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   2528篇
  免费   136篇
林业   212篇
农学   293篇
基础科学   31篇
  574篇
综合类   121篇
农作物   199篇
水产渔业   303篇
畜牧兽医   653篇
园艺   70篇
植物保护   208篇
  2023年   36篇
  2022年   73篇
  2021年   82篇
  2020年   102篇
  2019年   126篇
  2018年   154篇
  2017年   153篇
  2016年   119篇
  2015年   83篇
  2014年   118篇
  2013年   225篇
  2012年   180篇
  2011年   156篇
  2010年   134篇
  2009年   96篇
  2008年   105篇
  2007年   100篇
  2006年   84篇
  2005年   61篇
  2004年   49篇
  2003年   42篇
  2002年   32篇
  2001年   39篇
  2000年   35篇
  1999年   26篇
  1998年   18篇
  1997年   15篇
  1996年   9篇
  1995年   7篇
  1994年   7篇
  1993年   6篇
  1992年   11篇
  1991年   14篇
  1990年   13篇
  1989年   10篇
  1988年   11篇
  1987年   12篇
  1986年   7篇
  1985年   6篇
  1984年   7篇
  1983年   8篇
  1982年   5篇
  1981年   9篇
  1980年   5篇
  1979年   14篇
  1974年   8篇
  1973年   8篇
  1971年   7篇
  1969年   6篇
  1967年   4篇
排序方式: 共有2664条查询结果,搜索用时 15 毫秒
71.
An experiment was conducted to evaluate the effect of roasting whole soybean in the local level on their chemical composition, nitrogen fractions, in situ degradability, and feeding performance in crossbred (Karan Swiss and Karan Fries) dairy cows. Twelve lactating crossbred cattle (369.08 ± 17.53 kg body weight) were randomly divided into two groups on the basis of milk yield (10.18 kg/day) and day of calving (89 days) in a randomized block design. Cows were fed green maize fodder and concentrate mixtures with 1 kg raw soybean as fed basis (7.6% of total diet) in the control group, where as roasted soybean replaced raw soybean in the treatment group to make both diets isonitrogenous and isocaloric. The roughage to concentrate ratio was around 55:45 in both diets. The cows were housed in individual byres and fed experimental diet for 90 days. The total dry matter intake per animal in both groups was similar. The digestibility of dry matter, organic matter, crude protein, ether extract, and neutral detergent fiber was comparable in both groups. The average milk production and fat-corrected milk yield per day was similar during the trial. Milk fat, milk protein, and solids not fat content remained unaffected and similar in both groups. All the animals maintained their body weight in both groups. Thus, rumen bypassing of protein fractions at the present method of bypassing did not have the desired level of beneficial effect in medium producing crossbred cows.  相似文献   
72.
73.
74.
The objectives of the present study were to investigate phytochemical screening and to assay cytotoxicity and antibacterial activities of ethanolic extracts of leaves of two medicinal plants, Aglaonema hookerianum Schott (Family: Araceae) and Lannea grandis Engl. (Family: Anacardiaceae) available in Bangladesh. The brine shrimp lethality bioassay showed that the ethanolic extracts of Aglaonema hookerianum and Lannea grandis possessed cytotoxic activities with LC50 5.25 (microg mL(-1)) and 5.75 (microg mL(-1)) and LC90 10.47 (microg mL(-1)) and 9.55 (microg mL(-1)), respectively. Two extracts obtained from leaves were examined for their antibacterial activities against some gram positive bacteria such as Bacillus subtilis, Bacillus megaterium and Staphylococcus aureus, also gram negative strains of Pseudomonas aeruginosa, Escherichia coli, Shigella dysenteriae, Salmonella typhi, Salmonella paratyphi and Vibrio cholerae. Agar disc diffusion method was applied to observe the antibacterial efficacy of the extracts. Results indicated that both plant extracts (500 microg disc(-1)) displayed antibacterial activity against all of the tested microorganisms. These results were also compared with the zones of inhibition produced by commercially available standard antibiotic, Amoxicillin at concentration of 10 microg disc(-1). Observed antibacterial properties of the ethanolic extract of Aglaonema hookerianum Schott and Lannea grandis Engl. showed that both plants might be useful sources for the development of new potent antibacterial agents.  相似文献   
75.
Geographical isolates ofSpodoptera litura (Fabricius) (Noctuidae: Lepidoptera) nucleopolyhedrovirus (SpltNPV), collected from different parts of India and maintained at Tamil Nadu Agricultural University, were compared for their biological activity and subjected to Restriction Endonuclease (REN) analysis. Neonate and second instar bioassay studies revealed similarity in biological activity as shown by the overlapping fiducial limits of LC50 values. However, there were differences in yield among isolates: significantly higher yields were obtained from isolates UAS and CBE than from the BARC isolate. REN analysis of the four isolates withPst I,Hind III,Bam HI andEco RI enzymes indicated genotypic variation among the isolates. Based on the commonality of the bands, the isolates could be broadly divided into two groups: isolates AU and CBE formed one group, and the other group comprised UAS and BARC based on genetic relatedness. http://www.phytoparasitica.org posting Nov. 21, 2005.  相似文献   
76.
TREATMENT OF DIAPHRAGMATIC HERNIA IN BUFFALOES   总被引:2,自引:0,他引:2  
The surgical treatment of diaphragmatic hernia attempted on 19 lactating buffaloes is described. Thirteen cases recovered uneventfully, 1 recovered after developing brisket oedema and 5 died, 3 during surgery and 2 postoperatively. The desired depth of anaesthesia was achieved by the administration of 6% chloral hydrate followed by 5% thiopentone sodium. A postxiphoid approach and the use of a continuous lock stitch suture were preferred to repair the vent in the diaphragm. Pre- and post-operative use of hydrocortisones and fluids and sufficient tissue oxygenation by controlled positive pressure respiration are believed to be keys to the success of the treatment adopted.  相似文献   
77.
The sensitivity and specificity of the enzyme-linked immunosorbent assay (ELISA) for the diagnosis of Taenia solium cysticercosis was evaluated in experimentally and naturally infected pigs, using T. solium larval scoleces and its fractionated 1st and 2nd peaks on Sephadex G-200 as antigens. First peak antigen gave maximum sensitivity and highest antibody titres. The overall sensitivity of this test was found to be 91.5, 95.8 and 70.8% with scolex, 1st and 2nd peak antigens, respectively. False positive reactions occurred in 9.09% of uninfected pigs with scolex and 1st peak antigens and cross-reactions occurred in 25% of Taenia hydatigena-infected animals using scolex and 2nd peak antigens. No cross-reaction was observed using 1st peak antigen. The specificity of the test was 92.3, 96.2 and 92.3% with scolex, 1st and 2nd peak antigens, respectively.  相似文献   
78.
Tropical Animal Health and Production - The rise of antibiotic resistance and its global outreach has recently become a subject of increasing importance in veterinary research with an objective to...  相似文献   
79.
Dynamics of salmonella infection in fryer roaster turkeys   总被引:2,自引:0,他引:2  
  相似文献   
80.
In the present study, (co)variance components and genetic parameters in Nellore sheep were obtained by restricted maximum likelihood (REML) method using six different animal models with various combinations of direct and maternal genetic effects for birth weight (BW), weaning weight (WW), 6-month weight (6MW), 9-month weight (9MW) and 12-month weight (YW). Evaluated records of 2075 lambs descended from 69 sires and 478 dams over a period of 8 years (2007–2014) were collected from the Livestock Research Station, Palamaner, India. Lambing year, sex of lamb, season of lambing and parity of dam were the fixed effects in the model, and ewe weight was used as a covariate. Best model for each trait was determined by log-likelihood ratio test. Direct heritability for BW, WW, 6MW, 9MW and YW were 0.08, 0.03, 0.12, 0.16 and 0.10, respectively, and their corresponding maternal heritabilities were 0.07, 0.10, 0.09, 0.08 and 0.11. The proportions of maternal permanent environment variance to phenotypic variance (Pe2) were 0.07, 0.10, 0.07, 0.06 and 0.10 for BW, WW, 6MW, 9MW and YW, respectively. The estimates of direct genetic correlations among the growth traits were positive and ranged from 0.44(BW-WW) to 0.96(YW-9MW), and the estimates of phenotypic and environmental correlations were found to be lower than those of genetic correlations. Exclusion of maternal effects in the model resulted in biased estimates of genetic parameters in Nellore sheep. Hence, to implement optimum breeding strategies for improvement of traits in Nellore sheep, maternal effects should be considered.  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