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   161篇
  免费   22篇
林业   7篇
农学   25篇
  9篇
综合类   22篇
农作物   5篇
水产渔业   4篇
畜牧兽医   94篇
园艺   6篇
植物保护   11篇
  2023年   2篇
  2022年   2篇
  2020年   2篇
  2019年   5篇
  2018年   8篇
  2017年   5篇
  2016年   7篇
  2015年   9篇
  2014年   4篇
  2013年   14篇
  2012年   8篇
  2011年   7篇
  2010年   10篇
  2009年   6篇
  2008年   4篇
  2007年   6篇
  2006年   4篇
  2005年   3篇
  2004年   4篇
  2003年   8篇
  2001年   2篇
  2000年   3篇
  1999年   3篇
  1998年   9篇
  1997年   3篇
  1996年   2篇
  1993年   4篇
  1991年   2篇
  1990年   2篇
  1986年   1篇
  1985年   1篇
  1984年   1篇
  1983年   1篇
  1980年   1篇
  1979年   2篇
  1978年   2篇
  1976年   1篇
  1975年   1篇
  1974年   1篇
  1973年   2篇
  1972年   1篇
  1971年   1篇
  1970年   3篇
  1969年   4篇
  1968年   2篇
  1967年   2篇
  1966年   1篇
  1965年   1篇
  1963年   1篇
  1924年   1篇
排序方式: 共有183条查询结果,搜索用时 31 毫秒
71.
Saponins are one of the components present in the soybean seeds that have various functional properties. The chemical structures and concentration of soyasaponins affect the taste of the processed soyfood, thereby limiting its industrial applications. Therefore, it is important to understand saponin biosynthesis to explore natural and artificial variation in the saponin components, which can be modified to suit its application. The objective of the present study was to identify and characterize an EMS-induced soybean mutant with an altered saponin composition from a pool of 892 M4 lines. The mutant PE1905 showed an increased content of saponin Af (336.0%). The content of saponin Ab, DDMP-αg, and DDMP-βg was decreased in the mutant PE1905 by 89.3, 24.8, and 63.1%, respectively compared to the wild-type Pungsannamul. Additionally, four new components were detected in the mutant PE1905 that were absent in the wild type. Of these, the compound 4 (designated as Ab-δ) had the highest concentration, and therefore it was further characterized by HPLC and LC-PDA/MS/MS analysis to know the chemical structure, and molecular weight and formula. Considering these details, along with the alterations in the saponin Af and Ab concentrations, it was presumed that the Ab-δ acts as a precursor for the synthesis of saponin Af and Ab. Thus, we predicted a biosynthetic pathway from the Ab-δ to Ab saponin. The inheritance analysis showed that the concentration of saponin Ab-δ is controlled by a single recessive gene in the mutant PE1905. The results from the present study would be helpful in understanding the mechanisms behind altered seed saponin composition in soybeans.  相似文献   
72.
73.
In spite of widespread application of flutamide in the endocrine therapies of young and adult patients, the side effects of this antiandrogen on spermatogenesis and germ‐cell morphology remain unclear. This study evaluates the short‐term androgen blockage effect induced by the administration of flutamide to the testes of pubertal (30‐day old) and adult (65‐ and 135‐day old) guinea pigs, with an emphasis on ultrastructural alterations of main cell types. The testes removed after 10 days of treatment with either a non‐steroidal antiandrogen, flutamide (10 mg/kg of body weight) or a pharmacological vehicle alone were processed for histological, quantitative and ultrastructural analysis. In pubertal animals, flutamide androgenic blockage induces spermatogonial differentiation and accelerates testes maturation, causing degeneration and detachment of primary spermatocytes and round spermatids, which are subsequently found in great quantities in the epididymis caput. In post‐pubertal and adult guinea pigs, in addition to causing germ‐cell degeneration, especially in primary spermatocytes, and leading to the premature detachment of spherical spermatids, the antiandrogen treatment increased the relative volume of Leydig cells. In addition, ultrastructural evaluation indicated that irrespective of age antiandrogen treatment causes an increase in frequency of organelles involved with steroid hormone synthesis in the Leydig cells and a dramatic accumulation of myelin figures in their cytoplasm and, to a larger degree, in Sertoli cells. In conclusion, the transient exposition of the guinea pigs to flutamide, at all postnatal ages causes some degenerative lesions including severe premature detachment of spermatids and accumulation of myelin bodies in Leydig and Sertoli cells, compromising, at least temporarily, the spermatogenesis.  相似文献   
74.
75.
Lasing action in organic vertical-cavity surface-emitting laser (OVCSEL) structures is demonstrated. Optically pumped OVCSELs with an active layer composed of a thin-film organic semiconductor tris-(8-hydroxyquinoline) aluminum (Alq3) doped with DCM laser dye produced very narrow linewidth (0.2 +/- 0.1 angstrom), high-power (3 watts) emission that could be varied in different devices from orange to red. The efficient energy transfer from Alq3 to DCM results in a threshold input energy of 300 microjoules per square centimeter. An operational lifetime >10(6) laser pulses was achieved for a device operated well above threshold in atmosphere. The linewidths above threshold are Fourier transform-limited and could potentially be narrowed further.  相似文献   
76.
A cluster analysis of the stratigraphic distribution of all Ordovician trilobite families, based on a comprehensive taxonomic database, identified two major faunas with disjunct temporal diversity trends. The Ibex Fauna behaved as a cohort, declining through the Ordovician and disappearing at the end-Ordovician mass extinction. In contrast, the Whiterock Fauna radiated rapidly during the Middle Ordovician and gave rise to all post-Ordovician trilobite diversity. Its pattern of diversification matches that of the Paleozoic Evolutionary Fauna; hence, trilobites were active participants in the great Ordovician radiations. Extinction patterns at the end of the Ordovician are related to clade size: Surviving trilobite families show higher genus diversity than extinguished families.  相似文献   
77.
78.
SUMMARY Two field trials using an injectable vitamin A, D and E solution conducted in the pastoral environment of northern Australia are described. It was found that treatment of lighter (< 150 kg) or heavier (> 372 kg) weight cattle did not reduce weight loss during road transport. These findings contradict anecdotal evidence of reduced weight loss during transport with the use of vitamins A, D and E. The lack of scientific basis for their use is discussed.  相似文献   
79.
80.
Objective To investigate causes of ill health and mortality in juvenile wild green sea turtles ( Chelonia mydas ) found along the mid-north west coast of Western Australia between June and October of 1997.
Procedure Department of Conservation and Land Management rangers submitted four dead or dying green sea turtles from separate incidents for veterinary examination, necropsy, and bacteriological, parasitological and histopatho-logical examination.
Results Numerous different species of trematodes belonging to the families Pronocephalidae, Microscaphidiidae and Paramphistomidae were detected in the intestines of two turtles examined, and in all turtles there was severe spirorchid fluke infection including Haemoxenicon sp, Amphiorchis sp and Hapalotrema sp. Histopathological examination demonstrated severe multifocal to diffuse granulomatous vasculitis, aggregations of spirorchid fluke eggs and microabscesses throughout various tissues including intestines, kidney, liver, lung and brain. Cultures and or histopathological examination demonstrated disseminated Gram-negative bacterial infections including salmonella, E coli , Citrobacter freundii and Moraxella sp.
Conclusion Infections caused by salmonellae, E coli and other Gram-negative bacteria should be considered as causes of systemic illness and death in wild green sea turtles infected with spirorchid cardiovascular flukes and other internal parasites.  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