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   118篇
  免费   5篇
林业   7篇
农学   4篇
  31篇
综合类   12篇
农作物   2篇
水产渔业   15篇
畜牧兽医   48篇
植物保护   4篇
  2022年   2篇
  2021年   4篇
  2020年   2篇
  2019年   5篇
  2018年   2篇
  2017年   5篇
  2015年   1篇
  2014年   4篇
  2013年   11篇
  2012年   7篇
  2011年   7篇
  2010年   2篇
  2009年   6篇
  2008年   9篇
  2007年   9篇
  2006年   2篇
  2005年   4篇
  2004年   5篇
  2003年   6篇
  2002年   3篇
  2001年   4篇
  2000年   2篇
  1999年   4篇
  1998年   1篇
  1996年   1篇
  1993年   3篇
  1992年   1篇
  1990年   1篇
  1989年   1篇
  1986年   1篇
  1984年   1篇
  1980年   1篇
  1978年   1篇
  1977年   1篇
  1974年   2篇
  1971年   1篇
  1962年   1篇
排序方式: 共有123条查询结果,搜索用时 15 毫秒
71.
72.
73.
Magnetic resonance imaging was used to identify a spinal mass at the level of the 6th-7th cervical vertebral body in a cat. The MRI images were most consistent with the presence of an intradural, extramedullary meningioma that was confirmed by subsequent histological examination.  相似文献   
74.
The chemical composition of silage consumed by cattle can influence the subsequent rumen microbial fermentation patterns and methane (CH4) emissions. The objectives of this study were to (i) evaluate the effect of ensilage on the in vitro rumen methane output of perennial ryegrass and (ii) relate the silage fermentation characteristics of grass silages with in vitro rumen methanogenesis. Three pre‐harvest herbage‐conditioning treatments and seven silage‐additive treatments were used in a laboratory‐scale silo experiment to produce a diversity of silage fermentation characteristics. Ensilage reduced (< 0·01) the in vitro rumen CH4 output (mL CHg?1 dry matter (DM) disappeared). This reflected differences in the direction of rumen fermentation (lower acetic (< 0·05) and higher propionic (< 0·001) acid proportions in volatile fatty acids) rather than major changes in the extent of in vitro rumen fermentation (i.e. mmol VFA g?1 DM). The magnitude of the decrease in CH4 output (mL g?1 DM incubated) owing to ensilage increased as the extent of silage fermentation, and in particular the lactic acid concentration, increased. In contrast, among silages with relatively similar extents of silage fermentation (i.e. total fermentation products), an increase in the proportion of lactic acid in silage fermentation products led to a more extensive in vitro rumen fermentation and thus to a greater CH4 output (mL g?1 DM).  相似文献   
75.
Yarrowia lipolytica is a dimorphic yeast able to secrete different types of proteases depending on the pH of the environment. At neutral pH, the production of an extracellular alkaline protease (AEP) is induced. This protease could be useful in the leather, detergent, or food industries. The XPR2 gene, coding for AEP, was extracted from the pINA154 vector and cloned into the pHIL-D2 vector to obtain a new protease-producing recombinant Pichia pastoris strain. The gene was efficiently integrated in the P. pastoris genome and expressed from the AOX1 promoter actively induced by methanol. Finally, the protease was successfully secreted by P. pastoris GS115.  相似文献   
76.
OBJECTIVES: To determine the differences in macronutrient and food group contribution to total food and energy intakes between Estonian and Swedish under-, normal- and overweight schoolchildren, and to estimate the association between diet and body mass index (BMI). DESIGN: Cross-sectional comparison between Estonian and Swedish children and adolescents of different BMI groups. SETTING: Twenty-five schools from one region in Estonia and 42 in two regions of central Sweden. SUBJECTS: In total 2308 participants (1176 from Estonia and 1132 from Sweden), including 1141 children with a mean age of 9.6 +/- 0.5 years and 1167 adolescents with a mean age of 15.5 +/- 0.6 years. RESULTS: Overweight was more prevalent among younger girls in Sweden (17.0 vs. 8.9%) and underweight among girls of both age groups in Estonia (7.9 vs. 3.5% in younger and 10.5 vs. 5.1% in older age group of girls). Compared with that of normal- and underweight peers, the diet of overweight Estonian children contained more energy as fat (36.8 vs. 31.7%) but less as carbohydrates, and they consumed more milk and meat products. Absolute BMI of Estonian participants was associated positively with energy consumption from eggs and negatively with energy consumption from sweets and sugar. Swedish overweight adolescents tended to consume more energy from protein and milk products. Risk of being overweight was positively associated with total energy intake and energy from fish or meat products. In both countries the association of overweight and biological factors (pubertal maturation, parental BMI) was stronger than with diet. CONCLUSION: The finding that differences in dietary intake between under-, normal- and overweight schoolchildren are country-specific suggests that local dietary habits should be considered in intervention projects addressing overweight.  相似文献   
77.
OBJECTIVE: To analyse the association between macronutrient intake and body mass index (BMI). DESIGN: A series of hospital-based case-control studies. SETTINGS: Selected teaching and general hospitals in several Italian regions. SUBJECTS: A total of 6619 subjects from the comparison groups of the case-control studies were included in the analysis. METHODS: We obtained data from a validated 78-item food-frequency questionnaire submitted between 1991 and 2002. For various macronutrients, the partial regression coefficient (variation of BMI (kg m(-2)) per 100 kcal increment of energy intake) was derived from multiple linear regression models, after allowance for age, study centre, education, smoking habits, number of eating episodes and mutual adjustment for macronutrients. RESULTS: BMI was directly associated with protein intake among women only (beta = 0.68) and with unsaturated fats in both genders (for monounsaturated fats beta = 0.27 for men and 0.26 for women; for polyunsaturated fats beta = 0.27 for men and 0.54 for women), and inversely related to carbohydrates (beta = -0.05 for men and -0.21 for women) and number of eating episodes in both genders (beta = -0.42 for men and -0.61 for women) and to saturated fats among women only (beta = -0.57). CONCLUSIONS: These results confirm and provide convincing evidence that, after allowance for selected covariates including total energy intake, a protein-rich diet is not inversely related to BMI, and a carbohydrate-rich diet is not directly related to BMI.  相似文献   
78.
Tramadol is a synthetic codeine analogue used as an analgesic in human and veterinary medicine, but not approved for use in cats. Tramadol (2 mg/kg) was administered intravenously (IV) as preoperative analgesic in 12 cats (6 males) undergoing surgical gonadectomy. The pharmacokinetic profile of the drug and its O-desmethyl metabolite were determined in 8 animals (4 males), while intraoperative effects and postoperative analgesia, estimated by subjective pain score (0–24), were evaluated in all. Mean intraoperative isoflurane consumption was reduced, but hypoventilation was not observed. Sex-related differences were not observed, particularly in terms of postoperative analgesia: rescue analgesic was never administered. Concentrations of the active O-desmethyl metabolite were persistently high in all the animals. Considering the results obtained in this study, tramadol, at the dose of 2 mg/kg IV, did not produce any evident intraoperative cardiorespiratory side effects and with additional investigation may prove to be an appropriate intraoperative analgesic in cats undergoing gonadectomy.  相似文献   
79.
In the Philippines, bacterial wilt caused by Ralstonia solanacearum is one of the most important diseases affecting vegetables and banana. In this study, 89 strains of R. solanacearum isolated from various hosts were screened for their biovar, phylotype, pathogenicity, and genetic diversity. Foreign strains were included for comparison with these Philippine strains. Results of the biochemical and multiplex-PCR tests divided the Philippine strains into five biovars (1, 2, 3, 4, and N2) and three phylotypes (I, II, and IV). Three potato strains belonged to biovar N2/phylotype IV. Pathogenicity tests divided the strains into five pathogenicity types based on their virulence in tomato, potato, eggplant, sweet pepper, and tobacco. Strains classified as biovar N2 were weakly pathogenic to potato (pathogenicity type III) and almost all strains isolated from banana were not pathogenic to the test plants except potato (pathogenicity type V). The results of AFLP analysis divided the strains into four clusters. Cluster 1 was composed of strains isolated from solanaceous crops, ginger (Zingiber officinale), and Morus sp. from the Philippines and other Asian countries. Cluster 2 grouped the potato strains (biovar N2) from the Philippines and Japan and blood disease bacterium strains from Indonesia. Cluster 3 contained the local and foreign strains isolated from potato (biovar 2) and banana (biovar 1). Cluster 4 consisted only of the tomato strain from the USA.  相似文献   
80.
Fuzzati N  Pace R  Villa F 《Fitoterapia》2003,74(3):247-256
Extracts from the leaves of Ginkgo biloba are among the most widely used phytotherapeutics. Some alkylphenols (ginkgolic acids, cardanols and cardols) have been described as potentially hazardous constituents in Ginkgo extracts. Accordingly, a requirement for a maximum concentration of ginkgolic acids has been proposed in the UE and US pharmacopoeias Ginkgo monographs establishing a limit value of 5 ppm. A novel HPLC-UV method, developed by the use of HPLC-APCI-MS HPLC-DAD techniques and allowing the identification of ginkgolic acids and related phenols, is described. The new analytical method, not requiring enrichment procedures, can be used for the quantification of ginkgolic acids in Ginkgo extracts.  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