全文获取类型
收费全文 | 1204篇 |
免费 | 115篇 |
国内免费 | 15篇 |
专业分类
林业 | 89篇 |
农学 | 63篇 |
基础科学 | 6篇 |
219篇 | |
综合类 | 137篇 |
农作物 | 71篇 |
水产渔业 | 125篇 |
畜牧兽医 | 541篇 |
园艺 | 19篇 |
植物保护 | 64篇 |
出版年
2024年 | 9篇 |
2023年 | 25篇 |
2022年 | 32篇 |
2021年 | 53篇 |
2020年 | 63篇 |
2019年 | 65篇 |
2018年 | 58篇 |
2017年 | 63篇 |
2016年 | 68篇 |
2015年 | 60篇 |
2014年 | 58篇 |
2013年 | 55篇 |
2012年 | 95篇 |
2011年 | 85篇 |
2010年 | 70篇 |
2009年 | 48篇 |
2008年 | 58篇 |
2007年 | 67篇 |
2006年 | 44篇 |
2005年 | 34篇 |
2004年 | 33篇 |
2003年 | 40篇 |
2002年 | 27篇 |
2001年 | 21篇 |
2000年 | 25篇 |
1999年 | 10篇 |
1998年 | 9篇 |
1997年 | 6篇 |
1996年 | 11篇 |
1995年 | 1篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1954年 | 1篇 |
1948年 | 1篇 |
排序方式: 共有1334条查询结果,搜索用时 19 毫秒
81.
Juliano Lino Ferreira José Eustáquio de Souza Carneiro Alexsandro Lara Teixeira Fabiéli Fortunata de Lanes Paulo Roberto Cecon Aluízio Borém 《Euphytica》2007,153(1-2):165-170
This study was conducted in Brazil in order to assess the potential risk posed by gene escape from transgenic into non-transgenic plants and wild populations. A new methodology was applied to evaluate the gene flow between common bean cultivars, by means of a specially delineated experiment in two stages. The first stage consisted of the planting of one cultivar with violet flowers (BB) as pollen source (‘Diamante Negro’), and a receiver (‘Talismã’) with white flowers (bb), at different distances. The source was sown in the center of the area. The pollen receiver cultivar was sown, in concentrical squares around it. At maturity, the rows were sampled at varied distances from the source in the four cardinal directions. In the second stage, the sampled seeds of the previous stage were sown, and the percentage of outcrossing was evaluated during flowering through the presence of violet flowers (Bb). The highest frequency of natural hybrids, 0.136%, occurred at a distance of 0.5 m between the cultivars. The natural outcrossing rate was practically zero beyond a distance of 3.25 m. 相似文献
82.
Cytoprotection by neutral fraction of tannat red wine against oxidative stress-induced cell death 总被引:1,自引:0,他引:1
Echeverry C Blasina F Arredondo F Ferreira M Abin-Carriquiry JA Vasquez L Aspillaga AA Diez MS Leighton F Dajas F 《Journal of agricultural and food chemistry》2004,52(24):7395-7399
Some of the beneficial effects of the Mediterranean diet on human pathologies have been attributed to red wine polyphenols. It has been postulated that the antioxidant activity of the latter would be also responsible for the cytoprotective capacity of red wine that has been reported in a few papers. Nevertheless, red wine shows a complex composition, and the active fraction is not known yet. In this context, the protective capacity of total lyophilized extracts of red wine and anthocyanin, neutral, or acidic fractions, was explored in PC12 cells in culture after a hydrogen peroxide insult. Although all fractions showed high antioxidant activity, only the neutral fraction was cytoprotective. The analysis of this active fraction showed that it was rich in the aglycons quercetin and myricetin as well as the glycosides of kaempferol, isorhamnetin, epicatechin, and catechin, some of which are known to be cytoprotective. This is the first paper to reveal the active fraction of total wine responsible of its cytoprotection. 相似文献
83.
Kamara BI Brandt EV Ferreira D Joubert E 《Journal of agricultural and food chemistry》2003,51(13):3874-3879
The fermented leaves and stems of Cyclopia intermedia are used to brew Honeybush tea, a herbal tea indigenous to South Africa. The plant is also used to manufacture a sweet herbal infusion used for restorative properties such as soothing coughs and alleviating bronchial complaints including tuberculosis, pneumonia, and catarrh. It is claimed to have a low tannin content and no caffeine and contains various antioxidants. Continued investigations into the phenolic content of the leaves and stems of C. intermedia yielded tyrosol and a methoxy analogue, 2-[4-[O-alpha-apiofuranosyl-(1' '-->6')-beta-d-glucopyranosyloxy]phenyl]ethanol, 4-[O-alpha-apiofuranosyl-(1' '-->2')-beta-d-glucopyranosyloxy]benzaldehyde, five glycosylated flavonols, two isoflavones, four flavanones, two isoflavones, and two flavones. Structure elucidation was done by NMR, CD, and MS methods. Because flavonoids are presumed to contribute significantly toward the scavenging effects of active oxygen species, our results indicate that the tentative claimed health-promoting properties may be attributed to the presence of these and other phenolics in C. intermedia. 相似文献
84.
Oliveira CM Silva Ferreira AC Guedes De Pinho P Hogg TA 《Journal of agricultural and food chemistry》2002,50(7):2121-2124
This work describes a new potentiometric method to evaluate the resistance to oxidation of white wines. Reduction and oxidation titrations were made, and coefficient of variation obtained were 10.87 and 2.65%, respectively. The antioxidant powers of ascorbic acid (Aas) and sulfur dioxide (SO(2)) were evaluated by this method, SO(2) proving to be much less active in this respect than ascorbic acid. The two agents did not demonstrate any antioxidant synergy. A relationship between oxygen present and ascorbic acid was found by the proposed method (1 mmol of O(2) <--> 0.84 mmol of Aas). This method enables the distinction of different wines on the basis of their resistance to oxidation. 相似文献
85.
Silva RD Bueno AL Gallon CW Gomes LF Kaiser S Pavei C Ortega GG Kucharski LC Jahn MP 《Fitoterapia》2011,82(6):818-826
This study analyzed the plasma lipid profile, glucose levels and fat deposits in male rats treated with aqueous extract of gross yerba mate, commercial yerba mate or water. Yerba mate treatment did not change body weight gain and lipid profile. The consumption of gross yerba mate significantly increased blood glucose (6.6 mmol/L) as compared to the water (4.8 mmol/L) and commercial group (5.2 mmol/L) and decreased epididymal and intra-abdominal deposits (10.1 mg/g and 23.7 mg/g of weight) as compared to the water (15.4 mg/g and 36.9 mg/g of weight) and commercial group (12.5 mg/g and 28 mg/g of weight). The results suggest that gross yerba mate reduces fat more efficiently but produces a greater increase in blood glucose when compared to commercial yerba mate and water groups. 相似文献
86.
Effect of coupling media on velocity and attenuation of ultrasonic waves in Brazilian wood 总被引:1,自引:0,他引:1
Raquel?Gon?alvesEmail author Alex?Julio?Trinca Gisleiva?Cristina?dos?Santos Ferreira 《Journal of Wood Science》2011,57(4):282-287
Coupling media are necessary to ensure that transducers bond to wood specimens to minimize coupling losses and improve the
accuracy of ultrasonic measurements. There are several types of coupling media available, and the optimal choice is not known.
In this work, we analyzed the results of ultrasonic wave attenuation for 0.1-MHz longitudinal and transverse transducers with
six different materials as coupling media in nine species of Brazilian wood with densities in the range 700–1170 kg/m3. Tests were performed using constant pressure on the transducer and with wave propagation in the longitudinal direction.
For transverse transducers, the polarization was in the radial and tangential directions. The results were analyzed statistically
and showed that, for attenuation in both longitudinal and transverse waves, the material used for coupling had significant
effects, whereas the wood species had no effect. For longitudinal waves, the statistical evaluation showed that the coupling
material performance was strongly dependent on the species of wood, but it was not possible to observe any tendency of behavior
associated with specific anatomical properties. 相似文献
87.
Mendes-Pinto MM Silva Ferreira AC Caris-Veyrat C Guedes de Pinho P 《Journal of agricultural and food chemistry》2005,53(26):10034-10041
Carotenoids and chlorophyll-derived compounds in grapes and Port wines were investigated by HPLC-DAD and HPLC-DAD-MS (ESP+) analysis. A total of 13 carotenoid and chlorophyll-derived compounds are formally reported in grapes, 3 are identified for the first time, pheophytins a and b and (13Z)-beta-carotene, and 3 others remain unknown. In Port wines 19 compounds with carotenoid or chlorophyll-like structures are present, 8 still unidentified. The young wines showed higher total carotenoid content and chlorophyll-like compounds compared to aged Ports, with lutein and beta-carotene as major carotenoids. Among samples analyzed of monovarietal Vitis vinifera L. cultivar wines produced with the five most important Douro varieties, Tinta Roriz contained the highest levels of carotenoids and Touriga Franca the lowest. The forced-aging study indicated that lutein was more sensitive to temperature than beta-carotene. Additionally, aged wines showed higher ratios of beta-carotene/lutein concentrations compared to new Ports. Rates of degradation of chlorophyll derivative compounds were higher than those for carotene and lutein. 相似文献
88.
Monteiro S Piçarra-Pereira MA Mesquita PR Loureiro VB Teixeira A Ferreira RB 《Journal of agricultural and food chemistry》2001,49(8):3999-4010
In the present work, single grape variety wines, Moscatel and Arinto, were used. Analysis by denaturing polyacrylamide gel electrophoresis of the wine proteins revealed the presence of only a few polypeptides ranging in molecular mass from 15 to 30 kDa. However, a more detailed examination of the whole protein fraction, by a combination of techniques, showed that these wines contain a very large number (many tens and, possibly, many more) of distinct polypeptides, exhibiting similar molecular masses but different electrical charges. The results obtained using highly specific antibodies and N-terminal sequencing indicate that there is structural similarity among most of the wine polypeptides. These observations can be explained by the existence of a common precursor to most or all of the wine proteins, which could generate all of the detected polypeptides by limited proteolysis. Comparison of the N-terminal sequences of the polypeptides isolated from Moscatel wine with proteins from other sources revealed a high degree of homology to pathogenesis-related proteins. 相似文献
89.
Free amino acid composition of quince (Cydonia oblonga Miller) fruit (pulp and peel) and jam 总被引:2,自引:0,他引:2
Silva BM Casal S Andrade PB Seabra RM Oliveira MB Ferreira MA 《Journal of agricultural and food chemistry》2004,52(5):1201-1206
Twenty-one free amino acids present in several samples of quince fruit (pulp and peel) and quince jam (homemade and industrially manufactured) were analyzed by GC/FID. The analyses showed some differences between quince pulps and peels. Generally, the highest content in total free amino acids and in glycine was found in peels. As a general rule, the three major free amino acids detected in pulps were aspartic acid, asparagine, and hydroxyproline. For quince peels, usually, the three most abundant amino acids were glycine, aspartic acid, and asparagine. Similarly, for quince jams the most important free amino acids were aspartic acid, asparagine, and glycine or hydroxyproline. This study suggests that the free amino acid analysis can be useful for the evaluation of quince jam authenticity. It seems that glycine percentage can be used for the detection of quince peel addition while high alanine content can be related to pear addition. 相似文献
90.
Rangel A Domont GB Pedrosa C Ferreira ST 《Journal of agricultural and food chemistry》2003,51(19):5792-5797
The major storage globulins (vicilins) of cowpea (Vigna unguiculata) and pea (Pisum sativum) seeds were purified by ammonium sulfate precipitation, and a semipurified cowpea protein isolate (CPI) was prepared by isoelectric precipitation. Some of the functional properties of these proteins, including solubility, foaming, and emulsifying capacities, were investigated and compared. The solubility of purified cowpea vicilin was reduced at pH 5.0, increasing markedly below and above this value. Pea vicilin exhibited poor solubility between pH 5.0 and pH 6.0, and CPI was little soluble in the pH range from 4.0 to 6.0. At neutral pH, the emulsifying activity indexes (EAI) of purified pea vicilin and CPI were 194 and 291 m(2)/g, respectively, which compare quite favorably to EAIs of 110 and 133 m(2)/g for casein and albumin, respectively. Remarkably, purified cowpea vicilin exhibited an EAI of 490 m(2)/g, indicating a very high emulsifying activity. Purified cowpea and pea vicilins exhibited lower foaming capacities and foam stablity indexes (FSI) than CPI. FSI values of 80 and 260 min were obtained for purified pea and cowpea vicilin, respectively, whereas a FSI value of 380 min was obtained for CPI. These results are discussed in terms of the possible utilization of purified vicilins or protein isolates from pea and cowpea in the food processing industry. 相似文献