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排序方式: 共有124条查询结果,搜索用时 15 毫秒
51.
Toebes AH de Boer V Verkleij JA Lingeman H Ernst WH 《Journal of agricultural and food chemistry》2005,53(12):4660-4666
Extraction of isoflavone malonylglucosides from red clover (Trifolium pratense L.) is a complicated procedure. This is due to the relatively unstable character of the thermolabile glucoside malonates as well as by action of native beta-glucosidases, resulting in a rapid degradation of malonylated glucosides into their corresponding aglucones. In this study, Tris was identified as a suitable beta-glucosidase inhibitor in red clover extracts, optimized at 350 mM Tris in 80% ethanol at pH 7.2. Extraction of fresh red clover leaves using Tris increased the concentration of malonate conjugated isoflavones approximately 13 to 24 times as opposed to extraction without Tris. A comparison of isoflavone profiles obtained after extraction with and without Tris of different plant organs of red clover and several species within the family Fabaceae suggests that the amount and/or activity of the degenerative beta-glucosidase enzymes vary for the different plant parts of red clover and among the species studied. Therefore, the use of standard extraction methods may well result in overestimation of the concentration of aglucones and consequently underestimation of the malonylglucoside isoflavones concentration depending on the plant species and plant part studied. 相似文献
52.
The formation of 4-hydroxy-2,5-dimethyl-3(2H)-furanone (HDMF) by Zygosaccharomyces rouxii was studied in yeast-peptone-dextrose medium containing d-fructose 1,6-diphosphate under various culture conditions. Cell growth and HDMF production was heavily dependent on medium pH and sodium chloride concentration. Higher pH values of the nutrient medium had a positive effect on HDMF formation but retarded cell growth resulting in an optimal pH value of 5.1 with regard to the yield of HDMF. Salt stress stimulated HDMF formation by Z. rouxii as increasing sodium chloride concentration led to higher amounts of HDMF. The HDMF concentration in the culture supernatant and HDMF formation per yeast cell peaked at 20% sodium chloride in the nutrient medium. The nonutilizable carbohydrate d-xylose displayed a weak effect on HDMF formation, and the addition of glycerol to salt-stressed cells had no effect on the production of HDMF. 相似文献
53.
54.
Dou Yue Cosentino Francesca Malek Ziga Maiorano Luigi Thuiller Wilfried Verburg Peter H. 《Landscape Ecology》2021,36(8):2215-2234
Landscape Ecology - While land use change is the main driver of biodiversity loss, most biodiversity assessments either ignore it or use a simple land cover representation. Land cover... 相似文献
55.
Calibration of the simulation model “Ceres Wheat” under conditions of soils with shallow watertable and temperate climate. Part 1: Limitations in the applicability of the original model and necessary modifications To apply the yield simulation model “Ceres Wheat” under the specific climate conditions of Schleswig Holstein, the following modifications were necessary:
- Wheat development is strongly influenced by climatic conditions. Therefore the model has been adjusted to the temperate climate of Schleswig Holstein.
- The soil water balance routine of the model was originally designed for soils without oxygen deficiencies due to water logging. Routines for shallow water tables and artificial drainage were formulated.
- Due to modifications of the soil water balance routine, the associated nitrogen routine, especially the leaching of nitrate, has been changed.
- The simulation of yield depressions due to excessive water required the introduction of a trafficability delay function and an additional reduction factor for crop development.
56.
The biotransformation of a series of aliphatic aldehydes (C(8)-C(12)) by Bacillus megaterium isolated from strawberry leaf surfaces was investigated. Products were isolated by liquid/liquid extraction and analyzed by gas chromatography (GC) combined with mass spectrometry (MS). In addition to aliphatic alcohols and the remaining aldehydes, major transformation products included the corresponding acids as well as 2,3-dialkylacroleins, dehydrated aldol addition products, which were detected for the first time as biotransformation products. To verify the structures, 2,3-dialkylacroleins were chemically synthesized from the appropriate aldehydes by base-catalyzed aldol condensation reactions and characterized by (1)H and (13)C NMR spectroscopy. Time-course studies showed that the maximum yield of the acrolein derivatives was obtained after 6 days of incubation. 相似文献
57.
Influence of long-term slurry application on soil nutrients. 2. Fractions and solubility criteria of soil phosphorus Fractions and solubility criteria of soil phosphorus accumulated by long-term slurry application were investigated. The following results were obtained:
- – Slurry application mainly resulted in higher concents of inorganic phosphorus, especially Fe-Al-P, even in deeper soil layers.
- – The accumulation of inorganic phosphorus resulted in an increase of phosphorus availability in all conventional extraction methods used, as well as in higher phosphorus concentration of the soil solution.
- – In the upper soil layers of luvisols and in the deeper soil layers of diluvial sandy soils organic phosphorus was enriched, but did not significantly influence phosphorus intensity and delivery.
- – Compared to soils supplied with mineral fertilizers there are no particularities in phosphorus dynamics, from which differences in the interpretation of “available” phosphorus values with respect to phosphorus recommendation scales could be concluded.
58.
Preparation and use of 33P labelled carbonate fluorapatite in studies on the effect of phosphate rock containing fertilizers For a precise evaluation of the effectiveness of the different phosphate fractions in partially acidulated phosphate rocks these fractions were alternatively labelled. For this purpose a technique was developed to prepare synthetic, 33P labelled carbonate fluorapatite (francolite type). A labelled (NH4)2HPO4 solution (+ Na2CO3, NH4F) was poured into a Ca(NO3)2 × 4H2O solution (pH 12) and the washed precipitate heated until the aimed solubility was reached (e.g. 2 h 400°C + 1.5 h 600°C). After grinding this mother phosphate rock was acidulated with sulphuric acid to fully acidulated superphosphate and partially acidulated phosphate rock. The nonacidulated rock residue was extracted from the partially acidulated phosphate rock. In an identical procedure phosphate rock was prepared without addition of 33P and in part acidulated to superphosphate. Mixing of labelled phosphate rock and not labelled superphosphate (and vice versa) gave two fertilizer mixtures with alternate labelled fractions equivalent to the fully labelled partially acidulated phosphate rock. Mineralogical properties of the synthetic phosphate fertilizers and their turnover in pot experiments with rye grass were corresponding to that of commercial products. The reactivity of the nonacidulated rock residue was inferior to that of the original phosphate rock after the process of partial acidulation. Fertilizer utilization was determined by use of isotopes (33P) and total P uptake method. P utilization as determined by total P uptake method was significantly higher compared to the real fertilizer effectiveness measured by 33P labelling. 相似文献
59.
Heini Kujala Miguel B. Araújo Wilfried Thuiller Mar Cabeza 《Biological conservation》2011,(10):2450-2458
Gap analysis is a widely used method for assessing the representation of species in protected area (PA) networks. However, representation does not imply persistence. Here, we investigated whether gap analysis may result in misleading conservation guidelines by comparing the representation to two indicators of persistence. We ran a gap analysis with Finnish breeding birds and identified conservation priorities based on current distribution patterns. We tested the sensitivity of these results by using two target setting schemes and several thresholds defining the amount of protected area, and found the levels of representation identified by gap analysis to be robust. We then compared the gap analysis results with recent population trends and projected changes in potential suitable climate under different climate change scenarios for the year 2050. We show that although high latitude species are well represented in PAs, they are currently declining and are projected to lose climatic suitability in the near future. In contrast, low latitude species with poor representation in PAs have increasing population trends and are generally expected to expand their ranges into protected areas in the near future. This study demonstrates with empirical data a mismatch between representation in PAs and population trends, resulting in misleading understanding of current PA effectiveness. The mismatch is linked to the latitude of species distributions and corresponds to expected future changes, indicating that the patterns are potentially driven by climate change. We therefore urge practitioners and researchers to include better indicators of persistence in gap-analysis frameworks even for short term assessments. 相似文献
60.