全文获取类型
收费全文 | 17114篇 |
免费 | 64篇 |
专业分类
林业 | 3678篇 |
农学 | 1324篇 |
基础科学 | 142篇 |
2888篇 | |
综合类 | 737篇 |
农作物 | 2146篇 |
水产渔业 | 1851篇 |
畜牧兽医 | 1378篇 |
园艺 | 1116篇 |
植物保护 | 1918篇 |
出版年
2023年 | 3篇 |
2022年 | 13篇 |
2021年 | 45篇 |
2020年 | 38篇 |
2019年 | 46篇 |
2018年 | 2767篇 |
2017年 | 2727篇 |
2016年 | 1215篇 |
2015年 | 95篇 |
2014年 | 45篇 |
2013年 | 60篇 |
2012年 | 848篇 |
2011年 | 2186篇 |
2010年 | 2129篇 |
2009年 | 1285篇 |
2008年 | 1354篇 |
2007年 | 1609篇 |
2006年 | 60篇 |
2005年 | 132篇 |
2004年 | 124篇 |
2003年 | 180篇 |
2002年 | 75篇 |
2001年 | 12篇 |
2000年 | 46篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 6篇 |
1994年 | 1篇 |
1993年 | 14篇 |
1992年 | 9篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1988年 | 12篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 6篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1969年 | 1篇 |
1968年 | 4篇 |
1967年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
991.
992.
Mezo M González-Warleta M Castro-Hermida JA Ubeira FM 《Veterinary parasitology》2008,157(3-4):235-243
Fasciola hepatica infection is an important cause of lost productivity in livestock worldwide. Effective control of fasciolosis is difficult, especially in milking cows, which can only be treated during dry periods, a control strategy that has not been yet evaluated. In this cross-sectional study, we investigated the effect of the type of flukicide treatment on the prevalence and intensity of infection in dairy cattle from Galicia, an area where fasciolosis is endemic and which is also the main milk-producing region in Spain. Faecal samples were taken from 5188 dairy cows on 275 randomly selected farms for measurement of the concentration of F. hepatica coproantigens by a monoclonal antibody based immunoassay (MM3-COPRO ELISA). On the same day as the sampling, each farm owner/manager was questioned about the types of treatment used on the farm. Three groups of farms were considered according to the fasciolicide treatment: (A) flukicides were not used, (B) an anthelmintic effective against mature stages of flukes was used (albendazole or netobimin) and (C) a fasciolicide effective against immature and mature stages was used (triclabendazole: TCBZ). Results indicated that 16.0% (832/5188) cows from 61.1% (168/275) herds were infected by F. hepatica. The mean coproantigen concentration in infected herds was 13.0ng/ml (range 0.9-112.6ng/ml). The highest individual concentration recorded was 496.6ng/ml. Herd and within-herd prevalences of F. hepatica were similar in all three groups, but surprisingly, individual prevalence and antigen concentration were higher in Group C (p<0.05). The percentage of farms with within-herd prevalences >25% was very high in all three groups, and no significant differences were observed. In contrast, the percentage of herds with mean antigen concentrations >20ng/ml was significantly lower (p<0.05) in Groups A and B (14.4% and 14.9%, respectively) than in Group C (50.0%). The proportion of herds that exceeded both limits (25% for prevalence and/or 20ng/ml for coproantigen concentration) was also significantly higher (p<0.05) in Group C than in untreated animals (Group A). The survey showed that most dairy farmers are unaware of the existence of F. hepatica infection on their farms, and treatments, when given, are administered without prior diagnosis. Treatment with TCBZ administered only at drying off did not show advantages over other measures including no treatment, or treatment with other benzimidazoles. Consequently, TCBZ should only be used to treat individual animals after correct diagnosis of the infection, and correct management measures taken to control re-infection. 相似文献
993.
Yabsley MJ McKibben J Macpherson CN Cattan PF Cherry NA Hegarty BC Breitschwerdt EB O'Connor T Chandrashekar R Paterson T Perea ML Ball G Friesen S Goedde J Henderson B Sylvester W 《Veterinary parasitology》2008,151(2-4):279-285
To identify the tick-borne pathogens in dogs from Grenada, we conducted a serologic survey for Ehrlichia canis in 2004 (104 dogs) and a comprehensive serologic and molecular survey for a variety of tick-borne pathogens in 2006 (73 dogs). In 2004 and 2006, 44 and 32 dogs (42.3% and 43.8%) were seropositive for E. canis, respectively. In 2006, several tick-borne pathogens were identified by serology and PCR. DNA of E. canis, Anaplasma platys, Babesia canis vogeli, Hepatozoon canis, and Bartonella sp. were identified in 18 (24.7%), 14 (19.2%), 5 (7%), 5 (7%), and 1 (1.4%) dogs, respectively. Six (8.2%) dogs were seropositive for Bartonella vinsonii subsp. berkhoffii. All dogs were seronegative and PCR-negative for Rickettsia spp. Coinfection with two or three pathogens was observed in eight dogs. Partial 16S rRNA E. canis and A. platys sequences were identical to sequences in GenBank. Partial 18S rRNA gene sequences from the Grenadian H. canis were identical to each other and had one possible mismatch (ambiguous base) from H. canis detected from Spain and Brazil. Grenadian B. c. vogeli sequences were identical to B. c. vogeli from Brazil and Japan. All of the detected pathogens are transmitted, or suspected to be transmitted, by Rhipicephalus sanguineus. Results of this study indicate that dogs from Grenada are infected with multiple tick-borne pathogens; therefore, tick-borne diseases should be included as differentials for dogs exhibiting thrombocytopenia, leukopenia, fever, or lethargy. One pathogen, E. canis, is also of potential public health significance. 相似文献
994.
Woclawek-Potocka I Piskula MK Bah M Siemieniuch MJ Korzekwa A Brzezicka E Skarzynski DJ 《The Journal of reproduction and development》2008,54(5):358-363
The present study compared the changes in isoflavones (daidzein and genistein) and their metabolite (equol and para-ethyl-phenol) concentrations in the blood plasma of cyclic and pregnant heifers after feeding with soy bean. Twelve healthy heifers were divided into three groups: cyclic heifers (days 8-12 of the estrous cycle; control group; n=4), an early pregnancy group (2 months pregnant; n=4) and a late pregnancy group (8 months pregnant; n=4). All heifers were fed a single dose of 2.5 kg of soy bean and then blood samples were taken from the jugular vein for 8 h at predetermined intervals. The concentrations of soy bean-derived isoflavones and their active metabolites were measured in the blood plasma on an HPLC system. In the blood plasma of the early- and late-pregnant heifers, we found lower concentrations and time-dependent decreases in daidzein and genistein in comparison to cyclic heifers (P<0.05). Moreover, we noticed significant increases of equol and para-ethyl-phenol in the blood plasma of the early-pregnant heifers (P<0.05). In contrast, in the blood plasma of the late-pregnant heifers, we did not find an increase in the isoflavone metabolite concentrations compared with the early-pregnant heifers (P>0.05). In conclusion, physiological status (cyclicity or pregnancy) of the females influenced the concentrations of isoflavone metabolites in the blood plasma of the heifers. The stage of pregnancy affects isoflavone absorption, biotransformation and metabolism differently and results in higher concentrations of active metabolites of isoflavones during early pregnancy in comparison to their lower concentrations during late pregnancy. Therefore, we surmise that cows are more sensitive to active isoflavone metabolite actions during early pregnancy than cyclic heifers and heifers in late pregnancy. 相似文献
995.
Eighteen multiparous Zebu cows in their third lactation and their calves were randomly allocated to three suckling periods, up to 3, 4 or 5 months of age of the calf. The cows were individually fed natural hay, cottonseed cake and molasses. At 2 months of age, all calves were separated from their mothers, and were offered cottonseed cake mixed with molasses and Mucuna hay individually. The calves stimulated milk ejection by suckling 30 seconds and suckled the residual milk for 45 minutes after milking. The dry matter intake of cows (3.68, 3.29 and 3.31% of body weight) and calves (2.88, 2.80 and 2.55% of body weight) for suckling up 3, 4 and 5 months of age, respectively, was not significantly affected by treatment and neither was the growth rate of the calves (178, 157 and 149 g/d for 3, 4 or 5 months suckling period, respectively). Cows suckling their calves up to 5 months had significantly higher milk yield and higher amount of saleable milk (1.97, 2.93 and 3.69 kg/cow/d for 3, 4 and 5 months suckling period, respectively). The fat content of the milk decreased with increasing length of the suckling period while the protein content was not affected. In conclusion, a suckling period of 5 months resulted in higher total milk production and higher amount of saleable milk but did not seem to have any effect on calf growth when the calves were supplemented. 相似文献
996.
997.
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
998.
Téguia A Mafouo Ngandjou H Defang H Tchoumboue J 《Tropical animal health and production》2008,40(1):5-10
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
999.
Shafarin MS Zamri-Saad M Khairani BS Saharee AA 《Tropical animal health and production》2008,40(5):335-340
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
1000.