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   153篇
  免费   12篇
林业   19篇
农学   5篇
  23篇
综合类   14篇
农作物   9篇
水产渔业   13篇
畜牧兽医   67篇
园艺   3篇
植物保护   12篇
  2023年   1篇
  2021年   3篇
  2020年   7篇
  2019年   9篇
  2018年   10篇
  2017年   10篇
  2016年   4篇
  2015年   7篇
  2014年   3篇
  2013年   9篇
  2012年   7篇
  2011年   8篇
  2010年   3篇
  2009年   5篇
  2008年   9篇
  2007年   8篇
  2006年   7篇
  2005年   4篇
  2004年   4篇
  2003年   8篇
  2002年   9篇
  2001年   4篇
  2000年   4篇
  1999年   7篇
  1998年   1篇
  1997年   1篇
  1996年   2篇
  1995年   1篇
  1992年   1篇
  1991年   1篇
  1990年   1篇
  1989年   1篇
  1970年   3篇
  1968年   1篇
  1967年   1篇
  1966年   1篇
排序方式: 共有165条查询结果,搜索用时 15 毫秒
91.
A 7-year-old castrated male French Bulldog was examined for chronic large intestinal enteropathy. A colonic mass and thickened rectal mucosa were identified, and histopathologic examination of endoscopic biopsy specimens disclosed eosinophilic proctitis with large (5-20 μm), irregularly shaped, pauciseptate hyphae that were Gomori methenamine silver and periodic acid-Schiff positive. Amplification and sequencing of ribosomal DNA extracted from paraffin-embedded tissues yielded a sequence with 97% identity to GenBank sequences for Basidiobolus ranarum. After itraconazole, terbinafine, and prednisone administration, clinical signs resolved rapidly, and sonographic lesions were largely absent after 6 weeks. Treatment was discontinued by the owner 15 weeks after diagnosis. Three weeks later, the dog collapsed acutely and was euthanized. Necropsy identified metastatic islet cell carcinoma and grossly unremarkable colorectal tissues. However, histopathology of the rectum disclosed multifocal submucosal granulomas with intralesional hyphae morphologically similar to those previously observed. This report is the first to describe medical treatment of gastrointestinal basidiobolomycosis in a dog.  相似文献   
92.
A one-way random effects model is considered for the log-transformed shift-long personal exposure measurements, where the random effect in the model represents an effect due to the worker. Following a previous approach, we address a hypothesis-testingproblem involving the proportion of workers for whom the mean exposure exceeds the occupational exposure limit. A confidence interval is constructed for the relevant parameter of interest, following the idea of a previously presented generalized confidence interval. The confidence bound is used for the purpose of testing hypotheses, and the performance of the test is numerically in vestigated. It turns out that the test exhibits satisfactory performance regardless of the sample size, in particular, for small samples. A similar procedure is then employed for testing hypotheses concerning the overall mean exposure. The results are illustrated using examples.  相似文献   
93.
94.
95.
96.
Differences in perceptions and knowledge of crop diseases constitute a major obstacle in farmer–researcher cooperation, which is necessary for sustainable disease management. Farmers’ perceptions and management of crop diseases in the northern Ethiopian Regional State of Tigrai were investigated in order to harness their knowledge in the participatory development of integrated disease management (IDM) strategies. Knowledge of disease etiology and epidemiology, cultivar resistance, and reasons for the cultivation of susceptible cultivars were investigated in a total of 12 tabias (towns) in ten weredas (districts). Perception of diseases involved both scientific and spiritual conceptual frameworks. Of the more than 30 crop diseases recorded on the major crops in the region, only rusts and powdery mildews (locally called humodia) and a few root rots were considered by farmers to be important. Farmers’ awareness of other diseases was extremely low; some highly damaging but less conspicuous diseases, such as faba bean chocolate spot and chickpea ascochyta blight (also called humodia), were not regarded by farmers as disease but as problems caused primarily by excessive soil moisture. Considering that some of these “unrecognized” diseases can cause complete yield loss and genetic erosion in epiphytotic years, there is an urgent need for bringing together farmers’ and scientists’ knowledge to complement each other. Even when farmers had access to disease-resistant or disease-tolerant cultivars, they grew susceptible local varieties because of multiple criteria including earliness, good yield in years with low humodia severity, suitability for home consumption, market demand/quality, and low soil fertility and land management requirements. Farmer innovation and knowledge were evident in their use of diverse disease control measures, but these were a mixture of the “useful and the useless.” Our findings stress the necessity for extension workers and researchers to understand and improve farmers’ knowledge of crop diseases, and farmers’ ability to observe and experiment, through the Farmer Field School or a similar experiential learning approach. These insights about farmers’ knowledge of crop diseases provide a basis for further collaborative maintenance of crop genetic diversity, development of germplasm, and IPM-related research in Africa.
Mathew M. AbangEmail:
  相似文献   
97.
Fusarium wilt, caused by Fusarium oxysporum Schlechtend.: f. sp. ciceris (Padwick) Matuo & K. Sato, is a major production problem in many countries. A study was conducted to develop an integrated management of Fusarium wilt of chickpea using genotypes, sowing dates (January as early sowing and March/April as spring sowing) and fungicide seed treatments under natural infested plots in research plots and farmers’ fields 2007–2009 cropping seasons. In most cases, sowing date and fungicides did not affect disease parameters and seed yield. Chickpea genotypes showed significant differences in seed yield but different responses for disease parameters. Averaged over locations and seasons, the rate of disease development was higher in early (0.035 units day?1) than spring (0.023 units day?1) sowing. Chickpea genotypes showed different responses in affecting rate of disease development and cumulative wilt incidence in early and late sowing periods. Higher mean seed yield (1.3 t ha?1) was recorded in early than late sowing (1.0 t ha?1) of chickpea. The average seed yield reduction due to spring sowing ranged from 9% to 60% and highest yield losses were observed in FLIP-97–706 and Ghab-3. This study showed that integrating January sowing with genotypes having good levels of resistance for Fusarium wilt and Ascochyta blight helps farmers to narrow chickpea yield gaps in Syria.  相似文献   
98.
Browning is a critical problem, which often limits the shelf life and marketability in fresh-cut lotus tuber. Proteome level changes in response to the browning metabolism were investigated using two-dimensional electrophoresis (2-DE) and MALDI-TOF-TOF. A total of 34 functional protein spots were identified by comparing 2-DE protein patterns of fresh-cut lotus tuber before and after browning. These 34 identified proteins could be classified into 7 functional groups based on the NCBI database, that is, material and energy metabolism (35%), stress response (20%), respiration metabolism (12%), cell structure (12%), signal transduction (6%), gene expression regulation (6%), and unclassified proteins (9%). The group with the greatest difference in protein expression was related to material metabolism and regulation, reactive oxygen species metabolism, and respiratory control. The distinct proteins included universal stress protein (USP), superoxide dismutase (SOD), peroxidase (POD), ferritin, and ATPase.  相似文献   
99.
Alkali treatment coupled with high pressure defibrillation and acid treatment have been tried on banana fibers obtained from the pseudo stem of the banana plant Musa sapientum. The structure and morphology of the fibers have been found to be affected on the basis of the concentration of the alkali and acid and also on the pressure applied. Steam explosion in alkaline medium followed by acidic medium is found to be effective in the depolymerization and defibrillation of the fiber to produce banana nanowhiskers. The chemical constituents of raw and steam exploded fibers were analyzed according to the ASTM standards. Structural analysis of steam exploded fibers was carried out by FTIR and XRD. The fiber diameter and percentage crystallinity of the modified fibers were investigated using X-ray diffraction studies. Characterization of the fibers by SFM and TEM supports the evidence for the development of nanofibrils of banana fibers.  相似文献   
100.
Soil food webs influence organic matter mineralization and plant nutrient availability, but the potential for plants to capitalize on these processes by altering soil food webs has received little attention. We compared soil food webs beneath C3- and C4-grass plantings by measuring bacterial and fungal biomass and protozoan and nematode abundance repeatedly over 2 years. We tested published expectations that C3 detritus and root chemistry (low lignin/N) favor bacterial-based food webs and root-feeding nematodes, whereas C4 detritus (high lignin/N) and greater production favor fungal decomposers and predatory nematodes. We also hypothesized that seasonal differences in plant growth between the two grassland types would generate season-specific differences in soil food webs. In contrast to our expectations, bacterial biomass and ciliate abundance were greater beneath C4 grasses, and we found no differences in fungi, amoebae, flagellates, or nematodes. Soil food webs varied significantly among sample dates, but differences were unrelated to aboveground plant growth. Our findings, in combination with previous work, suggest that preexisting soil properties moderate the effect of plant inputs on soil food webs. We hypothesize that high levels of soil organic matter provide a stable environment and energy source for soil organisms and thus buffer soil food webs from short-term dynamics of plant communities.  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