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   106篇
  免费   9篇
林业   5篇
农学   3篇
基础科学   2篇
  4篇
综合类   10篇
农作物   1篇
畜牧兽医   72篇
园艺   1篇
植物保护   17篇
  2023年   1篇
  2021年   1篇
  2020年   1篇
  2019年   1篇
  2018年   3篇
  2017年   2篇
  2016年   5篇
  2015年   5篇
  2014年   5篇
  2013年   10篇
  2012年   2篇
  2011年   3篇
  2010年   3篇
  2009年   3篇
  2008年   4篇
  2007年   4篇
  2006年   1篇
  2005年   1篇
  2003年   1篇
  2002年   2篇
  2001年   2篇
  2000年   5篇
  1999年   4篇
  1998年   8篇
  1997年   9篇
  1996年   5篇
  1995年   3篇
  1993年   5篇
  1992年   3篇
  1991年   2篇
  1990年   5篇
  1989年   2篇
  1988年   3篇
  1974年   1篇
排序方式: 共有115条查询结果,搜索用时 31 毫秒
101.
102.
A collection of 127 strains of Erwinia amylovora, the causative agent of fire blight, was tested by PCR amplification of a fragment of the plasmid pEA29. A variability in the length of the DNA fragment obtained was observed after digestion by MspI and Sau3A restriction enzymes. Strains were distributed into three groups according to the length of the DNA product. Most of the strains analysed were placed into two groups. Thirteen strains were clustered into a third group which was linked with the geographical origin of strains: they were all isolates from recently reported outbreaks of fire blight in Austria and in southern Bavaria in Germany. The variation in the length of the amplified fragment is probably due to an insertion into this fragment.  相似文献   
103.
ABSTRACT The sequences of the 16S rRNA genes (nucleotides 29 to 1,521) from various Streptomyces strains pathogenic to potato were compared. These included 10 pathogenic Streptomyces strains isolated from potato scab lesions in Finland, the type strains of S. aureofaciens NRRL 2209(T) and S. lydicus ATCC 25470(T), 'S. griseus subsp. scabies' ATCC 10246, and two S. griseus strains that were originally deposited to the collection as pathogens. The nucleotide sequence (>94.5% sequence identity [SI]) and length (1,469 to 1,481 nucleotides) of the analyzed region varied. Phylogenetic analysis of 16S rRNA genes placed Finnish strains into three species, supported by previously characterized morphological and physiological traits. Six Finnish strains, including two strains that deviated from the others in one trait (no spiral sporophores or D-xylose utilization), had identical 16S rRNA genes and were identified as S. scabies (99.9% SI to S. scabies ATCC 49173). Three Finnish strains were identified as S. turgidiscabies, a species previously described only in Japan (99.9% SI to S. turgidiscabies ATCC 700248). Finnish strain 317 and S. aureofaciens NRRL 2209 (99.8% SI) were placed in a distinct phylogenetic cluster together with Kitosatospora spp., which suggests that S. aureofaciens may belong to the recently revived genus Kitosatospora. In pathogenicity tests, S. scabies caused characteristic symptoms of common scab, S. turgidiscabies caused mainly pitted scab, and S. aureofaciens caused netted scab and necrotic lesions on stolons of potato cultivars Bintje and Matilda in the greenhouse. The nec1 gene and the intergenic region between nec1 and the 5' transposase pseudogene ORFtnp were successfully amplified by polymerase chain reaction from S. scabies ATCC 49173 and the pathogenic Finnish strains of S. scabies, but not from a nonpathogenic strain of S. scabies, three pathogenic and two nonpathogenic strains of S. turgidiscabies, and S. aureofaciens.  相似文献   
104.

Purpose

Identifying sources and fluxes of suspended matter within the catchment is vitally important for the water quality of rivers and for establishing sediment management plans. Constituents of suspended particles are of abiotic and biotic origin. In the Elbe, the biotic fraction of suspended particles is mainly composed of phytoplankton biomass. In this study, total seston and phytoplankton are analyzed for their seasonality, their interdependence and temporal trends over three or five decades, respectively.

Materials and methods

The biotic load was separated from the total suspended matter load, and time series of total suspended substances (seston) (1964 to 2015) and chlorophyll a values (1985 to 2015) were analyzed. Our analyses focused on the seasonal dynamics, long-term trends, and the correlation to hydrological events.

Results and discussion

The mean share of phytoplankton in total seston accounted for 24% in summer months (April–September), with a negative correlation between discharge and total seston, and 11% in winter months (October–March), with a weak positive correlation between discharge and total seston. The long-term trend of seston load was decreasing, while phytoplankton load did not show a significant trend.

Conclusions

Autochthonous biogenic portions should not be neglected in the budget of total suspended matter loads in the Elbe catchment. Our results indicate that land-use and industrial changes subsequent to the German reunification mainly caused the observed trend. Phytoplankton growth superimposes the seasonal dynamics of seston in summer, whereas in the long term, decreasing mineral fraction dominates the significantly decreasing trend.
  相似文献   
105.
Kerkoud M  Manceau C  Paulin JP 《Phytopathology》2002,92(10):1077-1083
ABSTRACT The identification and detection of Pseudomonas syringae pv. papulans, the causal agent of blister spot of apple, on apple leaves and fruit was achieved by polymerase chain reaction amplification of a specific DNA fragment of the hrpL sequence. The consensus primers hrpL(1) and hrpL(2) were designed based on the alignment of pseudomonad hrpL gene sequences available in nucleic acid data banks. This primer set produced a 631-bp amplicon from 37 of the 57 pseudomonads strains tested. These strains belonged to genomospecies 1 and 2, as described by Gardan et al. (8). The amplicon obtained from 30 of these strains was digested with eight restriction enzymes. Three different restriction patterns were produced from strains belonging to genomospecies 1, resulting in A1 and A2 patterns, while strains belonging to genomospecies 2 were characterized by a B pattern. Patterns A1 and A2 differed at only two sites, a Bsp 143I site located at nucleotide 360 and a MseI site located at nucleotides 22-24. Group A2 consisted solely of P. syringae pv. papulans strains. The hrpL gene in P. syringae pv. papulans strain CFBP3323 was sequenced. Two primer sets, Pap1/Pap2 and Pap1/Pap3, were designed and tested for specificity to P. syringae pv. papulans. These primers amplified expected fragments of 242 and 303 bp, respectively. Pap1/Pap2 amplified a fragment only with P. syringae pv. papulans DNA, while Pap1/Pap3 amplified all tested strains belonging to genomospecies 1. A diagnostic procedure using the Pap1/Pap2 primer set was successful for the detection of P. syringae pv. papulans in diseased fruit and artificially inoculated leaves.  相似文献   
106.
Objective To examine associations between late event-related cerebral potential amplitudes and behavioural responses to noxious electrical stimulation as an indicator of acute pain in sheep.
Design Analysis of variance for the effects of stimulus intensity on the behaviour and event-related cerebral potential variables.
Procedure Ninety-six brief constant current electrical pulse trains were presented to the front left leg of eight sheep at four intensities (2.5 to 10 mA) in a randomised order. An event-related cerebral potential and a graded flinch response were recorded for each stimulus and the 24 event-related cerebral potentials at each intensity were averaged to produce a mean waveform. Various components of this waveform were analysed and changes in these measures and the sheep's flinch response, as stimulus intensity increased, were determined.
Results Both the flinch response and some event-related cerebral potential components, that is, peak amplitudes 114 {N1}, 187 {P1}, 318 {P2} and 230 {Pm} ms after stimulus onset, were significantly affected as stimulus intensity increased.
Conclusion These corresponding behavioural and event-related cerebral potential changes indicate the usefulness of using changes in the event-related cerebral potential to measure acute pain in sheep.  相似文献   
107.
Pyogranulomatous panniculitis due to infection by Mycobacterium smegmatis was diagnosed in two cats in Finland, a country with a rather cold climate. The diagnosis was confirmed by sequencing of the 16S rRNA gene, which gave a perfect match with the M smegmatis strain ATCC 19420. Gene sequencing makes it possible to distinguish M smegmatis from closely related mycobacteria such as M goodii sp.nov. Diagnosing this entity seems to be a question of having a high index of suspicion. The appearance of the disease as well as sampling is described in detail. In our first case an initial erroneous diagnosis of Nocardia species considerably delayed our arriving at the right diagnosis. The first patient has now been followed for more than 7 years. Her disease is chronic, but she is not systemically affected. Several antimicrobials were tried. Probable side effects of enrofloxacin medication are described.  相似文献   
108.
Ear tags impregnated with 20% diazinon were evaluated for their efficacy against the buffalo fly (Haematobia irritans exigua) on beef cattle in southern Queensland. Buffalo fly numbers and weight changes were recorded and diazinon residues in tissues of beef cattle and milk from lactating dairy cattle were assayed at different time intervals after tagging. In 2 efficacy trials conducted over 19 and 20 weeks, the mean numbers of buffalo fly on cattle each fitted with ear tags were 1 to 9 and 0 to 16, respectively, in trials 1 and 2, compared with 44 to 345 and 26 to 306 per head on untreated herds, respectively, despite regular spraying of the untreated herd in trial 1 with cyper-methrin to reduce fly burdens. Percentage buffalo fly control was 96.7 to 99.5% and 89.3 to 100% in the 2 trials. Cattle fitted with ear tags gained an average of 94 kg body weight after 5 months compared with 61 kg in the untreated herd, a net increase of 60% in treated animals compared with 28% in the untreated herd. Mean diazinon residue concentrations in the fat of perianal tissue biopsies were 0.02 to 0.03 mg/kg 1 to 8 weeks after tagging. Mean diazinon residue concentrations in the butterfat of milk from lactating dairy cattle were 0.01 to 0.04 mg/kg after tagging.  相似文献   
109.
110.
Observations were made on the abundance and survival of Haemonchus placei, Cooperia punctata and Oesophagostomum radiatum infective larvae from cattle faecal pats exposed at various times of the year in north Queensland wet tropics. Pats exposed in the hot, wet season yielded abundant larvae on herbage. In the dry season, although low numbers of infective larvae were usual, considerable numbers were produced under conditions of heavy dews on dense herbage. Irrespective of season of deposition of pats, the resulting larvae persisted generally for not longer than 10 to 12 weeks, and in large numbers for only 2 to 6 weeks. The findings suggest that prevention of contamination in the wet season, and in the dry season when light rainfalls are accompanied by heavy dews on dense herbage, will result in low levels of larval infestation on herbage. Rotational grazing in the area is suggested as a means of worm control.  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