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   97篇
  免费   6篇
  103篇
  2022年   1篇
  2021年   1篇
  2020年   3篇
  2018年   2篇
  2016年   3篇
  2015年   3篇
  2014年   5篇
  2013年   4篇
  2012年   3篇
  2011年   5篇
  2010年   2篇
  2009年   3篇
  2008年   10篇
  2007年   4篇
  2006年   3篇
  2005年   3篇
  2004年   8篇
  2003年   6篇
  2002年   7篇
  2000年   1篇
  1998年   3篇
  1997年   3篇
  1995年   1篇
  1994年   2篇
  1993年   2篇
  1992年   1篇
  1991年   1篇
  1990年   4篇
  1988年   1篇
  1987年   1篇
  1985年   2篇
  1984年   1篇
  1981年   2篇
  1980年   1篇
  1966年   1篇
排序方式: 共有103条查询结果,搜索用时 0 毫秒
1.
1. In view of the suggested association between collagen and acid mucopolysaccharides in the connective tissues, this study was designed to see whether the lathyrus factor, beta-aminopropionitrile, affected the acid mucopolysaccharides as well as inhibiting the normal polymerization of collagen. The changing pattern of these two components of cartilage from normal and lathyritic chick embryos aged 14-20 days is described. The chondroitin sulphates and their protein complexes have been isolated from these cartilages, characterized and compared, particularly with respect to their sulphate content; no significant differences in quality or quantity were detectable. 2. Saline extracts of normal and lathyritic cartilages were also compared; whereas the collagen content of lathyritic extracts was increased to ten times that in the normal, the acid mucopolysaccharide content of both extracts was always the same. 3. It therefore appears that in the chick embryo beta-aminopropionitrile does not affect the acid mucopolysaccharides of the developing cartilage.  相似文献   
2.
Abstract: In efforts to determine the primary structure of intermediate filament proteins in the goldfish visual pathway, we isolated clones from a retinal λgt11 cDNA expression library that represent goldfish vimentin. We show that there are at least two forms of goldfish vimentin, designated as vimentin α and vimentin β. RNase protection assays indicate that vimentin α mRNA is expressed in low amounts in retina, optic nerve, and brain and in higher amounts in spinal cord. In contrast, vimentin β mRNA is expressed in low amounts in retina, optic nerve, brain, and spinal cord and in very high amounts in eye lens. Immunohistochemical studies show that in the optic nerve, vimentin α is mainly restricted to blood vessels, meninges, and septa. Light staining is observed with this antibody in an astrocytic glial pattern throughout the optic nerve. Two-dimensional gel analysis shows that all of these goldfish vimentins are low abundant components of optic nerve cytoskeletal preparations.  相似文献   
3.
The novel method of Fourier transform multi-pixel spectroscopy was used for the nondestructive analysis of and comparison of pigmentation in different regions of live thalli of the red alga Porphyra linearis. Because the thallus in this alga consists of a monolayer of nonoverlapping cells, we were able to analyze the pigmentation of single cells by combining light absorbance with natural fluorescence data. From the image of each cell in the vegetative male and female reproductive and holdfast regions, more than 4 ± 104 fluorescence and absorbance spectra were obtained. Specific pigments in the different regions were localized by the use of a software program of similarity mapping followed by image construction. The reconstructed images revealed subcellular localization of each pigment according to specific spectroscopic fingerprints. The results showed that the vegetative and female reproductive cell types had a significantly higher content of phycoerythrin than of phycocyanin, and quite similar chlorophyll a levels. Most of the holdfast cells were poorly pigmented, but had more chlorophyll a than phycoerythrin or phycocyanin. The male reproductive cells contained only traces of pigments. Thus, by using Fourier transform multipixel spectroscopy, we were able to characterize the pigmentation of different regions of the thallus and follow the distribution patterns of the different pigments on the subcellular level along the differentiation gradient of the alga.  相似文献   
4.
5.
Improving salinity tolerance in the most widely cultivated cereal, bread wheat (Triticum aestivum L.), is essential to increase grain yields on saline agricultural lands. A Portuguese landrace, Mocho de Espiga Branca accumulates up to sixfold greater leaf and sheath sodium (Na+) than two Australian cultivars, Gladius and Scout, under salt stress in hydroponics. Despite high leaf and sheath Na+ concentrations, Mocho de Espiga Branca maintained similar salinity tolerance compared to Gladius and Scout. A naturally occurring single nucleotide substitution was identified in the gene encoding a major Na+ transporter TaHKT1;5-D in Mocho de Espiga Branca, which resulted in a L190P amino acid residue variation. This variant prevents Mocho de Espiga Branca from retrieving Na+ from the root xylem leading to a high shoot Na+ concentration. The identification of the tissue-tolerant Mocho de Espiga Branca will accelerate the development of more elite salt-tolerant bread wheat cultivars.  相似文献   
6.
Genetic heterogeneity could reduce the power of linkage analysis to detect risk loci for complex traits such as alcohol dependence (AD). Previously, we performed a genomewide linkage analysis for AD in African-Americans (AAs) (Biol Psychiatry 65:111–115, 2009). The power of that linkage analysis could have been reduced by the presence of genetic heterogeneity owing to differences in admixture among AA families. We hypothesized that by examining a study sample whose genetic ancestry was more homogeneous, we could increase the power to detect linkage. To test this hypothesis, we performed ordered subset linkage analysis in 384 AA families using admixture proportion as a covariate to identify a more homogeneous subset of families and determine whether there is increased evidence for linkage with AD. Statistically significant increases in lod scores in subsets relative to the overall sample were identified on chromosomes 4 (P = 0.0001), 12 (P = 0.021), 15 (P = 0.026) and 22 (P = 0.0069). In a subset of 44 families with African ancestry proportions ranging from 0.858 to 0.996, we observed a genomewide significant linkage at 180 cM on chromosome 4 (lod = 4.24, pointwise P < 0.00001, empirical genomewide P = 0.008). A promising candidate gene located there, GLRA3, which encodes a subunit of the glycine neurotransmitter receptor. Our results demonstrate that admixture proportion can be used as a covariate to reduce genetic heterogeneity and enhance the detection of linkage for AD in an admixed population such as AAs. This approach could be applied to any linkage analysis for complex traits conducted in an admixed population.  相似文献   
7.
8.
In two experiments, we investigated the mate choice behavior of female Japanese quail toward taxidermically-prepared male models. Both experiments consisted of four phases: (1) habituation; (2) a pre-test in which two taxidermically-prepared models of male birds were presented; (3) observation in which the respective non-preferred male model was presented either alone or with another stimulus, and (4) a post-test in which male models were again presented alone. Results showed that focal females increased their preference for a non-preferred male model that they had previously observed with a live female (Experiment 1) or with a taxidermically-prepared female model (Experiment 2). Two control groups ruled out the possibility that focal females were choosing male models either because: (1) males were presented with an additional stimulus, or (2) females were choosing an area where they observed male models with other females. The findings suggest that female quail may utilize static, species-specific features of male conspecifics in mate choice.  相似文献   
9.
The goal of this study was to prospectively assess the long-term results of ruby laser depilation in 346 consecutive patients who underwent hair removal at 402 anatomical sites. The patients were treated using a ruby laser, with mean power ranging from 8.6 J to 15.7 J according to skin type. Results were assessed using two outcome measures-the percentage reduction in hair density and the hair-free interval. The median reduction in hair density was 55 percent (range, 0 to 100 percent) at a median time of 1 year after the last treatment session. The median hair-free interval was 8 weeks. Patients underwent a median number of four treatment sessions. Forty-three of the 346 patients were treated at more than one anatomical site. Of the sites treated, 75 percent reduction in hair density was achieved in 22 percent, 90 percent reduction was achieved in 2.2 percent, and complete depilation was achieved in only 0.7 percent. Darker colored hair was more effectively treated. Treatment efficacy was not affected by anatomical site, with the exception of the faces of male patients, which were found to be particularly resistant to treatment. There was a significant correlation between the number of treatments given and the outcome. The overall complication rate was 9.0 percent (36 of 402 sites) with respect to pigmentary changes and blistering, but varied according to Fitzpatrick skin type. The complication rate was highest in skin types V and VI (24.7 percent), with no complications in skin type I. Although a greater than 50 percent reduction in hair density was achieved in half of the 346 patients treated, complete depilation was achieved in only an extremely limited number of patients.  相似文献   
10.
Choking is a serious problem in pharyngoesophageal reconstruction, which may occur following tumor ablation of the pharynx or following corrosive injury involving the epiglottis and other parts of the upper airway. To prevent choking and the risk of severe pulmonary complications, patients have to give up oral intake and assume feeding via jejunostomy for the rest of their lives. After reconstruction of the esophagus, eight patients experienced frequent choking and aspiration. With a free jejunal flap, the inlet for food could be separated from the route of the upper airway by a diversion technique. The jejunum segment was transferred microsurgically to reconstruct the cervical esophagus, with its inlet at the buccogingival sulcus. There were no surgical complications related to either the free jejunal flap transfer or the donor site. Postoperatively, patients require re-education of their pattern of swallowing, but after the rehabilitation period all patients reported a satisfactory oral intake through the reconstructed esophagus to the abdomen without choking. There were no episodes of aspiration following reconstruction. With this new method to create a separate food pathway, patients can resume oral intake safely without choking and without permanent jejunostomy. This technique offers a useful solution for patients who suffer from recurrent choking and aspiration following injury or ablation of the pharynx.  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