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   109篇
  免费   13篇
林业   10篇
农学   2篇
  22篇
综合类   4篇
农作物   11篇
水产渔业   13篇
畜牧兽医   46篇
园艺   1篇
植物保护   13篇
  2022年   3篇
  2021年   3篇
  2020年   2篇
  2019年   12篇
  2018年   10篇
  2017年   9篇
  2016年   7篇
  2015年   7篇
  2014年   6篇
  2013年   5篇
  2012年   5篇
  2011年   9篇
  2010年   3篇
  2009年   6篇
  2008年   8篇
  2007年   7篇
  2006年   5篇
  2005年   4篇
  2004年   1篇
  2003年   3篇
  2002年   1篇
  2001年   2篇
  2000年   3篇
  1986年   1篇
排序方式: 共有122条查询结果,搜索用时 203 毫秒
1.
2.
Crude extracts and fractions of Bertholletia excelsa stem barks were tested for trypanocidal activity. Acetone and methanol extracts showed significant in vitro trypanocidal activity against trypomastigote form of Trypanosoma cruzi since in the concentration of 500 microg/ml, the parasites were reduced in 100% and 90.3% respectively, whereas the triterpene betulinic acid pure isolated from hexane extract presented 75.4%.  相似文献   
3.
The antibacterial effects of extracts obtained from Persea cordata stem bark, employed in Brazil to treat infectious diseases, were studied. The ethyl acetate fraction of the hydroalcoholic extract showed activity against pathogenic bacteria which may justify the popular use of the plant.  相似文献   
4.
This retrospective study describes the computed tomography (CT) findings in 59 horses presented with diseases of the head over 8 years that underwent CT examination of this region, including dental or sinonasal diseases (Group A) (n = 42), osseous and/or articular diseases (Group B) (n = 11) and soft tissue diseases (Group C) (n = 6). For Group A, radiographic and CT findings comparison was possible. Computed tomography had higher sensitivity (100%) and specificity (96.7%) than radiography in diagnosing dental disease. Compared to CT, radiographic identification of sinus involvement was less sensitive, particularly for ventral conchal and sphenopalatine sinuses and presented an overall sensitivity of 43.5 and 16.7%, respectively. In Group B CT allowed identification of a higher number of bone fragments and fractures in the maxillary, lacrimal, sphenoidal, temporal and zygomatic bones not identified radiographically. Accurate identification of CT changes in the temporomandibular joint and temporohyoid articulation was also possible. Group C included both intra‐ and extra‐cranial disease, retrobulbar masses being the most representative pathology (n = 3). In this group, CT was considered the gold standard for detection of periorbital diseases. We conclude that CT is an imaging technique with high diagnostic value for evaluating the equine head, yielding additional information over multiple radiographic views, which may alter the outcome of the case. Additionally, this paper reports several conditions not previously described using CT.  相似文献   
5.

Yield mapping technologies can help to increase the quantity and quality of agricultural production. Current systems only focus on the quantification of the harvest, but the quality has equal or greater importance in some perennial crops and impacts directly on the financial profitability. Therefore, a system was developed to quantify and relate the quality obtained in the classification line with the plants of the orchard and for decision-making. The system is comprised of hardware, which obtains the location of the harvester bag during harvesting and unloading at the unloading site, and software that processes the collected data. The cloud of real-time data contributed from the different collectors (bins) allows the construction of yield maps, considering the multi-stage harvesting system. Further, the system enables the creation of a detailed map of the plants and fruits harvested. As the harvest focuses on quality, it takes place in stages, depending on the ripening of the fruits. In addition to the yield maps, the system allows identification of the efficiency of each worker undertaking the harvest by the number of performed discharges and by the time spent. The system was developed in partnership with the Federal Technological University of Paraná and Embrapa Uva & Vinho and was tested in apple orchards in southern Brazil. Although the system was evaluated with only data from apple cultivation, monitoring the quality and quantifying other orchard fruits can positively impact the fruit sector.

  相似文献   
6.
To determine the role of the spleen in the pathogenesis of canine visceral leishmaniasis (CVL), we analyzed cellular immunophenotypic profiles of 52 dogs naturally infected with Leishmania infantum, clinically classified as follows: asymptomatic dogs-I (AD-I), seronegative/PCR+; asymptomatic dogs-II (AD-II), seropositive/PCR+; oligosymptomatic dogs (OD) and symptomatic dogs (SD). Seven non-infected dogs (CD) were included as a control group. AD-II presented higher levels of CD8+ T splenocytes and lower TCD4+/TCD8+ ratio in comparison with CD. OD and SD showed lower percentages of CD21+ as compared with AD-II. All seropositive dogs presented lower levels of CD45RA+ than CD. Regardless of the stimuli used, the proliferation index from splenocytes in vitro was inversely correlated with clinical status. After LSA stimulation, there was a higher percentage of specific CD8+ T in AD-II than CD and non-stimulated culture. In contrast, splenocytes from SD under in vitro LSA stimulation induced decreased MHC-II+ expression in comparison with all groups, and non-stimulated culture. In conclusion, the role of CD8+ T splenocytes seems to be important for an effective immunological response, a hallmark of asymptomatic CVL, whereas the pronounced loss of MHC-II expression upon LSA stimulation is a biomarker of symptomatic CVL.  相似文献   
7.

? Context

Pinus pinea L. presents serious problems of natural regeneration in managed forest of Central Spain. The species exhibits specific traits linked to frugivore activity. Therefore, information on plant–animal interactions may be crucial to understand regeneration failure.

? Aims

Determining the spatio-temporal pattern of P. pinea seed predation by Apodemus sylvaticus L. and the factors involved. Exploring the importance of A. sylvaticus L. as a disperser of P. pinea. Identifying other frugivores and their seasonal patterns.

? Methods

An intensive 24-month seed predation trial was carried out. The probability of seeds escaping predation was modelled through a zero-inflated binomial mixed model. Experiments on seed dispersal by A. sylvaticus were conducted. Cameras were set up to identify other potential frugivores.

? Results

Decreasing rodent population in summer and masting enhances seed survival. Seeds were exploited more rapidly nearby parent trees and shelters. A. sylvaticus dispersal activity was found to be scarce. Corvids marginally preyed upon P. pinea seeds.

? Conclusions

Survival of P. pinea seeds is climate-controlled through the timing of the dry period together with masting occurrence. Should germination not take place during the survival period, establishment may be limited. A. sylvaticus-mediated dispersal does not modify the seed shadow. Seasonality of corvid activity points to a role of corvids in dispersal.  相似文献   
8.
Potential antagonists were isolated from the epiphytic flora associated with oranges and pome fruit. A total of 1465 microorganisms were tested in a preliminary screening against blue and green moulds on pome and citrus fruit, respectively. Among them, approximately 3% reduced incidence and severity by more than 50% and 4 microorganisms fulfilled the selection criteria of reduction in severity and incidence by 75%. The most effective was a yeast identified as Metschnikowia andauensis, strain NCYC 3728 (PBC-2), isolated from the surface of ‘Bravo de Esmolfe’ apple fruit cultivated in North Portugal. The biocontrol activity of M. andauensis PBC-2 was dependent on its applied concentration. At 5 × 106 cfu/mL incidence (% of infected wounds) and severity (lesion diameter) were reduced by 62 and 70%, respectively and at 1 × 107 cfu/mL, the greatest reduction was achieved, 90% of incidence and 95% of severity. The broad spectrum of action of M. andauensis PBC-2 was evaluated with effective control being achieved against Rhizopus stolonifer, Penicillium expansum and Botritys cinerea, on ‘Rocha’ pears and on different apple cultivars and against Penicillium digitatum and Penicillium italicum on mandarins and oranges. In semi-commercial trials in cold storage, the reduction of blue mould was 90%. Rapid colonization of fresh apple fruit wounds was observed during the first 24 h of cold storage, followed by a significant population increase during the first 15 days of storage and then the population remained stable until the end of storage.  相似文献   
9.
The inhibitory effects of apple polyphenols (APP) on the synthesis of water-insoluble glucans by glucosyltransferases (GTF) of streptococci of the mutans group and on the sucrose-dependent adherence of the bacterial cells were examined in vitro. APP markedly inhibited the activity of GTF purified from the cariogenic bacterial cells. However, APP showed no significant effect on the growth of the cariogenic bacteria. The strongest GTF inhibitors in APP were apple condensed tannins (ACT), a mixture of procyanidins. The 50% inhibitory doses of ACT against the GTF of S. sobrinus and that of S. mutans were 1.5 microgram/mL and 5 microgram/mL, respectively. The ACT efficacy largely depended upon the degree of polymerization. Interestingly, while the other polyphenols known to inhibit GTF such as tannic acid markedly inhibited salivary alpha-amylase activity, APP and ACT only scarcely inhibited that enzyme activity. This means that APP and ACT might selectively inhibit the bacterial GTF activity under oral conditions.  相似文献   
10.
The effect of 0, 1, 2, 3 and 4 intercross cycles using genetic male sterility on the mean yield and genetic variability of the CNA 5 irrigated rice synthetic population was assessed studying 300 S0:2 (1998/99) and S0:3 (1999/00) families grown in two locations (Lambari, MG and Goianira, GO). Each intercross was investigated using a 8 × 8 triple lattice design experiment containing 60 families and four control cultivars. Five experiments were carried out per location and generation, totaling 20 experiments. Individual, combined over locations, combined over generations and combined over locations and generations analyses of variance were performed. Linear regression equations were fitted to data of each location and generation as well as, genetic and phenotypic parameters were estimated. An average increase of 3.91% in grain yield was obtained with the increase in the number of intercrosses. However, when genetic gains obtained from selection of the five and ten highest yielding families were considered, negative b estimates were always obtained, suggesting a tendency of gain increase reduction with the increase in the number of intercrosses. This was confirmed by the analysis of the means of the best families, since increases in the number of intercrosses did not result in selection of families with greater mean grain yield. The estimates of the genetic variances and heritabilities did not suggest an increase in genetic variability with the increase in intercross cycles. Therefore, carrying out intercrosses on the base population did not improve the results of the irrigated rice recurrent selection program. This revised version was published online in August 2006 with corrections to the Cover Date.  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