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   170篇
  免费   20篇
林业   2篇
  10篇
综合类   21篇
农作物   3篇
水产渔业   2篇
畜牧兽医   145篇
植物保护   7篇
  2020年   3篇
  2019年   7篇
  2018年   6篇
  2017年   6篇
  2016年   4篇
  2015年   5篇
  2014年   9篇
  2013年   23篇
  2012年   4篇
  2011年   5篇
  2010年   11篇
  2009年   9篇
  2008年   1篇
  2007年   9篇
  2006年   9篇
  2005年   3篇
  2004年   1篇
  2003年   5篇
  2002年   4篇
  2001年   5篇
  2000年   2篇
  1999年   3篇
  1998年   14篇
  1997年   11篇
  1996年   8篇
  1995年   2篇
  1994年   3篇
  1993年   3篇
  1992年   1篇
  1991年   2篇
  1990年   2篇
  1989年   3篇
  1988年   1篇
  1985年   1篇
  1984年   1篇
  1978年   1篇
  1970年   1篇
  1969年   1篇
  1934年   1篇
排序方式: 共有190条查询结果,搜索用时 31 毫秒
101.
CM Roberts 《Science (New York, N.Y.)》1997,278(5342):1454-1457
Surface current patterns were used to map dispersal routes of pelagic larvae from 18 coral reef sites in the Caribbean. The sites varied, both as sources and recipients of larvae, by an order of magnitude. It is likely that sites supplied copiously from "upstream" reef areas will be more resilient to recruitment overfishing, less susceptible to species loss, and less reliant on local management than places with little upstream reef. The mapping of connectivity patterns will enable the identification of beneficial management partnerships among nations and the design of networks of interdependent reserves.  相似文献   
102.
103.
104.
Abstract

AIM: To identify weather variables associated with the development of eggs of Teladorsagia (=Ostertagia) circumcincta, Trichostrongylus colubriformis and Haemonchus contortus to third-stage infective larvae (L3) under a range of climatic conditions on pasture in the North Island of New Zealand.

METHODS: Sheep faeces containing known numbers of eggs of all three nematode species were deposited on, or buried in, pasture plots at three sites, viz coastal Manawatu, Upper Hutt Valley, and East Cape hill country. Development was measured by recovering L3 from faeces, herbage and soil 28–31 days after deposition, on 13–18 occasions between January 2005 until July 2006. Weather data were recorded at each site, and the association between weather variables and number of L3 recovered was analysed using subsets regression to select best-fitting models from several candidate variables, after adjustment for efficiency of recovery of L3. A multiple linear regression model was then developed for each species, to select weather variables that had both significant and substantive effects on the number of L3 recovered.

RESULTS: For all species, mean daily temperature was the bestpredictor of the number of L3 recovered (p=0.001). For T.circumcincta the final model included mean daily temperature and soil temperature (R2=51%), and for T. colubriformis the model only included mean daily temperature (R2=55%). For development of H. contortus, mean daily temperature was the most significant variable, but moisture in the form of rainfall entropy, i.e. the temporal distribution of rainfall, overthe first 14 days was also significant in the final model (R2=34%).

CONCLUSIONS: Temperature was the most important determinant of developmental success of free-living nematodes on pasture at the study sites, and probably also for other parts ofNew Zealand with similar climates. Moisture was not significant in the development of T. circumcincta or T.colubriformis, implying that under the generally moist temperate climate in New Zealand, moisture is seldom limiting for development of these species. Haemonchus contortusappeared to be sensitive to moisture availability and precipitation in the first 14 days after deposition of faeces. The results of this study will be further developed as part of species-specific climate-driven models of parasite development in New Zealand.  相似文献   
105.
AIM: To compare the rectal and I/V administration of tramadol in dogs, to assess both its pharmacokinetic properties and absolute bioavailability.

METHODS: After rectal administration via suppositories and I/V injection of tramadol (4 mg/kg), the concentration of tramadol and its main metabolites, O-desmethyl-tramadol (M1), N-desmethyl-tramadol (M2) and N,O-didesmethyl-tramadol (M5), were determined in plasma, using high-performance liquid chromatography (HPLC). A balanced cross-over study was used, involving six male Beagle dogs.

RESULTS: Plasma concentrations after rectal and I/V administration were fitted on the basis of mono- and bi-compartmental models, respectively. Following rectal administration tramadol was detected from 5 minutes up to 10 hours, in lesser amounts than M5 and M2, while M1 was detected in negligible amounts. Following I/V administration tramadol was detected up to 10 hours, M2 and M5 were detected at similar concentrations, and M1 was present at low concentrations. The area under the curve (AUC) of the three metabolites did not differ significantly after either route of administration of tramadol. The absolute bioavailability of tramadol via rectal administration was 10 (SD 4)%.

CONCLUSIONS: After rectal administration of tramadol suppositories, absorption of the active ingredient was rapid, but its metabolism quickly transformed the parent drug to high levels of M2 and M5.

CLINICAL RELEVANCE: In the dog, rectal pharmaceutical formulation of tramadol would have a different pharmacokinetic behaviour than in humans.  相似文献   
106.
107.
108.
Winter wheat producers in Oklahoma often combine an insecticide with a top-dress application of nitrogen during late fall and winter to control existing greenbug populations. We evaluated the efficacy of three classes of insecticides applied in cold weather field conditions ranging from −13.3 to 28.9 °C from 2002 to 2004 for greenbug control in winter wheat in replicated small plots. Insecticides provided control ranging from 0% to 98%, but generally responded similarly to temperature. Percent control of greenbugs resulting from applications of dimethoate, chlorpyrifos and λ-cyhalothrin was correlated with maximum, minimum and average daily temperatures that occurred two days post-treatment. While percent control was unique for each insecticide, a combined regression of percent control against average daily temperature predicted that a 95% level of control would be achieved when post-treatment temperatures exceeded 13.6 °C. Rainfall that occurred post-treatment affected the efficacy of dimethoate but did not affect the other insecticides. Insecticide persistence was extended under cooler temperatures, allowing acceptable control 14 days post-treatment if temperatures warmed. The decision to apply insecticides should be made based on existing treatment thresholds for greenbug, but if treatment with an insecticide is warranted, winter wheat producers can expect reasonable control of greenbugs from insecticides applied during the winter, as long as post-treatment temperatures exceed 13 °C within the following 14 days.  相似文献   
109.
110.
The effect of pesticide delivery on the eficacy of equivalent rates of several insecticides was investigated by comparing broadcast foliar sprays to applications via drip irrigation in bell peppers, celery and cantaloupe. Oxamyl applied through the drip line controlled green peach aphids, Myzus persicae (Sulzer) in bell peppers, Capsicum annum L. ‘Tambel-2’, throughout the growing season, but did not control pepper weevil, Anthonomus eugenii Cano populations. Foliar applications of oxamyl controlled both insects. Foliar applications of cyromazine controlled leafminers, Liriomyza spp. in bell peppers late in the growing season. Drip applications of cyromazine suppressed leafiminers early in the growing season, but were ineffective in later applications. In cantaloupe, Cucumis melo L. ‘Magnum 45’, populations of melon aphids, Aphis gossypii Glover were suppressed with oxamyl and oxydemeton-methyl, but foliar applications were significantlymore effective in achieving reductions. Oxamyl controlled leafmminers in cantaloupe with both application methods after the first evaluation, but control was superior with foliar applications at the second evaluation. Oxamyl suppressed populations of the western potato leafhopper, Empoasca abrupta DeLong in celery, Apium graveolens L. ‘5270’, using either delivery method. Oxamyl residues in drip-applied celery were higher than USA regulations would allow, thus the rate of application would have to be modified. A cost analysis comparing delivery systems indicated that a drip-applied insecticide application was much less expensive than a foliar application with air or ground equipment. However, control was limited to phloem-feeding insects, was slower in attainment, and at best, was equal to or less than that obtained with a foliar spray.  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