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   934篇
  免费   25篇
林业   67篇
农学   22篇
基础科学   3篇
  225篇
综合类   57篇
农作物   52篇
水产渔业   32篇
畜牧兽医   366篇
园艺   10篇
植物保护   125篇
  2023年   6篇
  2022年   13篇
  2021年   25篇
  2020年   20篇
  2019年   19篇
  2018年   30篇
  2017年   18篇
  2016年   22篇
  2015年   4篇
  2014年   21篇
  2013年   28篇
  2012年   71篇
  2011年   96篇
  2010年   23篇
  2009年   20篇
  2008年   93篇
  2007年   76篇
  2006年   73篇
  2005年   67篇
  2004年   58篇
  2003年   54篇
  2002年   57篇
  2001年   11篇
  2000年   22篇
  1999年   8篇
  1998年   9篇
  1997年   2篇
  1996年   2篇
  1994年   1篇
  1993年   1篇
  1989年   1篇
  1988年   1篇
  1987年   2篇
  1983年   1篇
  1977年   1篇
  1976年   1篇
  1926年   2篇
排序方式: 共有959条查询结果,搜索用时 15 毫秒
101.
Thirteen orf virus isolates obtained during the time period between 1995 and 2004 from crusted scab lesions of nine sheep and four goats from different geographical areas of Greece and Italy with suspected contagious ecthyma infection were analyzed. DNA of all isolates was successfully amplified by PCR with the primers 045F-045R and identified them as parapox virus. Partial DNA sequence of orf virus interferon resistant (VIR) gene, phylogenetic analysis of the available isolates and amino acid comparison of the interferon resistance protein encoded by this genomic region was carried out. According to the results of the present report a precise characterisation of the genomic region studied might provide evidence for the genetic variation and movement of the circulating orf virus strains.  相似文献   
102.
103.
Fossils of a giant sauropod dinosaur, Turiasaurus riodevensis, have been recovered from terrestrial deposits of the Villar del Arzobispo Formation (Jurassic-Cretaceous boundary) of Riodeva (Teruel Province, Spain). Its humerus length (1790 millimeters) and estimated mass (40 to 48 metric tons) indicate that it may have been the most massive terrestrial animal in Europe and one of the largest in the world. Phylogenetic analysis indicates that the fossil represents a member of a hitherto unrecognized group of primitive European eusauropods that evolved in the Jurassic.  相似文献   
104.
105.
Transformation of Kalancho? blossfeldiana ‘Molly’ using the naturally occurring bacterium Agrobacterium rhizogenes is a non-GMO strategy to breed compact plants. In the present study, crosses resembling a commercial breeding strategy were made to determine if the improved ornamental quality observed in the T1 generation was inherited to the offspring. F1 lines were produced by crossing the commercial Kalancho? cultivar ‘Sarah’ with a selected T1 line. Subsequently, F2 populations were produced by self-pollination of individual selected lines. The rol-genes were inherited to the progeny and the presence of rol-genes was confirmed in all F1 and many F2 plant lines exhibiting dwarfism. Screening of F1 and F2 plants showed that the rol-genes were inherited together. Besides decreased plant height, several F1 and F2 lines containing rol-genes exhibited changes in plant diameter, number of branches, flower diameter and time to first open flower and duration of flowering compared to the WT ‘Molly’. Furthermore, increased ethylene tolerance was observed in several lines containing rol-genes compared to the WT ‘Sarah’. Screening of three selected F2 populations derived from self-pollination of F1 lines containing rol-genes indicated a shift in distribution towards a lower mean plant height within the entire plant population compared to a control population of plants without rol-genes. Moreover, one of these F2 populations also exhibited earlier flowering compared to the control population. Compact potted plants and lines without delayed flowering and with improved ethylene tolerance were obtained and are valuable in commercial breeding programmes without using recombinant DNA technology.  相似文献   
106.
An 11-year-old, 24-kg, intact female Siberian husky dog in anestrus had a 2-month history of polyuria and polydipsia. The dog had signs of mineralocorticoid excess such as hypertension and hypokalemia refractory to potassium supplementation. Abdominal ultrasound revealed an irregular mass in the left adrenal gland. The ACTH stimulation test for aldosterone concentration did not reveal hyperaldosteronism. Unilateral adrenalectomy was performed and histopathology identified adrenal cortical carcinoma. All clinical signs of mineralocorticoid excess ceased after surgery.  相似文献   
107.
Participatory research methods have helped scientists to understand how farmers experiment and to seek partnerships with farmers in developing technologies with enhanced relevance and adoption. This paper reports on the development of a participatory methodology to systematize long-term experimentation with agroforestry systems carried out in a hotspot of biodiversity by non-governmental organizations and local farmers. A methodological guide for systematization and techniques used for Participatory Rural Appraisal formed the basis of our work. We propose an analytical framework that recognizes systems of reflexive and learning interactions, in order to make the learned lessons explicit. At the process level, the main lessons and recommendations are as follows. It is important to establish partnerships to conduct innovative and complex experimentation with agroforest. Participatory systematization allows us to improve the methodological aspects of design, implementation and management of on-farm participatory experimentation. It also serves to synthesize the main findings and to extract lessons from agroforestry systems experiments. It fosters the technical improvement of agroforestry systems. It creates possibilities for reflection on agroforestry systems by farmers, extensionists and researchers, as well as their learning with respect to management of such systems. The findings are placed in the context of current theory on participatory experimentation in agriculture. Extractive and interactive approaches help to produce rich insights of mutual interest through collaboration by identifying local, regional and global convergences, complementarities, and conflicts of interest; which affect the advance of new eco-friendly technologies, to both improve the livelihoods and to reverse biodiversity loss and environmental degradation.  相似文献   
108.
The formulations of acaripathogenic fungi to control ticks have been widely studied. The present study evaluated the efficacy of oil-based formulations of Metarhizium anisopliae sensu lato (s.l.), isolate Ma 959, and Beauveria bassiana, isolate Bb 986, on different Rhipicephalus microplus stages, comparing the efficacy between aqueous suspensions and 10, 15 and 20% mineral oil formulations. Twelve groups were formed: one aqueous control group; three mineral oil control groups, at 10, 15 or 20%; two aqueous fungal suspensions of M. anisopliae s.l. or B. bassiana; and three formulations of M. anisopliae (s.l.) or B. bassiana containing 10, 15, and 20% mineral oil. To prepare aqueous suspensions and oily formulations, fungal isolates were cultivated on rice grains in polypropylene bags. The conidial suspensions and formulations had a concentration of 10(8)conidia/mL. Bioassays were repeated twice. After treatment, the following biological parameters of engorged females were evaluated: hatching percentage, egg production index, nutritional index, and percentage of tick control. The following parameters were evaluated in the bioassays with eggs: period of incubation, period of hatch, and hatching percentage. Mortality was evaluated in bioassays with larvae. M. anisopliae s.l. and B. bassiana oil-based formulations were more effective than aqueous suspensions against R. microplus eggs, larvae and engorged females, however, there was no significant difference between the three oil concentrations used. M. anisopliae s.l. and B. bassiana formulated in mineral oil reached 93.69% and 21.67% efficacy, respectively, while M. anisopliae s.l. and B. bassiana aqueous suspensions attained 18.70% and 1.72% efficacy, respectively. M. anisopliae s.l. oil-based formulations caused significant effects in all biological parameters of engorged females while B. bassiana oil-based formulations modified significantly the nutritional index only. Eggs treated with M. anisopliae s.l. and B. bassiana oil-based formulations showed hatching rates that decreased 102.5 and 3.65 times, respectively. In the bioassay with larvae, M. anisopliae s.l. oil-based formulations caused nearly 100% mortality five days after treatment, while larva treated with B. bassiana oil-based formulations reached 100% mortality at day 20 after treatment. Larva from oil-based control groups showed mortality at day 15 after treatment, which indicated a possible toxic effect of the oil for this R. microplus stage. The results showed that the fungal mineral oil formulations tested were more effective than the aqueous suspension. Oil-based formulations at 10, 15 and 20% enhanced the activity of M. anisopliae s.l. Ma 959, and B. bassiana Bb 986, isolates against R. microplus eggs, larvae, and engorged females tick. Mineral oil was effective as an adjuvant in formulations of M. anisopliae s.l., Ma 959, and B. bassiana, Bb 986, for the control of R. microplus under laboratory conditions.  相似文献   
109.
Intra-mammary (IM) bacterial infection in cattle can result in clinical outcomes that range from being acute and life-threatening to those that are chronic and sub-clinical. The typical bacteria involved in IM bacterial infections activate the mammary immune system in different ways which can influence the severity of the outcome. A clear understanding of the mechanisms that activate and regulate this response is central to the development of effective preventative and treatment regimes. This review focuses on the different immune responses of the bovine mammary gland to common mastitis-causing pathogens. There is special emphasis on comparing the responses to Escherichia coli and Staphylococcus aureus infections, as these are typically associated, respectively, with acute/severe and chronic/sub-clinical forms of the disease.  相似文献   
110.
The Aerococcus viridans isolates from bovine mastitis in Slovakia were isolated and characterized by classical microbiological and biochemical, and molecular techniques including IGS-PCR and rep-PCR, ARDRA and 16S rDNA gene sequencing. The substantial variability of antibiotic resistance patterns was observed. The majority of strains were resistant to beta-lactam antibiotics, the resistance to tetracycline was observed in 3 tested strains, resistance to lincomycin was found in 4 strains and practically all tested strains were sensitive to neomycin and ciprofloxacin. While variable at a phenotypic level, no significant genetic variability among A. viridans isolates was detected by molecular DNA based methods. The data obtained suggest that a few A. viridans strains spread among cow's population in Slovak farms.  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