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   142篇
  免费   0篇
林业   3篇
农学   5篇
基础科学   4篇
  41篇
综合类   3篇
农作物   10篇
水产渔业   1篇
畜牧兽医   71篇
园艺   1篇
植物保护   3篇
  2021年   3篇
  2019年   2篇
  2018年   1篇
  2017年   4篇
  2016年   2篇
  2013年   5篇
  2012年   5篇
  2011年   10篇
  2010年   4篇
  2009年   9篇
  2008年   14篇
  2007年   14篇
  2006年   8篇
  2005年   11篇
  2004年   6篇
  2003年   4篇
  2002年   4篇
  2001年   1篇
  2000年   1篇
  1997年   2篇
  1996年   1篇
  1995年   1篇
  1990年   3篇
  1989年   1篇
  1987年   2篇
  1986年   1篇
  1984年   1篇
  1979年   1篇
  1975年   3篇
  1973年   3篇
  1972年   2篇
  1971年   3篇
  1970年   1篇
  1969年   6篇
  1968年   2篇
  1966年   1篇
排序方式: 共有142条查询结果,搜索用时 31 毫秒
51.
In growing rats, boiled milled rice-legume diets (2:1 N ratio) had lower energy digestigibility than boiled milled rice and equal if not better true digestibility, biological value, and net protein utilization (NPU). Rice-soybean diets showed better NPU than the other rice-legume diets. Boiled whole-grain corn and sorghum had lower digstible energy and NPU than boiled milled rice. NPU of the diets did not follow strictly the trend of the amino acid score of the diets; phenol (tannin) content reduced energy and protein digestibility of all diets, but sugars reduced energy and protein digestibilities of rice-legume diets only.  相似文献   
52.
A headspace solid-phase microextraction (HS-SPME) method is proposed for analyzing the main volatile components from a sensory standpoint (furfural, oak lactones, eugenol, vanillin, and syringaldehyde) present in nontoasted and toasted oak wood of different origins. To maximize the yield of compounds extracted from wood chips and to obtain a good precision of the method, the most important variables affecting HS-SPME have been studied. The best results were obtained when the sample was heated at 70 degrees C and the headspace extracted for 40 min with a DVB/CAR/PDMS fiber, which gave the overall best recovery. The values for the repeatability ranged from 6.4 to 7.8%, and those for the reproducibility from 5.4 to 8.7%. The precision of the results obtained makes the proposed technique appropriate for its use in characterizing oak wood samples of different origins and in the selection of the most suitable oak wood to age wines and spirits, on the basis of the chemical composition of the wood samples.  相似文献   
53.
The effect of different drying treatments on the volatiles in bay leaf (Laurus nobilis L.) was studied. Simultaneous distillation extraction (SDE) and solid-phase microextraction (SPME) were compared by gas chromatography-mass spectrometry (GC-MS) of the volatile components in bay leaves. SDE yielded better quantitative analysis results. Four drying treatments were employed: air-drying at ambient temperature, oven-drying at 45 degrees C, freezing, and freeze-drying. Oven drying at 45 degrees C and air-drying at ambient temperature produced quite similar results and caused hardly any loss in volatiles as compared to the fresh herb, whereas freezing and freeze-drying brought about substantial losses in bay leaf aroma and led to increases in the concentration levels of certain components, e.g., eugenol, elemicin, spathulenol, and beta-eudesmol.  相似文献   
54.
A long-term (30 year) historical analysis of turfgrass monthly net irrigation requirements for southeast USA is analyzed and discussed in this paper. The process involved gathering weather data for ten locations in Florida plus one in Alabama, from 1980 through 2009, and data quality. Available weather data included maximum and minimum temperature, maximum and minimum relative humidity, wind speed, and rainfall. Solar radiation was estimated using the Hargreaves–Samani equation, and coefficients were calibrated for every location. Reference evapotranspiration (ETos) was calculated using the ASCE-EWRI standardized reference evapotranspiration equation. Net irrigation was estimated using a daily soil–water balance. Variability in soil types and root depth was taken into account during the simulations, and three sets of monthly K c values from the literature were applied from north through south Florida. Results showed that the calibrated Hargreaves–Samani adjustment coefficients varied from 0.14 in Tallahassee to 0.24 in Key West, with an inland average value of 0.15, and a coastal average value of 0.18. The calculated ETos ranged from 1,296 mm year?1 in Tallahassee to 1,658 mm year?1 in Miami. The estimated net irrigation ranged from 423 mm year?1 in Mobile, AL, to 1,063 mm year?1 in Key West, FL. The number of irrigation events per year varied from 25 in Mobile to 161 in Key West. May and December were the months with the highest and lowest net irrigation requirements, respectively.  相似文献   
55.
Five strains of Rhipicephalus (Boophilus) microplus collected from Tamaulipas Mexico were tested for resistance against several classes of acaricides commonly used. All were resistant to fipronil. Four of five were co-resistant to permethrin and coumaphos in addition to being resistant to fipronil. One strain, El Zamora was found multi-resistant to permethrin, coumaphos, fipronil, and amitraz. Selection with fipronil for 3 generations produced a resistance ratio of 8.3 and 9.4 at the LC50 and the LC99 estimates, respectively. Permethrin resistance in El Zamora was possibly linked to elevated esterase (CZEST9) and could be a contributing factor of resistance to fipronil. The implications of resistance for the control of the southern cattle tick in the future are discussed.  相似文献   
56.
Cyprodinil is an anilinopyrimidine fungicide applied worldwide for the prevention and treatment of highly destructive plant diseases in a large variety of crops, including cereals, fruits, and vegetables. This paper describes the development of the first reported immunoassays for cyprodinil. Two original haptens have been synthesized and conjugated to different carrier proteins, and polyclonal antibodies have been produced. Moreover, competitive enzyme-linked immunosorbent assays have been developed and characterized for the analysis of this widely used pesticide. The influence of organic solvents and buffer conditions over the assay analytical parameters was studied. The IC(50) values of the optimized immunoassays were 1.6 and 2.8 ng/mL for the direct and indirect formats, respectively. Quantitative recoveries were found using spiked apple and grape juice samples after a simple direct dilution, and a limit of quantification of 20 ng/mL for both fruit matrices was achieved. These immunoreagents could be very valuable for the sensitive, straightforward, and rapid monitoring of cyprodinil residues in foodstuffs.  相似文献   
57.
The quality of three types of treated sludges (sludge from the paper recycling industry, and sewage sludge treated by composting with pruning waste and thermally dried) was assessed in this work. The amendments were physicochemically characterized and evaluated for their microbiological quality and for contamination with pollutants. All three organic amendments showed an absence of pathogens, so they are microbially suitable for agricultural use. The pollutants studied in the amendments included eight heavy metals and 83 organic compounds. Heavy metals, pesticides, polycyclic aromatic hydrocarbons, octylphenol, bisphenol A, and parabens were found in the organic amendments. The amount and type of contaminants depended on the sample sources and differed between samples from a single origin. The presence of some of the pollutants found has not been previously reported in organic amendments. The germination assay showed that these amendments may be applied to soil in controlled doses. As far as we know, this is the first reported study that has evaluated a great variety of pollutants (heavy metals, pesticides, persistent and emerging organic pollutants) in sludge from the recycled paper industry; moreover, studies in other waste products in which such a broad range of pollutants has been evaluated have been scarce until now due to the complexity of these matrices.  相似文献   
58.

Background

Variability among stallions in terms of semen cryopreservation quality renders it difficult to arrive at a standardized cryopreservation method. Different extenders and processing techniques (such us colloidal centrifugation) are used in order to optimize post-thaw sperm quality. Sperm chromatin integrity analysis is an effective tool for assessing such quality. The aim of the present study was to compare the effect of two single layer colloidal centrifugation protocols (prior to cryopreservation) in combination with three commercial freezing extenders on the post-thaw chromatin integrity of equine sperm samples at different post-thaw incubation (37°C) times (i.e., their DNA fragmentation dynamics).

Results

Post-thaw DNA fragmentation levels in semen samples subjected to either of the colloidal centrifugation protocols were significantly lower (p<0.05) immediately after thawing and after 4 h of incubation at 37°C compared to samples that underwent standard (control) centrifugation. The use of InraFreeze® extender was associated with significantly less DNA fragmentation than the use of Botu-Crio® extender at 6 h of incubation, and than the use of either Botu-Crio® or Gent® extender at 24 h of incubation (p<0.05).

Conclusions

These results suggest that single layer colloidal centrifugation performed with extended or raw semen prior to cryopreservation reduces DNA fragmentation during the first four hours after thawing. Further studies are needed to determine the influence of freezing extenders on equine sperm DNA fragmentation dynamics.  相似文献   
59.
The tomato leafminer Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is a devastating pest of tomato originating from South America. After its initial detection in eastern Spain in 2006, it rapidly invaded various other European countries and spread throughout the Mediterranean basin. If no control measures are taken, then the pest can cause up to 80–100% yield losses in tomato crops in recently invaded areas and may pose a threat to both greenhouse and open-field tomato production. The exceptional speed and extent of T. absoluta invasion have called for studies documenting its biology and ecology, while indicating an urgent need for efficient and sustainable management methods. The development of approaches to manage T. absoluta would be facilitated through a detailed revision of information on this pest in its area of origin. This review combines information on the invasion by T. absoluta, its ecology, and potential management strategies, including data that may help the implementation of efficient biological control programs. These programs, together with a variety of other management tactics, may allow efficient integrated pest management of T. absoluta in Europe and Mediterranean Basin countries.  相似文献   
60.
The cultivation of rice (Oriza sativa L.) under Mediterranean conditions regularly requires the use of treated wastewater due to shortage of freshwater. As a consequence, the intensification of rice production to supply the uprising demand of grain could break the stability between agriculture and environment. In this work, we studied the occurrence and distribution of pyrethroids in surface water and groundwater collected during two periods (flooding and dry soil conditions) in paddy fields located in the Spanish Mediterranean coast. Pyrethroids were detected at concentrations ranging from 14 to 1450 ng L?1 in surface water and from 6 to 833 ng L?1 in groundwater. The results obtained were evaluated statistically using principal component analysis, and differences between both sampling campaigns were found, with lower concentrations of the target compounds during the flooding sampling event. Moreover, a geographic information system program was used to represent a model distribution of the obtained results, showing wastewater treatment plants as the main sources of contamination and the decrease of pyrethroids during flooding condition when water flows over the paddy fields. The impact of these compounds on water quality was discussed.  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