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   350篇
  免费   6篇
  国内免费   56篇
安全科学   10篇
废物处理   26篇
环保管理   22篇
综合类   89篇
基础理论   57篇
污染及防治   142篇
评价与监测   27篇
社会与环境   29篇
灾害及防治   10篇
  2024年   1篇
  2023年   7篇
  2022年   36篇
  2021年   39篇
  2020年   9篇
  2019年   12篇
  2018年   18篇
  2017年   22篇
  2016年   22篇
  2015年   17篇
  2014年   27篇
  2013年   24篇
  2012年   21篇
  2011年   21篇
  2010年   21篇
  2009年   26篇
  2008年   22篇
  2007年   9篇
  2006年   13篇
  2005年   6篇
  2004年   6篇
  2003年   4篇
  2002年   4篇
  2001年   2篇
  2000年   3篇
  1999年   1篇
  1998年   4篇
  1997年   2篇
  1996年   5篇
  1995年   3篇
  1994年   1篇
  1993年   1篇
  1992年   1篇
  1991年   1篇
  1990年   1篇
排序方式: 共有412条查询结果,搜索用时 328 毫秒
261.
262.
本文论术字菜用玉米的分类,特性,食用功效,生产开发利用途径及其应注意的问题。  相似文献   
263.
Journal of Material Cycles and Waste Management - Ports and marine transportation play important roles in the development of Vietnam, but there are increasing concerns over environmental issues...  相似文献   
264.
Three different molecular markers (i.e. seven allozyme loci, two nuclear gene loci and, mtCOI DNA sequences) were used to assess the genetic structure of the vent gastropod Lepetodrilus elevatus collected from three vent fields along the East Pacific Rise (13°N, 9°50′N and 17°S). While allozymes and nuclear loci suggested a strong stepping-stone pattern, a multivariate analysis performed on allozymic frequencies showed the presence of two distinct evolutionary lineages: the first situated in the north from 13°N to 9°50′N and the second in the south from 9°50′N to 17°S. The analysis of mitochondrial DNA sequences confirmed the separation of L. elevatus into two distinct clades with a divergence of 6.5%, which is consistent with the interspecific level of sequence variation in other vent species. A divergence time of 6–14 Mya was estimated between the two clades from previous clock calibrations. Our results suggest that these taxa followed an allopatric speciation between the northern and southern parts of the EPR with a recent demographic expansion of the southern clade to the north and a subsequent secondary contact (clade hybridisation). This speciation was probably reinforced by a habitat specialisation of the two cryptic species because the southern clade was mainly found associated with mussel-dominated communities and the northern clade with tubeworm-dominated communities. However, the analysis of shell morphology failed to separate the two cryptic species based on this sole criterion although they differed from Lepetodrilus elevatus galriftensis (Galapagos population) by a higher shell elevation. Within each clade, genetic differentiation was not related to the distance across populations and could be within vent field as important as between fields. While both clades appear to be in expansion since their speciation, significant excesses in heterozygotes suggest a very recent and local bottleneck at 17°S, probably due to massive site extinction in this region.  相似文献   
265.
The degradation of 2,2′,4,4′-tetrabromodiphenyl ether(BDE-47) by Pycnoporus sanguineus was investigated in order to explore the impact of the heavy metal Cu~(2+) on BDE-47 decomposition and the subsequent formation of metabolites, as well as to further elucidate the degradation mechanism of BDE-47. An increase in degradation rate from 18.63% to49.76% in the first four days and its stabilization at(51.26 ± 0.08)% in the following days of BDE-47 incubation were observed. The presence of Cu~(2+) at 1 and 2 mg/L was found to promote the degradation rate to 56.41% and 60.79%, respectively, whereas higher level of Cu~(2+) (≥ 5 mg/L) inhibited the removal of BDE-47. The similar concentration effects of Cu~(2+) was also found on contents of fungal protein and amounts of metabolites. Both intracellular and extracellular enzymes played certain roles in BDE-47 transportation with the best degradation rate at 27.90% and 27.67% on the fourth and third day, individually. During the degradation of BDE-47, four types of hydroxylated polybrominated diphenyl ethers(OH-PBDEs), i.e., 6′-OH-BDE-47, 5′-OH-BDE-47, 4′-OH-BDE-17, 2′-OH-BDE-28, and two bromophenols, i.e., 2,4-DBP and 4-BP were detected and considered as degradation products. These metabolites were further removed by P. sanguineus at rates of 22.42%,23.01%, 27.04%, 27.96%, 64.21%, and 40.62%, respectively.  相似文献   
266.
We studied the effect of chlorfenvinphos dermal absorption on the morphological picture of blood, on the histological and fine structure of tail skin, and on the histological structure of internal organs (lungs, heart, liver, spleen, and kidney) of rats. This study was conducted on 25 white Wistar rats, the tail skin of which was—or was not—hydrated before exposure. Rat tails were soaked in 0.5% or 0.05% chlorfenvinphos for 1 hr day for 3 months. Evident tendencies for a decrease in the absolute level of leukocytes and for an increase in the absolute level of erythrocytes in all experimental animals were observed. Histopathological changes in the internal organs were mildly manifested in only a few rats, mainly as liver and pulmonary hyperaemia. Rat tail skin at the direct exposure site showed hyperceratosis, intensive desquamation, and compensatory hyperplasia.  相似文献   
267.
Vietnam is a tropical to subtropical country located on the eastern Asian coast where the Red (Song Hong) and Mekong rivers discharge into the sea. The catchments of these two transboundary rivers cover parts of six countries, and their water and sediment discharges greatly influence the coastal seas of Vietnam. The impact of human activities include changes in the supply and distribution of water, sediments, and nutrients; changes in the relationships and balance among dynamically interacting factors and processes; and changes in the quality of the coastal and marine environments due to the increased use and accumulation of pollutants and the loss of habitats. These impacts have resulted in increasing unpredictability and severity of coastal problems such as floods, erosion, sedimentation, and saltwater intrusion; environmental pollution; and the degradation of ecosystems, with accompanying decrease in biodiversity and fishery productivity.  相似文献   
268.
Environment, Development and Sustainability - The large-scale water-induced erosion is one of the most determining elements on land degradation in subtropical monsoon-dominated region. From this...  相似文献   
269.
Environment, Development and Sustainability - The Northeastern coastal zone of Vietnam possesses high biodiversity and rich ecosystems like coral reefs, seagrasses, beaches and mangroves. It also...  相似文献   
270.
Normal levels of cancer-associated antigen (CA) 19-9, neurone-specific enolase (NSE), cancer-associated antigen (CA) 125, and mucin-like carcinoma-associated antigen (MCA) during pregnancy were determined in 87 mothers and fetuses, using a solid-phase sandwich enzyme immunoassay. CA 19-9 concentrations were higher in the fetuses, whereas the other three tumour-associated antigen levels were higher in the mothers. Only fetal NSE and MCA levels were positively correlated with those in maternal serum. Contrary to adult samples, no difference was demonstrated between male and female fetal levels of CA 125. MCA was the only maternal marker that increased significantly with gestational age between 20 and 34 weeks' pregnancy.  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