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   278篇
  免费   2篇
  国内免费   4篇
安全科学   4篇
废物处理   6篇
环保管理   16篇
综合类   129篇
基础理论   70篇
污染及防治   35篇
评价与监测   10篇
社会与环境   13篇
灾害及防治   1篇
  2017年   6篇
  2015年   8篇
  2014年   2篇
  2013年   8篇
  2012年   13篇
  2011年   13篇
  2010年   11篇
  2009年   8篇
  2008年   8篇
  2007年   14篇
  2006年   5篇
  2005年   6篇
  2004年   9篇
  2003年   6篇
  2002年   11篇
  2001年   5篇
  2000年   5篇
  1999年   5篇
  1998年   6篇
  1997年   4篇
  1996年   4篇
  1995年   3篇
  1994年   4篇
  1992年   4篇
  1990年   2篇
  1989年   2篇
  1984年   2篇
  1982年   3篇
  1981年   4篇
  1980年   2篇
  1978年   2篇
  1977年   3篇
  1970年   3篇
  1967年   5篇
  1966年   4篇
  1965年   11篇
  1964年   9篇
  1963年   10篇
  1962年   6篇
  1961年   5篇
  1960年   4篇
  1959年   2篇
  1957年   2篇
  1956年   2篇
  1954年   5篇
  1951年   2篇
  1942年   2篇
  1940年   2篇
  1939年   2篇
  1925年   2篇
排序方式: 共有284条查询结果,搜索用时 15 毫秒
191.
192.
193.
194.
195.
During recent years, the awareness of quality assurance and quality control in environmental analyses has constantly increased, especially due to the implementation of new guidelines and regulations at both the national and international level. Achieving comparable results by using certified reference materials is one of the primary concerns of the scientific community. As a result, there is a growing demand for certified reference materials to cover different matrices and pollutants. Moreover, these CRMs should be in close relationship to the determinants and target concentrations required by environmental bodies and European Directives as well. Supplementary information to this paper presents an inventory of reference materials available on the market from different suppliers against the priority pollutants listed in the Water Framework Directive. These CRMs cover matrices such as water, sediment and biota. The use of CRMs in relationship to appropriate analytical methods and relevant determinants is discussed and the need for matrix-CRMs, particularly for organic pollutants is emphasised. The use of proficiency testing schemes as an alternative for the lack of appropriate CRMs and future trends in the production of CRMs within the BCR framework are also discussed.  相似文献   
196.
A set of microcosm experiments was performed to understand the behaviour of special degraders in bioaugmentation experiments. In the experiments the following chlorobenzene degraders were used: the genetically modified Pseudomonas putida F1CC, and the two wild-type strains Pseudomonas putida GJ31 and Pseudomonas aeruginosa RHO1. These strains were used at an initial cell density of 105 cells mL–1 groundwater which had been spiked with 1,2-dichlorobenzene (1,2-DCB), 1,4-dichlorobenzene (1,4-DCB) and, as main contaminant, chlorobenzene (CB). The population dynamics and behaviour of the three special degraders within the groundwater microcosms were studied by single-strand conformation polymorphism (SSCP) analysis of 16S rDNA fragments amplified from directly extracted community DNA and fluorescent in situ hybridization (FISH) with species-specific probes. RHO1 disappeared after 4 days as detected by FISH in contrast to SSCP-detection where RHO1 could be found during the whole incubation time. Whereas GEM F1CC and wild-type strain GJ31 survived the whole incubation for 20 days. With both methods we were able to detect all strains with high specificity among the indigenous microbial community. The data sets obtained from SSCP analysis and FISH were highly correlated. Specific band intensity within the SSCPfingerprints and the cell counts determined by FISH gave a quantitative overview about the introduced strains.  相似文献   
197.
Summary The diet selected by three-spined sticklebacks (Gasterosteus aculeatus) depends on the degree of parasitization by one or both of two parasite species (Schistocephalus solidus, Glugea anomala). Uninfested fish prefer the more profitable of two different size classes of prey (Daphinia magna). Fish parasitized by Glugea or Schistocephalus attack both prey types equally often, whereas sticklebacks infested by both parasite species prefer to attack the less profitable prey. The diet selected is optimal under the condition that parasites decrease their host's competitive ability.  相似文献   
198.
The Hypercycle     
The Science of Nature - The proposed model for a ‘realistic hypercycle’ is closely associated with the molecular organization of a primitive replication and translation apparatus....  相似文献   
199.
This article considers the growth in stockpiles of natural and enriched uranium, which have now reached such significant proportions and analyses the effect that the stockpiles might have on the market for natural uranium in the coming years. While stockpiles have not yet reached their peak in absolute terms, they have already passed it in relative terms, ie in multiples of annual demand.  相似文献   
200.
Lactation imposes substantial physiological costs on mothers and should therefore not be directed towards foreign offspring. Such allonursing, however, is common in mammal species that share roosts. Hypotheses to explain allonursing among such plural breeders include misdirected parental care, milk evacuation, brood parasitism, reciprocity, and kin selection. The necessary behavioral data, in combination with data on kinship and kin recognition, have rarely been available to distinguish among these explanations, however. In this study, we provide evidence for cooperative nursing and adoption by plural-breeding females in a nocturnal primate, the gray mouse lemur (Microcebus murinus), in which females forage solitarily during the night, but form day-time sleeping groups with one to two other females. We observed 34 resident females in an 8 ha study area in Kirindy Forest, Madagascar, over three consecutive annual breeding seasons and determined genetic relationships among all members of this population. Five sleeping groups of adult females were filmed inside their roosts during one breeding season after females gave birth. The composition of groups changed substantially across years, but they always consisted of close maternal relatives. All females within a group gave birth to one to three infants. They regularly transferred only their own offspring among roosting sites, demonstrating an ability to discriminate between their own and other’s offspring, but they regularly groomed and nursed related offspring other than their own and adopted related dependent young after their mother’s death. Kin selection may therefore be the main selective force behind cooperative breeding among these closely related females with a high mortality risk, providing each of them with family insurance.  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