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   1091篇
  免费   76篇
林业   81篇
农学   138篇
基础科学   22篇
  206篇
综合类   65篇
农作物   76篇
水产渔业   65篇
畜牧兽医   403篇
园艺   17篇
植物保护   94篇
  2023年   11篇
  2022年   12篇
  2021年   33篇
  2020年   35篇
  2019年   23篇
  2018年   44篇
  2017年   53篇
  2016年   46篇
  2015年   34篇
  2014年   43篇
  2013年   70篇
  2012年   81篇
  2011年   61篇
  2010年   43篇
  2009年   35篇
  2008年   45篇
  2007年   38篇
  2006年   26篇
  2005年   32篇
  2004年   17篇
  2003年   23篇
  2002年   29篇
  2001年   21篇
  2000年   12篇
  1999年   13篇
  1998年   11篇
  1996年   7篇
  1994年   11篇
  1992年   12篇
  1991年   9篇
  1990年   12篇
  1989年   9篇
  1988年   17篇
  1987年   18篇
  1986年   11篇
  1985年   7篇
  1984年   9篇
  1983年   11篇
  1982年   9篇
  1981年   13篇
  1980年   6篇
  1979年   14篇
  1978年   8篇
  1975年   13篇
  1973年   8篇
  1972年   6篇
  1971年   7篇
  1970年   11篇
  1969年   13篇
  1968年   6篇
排序方式: 共有1167条查询结果,搜索用时 0 毫秒
951.
Tropical Animal Health and Production - The present study determined trends in the isolation of bacterial pathogens in milk samples submitted from clinical mastitis buffaloes at the University...  相似文献   
952.
Tropical Animal Health and Production - The aim of this study was to evaluate the effects of urea as an additive in the ensiling of pearl millet on the intake, feeding behavior, and metabolic...  相似文献   
953.
954.
Present study is the first attempt to evaluate an indigenous milk ELISA with milk culture, standardize milk PCR, estimate lacto-prevalence of Map and genotype Map DNA from milk samples in few Indian dairy herds. In all 115 cows were sampled from 669 lactating cows in six dairy herds from three districts of North India. Fifty milk samples (four herds) were screened by three tests (milk culture, m-ELISA and m-PCR). Lacto-prevalence of Map in four dairy herds was 84.0% (50.0% in fat and 62.0% in sediment). Screening of both fat and sediment increased the sensitivity of culture. Colonies appeared between 45 and 120 DPI. In indigenous m-ELISA, protoplasmic antigen derived from native Map 'Bison type' strain of goat origin was used. Screening of 115 lactating cows by m-ELISA ('herd screening test') detected 32.1% positive lactating cows (lacto-prevalence). Sensitivity of ELISA was 28.5% and 42.8% in single point cutoff and S/P ratio, respectively. Lacto-prevalence of JD was high in dairy herds (66.6-100.0% by culture and 20.0-50.0% by m-ELISA). DDD farm, Mathura had very high (95.8%) and moderate prevalence of Map and lacto-antibodies, respectively. All cows were clinically suffering from JD. Specific IS 900 PCR was standardized in decontaminated fat and sediment of milk samples. DNA isolated from decontaminated pellets was amplified and characteristic 229 bp band was confirmatory for Map. Of the 50 milk samples, 6.0% were positive in m-PCR. The test needs further standardization. Map DNA were genotyped as Map 'Bison type' by IS 1311 PCR-REA. Of the three tests, milk culture was most sensitive followed by m-ELISA and m-PCR. Map DNA isolated from milk samples of dairy cattle were first time genotyped as Map, 'Bison type' in India. High prevalence of Map in milk of dairy herds, posed major health hazard for calves and human beings.  相似文献   
955.
Inoculation of plasmid DNA, encoding an immunogenic protein gene of an infectious agent, stands out as a novel approach for developing new generation vaccines for prevention of infectious diseases of animals. The potential of DNA vaccines to act in presence of maternal antibodies, its stability and cost effectiveness and the non-requirement of cold chain have heightened the prospects. Even though great strides have been made in nucleic acid vaccination, still there are many areas that need further research for its wholesome practical implementation. Major areas of concern are vaccine delivery, designing of suitable vectors and cytotoxic T cell responses. Also, the induction of immune responses by DNA vaccines is inconclusive due to the lack of knowledge regarding the concentration of the protein expressed in vivo. Alternative delivery systems having higher transfection efficiency and the use of cytokines, as immunomodulators, needs to be further explored. Recently, efforts are being made to modulate and prolong the active life of dendritic cells, in order to make antigen presentation a more efficacious one. For combating diseases like acquired immunodeficiency syndrome (AIDS), influenza, malaria and tuberculosis in humans; and foot and mouth disease, Aujesky’s disease, swine fever, rabies, canine distemper and brucellosis in animals, DNA vaccine clinical trials are underway. This review highlights the salient features of DNA vaccines, and measures to enhance their efficacy so as to devise an effective and novel vaccination strategy against animal diseases.  相似文献   
956.
This study was conducted to evaluate the effects of urea addition on fermentation characteristics, losses and chemical composition of silage of sorghum (Sorghum bicolor) ‘BRS Ponta Negra’. The sorghum plant was chopped and treated with different levels of urea (0.1756, 0.3512, 0.7024 and 1.4048 g per 10 kg fresh forage for the respective proportions of 0.5%, 1.0%, 2.0% and 4.0% of forage (dry matter [DM] basis), and packed into quintuplicate experimen- tal silos to determine its effects on fermentation, losses and chemical composition of sorghum silages. Addition of urea increased lactic acid bacteria up to the level of 60 g kg?1 (DM basis). Compared with control silage, the addition of urea (p < 0.05) reduced DM losses. Urea-treated silages linearly increased (p < 0.05) the ammoniacal nitrogen and crude protein contents, and linearly reduced (p < 0.05) the ethanol content. The pH in urea-treated silages indicated better preservation of substrates obtained from fermentation. The intermediate level of 2.0% urea additive can be used to improve fermentation, reducing losses in sorghum silage without compromising lactic acid production. However, the addition of 0.5% and 1.0% urea to sorghum silage is sufficient to improve aerobic stability.  相似文献   
957.
European Journal of Plant Pathology - Our study aimed to assess the structure and distribution of plant-parasitic nematodes in soybean [Glycine max (L.) Merr] in the south of Brazil. High...  相似文献   
958.
The aim of this study was to evaluate the role of antioxidant enzyme activity and nitric oxide levels induced by 28 day biliary obstruction in the rat. A total of 21 young Swiss albino rats were divided in to 3 groups. Bile duct ligations, bile duct ligations plus resveratrol, sham operated. Bile duct ligations plus resveratrol group received 10 mg/kg dose of resveratrol intraperitonealy once daily throughout for 28 days. Liver damage and cholestasis were determined by biochemical examination. SOD, CAT and GSH-PX activity decreased in BDL group compared with shame opareted groups (p < 0.001). NO levels increased in BDL groups compared with shame opareted groups (p < 0.001). SOD, CAT and GSH-PX activity was found higher in BDL+resveratrol treated groups than BDL groups (p < 0.001). In addition this NO levels decreased in BDL+resveratrol treated groups than BDL groups (p < 0.001). In conclusion, it is thought that resveratrol may be used as a protective agent in biliary obstructions; however, further clinical and experimental studies are needed to verify its antioxidative and hepatoprotective effects.  相似文献   
959.
Fusarium rot of melon, caused by species of the genus Fusarium, has become an important postharvest disease for many Brazilian producers. Due to the delayed onset of symptoms, this disease is often only detected when fruits arrive at the importing country, thus generating economic loss for the exportation of the fruit. This study was developed with the aim of investigating which Fusarium species cause fruit rot in melon and to evaluate any differences in aggressiveness and development of symptoms. Species were identified through phylogenetic analysis of two loci and morphological markers. The 28 isolates obtained from diseased melon fruits of different commercial cultivars were identified as Fusarium falciforme (FSSC), F. sulawesiense, F. pernambucanum (FIESC), and F. kalimantanense (FOSC). Three isolates belong to a new phylogenetic lineage within the F. fujikuroi species complex (FFSC). All isolates were tested for pathogenicity, and first symptoms of rot in Canary melon were observed 2 days after inoculation. Isolates of F. falciforme and F. sulawesiense were shown to be more aggressive. Our results extend information on Fusarium species that cause fruit rot in melon and support the development of management strategies, as there is currently no efficient control for this disease. To our knowledge, this is the first report of the occurrence of species of the FSSC, FOSC, and FFSC from muskmelon fruits in Brazil.  相似文献   
960.
A 60-day feeding trial was conducted to evaluate the haemato-biochemical, innate immune response, antioxidant capacity and histopathological changes in Labeo rohita fingerlings fed rubber protein isolates (RPI). One hundred and eighty fingerlings (average weight 4.45 ± 0.01 g) were distributed into five experimental groups in triplicate and fed with isonitrogenous and isocaloric diets. Soybean protein isolate (SPI) served as the reference diet (Control), and the treatment diets were formulated as RPI25, RPI50, RPI75 and RPI100 replacing 25, 50, 75 and 100% of SPI protein, respectively. The growth performance indices like final body weight (9.54–10.27 g), net weight gain (5.09–5.84 g), metabolic growth rate (4.54–5.02) and feed efficiency ratio (0.60–0.65) among the various groups were not significantly different (P > 0.05). All the haematological parameters, except red blood cells, showed no significant differences compared with the control group (P > 0.05). The immuno-biochemical parameters like albumin, globulin, total immunoglobulin, respiratory burst and lysozyme activities among the various groups did not differ significantly (P > 0.05). The stress enzyme such as superoxide dismutase (SOD), catalase (CAT) and oxidative stress marker malondialdehyde (MDA) showed no significant difference (P > 0.05). Histopathological examination of the liver revealed no marked changes. In summary, the results showed that RPI was well utilised by the fish and its inclusion did not generate any oxidative-induced stress, thus, RPI may be suggested as a potential replacement for SPI in fish diets without any detrimental effects. Hence, protein isolation offers a unique opportunity for the utilisation of rubber seed meal.  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