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   109篇
  免费   9篇
  国内免费   1篇
  2019年   2篇
  2018年   2篇
  2017年   1篇
  2016年   3篇
  2015年   4篇
  2014年   4篇
  2013年   6篇
  2012年   4篇
  2011年   3篇
  2010年   5篇
  2009年   11篇
  2008年   9篇
  2007年   9篇
  2006年   4篇
  2005年   5篇
  2004年   3篇
  2003年   6篇
  2001年   4篇
  2000年   2篇
  1999年   2篇
  1998年   2篇
  1997年   10篇
  1996年   3篇
  1995年   2篇
  1994年   2篇
  1993年   1篇
  1992年   1篇
  1987年   1篇
  1986年   1篇
  1985年   1篇
  1983年   1篇
  1982年   1篇
  1979年   1篇
  1957年   1篇
  1956年   1篇
  1955年   1篇
排序方式: 共有119条查询结果,搜索用时 15 毫秒
81.
Three new species of Rubus subgenus Rubus series Pallidi from Spain are described, mapped and illustrated: R. Cyclops, R. castroviejoi and R. urbionicus.  相似文献   
82.
BackgroundMany data are available on expansion protocols for mesenchymal stromal cells (MSCs) for both experimental settings and manufacturing for clinical trials. However, there is a lack of information on translation of established protocols for Good Manufacturing Practice (GMP) from validation to manufacturing for clinical application. We present the validation and translation of a standardized pre-clinical protocol for isolation and expansion of MSCs for a clinical trial for reconstitution of alveolar bone.MethodsKey parameters of 22 large-scale expansions of MSCs from bone marrow (BM) for validation were compared with 11 expansions manufactured for the clinical trial “Jaw bone reconstruction using a combination of autologous mesenchymal stromal cells and biomaterial prior to dental implant placement (MAXILLO1)” aimed at reconstruction of alveolar bone.ResultsDespite variations of the starting material, the robust protocol led to stable performance characteristics of expanded MSCs. Manufacturing of the autologous advanced therapy medicinal product MAXILLO-1-MSC was possible, requiring 21 days for each product. Transport of BM aspirates and MSCs within 24 h was guaranteed. MSCs fulfilled quality criteria requested by the national competent authority. In one case, the delivered MSCs developed a mosaic in chromosomal finding, showing no abnormality in differentiation capacity, growth behavior or surface marker expression during long-term culture. The proportion of cells with the mosaic decreased in long-term culture and cells stopped growth after 38.4 population doublings.ConclusionsClinical use of freshly prepared MSCs, manufactured according to a standardized and validated protocol, is feasible for bone regeneration, even if there was a long local distance between manufacturing center and clinical site. Several parameters, such as colony forming units fibroblasts (CFU-F), percentage of CD34+ cells, cell count of mononuclear cells (MNCs) and white blood cells (WBCs), of the BM may serve as a predictive tool for the yield of MSCs and may help to avoid unnecessary costs for MSC manufacturing due to insufficient cell expansion rates.  相似文献   
83.
To analyse the status and phylogeny of the genusPhyllocladus,seedsof all seven species of the genus were studied. The complexof features of thePhyllocladusreproductive system point to theisolated position of the genus within the conifers. Relationswith Podocarpaceae s. l., Taxaceae s. l. and Cephalotaxaceaeappeared to be remote because a complex of features clearlydistinguishesPhyllocladusfrom the afore-mentioned taxa. We findit advisable to circumscribe the family Phyllocladaceae as Bessey(1907) did, and place it into the order Taxales Knobl. in Warming(1890). From investigations of the seeds it appears the genusPhyllocladusconsistsof seven species, forming five groups. There is a significanttendency for transformation of the female reproductive structureswithin the generic boundaries ofPhyllocladus—seeds, originallysolitary, tending to aggregate in various kinds of compact clusters.Copyright1999 Annals of Botany Company PhyllocladusL. C. & A. Rich, ex Mirb., seed anatomy, seed morphology, systematics, phylogenetic relationships, Phyllocladaceae, Podocarpaceae s. str., Acmopyleaceae, Nageiaceae, Austrotaxaceae, Amentotaxaceae, Torreyaceae, Taxaceae, s. str., Cephalotaxaceae, Taxales.  相似文献   
84.
Plant suspension cell cultures display many features of the innate immune responses observed in planta and have been extensively applied to the study of basal and race-specific defences. However, no single model including photosynthetic cultured cells has been used for the exhaustive characterization of both basal and race-specific defences to date. In this article, we report the activation of basal and race-specific defences in green cultured cells from Arabidopsis thaliana . Inoculation of cultured cells with isogenic virulent or avirulent strains of Pseudomonas syringae pv. tomato DC3000 (Pst) was used to evaluate race-specific defences. The proliferation of avirulent Pst was found to be lower than that of virulent Pst in the inoculated cultures. Extracellular pH changes, sustained oxidative burst (5–13 h post-inoculation), enhancement of salicylic acid, and massive cell death were specifically stimulated by the avirulent bacterium. Neither avirulent nor virulent Pst induced markers of basal resistance, such as callose deposition or early oxidative burst (1–5 h post-inoculation). However, both basal defences were activated when cells were exposed to Pseudomonas syringae pv. phaseolicola or to the Pst mutant defective in the type III secretion system (TTSS), Pst-hrpL. Thus, in these cells, basal defences may be inhibited by Pst in a TTSS-dependent manner. Recapitulation of classical defence features demonstrates the usefulness of this system for the fine characterization of plant innate immune components.  相似文献   
85.
The phylogeographic architecture of the common vole, Microtus arvalis, has been well‐studied using mitochondrial DNA and used to test hypotheses relating to glacial refugia. The distribution of the five described cytochrome b (cyt b) lineages in Europe west of Russia has been interpreted as a consequence of postglacial expansion from both southern and central European refugia. A recently proposed competing model suggests that the ‘cradle’ of the M. arvalis lineages is in western central Europe from where they dispersed in different directions after the Last Glacial Maximum. In the present study, we report a new cyt b lineage of the common vole from the Balkans that is not closely related to any other lineage and whose presence might help resolve these issues of glacial refugia. The Balkan phylogroup occurs along the southern distributional border of M. arvalis in central and eastern Bosnia and Herzegovina, Montenegro, and eastern Serbia. Further north and west in Slovenia, Bosnia and Herzegovina, and Serbia, common voles belong to the previously‐described Eastern lineage, whereas both lineages are sympatric in one site in Bosnia and Herzegovina. The Balkan phylogroup most reasonably occupied a glacial refugium already known for various Balkan endemic species, in contrast to the recently proposed model. South‐east Europe is an absolutely crucial area for understanding the postglacial colonization history of small mammals in Europe and the present study adds to the very few previous detailed phylogeographic studies of this region. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 788–796.  相似文献   
86.
According to current systematics, Festuca inops and F. gracilior are two distinct species. However, they are hardly distinguishable from each other on the basis of their morphological characters. Festuca inops is considered a diploid species endemic to Italy, while F. gracilior has a discontinuous distribution area, apparently related to chromosomal levels: diploid populations in Italy and south-east France, tetraploid populations in north-east Spain. The diploid populations of both taxa from Italy and south-east France are investigated in the present study. Nearly 1000 exsiccata were examined and morphometric analysis was carried out on macro- and micromorphological features of 119 specimens (including type-specimens) and on 20 natural populations (including loci classici ). All these data showed that the two species should be referred to a single taxon, for which the rank of species seems to be appropriate. This result is supported by karyological, ecological and chorological data and was confirmed by the results of ISSR analysis. According to nomenclatural rules, the legitimate name for the species is Festuca inops De Not.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 151 , 239–258.  相似文献   
87.
1. Sympatric populations of insects adapted to different host plants are good model systems not only to study how they adapt to the chemistry of their food plant, but also to investigate whether morphological modifications evolved enabling them to live successfully on a certain plant species. 2. The pea aphid, Acyrthosiphon pisum (Harris) encompasses at least 11 genetically distinct sympatric host races, each showing a preference for a certain legume species. The leaflet surfaces of these legumes differ considerably in their wax coverage. 3. It was investigated whether the attachment structures of three pea aphid genotypes from different host races are adapted to the different surface properties of their host plants and whether they show differences in their attachment ability on the respective host and non‐host plants. 4. The surface morphology of plants and aphid tarsi was examined using SEM (scanning electron microscopy). The ability of the aphids to walk on specific surfaces was tested using traction force measurements. 5. The presence of wax blooms on the leaflets lowers the aphids' attachment ability considerably and diminishes their subsequent attachment on ‘neutral’ surfaces like glass. The pea aphid host races differ in their ability to walk on certain surfaces. However, the genotype from the adapted aphid host race was not necessarily the one with the best walking performance on their host plant. All aphids, regardless of the original host plant, were most efficient on the neutral control surface glass. The general host plant Vicia faba was the plant with the most favourable surface for all aphid host races.  相似文献   
88.
89.
ABSTRACT

Here we present an acoustic approach for reliable sexing in four whistling duck species from the genus Dendrocygna and compare it with molecular and cloacal inspection techniques. In the four examined species, the White-faced Whistling Duck D. viduata, Fulvous Whistling Duck D. bicolor, Cuban Whistling Duck D. arborea and Red-billed Whistling Duck D. autumnalis, sexes are indistinguishable by appearance. However all the four species show strong sexual differences in the structure of their species-specific loud whistles. For 59 examined birds, an acoustic-based sexing showed 100% accordance to the DNA PCR analysis, while the cloacal inspection showed only 89.8% accuracy. The results demonstrate that acoustic sexing represents a feasible alternative to the two traditional methods as a noninvasive tool for the distant sexing of the four whistling duck species both in captivity and in the wild.  相似文献   
90.
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