertification. These findings have been questioned by several modeling approaches, which have identified the presence of characteristic scale lengths on the patch-size distribution of semiarid periodic landscapes. We analyze the relationship between fragmentation of vegetation patterns and their patch-size distributions in semiarid landscapes showing different degree of periodicity (i.e., banding). Our assessment is based on the study of vegetation patterns derived from remote sensing in a series of semiarid Australian Mulga shrublands subjected to different disturbance levels. We use the patch-size probability density and cumulative probability distribution functions from both nondirectional and downslope analyses of the vegetation patterns. Our results indicate that the shape of the patch-size distribution of vegetation changes with the methodology of analysis applied and specific landscape traits, breaking the universal applicability of the power-law metrics. Characteristic scale lengths are detected in (quasi) periodic banded ecosystems when the methodology of analysis accounts for critical landscape anisotropies, using downslope transects in the direction of flow paths. In addition, a common signal of fragmentation is observed: the largest vegetation patches become increasingly less abundant under the effects of disturbance. This effect also explains deviations from power-law behavior in disturbed vegetation which originally showed scale-free patterns. Overall, our results emphasize the complexity of structure assessment in dryland ecosystems, while recognizing the usefulness of the patch-size distribution of vegetation for monitoring semiarid ecosystems, especially through the cumulative probability distributions, which showed high sensitivity to fragmentation of the vegetation patterns. We suggest that preserving large vegetation patches is a critical task for the maintenance of the ecosystem structure and functionality. 相似文献
876.
Introduction
The current study explored the association between the business cycle and the incidence of workplace injuries to identify cyclically sensitive industries and the relative contribution of physical capital and labor utilization within industries.Method
Bureau of Labor Statistics nonfatal injury rates from 1976 through 2007 were examined across five industry sectors with respect to several macroeconomic indicators. Within industries, injury associations with utilization of labor and physical capital over time were tested using time series regression methods.Results
Pro-cyclical associations between business cycle indicators and injury incidence were observed in mining, construction, and manufacturing but not in agriculture or trade. Physical capital utilization was the highest potential contributor to injuries in mining while labor utilization was the highest potential contributor in construction. In manufacturing each effect had a similar association with injuries.Conclusion
The incidence of workplace injury is associated with the business cycle. However, the degree of association and the mechanisms through with the business cycle affects the incidence of workplace injuries was not the same across industries.Impact on Industry
The results suggest that firms in the construction, manufacturing, and mining industries should take additional precautionary safety measures during cyclical upturns. Potential differences among industries in the mechanisms through which the business cycle affects injury incidence suggest different protective strategies for those industries. For example, in construction, additional efforts might be undertaken to ensure workers are adequately trained and not excessively fatigued, while safety procedures continue to be followed even during boom times. 相似文献877.
878.
879.
Devesa-Rey R Díaz-Fierros F Barral MT 《Environmental monitoring and assessment》2011,179(1-4):371-388
The metals distribution in the bed sediments of the Anllóns River was studied, with special emphasis on the evaluation of the metal distribution as a function of the granulometric fraction chosen for the analysis. Statistical significant differences between the distribution of K, Ca, Cr, Mn, As, Rb, Sr and Nb in the bulk (<2 mm) and fine fraction (<63 μm) were not found. Fe, Ni, Cu, Ga, Zr, Zn and Pb commonly appear in higher concentrations in the fine fraction, whereas Ti appears in higher concentrations in the bulk fraction. In general, it was observed that contamination phenomena tend to equalise the concentrations of both fractions, and this was mainly explained as the result of two processes. First, the formation of coatings over sands and, second, the formation of large aggregates (pseudo-sands) at sites located over basic rocks, whose chemical behaviour is closer to that of clays and could be responsible for significant adsorption processes. Normalisation techniques to evaluate contamination were applied by testing Nb, Sr, Rb or Ga as normaliser elements and by using crustal or shale average values for background concentrations. The most satisfactory result was obtained when using shale average values and Ga as the normaliser element. Arsenic was identified as the main contaminant of the basin, exceeding in all cases the low-effect reference values proposed by sediment quality guidelines and in two cases the medium-effect reference values. These sites were identified by multivariate techniques, which allow differentiating site 10 as affected by anthropogenic inputs related to past mining activities. 相似文献
880.
Nuria Castell Enrique Mantilla Ariel F. Stein Rosa Salvador Millán Millán 《Environmental Modeling and Assessment》2011,16(6):565-576
During the central months of the year, southwestern Spain is under strong insolation and weak synoptic forcing, promoting
the development of sea breezes and mountain-induced winds and creating recirculations of pollutants. The complex topography
of the Southwestern Iberia Peninsula induces the formation of vertical layers, into which the pollutants are injected and
subjected to long-distance transport and compensatory subsidence. The characteristics of these highly complex flows have important
effects on the pollutant dispersion. Air pollution studies in very complex terrains require high-resolution modelling for
resolving the flow dynamics. This paper shows the results obtained from using the MM5-CAMx multiscale-nested air quality model
to relate the sensitivity regimes for ozone, nitrogen oxides and volatile organic compounds in an area of high geographical
complexity. The article assesses the impact on the hourly and eight-hourly maximum daily ozone concentrations of four reduction
strategies during two ozone pollution episodes. This analysis of the ozone response has led to a preliminary evaluation of
the effectiveness of the most common control strategies: traffic, industry, mixed traffic and industry, and closure of some
of the largest industries (oil and petrochemical refineries). Photochemical indicators show that ozone chemistry in southwestern
Spain is strongly sensitive to NO
x
. However, volatile organic compound-sensitive points are found in areas with anthropogenic influence (highways, cities and
industrial parks). Our results indicate that reductions in road traffic lead to ozone reductions over large areas, whereas
reductions in industrial emissions, despite sometimes showing greater decreases in the maximum hourly and eight-hourly ground-level
ozone levels, lead to ozone reductions in a local area only. In the control study case, with the oil refinery and the petrochemical
plants closed, decreases in ozone hourly concentrations are up to 40% higher than in the other emission control scenarios
studied. This analysis provides an assessment of the effectiveness of different policies for controlling precursor emissions
by comparing the modelled results for different scenarios. 相似文献