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101.
Repeated epilation (Er) is a radiation-induced, autosomal, incomplete dominant mutation in mice which is expressed in heterozygotes but is lethal in the homozygous condition. Many effects of the mutation occur in skin: the epidermis in Er/Er mice is adhesive (oral and nasal orifices fuse, limbs adhere to the body wall), hyperplastic, and fails to undergo terminal differentiation. Skin from fetal +/+, Er/+ and Er/Er mice at ages pre- and postkeratinization examined by light, scanning, and transmission electron microscopy showed marked abnormalities in tissue architecture, differentiation, and cell structure; light and dark basal epidermal cells were separated by wide intercellular spaces, joined by few desmosomes, and contained phagolysomes. The numbers of spinous, granular, and superficial layers were highly variable within any given region and among various regions of the body. In some areas, 2-8 layers of granular cells, containing large or diminutive keratohyalin granules, extended to the epidermal surface; in others, the granular layers were covered by several layers of partially keratinized or nonkeratinized cells. In rare instances, a single or small group of cornified cells was present among the granular layers but was not associated with the epidermal surface. Both the granular and nonkeratinized/partially keratinized upper epidermal layers Er/Er skin gave positive immunofluorescence with antiserum to the histidine-rich, basic protein, filaggrin. Proteins in epidermal extracts from +/+, Er/+ and Er/Er mice were separated and identified by radio- and immunolabeling techniques. The Er/Er extract was missing a 26.5- kdalton protein and had an altered ratio of bands in the keratin region. The 26.5-kdalton band was histidine-rich and cross-reacted with the antiserum to rat filaggrin. Several high molecular weight bands present in both Er/Er and +/+ extracts also reacted with the antiserum. These are presumed to be the precursors of filaggrin and to account for the immunofluorescence om Er/Er epidermis even though the product protein is absent. The morphologic and biochemical data indicated that the genetic defect has a general and profound influence on epidermal differentiation, including alteration of two proteins (filaggrin and keratin) important in normal terminal differentiation, tissue architecture, and cytology. Identification of epidermal abnormalities at early stages of development (prekeratinization) and defective structure of other tissues and gross anatomy suggest that the mutation is responsible for a defect in same regulatory step important in many processes of differentiation and development. 相似文献
102.
A photoperiodically-controlled diapause of the long-day, short-day type was identified in a brown-winged, yellow-eyed strain of Ephestia cautella (Walker). The proportion of larvae diapausing in very long photoperiods was less than in short photoperiods. The mean critical photoperiod, here defined as that photoperiod giving half the maximum percentage of insects that diapause in response to photoperiod at a given temperature, was between 12 and 13 hr for the long-day reaction at both 20 and 25°C. The principal sensitive phase occurred near the time of the last larval moult. The mean duration of diapause was 2–3 months at 20°C and slightly longer at 25°C. The optimum temperature for diapause development was near 15°C, all larvae pupating within 24 days after a 45-day exposure at this temperature. Diapause could be terminated whenever larvae diapausing at 20°C were exposed to as few as five long (15 hr) photoperiods at 25°C. Long photoperiods at 20°C, or short photoperiods (9 hr) at 25°C were less effective in terminating diapause. 相似文献
103.
H. Brittain-Loucas S. R. Bowley B. D. McKersie 《In vitro cellular & developmental biology. Plant》1998,34(4):281-284
Summary The effects of callus inoculation concentration and culture duration on somatic embryogenesis of orchardgrass,Dactylis glomerata L., were evaluated in suspension cultures of an embryogenic genotype Embryogen-P. Somatic embryo formation was induced in
liquid SH medium containing 30 μM dicamba (SH-30 and 1.5% casein hydrolysate; embryo development was in liquid SH medium without plant growth regulators (SH-0);
and embryo maturation and germination occurred on solid SH-0 medium. Callus proliferation in SH-30 suspension cultures was
greatest when callus was inoculated into the liquid medium at a relatively high concentration of 4% (4 g callus/100 ml medium),
but the induction of somatic embryos was highest in this medium if the callus was inoculated at a lower concentration (<2%).
In a second experiment, somatic embryo yield was highest when SH-0 development medium was inoculated with suspension culture
callus at 0.1% concentration and declined markedly as inoculation concentration increased. Cell concentration is a critical
factor in regulating the somatic embryogenesis response in orchardgrass suspension cultures. 相似文献
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107.
苜蓿核糖体基因物理定位及染色体荧光分带 总被引:5,自引:0,他引:5
利用核糖体基因为探针对,二倍体和四倍体苜蓿(Medicago sativa)进行原位杂交,结果表明,45s在四倍体、二倍体种中总是以单位点位于核仁组织区,5s则有2~3个位点;以二倍体种的基因组DNA为探针的原位杂交表明,蓝花苜蓿(M.coerulea)和黄花苜蓿(M.falcata)均能与四倍体染色体进行杂交,仅杂交信号强弱的染色体数目有差别;荧光染料DAPI使苜蓿的染色体显示带纹,蓝花苜蓿的DAPI带与C-带基本一致.文章对四倍体苜蓿的可能来源进行了讨论. 相似文献
108.
Pyramiding Mn-superoxide dismutase transgenes to improve persistence and biomass production in alfalfa 总被引:19,自引:0,他引:19
Expression of individual superoxide dismutase (SOD) transgenes improves environmental stress tolerance and biomass production in alfalfa (Medicago sativa L.). The objective of this study was to test the hypothesis that synergy exists between transgenic SOD stress-tolerance mechanisms, specifically that the simultaneous expression of two SOD transgenes confers greater benefit than the expression of a single SOD transgene. The hypothesis was tested through an evaluation of an F(1) family generated through a sexual cross of a hemizygous Mit-MnSOD plant and a hemizygous Chl-MnSOD-transgenic alfalfa plant which had previously been screened in field trials for improved persistence. Southern analyses revealed that the parents each had single insertion regions of the MnSOD cDNA and the inheritance followed the expected Mendelian ratios. Native PAGE gels and enzyme inhibition assays revealed the activity of the transgenic MnSOD isozymes. F(1) progeny containing either the Mit-MnSOD or the Chl-MnSOD transgene had significantly higher storage organ (crown+root) biomass compared to non-transgenic siblings. The joint expression of the transgenes resulted in a numerical increase in total SOD activity. However, F(1) progeny containing both transgenes had lower shoot and storage organ biomass compared to siblings having only one or the other transgene, a result that did not support the authors' hypothesis. It was postulated that a promoter with lower expression than 35S may be necessary if closely related transgenes are to be pyramided in the same plant. 相似文献
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Kavish J Bhansing Martin Lammens Hanneke KA Knaapen Piet LCM van Riel Baziel GM van Engelen Madelon C Vonk 《Arthritis research & therapy》2014,16(3):R111