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   141篇
  免费   2篇
安全科学   7篇
废物处理   12篇
环保管理   8篇
综合类   22篇
基础理论   41篇
污染及防治   35篇
评价与监测   12篇
社会与环境   6篇
  2023年   3篇
  2022年   5篇
  2021年   7篇
  2020年   2篇
  2019年   4篇
  2018年   6篇
  2017年   4篇
  2016年   13篇
  2015年   2篇
  2014年   7篇
  2013年   13篇
  2012年   13篇
  2011年   9篇
  2010年   4篇
  2009年   4篇
  2008年   9篇
  2007年   11篇
  2006年   6篇
  2005年   7篇
  2004年   4篇
  2003年   2篇
  2002年   4篇
  1991年   1篇
  1990年   1篇
  1984年   1篇
  1972年   1篇
排序方式: 共有143条查询结果,搜索用时 15 毫秒
81.
Carotenoid-based ornaments (many yellow–orange–red colourations) may signal the genetic or parental quality of the bearer. Thus, their expression could influence the amount of resources/energy that the mate will invest in the production of offspring, thereby optimising its reproductive fitness. The differential allocation hypothesis (DAH) predicts that females mated with more attractive males should lay more and better eggs. This has been explored only in few bird species with carotenoid-based traits. We tested this hypothesis in the red-legged partridge (Alectoris rufa), a gallinacean with very variable laying capacity. Both sexes display carotenoid-based ornamentation that gradually fades throughout the laying period. Here, the redness of beak and eye rings of captive males was intensified after mating by means of paint. The proportion of females that laid eggs did not differ between treatments. Amongst laying females, those mated with colour-enhanced males (experimental females) tended to lay earlier and produced significantly more eggs than controls, but of similar quality (egg mass and composition). We additionally investigated whether male attractiveness influenced egg components depending on the clutch size and laying sequence. The testosterone level in eggs from experimental females was positively related to the laying order, whereas control eggs did not show any trend. Our results provided mixed support for the DAH, but nevertheless revealed that female red-legged partridges may adjust their breeding investment according to male carotenoid-based ornamentation.  相似文献   
82.
Three laboratories participated in a PCDD and PCDF sampling experiment on the stack of a municipal waste incinerator and six laboratories examined a fly ash sample for PCDDS and PCDFS in order to assess analytical precision.

The flue gas sampling results are in agreement for the three laboratories and show that the PCDDS and PCDFS are predominantly in the gas phase, whereas emitted particulate account for 20% of the total PCDD/PCDF concentration.  相似文献   

83.
We discuss a problem in the safety assessment of automatic control and protection systems. There is an increasing dependence on software for performing safety-critical functions, like the safety shut-down of dangerous plants. Software brings increased risk of design defects and thus systematic failures; redundancy with diversity between redundant channels is a possible defence. While diversity techniques can improve the dependability of software-based systems, they do not alleviate the difficulties of assessing whether such a system is safe enough for operation. We study this problem for a simple safety protection system consisting of two diverse channels performing the same function. The problem is evaluating its probability of failure in demand. Assuming failure independence between dangerous failures of the channels is unrealistic. One can instead use evidence from the observation of the whole system's behaviour under realistic test conditions. Standard inference procedures can then estimate system reliability, but they take no advantage of a system's fault-tolerant structure. We show how to extend these techniques to take account of fault tolerance by a conceptually straightforward application of Bayesian inference. Unfortunately, the method is computationally complex and requires the conceptually difficult step of specifying ‘prior’ distributions for the parameters of interest. This paper presents the correct inference procedure, exemplifies possible pitfalls in its application and clarifies some non-intuitive issues about reliability assessment for fault-tolerant software.  相似文献   
84.
85.
The underlying principles of water’s equation of state (ES) and its associated pressure–volume–temperature (PVT) relationship, are employed for the purpose of producing “ultra-high” pressure within the closed volume of a thick-walled metal tube, resulting in a new and innovative hydroforming process. The process, called “Closed-Volume Thermally Activated” (CVTA) Tube Hydroforming, involves conducting a high level of heat through the walls of a thick-walled, metallic, water-containing closed tube. Experimental validation of the concept is presented, and potential applications are discussed. This work represents a break-through in manufacturing technology, which, when further developed, is expected to enable manufacturers to expand significantly their manufacturing capability.  相似文献   
86.
Environmental and Ecological Statistics - In the inverse distance weighting interpolation the interpolated, value is a weighted mean of the sampled values, with weights decreasing with the...  相似文献   
87.
To understand the scope and scale of the loss of biodiversity, tools are required that can be applied in a standardized manner to all species globally, spanning realms from land to the open ocean. We used data from the International Union for the Conservation of Nature Red List to provide a synthesis of the conservation status and extinction risk of cetaceans. One in 4 cetacean species (26% of 92 species) was threatened with extinction (i.e., critically endangered, endangered, or vulnerable) and 11% were near threatened. Ten percent of cetacean species were data deficient, and we predicted that 2–3 of these species may also be threatened. The proportion of threatened cetaceans has increased: 15% in 1991, 19% in 2008, and 26% in 2021. The assessed conservation status of 20% of species has worsened from 2008 to 2021, and only 3 moved into categories of lesser threat. Cetacean species with small geographic ranges were more likely to be listed as threatened than those with large ranges, and those that occur in freshwater (100% of species) and coastal (60% of species) habitats were under the greatest threat. Analysis of odontocete species distributions revealed a global hotspot of threatened small cetaceans in Southeast Asia, in an area encompassing the Coral Triangle and extending through nearshore waters of the Bay of Bengal, northern Australia, and Papua New Guinea and into the coastal waters of China. Improved management of fisheries to limit overfishing and reduce bycatch is urgently needed to avoid extinctions or further declines, especially in coastal areas of Asia, Africa, and South America.  相似文献   
88.
Coal ash from power stations has long been used successfully in the cement industry as binders in several Portland formulations. This is not the case for municipal solid waste (MSW) ash as chloride concentrations, ranging from 10 to 200 g kg(-1) dry weight in the bottom and fly ash, respectively, exceed the maximum allowable concentration in most cement mixtures. To reduce chloride content in MSW bottom ash, a laboratory investigation was carried out based on the exhaustive washing in tap water. The influence of operative parameters such as temperature, granulometric properties and solid/liquid ratio of extraction was evaluated. In addition to optimization of the mentioned operative parameters for full-scale application, the paper gives preliminary indications on mechanistic aspects of the washing operation.  相似文献   
89.
Gorgonian corals are long-lived, slow-growing marine species dominating Mediterranean rocky bottoms. Endowed with complex morphologies they give a structure to the whole community, moreover, being efficient suspension feeders, they play a key role in plankton-benthos energy flow and CO2CO2 storage. Thus, the structure and the development of benthic, hard bottom communities are linked to gorgonian survival. The red coral Corallium rubrum (L. 1758) is a precious gorgonian endemic to the Mediterranean Sea. Harvested and traded world-wide since ancient times red coral is a clear example of overexploited marine resource. This species is structured into self-seeding, genetically differentiated populations, some of which, living in the shallower part of the species bathymetric distribution, was recently affected by anomalous mortality events linked to global climate change. The co-occurrence of overharvesting and mass mortality could dramatically affect such populations. Demographic population models, widely applied by conservation biologists to check population viability and to project population trends over time are fundamental to foster survival of such populations matching harvesting to population growth rates. Therefore we set out a dynamic model of a genetically differentiated red coral population living in shallow waters. This population is characterised by small/young, crowded colonies and high recruitment rate. On the basis of the size–age structure determined for this population, a static life-history table, in which survival and reproduction coefficients of the different size–age classes were reported, has been set out. Demographic data were included in a non-linear, discrete, age-structured dynamic model, based on a Leslie-Lewis transition matrix. Our field data indicate that the recruits-to-larvae ratio is actually density-dependent. Such dependence, positive for low and negative for high density values, was included into the model and the effect of colonies of different size–age classes on recruits-to-larvae ratio was considered to be proportional to the number of polyps they have. We applied such model to simulate the trends of the studied population under different increases of survival and life-span. As some populations of gorgonians actually show the dominance of sparse, big/old colonies and low recruitment rate, while others are characterised by crowded, small/young colonies and high recruitment rate, we simulated the shift from the former to the latter structure increasing survival and life-span. Our results suggest that a dramatic mortality increase of bigger–older colonies (due, in the case of red coral to overfishing) could have determined the population structure we found.  相似文献   
90.
The aim of this work was to study the distribution of imidacloprid in soil and its translocation to roots and aerial parts of maize plant. The main objective was to assess imidacloprid residues in field environment, in order to provide data on honeybees exposure level to such an active substance. Imidacloprid has been detected and quantified by Triple Quadrupole HPLC-MS-MS. Pesticide persistence in the soil and its residues in pollen and in maize plants have been evaluated during the growing of maize plants developed from seeds dressed with Gaucho 350 FS (imidacloprid: 1.0 mg/seed). The sowing has been performed by means of a pneumatic precision drill. Samples have been collected at 30, 45, 60, 80, 130 days after the sowing, as pollen samples have been collected at the tasseling. Imidacloprid presence in aerial part of maize plant declined to 2-3 μg/kg 80 days after the sowing, while concentration in kernel at harvest was <1 μg/kg. Maize pollen represents an important part of protein supply of beehives, and it is of critical importance to bee foraging. The values detected (imidacloprid residues <1 μg/kg) showed that maize pollen source should not be relevant for acute toxicity impact on honey bees.  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