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   112篇
  免费   9篇
林业   2篇
农学   10篇
基础科学   6篇
  37篇
综合类   11篇
农作物   15篇
水产渔业   6篇
畜牧兽医   17篇
园艺   4篇
植物保护   13篇
  2023年   1篇
  2022年   4篇
  2021年   7篇
  2020年   10篇
  2019年   8篇
  2018年   8篇
  2017年   8篇
  2016年   10篇
  2015年   3篇
  2014年   6篇
  2013年   12篇
  2012年   4篇
  2011年   3篇
  2010年   4篇
  2009年   2篇
  2008年   7篇
  2007年   2篇
  2006年   1篇
  2005年   1篇
  2002年   3篇
  2000年   3篇
  1996年   1篇
  1992年   2篇
  1991年   3篇
  1990年   1篇
  1984年   1篇
  1983年   1篇
  1982年   1篇
  1979年   2篇
  1975年   1篇
  1974年   1篇
排序方式: 共有121条查询结果,搜索用时 156 毫秒
101.

The first objective of the present study was to evaluate if the antibodies induced by the live LaSota and killed Newcastle disease (sub-genotype VIIi) vaccines protect the chickens against exposure with pathogenic avian avulavirus-1 (AAvV-1) of chicken and/or pigeon origins. The second objective was to study the effect of vaccines on stressed birds (dexamethasone, aflatoxin, and heat stressed) with respect to antibody production and protection against pathogenic AAvV-1 challenge. Sixty-one-day-old Hubbard chickens were divided into six groups (gA–gF) with ten animals each. All the groups received LaSota (105 EID50, 0.1 ml per chick) on days 7 and 27 via eye drop and one intramuscular injection of a killed vaccine (sub-genotype VIIi) (107.5 EID50, 1 ml) on day 18, except the control birds received the PBS only. Moreover, group gC-DEX received dexamethasone intramuscularly at a dose rate of 1-mg/kg body weight daily; gD-AFLA had received aflatoxin as oral gavage at a dose rate of 30 ppb daily, and gE-HEAT was kept under heat stressed (38 °C) till challenged. All the groups were challenged with AAvV-1 strain of chicken origin of sub-genotype VIIi, except the group gA-pigeon was challenged with pigeon-origin strain (sub-genotype VIm). The result showed that the gA-pigeon and gB-chicken vaccinate showed 100% and 80% protection. The immunosuppressive birds produced low pre-challenge HI titer, and protection was observed at 40%, 50%, and 70% in gC-DEX, gD-AFLA, and gE-HEAT, respectively. Our findings suggest the stress factors such as aflatoxin in the feed and dexamethasone are immunosuppressive in nature and suppress the immune response and its associated protective role during infection.

  相似文献   
102.
The foraging technique and prey‐handling time of the black‐necked stork (Ephippiorhynchus asiaticus) was studied in Dudhwa National Park, India, from January 1996 to June 1997. The habitat in which the storks foraged played an important role in selecting a particular technique to procure food. Black‐necked storks mostly foraged using a tactile technique (>90%), but sometimes foraged visually. When the water level was estimated to be less than 60 cm, the storks foraged using tactile techniques. There was no difference in the feeding techniques of male and female storks. Foraging attempt rates varied between the sexes in summer (May) and during late winter (February) in 1997. The search time for prey increased when the water level was high and fish were widely distributed. Decreases in water level resulted in concentration offish in certain areas and this contributed to high fish‐catching rates by black‐necked storks. Males had a higher success rate offish capture than females. However, females captured longer fish than males. Prey‐handling time increased in both sexes as fish length increased. Fish 4–6 cm long were most frequently taken by the foraging storks.  相似文献   
103.
Abstract

During the last century, concerns about nitrate presence in the groundwater have tremendously increased worldwide, mainly because of its detrimental consequences on environment and human health. There are different factors contributing their past in nitrate pollution, farm manure is given due consideration. Knowing above facts, a field study was performed to check the effect of different farm yard manure (FYM) levels with urea on nitrate distribution in the soil profile and yield of wheat crop. The experiment was set out in a randomized complete block design, consisted of application of nitrogen at 125?kg ha?1 from urea, 80?kg ha?1 of N from urea +10 tons FYM ha?1 and 20 tons FYM ha?1 with three replications. Wheat (cultivar S7ehar-2006) was sown as test crop. Soil samples were examined to measure the nitrate concentration from four different depths (0–25, 25–50, 50–75, and 75–100?cm) after harvesting. Results showed that the straw yield, total biomass, spike length, and number of grains per spike and 1000-grain weight were significantly influenced by fertilizer strategies. All manure treatments significantly affected the infiltration rate and concentration of nitrate at different depths of the soil profile. Farm yard manure showed greater nitrate concentration up to 50?cm depth as compared to alone urea and combined application, while at the depth of 100?cm, combined application of urea and FYM showed a minimum concentration of nitrates than alone application of either urea or FYM.  相似文献   
104.
Abstract

This experiment carried out as split plot factorial based on a randomized complete block design with three replications during two consecutive years (2015–2016). The main plot consisted of drought stress: complete irrigation, irrigation withholding at R1 stage, irrigation withholding at R2 stage and subplots included foliar application of micronutrients: distilled water (control), zinc sulfate, manganese sulfate and zinc sulfate?+?manganese sulfate and cultivar as: Williams and Zan elite. The results showed that proline and linoleic acid were increased significantly, but chlorophyll a and b, seed yield, protein percentage, oleic and linolenic acids were decreased significantly by irrigation withholding. Also, the maximum values of chlorophyll b, protein percentage and linolenic acid were achieved by Williams. The significant increasing effect of zinc was found on the maximum root and stem proline, chlorophyll b, and oleic, linolenic and linoleic unsaturated fatty acids, meanwhile the maximum leaf proline was obtained by manganese sulfate.  相似文献   
105.
The methanolic extract of the Zanthoxylum rhetsa Roxb. stem bark, given by oral route to mice at doses of 250 and 500 mg/kg, significantly reduced the abdominal contraction induced by acetic acid and the diarrhoeal episodes induced by castor oil in mice.  相似文献   
106.
The sensitivity of crop genotypes determines the level of growth reduction by salinity. Effect of salinity levels (7.5 and 15 dihydrate m?1) using completely randomized design (CRD) with four replications per treatment were compared on germination, chlorophyll content, water potential, ionic sodium and potassium (Na+, K+) balance, and other growth-related parameters of six wheat genotypes for varietal differences under long-term salinity stress. Chlorophyll contents at flowering stage and yield aspects at maturity of all the wheat genotypes decreased with increasing salinity. The maximum Na+ concentration was observed at 7.5 and 15 dS m?1 in Bhakhar and Saher-2000, respectively, while minimum Na+ concentration was observed for 9476. However, the maximum K+ concentration and water potential was noticed in 9476 at 7.5 dS m?1. Careful selection of salt-tolerant genotypes for field crops is an important perspective especially in the developing countries facing salinity problem. Our results revealed that the wheat genotype 9476 performed best regarding growth and physiological parameters compared to other wheat genotypes.  相似文献   
107.
Abstract

This study was designed to investigate the effect of biochar on maize production and nutrient retention with recommended full and half dose of nitrogen (N) and phosphorus (P) nutrition in loamy soil. In the first study, maize was grown in pots with four levels of biochar (0, 2, 4, and 6?t?ha?1) under two levels of NP fertilizer, viz. recommended (200–150?kg?NP?ha?1) and it’s half (100–75?kg?NP?ha?1) dose. The prominent improvement in plant roots traits, leaf area, plant growth, morphological and yield-related parameters were observed with addition of biochar at 2 and 4?t?ha?1; while, plant height, number of grains per cob, grains and biological yield decreased with biochar addition 6?t?ha?1 along with full dose of NP nutrition. In subsequent field studies, two levels of biochar along with control (0, 2, 4?t?ha?1) were investigated. The more improvement in root growth, leaf area and crop growth was observed when biochar was applied at 2?t?ha?1 with full NP nutrition. Biochar application at 2?t?ha?1 with full NP nutrition produced the highest grain yield (6.64?t?ha?1); however, biochar addition (2?t?ha?1) with half NP nutrition resulted in better grain yield than full dose of NP to enhance maize production as compared with full dose of NP without biochar. Therefore, biochar addition (2?t?ha?1) with half-recommended dose of NP prominently improved the maize productivity in loamy soil and serve as better in replacement of full dose of NP fertilizer.  相似文献   
108.
ABSTRACT

Soil amendment with biochar could increase soil microbial activity and biomass. This study contributes to an understanding of the synergistic effects of biochar and phosphate solubilizing microorganisms on safflower yield and soil microbial activity enhancement. In the split plot experiments that repeated in two years, the main factor was biochar types included cow manure, wheat straw, wood biochar and control. The sub factors were phosphate solubilizing microorganisms included the mycorrhizal fungi (Glomus etunicatum and G. mosseae), Bacillus lentus, Pseudomonas fluorescence and control. The highest levels of dehydrogenase, urease activity and microbial biomass carbon were obtained from the cow manure biochar. The maximum activity of acid phosphatase was in the plots inoculated by P. fluorescence in all treatments, whether using or not using biochar. The grain yield of plants inoculated with B. lentus and P. fluorescence was in the same statistical group. The highest grain yield equal to 1527 kg/ha was obtained when using cow manure biochar. According to the results, the application of cow manure biochar and phosphate solubilizing microorganisms, especially mycorrhiza species, can be recommended for improving soil biological traits and safflower yield traits.  相似文献   
109.

The effects of anthropogenic noise have garnered significant attention in marine ecosystems, but comparatively less is known about its impacts on freshwater ecosystems. For fish that provide parental care, the effects of acoustic disturbance could have fitness-level consequences if nest tending behavior is altered. This study explored the effects of motorboat noise on the parental behavior of nesting male smallmouth bass (Micropterus dolomieu; Lacépède, 1802), an important freshwater game fish in North America that provides sole paternal care to offspring. Specifically, we evaluated how boat noise proximity to a bass nest (ranging from 4.5 to 90 m) influenced paternal care behaviors. A total of 73 fish were exposed to a 3-min motorboat playback designed to simulate a boat sound that typically occurs in areas near littoral nesting sites. The fish were video recorded, and their behaviors were analyzed before, during, and after exposure to the playback. Residency time was the only behavioral metric to be adversely affected by noise playbacks but only when in close proximity to the speaker. Our results suggest that boat noise may have an impact on bass reproductive fitness in specific contexts where combustion motors are used near shore during the nesting period. The largely null findings may indicate a resilience to boat noise and/or habituation to the noise. In addition, boats displace water and create waves that represent another form of disturbance that could be experienced by fish but was not simulated here. Future research should integrate behavioral and physiological responses to boat noise and other aspects of boat disturbance to better understand the fitness impacts of boating activity on freshwater fish.

  相似文献   
110.
Soil productivity (SP) without external fertilization influence is an important indicator for the capacity of a soil to support crop yield. However, there have been difficulties in estimating values of SPs for soils after various long-term field treatments because the treatment without external fertilization is used but is depleted in soil nutrients, leading to erroneous estimation. The objectives of this study were to estimate the change of SP across different cropping seasons using pot experiments, and to evaluate the steady SP value (which is defined by the basal contribution of soil itself to crop yield) after various long-term fertilization treatments in soils at different geographical locations. The pot experiments were conducted in Jinxian of Jiangxi Province with paddy soil, Zhengzhou of Henan Province with fluvo-aquic soil, and Gongzhuling of Jilin Province with black soils, China. Soils were collected after long-term field fertilization treatments of no fertilizer (control; CK-F), chemical fertilizer (NPK-F), and combined chemical fertilizer with manure (NPKM-F). The soils received either no fertilizer (F0) or chemical fertilizer (F1) for 3–6 cropping seasons in pots, which include CK-P (control; no fertilizer from long-term field experiments for pot experiments), NPK-P (chemical fertilizer from long-term field experiments for pot experiments), and NPKM-P (combined chemical and organic fertilizers from long-term field experiments for pot experiments). The yield data were used to calculate SP values. The initial SP values were high, but decreased rapidly until a relatively steady SP was achieved at or after about three cropping seasons for paddy and fluvo-aquic soils. The steady SP values in the third cropping season from CK-P, NPK-P, and NPKM-P treatments were 37.7, 44.1, and 50.0% in the paddy soil, 34.2, 38.1, and 50.0% in the fluvo-aquic soil, with the highest value observed in the NPKM-P treatment for all soils. However, further research is required in the black soils to incorporate more than three cropping seasons. The partial least squares path mode (PLS-PM) showed that total N (nitrogen) and C/N ratio (the ratio of soil organic carbon and total N) had positive effects on the steady SP for all three soils. These findings confirm the significance of the incorporation of manure for attaining high soil productivity. Regulation of the soil C/N ratio was the other main factor for steady SP through fertilization management.  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