首页 | 官方网站   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   100篇
  免费   0篇
环境安全   100篇
  2023年   1篇
  2021年   1篇
  2020年   1篇
  2019年   1篇
  2018年   1篇
  2017年   1篇
  2016年   1篇
  2015年   5篇
  2014年   5篇
  2013年   7篇
  2012年   7篇
  2011年   11篇
  2010年   3篇
  2009年   7篇
  2008年   4篇
  2007年   9篇
  2006年   7篇
  2005年   6篇
  2004年   5篇
  2003年   3篇
  2002年   2篇
  2001年   1篇
  1998年   1篇
  1997年   1篇
  1996年   1篇
  1995年   3篇
  1994年   1篇
  1993年   1篇
  1990年   2篇
  1964年   1篇
排序方式: 共有100条查询结果,搜索用时 62 毫秒
1.
2.
A case of body stalk anomaly diagnosed prenatally by ultrasound during the 24th week of pregnancy in a cocaine abusing mother is presented. Accurate visualization of the fetal organs was difficult due to the severe oligohydramnios caused by premature rupture of membranes, probably related to the cocaine use. The sonographic findings were an omphalocoele, fetal attachment to the placenta, kyphoscoliosis, and absence of a floating umbilical cord. The prenatal diagnosis of the syndrome and the possible relationship with cocaine abuse are discussed.  相似文献   
3.
Fluid from pleural effusion (n=2) and cystic hygroma (n=7) was obtained from eight fetuses, between 13 and 32 weeks of pregnancy at the time when a conventional prenatal diagnosis procedure was carried out. As these fluids contain lymphocytes, they were processed like peripheral blood. A karyotype was obtained in 4 days in both cases of pleural effusion and in four out of seven samples of cystic hygroma. An abnormal karyotype was detected in three of the four samples of cystic hygroma: two trisomies 21 and a monosomy X. Different parameters were evaluated in order to predict the feasibility of obtaining a cytogenetic diagnosis. Our data showed that if the amount of fluid obtained was ⩾4 ml and the initial lymphocyte count (ILC) was >0.2 × 106 cells/ml, a cytogenetic diagnosis was possible from an initial concentration of cultured lymphocytes )ICCL) of >0.06 × 106 cells/ml.  相似文献   
4.
5.
To adequately describe seasonal rhythms in habitat utilization by fish communities, observations are needed that occur at a relatively high frequency and over large temporal windows. For the first time, images collected from a cabled video-observatory (the western Mediterranean expandable SEAfloor OBservatory; OBSEA) were utilized to examine habitat utilization by coastal fishes. Over the course of a year, hourly digital images of the water column and an artificial reef were obtained during daylight hours. For each image, the total number of species, an estimate of the abundance of individuals, and the Shannon Diversity Index were quantified. A total of 22 fish species commonly associated with nearshore western Mediterranean habitats were identified, and significant spatial (water column vs. artificial reef), seasonal (spring, summer, autumn, and winter), and daily (morning, midday, and sunset) differences in habitat utilization occurred. Four species (Diplodus vulgaris, Diplodus cervinus, Diplodus sargus, and Scorpaena porcus) were associated with the artificial reef, while one species (Pagrus pagrus) chiefly occurred in the water column. Chromis chromis and Diplodus annularis occurred at the site more frequently in the winter and autumn, respectively, while 14 other species utilized the site more frequently in either the spring (8 spp) or summer (6 spp). In addition, Dentex dentex and Spicara maena occurred more frequently at sunset, while D. cervinus displayed a crepuscular rhythm (occurring more frequently in the morning and at sunset). Species diversity was highest in the summer and lowest in the winter. If not taken into account when planning in situ sampling, such seasonal and/or diel differences may lead to spurious estimates of population sizes and biodiversity. We suggest that cabled video-observatories offer a non-invasive and reliable technology for faunistic sampling and population assessment in coastal water of the Mediterranean and likely elsewhere.  相似文献   
6.
Carotenoids may provide numerous health benefits and are also responsible for the integumentary coloration of many bird species. Despite their importance, many aspects of their metabolism are still poorly known, and even basic issues such as the anatomical sites of conversion remain controversial. Recent studies suggest that the transformation of carotenoid pigments takes place directly in the follicles during feather growth, even though the liver has been previously recognised as a storing organ for these pigments with a certain potential for conversion. In this context, we analysed the carotenoid profile of plasma, liver, skin and feathers of male Common Crossbills (Loxia curvirostra). Interestingly, the derivative feather pigment 3-hydroxy-echinenone was detected in the liver and in the bloodstream (i.e. the necessary vehicle to transport metabolites to colourful peripheral tissues). Our results demonstrate for the first time with empirical data that the liver may act as the main site for the synthesis of integumentary carotenoids. This finding contradicts previous assumptions and raises the question of possible inter-specific differences in the site of carotenoid conversion in birds.  相似文献   
7.
8.
9.
10.
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-23

京公网安备 11010802026262号