全文获取类型
收费全文 | 207篇 |
免费 | 9篇 |
专业分类
林业 | 31篇 |
农学 | 14篇 |
基础科学 | 5篇 |
32篇 | |
综合类 | 9篇 |
农作物 | 16篇 |
水产渔业 | 36篇 |
畜牧兽医 | 50篇 |
园艺 | 3篇 |
植物保护 | 20篇 |
出版年
2023年 | 1篇 |
2022年 | 7篇 |
2021年 | 11篇 |
2020年 | 6篇 |
2019年 | 5篇 |
2018年 | 12篇 |
2017年 | 14篇 |
2016年 | 10篇 |
2015年 | 2篇 |
2014年 | 6篇 |
2013年 | 15篇 |
2012年 | 12篇 |
2011年 | 10篇 |
2010年 | 12篇 |
2009年 | 8篇 |
2008年 | 16篇 |
2007年 | 10篇 |
2006年 | 5篇 |
2005年 | 9篇 |
2004年 | 5篇 |
2003年 | 2篇 |
2002年 | 3篇 |
2001年 | 5篇 |
1999年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 2篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1945年 | 1篇 |
排序方式: 共有216条查询结果,搜索用时 0 毫秒
1.
The common pistachio psylla, Agonoscena pistaciae, is a serious global pest menacing pistachio orchards. Considering the dangers of using excessive chemical pesticides, it seems that using natural insecticides such as diatomaceous earth is a suitable way to lower the residual amount of highly hazardous pesticides. In this study, the effects of diatomaceous earth with different additives, including dipotassium hydrogen phosphate, polyurethane glue as a wood adhesive, and potassium silicate, were investigated in several concentrations over two years in orchard conditions. Although all treatments showed significant effects, the most effective treatments were (diatomaceous earth+dipotassium hydrogen phosphate) and (diatomaceous earth+polyurethane glue). Therefore, the use of diatomaceous earth combined with the additive materials mentioned can potentially be a safe method for the integrated management of the common pistachio psylla. 相似文献
2.
The problem of real-time irrigation scheduling under limited water supply is considered. The goal is to develop an irrigation operation policy which maximizes crop yields and is responsive to current season changes in weather and other variables. Because irrigation decisions are sequential and dependent on crop and soil water status, and also because crop yields can only be known at the end of the season, the decisions are arrived at by a two-stage process. In the first or the design stage, irrigations are planned for the entire season at weekly intervals using historical data and an optimal irrigation scheduling model. In the second stage, the decisions for the subsequent weeks are revised each week after updating the status of the system with real time data up to that week and solving the irrigation optimization model once again for the new conditions. Thus, each week an irrigation decision is made, the entire planning horizon is kept in view. The procedure is illustrated by application to a case study. 相似文献
3.
利用随机区组试验评估了孟加拉国吉大港大学苗圃内的银合欢落叶对森林作物种白格、黄金檀和农田作物种长豇豆、鹰嘴豆和木豆的他感作用。结果表明,凋落叶诱导抑制作物的萌发和生长,该抑制作用依赖于萃取物浓度、凋落物及受体物种类型。萃取物浓度越高则他感作用越强。受体植物的生长响应随应用的凋落叶而变化。低浓度(10g·m-2)凋落叶对农田作物嫩芽生长有促进作用,而其他浓度的凋落叶则呈现明显的抑制作用,施用的凋落叶浓度越大抑制作用也越大。但是不同处理所表现出的抑制趋势并不均一,根系生长受到的影响大于嫩芽。图3表4参34。 相似文献
4.
Hadia OM Khair Ibrahim A Adam Shakir B Bushara Kamal H Eltom Nasreen O Musa Imadeldin E Aradaib 《Irish veterinary journal》2014,67(1):4
Background
Bluetongue virus (BTV) is an insect-transmitted virus, which causes bluetongue disease (BT) in sheep and a fatal hemorrhagic infection in North American white-tailed deer. However, in cattle the disease is typically asymptomatic and no overt clinical signs of disease appear to be associated with BTV infection. Serological evidence and isolation of different BTV serotypes have been reported in Sudan, however, no information is currently available in regard to previous exposure of Sudanese livestock to BTV infection in East Darfur State, Sudan.Aims
To determine the prevalence of BTV antibodies and to identify the potential risk factors associated with BTV infection among cattle in East Darfur State, Sudan.Methods
A total of 224 blood samples were collected randomly from five localities in East Darfur State, Sudan. The serum samples were screened for detection of BTV-specific immunoglobulin G (IgG) antibodies using a competitive enzyme-linked immunosorbent assay (c-ELISA).Results
Serological evidence of BTV infection was observed in 150 out of 224 animals accounting for a 67% prevalence rate among cattle in East Darfur State. Older cattle (>2 years of age) were six times more likely to be infected with BTV (OR = 6.62, CI = 2.87-15.26, p-value = 0.01). Regarding animal source (contact with other herds) as a risk factor, it was shown that cattle purchased from market or introduced from other herds were 3 times at higher risk of being infected with BTV (OR = 3.87, CI = 1.07-13.87, p value = 0.03). Exposure of cattle to the insect vector increased the risk of contracting BTV infection by six times compared to non-exposed cattle (OR = 6.44, CI = 1.53-27.08, p value = 0.01).Conclusion
The present study indicated that age, animal source and the intensity of the insect vector are influential risk factors for BTV infection in cattle in the Darfur region. Surveillance for BTV infection should be extended to include other susceptible ruminants and to study the distribution of the insect vectors to better predict and respond to a possible BTV outbreak in the State of East Darfur, Sudan. 相似文献5.
6.
7.
Chickpea wilt caused by Fusarium oxysporum f. sp. ciceris is one of the major yield limiting factors in chickpea. The disease causes 10–90% yield losses annually in chickpea. Eight
physiological races of the pathogen (0, 1A, 1B/C, 2, 3, 4, 5 and 6) are reported so far whereas additional races are suspected
from India. The distribution pattern of these races in different parts of the world indicates regional specificity for their
occurrence leading to the perception that F. oxysporum f. sp. ciceris evolved independently in different regions. Pathogen isolates also exhibit differences in disease symptoms. Races 0 and 1B/C
cause yellowing syndrome whereas 1A, 2, 3, 4, 5 and 6 lead to wilting syndrome. Genetics of resistance to two races (1B/C
and 6) is yet to be determined, however, for other races resistance is governed either by monogenes or oligogenes. The individual
genes of oligogenic resistance mechanism delay onset of disease symptoms, a phenomenon called as late wilting. Slow wilting,
i.e., slow development of disease after onset of disease symptoms also occurs in reaction to pathogen; however, its genetics
are not known. Mapping of wilt resistance genes in chickpea is difficult because of minimal polymorphism; however, it has
been facilitated to great extent by the development of sequence tagged microsatellite site (STMS) markers that have revealed
significant interspecific and intraspecific polymorphism. Markers linked to six genes governing resistance to six races (0,
1A, 2, 3, 4 and 5) of the pathogen have been identified and their position on chickpea linkage maps elucidated. These genes
lie in two separate clusters on two different chickpea linkage groups. While the gene for resistance to race 0 is situated
on LG 5 of Winter et al. (Theoretical and Applied Genetics 101:1155–1163, 2000) those governing resistance to races 1A, 2, 3, 4 and 5 spanned a region of 8.2 cM on LG 2. The cluster of five resistance
genes was further subdivided into two sub clusters of 2.8 cM and 2.0 cM, respectively. Map-based cloning can be used to isolate
the six genes mapped so far; however, the region containing these genes needs additional markers to facilitate their isolation.
Cloning of wilt resistance genes is desirable to study their evolution, mechanisms of resistance and their exploitation in
wilt resistance breeding and wilt management. 相似文献
8.
Mounting a protective immune response is critically dependent on the orchestrated movement of cells within lymphoid organs. We report here the visualization, using major histocompatability complex class I tetramers, of the CD8-positive (CD8) T cell response in the spleens of mice to Listeria monocytogenes infection. A multistage pathway was revealed that included initial activation at the borders of the B and T cell zones followed by cluster formation with antigenpresenting cells leading to CD8 T cell exit to the red pulp via bridging channels. Strikingly, many memory CD8 T cells localized to the B cell zones and, when challenged, underwent rapid migration to the T cell zones where proliferation occurred, followed by egress via bridging channels in parallel with the primary response. Thus, the ability to track endogenous immune responses has uncovered both distinct and overlapping mechanisms and anatomical locations driving primary and secondary immune responses. 相似文献
9.
10.
Many expert-designed agroforestry projects enunciated in 1970s around the world, particularly in the developing countries,
had uneven success due to inadequate adoption or abandonment after adoption. There are many empirical studies on factors affecting
on-farm tree cultivation mainly where expert-designed agroforestry programmes were introduced but lacking in case of traditional
agroforestry. Moreover, the concern to identify key factors influencing on-farm tree growing is gaining importance. The present
study identifies key factors in on-farm tree growing based on investigation of traditional agroforestry using logistic regression
approach. The study is based on household survey of 401 households located in Indian Western Himalaya. The factors affecting
on-farm tree growing were grouped into: biophysical (included land use and infrastructural aspects) and social. Models predicting
on-farm tree growing for each category were developed and key factors affecting on-farm tree growing in the respective category
were identified. A composite model was also developed by combining biophysical and social factors. In the present study, farm
size, agroclimatic zone, soil fertility, mobility and importance of tree for future generations respectively were the key
factors which influenced tree growing. In contrast to many previous studies which considered either biophysical or social
factors, the composite model in the present study reveals that both biophysical and social factors are simultaneously important
in motivating the farmers to grow trees on their farms in traditional agroforestry. Moreover, the present study open vistas
for using farmers’ experience and knowledge of adoption of agroforestry to stimulate on-farm tree growing. The wider implication
of the study is that biophysical as well as social variables should be considered together in designing suitable agroforestry
systems in various parts of the world. 相似文献