全文获取类型
收费全文 | 415篇 |
免费 | 31篇 |
专业分类
林业 | 45篇 |
农学 | 19篇 |
基础科学 | 2篇 |
80篇 | |
综合类 | 15篇 |
农作物 | 28篇 |
水产渔业 | 55篇 |
畜牧兽医 | 138篇 |
园艺 | 30篇 |
植物保护 | 34篇 |
出版年
2023年 | 3篇 |
2022年 | 12篇 |
2021年 | 7篇 |
2020年 | 19篇 |
2019年 | 25篇 |
2018年 | 22篇 |
2017年 | 22篇 |
2016年 | 18篇 |
2015年 | 16篇 |
2014年 | 16篇 |
2013年 | 40篇 |
2012年 | 30篇 |
2011年 | 42篇 |
2010年 | 27篇 |
2009年 | 10篇 |
2008年 | 27篇 |
2007年 | 14篇 |
2006年 | 27篇 |
2005年 | 19篇 |
2004年 | 10篇 |
2003年 | 11篇 |
2002年 | 6篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1984年 | 2篇 |
1961年 | 1篇 |
排序方式: 共有446条查询结果,搜索用时 9 毫秒
111.
Fungal diseases and inappropriate sowing dates, the most important reducing factors in cumin fields of Iran, a case study in Khorasan provinces 总被引:1,自引:0,他引:1
112.
Carpel weight, grain length and stabilized grain water content are physiological drivers of grain weight determination of wheat 总被引:2,自引:0,他引:2
Ahmed K. Hasan Jaime HerreraCarolina Lizana Daniel F. Calderini 《Field Crops Research》2011,123(3):241-247
Among the yield components, grain weight is considered a conservative trait whose determination is still beyond our complete understanding. Crop physiology uses a whole approach to study this complex trait, which can provide helpful information to plant breeders and molecular biologists. This study emphasizes the understanding of pre- and post-anthesis determinants of final grain weight. A field experiment was carried out in two growing seasons evaluating two wheat cultivars contrasting in grain weight potential. Carpel weight at pollination, grain dimensions, grain water, dry matter and volume dynamics were assessed. Among grain dimensions, grain length was the trait, which explained final grain weight (r2 = 0.78; P < 0.01 and r2 = 0.94; P < 0.001 for the 1st and 2nd season, respectively) and it was the first trait to stabilize after anthesis. Water content of grains stabilized little later and also showed a strong association with final grain weight (r2 = 0.93; P < 0.01 and r2 = 0.98; P < 0.01 for the 1st and 2nd season respectively). Most importantly, carpel weight at pollination showed a positive and linear association with final grain weight (r2 = 0.79, P < 0.01 and r2 = 0.86 P < 0.01 for the 1st and 2nd season, respectively) irrespective of the cultivar and grain position. In addition, positive associations were also found between grain volume, water content, grain length, and carpel weight at pollination. Therefore, the associations between pre- and post-anthesis traits found in this study support the hypothesis that grain weight is determined before anthesis and fruit tissues (i.e., pericarp in cereals and sunflower) set an upper limit to grain weight. 相似文献
113.
The first total synthesis of acetylhomoagmatine, a natural product isolated form the methanolic extracts from the sponge Cliona celata, is performed in four steps in a very high yield. 相似文献
114.
Rodríguez-Meizoso I Jaime L Santoyo S Cifuentes A García-Blairsy Reina G Señoráns FJ Ibáñez E 《Journal of agricultural and food chemistry》2008,56(10):3517-3523
In the search for new functional ingredients with potential use in the food industry, extracts of unknown species of microalgae, such as Phormidium species have been studied. Three solvents of different polarities (i.e., hexane, ethanol, and water) have been used to obtain pressurized liquid extracts with different compositions. Moreover, extractions were performed at four different extraction temperatures (50, 100, 150, and 200 degrees C) with 20 min as extraction time. Antioxidant activity of the extracts has been measured by the TEAC assay. In general, hexane and ethanol extracts showed a higher antioxidant capacity that was mainly attributed to carotenoid compounds, as the TEAC value trend seems to be similar to the carotenoid content of the extracts. On the other hand, the high antioxidant activity of the 200 degrees C water extracts is likely related to the presence of Maillard reaction compounds produced by thermal degradation of the sample. beta-Carotene, lutein, violaxanthin, and neoxanthin were identified in 150 degrees C ethanol extracts. Four different microbial species ( Escherichia coli, Staphylococcus aureus, Candida albicans, and Aspergillus niger) were used to screen the potential antimicrobial activity of the Phormidium sp. extracts. The most sensitive microorganism was the yeast, C. albicans, whereas the fungus, A. niger, was the most resistant. In general, no drastic differences were found for solvents and temperatures tested, showing a very diverse nature of the compounds responsible for the antimicrobial activity of these microalgae. In ethanol extracts, antimicrobial activity could be mainly attributed to the presence of terpenes (i.e., beta-ionone, neophytadiene) and fatty acids (i.e., palmitoleic and linoleic acids) in the samples. Toxicity studies carried out with the extracts evaluated in the present work showed a cellular toxicity lower than those of other cyanobacteria such as Spirulina plantensis. 相似文献
115.
Lacomba R Salcedo J Alegría A Barberá R Hueso P Matencio E Lagarda MJ 《Journal of agricultural and food chemistry》2011,59(10):5755-5762
The effects of simulated gastrointestinal digestion upon sialic acid and gangliosides in infant and follow-on formulas and human milk, as well as their bioaccessibility, have been evaluated. The gastric stage is the step that causes a greater decrease in sialic acid and ganglioside contents. The intestinal stage only decreases the total and individual contents of gangliosides. After gastrointestinal digestion, neither sialic acid nor gangliosides were found in the nonbioaccessible fraction. The highest bioaccessibility (100 × content in soluble fraction after gastrointestinal digestion/total content) of sialic acid is found in human milk (87%), followed by infant formula (77%) and follow-on formula (16%). In the case of gangliosides, the highest bioaccessibility is present in the follow-on formula (51%), followed by human milk (29%) and infant formula (5%). 相似文献
116.
Mardones F Urrutia MT Villarroel L Rioseco A Castillo O Rozowski J Tapia JL Bastias G Bacallao J Rojas I 《Public health nutrition》2008,11(1):30-40
OBJECTIVE: To test the hypothesis that maternal food fortification with omega-3 fatty acids and multiple micronutrients increases birth weight and gestation duration, as primary outcomes. DESIGN: Non-blinded, randomised controlled study. SETTING: Pregnant women received powdered milk during their health check-ups at 19 antenatal clinics and delivered at two maternity hospitals in Santiago, Chile. SUBJECT: Pregnant women were assigned to receive regular powdered milk (n = 477) or a milk product fortified with multiple micronutrients and omega-3 fatty acids (n = 495). RESULTS: Intention-to-treat analysis showed that mean birth weight was higher in the intervention group than in controls (65.4 g difference, 95% confidence interval (CI) 5-126 g; P = 0.03) and the incidence of very preterm birth (0.80 just for mean birth weight and birth length in the on-treatment analysis; birth length in that analysis had a difference of 0.57 cm (95% CI 0.19-0.96 cm; P = 0.003). CONCLUSIONS: The new intervention resulted in increased mean birth weight. Associations with gestation duration and most secondary outcomes need a larger sample size for confirmation. 相似文献
117.
Flavonoids such as quercetin have been shown to serve as a protective defense against oxidative damage in vivo. However, the bioavailability of quercetin depends on the food source and type of glycosidic moiety linked to the molecule. In this study, mice were fed 1 mg/day quercetin in the form of quercetin aglycone, rutin, apple, or onion, and reduced glutathione (GSH), oxidized glutathione (GSSG), and protein-GSH mixed disulfides were determined to investigate the influence of dietary quercetin on the GSH redox status in metabolically active tissues, mitochondria, and plasma of mice. All quercetin treatment groups produced increases in the GSH:GSSG ratio and decreases in mixed disulfide levels in hepatic tissue. Cardiac tissue did not change in response to dietary quercetin; however, cardiac mitochondria demonstrated a reduction in the GSH:GSSG ratio and an increase in protein mixed disulfide levels. No significant changes were observed in the plasma GSH:GSSG ratio, but mixed disulfide levels were decreased for all of the diets. The changes in plasma redox status did not parallel the changes in the tissues. Onion fed mice demonstrated the greatest increases in GSH:GSSG ratios and the greatest decreases in protein mixed disulfide levels of all diets compared. For all treatment groups, increases in the GSH:GSSG ratios corresponded with decreases in protein mixed disulfide levels. The results of this study indicate that quercetin influences GSH:GSSG ratios and protein thiolation in a tissue-specific manner and that these effects are dependent on food source and bioavailability. 相似文献
118.
Lluis Benejam Josep Benito Jaime Ordóñez Joan Armengol Emili García-Berthou 《Water, air, and soil pollution》2008,190(1-4):3-11
Prescribed or natural drawdowns occur frequently in reservoirs but their effects on fish populations have been barely studied. As a consequence of a severe drought and the need to optimize water quality, a partial drawdown was prescribed in autumn 2005 to a eutrophic reservoir that provides water supply to a large metropolitan area (Barcelona, Spain). In order to avoid a potential massive fish kill given the reduced oxygen availability and high fish abundance, preventive purse seine fisheries were performed to reduce the fish stock. The fisheries had little effect on the fish assemblage because final population size structure and species composition did not change significantly. The species composition of the purse seine catches varied significantly during the drawdown with higher proportion of bleak (Alburnus alburnus) in pelagic water during the days of worst water quality, confirming that bleak is more tolerant than roach (Rutilus rutilus) to poor water quality and a potential good indicator of water pollution. The weight–length relationship (i.e. condition) of roach and bleak also varied significantly during the drawdown following the same tendency in both species, losing and recovering their weight (4.99% in roach and 5.96% in bleak) in only 16 days. The close relationship found between water quality and fish condition demonstrates that fish condition can be a good metric of the well being of fish, even for extreme short-term changes. 相似文献
119.
Paulo Cezar Rezende Fontes Juvenal Lopes Loures Everardo Chartuni Mantovani Jaime Barros da Silva Filho 《Journal of plant nutrition》2014,37(2):259-269
A drip fertigation system should use low-cost phosphorus fertilizer available in small markets to smallholders such as especially Brazilian tomato growers. A study was conducted in an unheated greenhouse to establish an optimum rate of single superphosphate (SS) to formulate an aqueous solution that can be applied to tomato plants through a low-pressure drip irrigation system. Five rates of SS [18% phosphorus pentoxide (P2O5)] 0, 25, 50, 100, and 200 g·plant?1, were evaluated in a randomized block design with four replications. Each rate was subdivided into 15 equal parts. Each part was dissolved in water (210 mL for each plant) and the mixture left to settle for 24 hours. The supernatant was applied by drip irrigation every week for 15 weeks. The tomato plants were grown in 9 dm3 plastic bags containing fertilized substrate in an unheated greenhouse. The leaf contents of nitrogen (N), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), copper (Cu), and zinc (Zn) were not affected by the treatments. The highest phosphorus (P), manganese (Mn), and iron (Fe) leaf contents were obtained from plants fertilized with SS at 79; 0; 0 g·plant?1, respectively. The marketable tomato fruit yield, measured up to 123 days after transplanting, increased with the increasing SS up to 54 g·plant?1, resulting in a yield of 6.16 kg·plant?1, corresponding to 10.3 kg·m?2. A settled aqueous solution of SS (54 g·210 mL?1 of water) can be applied weekly to tomato plant through a low-pressure drip irrigation system during the plant cycle. 相似文献
120.
M A Martín-Cabrejas L Jaime C Karanja A J Downie M L Parker F J Lopez-Andreu G Maina R M Esteban A C Smith K W Waldron 《Journal of agricultural and food chemistry》1999,47(3):1174-1182
The objective of this work was to evaluate extrusion cooking as a means to improve the nutritional properties of Phaseolus vulgaris L. that had been stored either at 42 degrees C and 80% relative humidity for 6 weeks or for periods >1 year in cereal stores in tropical conditions. Storage under these conditions resulted in an increase in cooking time increased (7.7- and 12-fold, respectively) as a result of development of the hard-to-cook (HTC) defect. Single-screw extrusion of the milled beans was carried out at four barrel temperatures and two moisture contents. The extrudate bulk density and water solubility index decreased with increasing temperature, whereas the water absorption index increased due to the higher proportion of gelatinized starch in the extruded samples. Both fresh and HTC beans contained nutritionally significant amounts of lectins, trypsin, and alpha-amylase inhibitors, which were mostly inactivated by extrusion. Extrusion also caused a considerable redistribution of insoluble dietary fiber to soluble, although the total dietary fiber content was not affected. Changes in solubility involved pectic polysaccharides, arabinose and uronic acids being the main sugars involved. Stored beans subjected to extrusion cooking showed physical and chemical characteristics similar to those of extrudates from fresh beans. 相似文献