全文获取类型
收费全文 | 2405篇 |
免费 | 200篇 |
专业分类
林业 | 202篇 |
农学 | 110篇 |
基础科学 | 17篇 |
526篇 | |
综合类 | 71篇 |
农作物 | 170篇 |
水产渔业 | 319篇 |
畜牧兽医 | 935篇 |
园艺 | 50篇 |
植物保护 | 205篇 |
出版年
2023年 | 35篇 |
2022年 | 66篇 |
2021年 | 139篇 |
2020年 | 143篇 |
2019年 | 162篇 |
2018年 | 105篇 |
2017年 | 149篇 |
2016年 | 132篇 |
2015年 | 85篇 |
2014年 | 116篇 |
2013年 | 160篇 |
2012年 | 180篇 |
2011年 | 223篇 |
2010年 | 112篇 |
2009年 | 104篇 |
2008年 | 112篇 |
2007年 | 111篇 |
2006年 | 76篇 |
2005年 | 75篇 |
2004年 | 65篇 |
2003年 | 64篇 |
2002年 | 50篇 |
2001年 | 21篇 |
2000年 | 16篇 |
1999年 | 10篇 |
1998年 | 9篇 |
1997年 | 13篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 7篇 |
1989年 | 4篇 |
1987年 | 6篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 3篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1968年 | 1篇 |
1966年 | 2篇 |
1965年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有2605条查询结果,搜索用时 15 毫秒
51.
Coagulase gene typing of Staphylococcus aureus isolated from cows with mastitis in southeastern Brazil 下载免费PDF全文
Elizabete Rodrigues da Silva Nivaldo da Silva 《Canadian journal of veterinary research》2005,69(4):260-264
A typing procedure based on polymorphism of the coagulase gene (coa) was used to discriminate Staphylococcus aureus isolated from Minas Gerais dairy cows with mastitis. Amplification of the gene from the 64 S. aureus isolates produced 27 different polymerase chain reaction (PCR) products; 60 isolates showed only 1 amplicon, and 4 showed 2 amplicons. The isolates were grouped into 49 types by analyzing the restriction fragment length polymorphism (RFLP) of the coa gene; the 10 most common types accounted for 39% of the isolates. The results demonstrate that many variants of the coa gene are present in the studied region, although only a few predominate. 相似文献
52.
W. G. D. Fernando A. K. Watson T. C. Paulitz 《European journal of plant pathology / European Foundation for Plant Pathology》1996,102(1):1-7
Colletotrichum coccodes is currently being investigated as a mycoherbicide against the weed velvetleaf (Abutilon theophrasti). Two isolates ofPseudomonas spp. (Ps2 and Ps5) reduced the percentage of germ tubes and increased appressorial formation ofC. coccodes on detached leaves of velvetleaf. A study was conducted to see whether this effect could be attributed to competition for nutrients or iron betweenC. coccodes andPseudomonas spp. Ps2 and Ps5 had no effect on early spore germination, but reduced the percentage of germ tubes at 24 and 30 h, compared to the nontreated control. This reduction was diminished by the addition of nutrients but not Fe3+. Ps2 and Ps5 stimulated the formation of dark-coloured appressoria without germ tubes (AWGT), but this stimulation was diminished by the addition of nutrients or Fe3+. Germ tube branching at 30 h was also inhibited by the bacteria, but was not diminished by the addition of nutrients or iron. EDTA stimulated conidial germination at 10 h, which was reduced by the addition of Fe3+. However, EDTA did not stimulate the formation of appressoria (AWGT). These results suggest that the reduction in the percentage of germ tubes and the increase in the percentage of appressoria induced by the bacteria may be due to the competition for carbon or nitrogen. Iron competition may also be involved in the stimulation of appressorial formation, but not in the reduction in germ tube percentage and branching. Phylloplane bacteria may compete for carbon, nitrogen and iron, limiting the saprophytic phase of the pathogen on the phylloplane and accelerating the development of the parasitic phase. This may enhance the field efficacy ofC. coccodes as a biocontrol agent against velvetleaf. 相似文献
53.
ABSTRACT A generalized two-dimensional Gaussian model is proposed to describe disease foci of head blight of wheat in plots (100 to 2,500 m(2)) originating from small areas (1 to 16 m(2)) inoculated with Gibberella zeae-colonized corn kernels. These anisotropic, asymmetrical foci arose from ascospores produced in perithecia. The model is Z = exp[-(AX(2) + BY(2) + CXY + DX + EY + F)], in which Z = the incidence of seed or spikelet infection at point (X,Y) located in the plot, exp = the exponential function, X = the abscissa or spatial coordinate of the point along a given axis (approximately parallel to the average wind vector during the period of spore release in these experiments), Y = the ordinate or spatial coordinate of the point along the axis perpendicular to the X axis (approximately perpendicular to the wind direction in these experiments), A and B = the quadratic coefficients of the second-order polynomial AX(2) + BY(2) + CXY + DX + EY + F, C = the bilinear coefficient, D and E = the linear coefficients, and exp(-F) = the incidence of seed or spikelet infection at the focus peak in which X = 0 and Y = 0. The generalized two-dimensional Gaussian model was tested on data from a circular or isotropic focus, an elliptical or anisotropic focus with two axes of symmetry, and two anisotropic foci with one and zero axis of symmetry. Its goodness-of-fit (r(2) and adjusted r(2)) was compared with the inverse power, modified inverse power, exponential, and classical Gaussian models. Submodels using only the linear terms, only the quadratic terms, or combinations selected from stepwise regression procedures using various probabilities to enter and to stay and a procedure maximizing the adjusted r (2) were also considered. Spatial analysis of the residuals was performed using Geary's c coefficient at the first distance class. For the circular and elliptical foci, our model provided a fit similar to the modified inverse power and exponential models. However, for anisotropic foci with one or zero axis of symmetry arising from ascospores influenced by wind direction, the generalized two-dimensional Gaussian model provided a better fit. For these anisotropic foci, the linear term X but not the quadratic term X(2) was generally retained in the model, indicating an exponential gradient in the direction parallel to the wind. In all models, the quadratic term Y(2) was retained, along with Y in some cases, indicating that the gradient in the direction roughly perpendicular to the wind was Gaussian or Gaussian-exponential in shape. The bilinear term XY provided an indication of the orientation of the focus in relation to the axes of the sampling grid. This model has the versatility and parameters (quadratic, bilinear, and linear) to better describe the anisotropy of foci from wind-dispersed spores. 相似文献
54.
55.
Roque DD Andreo JC De Oliveira JA Roque JS Buchaim RL Rodrigues AC 《Anatomia, histologia, embryologia》2003,32(4):207-211
Considering monkeys are animals closely related to the human, and semitendinosus muscle has been used in many postural research experiments, we have decided to study its histochemical characteristics. Samples were removed from the proximal, middle and distal regions of the semitendinosus muscles of five adult male tufted capuchin monkeys and observed for reaction with m-ATPase (with alkaline and acid pre-incubation), nicotinamide adenine dinucleotide tetrazolium reductase, and haematoxylin and eosin. The muscle fibres were classified as fast glycolytic (FG), fast oxidative glycolytic (FOG) and slow oxidative (SO) and quantified in terms of frequency and area. The three regions of the semitendinosus muscle showed no significant differences in frequency or area of the respective fibre types, and therefore the muscle can be considered histoenzymologically homogeneous. FG fibres presented higher frequencies and larger areas. The sum of FOG and SO fibres was 57.5%, suggesting that the semitendinosus muscle of the tufted capuchin monkey is adapted to an action involved in posture maintenance and in long arboreal dislocation. The present data agrees with the notion of differentiated quadrupedalism in some primates, which support a lower percentage of their weight on the fore limbs. 相似文献
56.
This paper reviews the epidemiology of bovine, swine, ovine, caprine, and canine brucellosis in Brazil. The zoonotic aspects of Brucella infection in Brazil is also discussed. Emphasis is given to the new program for the control of brucellosis in cattle and buffaloes that is likely to provide important insights into the prospects and strategies for controlling brucellosis in developing countries. 相似文献
57.
Effects of deficit irrigation strategies on cluster microclimate for improving fruit composition of Moscatel field-grown grapevines 总被引:1,自引:0,他引:1
Tiago Pedreira dos Santos Carlos M. Lopes M. Lucília Rodrigues Claudia R. de Souza Jorge M. Ricardo-da-Silva João P. Maroco João S. Pereira M. Manuela Chaves 《Scientia Horticulturae》2007
The grapevine plays a very important role in the economic, social and cultural sectors of many regions; however vineyards are often grown in regions under stressful conditions and thus they are vulnerable to climate change. The objective of this research was to investigate the effect of partial root-zone drying (PRD) irrigation on vine water relations, vegetative growth, plant microclimate, berry composition and yield components, compared to conventional deficit irrigation (DI, 50% ETc), full irrigation (FI, 100% of ETc) and non-irrigated vines (NI). The study was undertaken in mature ‘Moscatel’ grapevines (Vitis vinifera L.) grown in Pegões, South of Portugal. Compared to the other irrigated treatments, PRD vines showed a better microclimate at the cluster zone with higher incident photosynthetic photon flux density (PPFD). Within the more open canopies of NI and PRD treatments, berry temperatures were higher than those of denser ones (DI and FI). Compared to the conventional irrigation technique the better microclimate observed in PRD vines was a consequence of a reduction in vine growth, where lower values of leaf layer number, leaf area, canopy wideness, water shoots and shoot weight were observed. In PRD vines we observed a tendency to a development of a deeper root system, while DI and FI showed a more homogeneous root distribution throughout the different soil layers. PRD showed an improvement in berry quality with higher values of flavour precursors, and total phenols concentration without any significant yield reduction compared to DI and FI. 相似文献
58.
Gabriela Claudia Cangahuala-Inocente Lírio Luiz Dal Vesco Douglas Steinmacher Antonio Carlos Torres Miguel Pedro Guerra 《Scientia Horticulturae》2007
Pineapple guava (Acca sellowiana) syn. Feijoa sellowiana, a Brazilian indigenous Myrtaceae is under domestication in South Brazil. Previous works showed that this species is responsive to somatic embryogenesis and recalcitrant to conventional methods of clonal propagation. In the present work it was evaluated the role of components of culture medium in the induction and development of somatic embryos. The technology of synthetic seeds was also evaluated. Zygotic embryos were inoculated in LPm medium supplemented with 8 mM glutamic acid and 8 mM l-glutamine, 2,4-dichlophenoxiacetic acid (20 μM) and myo-inositol. For conversion of somatic embryos and synthetic seeds it was tested the effect of 6-benzylaminopurine and gibberellic acid combined or not with activated charcoal. The highest values for embryogenetic induction (100%) and number of somatic embryos/explant (113) were observed in the LPm medium supplemented with Glu (8 mM), and 2,4-D. The culture medium supplemented with BA (0.5 μM) and GA3 (1 μM) and activated charcoal (1.5 g L−1) enhanced the conversion of somatic embryos to plantlets. Pre-germinated somatic embryos encapsulated in sodium alginate with BA (0.5 μM) and GA3 (1 μM) developed radicles. The use of synthetic seed was a requisite for the survival of plantlets. 相似文献
59.
Silvio Aparecido Lopes Guilherme Fernando Frare Pedro Takao Yamamoto Antonio Juliano Ayres José Carlos Barbosa 《European journal of plant pathology / European Foundation for Plant Pathology》2007,119(4):463-468
The huanglongbing (HLB) disease of citrus trees, caused by Candidatus Liberibacter asiaticus and Ca. Liberibacter americanus, was first reported in Brazil in March, 2004. The presence of the disease has caused serious concerns
among growers. Pruning experiments were conducted to determine if removal of symptomatic branches or the entire canopy (decapitation)
would eliminate infected tissues and save HLB-affected trees. Pruning was done in five blocks on a total of 592 3- to 16 year-old
‘Valência’, ‘Hamlin’ or ‘Pêra’ sweet orange trees showing no symptoms or with two levels of symptom severity. Ten decapitated
trees per block were caged and all trees were treated with insecticides to control the psyllid vector, Diaphorina citri. Mottled leaves reappeared on most symptomatic (69.2%) as well on some asymptomatic (7.6%) pruned trees, regardless of age,
variety, and pruning procedure. Presence of the pathogen (Ca. Liberibacter americanus) in all symptomatic trees was confirmed by PCR. In general, the greater the symptom severity before
pruning the lower the percentage of trees that remained asymptomatic after pruning. 相似文献