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   126篇
  免费   10篇
  2021年   5篇
  2020年   2篇
  2019年   3篇
  2017年   1篇
  2016年   5篇
  2015年   4篇
  2014年   7篇
  2013年   9篇
  2012年   12篇
  2011年   8篇
  2010年   10篇
  2008年   6篇
  2007年   14篇
  2006年   15篇
  2005年   11篇
  2004年   10篇
  2003年   4篇
  2002年   1篇
  1997年   1篇
  1995年   1篇
  1991年   2篇
  1990年   2篇
  1986年   2篇
  1985年   1篇
排序方式: 共有136条查询结果,搜索用时 171 毫秒
131.
Dunja Begovi&#x; 《Bioethics》2019,33(8):958-964
Traditionally, two main rationales for the provision of prenatal testing and screening are identified: the expansion of women’s reproductive choices and the reduction of the burden of disease on society. With the number of prenatal tests available and the increasing potential for their widespread use, it is necessary to examine whether the reproductive autonomy model remains useful in upholding the autonomy of pregnant women or whether it allows public health considerations and even eugenic aims to be smuggled in under the smokescreen of autonomy. In this article I argue that if we are serious about upholding women’s autonomy in the context of prenatal testing, what is needed is a model based on a more robust conception of reproductive autonomy, such as the one defended by Josephine Johnston and Rachel Zacharias as ‘reproductive autonomy worth having’. While Johnston and Zacharias put forward a basic outline of this conception, I apply it to the specific case of prenatal testing and show how it responds to objections levelled against the reproductive autonomy model. I argue that adopting this kind of conception is necessary to avoid fundamental challenges to women’s autonomy when it comes to prenatal screening and testing.  相似文献   
132.
Wild boars shot in a hunting area in Baden-Württemberg during three consecutive years (148 males, 205 females) were analysed for insulin-like growth factor 1 (IGF-I) concentrations in blood plasma. Gonadal steroids were determined either in blood plasma (females, progesterone) or adipose tissue (males, androstenone). The age (estimated by the dental pattern) and the carcass weight were recorded. From 159 out of the 353 animals, the stomach content was analysed for total energy and digestibility. Sex differences in carcass weight were only significant in animals above the age of 14 months. Carcass weight was significantly correlated with IGF-I in males but not in females. IGF-I revealed a sex-specific seasonal pattern (maximum concentrations in males, June; in females, October). Additionally, as indicated by analyses of the stomach content, the digestibility of the food had affected IGF-I concentrations. Gonadal steroids revealed the well-known seasonal pattern described in other studies and did not point to a more aseasonal pattern of reproduction when energy supply is artificially increased by baiting.  相似文献   
133.
134.
  1. Omnivory is widespread in food webs, with an important stabilising effect. The strength of omnivorous trophic interactions may change considerably with changes in the local environment.
  2. Shallow temporary waters are often characterised by high levels of inorganic turbidity that may directly limit the food uptake of filter-feeding organisms, but there is little evidence on how it might affect omnivorous species. Anostracans are key species of temporary waters and recent evidence suggests that these organisms are omnivorous consumers of both phyto- and zooplankton.
  3. Using Branchinecta orientalis as a model species, our aim was to test how turbidity affects the feeding of an omnivorous anostracan. To do this, we used short-term feeding experiments and stable isotope analyses, with animals collected from soda pans in eastern Austria. In the feeding experiments, algae and zooplankton were offered as food either separately or in combination. The prey type treatments were crossed with turbidity levels in a factorial design.
  4. There was a pronounced decrease in the ingested algal biomass with increasing turbidity. Conversely, ingestion rates on zooplankton were less affected by turbidity. Stable isotope analyses from field material supported our experimental results by showing a positive relationship of the trophic position of anostracans and the trophic niche of the communities with turbidity.
  5. Our results show that turbidity modulates the intraguild trophic relationship between anostracans and their prey by shifting the diet of anostracans from more herbivorous in transparent to more carnivorous in turbid waters. Thus, inorganic turbidity might also have a community-shaping role in plankton communities of temporary waters through altering trophic relationships.
  相似文献   
135.
The rise and consequences of polyploidy in vertebrates, whose origin was associated with genome duplications, may be best studied in natural diploid and polyploid populations. In a diploid/tetraploid (2n/4n) geographic contact zone of Palearctic green toads in northern Kyrgyzstan, we examine 4ns and triploids (3n) of unknown genetic composition and origins. Using mitochondrial and nuclear sequence, and nuclear microsatellite markers in 84 individuals, we show that 4n (Bufo pewzowi) are allopolyploids, with a geographically proximate 2n species (B. turanensis) being their maternal ancestor and their paternal ancestor as yet unidentified. Local 3n forms arise through hybridization. Adult 3n mature males (B. turanensis mtDNA) have 2n mothers and 4n fathers, but seem distinguishable by nuclear profiles from partly aneuploid 3n tadpoles (with B. pewzowi mtDNA). These observations suggest multiple pathways to the formation of triploids in the contact zone, involving both reciprocal origins. To explain the phenomena in the system, we favor a hypothesis where 3n males (with B. turanensis mtDNA) backcross with 4n and 2n females. Together with previous studies of a separately evolved, sexually reproducing 3n lineage, these observations reveal complex reproductive interactions among toads of different ploidy levels and multiple pathways to the evolution of polyploid lineages.  相似文献   
136.
Colon cancer is one of the most reasons for cancer death worldwide. Thus, it is important to find new prognostic and diagnostic marker, as well as to throw light on the special metabolic pathways of colon cancer cells. This paper highlights for the first time some qualitative differences in the profiles of the volatile metabolites of colon cancer cell lines SW 480 (grade IV, Duke B) and SW 1116 (grade II, Duke A) among themselves and in comparison to the normal colon cell line NCM460, which are mostly represented by ketones and alcohols. These results, which were obtained by applying solid phase micro extraction (SPME) and combined gas chromatography/mass spectrometry (GC/MS), are consistent with Warburg’s hypothesis because the found reaction products may indicate that the cancer cells show the Crabtree’s effect. Furthermore, compounds like undecan-2-ol and pentadecan-2-one were associated for the first time with the human metabolism. In summary, these findings indicate that the metabolism of colon cancer cells differs extremely from the metabolism of healthy cells and it changes during the progress of the disease. Compounds that are present in the breath, the blood and the tissue of patients represent the differences and they can serve as new biomarker for colon cancer in future.  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