全文获取类型
收费全文 | 537篇 |
免费 | 24篇 |
专业分类
林业 | 47篇 |
农学 | 51篇 |
基础科学 | 2篇 |
96篇 | |
综合类 | 29篇 |
农作物 | 65篇 |
水产渔业 | 81篇 |
畜牧兽医 | 146篇 |
园艺 | 14篇 |
植物保护 | 30篇 |
出版年
2024年 | 3篇 |
2023年 | 8篇 |
2022年 | 6篇 |
2021年 | 8篇 |
2020年 | 16篇 |
2019年 | 18篇 |
2018年 | 22篇 |
2017年 | 25篇 |
2016年 | 28篇 |
2015年 | 14篇 |
2014年 | 28篇 |
2013年 | 60篇 |
2012年 | 37篇 |
2011年 | 31篇 |
2010年 | 34篇 |
2009年 | 23篇 |
2008年 | 35篇 |
2007年 | 19篇 |
2006年 | 13篇 |
2005年 | 13篇 |
2004年 | 10篇 |
2003年 | 3篇 |
2002年 | 7篇 |
2001年 | 14篇 |
2000年 | 6篇 |
1999年 | 7篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1994年 | 3篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1972年 | 1篇 |
1971年 | 4篇 |
1970年 | 5篇 |
1968年 | 7篇 |
1967年 | 4篇 |
1966年 | 6篇 |
1965年 | 2篇 |
1964年 | 1篇 |
1959年 | 1篇 |
1865年 | 1篇 |
排序方式: 共有561条查询结果,搜索用时 0 毫秒
101.
The effect of inoculum concentrations, temperature, relative humidity (RH), incubation period and leaf age on sporulation of Pestalotiopsis disseminata and the development of grey blight disease on som (Persea bombycina Kost.) were studied in controlled environmental conditions. These factors had a significant role on spore germination and germ tube development of P. disseminata, the causal organism of the disease. The optimum inoculum concentration of the pathogen were found to be 1 × 107 spores ml−1 for maximum infection percentage. A nonlinear relationship was found between temperature and germination percentage of spores at a given relative humidity (RH). However, 25 °C (±2) temperature and 70% RH were the optimum parameters for better spore germination of the pathogen. Young leaves (leaf no. 1–4 from the top) were more susceptible for development of the diseases in a controlled environment than the older leaves. The germination of spores started at 8 h of incubation and gradually increased up to 20 h (maximum). The disease severity was favoured in the optimum range of temperature (25 ± 2 °C) and RH (70%) which had a combined effect. These epidemiological parameters could help in the management practices of the disease. 相似文献
102.
103.
Systematics and taxonomic delimitation of vegetable,grain and weed amaranths: a morphological and biochemical approach 总被引:1,自引:0,他引:1
Saubhik Das 《Genetic Resources and Crop Evolution》2012,59(2):289-303
Amaranthus is a cosmopolitan genus comprising large number of species with many morphotypes cultivars/accessions having diversified
morphological features. The species, morphotypes within Amaranthus are very closely related requiring microclassification even revision in present taxonomic status. Most of the works have
been done employing grain Amaranthus and their putative ancestors applying morphological and molecular data. In present study along with morphological features,
phenolic compounds (secondary metabolites), isozyme profile of acid phosphatase were applied to get comprehensive reflection
of interrelationship and relative closeness among the species, morphotypes/accessions of few vegetable, grain and weed Amaranthus. Both the vegetable and grain Amaranthus are supposed to have originated from respective weed progenitor through occasional outcrossing and gradual domestication.
The study strongly vouched the previous interpretations regarding interrelationship of grain Amaranthus and their derivation from their putative progenitor also showed clear separate clustering of vegetable and grain Amaranthus with their close relatives. A sharp congruence in cluster pattern was achieved between morphological dendrogram and cumulative
dendrogram computed on morphological and biochemical parameters, which is a rare event in systematics. 相似文献
104.
Jaya Das Samira H. Daroub Jehangir H. Bhadha Timothy A. Lang Orlando Diaz Willie Harris 《Journal of Soils and Sediments》2012,12(6):952-965
Purpose
Excess nutrients such as phosphorus (P) transported from the Everglades Agricultural Area (EAA) in South Florida, USA, to downstream water bodies have been identified as contributing to trophic imbalances within the Florida Everglades. Decades of farming drainage from the EAA has led to accumulation of sediments in regional canals which may be transported to downstream ecosystems and act as potential internal source of P.Materials and methods
Intact sediment cores were collected from three main conveyance and three farm canals within the EAA. Physicochemical assessment, mineralogy, P speciation, and storage were determined for surface and subsurface layers.Results and discussion
The main conveyance canal sediments had higher total P (TP) concentrations (1,280?±?360?mg?kg-1) than the farm canals (960?±?540?mg?kg-1), while farm canal sediments showed higher organic matter content (28?C53?%) compared to the main canal (24?C27?%) sediments. The minerals found in main conveyance canal sediments were similar to those found in Lake Okeechobee. The labile KCl?CP fraction comprised <2?% of TP from all canal sediments, while NaOH?CPi (i?=?inorganic) fraction consisted of 1?C14?% of TP. The majority of P in the canal sediments was contained in the HCl?CP fraction (Ca?CP and Mg?CP), comprising >50?% of TP in the main and farm canal sediments. An estimated 73 metric tons (mt) of P was stored in the 0?C10-cm layer of the three main conveyance canals within the EAA boundary of which 57-mt P is reactive and potentially available for release at different time scales.Conclusions
The EAA canal sediments are highly organic with low bulk density and susceptible of being transported to downstream ecosystems. Many factors can impact the potential release of the reactive stored P, including redox potential of sediments as well as the overlying water column P concentration. Further investigation of potential P release from these sediments is warranted. 相似文献105.
106.
Hemagglutinating activity was identified in the roots and vegetative tissues of Bengal gram using rabbit erythrocytes. The activity in the roots appears to be similar to that of the seeds in respect to their sugar inhibition property. Seed and root extracts were found to have fetuin inhibitory agglutinating activity, whereas cotyledons showed different sugar specificity. However, 7-day cotyledons and roots from 3 and 7-day plants were also found to have galactose and N-acetyl-D-galactosamine inhibitory activity. Protein profile in different tissues during their developmental stages was analyzed by SDS-PAGE. A major band at 66 kDa was common to all tissues at different stages of their development except 3-day cotyledons where 2 major bands at 22 kDa and 74 kDa were observed. Two prominent bands at 74 kDa and 86 kDa were found along with 60 kDa protein in 3-day old roots whereas a major band at 33 kDa was found in 15-day old roots. Total protein content and specific activity of hemagglutinin were measured. Increase in specific activity with lower protein content was observed in cotyledons of 15-day old plant. Specific activity was eight times higher in the roots and four times more in leaf tissues of 7-day old plants in comparison to 15-day old plants. Stems also showed a significant increase of specific activity (p = 0.013) in 7-day old plants without any significant alteration in the protein content. 相似文献
107.
Micha?l C Fontaine Krystal A Tolley Ursula Siebert Sylvie Gobert Gilles Lepoint Jean-Marie Bouquegneau Krishna Das 《BMC ecology》2007,7(1):1
Background
We investigated the feeding ecology and habitat use of 32 harbour porpoises by-caught in 4 localities along the Scandinavian coast from the North Sea to the Barents Sea using time-integrative markers: stable isotopes (δ13C, δ15N) and trace elements (Zn, Cu, Fe, Se, total Hg and Cd), in relation to habitat characteristics (bathymetry) and geographic position (latitude). 相似文献108.
Background
Harbour porpoises Phocoena phocoena from the southern North Sea are known to display high levels of Zn and Hg in their tissues linked to their nutritional status (emaciation). The question arises regarding a potential role of metallothioneins (MTs) with regard to these high metal levels. In the present study, metallothionein detection and associated Zn, Cd, Cu and Hg concentrations were investigated in the liver and kidney of 14 harbour porpoises collected along the Belgian coast. 相似文献109.
Brojeswari Das A. Das V. K. Kothari R. Fanguiero M. de Araújo 《Fibers and Polymers》2008,9(2):225-231
The current work incorporates an experimental study on the effect of fiber cross sectional shape and fibre diameter on moisture
transmission properties of the fabric. Water vapour transmission of the fabrics was measured using the PERMETEST. In plane
liquid flow through the fabric was measured using a gravimetric in-plane wicking tester and vertical movement of liquid along
the fibres against gravity was also observed using a vertical wicking tester. With the change in shape factor and fibre diameter,
it is seen that with increase in fibre specific surface area wicking rate through fabric increases, whereas water vapour permeability
of the fabric reduces. 相似文献
110.
Root biomass and distribution of five agroforestry tree species 总被引:1,自引:0,他引:1
Knowledge of the quantitative assessment and structural development of root systems is essential to improve and optimize productivity
of agroforestry systems. Studies on root biomass recovery by sieves of different mesh sizes (2.0, 1.0, 0.5 and 0.25 mm) and
root distribution for four-year-old individuals of five agroforestry tree species viz.; Acacia auriculiformis A. Cunn. ex Benth, Azadirachta indica A. Juss, Bauhinia variegata L., Bombax ceiba L. and Wendlandia exserta Roxb. were conducted at the research farm of Rajendra Agricultural University, Pusa, Bihar, India. The results indicated
that the 0.5 mm sieve was adequate for recovery of the majority of roots. All the tree species exhibited a large variation
in root depth and horizontal root spread four years after planting. The maximum root depth was recorded in W. exserta (2.10 m) and minimum in B. variegata (1.00 m). Horizontal root spread was 2.05 m in B. ceiba and 8.05 m in A. auriculiformis. Root spread exceeded crown cover for all species. The primary roots were more horizontal than the secondary roots. The length
and diameter of the main root were highest in A. indica (108.3 cm) and B. ceiba (23.2 cm), respectively. Highest length and diameter of lateral roots were recorded in B.
variegata (201.6 cm) and A. indica (1.8 cm), respectively. Total root biomass among different species accounted for 18.2–37.9% of the total tree biomass. Results
of this study infer that although all the species have potential to conserve moisture and improve fertility status of the
soil, A. auriculiformis is the most effective for promoting soil fertility. The deep rooted W. exserta and A. auriculiformis will be preferred for cultivation under agroforestry systems and could reduce competition for nutrients and moisture with
crops by pumping from deeper layers of soil. 相似文献