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   16865篇
  免费   45篇
  国内免费   3篇
林业   3668篇
农学   1308篇
基础科学   139篇
  2820篇
综合类   773篇
农作物   2121篇
水产渔业   1814篇
畜牧兽医   1239篇
园艺   1117篇
植物保护   1914篇
  2024年   1篇
  2023年   2篇
  2022年   11篇
  2021年   24篇
  2020年   22篇
  2019年   18篇
  2018年   2757篇
  2017年   2720篇
  2016年   1198篇
  2015年   86篇
  2014年   29篇
  2013年   25篇
  2012年   826篇
  2011年   2159篇
  2010年   2123篇
  2009年   1270篇
  2008年   1344篇
  2007年   1598篇
  2006年   58篇
  2005年   127篇
  2004年   116篇
  2003年   169篇
  2002年   75篇
  2001年   12篇
  2000年   47篇
  1999年   8篇
  1998年   6篇
  1997年   4篇
  1995年   3篇
  1994年   3篇
  1993年   15篇
  1992年   8篇
  1991年   1篇
  1990年   1篇
  1989年   8篇
  1988年   12篇
  1987年   4篇
  1986年   2篇
  1985年   3篇
  1984年   1篇
  1983年   1篇
  1981年   1篇
  1977年   4篇
  1972年   1篇
  1969年   1篇
  1968年   4篇
  1967年   2篇
  1965年   1篇
  1960年   1篇
  1929年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Research in control of tick-borne diseases and trypanosomosis, and their vectors, namely, ticks and tsetse flies respectively, has been on going for decades. However, very little attention has been paid to the socio-economic factors that are likely to influence the outcome of the interventions in the control of these diseases. Thus, this study was designed to investigate these factors, mainly the intra-household factors influencing decision-making in the control of Vector-borne diseases in the pastoralist areas of Uganda. These factors included: indigenous technical knowledge, household economic factors, and gender. Both qualitative and quantitative methods were used in the collection and analysis of data. The tools used for data collection included among others, participatory learning and action (PLA), and Case studies. The findings included the following: In pastoralist households, a big proportion of the household budget was allocated to vector-borne diseases control. In the male-headed households, men dominated decision-making on vector-borne diseases control, although the goals and priorities of men and women in these households were not the same. Also, vector-borne disease control was predominantly by use of modern veterinary drugs, and pastoralists treated sick cattle by themselves even in situations where there were veterinary personnel.  相似文献   
992.
Three hundred and twenty 1-week old ducklings (160 males and 160 females) were used to evaluate the body weight, body parts and carcass characteristics of the African Muscovy duck. Sexual dimorphism was in favour of the male for all the parameters throughout the experimental period, however the difference was significant (P < 0.05) only after week 2. The 12-week old male weighed 1832.0 ± 180.4 g while the female reached only 68.2% of the male weight. Metatarsus diameter, thoracic perimeter, body length, length of bill, foot and wing in cm were respectively 1.3, 29.5, 57.5, 7.0, 27.1 and 27.8 for the male as compared with 1.2, 25.8, 51.0, 6.3, 23.3 and 26.9 for the female. Body measurements were highly (P < 0.01) correlated with body weight for both sexes, however the highest correlation coefficients were obtained with wing length (0.990 and 0.995) and thoracic perimeter (0.993 and 0.973) for female and male respectively. Live body weight had a linear relationship with both wing length (R2 = 0.991 and 0.81) and thoracic perimeter (R2 = 0.948 and 0.986) for male and female respectively. The female duck yielded higher percent ready-to-cook carcass (66.3%), breast (13.6%), liver (2.8%), heart (1.5%) and gizzard (3.8%) as compared to the male (65.0%, 12.0%, 2.5%, 1.1% and 3.4% respectively) although the difference was not significant (P > 0.05). The male small intestine (185.1 ± 3.4 cm), colon (14.8 ± 1.0 cm) and caecum (17.9 ± 0.4 cm) were significantly (P < 0.05) longer than that of the female (152.2 ± 1.8, 10.8 ± 0.7 and 14.85 ± 0.6 cm respectively).  相似文献   
993.
This report describes the proliferation and transmission patterns of Pasteurella multocida B:2 among stressful goats, created through dexamethasone injections. Thirty seven clinically healthy adult goats were divided into three groups consisted of 15 goats in group A, 11 goats in group B and the remaining 11 in group C. At the start of the study, all goats of group A were exposed intranasally to 1.97 × 1010 CFU/ml of live P. multocida B:2. Dexamethasone was immediately administered intramuscularly for 3 consecutive days at a dosage rate of 1 mg/kg. The exposed goats were observed for signs of HS for a period of 1 month. At the end of the 1-month period, 11 goats from group B were introduced into and commingled with the surviving goats of group A before all goats from both groups were immediately injected intramuscularly with dexamethasone for 3 consecutive days. The treatment with dexamethasone was then carried out at monthly interval throughout the 3-month study period. Goats of group C were kept separately as negative control. Three surviving goats from each group were killed at 2-week interval for a complete post-mortem examination. Two (13%) goats of group A were killed within 24 hours after intranasal exposure to P. multocida B:2 while another two (13%) goats from the same group were killed on day 40, approximately 10 days after the second dexamethasone injection. All four goats showed signs and lesions typical of haemorrhagic septicaemia. Bacteraemia was detected in 3 goats of group A that were having rectal temperature higher than 41°C. The P. multocida B:2 isolation pattern was closely associated with dexamethasone injections when significantly (p < 0.05) higher rate of isolations from both groups were observed after each dexamethasone injection. Transmission of P. multocida B:2 from goats of group A to group B was successful when P. multocida B:2 was isolated from goats of group B for a period of 28 days. There was a strong correlation between dexamethasone injections, rate of bacterial isolation and serum cortisol level. The IgG level showed an increasing trend 2 weeks after exposure to P. multocida B:2 and remained high throughout the study period.  相似文献   
994.
995.
A study was conducted to evaluate the macro and trace mineral contents of ten enset varieties collected from Sidama zone of southern Ethiopia. Samples of leaf lamina, leaf midrib, pseudostem and corm were taken from ten enset varieties at the age of 5 to 6 years during the main rainy season. The dry weight of each variety and fraction were also determined. Mineral contents in fractions of different enset varieties were analysed and compared with nutrient requirements of ruminants. The contribution of different enset fractions to the total dry weight was variable (P < 0.05), the highest being from pseudostem and the lowest from leaf lamina. There were varietal differences (P < 0.05) in macro and trace mineral content in different fractions except phosphorus (P) content of leaf lamina. Most enset fractions were rich sources of major minerals such as P, potassium (K), calcium (Ca) (except corm) and magnesium (Mg). Sodium (Na) content was very low. Most fractions were rich in iron (Fe) and manganese (Mn), but deficient in copper (Cu), except leaf lamina. Zinc (Zn) content was high in corm, but low in other fractions. This account of the macro and trace mineral content of different enset varieties and fractions could help in strategic supplementation intended to alleviate mineral deficiencies.  相似文献   
996.
AGPT and HA tests were employed for rapid diagnosis of PPRV infection in sheep and goats in Sudan. Forty lymph nodes and spleen samples from suspected cases of PPR in both sheep and goats were examined by AGPT and HA tests for detection of PPRV antigen. Viral antigen was detected from (77.5%) of the samples tested by AGPT and (92.5%) tested by HA test. The results of both tests revealed that HA test was more sensitive than AGPT for detection of PPRV antigen (Kappa statistics 0.4366). Another advantage of the HA test over AGPT was that it can differentiate PPRV from RPV. Thus the HA test represents a quick, easy, simple, cheap and reliable confirmatory test for the diagnosis of PPR and differential diagnosis of PPRV and RPV. The HA test was carried out using chicken, goat and pig RBCs. Chicken RBCs were found to be the most sensitive for detection of PPRV antigen, followed by goat then pig RBCs. The HA time when using chicken RBCs was 20–25 minutes, using goat RBCs was 25–30 minutes and using pig RBCs was 40–45 minutes. The distribution of PPR infection in four different regions of Sudan was investigated.  相似文献   
997.
Foliage of Afzelia africana, Pterocarpus erinaceus and Khaya senegalensis, from 10 trees per species, was collected every two weeks during the late dry, rainy and cool season to determine the seasonal effects on chemical composition. Fifteen rams of the Djallonké breed, weighing on average 20.0 kg, were used to evaluate the voluntary intake and digestibility of hay of A. gayanus, foliage of A. africana (as a sole feed), and A. africana, P. erinaceus and K. senegalensis offered with 30% of the diet as A. gayanus hay. The crude protein (CP) content of A. africana, and P. erinaceus decreased significantly from the late dry season to the cool season when that of K. senegalensis tended to increase. The mean CP of A. africana, P. erinaceus and K. senegalensis differed significantly (173 g, 139 g and 114 g/kg DM, respectively). The DM intake of A. africana offered with hay (571 g/d) or as a sole feed (598 g/d) were not significantly different, but was higher than that of P. erinaceus (428 g/d) and K. senegalensis (298 g/d). The digestibility calculated by difference of DM and CP of A. africana (582 g/kg DM and 795 g/kg CP, respectively) did not differ significantly from A. africana as a sole feed, but were higher than for the other species. The nutritive value of A. africana seems to justify the high preference of herders for this species.  相似文献   
998.
The objective of the present study was to describe the prevalence and risk factors associated with cryptosporidiosis in buffalo calves in Middle Egypt. During one year, 458 fecal samples were collected from buffalo calves less than 3 month age in 55 small scale herds and examined for the presence of Cryptosporidium oocysts. Data describing age, gender, season, and herd management practices were gathered to assess potential risk factors. Fecal examination showed that 14.19% of the examined calves were positive for Cryptosporidium spp. Calves at 1-15 days were at the highest risk (P < 0.001), and a significant relationship between season and infection (P < 0.05) was recorded. A significant association between infection and hygiene (P < 0.001), type of floor (P < 0.01) and source of water (P < 0.01) was also recorded. Statistical analysis concerning the clinical signs and fecal characteristics revealed a significant association with fecal consistency (P < 0.001), presence of blood (P < 0.01) and mucous (P < 0.01). Moreover, a significant association was found between infection and the desire for suckling (P < 0.05) and tenesmus (P < 0.05). The results of the present study demonstrated the strong relation between infections by Cryptosporidium spp. and diarrhea in buffalo calves.  相似文献   
999.
After very hot summer, 22 sheep from 5 different flocks consisting of approximately 150-200 animals each were diagnosed with facial eczema in September 2005, in southwest Turkey. Photophobia, corneal opacity, severe ulcers of the facial skin, especially localized around the eyes and mouth, and 3% mortality were the most prominent clinical symptoms. GGT levels of the animals were very high and varying between 261- 328 U/l. While the activities of ALT and total bilirubin were elevated and AST was normal in affected sheep. Total bilirubin level was higher than normal. Seven of the 22 sheep were euthanatized and necropsy was performed on all of these animals. Severe icterus, hepatomegaly, enlarged gallbladder, congestion of mesenteric vessels were the common necropsy findings. Histopathological changes of the liver included necrosis of the hepatocytes, cholangiohepatitis characterized by mononuclear inflammatory cell infiltrate in the portal area and mild to severe fibrosis around bile ducts. A diagnosis of sporidesmin toxicosis was made based on the histopathology of the livers, the elevation in liver enzymes, and the development of cutaneous lesions consistent with photosensitization and high spore counts in the ruminal contents. Surviving sheep were treated with procaine penicillin + dihidrostreptomycin sulfate, multivitamin complexes and flunixin meglumine. Additionally, zinc sulphate was also given at a dose of 6 gr per 100 lt drinking water for 28 days. All treated sheep recovered. Pasture spore counts were between 96,300- 267,500 spores/g grass.  相似文献   
1000.
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