全文获取类型
收费全文 | 182篇 |
免费 | 7篇 |
国内免费 | 2篇 |
专业分类
安全科学 | 11篇 |
废物处理 | 6篇 |
环保管理 | 56篇 |
综合类 | 13篇 |
基础理论 | 60篇 |
污染及防治 | 37篇 |
评价与监测 | 5篇 |
社会与环境 | 3篇 |
出版年
2023年 | 3篇 |
2022年 | 1篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 6篇 |
2017年 | 1篇 |
2016年 | 7篇 |
2015年 | 3篇 |
2014年 | 5篇 |
2013年 | 17篇 |
2012年 | 6篇 |
2011年 | 7篇 |
2010年 | 6篇 |
2009年 | 4篇 |
2008年 | 11篇 |
2007年 | 7篇 |
2006年 | 9篇 |
2005年 | 10篇 |
2004年 | 9篇 |
2003年 | 6篇 |
2002年 | 11篇 |
2001年 | 4篇 |
2000年 | 7篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1987年 | 6篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1967年 | 2篇 |
排序方式: 共有191条查询结果,搜索用时 15 毫秒
71.
72.
73.
Shanley JB Alisa Mast M Campbell DH Aiken GR Krabbenhoft DP Hunt RJ Walker JF Schuster PF Chalmers A Aulenbach BT Peters NE Marvin-DiPasquale M Clow DW Shafer MM 《Environmental pollution (Barking, Essex : 1987)》2008,154(1):143-154
The small watershed approach is well-suited but underutilized in mercury research. We applied the small watershed approach to investigate total mercury (THg) and methylmercury (MeHg) dynamics in streamwater at the five diverse forested headwater catchments of the US Geological Survey Water, Energy, and Biogeochemical Budgets (WEBB) program. At all sites, baseflow THg was generally less than 1ng L(-1) and MeHg was less than 0.2ng L(-1). THg and MeHg concentrations increased with streamflow, so export was primarily episodic. At three sites, THg and MeHg concentration and export were dominated by the particulate fraction in association with POC at high flows, with maximum THg (MeHg) concentrations of 94 (2.56)ng L(-1) at Sleepers River, Vermont; 112 (0.75)ng L(-1) at Rio Icacos, Puerto Rico; and 55 (0.80)ng L(-1) at Panola Mt., Georgia. Filtered (<0.7microm) THg increased more modestly with flow in association with the hydrophobic acid fraction (HPOA) of DOC, with maximum filtered THg concentrations near 5ng L(-1) at both Sleepers and Icacos. At Andrews Creek, Colorado, THg export was also episodic but was dominated by filtered THg, as POC concentrations were low. MeHg typically tracked THg so that each site had a fairly constant MeHg/THg ratio, which ranged from near zero at Andrews to 15% at the low-relief, groundwater-dominated Allequash Creek, Wisconsin. Allequash was the only site with filtered MeHg consistently above detection, and the filtered fraction dominated both THg and MeHg. Relative to inputs in wet deposition, watershed retention of THg (minus any subsequent volatilization) was 96.6% at Allequash, 60% at Sleepers, and 83% at Andrews. Icacos had a net export of THg, possibly due to historic gold mining or frequent disturbance from landslides. Quantification and interpretation of Hg dynamics was facilitated by the small watershed approach with emphasis on event sampling. 相似文献
74.
Donna M. Randall 《组织行为杂志》1990,11(5):361-378
Extensive research on the consequences of organizational commitment (OC) has been conducted over the past decade. The purpose of this paper is to summarize empirical evidence about the relationship between OC and work outcomes and to examine the effect of methodological decisions on the OC–work outcome relationship. A meta-analysis of 35 studies of the OC–work outcome linkage reveals that the overall empirical relationship between OC and outcome variables is generally weak, but positive. While subgroup analyses reveal that conceptualization, research design, sampling, operationalization and observation technique decisions have a definite impact on the OC–work outcome correlation, the relationship remains essentially weak. Multiple regression analysis reveals that the type of work outcome and methodological decisions explain only 19 per cent of the variance in the OC–work outcome relationship, with conceptualization decisions having the largest impact. 相似文献
75.
76.
Terrence McCue Rahul Naik Mauricio Zepeda Yan-Hua Liu Igor Vassiliev Andrew Amis Randall 《Water environment research》2004,76(1):23-28
A preliminary bench-scale study of parallel University of Cape Town (UCT) biological nutrient removal systems showed improvement in anoxic denitrification rates resulting from prefermentation of a septic (i.e., high volatile fatty acid [VFA] content), phosphorus-limited (i.e., total chemical oxygen demand/total phosphorus [TP] ratio < 40:1) wastewater. Net phosphorus removals due to enhanced biological phosphorus removal (EBPR) were only improved marginally by prefermentation in spite of significant increases in anaerobic phosphorus release, polyhydroxyalkanoate formation, and higher anoxic and aerobic uptakes. This probably was due to the high VFA/TP ratio in the raw influent relative to the VFA requirements for EBPR because enough VFAs were already present for phosphorus removal prior to prefermentation. An additional assessment of prefermentation using parallel UCT systems with step feed of 50% of the influent to the anoxic zone was completed. This second phase quantified the effect of prefermentation in a step-feed scenario, which prioritized prefermentation use to enhance denitrification rather than EBPR. While specific denitrification rates in the anoxic zone were significantly improved by prefermentation, high denitrification in the clarifiers and aerobic zones (simultaneous denitrification) made definitive conclusions concerning the potential improvements in total system nitrogen removal questionable. The prefermented system always showed superior values of the zone settling velocity and sludge volume index and the improvement became increasingly statistically significant when the prefermenter was performing well. 相似文献
77.
Dominance relationships in solitary species may be an important factor in the maintenance of long-term, stable relationships
among territorial neighbors. We examined the mediation of intraspecific interactions in a solitary, territorial kangaroo rat,
Dipodomys heermanni, and tested whether unfamiliar kangaroo rats establish a dominance hierarchy and then decrease aggression and increase communication
(via footdrumming and sandbathing) after initial interactions and the establishment of a social structure. Results revealed
that both dominance hierarchies and familiarization with particular individuals are likely to mediate social interactions.
After only one pairing per dyad, an almost linear dominance hierarchy emerged, which became perfectly linear after a 90-min
familiarization period. During the course of subsequent interactions between dyad partners, fighting decreased and non-agonistic
communication increased. Dominant kangaroo rats sandbathed at higher rates than subordinates, possibly to deposit scent to
advertise competitive ability, whereas subordinate kangaroo rats footdrummed from inside the burrow, which seemed to indicate
an unwillingness to interact. We suggest the kangaroo rats use a conditional strategy when deciding to fight (be dominant)
or withdraw (be subordinate) by employing different modes to communicate status and minimize the potential risk of injury
during unnecessarily prolonged fights. 相似文献
78.
Summary Mongolian gerbils were observed over seasonal changes in day length and temperature in an outdoor enclosure containing an extensive burrow system. Animals could choose between the stable environment of their burrow and the daily and seasonal flunctuations aboveground. Surgically implanted radio transmitters provided body temperature and location of animals.Gerbils avoided temperature extremes by emerging from their burrow when ambient temperature fell below burrow temperature in hot weather and rose above burrow temperature in cold weather. They delayed emergence in the winter until several hours after sunrise and emerged before or after sunset in summer (Fig. 1).Circadian changes in core-body temperature corresponded to increases and decreases in behavioral activity. Emergence from the burrow was predictable by an increase in body temperature, as a warm-up period preceded emergence (Fig. 3).We conclude that gerbils, when subjected to extreme temperatures in the wild, probably time their activity to correspond to preferred ambient temperatures and thus shift from diurnal activity in the winter to nocrurnal activity in the summer (Fig. 2). This desert rodent's exceptional thermoregulatory capacity adapts it for synchronizing its daily activity to temperature. 相似文献
79.
R. E. Randall 《Journal of Coastal Conservation》2004,10(1):159-168
Coastal vegetated shingle is a rare and declining resource worldwide but is found extensively around the UK coastline. Shingle
sediments b-axes range between 2 mm and 200 mm and occur as fringing beaches, bars, spits, barrier islands and forelands.
Sediment patterns are dependent upon accretion or erosion. With sea-level rise, shingle features tend to move inland. Larger
features may support reservoirs of fresh water but risk becoming saline with sea-level rise. Ranker soils may develop but
are naturally fragile. Vegetated shingle communities are dependent upon substrate stability, moisture and nutrient availability.
Only specialized and some ruderal plants can persist in patterns dependent upon geomorphic history. Coastal defence, agriculture,
public access and control of alien species are important factors in habitat management. Because of its dynamic and unusual
nature coastal vegetated shingle is an important habitat for environmental education. 相似文献
80.
In this study, the combined effects of temperature and solids retention time (SRT) on enhanced biological phosphorus removal (EBPR) performance and the mechanism of EBPR washout were investigated. Two pilot-scale University of Cape Town (South Africa) systems fed with synthetic wastewater were operated at 5 and 10 degrees C. The results showed that the phosphorus removal performance was optimum at total SRT ranges of 16 to 24 days and 12 to 17 days for 5 and 10 degrees C, respectively, and steady-state phosphorus removal was greater at the lower temperature. Higher SRT values of up to 32 days at 5 degrees C and 25 days at 10 degrees C slightly reduced EBPR performance as a result of increased extent of endogenous respiration, which consumed internally stored glycogen, leaving less reducing power for poly-hydroxy alkanoate (PHA) formation in anaerobic stages. The phosphorus-accumulating organism (PAO) washout SRTs of the systems were determined as 3.5 days at 5 degrees C and 1.8 days at 10 degrees C, considerably less than the washout SRTs of nitrifiers. Polyphosphorus, the main energy reserve of the EBPR bacterial consortium, was not completely depleted, even at washout points. The inability of EBPR biomass to use glycogen to generate reducing power for PHA formation was the major reason for washout. The results not only suggest that glycogen mechanism is the most rate-limiting step in EBPR systems, but also that it is an integral part of EBPR biochemistry, as proposed originally by Mino et al. (1987), and later others (Pereira et al., 1996, Erdal et al., 2002; Erdal, Z. K., 2002). The aerobic washout SRT values (2.1 and 1.2 days for 5 and 10 degrees C, respectively) of this study did not fit the linear line for PAO washout developed by Mamais and Jenkins (1992). Perhaps this was because the feeds used during this study were chemical-oxygen-demand-limited (acetate-based synthetic feed), whereas the feeds used for their study were phosphorus-limited (external acetate added to domestic wastewater), resulting in different ratios of PAOs and nonPAOs in the biomass. 相似文献