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   117篇
  免费   4篇
  2020年   1篇
  2018年   5篇
  2017年   1篇
  2016年   1篇
  2015年   2篇
  2013年   3篇
  2012年   5篇
  2011年   1篇
  2010年   1篇
  2009年   3篇
  2008年   2篇
  2007年   5篇
  2006年   5篇
  2005年   2篇
  2004年   3篇
  2003年   5篇
  2002年   4篇
  2001年   5篇
  2000年   5篇
  1999年   3篇
  1998年   3篇
  1997年   2篇
  1995年   1篇
  1993年   1篇
  1992年   1篇
  1991年   1篇
  1989年   1篇
  1987年   3篇
  1986年   2篇
  1984年   2篇
  1983年   2篇
  1980年   1篇
  1979年   1篇
  1976年   1篇
  1975年   5篇
  1973年   5篇
  1972年   4篇
  1971年   1篇
  1970年   5篇
  1969年   9篇
  1968年   4篇
  1966年   3篇
  1965年   1篇
排序方式: 共有121条查询结果,搜索用时 31 毫秒
21.
22.
23.
24.
25.
Two Fix? mutants of pea (Pisum sativum L.) which are unable to fix molecular nitrogen, E135f (sym-13) and Sprint-2Fix? (sym-31), were crossed to create the doubly homozygous recessive line, named RBT (sym-13, sym-31). The ultrastructural organization of nodules of the RBT line was compared with that of each of the two parental mutant lines and with the original wild-type genotypes of the cultivars Sparkle and Sprint-2. It was shown that the RBT line is similar to the mutant line Sprint-2Fix? in having abnormal symbiosome composition and bacteroids with relatively undifferentiated morphology. Because the phenotypic manifestation of the sym-31 mutant allele suppresses the phenotypic manifestation of the sym-13 mutant allele, it is concluded that the function of the gene Sym-31 (which is mutated in the Sprint-2Fix? line) is necessary at an earlier stage of symbiosome development than the gene Sym-13 (which is mutant in the E135f line).  相似文献   
26.
The mechanochemical preparation of solid compositions of praziquantel with plant saponin (glycyrrhizic acid disodium salt) is described. The study of a number of physicochemical parameters showed that dissolving solid compositions in water is accompanied by the inclusion of praziquantel molecules into micelles, which are formed in the solution of the glycyrrhizic acid disodium salt. Using the opisthorchiasis model caused by Opisthorchis felineus, we found a 4- to 11-fold increase in the anthelmintic activity of praziquantel in the composition as compared to the official praziquantel. According to the pharmacokinetic data, the use of the composition increased the bioavailability of praziquantel 3 times.  相似文献   
27.
Patterns of medium-term (decades) postfire succession of a mire ecosystem were studied using multiproxy paleoecological analysis. The resistance of mire ecosystems featuring thick peat deposits to fires due to surface and patchy incineration has been noted. It was found that, in favorable climatic conditions (i.e., sufficient precipitation), the vegetation cover recovers and the vertical growth and development towards oligotrophication are resumed within a medium-term period.  相似文献   
28.
Elucidation of mechanisms underlying plant tolerance to cadmium, a widespread toxic soil pollutant, and accumulation of Cd in plants are urgent tasks. For this purposes, the pea (Pisum sativum L.) mutant SGECdt (obtained by treatment of the laboratory pea line SGE with ethylmethane sulfonate) was reciprocally grafted with the parental line SGE, and four scion/rootstock combinations were obtained: SGE/SGE, SGECdt/SGECdt, SGE/SGECdt, and SGECdt/SGE. They were grown in hydroponics in the presence of 1 μM CdCl2 for 30 d. The SGE and SGECdt scions on the SGECdt rootstock had a higher root and shoot biomass and an elevated root and shoot Cd content compared with the grafts having SGE rootstock. Only the grafts with the SGE rootstock showed chlorosis and roots demonstrating symptoms of Cd toxicity. The content of nutrient elements in roots (Fe, K, Mg, Mn, Na, P, and Zn) was higher in the grafts having the SGECdt rootstock, and three elements, namely Ca, Fe, and Mn, were efficiently transported by the SGECdt root to the shoot of these grafts. The content of other measured elements (K, Mg, Na, P, and Zn) was similar in the root and shoot in all the grafts. Then, the non-grafted plants were grown in the presence of Cd and subjected to deficit or excess concentrations of Ca, Fe, or Mn. Exclusion of these elements from the nutrient solution retained or increased differences between SGE and SGECdt in growth response to Cd toxicity, whereas excess of Ca, Fe, or Mn decreased or eliminated such differences. The obtained results assign a principal role of roots to realizing the increased Cd-tolerance and Cdaccumulation in the SGECdt mutant. Efficient translocation of Ca, Fe, and Mn from roots to shoots appeared to counteract Cd toxicity, although Cd was actively taken up by roots and accumulated in shoots.  相似文献   
29.
Mosquitoes transmit a diverse group of human flaviviruses including West Nile, dengue, yellow fever, and Zika viruses. Mosquitoes are also naturally infected with insect‐specific flaviviruses (ISFs), a subgroup of the family not capable of infecting vertebrates. Although ISFs are not medically important, they are capable of altering the mosquito's susceptibility to flaviviruses and may alter host fitness. Wolbachia is an endosymbiotic bacterium of insects that when present in mosquitoes limits the replication of co‐infecting pathogens, including flaviviruses. Artificially created Wolbachia‐infected Aedes aegypti mosquitoes are being released into the wild in a series of trials around the globe with the hope of interrupting dengue and Zika virus transmission from mosquitoes to humans. Our work investigated the effect of Wolbachia on ISF infection in wild‐caught Ae. aegypti mosquitoes from field release zones. All field mosquitoes were screened for the presence of ISFs using general degenerate flavivirus primers and their PCR amplicons sequenced. ISFs were found to be common and widely distributed in Ae. aegypti populations. Field mosquitoes consistently had higher ISF infection rates and viral loads compared to laboratory colony material indicating that environmental conditions may modulate ISF infection in Ae. aegypti. Surprisingly, higher ISF infection rates and loads were found in Wolbachia‐infected mosquitoes compared to the Wolbachia‐free mosquitoes. Our findings demonstrate that the symbiont is capable of manipulating the mosquito virome and that Wolbachia‐mediated viral inhibition is not universal for flaviviruses. This may have implications for the Wolbachia‐based DENV control strategy if ISFs confer fitness effects or alter mosquito susceptibility to other flaviviruses.  相似文献   
30.
An actinomycetous culture designated as LIA-0721 was isolated from a soil sample. It was close to Act. fulvoviolaceus by its morphologo-cultural features and differed from it in production of melanoid pigments and the spectrum of carbohydrate assimilation. This justified its classification as Act. fulvoviolaceus var. achromogenes var. nov. The culture produced new aromatic heptaens, i. e. fulvomycins A, B and C. Their physico- chemical and biological characteristics are presented.  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