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   267篇
  免费   19篇
林业   23篇
农学   18篇
基础科学   2篇
  41篇
综合类   19篇
农作物   31篇
水产渔业   26篇
畜牧兽医   94篇
园艺   6篇
植物保护   26篇
  2024年   1篇
  2023年   1篇
  2022年   5篇
  2021年   10篇
  2020年   18篇
  2019年   17篇
  2018年   23篇
  2017年   21篇
  2016年   13篇
  2015年   17篇
  2014年   15篇
  2013年   20篇
  2012年   16篇
  2011年   20篇
  2010年   4篇
  2009年   9篇
  2008年   8篇
  2007年   3篇
  2006年   5篇
  2005年   6篇
  2004年   6篇
  2003年   5篇
  2002年   2篇
  2001年   3篇
  2000年   4篇
  1999年   3篇
  1998年   1篇
  1997年   3篇
  1996年   1篇
  1995年   1篇
  1994年   2篇
  1992年   2篇
  1990年   2篇
  1989年   2篇
  1988年   2篇
  1987年   3篇
  1986年   3篇
  1985年   2篇
  1984年   5篇
  1983年   1篇
  1982年   1篇
排序方式: 共有286条查询结果,搜索用时 15 毫秒
251.
Ascochyta blight, caused by Didymella rabiei, affects both domesticated chickpea and its congeneric wild relatives. The aim of this study was to compare the aggressiveness of D. rabiei isolates from wild and domesticated Cicer spp. in Turkey and Israel on wild and domesticated hosts from both countries. A total of eight isolates of D. rabiei sampled from C. pinnatifidum, C. judaicum and C. arietinum in Turkey and Israel was tested on two domesticated chickpea cultivars and two wild Cicer accessions from Turkey and Israel. Using cross-inoculation experiments, we compared pathogen aggressiveness across the different pathogen and host origin combinations. Two measures of aggressiveness were used, incubation period and relative area under the disease progress curve. The eight tested isolates infected all of the host plants, but were more aggressive on their original hosts with one exception; Turkish domesticated isolates were less aggressive on their domesticated host in comparison to the aggressiveness of Israeli domesticated isolates on Turkish domesticated chickpea. C. judaicum plants were highly resistant against all of the isolates from different origins except for their own isolates. Regardless of the country of origin, the wild isolates were highly aggressive on domesticated chickpea while the domesticated isolates were less aggressive on the wild hosts compared with the wild isolates. These results suggest that the aggressiveness pattern of D. rabiei on different hosts could have been shaped by adaptation to the distinct ecological niches of wild vs. domesticated chickpea.  相似文献   
252.
253.
The fall armyworm Spodoptera frugiperda is a lepidopteran pest that can damage and destroy a wide variety of crops. It is widely present in the Americans and has been invasive in Africa since 2016. Larvae of Sfrugiperda were found for the first time in four rural farms on maize plants (Zea mays) located in Tafas town (Dara’a Governorate, in the south‐west of Syria) in November 2020. Infested maize showed the typical damage symptoms caused by Sfrugiperda. Furthermore, morphological identification of larvae based on standard parameters of larvae confirmed the identity of the pest as fall armyworm. Considering the recent introduction of the pest into the EPPO region, it could be concluded that the pest probably entered Syria through natural spread (active flight and via wind currents) from Jordan, which borders Syria in the southern part and where the pest was found very recently.  相似文献   
254.
Gesunde Pflanzen - In this study, pepper (Capsicum annuum L.) inbred lines were grafted onto different rootstock genotypes and tested under saline conditions. A hydroponic...  相似文献   
255.
Ulas  Firdes  Yetisir  Halit  Ulas  Abdullah 《Gesunde Pflanzen》2021,73(4):417-425
Gesunde Pflanzen - To assess whether grafting could improve the nitrogen (N) efficiency of potato cultivars and to determine which physiological and morphological characteristics are...  相似文献   
256.
Fractions derived from Clerodendrum phlomidis Linn. F. and isolated compounds from chloroform extract were evaluated against Earias vittella Fab. for their ovicidal and oviposition deterrent activities. There were 12 fractions obtained with silica gel column chromatographic techniques using different solvent systems. Among the fractions, fraction 5 recorded maximum ovicidal activity of 68.49% and oviposition deterrent activity of 100% at 1000 ppm concentration followed by 500 ppm concentration. The active fraction was further purified using HPLC. The purified fraction was subjected to UV, 1HNMR, 13CNMR, IR and EI-Mass spectroscopy and their spectral data confirmed the compound pectolinaringenin which belongs to the flavonoids. The compound pectolinaringenin was screened for its ovicidal and oviposition deterrent activities. It showed maximum ovicidal activity of 64.29% and oviposition deterrent activity of 100% at 100 ppm concentration against E. vittella. To the best of our knowledge, this is the first report of fractions and isolated compounds from C. phlomidis evaluated against E. vittella for their ovicidal and oviposition deterrent activities. The results from the present investigation clearly suggest that the active fraction or the isolated compound could be used to develop a novel pesticidal formulation to control economically important agricultural pests.  相似文献   
257.
The adsorption of residue oil from palm oil mill effluent using natural zeolite was investigated in this study. The adsorption was performed in batch mode, and the effect of different operational parameters such as pH, dose of adsorbent, stirring rate, contact time and initial oil concentration were explored. It was found that the pH plays a major role in the adsorption process. Isotherm data best fitted with the Freundlich model, and kinetic data followed the pseudo-second-order kinetic model. The results obtained demonstrated that the oil removal efficiencies by natural zeolite were up to 70?% at a pH of 3.0 and 50?min of contact time. The adsorbent material also has been characterised by X-ray diffraction, X-ray fluorescence and scanning electron microscopy.  相似文献   
258.
In order to observe the variation in land use changes, satellite images from the Landsat Thematic Mapper (TM) and the Enhanced Thematic Mapper (ETM) for 1991, 2000, 2005, and 2008 were used to compare the differences between selected water quality parameters, including heavy metal (Cd, Pb, and Zn) content in both water and green mussels or Perna viridis (Linnaeus.) before and after the increase in land use activities beginning from 2006. The samples were collected at 11 points for water and 4 points for green mussels between the Second Link and the Causeway Link at the Johor Strait in 2009 and were analyzed for pH, temperature degrees Celsius), dissolved oxygen, ammoniacal nitrogen, and heavy metal (Cd, Pb, and Zn) content.  相似文献   
259.
Background: Haemonchosis is a major economic problem in goat production in humid, tropical and subtropical regions. The disease is caused by an abomasal nematode, Haemonchus contortus, which is highly pathogenic in small ruminants. The aim of this study was to identifying single-nucleotide polymorphisms(SNP) that were associated with fecal egg counts(FEC) and could be used as markers to identify resistance to H. contortus in goats.Results: Ten novel variants in the CI TA, ATP2 A3, HSPA8, STAT5 B, ESYT1, and SERPING1 genes were associated with FEC in goats with a nominal significance level of P 0.05. Two missense mutation in the exon region of the caprine CI TA gene resulted in replacement of arginine with cysteine at position 9473550(R9473550 C) and aspartic acid with glutamic acid at position 9473870(D9473870 E). Chinese goat breeds had significantly higher FEC than Bangladeshi goat breeds within their respective genotypes. Polymorphism information content(PIC), effective al ele number(Ne), and heterozygosity(He)were greatest for the STAT5 B_197_A G SNP locus in al goat breeds. Pairwise coefficients of linkage disequilibrium(D′, r~2)revealed complete LD(r~2= 1) between significant SNP polymorphisms in CI TA and SERPING1 and strong LD(r~2= 0.93 and0.98) between polymorphisms in HSPA8 and ATP2 A3, respectively. Correlation coefficient(r) between FEC and body weight(BW) was significantly positive(r = 0.56***, P 0.001) but that between FEC and packed cel volume(PCV) was negatively significant(r =-0.47**, P 0.01) in the total population of goats. On the other hand, correlation coefficient(r)between BW and PCV was not significant in total population of goats. Association analysis revealed that haplotypes within ATP2 A3, HSPA8, and SERPING1 were significantly associated with FEC. Quantitative real-time PCR revealed that the relative expression of m RNA was higher(P 0.001) for resistant, compared to susceptible, groups of goats for al candidate genes except CI TA.Conclusions: This study identified SNP markers that can potential y be used in marker-assisted selection programs to develop goat breeds that are resistant to H. contortus.  相似文献   
260.
Background: Increasing understanding on the functions of amino acids(AA) has led to new commercial applications and expansion of the worldwide markets. However, the current technologies rely heavily on non-food grade microorganism and chemical synthesis for the production of AA. Several studies reported that lactic acid bacteria(LAB) have the capability of producing AA owing to their well-established proteolytic system and amino acid biosynthesis genes. Hence, the objectives of this study were to explore the extracellular proteolytic activity of LAB isolated from various Malaysian fermented foods and their potential to produce AA extracellularly as feed supplements.Results: Al the studied LAB isolates were versatile extracel ular protease producers, whereby extracel ular protease activities were detected from acidic to alkaline pH(pH 5, pH 6.5, pH 8) using qualitative and quantitative proteolytic assays.The highest proteolytic activity at pH 5(15.76 U/mg) and pH 8(19.42 U/mg) was achieved by Lactobacil us plantarum RG14, while Lactobacil us plantarum RS5 exhibited the highest proteolytic activity of 17.22 U/mg at pH 6.5. As for the results of AA production conducted in de Man, Rogosa and Sharpe medium and analysed by high pressure liquid chromatography system, al LAB isolates were capable of producing an array of AA. General y, Pediococcus sp. showed greater ability for AA production as compared to Lactobacil us sp. Moreover, the studied LAB were able to produce a few major feed supplement AA such as methionine, lysine, threonine and tryptophan. P. pentosaceus TL-3 recorded the highest methionine and threonine productivity of 3.72 mg/L/h and 5.58 mg/L/h respectively. However, L. plantarum I-UL4 demonstrated a lysine productivity of 1.24 mg/L/h, while P. acidilactici TP-6 achieved up to 1.73 mg/L/h of tryptophan productivity.Conclusion: Al the 17 studied LAB isolates possessed versatile extracel ular proteolytic system and have vast capability of producing various amino acids including a few major feed supplement AA such as methionine, lysine, threonine and tryptophan. Despite AA production was strain dependent, the studied LAB isolates possessed vast potential and can be exploited further as a bio-agent or an alternative amino acids and bioactive peptide producers.  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