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   166篇
  免费   5篇
  171篇
  2023年   1篇
  2021年   4篇
  2020年   1篇
  2018年   2篇
  2017年   5篇
  2016年   4篇
  2015年   3篇
  2014年   3篇
  2013年   6篇
  2012年   6篇
  2011年   9篇
  2010年   10篇
  2009年   11篇
  2008年   9篇
  2007年   6篇
  2006年   8篇
  2005年   9篇
  2004年   8篇
  2003年   3篇
  2002年   4篇
  2001年   3篇
  2000年   1篇
  1999年   4篇
  1998年   4篇
  1997年   2篇
  1996年   1篇
  1995年   2篇
  1994年   1篇
  1992年   2篇
  1991年   2篇
  1989年   3篇
  1988年   5篇
  1987年   2篇
  1986年   3篇
  1985年   1篇
  1984年   1篇
  1983年   3篇
  1980年   2篇
  1979年   2篇
  1978年   3篇
  1977年   4篇
  1976年   2篇
  1975年   2篇
  1971年   1篇
  1970年   1篇
  1967年   2篇
排序方式: 共有171条查询结果,搜索用时 0 毫秒
31.
The usefulness of quantum dots for the immunofluorescent detection of surface antigens on the lymphoid cells has been studied. To optimize quantum dots detection we have upgraded fluorescent microscope that allows obtaining multiple images from different quantum dots from one section. Specimens stained with quantum dots remained stable over two weeks and practically did not bleach under mercury lamp illumination during tens of minutes. Direct conjugates of primary mouse monoclonal antibodies with quantum dots demonstrated high specificity and sufficient sensitivity in the case of double staining on the frozen sections. Because of the high stability of quantum dots' fluorescence, this method allows to analyze antigen coexpression on the lymphoid tissue sections for diagnostic purposes. The spillover of fluorescent signals from quantum dots into adjacent fluorescent channels, with maxima differing by 40 nm, did not exceed 8%, which makes the spectral compensation is practically unnecessary.  相似文献   
32.
The results of the experimental investigation on 15 rabbits are presented here. Hypoglycemic action of the standard exogenic insulin dose strengthened after performing transcerebral lateral electrostimulation on the right side with the weak current impulse.  相似文献   
33.
The location of major quantitative trait loci (QTL) contributing to stem and leaf [Na+] and [K+] was previously reported in chromosome 7 using two connected populations of recombinant inbred lines (RILs) of tomato. HKT1;1 and HKT1;2, two tomato Na+‐selective class I‐HKT transporters, were found to be closely linked, where the maximum logarithm of odds (LOD) score for these QTLs located. When a chromosome 7 linkage map based on 278 single‐nucleotide polymorphisms (SNPs) was used, the maximum LOD score position was only 35 kb from HKT1;1 and HKT1;2. Their expression patterns and phenotypic effects were further investigated in two near‐isogenic lines (NILs): 157‐14 (double homozygote for the cheesmaniae alleles) and 157‐17 (double homozygote for the lycopersicum alleles). The expression pattern for the HKT1;1 and HKT1;2 alleles was complex, possibly because of differences in their promoter sequences. High salinity had very little effect on root dry and fresh weight and consequently on the plant dry weight of NIL 157‐14 in comparison with 157‐17. A significant difference between NILs was also found for [K+] and the [Na+]/[K+] ratio in leaf and stem but not for [Na+] arising a disagreement with the corresponding RIL population. Their association with leaf [Na+] and salt tolerance in tomato is also discussed.  相似文献   
34.
A concentrate with the antimicrobial activity has been isolated from the culture broth of Streptomyces roseoflavus INA-Ac-5812. Its further fractionation by reversed-phase HPLC has resulted in six fractions. It has been established by MALDI-TOF and ESI-MSn precision mass-spectrometry methods that the main components of the complex antibiotic are several closely related compounds, presumably of a glycopeptide nature. The fraction containing an individual component with a mass of 1845.788 Da has been characterized by UV/Vis absorbance and fluorescence spectra, amino acid analysis, and derivatization with tris(2,6-dimethoxyphenyl)methyl cation. The activity of fractions against pathogenic microbes has been studied. The results allow the supposition that the INA-5812 antibiotic complex is a glyco- or lipoglycopeptide antibiotic of a new type, which is very promising for further study.  相似文献   
35.
36.
Survival typically contributes most to population trends in long‐lived birds and its accurate estimation is therefore vital for population management and conservation. We evaluated the effects of age, territoriality and reproduction on survival in Bonelli’s Eagle Aquila fasciata through multistate capture‐mark‐recapture analyses on a long‐term dataset. Monitoring was carried out in southeast France (1990–2008) and involved the surveying of territorial Eagles, the marking of fledged chicks, and the recording of resightings and recoveries of marked non‐territorial and territorial birds. Survival improved with age, but territoriality was not retained in the best model; yearly survival was estimated at 0.479 for fledglings (to 1 year of age), 0.570 for 1‐ and 2‐year‐olds, and 0.870 for 3‐year‐old and older individuals. The second best model supported a further increase in survival from 3‐year‐olds (0.821) to older individuals (0.880). In the third best supported model, territoriality enhanced survival, but only in 2‐year‐olds (0.632 vs. 0.562 for non‐territorial). We found no correlation between the previous breeding stage and future survival, consistent with the long lifespan of the study species. Nevertheless, 4‐year‐old and older successful breeders were more likely to breed the following year than failed adult breeders (0.869 vs. 0.582), suggesting that the cost of reproduction is small in comparison with the variation in quality among individuals or their territories.  相似文献   
37.
The history of some invasive species is so complex that their origins can be difficult to determine. One example of such invasive species is the California invasive known as “wild artichoke thistle” (Cynara cardunculus var. sylvestris), found in natural and disturbed ecosystems. Wild artichoke thistle is a Mediterranean native and the progenitor of two domesticated horticultural taxa, artichoke and cardoon. Different hypotheses regarding the origins of California plants have included introductions by 19th century Italian immigrants and the de-domestication (evolutionary reversion to wild-type morphology) of feral (escaped, free-living) cultivars. Using microsatellite markers, we compared the genetic constitutions of 12 artichoke thistle populations in California with possible progenitor populations: 17 Spanish and Italian wild populations and eight different artichoke and cardoon cultivars. Each California population was compared with its putative progenitors using STRUCTURE analysis. Our results suggest that California's artichoke thistle populations are polyphyletic. Surprisingly, two-thirds of California's populations closely matched populations from the Iberian Peninsula. Three populations matched domesticated artichoke. One population appears to have wild and cultivar hybrid ancestry. Alleles specific to Italian populations were found at low frequencies in some California plants, suggesting that Italian wild plants may have been in California, but have left a trivial genetic legacy. Given that the de-domesticated plants in this study appear to be as invasive as the wild taxon, we conclude with a discussion of the role that ferality and de-domestication may have in plant invasions.  相似文献   
38.
The species related to Vriesea paraibica (Bromeliaceae, Tillandsioideae) have controversial taxonomic limits. For several decades, this group has been identified in herbarium collections as V. × morreniana, an artificial hybrid that does not grow in natural habitats. The aim of this study was to assess the morphological variation in the V. paraibica complex through morphometric analyses of natural populations. Two sets of analyses were performed: the first involved six natural populations (G1) and the second was carried out on taxa that emerged from the first analysis, but using material from herbarium collections (G2). Univariate ANOVA was used, as well as discriminant analysis of 16 morphometric variables in G1 and 18 in G2. The results of the analyses of the two groups were similar and led to the selection of diagnostic traits of four species. Lengths of the lower and median floral bracts were significant for the separation of red and yellow floral bracts. Vriesea paraibica and V. interrogatoria have red bracts; these two species are differentiated by the widths of the lower and median portions of the inflorescence and by scape length. These structures are larger in the former and smaller in the latter. Of the species with yellow floral bracts, V. eltoniana is distinguished by longer leaf blades and scapes and V. flava is characterized by its shorter sepal lengths. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 159 , 163–181.  相似文献   
39.
A new filamentous cyanobacterial strain BAC 9610 was isolated from the lake Baikal pelagial. Data obtained by light, scanning, and transmission electron microscopy, along with 16S rRNA gene sequence analysis, allowed the bacterium identification as Trichormus variabilis, previously known as Anabaena variabilis. Trichormus is a cyanobacterial genus not presented in the list of Baikal plankton algae; A. variabilis also hasn’t been previously detected in Baikal phytoplankton. T. variabilis nitrogen fixation ability was demonstrated. The gene responsible for nitrogen fixation, nifH, was identified by PCR and was partially sequenced. No hepatotoxin synthesis genes were revealed in the strain.  相似文献   
40.
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