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   286篇
  免费   18篇
林业   23篇
农学   14篇
基础科学   1篇
  62篇
综合类   42篇
农作物   27篇
水产渔业   33篇
畜牧兽医   65篇
园艺   12篇
植物保护   25篇
  2023年   1篇
  2022年   6篇
  2021年   7篇
  2020年   4篇
  2019年   10篇
  2018年   22篇
  2017年   12篇
  2016年   14篇
  2015年   3篇
  2014年   11篇
  2013年   20篇
  2012年   26篇
  2011年   15篇
  2010年   15篇
  2009年   10篇
  2008年   15篇
  2007年   13篇
  2006年   7篇
  2005年   8篇
  2004年   12篇
  2003年   6篇
  2002年   11篇
  2001年   1篇
  2000年   6篇
  1999年   5篇
  1998年   3篇
  1997年   1篇
  1996年   3篇
  1995年   2篇
  1994年   1篇
  1993年   1篇
  1991年   4篇
  1990年   3篇
  1989年   4篇
  1988年   1篇
  1987年   2篇
  1986年   1篇
  1982年   2篇
  1981年   1篇
  1979年   2篇
  1978年   2篇
  1976年   1篇
  1975年   4篇
  1970年   1篇
  1966年   1篇
  1965年   2篇
  1954年   1篇
  1949年   1篇
排序方式: 共有304条查询结果,搜索用时 390 毫秒
221.
1. The study was conducted to ascertain the effects of supplemental organic acids and chromium (Cr) on production and carcase traits of broiler chickens. 2. A total of 120 1-d-old broiler chicks were divided into 4 treatment groups in a 2 x 2 factorial design (each treatment group contained 6 replicates with 5 birds per replicate). 3. The diets were supplemented with an organic acid blend containing ortho-phosphoric, formic and propionic acid and calcium propionate (1 g/kg diet) and inorganic trivalent chromium (Cr(3+)) as chromic chloride hexahydrate (0.5 mg/kg diet) either independently or together as a combination for 35 d. 4. Individual supplementation of organic acids and Cr(3+) and their combination significantly improved the food conversion ratio, hot and dressed carcase weight and weight of the wholesale cuts compared to the control group of birds. 5. Organic acids, either independently or along with Cr(3+), increased total accretion of ash in carcase. Protein accretion was improved by dietary Cr(3+) and organic acid supplementation compared to the control group and a further improvement in this regard was observed when Cr(3+) and organic acid were supplemented together. Across the treatment groups meat fat content and fat accretion were lower in birds receiving dietary Cr(3+) supplementation. 6. Circulatory Cr(3+) and meat Cr(3+) concentration increased compared to the other treatment groups when Cr(3+) was supplemented to the birds. 7. It was concluded that, instead of individual supplementation, a combination of Cr(3+) and organic acids may improve the production and carcase traits of broilers more effectively presumably because of an additive effect.  相似文献   
222.
The tensile properties of spun yarns decisively influence its performance in various mechanical processing stages. This study is primarily aimed at simultaneous analysis of two tensile properties of spun yarns namely tenacity and breaking strain, which play crucial role in determining the frequency of warping breaks. The threshold values of yarn tenacity and breaking strain required for 20’s Ne carded cotton yarn to sustain the imposed stresses and strains during warping process have been determined using a bivariate normal distribution model. This study opens up the possibility of minimizing end breakage rate in various manufacturing processes of textile industry by engineering of spun yarns devoid of potential weak spots which are responsible for breaks.  相似文献   
223.
Antigens from larvae of Hyalomma anatolicum anatolicum were extracted and purified by immunoaffinity chromatography using immunoglobulin ligands from cross-bred animals immunized with soluble larval antigen. Affinity-purified antigen (Aff-TLE) and a total larval extract (TLE) were used to immunize cross-bred (Bos indicus×Bos taurus) cattle. The group immunized with Aff-TLE rejected 71.6% of larvae and 77.3% of nymphs. However, the rejection percentages were lower in the TLE-immunized group. No significant changes in the feeding period, moulting percentages or moulting period of engorged larvae and nymphs were recorded. There was, however, a significant decrease in the number of resultant nymphs p<0.01) and adults (p<0.01) in the ticks fed on the Aff-TLE-immunized group. The Aff-TLE antigen was 93.3% purified. SDS-PAGE analysis identified a 39 kDa protein, reported for the first time, as the antigen responsible for the induction of resistance in the host.  相似文献   
224.
The methanol extract of the dried leaves of Abies webbiana was evaluated for antimicrobial activity. The methanol extract showed a broad spectrum of antibacterial activity.  相似文献   
225.
Eight isonitrogenous (approximately 35 % crude protein) and isocaloric (17.58 kJ g?1) diets incorporating raw and fermented sesame oilseed meal replacing other feed ingredients including fishmeal at 10, 20, 30 and 40 % levels by weight into a fishmeal-based reference diet (RD) were fed to rohu, Labeo rohita, fingerlings (mean initial weight 3.19 ± 0.09 g) for 80 days. Two phytase-producing bacterial strains (LF1 and LH1 of Bacillus licheniformis) isolated from the foregut and hindgut regions of adult L. rohita were used for fermentation of oilseed meal for 15 days at 37 ± 2 °C. Fermentation of sesame seed meal was effective in significantly reducing the crude fibre content and anti-nutritional factors such as tannins and phytic acid and enhancing available free amino acids, free fatty acids and mineral concentration. In terms of growth, feed conversion ratio and protein efficiency ratio, 30 % fermented oilseed meal incorporated diet resulted in a significantly (P < 0.05) better performance of rohu fingerlings. In general, growth and feed utilization efficiencies of diets containing fermented oilseed meal were superior to diets containing raw meal. The apparent digestibility of protein, lipid, ash and minerals (phosphorus, calcium, manganese, copper and iron) was significantly (P < 0.05) higher in fish fed diet containing 30 % fermented oilseed meal in comparison with those fed RD. The maximum deposition of protein in the carcass was recorded in fish fed the diet containing 30 % fermented seed meal.  相似文献   
226.
Darjeeling and Sikkim hills of India are well known for production of mandarin orange (Citrus reticulata). The recent spread of Citrus tristeza virus (CTV) has threatened the citrus cultivation in this region. During a survey in Darjeeling and Sikkim hills, pomelo trees were recorded as CTV free. Since pomelo trees did not show any disease appearance, a study was undertaken to ascertain whether they are resistant to CTV infection or resistant to aphid feeding or both. Toxoptera citricida, the most efficient aphid vector and which is abundantly present in this region, did not feed on pomelo when other Citrus species such as mandarin, kagzi lime and rough lemon were available. Additionally, CTV isolates of Darjeeling and Sikkim hills were not transmissible to pomelo either by T. citricida or grafting. We report for the first time that pomelo is resistant to isolates of CTV present in this region.  相似文献   
227.
The present experiment was aimed at studying the conditioning, maturation and natural spawning of orange‐spotted grouper, Epinephelus coioides, in a recirculatory aquaculture system (RAS). Thirty fish (n = 30; 3.35 ± 0.05 kg) were stocked in a circular tank of 125 m3 capacity fitted with an RAS for conditioning and broodstock development. After 15 days, 15 fish were implanted with 17 α methyl testosterone and letrozole at the rate of 5 mg and 0.2 mg/kg body weight, respectively, for conversion from female to male. The gonadal development started after 1 month, and by 90th day, 63.53 ± 3.78% and 2.07 ± 0.84% of the oocytes attained a size of 400–500 μm and 500–600 μm respectively. Natural spawning commenced in the RAS from 4th month onward after stocking and spawning continued round the year. The spawning pair showed courtship behaviour with a typical vertical burst of swimming just before release of gametes. The total number of eggs spawned during 1 year was 47.23 million with spawning frequency varying form 5 to 13 times per month. The association of spawning events with new moon day (lunar cycle) weakened as time progressed. The mean monthly fertilization and hatching rates varied from 77.80 ± 3.34% to 83.70 ± 1.76% and 82.80 ± 4.21% to 88.33 ± 1.39% respectively. The study proved that RAS is an efficient system that provides a stable, controllable and conducive environment for year‐round natural breeding of orange‐spotted grouper.  相似文献   
228.
试验旨在确定添加有机酸和铬(Cr)对肉鸡生产性能和屠宰特性的影响。试验采用2x2因子设计,选择120只1日龄肉仔鸡随机分配到4个处理中,每个处理6个重复,每个重复5只。试验饲粮分别添加有机酸混合物(含正磷酸、乙酸、丙酸和丙酸钙)1g·kg^-1、无机三价铬(Cr^3+,如Crcl3·6H2O)0.5mg·k^-1或两者的混合物。试验期35d。与对照组相比,单独添加有机酸、Cr3’以及同时添加两者,均显著改善了肉鸡饲料转化率、活重、胴体重和销售肉片重。有机酸单独或与Cr^3+同时添加,提高了胴体总灰分的积累。与对照组相比,添加有机酸或Cr^3+改善了蛋白积累;两者同时添加效果更佳。添加Cr^3+降低了肌肉中脂肪含量和脂肪堆积。与其他处理组相比,添加Cr^3+提高循环CP和肌肉中Cr^3+的浓度。结论:由于有机酸和Cr^3+存在协调效应,两者混合应用替代单独添加,可更有效地改善肉鸡生产性能和屠宰特性。  相似文献   
229.
The effects of dietary administration of inorganic zinc (zinc sulphate, ZnSO4) and nano zinc (zinc oxide nanoparticles, ZnO‐NP) were evaluated in rohu, Labeo rohita fingerlings. Fish were fed with a basal diet (Control) supplemented with ZnSO4 (T1, T2 and T3) and ZnO‐NP (T4, T5 and T6) at 10, 20 and 30 mg/kg, respectively, for a duration of 45 days. The results revealed that fish fed diet containing 20 mg ZnO‐NP per kg (T5) had the highest weight gain and specific growth rate (SGR, % per day), which was significantly different (p < .05) from the other experimental diets. Significantly (p < .05), higher activities of the digestive and metabolic enzymes were recorded in the fish fed ZnO‐NP containing diets as compared to the diets containing inorganic Zn or control diet. The maximum serum glucose and protein levels were noted in fish reared on diet T5. Both SGOT and SGPT activities were significantly increased in fish fed Zn‐supplemented diets (T1 to T6), as compared to the control group. Similarly, innate immune parameters were improved with feeding Zn incorporated diets. The highest phagocytic (40.74 ± 0.65%) and respiratory burst (0.33 ± 0.001, OD 630nm) activities were recorded in the fish fed diet containing ZnO‐NPs at 20 mg/kg (T5). The maximum superoxide production and serum peroxidase activity were detected in the fish fed T5 and T6 diets. Overall, results indicated that short‐duration feeding (≤45 days) of dietary ZnO‐NP (20 mg/kg) improved growth, enzyme activity, serum biochemical parameters and immune function in rohu fingerlings.  相似文献   
230.
To examine the role of organic manure on boron (B) availability, a greenhouse experiment was conducted to study the effect of B and farmyard manure (FYM) levels on growth, yields, and B accumulation of sunflower (Helianthus annuus L.). Application of B or FYM individually increased the plant height, capitulum diameter, dry matter yields of seed and stalk and their B concentration and accumulation. The interaction of B and FYM levels had a significant influence only on B concentration of stalk and total B accumulation of sunflower. In the absence of B application, use of highest level of FYM (10 g kg‐1 soil) significantly increased B concentration of stalk and total B accumulation by the crop while with B application, use of FYM at lower rates was effective. Application of B or FYM, especially at higher rates of the latter (5 and 10 g FYM kg‐1 soil) increased the content of hot‐water soluble soil B in the soil after crop harvest. The interaction of B and FYM levels had no significant effect on the content of hot‐water soluble soil B. Application of FYM increased apparent availability of native and added B from soil to sunflower crops.  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