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   34篇
  免费   0篇
  34篇
  2018年   2篇
  2014年   2篇
  2012年   1篇
  2011年   1篇
  2009年   4篇
  2007年   2篇
  2004年   3篇
  2000年   4篇
  1999年   2篇
  1992年   3篇
  1991年   3篇
  1990年   1篇
  1989年   1篇
  1987年   3篇
  1965年   1篇
  1916年   1篇
排序方式: 共有34条查询结果,搜索用时 11 毫秒
1.
本文记述采自新疆的皿蛛科蜘蛛一新届——颚齿蛛属Maxillodens gen.nov.及其一新种——鞭状颚齿蛛M.flageuatus sp.nov。  相似文献   
2.
The effects of freezing rate, suspending fluid and age of culture on the ability of four strains of Campylobacter pylori to survive and recover from freeze-drying were examined. Freeze-drying by standard procedures generally resulted in an overall loss in viability of between 3 and 7 log units. The exact cause of poor recovery by C. pylori was not established but strain differences were detected, with NCTC 11637 (type strain) surviving better than NCTC 11638 and NCTC 11639. Recovery of the poorest growing strain (NE 26695) was notably more erratic. The largest loss in viability occurred at the primary drying stage. Losses resulting from freezing and secondary drying were less marked and the rate of freezing had only a marginal effect on recovery. Nineteen different freeze-drying suspending fluids were investigated. Overall the best recovery results were obtained with 5% inositol-broth (or horse serum) plus 25% glucose, at pH 7.0, in which loss of viability was typically about 4 log units. Other factors, such as age of culture and number of viable bacteria in the before-dry suspension, did not have a significant effect on survival. We conclude from these results that C. pylori can survive freeze-drying, albeit in small numbers, but the degree of recovery is apparently largely strain dependent.  相似文献   
3.
The authors studied the pattern of X-ray changes detectable in the lungs of 41 patients with LCH. The results of classical X-ray study were supplemented by the data of computed tomography, ultrasonography, and 99mTc and 67Ga citrate radioisotopic studies. The diagnostic values of these techniques were compared. X-ray syndromes of changes in the lung in LCH were found to be interstitial, interstitial and granulomatous, tumorous (focal). The authors emphasize the multisystematic character of a lesion, the phasic nature and progression of the disease into fibrosis.  相似文献   
4.
Within island archipelagos, repeated ecological settings may lead to radiations wherein similar niches are recurrently occupied. Although it has been shown that species with common habitat requirements share particular traits, it remains relatively unexplored to what extent this may lead to the repeated evolution of almost identical phenotypes (phenocopies) and how this correlates with traits subjected to sexual selection. Exploring divergence patterns of ecological and sexual relevant traits within spiders seem promising to enhance our understanding of the relative role of natural and sexual selection. Here, we conduct a detailed morphological analysis on a large set of genital and non‐genital traits (morphometrics, colour pattern) within a radiation of the wolf spider genus Hogna Simon, 1885 on Galápagos and interpret these data, taking into account their known phylogenetic relationship. Our results show that recurrent environmental gradients have led to the parallel evolution of almost identical phenotypes, which not only proves that natural selection has driven morphological divergence, but also suggests that a similar genetic or developmental basis most likely underlies this divergence. Among‐species variation in genital traits in contrast rather reflects the phylogenetic relationships on Santa Cruz and San Cristóbal. The combination of these data indicate that speciation in this system is driven by the combined effect of ecological mechanisms and allopatric divergence in sexual traits. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 123–136.  相似文献   
5.
微重力对石刁柏根尖组织和细胞中钙水平及分布的影响   总被引:10,自引:0,他引:10  
徐继  阎田  赵琦 《生物物理学报》1999,15(2):381-386
用焦锑酸钾沉淀法进行了组织和细胞中游离钙的化学定位。用光学显微镜和透射电镜观察石刁柏幼苗在太空飞行后Ca2+沉淀颗粒在根尖组织和细胞内的分布。结果表明,太空飞行15天后,Ca2+在各组织内的分布情况与地面对照无明显差异,但Ca2+的含量明显低于对照。Ca2+在细胞内不同区域的分布在飞行和对照样品中差异十分明显,对照细胞中Ca2+集中在液泡内,其它细胞器中很少见到。飞行幼苗的根尖细胞,液泡中Ca2+很少,并向液泡膜集结,液泡膜内侧和细胞质中的Ca2+明显增多。细胞壁中的Ca2+较对照有明显增加,高尔基体中也有少量钙存在。本文着重讨论了飞行幼苗根尖中Ca2+在细胞内重新分布的可能作用。  相似文献   
6.
A two-step procedure for the purification of 6-phosphogluconate dehydrogenase (EC 1.1.1.44; 6-PGDH) from sheep liver is described. The enzyme is directly bound to cellulose phosphate by batch extraction and eluted with a linear salt gradient. Purification is completed by affinity chromatography using NADP(+)-agarose. The result is 6-PGDH of high purity, greatly increased yield, and the highest specific activity yet achieved, with a significant reduction in the purification time.  相似文献   
7.
8.
Temporal changes in allele frequencies were studied in host-associated populations of the small ermine moth Yponomeuta padellus. At one site, populations from three host plants (Sorbus aucuparia, Amelanchier larnarckii , and Crataegus spp.) were sampled annually during a four-year-period and analysed with 20 polymorphic allozyme markers. At two other sites, allele frequencies at 5- 6 enzyme loci of Y. padellus populations from two different host plants were also tested for consistency over a 13-year-pcriod. Significant allele frequency changes occurred in the short-term analysis, whereas allele frequencies remained relatively stable through time in the long-term analyses. Furthermore, allele frequencies of Y. padellus populations from Crataegus spp. were relatively stable compared to the other host populations. The role of the agents responsible for the observed patterns is discussed.  相似文献   
9.
Cytogenetic characteristics of the radiation-induced chromosomal instability and its persistence in human peripheral blood lymphocytes due to the bystander effect from exposure to ionizing radiation in vitro and in vivo at low and high doses has been established using a coculturing of irradiated and nonirradiated human peripheral blood lymphocytes from persons of different sexes and G-banding metaphase chromosomes staining.  相似文献   
10.
The comparative evaluation of sensitivity and specificity of the micronucleus and chromosome aberration tests for human lymphocytes at the delayed terms after acute exposure to high-dose as well as during constant exposure to low-dose gamma-radiation has been done. Accordance between these tests registered only in the cases of acute radiation sickness of second and third degrees of severity (irradiation doses above 200 cGy). Unspecificity of micronucleus test for estimation of the radiation load under constant low-intensity irradiation was found.  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