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   169篇
  免费   15篇
  2021年   1篇
  2020年   3篇
  2019年   8篇
  2018年   3篇
  2017年   2篇
  2016年   10篇
  2015年   6篇
  2014年   9篇
  2013年   14篇
  2012年   11篇
  2011年   6篇
  2010年   7篇
  2009年   5篇
  2008年   8篇
  2007年   11篇
  2006年   7篇
  2005年   11篇
  2004年   10篇
  2003年   2篇
  2002年   3篇
  2001年   4篇
  2000年   1篇
  1999年   3篇
  1998年   2篇
  1997年   3篇
  1996年   2篇
  1995年   3篇
  1994年   4篇
  1993年   1篇
  1992年   1篇
  1991年   2篇
  1990年   5篇
  1989年   5篇
  1988年   2篇
  1986年   1篇
  1985年   1篇
  1979年   2篇
  1973年   1篇
  1972年   2篇
  1971年   1篇
  1969年   1篇
排序方式: 共有184条查询结果,搜索用时 15 毫秒
1.
Various operative methods for the correction of Stahl's ear exist. We, however, have devised an alternative "turnover and rotation" procedure. In this procedure, the deformed cartilage itself is used in its original contour to form a new scaphoid fossa, thus simplifying the corrective procedure and establishing a reliable operative method in which reversion to the original state is thought to be highly unlikely.  相似文献   
2.
3.
Our technique for the correction of cryptotia using both Z-plasty and the advancement flap is described. The main advantages are the simple design of the skin incision and the possibility of its application to cryptotia other than severe cartilage deformity and extreme lack of skin.  相似文献   
4.
In an 18 year old Japanese larch stand, leaf characteristics such as area, weight, gross photosynthetic rate and respiration rate were studied in order to obtain basic information on estimating canopy photosynthesis and respiration. The leaf growth courses in area and weight from bud opening were approximated by simple logistic curves. The growth coefficient for the area growth curve was 0.155–0.175 day−1, while that for the weight growth was 0.112–0.117 day−1. The larger growth coefficient in area growth caused the seasonal change in specific leaf area (SLA) that increased after bud opening to its peak early in May at almost 300 cm2 g−1 and then decreased until it leveled off at about 140 cm2g−1. The change inSLA indicates the possibility that leaf area growth precedes leaf thickness growth. The relationship between the coefficientsa andb of the gross photosynthetic rate (p)-light flux density (1) curve (p=bI/(1+aI)) and the mean relative light flux density (I′/I 0) at each canopy height were approximated by hyperbolic formulae:a=A/(I′/I 0)+B andb=C/(I′/I 0)+D. Leaf respiration rate was also increased with increasingI′/I 0. Seasonal change of gross photosynthetic rate and leaf respiration rate were related to mean air temperature through linear regression on semilogarithmic co-ordinates.  相似文献   
5.
Seasonal changes and yearly gross canopy photosynthetic production were estimated for an 18 year old Japanese larch (Larix leptolepis) forest between 1982 and 1984. A canopy photosynthesis model was applied for the estimation, which took into account the effect of light interception by the non-photosynthetic organs. Seasonal changes in photosynthetic ability, amount of canopy leaf area and light environment within the canopy were also taken into account. Amount of leaf area was estimated by the leaf area growth of a single leaf. The change of light environment within the canopy during the growing season was estimated with a light penetration model and the leaf increment within the canopy. Canopy respiration and surplus production were calculated as seasonal and yearly values for the three years studied. Mean yearly estimates of canopy photosynthesis, canopy respiration and surplus production were 37, 13 and 23 tCO2 ha−1 year−1, respectively. Vertical trend, seasonal changes and yearly values of the estimates were analyzed in relation to environmental and stand factors.  相似文献   
6.
5-Aminosalicylic acid given to rats as a single intravenous injection led to necrosis of the proximal convoluted tubules and of the renal papilla. These two lesions developed at the same time and the cortical lesions did not appear to be a consequence of the renal papillary necrosis. Since the compound possesses the molecular structure both of a phenacetin derivative and of a salicylate these observations may be relevant to the problem of renal damage incident to abuse of analgesic compounds and suggest the possibility that in this syndrome cortical lesions may develop independently of renal papillary necrosis.  相似文献   
7.
Summary Genetically defined alkaline phosphatase (ALP) isozymes from the larval midgut tissues ofBombyx mori were purified and characterized. The membrane-bound form (m-ALP) was solubilized with 1% Triton X-100, then purified by DEAE-Sephacel, Con A-Sepharose 4B and Ultrogel AcA 34 column chromatography. The soluble form (s-ALP) was purified by DEAE-Sephacel, epoxy Toyopearl coupled with phosphonic acid and Ultrogel AcA 34 column chromatography. About 840- and 650-fold purification were achieved for m-ALP and s-ALP, respectively, and both ALPs were homogeneous as judged by poly-acrylamide gel electrophoresis. Both forms were found to be similar (MW=68 000 in gel permeation chromatography, and a single subunit as a monomer in denaturing SDS-polyacrylamide gels with MW=58 000 for m-ALP and MW=61 000 for s-ALP). The pH optima of ALPs were shown to lie at 10.9 (m-ALP) and 9.8 (s-ALP), the former being extremely stable even in pH 10–12 which accords with the physiological milieu inBombyx midgut lumen. The Km values of the m-ALP and s-ALP forp-nitrophenyl phosphate were 1.99 and 1.49 mM, respectively. Both ALPs had a similar substrate specificity.l-Cysteine strongly inhibited both ALPs, but inhibitory effects ofl-phenylalanine,l-homoarginine andl-leucine were undetectable for s-ALP and very weak for m-ALP. A comparison of enzymatic properties on two ALPs suggested that each isozyme plays different roles.Abbreviations m-ALP membrane-bound alkaline phosphatase - s-ALP soluble alkaline phosphatase  相似文献   
8.
9.
Bonobos (Pan paniscus) inhabit regions south of the Congo River including all areas between its southerly tributaries. To investigate the genetic diversity and evolutionary relationship among bonobo populations, we sequenced mitochondrial DNA from 376 fecal samples collected in seven study populations located within the eastern and western limits of the species’ range. In 136 effective samples from different individuals (range: 7–37 per population), we distinguished 54 haplotypes in six clades (A1, A2, B1, B2, C, D), which included a newly identified clade (D). MtDNA haplotypes were regionally clustered; 83 percent of haplotypes were locality-specific. The distribution of haplotypes across populations and the genetic diversity within populations thus showed highly geographical patterns. Using population distance measures, seven populations were categorized in three clusters: the east, central, and west cohorts. Although further elucidation of historical changes in the geological setting is required, the geographical patterns of genetic diversity seem to be shaped by paleoenvironmental changes during the Pleistocene. The present day riverine barriers appeared to have a weak effect on gene flow among populations, except for the Lomami River, which separates the TL2 population from the others. The central cohort preserves a high genetic diversity, and two unique clades of haplotypes were found in the Wamba/Iyondji populations in the central cohort and in the TL2 population in the eastern cohort respectively. This knowledge may contribute to the planning of bonobo conservation.  相似文献   
10.
AMPA receptors (AMPARs) are glutamate-gated ion channels ubiquitous in the vertebrate central nervous system, where they mediate fast excitatory neurotransmission and act as molecular determinants of memory formation and learning. Together with detailed analyses of individual AMPAR domains, structural studies of full-length AMPARs by electron microscopy and x-ray crystallography have provided important insights into channel assembly and function. However, the correlation between the structure and functional states of the channel remains ambiguous particularly because these functional states can be assessed only with the receptor bound within an intact lipid bilayer. To provide a basis for investigating AMPAR structure in a membrane environment, we developed an optimized reconstitution protocol using a receptor whose structure has previously been characterized by electron microscopy. Single-channel recordings of reconstituted homomeric GluA2flop receptors recapitulate key electrophysiological parameters of the channels expressed in native cellular membranes. Atomic force microscopy studies of the reconstituted samples provide high-resolution images of membrane-embedded full-length AMPARs at densities comparable to those in postsynaptic membranes. The data demonstrate the effect of protein density on conformational flexibility and dimensions of the receptors and provide the first structural characterization of functional membrane-embedded AMPARs, thus laying the foundation for correlated structure-function analyses of the predominant mediators of excitatory synaptic signals in the brain.  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