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   215篇
  免费   11篇
  国内免费   2篇
林业   11篇
农学   8篇
基础科学   1篇
  28篇
综合类   13篇
农作物   16篇
水产渔业   23篇
畜牧兽医   109篇
植物保护   19篇
  2023年   3篇
  2021年   3篇
  2020年   6篇
  2019年   7篇
  2018年   6篇
  2017年   1篇
  2016年   5篇
  2015年   8篇
  2014年   10篇
  2013年   7篇
  2012年   23篇
  2011年   20篇
  2010年   4篇
  2009年   7篇
  2008年   15篇
  2007年   8篇
  2006年   13篇
  2005年   10篇
  2004年   10篇
  2003年   9篇
  2002年   16篇
  2001年   10篇
  2000年   6篇
  1999年   7篇
  1998年   2篇
  1997年   2篇
  1994年   2篇
  1992年   1篇
  1991年   1篇
  1990年   1篇
  1988年   2篇
  1980年   1篇
  1977年   1篇
  1974年   1篇
排序方式: 共有228条查询结果,搜索用时 31 毫秒
21.
22.
Primary flexor enthesopathy is a recently recognized elbow disorder and should be considered in the differential diagnosis of elbow lameness. For treatment planning purposes, it is important to make a distinction between primary and concomitant forms of the disease. The purpose of this prospective study was to compare radiographic findings for dogs with primary flexor enthesopathy (n = 17), concomitant flexor enthesopathy (n = 24), elbow dysplasia (n = 13), and normal dogs (n = 7). All dogs underwent a complete radiographic examination and each radiographic image was evaluated for the presence or absence of following characteristics: irregular medial humeral epicondyle, spur and calcified body. Additionally, the presence or absence of other elbow disorders (medial coronoid process disease, osteochondritis dissecans, ununited anconeal process, incongruity, subtrochlear sclerosis, and osteoarthritis) was recorded. Radiographic characteristics of flexor enthesopathy were found in 86% of painful joints in the primary flexor enthesopathy group and in 100% of painful joints in the concomitant flexor enthesopathy group. Radiographic characteristics of flexor enthesopathy were not found in sound elbow and elbow dysplasia groups. Frequencies and details of individual radiographic characteristics did not differ between primary and concomitant flexor enthesopathy groups. Findings support the use of radiography as a first screening method for detection of flexor enthesopathy, but not as a technique for distinguishing primary vs. concomitant forms.  相似文献   
23.
The aim of this study is to investigate the dynamic gut microbial diversity in weaning swine after administering feed supplemented with probiotic bacteria that specifically inhibit the activity of quorum molecules. Initially, the universal quorum molecule autoinducer‐2 (AI‐2) bioassay results indicated that AI‐2 activity was profoundly inhibited in enterohemorrhagic Escherichia coli (EHEC) O157:H7 in the presence of Lactobacillus acidophilus strain 30SC cell extract, although the growth of EHEC was not affected. Based on plate counting results, bacterial community analysis revealed a specific reduction in coliforms compared to the control, whereas the population of lactobacilli increased in weaning swine in in vivo trials. Supplementation with L. acidophilus strain 30SC did not affect the counts of other communities, such as total aerobes and yeast/mold. In addition, PCR‐denaturing gradient gel electrophoresis analysis showed a significant difference in the 16S rRNA gene products after administering L. acidophilus strain 30SC. Selected bands were sequenced, and most of them were identified as uncultured bacterium clones or a Lactobacillus‐ and Bifidobacterium‐specific community. Therefore, our results indicate that quorum‐quenching probiotic bacteria can significantly modulate the gut microbiota of swine and these beneficial effects can contribute to the improvement of performance and health in the gastrointestinal tract of weaning pigs.  相似文献   
24.
The sensitivity and specificity of recombinant open reading frame 5 products used in the Western blotting assay for confirmation of porcine reproductive and respiratory syndrome virus (PRRSV) serologic status were evaluated. The recombinant antigen-based assays were specifically compared with a commercial enzyme-linked immunosorbent assay (ELISA) for PRRSV antibodies using 1) PRRSV antibody-negative reference sera (n = 30), 2) naturally infected pig sera (n = 40), 3) sequential sera obtained from 24 experimentally infected pigs, and 4) sera submitted to 3 state diagnostic laboratories (n = 200). The recombinant antigen assay yielded an average increased sensitivity of 10% over the commercial PRRSV ELISA. The negative controls (group 1 sera) showed no difference between the 2 assays. This comparison confirmed that the recombinant antigen-specific assay was more sensitive than the commercial ELISA and is well suited for routine confirmation of the presence of PRRSV antibodies.  相似文献   
25.
We retrospectively evaluated the medical records and obtained follow-up information for nine horses which had been treated for cecocolic intussusception (CCI) between January 1982 and April 1998. During the 16-year study period, CCI was diagnosed in nine of 748 horses in which exploratory celiotomy was undertaken for abdominal pain, representing an incidence of 1.2%. Most affected horses (78%) were less than four years of age (median age was 12 months, age range was five months to 15 years). Cecocolic intussusception affected male horses (78%) more commonly than female horses. The most common clinical presentation was abdominal pain of a severe, acute nature or milder but recurrent signs of abdominal pain persisting in spite of conservative treatment for several days. Correction of CCI by either simple reduction or reduction followed by partial typhlectomy was successful if compromise of the intestine by devitalization and adhesion formation was not found at surgery. Definitive diagnosis of CCI necessitates exploratory celiotomy, although an ultrasonographic examination of the abdomen may confirm the diagnosis in some cases. When recognized early during the course of disease, surgical correction of CCI is associated with a favorable outcome; of the eight horses which underwent surgery in our series, five horses (63%) survived surgical correction of CCI. Handling of compromised gut during reduction of CCI necessitates extreme caution because the risk of intestinal tearing is quite high.  相似文献   
26.
Riemerella anatipestifer is a gram-negative rod-shaped bacterium associated with epizootic infections in poultry. A total of 35 R. anatipestifer isolates including the type strain ATCC11845T, reference and field strains for 18 different serotypes were characterized by repetitive sequence based-PCR (rep-PCR) with outwardly-directed primers based on the repetitive extragenic palindromic (REP) consensus sequence. This technique was applied by using either extracted genomic DNA or preparation of whole bacterial cells harvested directly from plate cultures. Rep-PCR discriminated the R. anatipestifer isolates into 19 electrophoretic types. DNA fingerprints obtained from rep-PCR of extracted genomic DNA or from preparations of whole cells yielded comparable patterns. Substantial variation was seen among the rep-PCR fingerprints of different serotypes. Moreover, different polymorphisms of the rep-PCR fingerprints were evident among epidemiologically unrelated isolates of the same serotype. These results suggest the presence of repetitive extragenic palindromic-like elements within the genome of R. anatipestifer that can be used in some isolates to discriminate between different strains belonging to the same serotype. Rep-PCR may serve as a useful molecular tool for subtyping R. anatipestifer isolates for epidemiologic investigations. The whole cell procedure offers the advantage of ease of performance requiring only small quantities of cells.  相似文献   
27.
A Bayesian population modelling tool integrating separable virtual population analysis, per‐recruit models and age‐structured demographic analysis was developed for the bigeye thresher Alopias superciliosus (Lowe) population in an area subset of the western North Pacific. The mortality rates for years 1989–2016 were estimated, various biological reference points and associated risks of decline were also estimated, and alternative harvest strategies for the stock were evaluated. Estimates of the posterior mean of fishing mortality for bigeye thresher shark suggest fishing pressure has been high in recent years (2011–2016). The estimated population growth rate (λ) (without fishing) obtained from age‐structured demographic model was relatively low (λ = 1.01 per year; 95% confidence intervals of 1.00 and 1.03 per year). Risk analyses revealed that only low levels of fishing pressure (10% of the current fishing pressure) over a wide range of ages could maintain a relatively low risk of population decline for bigeye threshers. Sensitivity testing indicated that the model is robust to prior specification. The developed framework could be used as an assessment tool to evaluate the risk of decline for other widely distributed pelagic shark species where insufficient catch and effort data are available.  相似文献   
28.
The new benzenesulfonylurea K-11451, an α-hydroxy-β-fluoropropyl- compound, applied at 3–9 g ha −1, controlled annual and perennial weeds grown in submerged paddy soil under greenhouse conditions. It effectively controlled barnyardgrass at growth stages varying from pre-emergence to the five-leaf stage. The compound inhibited acetolactate synthase, I50 values for the enzyme isolated from barnyardgrass and rice being 56 and 67 nM , respectively. K-11451 inhibited the growth of rice when it was transplanted at a shallow depth (0–1 cm) and water leaching from the paddy soil was high (3–5 cm per day). With a water depth of 3 cm, the compound appeared to move readily down into the paddy soil and had the relatively short half-life of 15.2 days under submerged paddy conditions. A mixture of K-11451 + mefenecet + daimuron (9 + 250 + 250 g ha−1) controlled almost all weeds in the paddy field without injury to rice, so that the combination could be used as a ‘one-shot’ herbicide in rice culture.  相似文献   
29.
Low pressure curing method with iodine vapor was used on low softening temperature polycarbosilane (PCS) precursor for fabrication of continuous SiC fiber at relatively low temperature. The low curing temperature can provide with a wide range of softening temperature PCS precursors, especially with low softening PCSs, which have a good spinnability, but many difficulties with conventional oxidation curing method. The low pressure curing method having the presence of iodine vapor have shown the more positive effect on pyrolysis with early stage crystallization of β-SiC at 1300 °C. Crystal size of β-SiC, cured at 0.008 kPa is around 2–3 nm larger than cured at 101 kPa. In addition, the higher tensile strength of SiC fiber at elevated temperature can be obtained at 0.008 kPa with a value of 2.1 GPa, compare to 1.3 GPa at 101 kPa of curing pressure condition.  相似文献   
30.
This experiment was conducted to evaluate the varietal differences of spikelet sterility response to air temperature during the reproductive stage. Six rice varieties differing in maturity group (early-maturing; Unkwangbyeo, Odaebyeo, medium-maturing; Andabyeo, Hwasungbyeo, and mid-late maturing; Donganbyeo, Chuchungbyeo) were grown under ambient temperature (AT) conditions before being transferred to the temperature-controlled plastic houses. For the synchronization of the growth stage, 15 rice seedlings (2011) and 10 rice seedlings (2012) per pot were transplanted in a circle and only main stems were grown by removing tillers at early stage of their emergence. At the initial heading stage, pots for each variety were transferred to the four plastic houses that were controlled to AT, AT + 1.5°C, AT + 3.0°C, and AT + 5.0°C, respectively. Spikelet fertility was significantly decreased due to high temperature-induced spikelet sterility at AT + 3.0 and/or AT + 5.0°C treatment during flowering time in 2011. Spikelet fertility in 2012 was much lower than in 2011 even at the AT treatment because of high temperature-induced spikelet sterility at the micosporogenesis stage. Critical temperature (Tc) that induces 50% spikelet sterility at flowering time was estimated by fitting the temperature response of spikelet fertility to a logistic function. Tc ranged from 34.6°C (Odaebyeo) to 39.7°C (Hwasungbyeo), Odaebyeo being significantly more sensitive to high temperature-induced spikelet sterility than the other varieties. This result has shown that response of spikelet sterility to higher temperature is different according to rice varieties. However, further study should be done to arrive at a concrete conclusion.  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