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991.
Macías FA Galindo JC Castellano D Velasco RF 《Journal of agricultural and food chemistry》2000,48(11):5288-5296
A structure-activity study to evaluate the effect of 17 guaianolide sesquiterpene lactones (in a range of 100-0.001 microM) on the growth and germination of several mono- and dicotyledon target species is accomplished. Results are compared with those obtained in the same bioassay with an internal standard, the commercial herbicide Logran, to validate the results with a known active formulation and to compare the results with a commercial product to test their potential use as natural herbicide models. Specific conditions for the selective mono- or polyhydroxylation of guaianolides using the SeO(2)/tert-butyl hydroperoxide system are presented and discussed. The high regio- and stereoselectivities of the reaction are explained through the specific structural requirements of the bulky first adduct formed during the ene reaction. These compounds appear to have deeper effects on the growth of either monocots or dicots than the previously tested germacranolides. Otherwise, the lactone group seems to be necessary for the activity, though it does not necessarily need to be unsaturated. However, the presence of a second and easily accessible unsaturated carbonyl system greatly enhances the inhibitory activity. Lipophilicity and the stereochemistry of the possible anchoring sites are also crucial factors for the activity. Finally, the levels of growth inhibition obtained with some compounds on dicots or monocots are totally comparable to those of Logran and allow proposing them as lead compounds. 相似文献
992.
Romero C Brenes M García P García A Garrido A 《Journal of agricultural and food chemistry》2004,52(7):1973-1979
The individual evolution of phenolic compounds has been studied during the natural fermentation of black olives for the first time. Cyanidin 3-rutinoside and cyanidin 3-glucoside were the main anthocyanins identified in fresh olives, and they were not detected after 1 month of storage either in brine or in olive. The fruit colors were different when aerobic or anaerobic conditions were used and as a consequence of the different anthocyanin polymerizations that took place. At time zero, the polyphenols observed in the olive juice were hydroxytyrosol-4-beta-glucoside, oleuropein, hydroxytyrosol, tyrosol, salidroside, and verbascoside and, after 12 months, the main phenol was hydroxytyrosol. The polyphenol content in the oil phase of olives was also analyzed. The dialdehydic form of elenolic acid linked to hydroxytyrosol and tyrosol, oleuropein aglycon, and ligstroside aglycon were the main compounds found at the beginning of fermentation but were not detected after 3 months. In contrast, hydroxytyrosol, hydroxytyrosol acetate, tyrosol, and tyrosol acetate were the main polyphenols detected in the oil phase of the final product. The acid hydrolysis of the initial glucosides (in olive juice) and the aglycons (in oil phase) was, therefore, the main reaction that took place during fermentation. 相似文献
993.
Gutiérrez A Rodríguez IM Del Río JC 《Journal of agricultural and food chemistry》2004,52(15):4764-4773
The chemical composition of lignin and lipids of bast fibers from kenaf (Hibiscus cannabinus) used for high-quality paper pulp production was studied. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) of fibers showed a lignin with a high syringyl/guaiacyl ratio (5.4) and minor amounts of p-hydroxyphenyl units. Simultaneously, sinapyl and coniferyl acetates were also identified, indicating that this lignin is partially acetylated. p-Hydroxycinnamic acids were found in only trace amounts. The main lipids identified by GC/MS of extracts from kenaf fibers were series of long-chain n-fatty acids, waxes, n-alkanes, and n-fatty alcohols. Free and esterified sterols and triterpenols, steroid hydrocarbons, and steroid and triterpenoid ketones, as well as steryl glycosides, were also found. Finally, the fate of the main constituents of kenaf fibers in alkaline pulping was also investigated. 相似文献
994.
Castro SM Van Loey A Saraiva JA Smout C Hendrickx M 《Journal of agricultural and food chemistry》2004,52(18):5724-5729
Pectin methylesterase (PME) from green bell peppers (Capsicum annuum) was extracted and purified by affinity chromatography on a CNBr-Sepharose-PMEI column. A single protein peak with pectin methylesterase activity was observed. For the pepper PME, a biochemical characterization in terms of molar mass (MM), isoelectric points (pI), and kinetic parameters for activity and thermostability was performed. The optimum pH for PME activity at 22 degrees C was 7.5, and its optimum temperature at neutral pH was between 52.5 and 55.0 degrees C. The purified pepper PME required the presence of 0.13 M NaCl for optimum activity. Isothermal inactivation of purified pepper PME in 20 mM Tris buffer (pH 7.5) could be described by a fractional conversion model for lower temperatures (55-57 degrees C) and a biphasic model for higher temperatures (58-70 degrees C). The enzyme showed a stable behavior toward high-pressure/temperature treatments. 相似文献
995.
Martínez-Villaluenga C Frias J Gulewicz K Vidal-Valverde C 《Journal of agricultural and food chemistry》2004,52(23):6920-6922
Improvement of a previously described method of purification of alpha-galactosides, members of the raffinose family of oligosaccharides (RFOs), has been developed for lupins. The considerable amount of sucrose present in the RFO preparations obtained by the previous method has been removed by modifying the purification stage on diatomaceous earth and charcoal. The present method allows for the preparation of high-purity RFOs containing approximately 99.4% of RFOs in the form of a white fine powder, which provides new perspectives for the production of pure alpha-galactoside preparations for their use as prebiotics in functional foods. 相似文献
996.
997.
998.
Lucas R Robles A García MT Alvarez De Cienfuegos G Gálvez A 《Journal of agricultural and food chemistry》2001,49(1):79-85
The hyphomycete Chalara (syn. Thielaviopsis) paradoxa produces endoglucanase activity during the late trophophase. The low molecular mass (35 kDa) endoglucanase purified from cultured broths works optimally at 37 degrees C and pH 5.0. The enzyme inactivates at pH below 3.0 and also at temperatures of 50 degrees C or higher, but it is stable at lower temperatures, including refrigeration temperature and freezing. The enzyme is inhibited by detergents, by EDTA, and by the divalent cations Hg(2+) and Ag(2+). It is also inhibited to some extent by 10 mM Zn(2+), Fe(2+), and Mg(2+), but it is stimulated by Mn(2+). Enzyme activity is not affected by reducing agents. In the presence of low concentrations of water miscible organic solvents (20%) endoglucanase activity is inhibited by 7% (for methanol) to 50% (for acetonitrile), and it is totally inhibited at higher solvent concentrations (50%). Enzyme activity is not affected by the water immiscible solvent ethyl acetate. Carboxymethylcellulose is the preferred substrate (K(m(app)) = 8.3 g/L; V(max(app)) = 1.1 microM/min). Hydrolysis of crystalline cellulosic substrates is very limited, but it is greatly enhanced by phosphoric acid swelling. The purified enzyme shows no activity toward disaccharides or aryl-glucosides. Its activity is inhibited by cellobiose. 相似文献
999.
Andrades MS Sánchez-Martín MJ Sánchez-Camazano M 《Journal of agricultural and food chemistry》2001,49(5):2363-2369
Adsorption and mobility of the fungicide metalaxyl were studied in 16 vineyard soils from the La Rioja region (Spain), with organic matter (OM) contents in the 0.31--1.37% range, and in 7 natural soils with OM contents in the 3.30--8.24% range. Adsorption isotherms were obtained using the batch equilibrium technique, and mobility was studied by soil thin-layer chromatography (soil-TLC). In all cases, the adsorption isotherms fit the Freundlich equation. The values of the K(f) constants were low in the vineyard soils (0.01--0.64) and increased in the natural soils (1.05--2.83). The n(f) values were in general lower than unity. K(f) constants were significantly correlated (p < 0.001) with the OM content when all of the soils were considered. According to the determination coefficient, r(2), OM would account for 88% of the variance in adsorption. When the vineyard soils alone were considered, a significant correlation was seen between K(f) and the OM and clay contents; both parameters, varying simultaneously, explain 80% of the variance in adsorption. Study of the mobility of metalaxyl with soil-TLC indicated that in vineyard soils the fungicide has the potential for being highly mobile in 19% of the soils and mobile in 81% of them. In natural soils, the fungicide has the potential for being moderately mobile or mobile in 86 and 14% of the soils, respectively. This type of behavior of metalaxyl indicates that in vineyards soils of the La Rioja region (Spain) with low OM contents, where application of the compound is continuous, a leaching of the fungicide from the soil to groundwaters could potentially occur. These results should be borne in mind when metalaxyl is to be used in the soils of this region. 相似文献
1000.
Segura Carretero A Cruces-Blanco C Soriano Peña M Cortacero Ramírez S Fernández Gutiérrez A 《Journal of agricultural and food chemistry》2004,52(6):1419-1422
A test mixture of five phytohormones [naphthaleneacetic acid (NAA), naphthoxyacetic acid (NOA), indoleacetic acid (IAA), indolebutyric acid (IBA), and indolepropionic acid (IPA)] was investigated. These compounds were cleanly separated with good resolution by capillary zone electrophoresis with a UV diode array detector using 20 mM sodium phosphate buffer (pH 7.25). The lowest detection limit was obtained for IPA (0.45 mg L(-)(1) or 0.005 mg kg(-)(1)) and the highest for NAA (1.04 mg L(-)(1) or 0.014 mg kg(-)(1)). The method has been applied for tomato samples fortified with the five phytohormones using a liquid-liquid extraction procedure, obtaining recovery percentages ranging from 91 to 109.0%. 相似文献