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   165篇
  免费   5篇
  国内免费   81篇
  251篇
  2023年   1篇
  2021年   2篇
  2018年   1篇
  2017年   1篇
  2015年   4篇
  2014年   10篇
  2013年   5篇
  2012年   14篇
  2011年   10篇
  2010年   3篇
  2009年   1篇
  2008年   12篇
  2007年   22篇
  2006年   12篇
  2005年   24篇
  2004年   17篇
  2003年   10篇
  2002年   9篇
  2001年   6篇
  2000年   7篇
  1999年   13篇
  1998年   9篇
  1997年   5篇
  1996年   5篇
  1995年   10篇
  1993年   2篇
  1992年   2篇
  1990年   1篇
  1988年   1篇
  1987年   1篇
  1986年   2篇
  1984年   3篇
  1983年   1篇
  1982年   1篇
  1957年   7篇
  1956年   1篇
  1955年   1篇
  1954年   2篇
  1953年   1篇
  1952年   1篇
  1951年   6篇
  1950年   4篇
  1943年   1篇
排序方式: 共有251条查询结果,搜索用时 15 毫秒
71.
72.
Viruses are agents of some of the most destruc- tive diseases afflicting plants and animals[1]. Viruses also play a central role in experimental methods of molecular and cellular biology, especially in modern genetic engineering[1]. Raman spectroscopy is a pow-erful tool for studying the structure of the whole virion. A number of researches are limited to the conforma-tion of viruses, involving only nucleic acid (RNA or DNA) and its coat protein[1]. Literatures can be found concerning Raman…  相似文献   
73.
Five species of higher marine fungi were observed on the incubated drift and intertidal woods collected from the coasts of Yellow Sea and Bohai Sea. Among them, Halosphaeriopsis was a genus newly recorded for China. Taxonomy and morphology of these species were discussed in this paper. The specimens were deposited in Mycology Herbarium at Qingdao Agricultural University (MHQAU).  相似文献   
74.
Clonostachys phyllophila and Clonostachys rogersoniana were isolated from rhizosphere soil of Allium tuberosum in Chaoyang, Liaoning Province. It is the first report of the genus in China. The species was described morphologically and illustrated in this paper, the culture was stored in the Culture Collection of Liaoning Center of Culture Collection (LCCC).  相似文献   
75.
Expression of the adhesion molecules, ICAM-1, VCAM-1, NCAM, CD44, CD49d (VLA-4, a chain), and CDlla (LFA-1, a chain) on mouse oocytes, and pre- and peri-implantation stage embryos was examined by quantitative indirect immunofluorescence microscopy. ICAM-1 was most strongly expressed at the oocyte stage, gradually declining almost to undetectable levels by the expanded blastocyst stage. NCAM, also expressed maximally on the oocyte, declined to undetectable levels beyond the morula stage. On the other hand, CD44 declined from highest expression at the oocyte stage to show a second maximum at the compacted 8-cell/morula. This molecule exhibited high expression around contact areas between trophecto-derm and zona pellucida during blastocyst hatching. CD49d was highly expressed in the oocyte, remained significantly expressed throughout and after blastocyst hatching was expressed on the polar trophecto-derm. Like CD44, CD49d declined to undetectable levels at the blastocyst outgrowth stage. Expression of both  相似文献   
76.
采用Slater区分单基因和多基因遗传的计算模式及Smith无偏分析方法对21个家系资料的分析表明:利手、优势足、扣手特征均为常染色体单基因显性遗传,R型为显性性状。虽然环境因素对这类特征的表现也有一定的影响,但遗传因素仍起主要作用。 Abstract:The data of 21 families were analyzed by the method of Slater's calculating model to differentiate between single-gene and multi-gene heredity and by the method of non-deviation analysis.The results showed that the hereditary mode of handedness or preferential foot or hand-clasping is the dominant heredity of single gene of autosome,and the right type of all of them is the dominant character.In a way,although environmental factors affected the phenotypes of these characters,hereditary factors were also the decisive ones.  相似文献   
77.
The filamentous fungus Trichoderma reesei is consi-dered to be the most efficient cellulase producer, and hasa long history in the production of hydrolytic enzymes,which was widely used in the food and feed industriesand recently also used in the textile,…  相似文献   
78.
The woodpecker does not suffer head/eye impact injuries while drumming on a tree trunk with high acceleration(more than 1000×g) and high frequency.The mechanism that protects the woodpecker’s head has aroused the interest of ornithologists,biologists and scientists in the areas of mechanical engineering,material science and electronics engineering.This article reviews the literature on the biomechanisms and materials responsible for protecting the woodpecker from head impact injury and their applications in engineering and human protection.  相似文献   
79.
Tocopherols (vitamin E) are lipophilic antioxidants synthesized by all plants and are particularly abundant in seeds. Despite cloning of the complete suite of tocopherol biosynthetic enzymes and successful engineering of the tocopherol content and composition of Arabidopsis thaliana leaves and seeds, the functions of tocopherols in plants have remained elusive. To address this issue, we have isolated and characterized two VITAMIN E loci (VTE1 and VTE2) in Arabidopsis that when mutated result in tocopherol deficiency in all tissues. vte1 disrupts tocopherol cyclase activity and accumulates a redox-active biosynthetic intermediate, whereas vte2 disrupts homogentisate phytyl transferase activity and does not accumulate pathway intermediates. Mutations at either locus cause significantly reduced seed longevity compared with the wild type, indicating a critical role for tocopherols in maintaining viability during quiescence. However, only vte2 mutants exhibited severe seedling growth defects during germination and contained levels of lipid hydroperoxides and hydroxy fatty acids elevated up to 4- and 100-fold, respectively, relative to the wild type. These data demonstrate that a primary function of tocopherols in plants is to limit nonenzymatic lipid oxidation during seed storage, germination, and early seedling development. The vte mutant phenotypes also explain the strong selection for retention of tocopherol biosynthesis during the evolution of seed-bearing plants.  相似文献   
80.
中国汉族人群原纤维蛋白-1基因(FBN1)第27内含子G/A多态性   总被引:1,自引:0,他引:1  
采用PCR-ASO方法, 对日本筑波大学101名中国汉族留学人员的DNA样品进行了原纤维蛋白-1基因(FBN1)第27内含子G/A多态性测定。结果发现,A等位基因频率为0.5396,G等位基因频率为0.4604。与Tynan等人报道的数据(A和G等位基因的频率分别为0.1675和0.8325)相比,有非常显著差异(P<0 .01),提示两样本间有不同的遗传背景。 Abstract:The G/A polymorphisms in intron 27 of fibrillin-1 gene in 101 Chinese Hans who were studying and working in University of Tsukuba,Japan were analyzed with PCR-ASO method.The frequencies of A and G alleles,were 0.5396 and 0.4604 respectively.In a population sample reported by Tynan the frequency of A allele was 0.1675 that of G allele was 0.8325.The distribution of G/A polymorphism was significantly different between the two population sample(P<0.01),suggesting different genetic backgrounds.  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