全文获取类型
收费全文 | 3649篇 |
免费 | 378篇 |
专业分类
林业 | 287篇 |
农学 | 162篇 |
基础科学 | 24篇 |
648篇 | |
综合类 | 129篇 |
农作物 | 250篇 |
水产渔业 | 508篇 |
畜牧兽医 | 1560篇 |
园艺 | 92篇 |
植物保护 | 367篇 |
出版年
2024年 | 7篇 |
2023年 | 43篇 |
2022年 | 115篇 |
2021年 | 194篇 |
2020年 | 217篇 |
2019年 | 248篇 |
2018年 | 254篇 |
2017年 | 229篇 |
2016年 | 218篇 |
2015年 | 138篇 |
2014年 | 186篇 |
2013年 | 236篇 |
2012年 | 284篇 |
2011年 | 270篇 |
2010年 | 148篇 |
2009年 | 151篇 |
2008年 | 172篇 |
2007年 | 150篇 |
2006年 | 128篇 |
2005年 | 77篇 |
2004年 | 83篇 |
2003年 | 84篇 |
2002年 | 64篇 |
2001年 | 55篇 |
2000年 | 53篇 |
1999年 | 33篇 |
1998年 | 23篇 |
1997年 | 15篇 |
1996年 | 20篇 |
1995年 | 9篇 |
1994年 | 7篇 |
1992年 | 6篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 9篇 |
1988年 | 7篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1977年 | 3篇 |
1976年 | 6篇 |
1973年 | 6篇 |
1972年 | 3篇 |
1970年 | 3篇 |
1969年 | 4篇 |
排序方式: 共有4027条查询结果,搜索用时 15 毫秒
991.
992.
993.
Liliana de Oliveira Rocha Gabriela Martins Reis Raquel Braghini Estela Kobashigawa Jansen de Araújo Benedito Corrêa 《European journal of plant pathology / European Foundation for Plant Pathology》2012,132(3):353-366
Aflatoxins can cause great economic losses and serious risks to humans and animals health. The largest aflatoxin producers
belong to Aspergillus section Flavi and can occur naturally in food commodities. Studies showed that molecular tools as well as the type of sclerotia produced
by the strains could be helpful for identification of Aspergillus species and could be correlated with levels of toxin production. The purpose of this work was to characterize the genetic
diversity using AFLP technique, the type of sclerotia and the ability of aflatoxin production by isolated strains from corn
of different origins in Brazil, and to verify whether qPCR based on aflR and aflP genes is appropriate for estimating the level of aflatoxin production. All the 75 strains were classified as A. flavus and the AFLP technique showed a wide intraspecific variability within them. Regarding sclerotia production, 34% were classified
as S and 66% as L type. Among the aflatoxin-producers, 52.8% produced aflatoxin B1, while 47.2% aflatoxins B1 and B2. Statistical analysis showed no correlation between sclerotia production and aflatoxigenicty, and no correlation between
the phylogenetic clusters and aflatoxin production. Concerning the relative expression of aflR and aflP, Pearson’s correlation test demonstrated low positive correlation between the expression of the aflR and aflP genes and the production of AFB1 and AFB2, but showed high positive correlation between aflR and aflP expression. In contrast to the other reference strains, A. oryzae ATCC 7282 showed no amplification of aflR and aflP. The results highlight the need for detection of reliable and reproducible markers with a high positive correlation with aflatoxin
production. 相似文献
994.
André Costa da Silva Paulo Estev?o de Souza José Eduardo Brasil Pereira Pinto Bruno Marques da Silva Douglas Carvalho Amaral Eudes de Arruda Carvalho 《European journal of plant pathology / European Foundation for Plant Pathology》2012,134(4):865-871
The objective of the work was to evaluate the effect of essential oils as a preventive treatment to control Asian soybean rust. Initially the fungitoxic effect of the essential oils of Hyptis marrubioides, Aloysia gratissima and Cordia verbenacea was tested on the urediniospores of Phakopsora pachyrhizi, through in vitro tests. The in vivo test was set up in a greenhouse, using cultivar MGBR-46. The treatments consisted of the three oils at different concentrations, a fungicide based on pyraclostrobin + epoxyconazole and a control. To verify the potential of the essential oils in preventive treatment, inoculation was conducted at 0, 6, 12 and 24?h intervals, after application of the treatments. All treatments inhibited 100% of Phakopsora pachyrhizi germination. In the in vivo test, it was observed that all of the oils were efficient in controlling soybean rust, by preventive treatment, mainly at the higher concentrations. Efficiency of the oils was reduced with the increase of the interval between the application of the treatments and the onset of the pathogen. The essential oils, at the tested dosages, were not as efficient as the pyraclostrobin + epoxyconazole based fungicide. 相似文献
995.
Natália T. Marques Ângela A. Costa Débora Lopes Gonçalo Silva Gustavo Nolasco 《European journal of plant pathology / European Foundation for Plant Pathology》2012,133(1):229-235
The p20 protein encoded by the Citrus Tristeza Virus (CTV) was previously identified as a RNA silencing suppressor. In this study, we analyzed the p20’s suppressing activity
from five phylogenetic groups of CTV, using the co-infiltration assay of Green fluorescence protein (GFP) gene and the suppressor
gene in 16C line Nicotiana benthamiana plants. Green fluorescence, GFP mRNA relative levels and GFP specific siRNAS were compared showing in most cases, only slight
differences. Contrary to previous studies, the p20 suppressor was not able to impede neither short range nor systemic spreading
of RNA silencing. The suppressor from the phylogenetic group 4 revealed a much reduced activity when compared with the others.
At present we still don’t know whether this property is a characteristic of this group or an atypical feature due to a unique
point mutation. The differences in the symptom type and intensity originated by isolates belonging to the phylogenetic groups
assayed could not be related to differences to the p20 suppressor’s activity. 相似文献
996.
A. Loureiro M.R. NicoleV. Várzea P. MoncadaB. Bertrand M.C. Silva 《Physiological and Molecular Plant Pathology》2012,77(1):23-32
Histological and ultrastructural studies were undertaken to compare Colletotrichum kahawae growth and the sequence of responses it induced in resistant and susceptible coffee genotypes. Coffee resistance was characterized by a restricted fungal growth associated with hypersensitive-like cell death and early accumulation of phenolic compounds, such as flavonoids (cytoplasmic contents) and hydroxycinnamic acid derivatives (cell walls). This accumulation of phenols in the cell walls preceded their lignification and thickening. In the susceptible genotype, a late accumulation of hydroxycinnamic acid derivatives in a number of cell walls and the encasement of some intracellular hyphae were also observed, but these delayed host responses did not prevent fungal growth and sporulation. 相似文献
997.
The effect of the pathogen Phytophthora austrocedrae on tree physiology of Austrocedrus chilensis in Patagonia was studied in a 4‐week study. In the first week, stem‐inoculated saplings showed a significant decrease in photosynthesis (A) without alteration of stomatal conductance (gs) or stem‐specific hydraulic conductivity (Ks). From the second week on, progressive decreases in A, gs and Ks were observed, concomitantly with development of significant stem lesions. Water use efficiency (WUE) increased in the second week and declined progressively from the third week. Hyphae and resinous materials were observed in tracheids and rays below lesions. Necrosis of parenchyma ray cells and blockage of tracheids torus were observed. Healthy xylem showed no resinous materials or tracheid blockage, but abundant starch in rays, which was absent in altered xylem. The culture filtrate (CF) of the pathogen was shown to induce changes in extracellular pH and conductivity, and increased necrosis in tissues of leaves and stem challenged with CF in vitro. Similar results were obtained in leaf tissues of the inoculated saplings in vivo. CF injection into xylem of saplings induced a decline in A and disturbance of leaf tissue integrity, without altering gs, WUE or Ks. The decrease of A correlated with changes in tissue integrity. A possible mechanism of A. chilensis decline induced by P. austrocedrae is discussed. 相似文献
998.
Objectives : The aim of this study was to evaluate the sensitivity of conventional and Doppler ultrasound for differentiation of benign and malignant mammary tumours in female dogs. Methods : Mammary tumours were evaluated from 60 animals and divided into two distinct groups, group 1 (benign tumours) and group 2 (malignant tumours). The tumours were assessed by conventional ultrasound, Doppler ultrasound mode, histopathology and immunohistochemical detection of vascular endothelial growth factor. Results : Conventional ultrasound examination was found to be ineffective in separating tumours into the two experimental groups. Similarly, using colour‐flow Doppler ultrasound, no correlation was found between the presence of vascularisation and its characteristics between the two groups. Triplex Doppler ultrasound yielded average maximum velocities of 28·71 cm/s for malignant and 19·91 cm/s for benign tumours, which were significantly different (P=0·01). For vascular endothelial growth factor, an average score of 2·22 was found for group 2 and 1·66 for group 1 (P=0·03). Positive correlations were found between vascular endothelial growth factor and presence of vascularisation (P=0·04 and r=0·3658) and between vascular endothelial growth factor and maximum velocity (P=0·03 and r=0·3913). Clinical Significance : Doppler evaluation may be used to predict malignancy of mammary tumours in bitches. 相似文献
999.
1000.
Amparo C. Martínez-Ramírez Baltasar Escriche M. Dolores Real Francisco J. Silva Juan Ferr 《Pest management science》1995,43(2):115-120
Inheritance of resistance to the Bacillus thuringiensis Berl. CryIA(b) crystal protein was studied in Plutella xylostella L. (diamondback moth). A field population 50-fold more resistant to CryIA(b) than a control susceptible strain was used. Dose-mortality curves of the resistant population, the susceptible strain and the F1 from the two reciprocal crosses were compared. Resistance transmission to the F1 was dependent on the sex of the resistant progenitor. Sex ratio of the survivors to high doses of CryIA(b) in the F1 of the two reciprocal crosses did not corroborate the preliminary hypothesis of resistance being due to a recessive sex-linked allele. Since, in a previous work, the loss of CryIA(b) binding capacity of resistant insects had been demonstrated, binding to midgut tissue sections from F1 individuals was also analysed. The presence of binding in all of the F1 preparations showed that, at least, a recessive autosomal allele was responsible for the loss of binding capacity in the resistant population. 相似文献