首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   115篇
  免费   1篇
  国内免费   2篇
安全科学   4篇
废物处理   7篇
环保管理   49篇
综合类   11篇
基础理论   17篇
污染及防治   15篇
评价与监测   9篇
社会与环境   1篇
灾害及防治   5篇
  2021年   1篇
  2020年   1篇
  2019年   1篇
  2018年   4篇
  2017年   3篇
  2016年   4篇
  2015年   4篇
  2014年   1篇
  2013年   16篇
  2012年   3篇
  2011年   6篇
  2010年   5篇
  2009年   5篇
  2008年   2篇
  2007年   5篇
  2006年   3篇
  2005年   7篇
  2004年   10篇
  2003年   3篇
  2002年   4篇
  2001年   3篇
  2000年   2篇
  1999年   2篇
  1998年   3篇
  1997年   4篇
  1996年   5篇
  1994年   2篇
  1993年   2篇
  1991年   1篇
  1989年   1篇
  1987年   1篇
  1983年   1篇
  1979年   1篇
  1978年   1篇
  1969年   1篇
排序方式: 共有118条查询结果,搜索用时 15 毫秒
91.
92.
Abstract

The aim of the research was to evaluate the effect of consumption of selenium-enriched pork on selected health indicators of probands. The intake of feed mixture with increased organic selenium at the dose of 0.3?mg.kg?1 probably increases selenium concentration in MSM (musculus semimembranosus). In the pork enriched with organic selenium, the concentration was higher by 1.045?±?0.10?mg.kg?1 compared with the control group 0.701?±?0.05?mg.kg?1 at significance P?<?0.001. Sixteen participants in the experiment were represented by 8 men at the average age of 41.5?±?11.9?years and 8 women at the average age of 41.4?±?7.9?years. All the probands consumed meat enriched with selenium three times a week during one month. By consumption of the enriched pork, there was an increase of the selenium concentration in blood serum of probands traced with selenium increase from 73.19?±?15.68?μg.L?1 to 73.73?±?15.13?μg.L?1 (P?>?0.05). From the results we can see that consumption of enriched pork with selenium was significantly manifested in lowering of total cholesterol levels, which was associated with LDL cholesterol lowering (P?<?0.05). Differences among the HDL cholesterol and triglycerides samples were not significant.  相似文献   
93.
Synchrotron-source X-ray computerized microtomography (CMT) is evaluated as a method to visualize transport processes. We conclude that CMT is adequate for visualization of transport experiments if the right conditions exist. Namely, 1) not much more than one-order-of-magnitude range in concentration data is needed for the study, 2) the pore space in the samples are greater than approximately 2--50 mum, depending on the sample size and system setup; 3) the sample is fine-grained enough so that a representative elemental volume (REV) can be contained by a 2--10 mm diameter sample, and 4) the transport process is slow enough that significant changes do not occur within the 25--50 min (and possibly less in the future) needed to collect data for one three-dimensional image. Absorption edge difference imaging (AEDI) in association with CMT is introduced as a method to enhance pore-space visualization. We successfully imaged the pore space in a low-porosity granodiorite, diorite and fine-grained granite cores and a higher-porosity soil aggregate sample. We found that the pore space important to transport in the core samples was smaller than what we were able to visualize with CMT. We also made rudimentary associations of minerals with pore-space location.  相似文献   
94.
We know that animals are harmed in plant production. Unfortunately, though, we know very little about the scale of the problem. This matters for two reasons. First, we can’t decide how many resources to devote to the problem without a better sense of its scope. Second, this information shortage throws a wrench in arguments for veganism, since it’s always possible that a diet that contains animal products is complicit in fewer deaths than a diet that avoids them. In this paper, then, we have two aims: first, we want to collect and analyze all the available information about animal death associated with plant agriculture; second, we try to show just how difficult it’s to come up with a plausible estimate of how many animals are killed by plant agriculture, and not just because of a lack of empirical information. Additionally, we show that there are significant philosophical questions associated with interpreting the available data—questions such that different answers generate dramatically different estimates of the scope of the problem. Finally, we document current trends in plant agriculture that cause little or no collateral harm to animals, trends which suggest that field animal deaths are a historically contingent problem that in future may be reduced or eliminated altogether.  相似文献   
95.
Entomophagy—eating insects—is getting a lot of attention these days. However, strict vegans are often uncomfortable with entomophagy based on some version of the precautionary principle: if you aren’t sure that a being isn’t sentient, then you should treat it as though it is. But not only do precautionary principle-based arguments against entomophagy fail, they seem to support the opposite conclusion: strict vegans ought to eat bugs.  相似文献   
96.
Although it is much safer and more fuel-efficient to transport children to school in buses than in private vehicles, school buses in the United States still consume 822 million gal of diesel fuel annually, and school transportation costs can account for a significant portion of resource-constrained school district budgets. Additionally, children in diesel-powered school buses may be exposed to higher levels of particulates and other pollutants than children in cars. One solution to emission and fuel concerns is use of hybrid-electric school buses, which have the potential to reduce emissions and overall lifecycle costs compared with conventional diesel buses. Hybrid-electric technologies are available in the passenger vehicle market as well as the transit bus market and have a track record indicating fuel economy and emissions benefits. This paper summarizes the results of an in-use fuel economy evaluation for two plug-in hybrid school buses deployed in two different school districts in Iowa. Each school district selected a control bus with a route similar to that of the hybrid bus. Odometer readings, fuel consumption, and maintenance needs were recorded for each bus. The buses were deployed in 2008 and data were collected through May 2010. Fuel consumption was calculated for each school district. In Nevada, IA, the overall average fuel economy was 8.23 mpg for the hybrid and 6.35 mpg for the control bus. In Sigourney, IA, the overall average fuel economy was 8.94 mpg for the hybrid and 6.42 mpg for the control bus. The fuel consumption data were compared for the hybrid and control buses using a Wilcoxon signed rank test. Results indicate that fuel economy for the Nevada hybrid bus was 29.6% better than for the Nevada control bus, and fuel economy for the Sigourney hybrid bus was 39.2% higher than for the Sigourney control bus. Both differences were statistically significant.  相似文献   
97.
Positive static allometry is a scaling relationship where the relative size of traits covaries with adult body size. Traditionally, positive allometry is thought to result from either altered physiological requirements at larger body size or from strongly condition-dependent allocation under sexual selection. Yet, there are no theoretical reasons why positive allometry cannot evolve in fitness-related traits that are solely under the influence of natural selection. We investigated scaling and sexual dimorphism of a naturally selected trait, pectoral fin size, in comparison to a trait important in male–male combat, head width in natural populations of a fish, the desert goby Chlamydogobius eremius. Male desert gobies provide uniparental care and use their pectoral fins to fan the brood (often under hypoxic conditions); hence, larger fins are expected to be more efficient. Male pectoral fins do not appear to fulfil a signalling function in this species. We found that, for both pectoral fin size and head width, males exhibited positive allometric slopes and greater relative trait size (allometric elevation) than females. However, for head width, females also showed positive allometry, albeit to a lesser degree than males. Because fin locomotory function typically does not result in positive allometry, our findings indicate that other naturally selected uses, such as paternal care, can exaggerate trait scaling relationships.  相似文献   
98.
It has now been well over 20 years since the North Sea Piper Alpha disaster in 1988. There have been many lessons learned; some documented others just etched in memory. The event chronicled many significant changes in the offshore industry. The emanating point for most sweeping changes has been the Cullen Report and the UK North Sea industry. This paper reviews some of the critical lessons and identifies many ‘secondary’ finer points that constitute important learnings. The paper looks at major changes instigated by step changes in safety criticality. It is argued that the ‘second tier’ modes of failure such as corrosion, materials degradation, environmental cracking, erosion, plant ergonomics, etc. need to be better examined. These mechanisms are dangerous threats to the integrity of deep subsea assets, and it is noted that such root causes of failure as witnessed or predicted have yet to be fully appraised. The authors’ use wide experiences and case histories to highlight such concerns, offering rational fit-for-purpose solutions. The industry disconnections between, urgency to build, knowledge transfer, and management of change, are refocused. Powerful advances in risk-based mechanical, process, materials, and corrosion engineering are emphasized and the use of key performance indicators (KPIs) are reasoned for best life-cycle integrity. To keep up with the pace of growth in the deepwater sector, methods of concurrent and inherently safe design have evolved in a world where the practicalities and costs of modification, repair and retrofit are extremely difficult. Hence getting it right at the outset is paramount. Thus the drive for purposeful investment, at design is more justifiable, than the traditional practice of postponing costs (and problems) to operations. In this way the ominous ‘gray’ zone between the two cost centers is better bridged for reasons of safety and commercial advantage.  相似文献   
99.
Mate choice is not just a female preoccupation. Under some circumstances, males may also be choosy. However, studies of male mate choice have generally been confined to situations where males can make direct comparisons between potential partners. In contrast, sequential male mate choice has largely been overlooked despite its biologically importance, especially if current investment in mate attraction diminishes a males future mating opportunities. Using the Pacific blue-eye fish Pseudomugil signifer, we show that males are capable of exercising sequential mate choice. When presented sequentially with large and small females, males spent more effort courting the former. However, males did not appear to modify the time spent courting a given female based on the size of the female encountered previously. We suggest that greater attention to the sequential choice problem in males may help illuminate similarities and differences between the sexes when it comes to mating decisions.Communicated by T. Czeschlik  相似文献   
100.
At the end of the 20th century, business finds itself in a period of transformation and a new emphasis on environmentally responsible practices. Leading-edge companies are now integrating environmental concerns into everyday business activities. Competitive issues, which led to the formation of just-in-time production processes, are now forcing companies to better understand their effects on the environment. Business leaders must now look at environmental issues as opportunities, not burdens. With innovative use of “industrial ecology,” companies can set the stage for long-term growth into the next century. “Business men go down with their businesses because they like the old way so well they cannot bring themselves to change.” Henry Ford.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号