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   22篇
  免费   0篇
林业   1篇
农学   1篇
  7篇
综合类   4篇
农作物   1篇
畜牧兽医   8篇
  2023年   1篇
  2020年   1篇
  2019年   1篇
  2014年   1篇
  2011年   3篇
  2010年   2篇
  2004年   2篇
  2002年   1篇
  2001年   2篇
  1983年   1篇
  1977年   1篇
  1976年   2篇
  1973年   1篇
  1971年   1篇
  1970年   1篇
  1966年   1篇
排序方式: 共有22条查询结果,搜索用时 244 毫秒
1.
2.
Internal organs of 74 racoon dogs originating from the eastern districts of the Federal Land Brandenburg were subjected to a complete helminthological dissection. In addition, samples of diaphragma muscles from 46 further animals were examined for Trichinella larvae. Altogether 3 trematode- (Alaria alata, Isthmiophora melis, Metorchis bilis), 3 cestode- (Mesocestoides sp., Echinococcus multilocularis, Taenia polyacantha) and 7 nematode species (Capillaria aerophila, C. plica, Trichinella spiralis, Uncinaria stenocephala, Molineus patens, Crenosoma vulpis, Toxocara canis) could be identified. Thereby, the racoon dog has a comparable helminth spectrum as well known in red foxes. Differences in the frequency of the occurrence of helminths in both hosts can be explained by different food preferences.  相似文献   
3.
4.
Calcium content in fruits of paprika, bean, quince and hip during fruit growth The Ca content and the Ca translocation into the fruits during their growth was determined in paprika and bean under controlled conditions (nutrient solution, growth room) and in quince and hip (Rosa rugosa Thumb.) under field conditions. Compared to leaves the Ca content in the fruits is very low in all 4 species and declines further during their growth. The K content, however, is similar in the leaves and in the fruits of all 4 species and remains nearly constant during fruit growth. The low Ca content of the fruits cannot directly be related to the cation exchange capacity (CEC) as there are no differences in the CEC between leaves and fruits. The generally low Ca content of the fruits and its decline during fruit growth is causally related in all 4 plant species to the low rate of Ca translocation compared to the rate of dry matter translocation into the fruits. There are, however, distinct differences between the 4 plant species in the course of the ratio Ca/dry matter translocation into the fruits: In paprika the Ca translocation into the fruits strongly declines during fruit growth and in bean the Ca translocation practically ceases with the onset of seed growth. In quince under field conditions the Ca translocation into the fruits rapidly declines at later stages and finally a translocation of Ca out of the fruit takes place (decrease in the amount of Ca/fruit). Only in hip the Ca translocation into the fruits remains constant during fruit growth. There is, however, a distinctly different distribution of Ca to the various parts within the hip fruits. The decline in Ca translocation during fruit growth can be explained in paprika and bean with a shift in water influx from the xylem (rich in Ca) to the phloem at the stage of high rates of dry matter influx into the fruit. In quince and hip, however, additional mechanisms (alternating water flux in the xylem, CEC) seem to be involved in the regulation of the Ca content of these fruits.  相似文献   
5.
Effect of Sodium Chloride and Mycostatin on the Mineral Content of Leaf Segments and on the Fine Structure of Chloroplasts Leaf segments of bean, barley and sugar beet were treated for several hours with 25 meq NaC1 or with the antibiotica mycostatin. The effect of these treatments on the content of potassium, sodium, calcium, magnesium and chloride in the leaf segments and on the fine structure of chloroplasts was studied. In bean sodium chloride treatment induced strong efflux of potassium and swelling of the chloroplasts. Sodium sulfate or mycostatin had the same effect. Despite of the strong efflux of potassium the content of calcium and magnesium in the segments was practically unaffected. Addition of 1 meq calcium to the external solution prevented the effect of sodium chloride on efflux of potassium as well as on the fine structure. In barley sodium chloride or mycostatin also induced efflux of potassium and swelling of the chloroplasts. These effects, however, were less pronounced than in bean. Again the content of calcium and magnesium in the segments was practically unaffected, and the addition of 1 meq calcium compensated the effect of sodium chloride. In sugar beet both mycostatin and sodium chloride did not induce efflux of potassium, despite of a strong influx of sodium in the sodium chloride treatment. In both treatments no change in the fine structure of the chloroplasts was observed. It was proved by isolation of chloroplasts that the typical sodium chloride induced differences in efflux of potassium from the leaf segments is also reflected in efflux of potassium from the chloroplasts. The results indicate the causative connection between efflux of potassium and change in the fine structure of the chloroplasts. Differences between the three plant species with respect to efflux of potassium induced by sodium chloride or mycostatin are reflections of different membrane properties. The presence of calcium in the external solution is much more important for the membrane stability of bean than it is for sugar beet e. g. The results obtained with leaf segments are a good reflection of the different tolerance of these three plant species to high sodium chloride concentrations under field conditions.  相似文献   
6.
7.
Most alpine ecosystem climate change studies identify changes in biota, several report abiotic factors and conditions, few report temperature changes, and few to none discuss growing degree days (GDD) changes. This study provides results of data analysis on changes in number of GDD in the alpine desert of the San Luis Valley (SLV) whose community is dominated by an irrigated agricultural region. Analysis indicates significant increases (p?<?0.05) in annual and growing season GDD10, GDD4.4 (potato), and GDD5.5 (alfalfa) during 1994–2007 compared to 1958–1993. With one exception, all stations experienced significant increases in mean annual daily GDD between 0.12 and 0.50 day?2 and growing season GDD day?2 0.21 and 0.81. Higher temperatures increase numbers of GDD, quickening growth of crops and maturity at the cost of reduced yield and quality. Increases in GDD indicate the Valley’s agricultural region and economy may experience negative impacts as yields decrease and water use increases.  相似文献   
8.
Late Pleistocene changes in oceanic primary productivity along the equator in the Indian and Pacific oceans are revealed by quantitative changes in nanoplankton communities preserved in nine deep-sea cores. We show that variations in equatorial productivity are primarily caused by glacial-interglacial variability and by precession-controlled changes in the east-west thermocline slope of the Indo-Pacific. The precession-controlled variations in productivity are linked to processes similar to the Southern Oscillation phenomenon, and they precede changes in the oxygen isotopic ratio, which indicates that they are not the result of ice sheet fluctuations. The 30,000-year spectral peak in the tropical Indo-Pacific Ocean productivity records is also present in the Antarctica atmospheric CO2 record, suggesting an important role for equatorial biological productivity in modifying atmospheric CO2.  相似文献   
9.
The reaction of decamethylsilicocene, (Me5C5)2Si, with the proton-transfer reagent Me5C5H2+B(C6F5)4- produces the salt (Me5C5)Si+ B(C6F5)4(2), which can be isolated as a colorless solid that is stable in the absence of air and moisture. The crystal structure reveals the presence of a cationic pi complex with an eta5-pentamethylcyclopentadienyl ligand bound to a bare silicon center. The 29Si nuclear magnetic resonance at very high field (delta = - 400.2 parts per million) is typical of a pi complex of divalent silicon. The (eta5-Me5C5)Si+ cation in 2 can be regarded as the "resting state" of a silyliumylidene-type (eta1-Me5C5)Si+ cation. The availability of 2 opens new synthetic avenues in organosilicon chemistry. For example, 2 reacted with lithium bis(trimethylsilyl)amide to give the disilene E-[(eta1-Me5C5)[N(SiMe3)2]Si]2(3).  相似文献   
10.
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