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   253篇
  免费   33篇
  2023年   2篇
  2021年   2篇
  2020年   1篇
  2019年   1篇
  2018年   2篇
  2016年   8篇
  2015年   14篇
  2014年   14篇
  2013年   16篇
  2012年   18篇
  2011年   17篇
  2010年   13篇
  2009年   11篇
  2008年   17篇
  2007年   12篇
  2006年   18篇
  2005年   14篇
  2004年   21篇
  2003年   9篇
  2002年   7篇
  2001年   6篇
  2000年   3篇
  1999年   1篇
  1998年   4篇
  1997年   1篇
  1996年   1篇
  1994年   1篇
  1992年   4篇
  1991年   2篇
  1989年   2篇
  1988年   2篇
  1987年   1篇
  1983年   1篇
  1981年   2篇
  1977年   1篇
  1976年   4篇
  1974年   5篇
  1973年   3篇
  1972年   2篇
  1971年   2篇
  1970年   1篇
  1969年   4篇
  1966年   4篇
  1964年   1篇
  1962年   2篇
  1961年   1篇
  1960年   2篇
  1959年   2篇
  1940年   1篇
  1939年   1篇
排序方式: 共有286条查询结果,搜索用时 343 毫秒
101.
102.
103.
Objective: To establish the mental health needs of homeless children and families before and after rehousing. Design: Cross sectional, longitudinal study. Setting: City of Birmingham. Subjects: 58 rehoused families with 103 children aged 2-16 years and 21 comparison families of low socioeconomic status in stable housing, with 54 children. Main outcome measures: Children’s mental health problems and level of communication; mothers’ mental health problems and social support one year after rehousing. Results: Mental health problems remained significantly higher in rehoused mothers and their children than in the comparison group (mothers 26% v 5%, P=0.04; children 39% v 11%, P=0.0003). Homeless mothers continued to have significantly less social support at follow up. Mothers with a history of abuse and poor social integration were more likely to have children with persistent mental health problems. Conclusions: Homeless families have a high level of complex needs that cannot be met by conventional health services and arrangements. Local strategies for rapid rehousing into permanent accommodation, effective social support and health care for parents and children, and protection from violence and intimidation should be developed and implemented.

Key messages

  • Homeless children and their mothers have a high level of mental health problems
  • Homeless families experience many risk factors, such as domestic violence, abuse, and family and social disruption
  • In two fifths of children and a quarter of mothers, mental health problems persisted after rehousing
  • In contrast with a comparison group of families of low socioeconomic status, a substantial proportion of homeless families remained residentially and socially unstable
  相似文献   
104.
Summary A mixed wild culture of thermophilic bacteria degraded 86% of 2% cellulose in 96 h with production of liquid (ethanol, acetic and propionic acids, and ethylesters of these acids) and gaseous products (hydrogen and carbon dioxide).  相似文献   
105.
Major quantitative, but not qualitative, differences in the various species of proteins in purified membranes from Streptococcus pyogenes and its stabilized L-form have been demonstrated by acidic and alkaline disc gel electrophoresis with and without urea. The fact that no significant differences in the amino acid content or composition between these two membranes could be demonstrated emphasizes that these results are probably due to changes in the relative amounts of the various species of proteins in this subcellular component. The possibility of these protein changes in the L-form membrane being related to its inability to synthesize a rigid cell wall is discussed. Finally, phage-associated lysin, routinely used for removal of the group A streptococcal cell wall, does not appear to affect the protein profile or amino acid composition of the membrane either metabolically or nonmetabolically.  相似文献   
106.
Membrane lipoteichoic acid continues to be synthesized by an osmotically fragile, stabilized L-form of Streptococcus pyogenes. Chromatographic and electrophoretic comparisons indicate that the lipid componenent of lipoteichoic acid in this L-form and its parental streptococcus is glycerophosphoryldiglucosyl diglyceride and not phosphatidylkojibiosyl diglyceride. Based upon dry weight determinations, the yield of lipoteichoic acid from the L-form is 0.19%, as compared with 0.97% from the streptococcus. When grown with bacitracin the L-form contains the same amount of teichoic acid as when grown without this antibiotic; however, its lipoteichoic acid content is reduced by 85%. Similarly, the L-form grown with novobiocin for 10 h contains only 17% of the teichoic acid found in control cells.  相似文献   
107.
Protein Structural Interactome map (PSIMAP) is a global interaction map that describes domain-domain and protein-protein interaction information for known Protein Data Bank structures. It calculates the Euclidean distance to determine interactions between possible pairs of structural domains in proteins. PSIbase is a database and file server for protein structural interaction information calculated by the PSIMAP algorithm. PSIbase also provides an easy-to-use protein domain assignment module, interaction navigation and visual tools. Users can retrieve possible interaction partners of their proteins of interests if a significant homology assignment is made with their query sequences. AVAILABILITY: http://psimap.org and http://psibase.kaist.ac.kr/  相似文献   
108.
109.
The Streptomyces phage C31 encodes an integrase belonging to the serine recombinase family of site-specific recombinases. The well studied serine recombinases, the resolvase/invertases, bring two recombination sites together in a synapse, and then catalyse a concerted four-strand staggered break in the DNA substrates whilst forming transient covalent attachments with the recessed 5′ ends. Rotation of one pair of half sites by 180° relative to the other pair occurs, to form the recombinant configuration followed by ligation of the DNA backbone. Here we address the nature of the recombination intermediates formed by C31 integrase when acting on its substrates attP and attB. We have identified intermediates containing integrase covalently attached to cleaved DNA substrates, attB or attP, by analysis of complexes in gels and after treatment of these complexes with proteinases. Using a catalytically inactive integrase mutant, S12A, the synaptic complexes containing integrase, attP and attB were identified. Furthermore, we have shown that attB mutants containing insertions or deletions are blocked in recombination at the stage of strand cleavage. Thus, there is a strict spacing requirement within attB, possibly for correct positioning of the catalytic serine relative to the scissile phosphate in the active site. Finally, using integrase S12A we confirmed the inability of attL and attR or other combinations of sites to form a stable synapse, indicating that the directionality of integrative recombination is determined at synapsis.  相似文献   
110.
The feeding behaviour of the pine processionary (PPC) caterpillar Thaumetopoea pityocampa Den. and Schiff. (Lepidoptera, Thaumetopoeidae) in L3-L4 stages was explored by means of laboratory arena feeding trials and natural substrates. In the bioassays, volatile extracts of 15 pine species, 8 of which are naturally growing in Greece, were incorporated. An analytical model was developed based on the principle of multinomial logit regression with five outcomes on the basis of the behavioural feeding sequence of the caterpillars. The outcomes were the five steps in which the feeding behavioural sequence was decomposed. The model's suitability (MacFadden's rho(2)=0.229, P<10(-4)) was examined when including 10 terpenes that were judged significant through a stepwise canonical discriminant analysis. The proposed model was superior to a random one and the two models resulting from the addition and subtraction of 4 terpenes to the already 10 existing compounds. The most informative model was built on the terpenes caryophyllene oxide, terpinolene, myrcene, germacrene D, eudesmol, limonene, beta-pinene, beta-caryophyllene, alpha-pinene and manoyl oxide. The background terpenes were present in the model and of particular importance. No special behavioural role, either as promoter or inhibitor could be assigned to the individual volatile metabolites, since no constant pattern among behavioural steps was observed. For instance, beta-caryophyllene while acts as promoter of attraction and trial bite it is a suppressor of partial feeding and strongly inhibits complete needle consumption. The monoterpene limonene, on the other hand, seems to be a suppressor of partial and complete feeding. The overall methodological scheme and the analytical modelling tool could be proved a suitable research protocol in unfolding the ecological role of a complex mixture of secondary metabolites. Those who develop safe practical systems can use this.  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