全文获取类型
收费全文 | 378篇 |
免费 | 32篇 |
国内免费 | 1篇 |
专业分类
林业 | 14篇 |
农学 | 4篇 |
基础科学 | 4篇 |
53篇 | |
综合类 | 66篇 |
农作物 | 9篇 |
水产渔业 | 20篇 |
畜牧兽医 | 225篇 |
园艺 | 1篇 |
植物保护 | 15篇 |
出版年
2023年 | 3篇 |
2021年 | 4篇 |
2020年 | 7篇 |
2019年 | 6篇 |
2018年 | 5篇 |
2017年 | 11篇 |
2016年 | 14篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 16篇 |
2012年 | 26篇 |
2011年 | 19篇 |
2010年 | 6篇 |
2009年 | 9篇 |
2008年 | 10篇 |
2007年 | 10篇 |
2006年 | 12篇 |
2005年 | 13篇 |
2004年 | 8篇 |
2003年 | 18篇 |
2002年 | 10篇 |
2001年 | 12篇 |
2000年 | 10篇 |
1999年 | 17篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1995年 | 4篇 |
1993年 | 3篇 |
1992年 | 12篇 |
1991年 | 11篇 |
1990年 | 13篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 9篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1979年 | 3篇 |
1977年 | 8篇 |
1974年 | 5篇 |
1972年 | 6篇 |
1970年 | 3篇 |
1968年 | 2篇 |
1967年 | 2篇 |
1966年 | 3篇 |
1957年 | 2篇 |
1941年 | 2篇 |
1938年 | 2篇 |
排序方式: 共有411条查询结果,搜索用时 937 毫秒
81.
Intensity of browsing on trees and shrubs under experimental variation of cattle stocking densities in southern Bolivia 总被引:1,自引:0,他引:1
Svenja Marquardt Alfredo Marquez Hlne Bouillot Stephan G. Beck Andrea C. Mayer Michael Kreuzer Humberto Alzrreca A. 《Forest Ecology and Management》2009,258(7):1422-1428
Mountain forests are traditionally used for cattle grazing during the dry season in southern Bolivia. To evaluate browsing intensity and damage to young trees and shrubs, a forest grazing area was monitored for about 3 months in both 2006 and 2007. Three similar paddocks of about 3 ha each, consisting of grassland and forest in a ratio of about 1:3 were stocked with 0.9, 1.6 and 2.6 tropical livestock units per ha (equivalents of 250 kg of body weight), reflecting low, medium and high stocking densities. Six 5 m × 5 m plots were mapped out within each paddock in 2006. Three additional plots per paddock were added in 2007. Within plots, the individuals of 18 woody species were coded and evaluated weekly for intensity of browsing. Intensity was quantified using five-scale categories reflecting the proportions of plant tissue removed (0 = no browsing, 1 = 1–25%, 2 = 26–50%, 3 = 51–75% and 4 = 76–100%). Across all plant species, the average category of browsing intensity, as determined in the post-grazing evaluation, was affected (P < 0.001) by stocking density. Browsing intensity increased in an approximately linear manner from 1.58 to 2.18 and 2.77 with low, medium and high stocking density, respectively. There was no significant difference between years. Most woody species followed the same general response pattern to stocking density, although some species were only noticeably browsed at high stocking density while a few others were intensively browsed at all stocking densities. The onset of browsing on woody species was observed only after some weeks had passed, indicating that herbaceous plants were preferred as a forage resource. The proportion of fatally damaged individuals, as assessed about 8 months after grazing in 2006, were 10.6%, 8.6% and 11.4% for low, medium and high stocking density, respectively. The percentage of completely browsed individuals increased with stocking density, but 80% of those plant individuals recovered following a resting period of 8 months. However, although most woody species recovered from browsing and fatal damage was infrequent, long-term changes in woody plant species composition and structure caused by grazing cannot be excluded. High stocking density in particular may reduce the vigour of heavily browsed species. 相似文献
82.
A comparison of monitoring systems used for Ceratitis species (Diptera: Tephritidae) in South Africa
For 16 years a bucket-type trap known as the Sensus fruit fly trap has been used to monitor three fruit fly pest species Ceratitis capitata, Ceratitis rosa and Ceratitis cosyra in South African fruit industries. The relative efficiencies of lures sold for monitoring fruit flies with the Sensus trap in South Africa were determined in field experiments where laboratory-reared C. capitata, C. rosa and C. cosyra were released in a mango orchard within a few metres of Sensus traps containing either Capilure (trimedlure or tert-butyl 4 (or 5) -chloro-2-methylcyclohexane carboxylate), Ceratitislure (protein hydrolysate plus β-caryophyllene) or Questlure (protein hydrolysate plus plant extracts). When using 12-day-old flies, Capilure caught 3 times more C. capitata males than C. rosa males and this difference was more extreme when 3-day-old flies were released. Ceratitislure caught significantly more 12-day-old C. cosyra males than 12-day-old C. capitata males, but the difference was reversed when 3-day-old flies were compared. Questlure showed the least differences between species and age but recovered the lowest proportion of released species. Further comparisons were conducted in an orchard with wild flies using other known attractants in larger yellow Probodelt bucket traps. Capilure caught more male C. capitata than BioLure Fruit Fly 3-component, but BioLure 2-component (trimethylamine and ammonium acetate) was more effective than Questlure for C. capitata females. The 3-component lure was also more effective than both Capilure and Questlure for male and female C. rosa, respectively. Ceratitislure was the most effective lure for male C. cosyra flies and BioLure 3-component was more effective than Ceratitislure and Questlure for female C. cosyra flies. The intervention threshold of 4 flies/trap/week previously used in citrus with Capilure for C. rosa was lowered to 2 C. rosa/trap/week when using the Sensus trap due to the lower sensitivity of this trap-lure combination found for C. rosa in this study. The 3-component lure, or the 2-component combination of trimethylamine and ammonium acetate in a ratio of 1:8 in the Sensus trap capsule, would be more effective for both sexes of all three Ceratitis species than the Questlure that is currently being used. 相似文献
83.
84.
Ana C. Neves Juracy CB. Santos Júnior Rodrigo L. Marucio Monica Midon Stelio PL. Luna 《Veterinary anaesthesia and analgesia》2017,44(2):375-378
Objective
To evaluate three volumes of lidocaine for spermatic cord block to perform castration in cattle.Study design
Randomized blinded clinical study.Animals
Thirty mixed-breed Nellore cattle, aged 28–40 months and weighing 395 ± 21 (352–452) kg [mean ± standard deviation (range)].Methods
Cattle were restrained in a chute and allowed to stand without sedation. Three milliliters of 2% lidocaine without epinephrine were infiltrated subcutaneously at each site of scrotal incision in all animals. The animals were allocated to three groups of 10 animals each. Lidocaine 2% was injected into each spermatic cord using a volume of 2, 3 or 4 mL in groups A, B, or C, respectively. The total volumes of lidocaine used were 10, 12, and 14 mL in groups A, B, and C, respectively. The duration of surgery and the retraction of the testicle (scored as positive or negative according to retraction of the testicle) during the procedure were recorded. The data were statistically analyzed by one-way anova followed by Tukey’s and chi-square tests. Differences were considered significant when p < 0.05.Results
The mean surgical time was shorter in group C than in groups A and B (p < 0.001). In groups A, B and C, 90%, 60% and 10% of the animals showed retraction of the testicle, respectively. Fewer animals retracted the spermatic cord in group C than in group A (p = 0.002) and B (p = 0.02).Conclusions and clinical relevance
Optimal spermatic cord block was achieved by injection of 4 mL of 2% lidocaine 5 minutes before castration and following incisional infiltration of lidocaine, in adult cattle weighing about 400 kg. 相似文献85.
SM Gonzalez CB da Silva AG Lindquist I Bufalo F Morotti LA Lisboa M Seneda 《Reproduction in domestic animals》2017,52(5):836-841
The goal of this study was to determine the distribution of pre‐antral follicles in the ovarian parenchyma of mares. For Experiment 1, each ovary was cut longitudinally at the greater curvature, performing two hemiovaries. After that, six fragments from each hemiovary were obtained, resulting in 12 fragments, which were divided into the innermost region of the parenchyma, the middle region and the outermost region. All the three obtained sections were cut transversally to obtain two fragments from each one. For Experiment 2, each ovary also submitted to a longitudinal cut on the greater curvature, forming two hemiovaries. Each hemiovary was sectioned into four symmetrical fragments, resulting in eight fragments per ovary. The fragments were related as being near to or far from the ovulatory fossa. The fragments of both experiments were immediately fixed in Carnoy for 12 hr and kept in 70% ethanol for 24 hr. Follicles were classified according to the stages of development and for morphological integrity according to oocyte morphology and granulosa cells. After the histological assessment, a total of 1,130 follicles were visualized from Experiment 1, being 1,054 (93.3%) primordial follicles and 76 (4.7%) follicles in development. The innermost region had the highest percentage of pre‐antral follicles compared to the other regions (p < .05). The middle and outermost regions showed higher percentages of intact primordial and developing follicles than the innermost region (p < .05). Considering Experiment 2, 938 follicles were found, being 894 (95.3%) primordial and 44 (4.7%) follicles in development. The region near the ovulatory fossa presented higher (58.7%; 551 of 938) follicular concentration compared to the region far from the ovulatory fossa (41.3%; 387 of 938; p < .05). As a conclusion, distribution of pre‐antral follicles in the equine ovary has a specific pattern through the parenchyma. Also, the follicular integrity differed in the studied ovarian areas. 相似文献
86.
Beck JJ 《Journal of agricultural and food chemistry》2012,60(5):1153-1157
As the sophistication and sensitivity of chemical instrumentation increase, so does the number of applications. Correspondingly, new questions and opportunities for systems previously studied also arise. As with most plants, the emission of volatiles from agricultural products is complex and varies among commodities. Volatiles are indicative of characteristics such as food quality, cultivar type, phenological stage, and biotic and abiotic stressors; thus, their systematic and accurate evaluation is important. Early volatile analyses entailed removal of the sample matrix in question, transport to the laboratory, and subsequent investigation. More recently, scientists are moving the laboratory to the field to obtain realistic emission patterns of the sample in its natural environment. This perspective proposes that a methodical and collaborative approach to the complex relationship between volatiles and agricultural commodities and their various phenological stages, oxidative degradation products, and fungal contamination is needed in order to fully comprehend the sample and associated relationships as a whole. These methodical approaches should incorporate both in situ and ex situ investigations of the sample. Ultimately, there exists an opportunity for development of methodologies that integrate both laboratory- and field-based collection of volatiles to explore and address the complex biological interactions of agricultural systems. 相似文献
87.
Gregorini P Gunter SA Bowman MT Caldwell JD Masino CA Coblentz WK Beck PA 《Journal of animal science》2011,89(11):3824-3830
Two complementary experiments were completed to assess short-term foraging dynamics, diet quality, and ruminal degradation kinetics of herbage consumed by steers with 3 levels of herbage depletion. Experiment 1 was a behavioral study in which 2 ruminally cannulated steers were allocated to grazing scenarios simulating 3 levels of herbage depletion. These treatments included an ungrazed sward (control), as well as medium and high levels of herbage depletion. Grazing scenarios were sampled for sward surface height and amount of green leaf and stem before being grazed. Foraging dynamics were determined through measurements of bite rate, bite depth, eating step rate, eating distance, potential area consumed while grazing, and bites and intake per eating step. Also, quality of potential herbage consumed was estimated from hand-plucked herbage. In Exp. 2, ruminal degradation kinetics of DM for samples of herbage consumed (masticate) by steers during Exp. 1 were assessed in situ using 5 ruminally cannulated steers. The immediately soluble, degraded, and undegraded DM fractions were determined. The DM disappearance rate and lag times were determined from a nonlinear regression model, and the effective degradability of DM was calculated. Herbage depletion resulted in increased eating steps/minute, as well as the potential area harvested while grazing (P < 0.05) and reduced herbage intake/eating step (P < 0.05). Neither the herbage potentially consumed nor the ruminal degradation kinetics was affected by extent of depletion (P > 0.05). Under these experimental conditions, steers adapted their foraging dynamic and were able to sustain diet quality in the short term. These results imply that behavioral adaptations would make diet quality less sensitive to certain levels of herbage depletion. 相似文献
88.
Habrun B Račić I Beck R Budimir A Benić M Kompes G Spičić S Cvetnić Z 《Acta veterinaria Hungarica》2011,59(4):419-425
Methicillin-resistant Staphylococcus aureus (MRSA) have emerged worldwide and have become resistant to a variety of antibiotics. MRSA colonisation in pigs was first reported from the Netherlands in 2005, where pigs were implicated as a source of human MRSA infections (Voss et al., 2005). This paper presents the first report on the presence of MRSA on large pig breeding farms in Croatia, together with the determination of the mecA gene, the results of spa typing and susceptibility to commonly used antimicrobials. Dust samples (7-11 per farm) were collected from eight large pig farms in Croatia. Of the total 68 swabs, the mecA gene was detected in 24 isolates growing on the MRSA agar. All isolates were resistant to oxacillin, tetracycline and streptomycin, and susceptible only to vancomycin, while 92% of the strains were susceptible to ciprofloxacin. Genotyping of the MRSA strains was performed by spa typing, and revealed t011 (n = 17), t034 (n = 5) and t1451 (n = 2). The results presented here predict that MRSA is present on a large number of pig farms in Croatia. 相似文献
89.
90.