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   382篇
  免费   28篇
  国内免费   1篇
林业   8篇
农学   9篇
基础科学   1篇
  58篇
综合类   54篇
农作物   5篇
水产渔业   7篇
畜牧兽医   239篇
园艺   9篇
植物保护   21篇
  2023年   3篇
  2022年   2篇
  2021年   6篇
  2020年   5篇
  2019年   8篇
  2018年   2篇
  2017年   9篇
  2016年   9篇
  2015年   6篇
  2014年   9篇
  2013年   14篇
  2012年   17篇
  2011年   23篇
  2010年   20篇
  2009年   11篇
  2008年   22篇
  2007年   28篇
  2006年   26篇
  2005年   11篇
  2004年   24篇
  2003年   25篇
  2002年   14篇
  2001年   6篇
  2000年   13篇
  1999年   8篇
  1998年   6篇
  1997年   6篇
  1996年   2篇
  1995年   3篇
  1994年   2篇
  1993年   4篇
  1992年   3篇
  1990年   3篇
  1989年   7篇
  1987年   5篇
  1986年   2篇
  1985年   4篇
  1982年   3篇
  1981年   3篇
  1979年   5篇
  1978年   2篇
  1977年   3篇
  1976年   2篇
  1973年   3篇
  1972年   4篇
  1970年   2篇
  1968年   2篇
  1947年   1篇
  1933年   1篇
  1886年   1篇
排序方式: 共有411条查询结果,搜索用时 15 毫秒
91.

Background

Large regions of central and eastern Europe are recognized as areas where tick-borne encephalitis virus (TBEV) is endemic, including countries neighbouring Denmark. It is therefore timely and relevant to determine if TBEV infections occur in Denmark. This study investigates the presence of antibodies against TBEV in a cross-section of the Danish canine population to assess the level of exposure to TBEV and possibly identify TBEV microfoci in Denmark.

Methods

Blood samples were collected from 125 dogs originating from five regions of Denmark between November 2005 and March 2006. Serum was tested by indirect ELISA. All positive and borderline samples were re-evaluated by neutralisation test (NT).

Results

The prevalence of TBEV serocomplex antibodies was 30% by ELISA and 4.8% by NT (with 100%-neutralising capacity). The island of Bornholm was the only area in Denmark with NT positive samples.

Conclusions

The island of Bornholm is an area with a high risk of encountering TBEV microfoci. The presence of TBEV serocomplex antibodies in many sentinel animals from other parts of Denmark points toward existence of other TBEV microfoci. Discrepancies found between ELISA and NT results stress the importance of careful evaluation of serological tests, when interpreting results.  相似文献   
92.
The total volatile basic nitrogen fraction (TVB-N) is often used as a quality parameter in the fish industry to assess spoilage. This parameter often leads to discussions between producers and retailers when it comes to defining clear limits of acceptability for modified atmosphere (MA) packed fish and fishery products. Suggested product limits (mg N/100 g fish) do not always correlate with the presence of off-odors. Gray shrimp are an economic valuable, very perishable niche product, where the TVB-N fraction plays an important role considering its shelf life. This research focuses on the effect of a shrimp matrix and its pH on the volatilization of these formed bases, revealing the relationship between concentrations in the fishery product and the concentrations of these bases present in the headspace of the packed product. Especially, the pH of the product, which is lowered when fishery products are packed under a carbon dioxide enriched atmosphere, appeared to have an immense effect on the volatilization of these bases. The effect of the fish matrix itself is established by means of calculated equilibration constants (dimensionless) being 2.13×10(-4)±0.38×10(-4) for trimethylamine, 6.34×10(-5)±1.71×10(-5) for dimethylamine, and 2.58×10(-5)±0.49×10(-5) for ammonia. Comparison of these constants with the equilibration constants of an aqueous solution indicated the retention of these bases in the product. This article provides not only the important insights for the interpretation of TVB-N values in modified atmosphere packaged gray shrimp but also the methodology to extend these findings to other fish and fishery products.  相似文献   
93.
BACKGROUND: In this study, the effects of three saponins and one sapogenin with a triterpenoid or steroid structure in two lepidopteran insect cell lines, ovarian Bm5 and midgut CF‐203 cells, were analysed with regard to cell viability, cell membrane permeation, EcR responsiveness and DNA fragmentation. In addition, the entomotoxic action of Q. saponaria saponin with primary midgut cell cultures and larval stages of the cotton leafworm Spodoptera littoralis was tested. RESULTS: Both lepidopteran cell lines show a high sensitivity to all four sapo(ge)nins, with a concentration‐dependent viability loss and EC50 values of 25–100 µM in MTT bioassays. A trypan blue assay with Q. saponaria saponin confirmed rapid cell membrane permeation to be a cause of cytotoxicity. Saponins caused no EcR activation in Bm5 cells, but a loss of ecdysteroid signalling was observed with IC50 values of 5–10 µM . Lower saponin concentrations induced DNA fragmentation, confirming their potential to induce apoptosis. Finally, Q. saponaria saponin caused cytotoxicity in primary midgut cell cultures of S. littoralis (EC50 = 4.7 µM ) and killed 70–84% of S. littoralis larvae at pupation at 30‐70 mg g?1, while lower concentrations retarded larval weight gain and development. CONCLUSIONS: The data obtained provide evidence that saponins exert a strong activity on lepidopteran cells, presumably based on a cytotoxic action due to permeation of the cell membrane. Primary midgut cell cultures and larvae of S. littoralis showed high sensitivity to Q. saponaria saponin, indicating the insect midgut as a primary target for entomotoxicity and the potential use of saponins in the control of pest Lepidoptera. Copyright © 2012 Society of Chemical Industry  相似文献   
94.
Cetirizine hydrochloride was administered orally at 5 mg/cat, q24h, to 32 cats with allergic skin disease. Pruritus was reduced in 41% (13/32) of the cats. The antipruritic effect was repeatable and sustainable. There was no significant association between patient age, disease severity, or cutaneous reaction pattern and improvement during cetirizine administration. No adverse side effects were reported.  相似文献   
95.
The chitin synthesis inhibitors diflubenzuron and teflubenzuron have recently become ineffective for the control of Spodoptera exigua in floricultural crops. An extended laboratory test with second-instar larvae of S. exigua on Vicia faba plants was carried out to determine the influence of synergists on the biological activity of three benzoylphenyl ureas (BPUs). The co-application of piperonyl butoxide, an oxidase inhibitor, did not increase the activity of diflubenzuron, teflubenzuron or hexaflumuron. The best results were obtained with diethyl maleate, for suppressing glutathione S-transferase activity, and with dimethoate, as a hydrolase inhibitor. A joint application of diflubenzuron (at a concentration which resulted in 43% survival) with diethyl maleate or dimethoate gave only 6.2 and 8.9% surviving larvae, respectively. In addition, development to fourth-instar larvae was inhibited. The more stable teflubenzuron was synergized by both compounds to a much lesser extent than diflubenzuron. None of the synergists had a significant effect on the activity of hexaflumuron, which was the most potent insecticide of the three BPUs tested against S. exigua.  相似文献   
96.
现在,雏鸡出壳后头7d内的营养和健康综合策略公认是影响肉鸡生产性能的最重要的决定因素之一。 由于刚出壳的雏鸡由胚胎生活转为肉鸡饲养舍环境下的出壳后生活,其心血管系统、消化系统、免疫系统、呼吸系统(肺)和骨骼系统必须全部发挥作用(与此同时各系统在体积上大大增加),方能确保其生长和对疾病的抵抗力。  相似文献   
97.
OBJECTIVES: To determine associations among infectious pathogens and diarrheal disease in dogs in an animal shelter and demonstrate the use of geographic information systems (GISs) for tracking spatial distributions of diarrheal disease within shelters. SAMPLE POPULATION: Feces from 120 dogs. PROCEDURE: Fresh fecal specimens were screened for bacteria and bacterial toxins via bacteriologic culture and ELISA, parvovirus via ELISA, canine coronavirus via nested polymerase chain reaction assay, protozoal cysts and oocysts via a direct fluorescent antibody technique, and parasite ova and larvae via microscopic examination of direct wet mounts and zinc sulfate centrifugation flotation. RESULTS: Salmonella enterica and Brachyspira spp were not common, whereas other pathogens such as canine coronavirus and Helicobacter spp were common among the dogs that were surveyed. Only intestinal parasites and Campylobacterjejuni infection were significant risk factors for diarrhea by univariate odds ratio analysis. Giardia lamblia was significantly underestimated by fecal flotation, compared with a direct fluorescent antibody technique. Spatial analysis of case specimens by use of GIS indicated that diarrhea was widespread throughout the entire shelter, and spatial statistical analysis revealed no evidence of spatial clustering of case specimens. CONCLUSIONS AND CLINICAL RELEVANCE: This study provided an epidemiologic overview of diarrhea and interacting diarrhea-associated pathogens in a densely housed, highly predisposed shelter population of dogs. Several of the approaches used in this study, such as use of a spatial representation of case specimens and considering multiple etiologies simultaneously, were novel and illustrate an integrated approach to epidemiologic investigations in shelter populations.  相似文献   
98.
OBJECTIVE: To evaluate a modified Ziehl-Neelsen acid-fast staining technique (mZN), a direct immunofluorescence detection procedure (DIF), and 3 commercial enzyme immunoassays (EIAs) for detection of Cryptosporidium oocysts in fecal specimens from kittens. DESIGN: Prospective study. SAMPLE POPULATION: 416 fecal specimens collected from 104 randomly selected domestic shorthair kittens (8 to 16 weeks of age) that were naturally exposed to Cryptosporidium spp. PROCEDURE: Fresh fecal specimens were collected once daily for 4 consecutive days and processed immediately. Sensitivities of mZN, DIF, and 3 commercial EIAs (EIA-1, EIA-2, and EIA-3) were estimated and compared. RESULTS: EIA-2 had the highest sensitivity on day 1 (89%), followed by EIA-1 (80%), and mZN (72%). EIA-3 had the lowest sensitivity on day 1 (15%). EIA-2, EIA-1, and mZN had similar sensitivities after 2 consecutive fecal examinations (approx 90%). Determination of specificities was compromised by the small number of cats that had negative results for all tests (n = 3). CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that EIA-2 and EIA-1 had the highest sensitivities when only a single fecal specimen was examined; however, mZN and EIA-1 had similar sensitivities when 2 consecutive fecal specimens were examined. The higher costs of EIA-2 and EIA-1 may be offset by the tests' high sensitivity, simplicity of use, and ease of interpretation and by savings in technician time.  相似文献   
99.
100.
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