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   60篇
  免费   1篇
  2020年   2篇
  2019年   2篇
  2018年   1篇
  2017年   1篇
  2015年   1篇
  2014年   5篇
  2013年   2篇
  2012年   1篇
  2011年   3篇
  2010年   2篇
  2009年   4篇
  2008年   3篇
  2007年   5篇
  2006年   2篇
  2005年   1篇
  2004年   4篇
  2003年   2篇
  2002年   2篇
  2001年   2篇
  1999年   1篇
  1998年   1篇
  1996年   1篇
  1994年   2篇
  1992年   2篇
  1991年   1篇
  1989年   1篇
  1988年   1篇
  1987年   2篇
  1985年   1篇
  1983年   1篇
  1981年   1篇
  1977年   1篇
排序方式: 共有61条查询结果,搜索用时 15 毫秒
31.
《Phytomedicine》2014,21(11):1349-1355
The present study investigated the effects of repeated administration of Korodin®, a combination of camphor and crataegus berry extract, on blood pressure and attentional functioning. This study was conducted based on a randomized, placebo-controlled, double-blind design. 54 persons participated (33 female, 21 male) with a mean age of 24.3 years. Blood pressure and body mass index were in the normal range. Participants received 20 drops of either Korodin® or a placebo for four times with interjacent time intervals of about 10 min. Blood pressure was measured sphygmomanometrically before and after each administration. Attentional performance was quantified by using two paper-and-pencil tests, the d2 Test of Attention and Digit Symbol Test.Greater increases in blood pressure occurred after the four Korodin® administrations in comparison to the four placebo administrations. The performance in two parameters of d2 Test of Attention was consistently superior after the intake of Korodin®. The excellent tolerability and safety of Korodin®, even after a total consumption of 80 drops, was confirmed.  相似文献   
32.
33.
Apomixis in Crataegus is primarily aposporous and requires pollination. The embryo sac is of the Polygonum type. A combination of meiotically unreduced embryo sacs with apparently reduced pollen would violate the usual requirement for a 2 : 1 ratio of maternal to paternal contributions to the endosperm. We therefore investigated the origin of endosperm in seeds of sexual diploids and apomictic polyploids of the sister genera Crataegus and Mespilus. Flow-cytometric DNA measurements from embryo and endosperm in mature seeds were converted to ploidy levels using leaf-tissue information. The diploids had triploid endosperm. In c. 60% of seed from polyploids, one sperm apparently contributes to the endosperm, while 25% or more may involve two sperm. Additional results suggest that trinucleate central cells also occur. Fertilization of meiotically unreduced eggs is indicated. The ratio of maternal to paternal contributions to the endosperm in these apomictic Crataegus is not constrained to 2 : 1. They thus resemble some Sorbus (Pyreae) and very distantly related Ranunculus (Ranunculaceae). It is suggested that Paspalum (Poaceae) may have similarly flexible endosperm ploidy levels.  相似文献   
34.
The chemotaxonomic investigation of Crataegus x macrocarpa, a hybrid of C. laevigata and C. rhipidophylla, presents the qualitative and quantitative composition of its flavonoid pattern in relationship to its parent species for the first time. Six flavonoids were identified as vitexin-2'-O-rhamnoside (1), vitexin (2), isovitexin (3), rutin (4), hyperoside (5), and isoquercitrin (6). Furthermore, two flavonoids were isolated from C. x macrocarpa and identified as a diastereoisomeric mixture of (R)- and (S)-eriodictyol-7-O-beta-D-glucuronide (7) and luteolin-7-O-beta-D-glucuronide (8) by means of 1D- and 2D-NMR, MS, and UV experiments. Compounds 7 and 8 were isolated for the first time from Crataegus species. While missing in C. laevigata, their occurrence in C. rhipidophylla additionally emphasizes its chemotaxonomic relationship to C. x macrocarpa.  相似文献   
35.
WS(?) 1442 is a special extract of hawthorn leaves with flowers used for the treatment of mild cardiac failure. The activation of endothelial nitric oxide synthase (eNOS) has been shown to contribute to its vasodilating properties. Quite recently it has been demonstrated that red blood cells (RBCs) express a functional NO-synthase (rbcNOS) and rbcNOS activation has been associated with increased RBC deformability. The aim of the present study was to determine whether WS(?) 1442 is able to activate rbcNOS, to induce NO-formation in RBC and to alter RBC-deformability. Blood from healthy volunteers was incubated with WS(?) 1442 (25-100 μg/ml) for up to 30 min. RbcNOS activation was detected by immunohistochemical staining of phosphorylated rbcNOS and NO-formation was examined by diaminofluorescein (DAF) fluorescence. RBC deformability was measured by a laser assisted optical rotational cell analyzer. Serine 1177 of RbcNOS (rbcNOS Ser(1177)) was time- and concentration-dependently phosphorylated by WS(?) 1442. Rates of rbcNOS Ser(1177) phosphorylation were up to 149% higher in RBCs treated with WS(?) 1442 in comparison to control (DMSO 0.05%). WS(?) 1442 induced a time-dependent increase in NO-formation in RBCs which reached its maximum after 5 min. An increase in shear stress (0.3-50 Pa) caused an increase in RBC deformability. WS(?) 1442 did not change either basal or maximal RBC-deformability or shear stress sensitivity of RBC at normoxia. CONCLUSION: WS(?) 1442 activates rbcNOS and causes NO-formation in RBCs. WS(?) 1442-dependent NO-formation however does not affect RBC-deformability at normoxia.  相似文献   
36.
Hawthorn ( Crataegus spp.) has a long history as an ornamental and a source of medicine. We report the use of random amplified polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR) markers to determine genetic relationships in the genus Crataegus . Twenty-eight accessions, including eight species ( Crataegus pinnatifida , Crataegus bretschneideri , Crataegus maximowiczii , Crataegus kansuensis , Crataegus altaica , Crataegus songarica , Crataegus dahurica and Crataegus sanguinea ) and two botanical varieties ( C. pinnatifida var. major and C. maximowiczii var. ninganensis ) were analysed. Twelve RAPD primers reproducibly and strongly amplified 128 fragments of which 116 were polymorphic; similarly, 13 ISSR primers generated 127 products of which 119 were polymorphic. Dendrograms based on unweighted pair group method with arithmetic average analysis were constructed from both the RAPD and the ISSR data. Similarity coefficient based on RAPD and ISSR markers ranged from 0.22 to 0.98 and 0.23 to 0.98, respectively. The range in similarity coefficient indicated that the genus has a high level of genetic diversity. The Mantel test on the similarity matrices produced by RAPD and ISSR markers gave r  = 0.86, showing high correlation between RAPD and ISSR markers in their ability to detect genetic relationships between Crataegus accessions. RAPD and ISSR appear to be reliable methods for the analysis of genetic relationships among hawthorns.  相似文献   
37.
研究盐胁迫下外源葡萄糖对山楂叶中光系统II(PSII)光化学活性影响的结果表明,盐胁迫下,浇灌外源葡萄糖可增加山楂幼苗叶中PSII最大光化学效率(Fv/Fm)、暗适应后PSII最大光化学效率(ΦPo)、捕获的激子将电子传递到电子传递链中QA-下游的其它电子受体的概率(Ψo)及反应中心吸收的光能用于电子传递的量子产额(ΦEo),降低照光2ms时反应中心的关闭程度(Vj)和单位反应中心吸收的能量(ABS/RC),提高电子转运效率(ETo/RC),降低放氧复合体(OEC)受伤害的程度。  相似文献   
38.
The possibilities and limitations of supercritical fluid extraction of natural products of low, medium and high polarity under very high pressure and with polar modifiers has been investigated. The medicinal herbs marigold (Calendula officinalis), hawthorn (Crataegus sp.) and chamomile (Matricaria recutita) were used as models in this study. Extraction profiles and the spectra of extractable metabolites were recorded following extraction with mixtures of carbon dioxide:ethanol of varying proportions (0-20% ethanol) and at various pressures in the range 300-689 bar. Components were identified by HPLC-PAD-MS or GC-MS and quantified by HPLC or GC as appropriate. Extraction yields under the varying conditions depended to a large extent on the profiles of secondary metabolites present in the three drugs. Whereas the extractability of lipophilic compounds increased substantially at pressures above 300 bar, the yields of polyphenolic and glycosidic compounds remained low even at 689 bar and with 20% modifier in the extraction fluid.  相似文献   
39.
用成年云南山楂Crataegus scabrifolia(Franch)Rehd.树的无菌增殖芽苗作为生根试验材料。结果表明:接种在含生长素(IBA、NAA)0.01—1.0mg/l的MS/2培养基中,芽苗的平均生根率为50.4%;在高浓度(150—250mg/l)生长素溶液中浸泡芽苗基部30分钟,然后接种到无生长素的MS/2培养基中,其生根率为60.1%;用高浓度生长素液蘸芽苗基部的生根率为83.5%;芽苗在含IBA 1—5mg/l的培养基中培养2—4天,然后转入MS/2培养基中诱导生根,生根率可达92%以上,根伸长正常。黑暗条件明显抑制生根,每日16小时至24小时光照对芽苗生根有益。  相似文献   
40.
Crataegus section Douglasii exhibits variation in stamen number per flower typical for the genus throughout North America. To understand the developmental basis for this variation we studied the early floral ontogeny of the three taxa in section Douglasii: C. douglasii (both Pacific northwest and the upper Great Lakes basin), C. rivularis, and C. suksdorfii. Crataegus suksdorfii, like all known diploid Crataegus, has ≈20 stamens; the two other taxa have ≈10 stamens, a condition associated only with polyploidy. In all taxa petal primordia and a whorl of five pairs of stamen primordia develop from five common primordia. The 10-stamen∗∗∗ condition results from loss of two whorls of five stamens that are subsequently formed in C. suksdorfii. Loss of these two whorls in the 10-stamen taxa is the result of neither a smaller floral apex at initiation, nor a smaller flower at anthesis. Stamen number variability, particularly in C. douglasii and C. rivularis, is the result predominantly of fewer than two stamen primordia developing between adjacent petal primordia. Pollen production in C. douglasii is half that in C. suksdorfii because of the reduction in stamen number. The results are presented and discussed in terms of morphogenetic explanations of meristic variation.  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