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   104篇
  免费   3篇
  国内免费   3篇
安全科学   2篇
废物处理   6篇
环保管理   14篇
综合类   26篇
基础理论   15篇
污染及防治   30篇
评价与监测   11篇
社会与环境   5篇
灾害及防治   1篇
  2023年   4篇
  2022年   4篇
  2021年   6篇
  2020年   5篇
  2019年   3篇
  2018年   4篇
  2017年   10篇
  2016年   10篇
  2015年   6篇
  2014年   5篇
  2013年   8篇
  2012年   5篇
  2011年   9篇
  2010年   4篇
  2009年   4篇
  2008年   8篇
  2007年   1篇
  2006年   3篇
  2005年   2篇
  2004年   1篇
  2003年   2篇
  2002年   3篇
  1995年   2篇
  1974年   1篇
排序方式: 共有110条查询结果,搜索用时 93 毫秒
71.
We performed a study of fulvic acids extracted from fresh and aged snow, and from recent and ancient ice in Antarctica. The fresh snow samples were collected in coastal and inland sites to evaluate the influence of the distance from the sea on organic matter transport. Moreover, in a site (Melbourne Mountain) samples were collected at different heights to study the influence of altitude on transport. The obtained results showed that dissolved fulvic acid concentrations are influenced neither by distance nor by height while particulate fulvic acid concentrations are influenced by both parameters. Moreover, the results showed that fulvic acids transported for a long distance can undergo chemical modifications. Chemical modifications are better evidenced by the analysis of samples taken in trenches at different depth, which showed structural changes attributable to the loss of nitrogen-containing compounds and to an increase in aromatic character of the structures due to reduction and/or condensation processes. With ageing, the humification process proceeds with heavy carbon losses as demonstrated by results obtained from fulvic acids isolated from ice aged between twenty-five thousand and seventy thousand years.  相似文献   
72.
On consultation, percutaneous umbilical blood sampling (PUBS) was offered to women with immune thrombocytopenic purpura (ITP) to determine the mode and site of delivery prior to labour. Between January 1989 and December 1993, 41 pregnant women underwent PUBS. All women had a history of ITP, a platelet count less than 90 K, (+) antiplatelet antibody, and/or thrombocytopenia diagnosed early in pregnancy. PUBS was performed at term except in one patient with preterm labour, who underwent PUBS at 31 weeks' gestation. Patients with fetal platelet counts greater than 50 K returned to their referring physician for delivery. Records were complete in 39 pregnancies. Fetal blood was successfully obtained in 37 of 39 cases (95 per cent). Fetal platelet counts correlated with neonatal platelet counts in 36 of 37 cases (97 per cent). The interval between PUBS and delivery ranged from 0 to 31 days. Six of 37 fetuses (16 per cent) had significant fetal thrombocytopenia (<50 K). These six patients underwent Caesarean section. Vaginal delivery was recommended in all others. There were two procedure-related complications. There were no cases of intraventricular haemorrhage in any of the neonates. In conclusion, there is a high incidence of fetal thrombocytopenia in women with ITP. PUBS reliably detects fetal thrombocytopenia and is therefore useful in the perinatal planning of the mode and site of delivery.  相似文献   
73.

Laboratory water flumes are artificial troughs of moving water widely used in hydraulic studies of fluvial systems to investigate real-world problems at smaller, more manageable scales. Water flumes have also been used to understand bone transportation sorting and bone orientation found in the fossil record using actual bones. To date, these studies have not involved scaled bones. A 1/12 scale model of a 21.8-m long skeleton of Apatosaurus, a long-necked sauropod dinosaur from the Late Jurassic, was used to explore three problems at Dinosaur National Monument (USA) that cannot be explained by tradition bone flume studies: (1) why there is an abrupt bend in articulated vertebrae, (2) why articulated dorsals are inverted relative to the pelvis, and (3) how bone jams form. The flume experiments established that (1) bed friction with the wing-like transverse processes of vertebrae resists the force of the water flow, whereas those vertebrae lacking the processes are free to pivot in the flow; (2) elevation of the dorsal vertebrae by the transverse processes subjects the vertebrae to the energy of the flow stream, which causes the vertebrae to flip. Computation fluid dynamics (CFD) software shows this flip was due to differential pressure on the upstream and downstream sides. (3) The formation and growth of bone clusters or jams (analogous to log jams in rivers) occur as transported bones pile against an initial obstruction and jammed bones themselves become obstacles. These preliminary studies show that scale models can provide valuable insights into certain taphonomic problems that cannot be obtained by traditional bone flume studies.

  相似文献   
74.
Hybridisation between closely related species is frequently seen as retarding evolutionary divergence and can also promote it by creating novel phenotypes due to new genetic combinations and developmental interactions. We therefore investigated how hybridisation affects the shape of the mouse mandible, a well-known feature in evo–devo studies. Parental groups corresponded to two strains of the European mouse sub-species Mus musculus domesticus and Mus musculus musculus. Parents and hybrids were bred in controlled conditions. The mandibles of F1 hybrids are mostly intermediate between parental phenotypes as expected for a complex multigenic character. Nevertheless, a transgressive effect as well as an increased phenotypic variance characterise the hybrids. This suggests that hybridisation between the two subspecies could lead to a higher phenotypic variance due to complex interactions among the parental genomes including non-additive genetic effects. The major direction of variance is conserved, however, among hybrids and parent groups. Hybridisation may thus play a role in the production of original transgressive phenotypes occurring following pre-existing patterns of variance.  相似文献   
75.
Two media bed (gravel and Filtralite NR) were tested in a mesocosm to evaluate the removal of organic matter (as chemical oxygen demand (COD)), ammonia (NH4-N), nitrite, nitrate and solid matter (as total suspended solids (TSS)) for a synthetic wastewater (acetate-based) and a domestic wastewater. The use of Filtralite allowed average removal rates (6–16.8 g COD/(m2 day), 0.8–1.1 g NH4-N/(m2 day) and 3.1 g TSS/(m2 day)) and removal e ciencies (65%–93%, 57%–85% and 78% for COD, NH4-N and TSS, respectively), higher than that observed in the experiments with gravel. The applied loads of COD, ammonia, nitrate and TSS seem to influence the respective removal rates but only for the treatment of domestic wastewater with higher correlation coe cients for Filtralite. Regardless the type of media bed and the type of wastewater, nitrate was completely removed for nitrogen loading rates up to 1.3 g NO3-N/(m2 day). There was no evidence of the influence of nitrate loads on the removal of organic matter.  相似文献   
76.
Climate change influences populations by reducing or extirpating local populations, by disrupting patterns of migration and by shifting geographical distributions. These events can affect genetic population structure in several ways. Molecular markers have been used in numerous population genetic and phylogeographical studies of marine species and have detected population responses to climate change in the last few decades, such as range expansions, adaptative shifts and declines or increases in abundance. Little is known, however, about the molecular and physiological basis of adaptive responses to climate change in marine Mediterranean species. The Mediterranean Sea ecosystem is a ‘living laboratory’ with native species that are challenged by environmental change and by invasive species and a ‘gene-climate’ approach should be adopted as a way of focusing on the relationship between climate warming and genetic diversity.  相似文献   
77.
The time seabirds have to forage is restricted while breeding, as time at sea must be balanced against the need to take turns with the partner protecting the nest site or offspring, and timing constraints change once the breeding season is over. Combined geolocator-immersion devices were deployed on eleven Imperial Shags (four males and seven females) in Argentina (43°04′S; 64°2′W) in November 2006 and recovered in November 2007. During the breeding season, females foraged throughout the morning, males exclusively in the afternoon, and variability between individuals was low. Outside the breeding season, both sexes foraged throughout the day, and variability between individuals was high. Timing differences may be explained by higher constraints on foraging or greater demands of parental duties experienced by the smaller sex, females in this case. Sexual differences in reproductive role, feeding habits or proficiency can also lead to segregation in timing of foraging, particularly while breeding.  相似文献   
78.
Nowadays, sustainable development has been underlined as critical in relation to firm performance and is becoming a global concern. Green innovation is believed to be a fundamental approach to environmental protection and determines the firms' competitiveness. Many factors drive the success of adopting green innovation. Unfortunately, many studies generally focus on large industries. This study investigates the influence of the firms' external pressure and internal factors simultaneously on the adoption of green innovation in small enterprises in developing countries. We conceptualized the four factors that may determine the successful implementation of green innovation to achieve sustainable performance, including environmental regulations, customer pressure, resources and capabilities, and management commitment. Data were gathered from 160 food sector SMEs in Malang Raya, Indonesia. Data analysis used structural equation modeling with the partial least squares approach (SEM-PLS). The empirical results conclude the positive effects of customer pressure, resources and capabilities, and commitment management on green innovation, which in turn had a positive on sustainable performance. The results also confirmed that environmental regulations did not significantly impact green innovation. The findings provide valuable contributions and encourage SMEs to foster green innovation's potential for better sustainable performance and competitive advantage. The findings also offer integrated perspectives on how firms should be more innovative toward sustainability.  相似文献   
79.
Environmental Science and Pollution Research - This study investigated the influence of the sewage sludge (SS) soil amendment on the chronic toxicity of imidacloprid (through the seed dressing...  相似文献   
80.
Environmental Science and Pollution Research - The use of different types of zeolites (X, Na-P1, and 4A) synthesized by different methods and scales were tested in this work to adsorb nutrients...  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