全文获取类型
收费全文 | 486篇 |
免费 | 38篇 |
专业分类
林业 | 33篇 |
农学 | 15篇 |
基础科学 | 3篇 |
98篇 | |
综合类 | 29篇 |
农作物 | 26篇 |
水产渔业 | 67篇 |
畜牧兽医 | 192篇 |
园艺 | 16篇 |
植物保护 | 45篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 9篇 |
2021年 | 17篇 |
2020年 | 22篇 |
2019年 | 32篇 |
2018年 | 28篇 |
2017年 | 19篇 |
2016年 | 26篇 |
2015年 | 21篇 |
2014年 | 17篇 |
2013年 | 26篇 |
2012年 | 43篇 |
2011年 | 50篇 |
2010年 | 26篇 |
2009年 | 15篇 |
2008年 | 26篇 |
2007年 | 31篇 |
2006年 | 28篇 |
2005年 | 26篇 |
2004年 | 13篇 |
2003年 | 12篇 |
2002年 | 11篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有524条查询结果,搜索用时 312 毫秒
171.
Vezzani D Carbajo AE Fontanarrosa MF Scodellaro CF Basabe J Cangiano G Eiras DF 《Veterinary parasitology》2011,176(2-3):240-249
This study was aimed at understanding some aspects of the canine heartworm epidemiology in the southern distribution limit of the parasite in South America. With this objective, 19,298 blood samples of owned dogs from 65 localities of 13 municipalities of Buenos Aires Province were tested for Dirofilaria immitis circulating microfilariae and/or female antigens. The overall heartworm prevalence was 1.63% by microhematocrit tube technique (n=19,136), 3.65% by modified Knott (n=713), and 14.41% by antigen test kit (n=118). Microfilaremic dogs showed a median of 1933 microfilariae per millilitre (q1=375, q3=5625, n=100). Male dogs belonging to breeds of short hair and large size recorded significantly higher prevalences than the other categories. Also, the prevalence increased significantly with the age and only dogs younger than 12 months were not found infected. A clear decreasing trend of the annual prevalence was observed during the whole study period, from 3.91% in 2001 to 1.17% in 2006. D. immitis-infected dogs were detected in 32 localities of 9 municipalities (prevalence range: 0.2-6.7%). Generalized linear models were used to assess associations between heartworm prevalence and environmental variables. The resulting significant models were univariate and included variables related with soil cover and human population density. The best model predicted maximum heartworm prevalences around middle values of bare soil cover, and lower at high and low covers. According to our analyses, canine heartworm infection in urban temperate Argentina could be described as relatively low, endemic, and spatially heterogeneous. Host and environmental factors affecting heartworm transmission at local level were identified and discussed. 相似文献
172.
Do Nascimento VV Castro HC Abreu PA Oliveira AE Fernandez JH Araújo Jda S Machado OL 《Journal of agricultural and food chemistry》2011,59(9):4814-4821
The major Ricinus communis allergens are the 2S albumins, Ric c 1 and Ric c 3. These proteins contain a trypsin/α-amylase inhibitor family domain, suggesting that they have a role in insect resistance. In this study, we verified that Ric c 1 and Ric c 3 inhibited the α-amylase activity of Callosobruchus maculatus, Zabrotes subfasciatus, and Tenebrio molitor (TMA) larvae as well as mammalian α-amylase. The toxicity of 2S albumin was determined through its incorporation in C. maculatus larvae as part of an artificial diet. Bioassays revealed that 2S albumin reduced larval growth by 20%. We also analyzed the tridimensional structures of Ric c 1 and Ric c 3 by (a) constructing a comparative model of Ric c 1 based on Ric c 3 NMR structure and (b) constructing the theoretical structure of the Ric c 1-TMA and Ric c 3-TMA complexes. Our biological and theoretical results revealed that Ric c 1 and Ric c 3 are a new class of α-amylase inhibitors. They could potentially be used to help design inhibitors that would be useful in diverse fields, ranging from diabetes treatment to crop protection. 相似文献
173.
Stephen L. Winter Samuel D. Fuhlendorf Carla L. Goad Craig A. Davis Karen R. Hickman 《Strength and Conditioning Journal》2011,64(6):633-640
Patch burning is the deliberate application of fire to a management unit in a heterogeneous manner, resulting in the heterogeneous distribution of grazing animal impact. The application of patch burning typically has been discussed within a framework of imposing heterogeneity on a homogeneous landscape or management unit, yet most landscapes and management units are actually distinguished by an inherent level of heterogeneity. Within landscapes and management units, differing topography and soils interact to create patterns of contrasting patches, also known as topoedaphic sites. Thus, introduction of a heterogeneous disturbance such as patch burning on a landscape or management unit is more accurately described as the imposition of one layer of heterogeneity onto a pre-existing layer of heterogeneity. We examined effects of patch burning on vegetation structure and animal distribution across contrasting topographical sites in sand sagebrush (Artemisia filifolia Torr.) shrubland of the southern Great Plains in North America. Landscapes at our study site were characterized by an inherent amount of heterogeneity in vegetation structure due to variability in topoedaphic sites, and the patch burning treatment superimposed additional heterogeneity that was constrained by topoedaphic characteristics. Shrub-dominated sites were more dependent on patch burning for heterogeneity of vegetation structure than sites dominated by short grasses. Distribution patterns of cattle (Bos taurus) were not significantly different across treatments, though they followed patterns similar to previous studies. We demonstrated that heterogeneity was dependent on topoedaphic patterns and the application of patch burning management for heterogeneity was dependent on the inherent variability of a landscape. 相似文献
174.
Roshwalb S Gorman S Hurst S Bartges J Agarwal S Sommardahl C Odoi A Dhar MS 《Veterinary journal (London, England : 1997)》2011,190(1):173-175
Mouse and human Atp10c genes are strong candidates for changes in bodyweight and glucose homeostasis. Using comparative genomic analysis, a novel canine P4-type ATPase, ATP10C, was identified. Expression of ATP10C was compared between sex-matched lean (body condition score, BCS<8; n=7) and obese (BCS?8, n=8) client-owned dogs of comparable ages. Canine ATP10C is highly expressed in visceral and subcutaneous fat at approximately 3-fold levels compared to the omental adipose depot. There was a 5-fold significant increase (P<0.0001) in mRNA expression of ATP10C in dogs with a BCS?8. 相似文献
175.
Carla Rohrer Bley Dr Med Vet Hans Blattmann PHD Malgorzata Roos PHD Andrea Sumova Dipl Ing Barbara Kaser-Hotz Dr Med Vet Habil 《Veterinary radiology & ultrasound》2003,44(4):470-475
Radiation treatment requires a precise procedure for interfraction repositioning of the patient. The purpose of this study was to determine the accuracy of our fixation device in treatment position and to evaluate the setup accuracy with two different methods. The positioning data of 19 canine patients with tumors in the head region (oral, nasal, cerebral) treated with photon or proton irradiation were included in this study. The patients were immobilized by means of an individualized fixation device. Focus was set upon interfraction displacement with systematic and random components. In one method, treatment position was evaluated using single plane port radiographs and megavoltage x-rays. In the other method, two orthogonal CT-topograms were acquired to evaluate the precision of positioning of the patient in the immobilization device. Systematic and random displacements were calculated and presented as mean values with corresponding 95% confidence intervals. In spite of a difference between both methods, the positioning seemed to be accurate within the expected range. It seems that a safety margin of 3.7 mm would be enough for both methods to take into account systematic and random position variability in the fixation device, thereby preventing geometric inaccuracies of treatment delivery. The reported immobilization protocol provides accurate patient immobilization for photon and conformal proton radiation therapy. 相似文献
176.
Frozen beef liver fed at dietary levels of 5, 10, 15, 20, and 25% (dry weight) to postlarval Mucrobruchium rosenbergii was evaluated as a supplement to Mna Trout Chow No. 2. Final mean wet weights and yields of prawns fed 15, 20, and 25% beef liver were significantly higher than those of prawns that received 5 and 10% levels. Survival rates and food conversion ratios of dry matter fed to wet biomass produced were not significantly different among treatments. The suitability of 47 fresh and frozen fruits and vegetables as dietary supplements was tested. Fourteen fruits and vegetables sank and were readily consumed by prawns, and seven (fresh orange and sweet potato, and frozen banana, carrot tops, butternut squash, yellow squash, and turnip greens) were tested as supplements (10% dry weight of the total ration) to trout chow and 15% beef liver. There were no significant differences ( P < 0.05) in final mean weight, survival, yield, or food conversion ratio. Pigmentation of prams fed carrot tops or turnip greens was enhanced. No significant differences in final mean weight, yield, or survival were found when frozen banana was evaluated at levels of 0, 5,10,15, and 20% as a supplement to trout chow and 15% beef liver. Food conversion ratios for prawns fed 15 and 20% levels of banana were not different from those fed 10%, but were significantly higher than for prawns fed the 0 and 5% levels. Thus, a diet of Purina Trout Chow No. 2 plus 15% beef liver gives good results with postlarval M. rosenbergii in aquaria. Largescale testing and an economic analysis are needed to determine if this diet is practical for commercial prawn nurseries. 相似文献
177.
Vasilopulos RJ Rickard LG Mackin AJ Pharr GT Huston CL 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2007,21(2):352-355
BACKGROUND: Giardia duodenalis is an intestinal flagellated protozoan that affects many mammalian species often causing severe diarrheal disease. Several different genotypes have been identified (Assemblages A-G). Most isolates recovered from domestic cats have been assigned to either Assemblage A, the zoonotic form of the parasite, or Assemblage F, identified thus far only in cats. Genotypic variation within G. duodenalis may influence clinical presentation and course of disease. Therefore, host-adapted genotypes may not be responsible for diarrheal disease (eg, Assemblage F in cats). HYPOTHESIS: Multiple Giardia genotypes will be present in domestic cats, including Assemblage F, which will not be correlated with clinical signs. ANIMALS: 250 domestic cats from eastern Mississippi and northwestern Alabama. METHODS: Prevalence survey. Fecal samples evaluated for cysts using a centrifugation concentration technique and a commercially available direct immunoflourescent antibody kit. Giardia isolates were characterized by PCR amplification and sequencing of the glutamate dehydrogenase gene. RESULTS: Both Assemblage A-I (6/17) and Assemblage F (11/17) were identified. Although Assemblage was significantly associated with age and housing, no association was detected between Assemblage and a variety of other factors including the presence of gastrointestinal signs (acute vomiting, diarrhea, and constipation). CONCLUSIONS AND CLINICAL IMPORTANCE: The presence of diarrhea in domestic cats with Giardia cannot be used as a predictor of the presence of zoonotic genotypes in animals within the study area. Although Assemblage A was associated with age and housing, veterinarians should consider any isolation of Giardia from domestic cats as potentially zoonotic. 相似文献
178.
Molecular characterization of Cryptosporidium and Giardia isolates from cattle from Portugal 总被引:1,自引:0,他引:1
Mendonça C Almeida A Castro A de Lurdes Delgado M Soares S da Costa JM Canada N 《Veterinary parasitology》2007,147(1-2):47-50
Fecal samples from 291 calves and 176 adult cattle in Northern Portugal were screened for Cryptosporidium and Giardia using a formalin-ethyl acetate concentration method. Acid-fast staining techniques for Cryptosporidium oocyst identification and direct microscopic observation of fecal smears for Giardia cyst identification were performed so as immunofluorescence microscopy examination. Polymerase chain reaction methods were employed to determine the genotype of each isolate. Molecular characterization was performed using amplification and sequencing of the hsp70 and 18SrRNA genes of Cryptosporidium and beta-giardin gene and glutamate dehydrogenase for assemblage determination of Giardia duodenalis. Seventy-four out of 291 calves (25.4%) and 8 out of 176 adult bovines (4.5%) were positive for Cryptosporidium. Forty-one out of 291 calf samples (14.1%) and 1 out of 176 adults samples (0.57%) were positive for Giardia. From the Cryptosporidium positive samples we obtained 63 isolates from calves samples and 7 isolates from adult samples. Additionally, Giardia was isolated in 13 out of 41 positive samples from calves and it was also possible to isolate Giardia from the positive adult sample. Molecular characterization of the Cryptosporidium and Giardia isolates showed us that C. parvum and G. duodenalis assemblage E were the prevalent species. C. parvum may infect humans, representing a potential public health risk. On the other hand, the assemblages B and A2 of Giardia, previously described in humans, were here identified in cattle. Further studies will be needed for determine the importance of cattle as carrier of zoonotic assemblages of G. duodenalis. 相似文献
179.
180.