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   278篇
  免费   22篇
林业   18篇
农学   9篇
基础科学   8篇
  69篇
综合类   10篇
农作物   29篇
水产渔业   28篇
畜牧兽医   88篇
园艺   11篇
植物保护   30篇
  2024年   1篇
  2023年   2篇
  2022年   7篇
  2021年   7篇
  2020年   14篇
  2019年   15篇
  2018年   18篇
  2017年   12篇
  2016年   8篇
  2015年   9篇
  2014年   10篇
  2013年   22篇
  2012年   17篇
  2011年   20篇
  2010年   12篇
  2009年   10篇
  2008年   18篇
  2007年   11篇
  2006年   16篇
  2005年   9篇
  2004年   7篇
  2003年   10篇
  2002年   11篇
  2001年   3篇
  2000年   1篇
  1999年   3篇
  1998年   2篇
  1997年   2篇
  1996年   1篇
  1995年   1篇
  1993年   1篇
  1991年   1篇
  1990年   1篇
  1989年   3篇
  1988年   1篇
  1985年   1篇
  1983年   1篇
  1981年   1篇
  1980年   1篇
  1977年   3篇
  1975年   1篇
  1974年   1篇
  1973年   2篇
  1972年   1篇
  1968年   1篇
  1935年   1篇
排序方式: 共有300条查询结果,搜索用时 406 毫秒
271.
The present research assessed the radical scavenging activity against the synthetic 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl radical of the water-saturated 1-butanol extracts of wholemeal flour from 63 Triticum monococcum accessions, which originated from different eco-geographical areas. On average, T. monococcum had higher radical scavenging activity than T. turgidum and T. aestivum species, which served as controls (0.90, 0.64 and 0.70 mmol TE/kg DM, for T. monococcum, T. turgidum and T. aestivum, respectively). A significant correlation between radical scavenging activity and tocol content was observed, while no correlation existed with soluble phenolics and carotenoid contents.  相似文献   
272.
The molluscicidal activities of ten Baylis-Hillman adducts against Biomphalaria glabrata (Say) snails, the intermediate host of schistosomiasis, have been determined. Nine of these compounds showed significant molluscicidal activity against B. glabrata, falling below the threshold of 100 microg ml(-1) set for potential molluscicidal activity by the World Health Organisation. Among these compounds, 3-hydroxy-2-methylene-3-(4-nitrophenyl)propanenitrile had the highest activity, with LC(50) = 6.64 microg ml(-1).  相似文献   
273.
ABSTRACT

The resulting supernatant from the isoelectric precipitation of “sawdust” from Cape hake portioning and blue whiting muscle was concentrated by ultrafiltration and the retentate spray-dried. Two main peaks corresponding to molecular weights of 15 kDa and 65 kDa were detected in the supernatant from both raw materials; in the retentate the main proteins had approximately 18 kDa and 73 kDa, and some proteins with 59 kDa were detected in the permeate. The protein content was 74.0% and 70.0% for hake by-products and blue whiting, respectively. Dried proteins had relatively low emulsifying and foaming capacity but high foaming stability and were whitish in color. Hydrophobicity and sulphydryl content were similar to those from other protein sources.  相似文献   
274.

Background  

The cultivar Micro-Tom (MT) is regarded as a model system for tomato genetics due to its short life cycle and miniature size. However, efforts to improve tomato genetic transformation have led to protocols dependent on the costly hormone zeatin, combined with an excessive number of steps.  相似文献   
275.
Disease resistance genes most commonly used in breeding programs are single, dominant genes with relative effectiveness that is sometimes influenced by plant developmental stage. Knowing the developmental stages at which a resistance gene is functional is important for disease management. In rice, resistance at the seedling stage is crucial, because wounding during transplanting increases the potential for bacterial blight disease, and not all bacterial blight resistance genes are effective at the seedling stage. Effectiveness of the bacterial blight resistance genes Xa4, xa5, and Xa7, all in a common genetic background, was evaluated at different developmental stages by measuring lesion length and bacterial numbers after inoculation with the bacterial pathogen, Xanthomonas oryzae pv. oryzae. The Xa4 and xa5 genes controlled disease at all growth stages. In contrast, Xa7 was not fully functional in very young seedlings, but was completely effective by 21 days after sowing (das). The effects of plant developmental stage on interactions of the Xa7 gene with X. oryzae pv. oryzae strains carrying different mutant avrXa7 alleles were also tested. If a partial or fully functional avrXa7 allele was present, Xa7 resistance was effective at all growth stages tested after the transplant stage (>21 das).  相似文献   
276.
277.
278.
The aim of the present study was to determine the effective dose of an experimental fasciolicide called compound alpha or 5-chloro-2-methylthio-6-(1-napthyloxy)1H-benzimidazole in experimentally and naturally infected cattle. In the first experiment, 24 fluke-free heifers were each infected with 800 metacercariae of Fasciola hepatica and re-infected on day 45 with other 600 cysts per animal. On day 75, when the animals had 4- and 10-week-old flukes respectively, they were divided into four groups (G) of six animals each according to fluke egg counts. Groups 1-3 received compound alpha at 10, 12 and 14 mg/kg/p.o., respectively. G4 remained as an untreated control. Twenty days after treatment, the animals were sacrificed for the recovery of flukes. Efficacy was assessed as a percentage of egg or fluke reduction relative to the untreated control. In the second experiment (naturally infected cattle), 24-year-old steers positive to F. hepatica eggs were blocked into four groups of five animals each. Groups 1-3 received compound alpha at 10, 12 and 14 mg/kg/p.o., respectively. Group 4 served as a non-treated control. All procedures to determine efficacy were carried out as mentioned in the first experiment. The results in the first study showed a percentage on egg reduction of 97.3, 100 and 100 and overall fluke reduction of 94.3, 100 and 100 for Groups 1-3, respectively. In the second study, the percentage of egg reduction was of 87.5, 99.1 and 100 and overall efficacy regarding fluke reduction was of 84.2, 99.6, and 100 for Groups 1-3, respectively. It is concluded that the effective dose selected for compound alpha was of 12 mg/kg/p.o. in cattle having an induced or natural F. hepatica infection.  相似文献   
279.
OBJECTIVE: To compare prothrombin time (PT), activated partial thromboplastin time (APTT), and fibrinogen concentration in canine blood samples collected via an indwelling IV catheter and direct venipuncture. ANIMALS: 35 dogs admitted to an intensive care unit that required placement of an IV catheter for treatment. PROCEDURES: Blood samples were collected via IV catheter and direct venipuncture at the time of catheter placement and 24 hours after catheter placement. Prothrombin time, APTT, and fibrinogen concentration were measured. RESULTS: 5 dogs were excluded from the study; results were obtained for the remaining 30 dogs. Agreement (bias) for PT was -0.327 seconds (limits of agreement, -1.350 to 0.696 seconds) and 0.003 seconds (limits of agreement, -1.120 to 1.127 seconds) for the 0- and 24-hour time points, respectively. Agreement for APTT was -0.423 seconds (limits of agreement, -3.123 to 2.276 seconds) and 0.677 seconds (limits of agreement, -3.854 to 5.207 seconds) for the 0- and 24-hour time points, respectively. Agreement for fibrinogen concentration was -2.333 mg/dL (limits of agreement, -80.639 to 75.973 mg/dL) and -1.767 mg/dL (limits of agreement, -50.056 to 46.523 mg/dL) for the 0- and 24-hour time points, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Agreement between the 2 techniques for sample collection was clinically acceptable for PT, APTT, and fibrinogen concentration at time 0 and 24 hours. It is often difficult or undesirable to perform multiple direct venipunctures in critically ill patients. Use of samples collected via an IV catheter to monitor PT and APTT can eliminate additional venous trauma and patient discomfort and reduce the volume of blood collected from these compromised patients.  相似文献   
280.
An exhaustive biochemical characterisation of 60 porcine Pasteurella multocida clinical isolates recovered from lesions indicative of pneumonia, previously confirmed by PCR and all belonging to the capsular serogroup A, was performed by means of four commercial systems. The API 20NE correctly identified almost all isolates (95%), but only 60% could be ascribed to this species by the API 20E method. The high diversity exhibited by the API 50CHB/E system, with six different patterns, does not advise its use as additional system for a definitive identification at the species level, but this method could be a potential tool for characterising P. multocida isolates below this level. The more uniform reactions yielded by the API ZYM test make this system helpful in the confirmatory identification of this organism. The high variability (20 profiles) obtained when the four systems are taken together also suggests their usefulness for epidemiological purposes in order to sub-type P. multocida isolates.  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