全文获取类型
收费全文 | 161篇 |
免费 | 13篇 |
专业分类
林业 | 11篇 |
农学 | 5篇 |
40篇 | |
综合类 | 22篇 |
农作物 | 13篇 |
水产渔业 | 6篇 |
畜牧兽医 | 65篇 |
园艺 | 1篇 |
植物保护 | 11篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 5篇 |
2020年 | 5篇 |
2019年 | 5篇 |
2018年 | 5篇 |
2017年 | 5篇 |
2016年 | 4篇 |
2015年 | 2篇 |
2014年 | 6篇 |
2013年 | 8篇 |
2012年 | 18篇 |
2011年 | 19篇 |
2010年 | 8篇 |
2009年 | 5篇 |
2008年 | 12篇 |
2007年 | 10篇 |
2006年 | 10篇 |
2005年 | 7篇 |
2004年 | 7篇 |
2003年 | 12篇 |
2002年 | 10篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1997年 | 1篇 |
1994年 | 1篇 |
排序方式: 共有174条查询结果,搜索用时 359 毫秒
71.
Tina Birk Jensen Anders Ringgaard Kristensen Nils Toft Niels Peter Baadsgaard Sren
stergaard Hans Houe 《Preventive veterinary medicine》2009,89(3-4):237-248
The implementation of an effective control strategy against disease in a finisher herd requires knowledge regarding the disease level in the herd. A Bayesian network was constructed that can estimate risk indexes for three cause-categories of leg disorders in a finisher herd. The cause-categories of leg disorders were divided into infectious causes (arthritis caused by infectious pathogens), physical causes (e.g. fracture and claw lesions), and inherited causes (osteochondrosis). Information about the herd (e.g. the herd size, floor type and number of suppliers) and information about individual pigs (e.g. results from diagnostic tests) were used to estimate the most likely cause of leg disorders at herd level. As information to the model originated from two different levels, we used an object-oriented structure in order to ease the specification of the Bayesian network. Hence, a Herd class and a Pig class comprised the basic components of the object-oriented structure. The causal structure of the model was based on evidence from published literature. The conditional probabilities used in the model were elicited from experts within the field and from the published literature. To illustrate the behaviour of the model, we investigated the value of different levels of evidence in two fictitious herds with different herd characteristics related to the risk of leg disorders (e.g. purchase policy, production type and the stocking density in pens). The model enabled us to demonstrate the value of performing systematic collection of additional information (i.e. clinical, pathological and bacteriological examination) when identifying causes of leg disorders at herd level. 相似文献
72.
Wilson BD Ii M Park KW Suli A Sorensen LK Larrieu-Lahargue F Urness LD Suh W Asai J Kock GA Thorne T Silver M Thomas KR Chien CB Losordo DW Li DY 《Science (New York, N.Y.)》2006,313(5787):640-644
Axonal guidance and vascular patterning share several guidance cues, including proteins in the netrin family. We demonstrate that netrins stimulate proliferation, migration, and tube formation of human endothelial cells in vitro and that this stimulation is independent of known netrin receptors. Suppression of netrin1a messenger RNA in zebrafish inhibits vascular sprouting, implying a proangiogenic role for netrins during vertebrate development. We also show that netrins accelerate neovascularization in an in vivo model of ischemia and that they reverse neuropathy and vasculopathy in a diabetic murine model. We propose that the attractive vascular and neural guidance functions of netrins offer a unique therapeutic potential. 相似文献
73.
Dong TT Zhao KJ Gao QT Ji ZN Zhu TT Li J Duan R Cheung AW Tsim KW 《Journal of agricultural and food chemistry》2006,54(7):2767-2774
Danggui Buxue Tang (DBT), a Chinese medicinal decoction that is commonly used as a dietary supplement in treating woman with menopausal irregularity, contains two herbs: Radix Astragali (Huangqi) and Radix Angelicae Sinensis (Danggui). The ratio of Radix Astragali and Radix Angelicae Sinensis used in DBT should be 5:1 as described in China in 1247 A.D.; however, the rationale of this formula has not been given. Here, the chemical and biological properties of DBT, prepared from different ratios of the drugs, were determined. Significantly, higher amounts of Radix Astragali-derived astragaloside IV, calycosin, and formononetin and Radix Angelicae Sinensis-derived ferulic acid were found in DBT with Radix Astragali and Radix Angelicae Sinensis in a 5:1 ratio. By using the biological effects of DBT in stimulating osteoblast proliferation, estrogen promoter activation, and anti-platelet aggregation activity, the drug ratio of 5:1 produced the best effects. In addition, the use of ethanol-treated Radix Angelicae Sinensis enhanced the efficacy of DBT, and the treatment further increased the solubilities of chemical constituents. By analyzing the correlation of chemical and biological results, several chemicals showed positive correlation with DBT-induced bioactivities. The current results support the ancient formulation of DBT, and the identified chemicals could serve as markers for quality control of DBT. 相似文献
74.
OBJECTIVES: To evaluate compliance with the national recommendation on supplemental iron to all pregnant women in Denmark and to explore differences between compliers and non-compliers with respect to dietary habits and other lifestyle factors. DESIGN: Intake of supplemental iron from pure iron supplements and from multivitamin and mineral preparations was estimated in mid-pregnancy. SETTING: Nationwide cohort study, the Danish National Birth Cohort (DNBC), comprising more than 100,000 women recruited in early pregnancy. SUBJECTS: Information on diet and dietary supplements was available for 54,371 women. Of these, information on lifestyle factors was available for 50,902 women. RESULTS: A high compliance with the recommendation was found, as approximately 77% of the women reported use of iron supplements during pregnancy. However, many of the compliers did not obtain the recommended doses of iron, which can partly be explained by the lack of iron preparations of appropriate doses available on the Danish market. Compliance with the recommendation was associated with age above 20 years, primiparity, body mass index<30 kg m- 2, non-smoking and long education. No major differences were seen in dietary intake between compliers and non-compliers.ConclusionOverall, a high compliance rate was found among participants of the DNBC but a clarification on daily dose is needed, and more concern should be paid to vulnerable groups such as young, smoking women and women with no or short education. 相似文献
75.
Parducci L Jørgensen T Tollefsrud MM Elverland E Alm T Fontana SL Bennett KD Haile J Matetovici I Suyama Y Edwards ME Andersen K Rasmussen M Boessenkool S Coissac E Brochmann C Taberlet P Houmark-Nielsen M Larsen NK Orlando L Gilbert MT Kjær KH Alsos IG Willerslev E 《Science (New York, N.Y.)》2012,335(6072):1083-1086
It is commonly believed that trees were absent in Scandinavia during the last glaciation and first recolonized the Scandinavian Peninsula with the retreat of its ice sheet some 9000 years ago. Here, we show the presence of a rare mitochondrial DNA haplotype of spruce that appears unique to Scandinavia and with its highest frequency to the west-an area believed to sustain ice-free refugia during most of the last ice age. We further show the survival of DNA from this haplotype in lake sediments and pollen of Tr?ndelag in central Norway dating back ~10,300 years and chloroplast DNA of pine and spruce in lake sediments adjacent to the ice-free And?ya refugium in northwestern Norway as early as ~22,000 and 17,700 years ago, respectively. Our findings imply that conifer trees survived in ice-free refugia of Scandinavia during the last glaciation, challenging current views on survival and spread of trees as a response to climate changes. 相似文献
76.
Patricia M. Fraser Michael H. Beare Ruth C. Butler Tina Harrison-Kirk Jacqueline E. Piercy 《Pedobiologia》2003,47(5-6):870-876
77.
Chemical analysis of Radix Astragali (Huangqi) in China: a comparison with its adulterants and seasonal variations 总被引:8,自引:0,他引:8
Ma XQ Shi Q Duan JA Dong TT Tsim KW 《Journal of agricultural and food chemistry》2002,50(17):4861-4866
Radix Astragali (root of Astragalus; Huangqi) is a popular traditional Chinese medicine, and Astragalus membranaceus and A. membranaceus var. mongolicus are two commonly used species; however, there are many Astragalus species that could act as adulterants of Radix Astragali. To find the chemical composition of Radix Astragali, the main constituents including flavonoids, saponins, polysaccharides, amino acids, and trace elements were determined in two Radices Astragali, A. membranaceus and A. membranaceus var. mongolicus, and its eight adulterants, Astragalus propinquus, Astragalus lepsensis, Astragalus aksuensis, Astragalus hoantchy, Astragalus hoantchy subsp. dshimensis, Astragalus lehmannianus, Astragalus sieversianus, and Astragalus austrosibiricus. The results showed that the amounts of main constituents such as isoflavonoids and astragalosides varied in different species. In distinction, A. membranaceus and A. membranaceus var. mongolicus contained a higher amount of astragaloside I and IV. In addition, the main constituents of A. membranaceus var.mongholicus changed according to seasonal variation and age of the plant. The chemical composition of different species of Astragalus would provide useful information for the quality control of Radix Astragali. 相似文献
78.
To assess the effects of clearcutting on snowshoe hare (Lepus americanus) relative abundance, we surveyed pellets in 1 m2 circular plots and, vegetation and browse surveys in 4.5 m2 circular plots among four different aged clearcut (30, 20, 10, 5 years post-harvest) and mature forests (>150 years old) in central Labrador, Canada. Data were modelled at three grain sizes: transect (4400 m2), plot (314 m2) and subplot scales (4.5 m2). Betula papyrifera, distance from mature forest edge, tree and herb cover as well as remotely sensed forest inventory data were used as predictors for hare pellets. We found pellet abundance was 5 and 37 times greater (new and old pellets, respectively) in clearcut stands 30 years old than the next highest in 20 year old cuts. There were few hare pellets in the remaining stand ages. B. papyrifera was the most proportionately used browse species and most important of our fine-detailed vegetation in predicting hare pellets. The coarse-detailed, forest inventory and topographic data better predicted hare pellets than the fine-detailed vegetation data. 相似文献
79.
Multivariate principal component analysis to evaluate growth performances in Malabari goats of India
Valsalan Jamuna Sadan Tina Venketachalapathy Thirupathy 《Tropical animal health and production》2020,52(5):2451-2460
Tropical Animal Health and Production - Evaluation of growth performances in Malabari goats was done with body weight and major morphometric traits, viz. body height, body length and chest girth at... 相似文献
80.
Tommaso Vezzosi Caterina Puccinelli Rosalba Tognetti Tina Pelligra Simonetta Citi 《Veterinary radiology & ultrasound》2020,61(5):507-511
Thoracic radiography is a useful technique for the evaluation of cardiac dimensions, especially when echocardiography is not possible. The vertebral left atrial size (VLAS) has recently been proposed as a new radiographic method for quantifying left atrial dimensions in dogs. The aims of this retrospective, reference interval, observational study were to describe values for VLAS in a group of healthy adult dogs and to compare intraobserver and interobserver agreement for VLAS versus vertebral heart score (VHS) methods. Thoracic radiographs of 80 healthy adult dogs were evaluated. Normal left atrial size was determined based on an echocardiographic left atrial‐to‐aorta ratio < 1.6. The VLAS and vertebral heart score values were measured from right lateral radiographs. The correlations between VLAS, the vertebral heart score, and the left atrial‐to‐aorta ratio were evaluated. The effects of body weight, sex, and age were also tested using regression analyses. The median value of VLAS were 1.9, with a reference interval of 1.4‐2.2. A positive correlation was found between VLAS and vertebral heart score values (r = 0.53; P < .0001). No effect of body weight, sex, and age on VLAS was detected. Excellent intraobserver and interobserver agreements were found for both VLAS and vertebral heart score methods (intraclass correlation coefficients ≥ 0.91). Findings from this sample of healthy dogs indicated that VLAS is a repeatable radiographic method for quantifying left atrial size. Further studies are warranted to evaluate this measure in clinically affected dogs. 相似文献