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   72篇
  免费   1篇
  国内免费   3篇
  2019年   1篇
  2018年   1篇
  2016年   3篇
  2015年   6篇
  2014年   1篇
  2013年   1篇
  2011年   3篇
  2010年   3篇
  2009年   5篇
  2008年   2篇
  2007年   2篇
  2006年   2篇
  2005年   6篇
  2004年   1篇
  2003年   3篇
  2002年   2篇
  2001年   3篇
  2000年   1篇
  1997年   3篇
  1996年   3篇
  1995年   2篇
  1994年   2篇
  1993年   2篇
  1992年   3篇
  1990年   1篇
  1989年   5篇
  1986年   1篇
  1985年   5篇
  1984年   2篇
  1982年   1篇
排序方式: 共有76条查询结果,搜索用时 640 毫秒
41.
四倍体大燕麦×六倍体裸燕麦的杂种F1的产生及鉴定   总被引:6,自引:0,他引:6  
本研究以四倍体大燕麦 (AvenamagnaL .)做母本 ,六倍体裸燕麦 (AvenanudaL .)做父本进行杂交 ,利用幼胚拯救技术获得了杂种F1,并对其后代形态特征进行了观察 ;对杂种F1同工酶图谱和DNA指纹图谱进行了分析。杂种F1形态特征偏亲本或介于双亲之间 ;同工酶研究表明多数F1具有双亲互补酶带 ;RAPD分析不同引物扩增产物F1呈共显性或偏父、偏母。这些结果表明F1为真杂种  相似文献   
42.
43.
In Morocco, Clonopsis stick insects showed tangled reproductive interactions actually resulting into a network of phylogenetic relationships known as ‘reticulate evolution’. Peculiar to parthenogenetic C. gallica and C. soumiae (54 and 72 chromosomes, respectively) – closely related to the bisexual C. felicitatis (2n = 36) – is the finding of numerically polyploid karyotypes with a diploid structure. Androgenesis appeared to be the most parsimonious explanation accounting for both the low mitochondrial differentiation and the quick onset of those polyploids with structurally diploid karyotypes, paired with neat nuclear differentiations. According to a proposed model, hybrid triploid females would segregate balanced haploid and diploid 2nd oocytes immediately producing all kinds of parthenogens and androgens. Owing to these peculiar reproductive issues, we felt useful searching for stronger evidence by deeply analysing the mitochondrial genome. This new analysis showed a neat separation of sexual Tetouan haplotypes from the parthenogenetic and androgenetic ones, which are grouped in two slightly overlapping groups by network analysis: Moroccan parthenogens and androgens vs European C. gallica. It could be also envisaged that C. gallica has multiple origins, being a complex of parthenogenetic strains originated through independent hybridizations. The straightforward mechanism originating both triploid and tetraploid parthenogens well fits with both their widely ascertained low mitochondrial differentiation and the geographical closeness of the most similar samples, independently from their specific karyotype. Combining the outcomes of the hybridization events and androgenesis, which completely substitutes hybrid genomes with those of a related paternal species, would conceivably realize the observed picture of species structure and distribution. Owing to the reinforced data set, it now appears much more sensible to support androgenesis as a quick pathway to originate polyploids with numerically and genetically sharply differing chromosome sets, while maintaining, at the same time, high mitochondrial similarity.  相似文献   
44.
目的:探讨不同病理类型IV期原发性支气管肺癌的远处转移特点。方法:回顾性分析我科收治的622例诊断明确、资料完整的IV期肺癌患者,比较不同病理类型肺癌患者各器官远处转移发生率,并进行统计学分析。结果:622例IV期肺癌患者中,鳞状细胞癌188例(30.2%),腺癌275例(44.2%),小细胞癌130例(20.9%),大细胞癌5例(0.8%),腺鳞癌14例(2.3%)。平均年龄55.4岁,男女比例为2.60:1,高发年龄为40~60岁。各器官远处转移发生率从高到低依次为:骨267例(42.9%),胸膜212例(34.1%),双肺162例(26.0%),脑148例(23.8%),肝132例(21.2%),肾上腺53例(8.5%),心包50例(8.0%),皮下转移6例(1.0%),肌肉3例(0.5%),眼球和脊髓各1例(0.2%)。单器官转移共283例(45.5%),多器官转移共339例(54.5%),最多为6个器官远处转移。结论:不同病理类型肺癌有各自不同的远处转移特点及临床特征,应选择相应的检查并制定针对性治疗方案。  相似文献   
45.
目的:探讨不同病理类型IV 期非小细胞肺癌(NSCLC)患者远处转移的临床特征。方法:回顾性分析我科收治的482 例诊断 明确IV 期NSCLC 患者的临床资料,比较不同病理类型患者各器官远处转移发生率,并进行统计学分析。结果:482 例IV 期 NSCLC 患者中,鳞状细胞癌188 例(39.0%),腺癌275 例(57.1%),大细胞癌5 例(1.0%),腺鳞癌14 例(2.9%)。平均年龄55.2 岁,男 女比例为2.30:1,高发年龄为40~60 岁。各器官远处转移的发生率从高到低依次为:骨217 例(45.0%),胸膜170 例(35.3%),双肺 138例(28.6%),脑113 例(23.4%),肝85 例(17.6%),肾上腺33 例(6.8%),心包36 例(7.5%)。单器官转移221 例(45.9%),多器官转移 261例(54.1%)。T4 期患者所占比例高达44.8%,N2+3 组患者所占比例明显高于N0+1 组患者,差异有统计学意义。单纯骨、脑、肝、 肾上腺转移发生率分别为28.1%、23.9%、12.9%和15.2%。结论:NSCLC 以骨和胸膜转移最为常见,原发肿瘤情况、淋巴结转移情 况与远处转移存在一定关系,多数M1b 期患者初诊时已发生全身多部位远处转移。  相似文献   
46.
以萝卜为母本,以芥蓝为父本,采用人工去雄授粉的方法进行杂交,然后通过胚抢救(embryo rescue)得到F1代植株,并利用RAPD技术对杂种F1代幼苗进行了鉴定。RAPD鉴定结果表明:杂种表现出亲本的特异带或者亲本不具备的新谱带,有的还遗失了亲本的特异带或者共有带。  相似文献   
47.
Summary Some of results from morphological and cytological observations and esterase-isozyme studies of a rice-sorghum hybrid are presented in this paper. There is a great diversity of morphological characters and some special characteristics in the progenies of the hybrids of rice with sorghum. The meiosis of pollen mother cells in the early generations of the hybrid was found to be abnormal. One main band coinciding with one found in sorghum but lacking in rice appeared in the majority of the hybrid lines. This band is characteristic of a are the specificities of the distant hybridization of rice and sorghum, and is rarely observed in the intervariety hybrids or hybrids between subspecies of Oryza sativa, indica and japonica. On the basis of these facts we concluded that the hybrids obtained are true hybrids of rice and sorghum.  相似文献   
48.
We report here that XPA1 human pancreatic cancer cells are dimorphic. After injection in the spleen, XPA1 cells isolated from the primary tumor in the spleen were predominantly round; while cells isolated from the resulting liver metastasis and ascites were comprised of both round- and spindle-shaped cell types. Cancer cells previously grown in the spleen and re-implanted in the spleen developed large primary tumors in the spleen only. Cancer cells isolated from liver metastasis and re-transplanted to the spleen resulted in a primary tumor in the spleen and liver metastasis. Cancer cells derived from ascites and re-transplanted to the spleen developed primary tumors in the spleen and distant metastasis in the liver, lung, and diaphragm in addition to ascites formation. Spindle and round cells were differentially labeled with fluorescent proteins of different colors. After co-injection of the two cell types in the spleen, cells were isolated from the primary tumors, liver metastasis, and ascites and analyzed by color-coded fluorescence microscopy and fluorescence-activated cell sorting (FACS). No significant differences between the percentages of spindle-shaped and round cancer cells in the primary tumor and the liver metastasis were observed. However, spindle-shaped cancer cells were enriched in the ascites. One hundred percent of the spindle-shaped and round cancer cells expressed CD44, suggesting that morphology and metastatic behavior rather than CD44 expression can distinguish the stem-like cells of the XPA1 pancreatic cancer cell line. The spindle-shaped cancer cells had the greater capability for distant metastasis and ascites formation, suggesting they are stem-like cells, which can be readily targeted for therapy.  相似文献   
49.
Three new strains of the unicellular green alga Chlamydomonas reinhardtii Dangeard were isolated from soil. The isolates differed from one another and from standard laboratory strains of C. reinhardtii in a number of traits, including heavy metal resistance, protein composition, and mitochondrial DNA length. The new isolates also exhibited distinctive restriction fragment length polymorphisms in their nuclear, chloroplast, and mitochondrial genomes. The new isolates were interfertile with the standard laboratory strains and appeared to transfer chloroplast and mitochondrial genomes in a similar manner, that is, predominantly from the material (mt+) and paternal (mt?) parents, respectively.  相似文献   
50.
作物远缘杂交育种的途径及其实质   总被引:5,自引:0,他引:5  
作物远缘杂交的育种可操作性及效果多年来颇有争议,科学家对物种起源与进化的研究恰恰是指导作物远缘杂交育种的理论基础。物种形成理论研究表明生命的共同起源是远缘杂交的理论基础,生物多样性是远缘杂交的物质基础。生物种间的繁殖隔离机制是远缘杂交不亲和性障碍的根源所在,而物种形成方式又为克服远缘杂交的不亲和性提供了理论依据。其中异域性物种形成方式下的生殖隔离具有不彻底性,是克服远缘杂交受精前不亲和性的理论根据;同域性物种形成方式中多倍体化的方式对远缘杂交受精后不亲和性的克服具有较强的指导意义。本文在通过对以上方面的阐述,剖析了远缘杂交的障碍来源、克服途径及实质,为作物远缘杂交育种工作提供参考。  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