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51.
Rapid advances in the chemistry of enols and other reactive species have been made possible recently by the development of methods for generating these short-lived substances in solution under conditions where they can be observed directly and their reactions can be monitored accurately. New laboratory techniques are described and a sample of the new chemistry they have made available is provided; special attention is given to ynols and ynamines and the remarkable effects that the carbon-carbon triple bonds of these substances have on their acid-base properties. 相似文献
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Summary The individual chromosomes of cabbage are identifiable in nucellar cells found in the ovaries of immature pistils by the combination of their relative length, arm ratios, secondary constrictions, chromatic and achromatic regions and the presence of satellites. 相似文献
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Summary Heads of 59 commercial cabbage cultivars, all susceptible to clubroot disease, and of 86 individual clubroot resistant cabbage plants of various breeding selections were analysed for their composition in glucosinolates, determined by quantifying their hydrolytic breakdown products, thiocyanate, goitrin, and volatile isothiocyanates. The mean thiocynate ion content was significantly lower in the breeding selections (120 g/g dry weight) than in the commercial cultivars (204 g/g). In contrast, the mean goitrin content was significantly higher in the breeding selections (193 g/g) than in the commercial cultivars (35 g/g). Similar to goitrin, the range of volatile isothiocyanates and total glucosinolate were higher in the breeding selections, but the mean contents of each were not statistically different between selections and cultivars. Fourteen cultivars and four selections were found to be free of goitrin; three cultivars, but no breeding selection were free of volatile isothiocyanates. The breeding selections will provide germplasm for breeding new clubroot resistant and low glucosinolate cultivars.Contribution No. J-965. 相似文献
57.
Rapid screening of wood chemical component variations using transmittance near-infrared spectroscopy
Yeh TF Yamada T Capanema E Chang HM Chiang V Kadla JF 《Journal of agricultural and food chemistry》2005,53(9):3328-3332
A rapid transmittance near-infrared (NIR) spectroscopy method was developed to predict the variation in chemical composition of solid wood. The effect of sample preparation, sample quantity (single versus stacked multiple wood wafers), and NIR acquisition time on the quantification of alpha-cellulose and lignin content was investigated. Strong correlations were obtained between laboratory wet chemistry values and the NIR-predicted values. In addition to the experimental protocol and method development, improvements in calibration error associated with utilizing stacked multiple wood wafers as opposed to single wood wafers are also discussed. 相似文献
58.
Chen HH Chiang W Chang JY Chien YL Lee CK Liu KJ Cheng YT Chen TF Kuo YH Kuo CC 《Journal of agricultural and food chemistry》2011,59(12):6444-6452
Adlay has long been used in traditional Chinese medicine and as a nourishing food. The acetone extract of adlay hull had previously been demonstrated to possess potent antimutagenic activity. The aims of this study were to identify the antimutagenic constituents from adlay hull by using Ames antimutagenic activity-guide isolation procedures and to investigate their chemopreventive efficacies in cultured cells. The results demonstrated that six compounds showing great antimutagenic activity were identified by spectroscopic methods and by comparison with authentic samples to be p-hydroxybenzaldehyde, vanillin, syringaldehyde, trans-coniferylaldehyde, sinapaldehyde, and coixol. Two of them, trans-coniferylaldehyde and sinapaldehyde, exhibit relatively potent scavenging of DPPH radicals, inhibit TPA stimulated superoxide anion generation in neutrophil-like leukocytes, and induce Nrf2/ARE-driven luciferase activity in HSC-3 cells. Moreover, trans-coniferylaldehyde possesses cytoprotective efficacy against tert-butyl hydroperoxide-induced DNA double-strand breaks in cultured cells, and the chemopreventive potency induced by trans-coniferylaldehyde may be through the activation of kinase signals, including p38, ERK1/2, JNK, MEK1/2, and MSK1/2. In summary, we first identified six antimutagenic constituents from adlay hull. Among them, trans-coniferylaldehyde would be a highly promising agent for cancer chemoprevention and merits further investigation. 相似文献
59.
Wang ZW Lai CB Chang CH Chiang CJ Chao YP 《Journal of agricultural and food chemistry》2011,59(12):6534-6542
The L-arabinose (Ara)-controlled T7 expression system was previously constructed by creation of an Escherichia coli BL21(BAD) strain. The production of recombinant proteins in this strain was stringently regulated and reached a high level upon induction with Ara. Nevertheless, this system is still associated with inherent problems of interference with glucose and of the all-or-nothing induction profile at a subsaturating level of Ara. In this study, these problems were circumvented by modifying the physiological traits of BL21(BAD) strain. This was followed by deletion of ptsG gene and the araFGH and araBAD operon. The former encodes the glucose transporter while the latter two gene operons produce proteins responsible for Ara uptake and catabolism. In addition, the expression of genomic araE (encodes the Ara transporter) was constitutively enhanced. The resulting strain was designated BAD-5. By expression of the faster degrader GFP(LAA) at a subsaturating level of Ara, 80% of BAD-5 strain was found visually bright in the presence or absence of glucose. A further analysis by flow cytometry showed a uniform distribution of GFP expression for BAD-5 strain. In marked contrast, BL21(BAD) strain exhibiting visual brightness was less than 10% of the cell population and remained dark in the presence of glucose. Moreover, a saturated level of luciferase from Renilla reniformis (Rluc) could be readily obtained in BAD-5 strain at 20 μM Ara regardless of glucose. Rluc in BL21(BAD) strain was produced in an Ara dose-dependent manner, and the protein production became arrested when glucose was present. Overall, it illustrates the usefulness of the improved system for overproduction of recombinant proteins in an efficient, homogeneous, and glucose-insensitive way. 相似文献
60.
Lee TT Huang YF Chiang CC Chung TK Chiou PW Yu B 《Journal of agricultural and food chemistry》2011,59(13):7353-7359
The main objective of this research was to study the characteristics of starch granules and their influences on in vitro and pig prececal starch digestion of corn, dehulled barley, wheat, and potato. Scanning electron microscopy was used to study the starch endosperm structure in the parent material as well as in vitro starch digestion. The results showed that corn starch granules were polyhedral, with a diameter ranging from 2 to 10 μm, whereas those of dehulled barley and wheat were spherical, with a diameter ranging from 5 to 20 μm. Potato had the largest starch granules among starch sources reported herein, with oval spheres of 10-50 μm in diameter. In vitro starch hydrolysis showed that starch granules of corn degraded faster than the starch of dehulled barley and wheat, with the potato starch being degraded the slowest. The in vivo digestibility trial using ileal-cannulated pigs confirmed the starch degradation of grains. The in vitro (x, %) and in vivo (y, %) digestibility were highly correlated [y = 6.5304x - 538.48 (R(2) = 0.9924)]. On the basis of the results, in vitro starch hydrolysis might be useful in predicting in vivo prececal starch digestibility. The digestion kinetic characteristics of different starch sources might be employed to evaluate the starch digestive rate at the pig ileum. 相似文献