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   308篇
  免费   29篇
林业   11篇
农学   6篇
  111篇
综合类   11篇
农作物   13篇
水产渔业   23篇
畜牧兽医   125篇
园艺   6篇
植物保护   31篇
  2023年   2篇
  2022年   6篇
  2021年   15篇
  2020年   13篇
  2019年   15篇
  2018年   11篇
  2017年   14篇
  2016年   20篇
  2015年   9篇
  2014年   17篇
  2013年   21篇
  2012年   24篇
  2011年   24篇
  2010年   7篇
  2009年   9篇
  2008年   23篇
  2007年   18篇
  2006年   20篇
  2005年   3篇
  2004年   10篇
  2003年   16篇
  2002年   7篇
  2000年   6篇
  1999年   6篇
  1997年   1篇
  1996年   2篇
  1993年   1篇
  1992年   2篇
  1989年   4篇
  1986年   1篇
  1985年   1篇
  1984年   1篇
  1983年   3篇
  1980年   2篇
  1978年   1篇
  1973年   1篇
  1954年   1篇
排序方式: 共有337条查询结果,搜索用时 250 毫秒
101.
Porcine coccidiosis caused by Isospora suis is one of the leading causes of neonatal diarrhea in suckling piglets. Currently the only registered drug for metaphylaxis is toltrazuril. To evaluate the effect of treatment on piglets from 7 Austrian farms without and 8 Austrian farms with toltrazuril application we examined oocyst excretion (including determination of oocysts per gram of feces; OPG), diarrhea (fecal score FS 1-4 with 3 and 4 being diarrhea), and general health (health score HS 1-4 with 3 and 4 describing poor health). Both groups included farms with different levels of hygiene. Samples from 265 litters without treatment, comprising 1588 individual samples, and 1548 samples from 258 treated litters were taken twice (around the 14th and the 21st day of life, respectively), examined by autofluorescence and, if positive, by McMaster counting. In both groups animals had less diarrhea and lower health scores during the second sampling but the treated piglets were always significantly healthier and had less diarrhea. The percentage of weaned piglets was higher in treated animals although this was not significant (p=0.052). In the first round of sampling 17.8% of the individual samples from untreated piglets were positive for oocysts (with a maximum prevalence on the 12-15th day of life) while in the treated piglets only 0.4% shed oocysts p<0.001). At the second sampling only 2.1% of the untreated animals and none of treated piglets excreted I. suis (p=0.083). Positive animals shed up to 8 × 10(3)OPG. There was an increased risk for infected piglets to develop diarrhea (odds ratio, OR 4.73) and poor health (OR 5.05) in untreated piglets, and poor hygiene without disinfection was identified as a risk factor for poor health (OR 1.90), diarrhea (OR 1.42) and oocyst excretion (OR 1.73). The risk of poor health (OR 2.89) and diarrhea (OR 1.44) was also increased for piglets under poor hygienic conditions receiving toltrazuril, so both metaphylaxis of coccidiosis and good hygiene are necessary to effectively control neonatal diarrhea. The costs of treatment are considerably lower than the estimated financial production losses. Therefore, treatment is recommended for farms where clinical coccidiosis is diagnosed.  相似文献   
102.
To evaluate the presence of Campylobacter spp. and related cdt genes, cloacal swabs were collected from 70 common teals (Anas crecca) and analyzed by culture methods and polymerase chain reaction. In addition, C. jejuni were examined also for the presence of wlaN gene. This is believed to be the first report of Campylobacter spp. in common teal and our results confirm the very common occurrence of C. jejuni (n=40) and C. coli (n=13) in waterfowls. Furthermore, the cdt genes were frequently present in both C. jejuni and C. coli isolated. Moreover, seven C. jejuni isolates carried also the wlaN gene which is presumably involved in the expression of ganglioside mimics in Guillain-Barré syndrome.  相似文献   
103.
This work aimed to compare methods for the formation of complexes of bixin and curcumin with β-cyclodextrin (β-CD) and to evaluate the stability of the complexes formed by these methods and their food applications. The stoichiometric relationship between curcumin and β-CD was 1:2 and that between bixin and β-CD was 1:1. Curcumin-β-CD and bixin-β-CD complexes formed by kneading, coprecipitation, and simple mixing were evaluated by differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), or nuclear magnetic resonance (NMR-H). For both curcumin and bixin, the best method of complexation was coprecipitation. Complexation of colorants with β-CD promoted an intensification of color and increased water solubility; however, stabilization in the presence of light occurred only for bixin. Application of curcumin-β-CD in cheese and yogurt and bixin-β-CD in the curd did not alter the initial characteristics of the products, which were sensorialy well accepted. Therefore, the complexation of these natural colorants with β-CD favors their use in low-fat foods, broadening the field of industrial application.  相似文献   
104.
It was recently reported that tetracycline could enhance the mobility of manure-derived Escherichia coli within saturated porous media (Walczak et al. (Water Research 45:1681-1690, 2011)). It was also shown, however, that E. coli from various sources could display marked variation in their mobility (Bolster et al. (Journal of Environmental Quality 35:1018-1025, 2009)). The focus of this research was to examine if the observed difference in the mobility of manure-derived tetracycline-resistant (tet(R)) and tetracycline-susceptible (tet(S)) E. coli strains was source-dependent. Specifically, E. coli were isolated from Lake Michigan, and the influence of tetracycline resistance on Lake Michigan-derived E. coli was investigated through column transport experiments. Additionally, a variety of cell morphology and surface properties were determined and related to the observed bacterial transport behavior. Our experimental results showed that, consistent with previous observations, the deposition rate coefficients of the tet(R)E. coli strain was ~20-100% higher than those of the tet(S)E. coli strain. The zeta potential of the tet(R)E. coli cells was ~25 mV more negative than the tet(S)E. coli cells. Because the surfaces of the E. coli cells and the quartz sands were negatively charged, the repulsive electrostatic double-layer interaction between the tet(R)E. coli cells and the quartz sands was stronger, and the mobility of the tet(R)E. coli cells in the sand packs was thus higher. The tet(R)E. coli cells were also more hydrophilic than the tet(S)E. coli cells. Results from migration to hydrocarbon phase (MATH) tests showed that about ~35% more tet(S)E. coli cells partitioned to the hydrocarbon phase. As it was previously shown that cell hydrophobicity could enhance the attachment of bacterial cells to quartz sand, the difference in cell hydrophobicity could also have contributed to the observed higher mobility of the tet(R)E. coli cells. The size of the tet(R) and tet(S)E. coli cells were similar, suggesting that the observed difference in their mobility was not size-related. Characterization of cell surface properties also showed that tet(R) and tetS E. coli cells differed slightly in cell-bound lipopolysaccharide contents and had distinct outer membrane protein profiles. Such difference could alter cell surface properties which in turn led to changes in cell mobility.  相似文献   
105.
Catecholamines seem to play a role in equine exercise physiology that is somewhat different from their role in human beings. In sport horses, a greater increase in plasma adrenaline (ADR) levels occurs in response to strenuous exercise as compared with human beings. However, it is not known whether this is true for breeds not specifically bred for sport. The aim of this study was to gather data on plasma catecholamine kinetics during exercise in a nonracing breed. We also attempted to evaluate the influence of the phases preceding the start of the exercise on the kinetics of these molecules. Four 2-year-old female Esperia ponies were made to perform a four-step exercise test on a treadmill. Blood samples were collected in the box (basal 1), in the treadmill room (basal 2), and at the conclusion of each step, using an automatic system. ADR and noradrenaline (NOR) levels were determined by high-pressure liquid chromatography. Results were analyzed using analysis of variance and the Student-Newman-Keuls test. As compared with basal 1, basal 2 showed a significant 19.6-fold increase for ADR and a 6.7-fold increase for NOR. The highest concentration was observed for both molecules at the end of the fourth step, with a significant 1.2-fold increase as compared with blood samples collected at basal 2 for ADR and a 2.4-fold increase for NOR. Therefore, in Esperia ponies, catecholamine showed a trend similar to that of Standardbreds and Thoroughbreds. The results reported in this study also revealed a marked increase in ADR in the phases preceding the beginning of physical activity. Therefore, the greater adrenergic activity in horses in response to exercise could be because of an anticipatory response.  相似文献   
106.
Fascioliasis, the zoonotic disease caused by the trematode Fasciola hepatica, is expanding worldwide, with a 17 million people at risk. Rodents, often recognized as a major source of zoonotic diseases, are affected by F. hepatica, with some species playing important roles in the disease epidemiology. The case reported here in a nutria or kiyá (Myocastor coypus) is the first documented case of F. hepatica in this species in Uruguay. Parasitic burden and total egg production detected are markedly higher than reported previously for this species, confirming its potential role as an effective reservoir and disseminator of liver flukes. Although further research is needed, nutria should be considered when designing effective control programs for fascioliasis.  相似文献   
107.
A method is described for the simultaneous determination of residues of five fungicides used for foliar treatment of apple and pear trees, and for postharvest application. After extraction, the mixture of these fungicides is cleaned-up on a ‘SEP PAK C18’ cartridge and the components determined by gas-liquid chromatography with electron-capture detection. The minimum detectable amounts in apples and pears, on a fresh weight basis, were 0.005mg kg−1 for vinclozolin, 0.010mg kg−1 for captan, folpet and iprodione, and 0.020 mg kg−1 for captafol. The percentage recovery for each fungicide (calculated by analysing four samples of untreated apples and pears, to which varying concentrations of each active ingredient had been added) varied for vinclozolin between 70.0 and 89.2, for captan between 72.0 and 83.8, for folpet between 73.0 and 93.0, for captafol between 70.8 and 91.8, and for iprodione between 75.1 and 97.1.  相似文献   
108.
A series of 1-(3-pyridyl)-1-substituted-but-3-yn-1-ols and some related compounds were synthesised and tested for antifungal activity against eight phytopathogenic fungi of different taxonomic classes. High activity was shown in particular against Sphaerotheca fuliginea on Cucumis sativus. The compounds containing aromatic substituents gave the best results, not only in protectant but also in systemic and eradicant tests. The quantitative structure-activity relationship suggests that steric effects play an important role in determining fungicidal activity.  相似文献   
109.
110.
During the period January 2004 to December 2005 four different ostrich farms were investigated to evaluate the presence of thermotolerant Campylobacter. A total of 150 ostriches were examined and all were found to be clinically healthy. Campylobacter spp. were isolated from 60/150 cloacal swabs. Among the isolates, 48 were identified as Campylobacter jejuni whereas the remainder were identified as Campylobacter coli. Campylobacter lari was not isolated. The ostriches, although apparently in a healthy body condition, can be considered, theoretically, as potential Campylobacter carriers.  相似文献   
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