全文获取类型
收费全文 | 3542篇 |
免费 | 211篇 |
国内免费 | 139篇 |
专业分类
林业 | 225篇 |
农学 | 189篇 |
基础科学 | 102篇 |
605篇 | |
综合类 | 720篇 |
农作物 | 222篇 |
水产渔业 | 337篇 |
畜牧兽医 | 1129篇 |
园艺 | 120篇 |
植物保护 | 243篇 |
出版年
2024年 | 10篇 |
2023年 | 45篇 |
2022年 | 104篇 |
2021年 | 122篇 |
2020年 | 137篇 |
2019年 | 131篇 |
2018年 | 143篇 |
2017年 | 165篇 |
2016年 | 123篇 |
2015年 | 120篇 |
2014年 | 176篇 |
2013年 | 234篇 |
2012年 | 247篇 |
2011年 | 241篇 |
2010年 | 182篇 |
2009年 | 160篇 |
2008年 | 225篇 |
2007年 | 186篇 |
2006年 | 155篇 |
2005年 | 121篇 |
2004年 | 101篇 |
2003年 | 89篇 |
2002年 | 101篇 |
2001年 | 83篇 |
2000年 | 77篇 |
1999年 | 60篇 |
1998年 | 17篇 |
1997年 | 23篇 |
1996年 | 20篇 |
1995年 | 31篇 |
1994年 | 9篇 |
1993年 | 15篇 |
1992年 | 16篇 |
1991年 | 19篇 |
1990年 | 15篇 |
1989年 | 16篇 |
1988年 | 16篇 |
1987年 | 13篇 |
1986年 | 12篇 |
1985年 | 11篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1979年 | 7篇 |
1976年 | 7篇 |
1973年 | 10篇 |
1970年 | 6篇 |
1968年 | 6篇 |
1967年 | 8篇 |
排序方式: 共有3892条查询结果,搜索用时 0 毫秒
991.
Le Gall G Colquhoun IJ Davis AL Collins GJ Verhoeyen ME 《Journal of agricultural and food chemistry》2003,51(9):2447-2456
992.
Cantos E Espín JC López-Bote C de la Hoz L Ordóñez JA Tomás-Barberán FA 《Journal of agricultural and food chemistry》2003,51(21):6248-6255
The aim of the present work was to identify and quantify the phenolic compounds and fatty acids in acorns from Quercus ilex, Quercus rotundifolia, and Quercus suber. The concentration of oleic acid was >63% of total fatty acids in all cases, followed by palmitic and linoleic acids at similar concentrations (12-20%). The concentrations of alpha-tocopherol in Q. rotundifolia, Q. ilex, and Q. suber were 19, 31, and 38 mg/kg of dry matter (DM), respectively, whereas the concentrations of gamma-tocopherol were 113, 66, and 74 mg/kg of DM, respectively. Thirty-two different phenolic compounds were distinguished. All of them were gallic acid derivatives, in the form of either galloyl esters of glucose, combinations of galloyl and hexahydroxydiphenoyl esters of glucose, tergallic O- or C-glucosides, or ellagic acid derivatives. Several tergallic acid C-glucosides were also present in the extracts obtained from Q. suber. Acorns from Q. ilex and Q. rotundifolia showed similar polyphenol patterns mainly with gallic acid-like spectra. Chromatograms of Q. suber showed mainly polyphenols with ellagic acid-like spectra. Valoneic acid dilactone was especially abundant in Q. suber skin. The contribution of skin to the total phenolics of the acorn was relatively small in Q. rotundifolia and Q. ilex but relatively high in Q. suber. Skin extracts from Q. suber, Q. rotundifolia, and Q. ilex showed 1.3, 1.4, and 1.0 antioxidant efficiencies, respectively (compared to that of butylhydroxyanisole). Endosperm extracts showed lower capacity to prevent lipid peroxidation than skin extracts. 相似文献
993.
Narváez-Rivas M Vicario IM Constante EG León-Camacho M 《Journal of agricultural and food chemistry》2008,56(16):7131-7137
In this study, we have evaluated the changes that occur in the profiles of total fatty acids and triacylglycerols during the dry-curing process (730 days) of Iberian ham. The subcutaneous adipose tissues of six hams obtained from three Iberian pigs fed on acorns were analyzed periodically during the processing time (from the raw to the dry-cured samples), including postsalting, drying, and ripening stages. The environmental conditions were also registered. The curing process significantly decreased (p < 0.01) the relative percentages of total polyunsaturated fatty acids, including C18:2n-6 and C18:3n-3 and, therefore, significantly increased (p < 0.05) the level of monounsaturated fatty acids. The triglycerides containing 0-2 double bonds showed an increase during the curing process. On the contrary, the more unsaturated ones (3-5 double bonds) suffered a significant decrease. We have postulated that these changes could also be due to polymerization and oxidation reactions that affect the triacylglycerols and besides the fatty acids. In general, most fatty acids and triacylglycerols reversed the trend by about 500-600 days of processing. 相似文献
994.
Javier López-Miranda Sergio Cisneros-de la Cueva Jesús Bernardo Páez-Lerma Juan Antonio Rojas-Contreras Nicolás Oscar Soto-Cruz 《Water, air, and soil pollution》2018,229(5):165
The goal of this study was to evaluate the effect of high Tween 80 concentrations on hydrocarbon contaminants and hydrocarbonoclastic microorganisms present in contaminated mining soil during a bioremediation process. The independent variables included Tween 80 concentration and process time. The elected response variables included concentration of total petroleum hydrocarbons (TPH), the chemical composition of contaminants, viable microbial count, and CO2 production. These were measured at various time points during the bioremediation process, which was conducted at room temperature. Higher removal of pollutants occurred at low Tween 80 concentrations. An analysis of the normalized variables shows that the rate of TPH degradation depended on microbial growth rate, which depended on Tween 80 concentration. The addition of Tween 80 changed the concentration and type of the residual hydrocarbon contaminants present, as well as the count and genus of the hydrocarbonoclastic microorganisms that grew during the bioremediation process. Higher concentrations of Tween 80 increased the levels of the chemical compounds present in the bioremediated soil while reducing the viable count and microbial diversity during the bioremediation process. Conversely, low Tween 80 concentrations produced only monoethylhexyl phthalate, which is not a petroleum hydrocarbon derivative. Overall, these results prove that the removal of TPH is dependent on the count and genus of active indigenous hydrocarbonoclastic microorganisms in soil, and these conditions may be controlled by modulating the concentration of Tween 80 that is applied. 相似文献
995.
Quang Dung Le Kotaro Shirai Duc Cu Nguyen Nobuyuki Miyazaki Takaomi Arai 《Water, air, and soil pollution》2009,204(1-4):69-78
In order to understand the present status of heavy metal contamination and the risk associated with human consumption, commercial freshwater eels in Vietnam were examined. The concentration of eight elements (Cr, Mn, Co, Cu, Zn, Sr, Cd, and Pb) was determined in muscle tissue of tropical eel Anguilla marmorata collected in four provinces, Quang Tri, Quang Ngai, Binh Dinh, and Phu Yen, from the central part of Vietnam. Concentrations of Cu, Zn, Cd, and Sr were found to be highest, whereas Co concentration showed the lowest at Quang Tri. Cr was recorded to be lowest in Quang Ngai, while the amounts of Mn and Pb did not vary among locations. Although the metal concentrations in the muscle of A. marmorata did not represent a risk for human consumption, elevated Cd concentrations in Quang Tri related to agriculture activities suggest that further investigations should be undertaken to clarify the potential risk to the eel population. 相似文献
996.
997.
Biodiversity conservation does predominantly focus on protected natural areas, but has to consider also the usually Human-dominated matrix in which these natural areas are embedded. Here we study highway stormwater retention ponds, which may act as refuges for native flora and fauna and contribute to the maintenance of biodiversity in Human-dominated landscapes. However, the biodiversity supported by such artificial ponds has received little attention so far. Using standardised methods, we addressed the potential role of highway stormwater ponds as refuges by comparing aquatic macroinvertebrate communities (Coleoptera, Heteroptera, Odonata and Gastropoda) in highway stormwater ponds with ponds in the wider landscape. As expected from their pollutant retention function, highway ponds differed in abiotic conditions from surrounding ponds. However, they supported aquatic macroinvertebrate communities at least as rich and diverse at the family level as surrounding ponds and exhibited similar variability in family community composition and structure. The main difference we observed was a higher abundance of small and/or short-lived invertebrates in the highway ponds. These similar community compositions and structures suggest that highway ponds contribute to the biodiversity of the pond network at a regional scale. Thus, road practitioners should consider highway ponds not only for their hydrological and pollutant retaining purposes but also as a possibility to increase the role of highway verges as a refuge and, consequently, landscape connectivity. The management of these water bodies should recognise their potential for biodiversity especially in Human-dominated landscapes. 相似文献
998.
Guillén-Casla V Pérez-Arribas LV León-González ME Polo-Díez LM 《Journal of agricultural and food chemistry》2008,56(7):2303-2309
Simple one- and two-dimensional high-performance liquid chromatography (HPLC) methods for the simultaneous enantiomeric determination of alkyloxyphenoxypropionic acid herbicides is presented. Compounds studied were ( R, S)-2-[4-(2,4-dichlorophenoxy)phenoxy]propionic acid (diclofop-acid) and ( R, S)-2-[4-(2,4-dichlorophenoxy)]methyl propionate (diclofop-methyl). Mobile phases necessary to separate their enantiomers on an alpha1-acid glycoprotein chiral stationary phase are different; therefore, the simultaneous separation by an isocratic mode is not possible. The chiral separation method proposed involves a one-step gradient allowing for the simultaneous determination of both racemic enantiomers. Detection limits of the method were 0.03 mg/L for both diclofop-acid enantiomers and 0.14 and 0.15 mg/L for diclofop-methyl enantiomers, respectively. The two-dimensional method involves the use of two chromatographs in one achiral-chiral coupling. The LC-LC method is more suitable for complex samples because it involves an online cleanup effect. Detection limits were 1.25 and 1.87 mg/L for diclofop-acid and 2.70 and 3.02 mg/L for diclofop-methyl enantiomers, respectively. Accuracy, repeatability, and reproducibility have been studied in standard samples and a technical product. 相似文献
999.
Sodium iron ethylenediaminetetraacetate (NaFeEDTA) has considerable promise as an iron fortificant in food. However, effects of administering high levels of NaFeEDTA on tissue iron distribution and mineral excretion are not well understood. The objectives of this study were to assess nonheme iron distribution in the body and urinary excretion of Ca, Mg, Cu, Fe, and Zn after daily administration of high levels of iron to rats over 21 days. Iron was either given orally with food or injected subcutaneously, as either FeSO 4 or NaFeEDTA. Selected tissues were collected for nonheme iron analysis. Estimated total body nonheme iron levels were similar in rats fed NaFeEDTA or FeSO 4, but the tissue distribution was different: it was 53% lower in the liver and 86% higher in the kidneys among rats fed NaFeEDTA than among those fed FeSO 4. In contrast, body nonheme iron was 3.2-fold higher in rats injected with FeSO 4 than in rats injected with NaFeEDTA. Administering NaFeEDTA orally elevated urinary Cu, Fe, and Zn excretion compared with FeSO 4 (1.41-, 11.9-, and 13.9-fold higher, respectively). We conclude that iron is dissociated from the EDTA complex prior to or during intestinal absorption. A portion of intact FeEDTA may be absorbed via a paracellular route at high levels of intake but is mostly excreted in the urine. Metal-free EDTA may be absorbed and cause elevated urinary excretion of Fe, Cu, and Zn. 相似文献
1000.
Bernard H Mondoulet L Drumare MF Paty E Scheinmann P Thaï R Wal JM 《Journal of agricultural and food chemistry》2007,55(23):9663-9669
Numerous food allergens of plant origin belong to the 2S albumin family, including peanut Ara h 2. In addition to Ara h 2, several other conglutins related to 2S albumins are present in peanut seeds. We evaluated the allergenicity of different peanut conglutins as compared with Ara h 2. Several conglutins were isolated from the kernel, i.e. Ara h 2, a new isoform of Ara h 6 and its derived product, which is likely to be naturally formed during seed processing. Enzyme allergosorbent tests performed on sera of peanut allergic patients showed that more than 94% of 47 analyzed patients had positive IgE responses to Ara h 6 isoform and to its degradation product. Skin prick tests with the new isoform of Ara h 6 led to a positive response in seven out of the eight tested patients. Both enzyme allergosorbent tests and skin prick tests showed that the reactivity of Ara h 6 was similar to, or even higher than, that of Ara h 2, suggesting that the present isoform of Ara h 6 is as allergenic as Ara h 2. In addition the IgE response to the plant processed (i.e., hydrolyzed) Ara h 6 new isoform is equivalent to the IgE response to the native isoform. The IgE immunoreactivity is mostly abrogated by chemical reduction and denaturation of Ara h 6 isoforms, which underlined the importance of tertiary structure in Ara h 6 immunoreactivity. These results, and particularly the high correlation between anti-Ara h 2 and anti-Ara h 6 IgE responses, emphasise the major role of 2S albumins in peanut allergenicity. 相似文献