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   172篇
  免费   16篇
林业   11篇
农学   11篇
  32篇
综合类   5篇
农作物   6篇
水产渔业   26篇
畜牧兽医   81篇
园艺   1篇
植物保护   15篇
  2023年   1篇
  2022年   4篇
  2021年   3篇
  2020年   4篇
  2019年   7篇
  2018年   4篇
  2017年   7篇
  2016年   11篇
  2015年   4篇
  2014年   4篇
  2013年   10篇
  2012年   8篇
  2011年   15篇
  2010年   4篇
  2009年   11篇
  2008年   6篇
  2007年   10篇
  2006年   10篇
  2005年   8篇
  2004年   4篇
  2003年   6篇
  2002年   6篇
  2001年   3篇
  2000年   4篇
  1999年   4篇
  1998年   3篇
  1997年   2篇
  1996年   1篇
  1995年   2篇
  1993年   3篇
  1992年   4篇
  1990年   2篇
  1988年   2篇
  1987年   1篇
  1985年   1篇
  1981年   1篇
  1979年   1篇
  1978年   2篇
  1976年   1篇
  1974年   3篇
  1973年   1篇
排序方式: 共有188条查询结果,搜索用时 15 毫秒
31.
The IgG antibody response to Calicophoron daubneyi (Digenea: Paramphistomidae) excretory/secretory antigens was evaluated in naturally infected cattle from Lugo (Galicia, NW Spain) by using an ELISA procedure. Two studies were conducted, first a survey in 524 cattle separated into three groups according to age, G-1 (0–2 years old), G-2 (3–5 years old) and G-3 (>6 years old). In the second study, three groups of cattle were employed: G-I, naturally infected; G-T, naturally infected and treated with oxyclozanide plus levamisole (Nilzan Plus®); G-C, cattle maintained in a farm where C. daubneyi has never diagnosed. Variations on egg-output and haematic parameters (erythrocytes, haematocrite, leukocytes and lymphocytes) were also analyzed.

The ELISA procedure showed that 61.2% of the cattle in the first study had been exposed to the trematode, but only 10.1% passed eggs in the feces. Age-association with egg-output was shown but not with the IgG values. In the second experiment, the administration of the anthelmintic reduced significantly the IgG kinetic levels and the C. daubneyi-egg-output was suppressed during 12 weeks in the G-T group. The values of red cells, haematocrite, leukocytes and lymphocytes increased significantly in the treated cattle 5 weeks after chemotherapy; however, new reduction after week 5 was recorded, as results of the challenge of these cattle.

This is the first investigation in which evaluation of the IgG humoral response against C. daubneyi in cattle has been carried out. We proved that a notable IgG response in naturally infected cattle is induced, and can be detected by using an ELISA procedure. The IgG antibodies did not increase after challenge infection. Our results proved an important percentage of cattle were exposed to this trematode in the area of study and suitable measures for preventing this relationship must be considered.  相似文献   

32.
Advocates, practitioners and policy-makers continue to use and advocate for marine protected areas (MPAs) to meet global ocean protection targets. Yet many of the worlds MPAs, and especially no-take MPAs, are plagued by poaching and ineffective governance. Using a global dataset on coral reefs as an example, we quantify the potential ecological gains of governing MPAs to increase compliance, which we call the ‘compliance gap’. Using ecological simulations based on model posteriors of joint Bayesian hierarchical models, we demonstrate how increased compliance in no-take MPAs could nearly double target fish biomass (91% increases in median fish biomass), and result in a 292% higher likelihood of encountering top predators. Achieving these gains and closing the compliance gap necessitates a substantial shift in approach and practice to go beyond optimizing enforcement, and towards governing for compliance. This will require engaging and integrating a broad suite of actors, principles, and practices across three key domains: (i)) harnessing social influence, (ii) integrating equity principles, and (iii) aligning incentives through market-based instruments. Empowering and shaping communication between actor groups (e.g., between fishers, practitioners, and policy-makers) using theoretically underpinned approaches from the behavioural sciences is one of the most essential, but often underserved aspects of governing MPAs. We therefore close by highlighting how this cross-cutting tool could be further integrated in governance to bolster high levels of compliance in MPAs.  相似文献   
33.
Characterization of cider apples on the basis of their fatty acid profiles   总被引:1,自引:0,他引:1  
In the current study, the fatty acids composition of 30 monovarietal apple juices from six cider apple varieties belonging to two categories was analyzed. The different apple juices were obtained from three consecutive harvests (1997, 1998, and 1999). The fatty acids concentration in apple juice together with chemometric techniques such as principal components analysis (PCA), soft independent modeling of class analogy (SIMCA), and linear discriminant analysis (LDA), allowed us to differentiate apple juices on the basis of the sweet or sharp category to which the cider apple variety belongs. Fatty acids such as the unsaturated oleic and linoleic acids, and saturated caprylic, capric, stearic, and palmitic acids were related to the sweet cider apple category, while pentadecanoic acid is related to the sharp class.  相似文献   
34.
Intra‐ and interspecific characteristics of fish‐pathogenic Edwardsiella ictaluri, and E. tarda were determined by numerical analysis of gel electrophoresed protein profiles, fatty acid methyl esters (FAMEs) and immunoblotting. The 18 E. ictaluri isolates revealed a high degree of homogeneity (70% similarity or higher) in their protein profiles and 95% similarity in their FAME, while the nine E. tarda isolates revealed 30% similarity in their protein profiles and 95% similarity in their FAME. Immunoblots probed for antigenic epitopes with goat antiserum produced against E. ictaluri and E. tarda, respectively, revealed that E. ictaluri were more homogeneous compared with the E. tarda isolates. Overall, there was a considerable degree of relatedness between the two species. Our findings suggest that phenotypically E. ictaluri represents a clonal bacterial population structure compared with the less monomorphic E. tarda.  相似文献   
35.
At the end of September 2000, clinical symptoms of Bluetongue appeared in sheep flocks of the Balearic Islands (Spain). The presence of the BTV serotype 2 in tissue and blood samples of affected animals was confirmed by laboratory techniques. A systematic vaccination were carried out in affected areas using a live monovalent serotype 2 vaccine available from Onderstepoort laboratory (South Africa). In order to perform epidemiological studies, a new method to differentiate between the NS1 genes of BTV-2 affecting the Balearic islands and that of the Onderstepoort commercial live virus vaccine (monovalent, serotype 2) has been developed. This procedure is based on the use of an RT-PCR, followed by restriction endonuclease analysis. Epidemiological data of a study carried out in the period January-October 2001 using this procedure are included.  相似文献   
36.
‘Blanquilla’ pears processed as fresh-cut products are highly sensitive to browning and softening. Common postharvest methods, such as the use of antibrowning compounds and/or modified atmosphere packaging, fail to preserve ‘Blanquilla’ pear slices long enough to be marketable. However, treatment with 1-MCP before cutting and peeling considerably improved their textural properties (9.2 N vs. 1.1 N with and without 1-MCP treatment, respectively) and color (a* values of 1 vs. 5 after 15 d at 4 °C, for slices pear treated with 1-MCP and without treatment, respectively). These positive changes were closely related to a decrease in respiratory activity determined on whole pears after 3 months of storage in air at 0 ± 1 °C and 95% R.H. (0.40 ± 0.05 mmol CO2 kg−1 h−1 vs. 0.77 ± 0.04 mmol CO2 kg−1 h−1 with and without 1-MCP treatment, respectively) and ethylene production (1.18 ± 0.36 nmol C2H4 kg−1 h−1 vs. 5.751 ± 1.12 nmol C2H4 kg−1 h−1 for samples treated with and without 1-MCP, respectively). The use of 1-MCP allows fresh-cut ‘Blanquilla’ pears to be sold up to about 5 d after processing. Treatment with 1-MCP could be a viable alternative to common technologies for extending the shelf-life of ‘Blanquilla’ pears as a fresh-cut product.  相似文献   
37.
The effect of micellar aggregates upon the stability of carbofuran in basic media has been studied. The effect of the presence of micelles upon the basic hydrolysis of carbofuran is a function of the nature of the surfactant monomer. Important catalysis of basic hydrolysis of carbofuran in the presence of colloid aggregates with positive surface charge has been reported. On the other hand, the presence of anionic and nonionic surfactants implies a large inhibition of the basic hydrolysis of carbofuran. Both catalysis and inhibition are due to the association of carbofuran with the micellar core. The kinetic constants for the basic hydrolysis of carbofuran in these microheterogeneous media have been obtained on the basis of a micellar pseudophase model. No significant changes in the intrinsic reactivity of HO- against carbofuran have been observed.  相似文献   
38.
Jacaratia mexicana A. DC. (Caricaceae) is a tropical tree distributed throughout Mexico and Mesoamerica. Some evidence in Mexico indicates the presence of an incipient domestication process in this species. Phylogeographical analyses can potentially determine contemporary patterns of gene flow, isolation between population lineages, as well as historical processes such as population bottlenecks or expansions on their geographical areas. In this study we reconstruct the phylogeographical patterns in populations of J. mexicana A. DC., in order to find differences between genetic variation among wild and cultivated populations utilizing chloroplast DNA and nuclear DNA sequences. We generate a Bayesian phylogenetic tree, to estimate the divergence time between clades using calibrated mutation rates. We also infer the demographic history of these populations using neutrality tests among wild and cultivated accessions. We identified higher levels of haplotype and nucleotide diversity for the cpDNA and ITS types in wild populations than in domesticated populations. These results indicate a reduction of genetic diversity derived from human selection on domestication traits. Neutrality test suggests population expansion detected by the significant negative values of Fu’s Fs in the cultivated populations of this specie. These process results in an excess of rare polymorphism with the fixation of certain advantageous mutation throughout time, this implication are in accordance with the role of the strong selection in the fruit traits of J. mexicana. The dated phylogeny constructed with BEAST program indicated a dispersion pattern for the J. mexicana ancestors across the South Pacific and South Eastern populations during the late Pliocene. Posterior dispersion and divergence in the clades from Central Mexico and North Pacific are in agreement with the episodes of mountain-building in different regions of Mexico.  相似文献   
39.
A survey of the xylophagous insects in the conifer forests, mainly Pinus pinaster woodlands, in Spain was carried out in order to study the phoretic vectors of nematodes of the genus Bursaphelenchus. Fifteen environmental sites were characterized on the bases of altitude, rainfall, temperature and conifer species. Specimens of Orthotomicus erosus (n = 3476) were captured of which 59% carried nematodes under their elytrous, most of them were aphelenchid fungal‐feeding nematodes, but B. fungivorus was found on the beetles from Las Cumbres, Villa Blanca, (Huelva), southern Spain, which represent the first record of O. erosus as vector of a Bursaphelenchus sp. The nematode is characterized by morphometric and biomolecular techniques and distribution and ecology of the insect is discussed.  相似文献   
40.
The awn and the fur hair of Pudu were investigated. Values of the length are between 14 and 56 mm for the awn hair, and 9 to 36 mm for the fur hair. Hair thickness--especially at the thickest point--ranges from 140 to 236 microns for the awn hair and from 19 to 106 microns for the fur hair. The values of the cuticle scales are between 12 and 18 microns for the length and between 41 and 66 microns for the width. The shape of the scales is rectangular in the basal three quarters (R) and becomes crenated (R/Z) in the apical quarter. The medulla is continuous with large hollow vesicles. The similarity to the hair of european red deer is surprising.  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