全文获取类型
收费全文 | 1587篇 |
免费 | 115篇 |
国内免费 | 3篇 |
专业分类
林业 | 120篇 |
农学 | 46篇 |
基础科学 | 7篇 |
335篇 | |
综合类 | 184篇 |
农作物 | 46篇 |
水产渔业 | 236篇 |
畜牧兽医 | 531篇 |
园艺 | 62篇 |
植物保护 | 138篇 |
出版年
2024年 | 6篇 |
2023年 | 11篇 |
2022年 | 13篇 |
2021年 | 30篇 |
2020年 | 37篇 |
2019年 | 57篇 |
2018年 | 53篇 |
2017年 | 48篇 |
2016年 | 63篇 |
2015年 | 59篇 |
2014年 | 48篇 |
2013年 | 90篇 |
2012年 | 105篇 |
2011年 | 110篇 |
2010年 | 96篇 |
2009年 | 73篇 |
2008年 | 96篇 |
2007年 | 86篇 |
2006年 | 96篇 |
2005年 | 80篇 |
2004年 | 75篇 |
2003年 | 79篇 |
2002年 | 56篇 |
2001年 | 25篇 |
2000年 | 17篇 |
1999年 | 16篇 |
1998年 | 11篇 |
1997年 | 10篇 |
1996年 | 5篇 |
1995年 | 8篇 |
1994年 | 8篇 |
1993年 | 10篇 |
1992年 | 6篇 |
1991年 | 13篇 |
1990年 | 12篇 |
1989年 | 11篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1985年 | 6篇 |
1984年 | 8篇 |
1983年 | 9篇 |
1982年 | 5篇 |
1981年 | 9篇 |
1979年 | 6篇 |
1977年 | 2篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1968年 | 2篇 |
排序方式: 共有1705条查询结果,搜索用时 462 毫秒
111.
Mbithi-Mwikya S Van Camp J Mamiro PR Ooghe W Kolsteren P Huyghebaert A 《Journal of agricultural and food chemistry》2002,50(10):3030-3036
Finger millet (Eleusine coracana), kidney beans (Phaseolus vulgaris), peanuts (Arachis hypogoea), and mango (Mangifera indica) were processed separately and then combined, on the basis of their amino acid scores and energy content, into a complementary food for children of weaning age. The finger millet and kidney beans were processed by germination, autoclaving, and lactic acid fermentation. A mixture containing, on a dry matter basis, 65.2, 19.1, 8.0, and 7.7% of the processed finger millet, kidney beans, peanuts, and mango, respectively, gave a composite protein with an in vitro protein digestibility of 90.2% and an amino acid chemical score of 0.84. This mixture had an energy density of 16.3 kJ.g(-1) of dry matter and a decreased antinutrient content and showed a measurable improvement in the in vitro extractability for calcium, iron, and zinc. A 33% (w/v) pap made from a mix of the processed ingredients had an energy density of 5.4 kJ.g(-1) of pap, which is sufficient to meet the energy requirements of well-nourished children of 6-24 months of age at three servings a day and at the FAO average breast-feeding frequency. 相似文献
112.
We present here an indicator of soil quality that evaluates soil ecosystem services through a set of 5 subindicators, and further combines them into a single general Indicator of Soil Quality (GISQ). We used information derived from 54 properties commonly used to describe the multifaceted aspects of soil quality. The design and calculation of the indicators were based on sequences of multivariate analyses. Subindicators evaluated the physical quality, chemical fertility, organic matter stocks, aggregation and morphology of the upper 5 cm of soil and the biodiversity of soil macrofauna. A GISQ combined the different subindicators providing a global assessment of soil quality.Research was conducted in two hillside regions of Colombia and Nicaragua, with similar types of land use and socio-economic context. However, soil and climatic conditions differed significantly. In Nicaragua, soil quality was assessed at 61 points regularly distributed 200 m apart on a regular grid across the landscape. In Colombia, 8 plots representing different types of land use were arbitrarily chosen in the landscape and intensively sampled. Indicators that were designed in the Nicaragua site were further applied to the Colombian site to test for their applicability.In Nicaragua, coffee plantations, fallows, pastures and forest had the highest values of GISQ (1.00; 0.80; 0.78 and 0.77, respectively) while maize crops and eroded soils (0.19 and 0.10) had the lowest values. Examination of subindicator values allowed the separate evaluation of different aspects of soil quality: subindicators of organic matter, aggregation and morphology and biodiversity of macrofauna had the maximum values in coffee plantations (0.89; 0.72 and 0.56, respectively on average) while eroded soils had the lowest values for these indicators (0.10; 0.31 and 0.33, respectively).Indicator formulae derived from information gained at the Nicaraguan sites were not applicable to the Colombian situation and site-specific constants were calculated.This indicator allows the evaluation of soil quality and facilitates the identification of problem areas through the individual values of each subindicator. It allows monitoring of change through time and can guide the implementation of soil restoration technologies. Although GISQ formulae computed on a set of data were only valid at a regional scale, the methodology used to create these indices can be applied everywhere. 相似文献
113.
Jér?me?MathieuEmail author Jean-Pierre?Rossi Michel?Grimaldi Philippe?Mora Patrick?Lavelle Corinne?Rouland 《Biology and Fertility of Soils》2004,40(5):300-305
The influence of three spatially hierarchical factors upon soil macrofauna biodiversity was studied in four pasture plots in eastern Amazonia. The first factor was the local depth of the soil. The second factor was the ground cover type on the soil samples (bare ground, grass tufts, dead trees lying on the ground). The third factor was the dimensions of the grass tufts sampled (size and shape). The effect of each factor upon the morphospecies richness and density of total soil macrofauna was analysed. Detailed results are given for earthworms, termites, ants, beetles and spiders. All factors significantly affected the morphospecies richness and/or density of the soil macrofauna. The type of ground cover had the strongest influence, affecting the total richness and density of the soil macrofauna and of almost all the groups represented. The soil depth affected only the density of the termites and the global morphospecies richness. Interactions between soil depth and ground cover type affected the total macrofauna morphospecies richness and the density of the earthworms. The dimensions of the grass tuft influenced the global morphospecies richness, the morphospecies richness of the ants and the density of the spiders. 相似文献
114.
Marfak A Trouillas P Allais DP Champavier Y Calliste CA Duroux JL 《Journal of agricultural and food chemistry》2003,51(5):1270-1277
Oxidative reaction between hydroxymethyl radical ((*)CH(2)OH) and kaempferol, in methanol and methanol/water mixtures, was studied by gamma-radiolysis using a (60)Co source. Radiolysis was performed with concentrations and doses ranging from 5 x 10(-)(5) M to 5 x 10(-)(3) M and from 0.5 kGy to 14 kGy, respectively. Kaempferol degradation was followed by HPLC. Results showed that (*)CH(2)OH reacts with kaempferol at the 3-OH group and produces two depsides (K1 and K2) and other products including K3. K1, K2, and K3 were identified by NMR, LC-MS, and HRMS. The kaempferol degradation pathway leading to the K1, K2, and K3 formation is proposed. It was observed that the more water concentration in the irradiation medium increases, the more K2 concentration increases. Comprehension of food preservation is not clear because many phenomena occurring during irradiation are not established. Radiolysis of kaempferol in water/methanol mixtures helps to elucidate the phenomenon and it is possible that during the treatment of nutriments by gamma-irradiation, a series of products such as depside K2 could be formed. Antioxidant properties of kaempferol radiolysis products were evaluated according to their capacity to decrease the EPR DPPH (1,1-diphenyl-2-picrylhydrazil) signal and to inhibit superoxide radicals formed by the enzyme reaction "xanthine + xanthine oxidase". 相似文献
115.
Epi-fluorescence microscopy facilitated observations of the colonization of hyphae and conidia of C. sativus and other plant pathogenic fungi in soil. Of six fluorochromes examined, acridine orange and europium chelate effectively differentiated cells of bacteria and actinomycetes from the melanized fungal structures. Under u.v. radiation, the colonizing organisms fluoresced intensively while the pigmented conidia appeared dark. Periodic observations of hyphal fragments and conidia of C. sativus incubated in nonsterile soil revealed rapid colonization of their surface primarily by bacteria. Whereas up to 80% of the hyphal fragments of C. sativus were lysed after 32 days' incubation in soil, the conidia remained intact. However, disorganization of protoplasts and disappearance of conidial septa were evident after the fourth week. After 2, 3 and 5 weeks incubation of the plant pathogens in soil, no significant difference was noticed between microbial colonization of conidia on 8.0 μm pore size “Nucle-pore” membranes and those placed directly on the soil surface. 相似文献
116.
117.
CENH3 is a centromere-specific histone H3 variant essential for kinetochore assembly. Despite its central role in centromere function, there has been no conclusive evidence supporting CENH3 as sufficient to determine centromere identity. To address this question, we artificially targeted Drosophila CENH3 (CENP-A/CID) as a CID-GFP-LacI fusion protein to stably integrated lac operator (lacO) arrays. This ectopic CID focus assembles a functional kinetochore and directs incorporation of CID molecules without the LacI-anchor, providing evidence for the self-propagation of the epigenetic mark. CID-GFP-LacI-bound extrachromosomal lacO plasmids can assemble kinetochore proteins and bind microtubules, resulting in their stable transmission for several cell generations even after eliminating CID-GFP-LacI. We conclude that CID is both necessary and sufficient to serve as an epigenetic centromere mark and nucleate heritable centromere function. 相似文献
118.
Colin PL 《Science (New York, N.Y.)》2003,300(5626):1657-9; author reply 1657-9
119.
Linder P 《Science (New York, N.Y.)》2004,304(5671):694-695
120.
Soft lithography is an alternative to silicon-based micromachining that uses replica molding of nontraditional elastomeric materials to fabricate stamps and microfluidic channels. We describe here an extension to the soft lithography paradigm, multilayer soft lithography, with which devices consisting of multiple layers may be fabricated from soft materials. We used this technique to build active microfluidic systems containing on-off valves, switching valves, and pumps entirely out of elastomer. The softness of these materials allows the device areas to be reduced by more than two orders of magnitude compared with silicon-based devices. The other advantages of soft lithography, such as rapid prototyping, ease of fabrication, and biocompatibility, are retained. 相似文献