全文获取类型
收费全文 | 509篇 |
免费 | 10篇 |
专业分类
林业 | 67篇 |
农学 | 10篇 |
基础科学 | 4篇 |
203篇 | |
综合类 | 83篇 |
农作物 | 21篇 |
水产渔业 | 15篇 |
畜牧兽医 | 79篇 |
园艺 | 12篇 |
植物保护 | 25篇 |
出版年
2024年 | 1篇 |
2023年 | 5篇 |
2022年 | 7篇 |
2021年 | 14篇 |
2020年 | 7篇 |
2019年 | 12篇 |
2018年 | 24篇 |
2017年 | 12篇 |
2016年 | 11篇 |
2015年 | 16篇 |
2014年 | 14篇 |
2013年 | 25篇 |
2012年 | 40篇 |
2011年 | 35篇 |
2010年 | 26篇 |
2009年 | 19篇 |
2008年 | 43篇 |
2007年 | 24篇 |
2006年 | 28篇 |
2005年 | 30篇 |
2004年 | 25篇 |
2003年 | 24篇 |
2002年 | 30篇 |
2001年 | 9篇 |
2000年 | 3篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1994年 | 2篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1984年 | 1篇 |
1978年 | 2篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有519条查询结果,搜索用时 0 毫秒
101.
Michael Rodgers Mark O’Connor Mark Gerard Healy Connie O’Driscoll Zaki-ul-Zaman Asam Mika Nieminen Russell Poole Markus Müller Liwen Xiao 《Forest Ecology and Management》2010
The aim of this study was to investigate the release of phosphorus (P) to receiving waters resulting from harvesting 34-year-old lodgepole pine trees in an upland peat catchment. The study site was within a 25.3-hectare (ha) area, and was drained by a stream that received flows from ploughed furrows, mainly, via collector drains, and discharged directly to the salmonid Shrahrevagh River, Burrishoole, Co. Mayo, Ireland. The study site was divided into two parts: the upstream part was left intact and the downstream part was harvested in early Autumn 2005 following implementation of forest guidelines. Good management practices such as proper use of brash mats and harvesting only in dry weather were implemented. Two instrumented stations were established – one just upstream (US) and the other just downstream (DS) of the clearfelled area. The measurement of P concentrations at the two stations commenced in May 2005, two months before the harvesting started. The daily mean P concentration at the DS station increased from about 6 μg L−1 of total reactive phosphorus (TRP) during pre-clearfelling to 429 μg L−1 in August 2006. By October 2009, four years after clearfelling, the P concentrations at the DS station had returned to pre-clearfelling levels. In the first three years after harvesting, up to 5.15 kg ha−1 of TRP was released from the harvested catchment to the receiving water; in the second year alone, 2.3 kg ha−1 of TRP was released. Linear regression can be used to describe the relationship between TRP load and water discharge. About 80% of the total phosphorus (TP) in the study stream was soluble and more than 70% of the P release occurred in storm events, indicating that traditional buffer strips with widths of 15–20 m might not be efficient for P immobilization. The P concentrations were affected by antecedent weather conditions and highest concentrations occurred during storm events following prolonged drought periods. The water extractable phosphorus (WEP) contents in the soil were significantly higher below windrow/brash material than in brash-free areas, and whole-tree harvesting should be studied as one of the means to decrease P export from blanket peats. 相似文献
102.
103.
Mayer F Haase I Graubner A Heising F Paschke-Kratzin A Fischer M 《Journal of agricultural and food chemistry》2012,60(6):1350-1357
Partial sequencing of the γ-gliadin gene of 62 spelt and 14 soft wheat cultivars was performed. Fifty-six of the 62 spelt cultivars and 13 of the 14 soft wheat cultivars were shown to exhibit the typical spelt or soft wheat γ-gliadin sequence, respectively. Exceptions were ascribed to crossbreeding of soft wheat and spelt. Using the typical soft wheat γ-gliadin sequence, two alternative DNA-based analytical methods were developed for the detection and quantification of spelt flour "adulteration" with soft wheat. A simple and fast detection of soft wheat in spelt flours could be achieved by restriction fragment length (RFLP) analysis. In combination with lab-on-a-chip capillary gel electrophoresis (LOC-CE) the soft wheat proportion could be estimated. Heteroduplex formation served as additional confirmation for the presence of spelt besides soft wheat. Hence, RFLP-LOC-CE constitutes a perfect analysis tool for the quality control of cereal seeds and pure cultivars. A precise quantification of soft wheat "adulterations" in spelt flour down to 1% could be achieved by the developed real-time PCR method. The calibration parameters of the real-time PCR assay fulfilled the minimum performance requirements of the European Network of GMO (genetically modified organisms) Laboratories (ENGL). 相似文献
104.
The differentiation of nonrefined (e.g., cold-pressed) and refined edible oils is an important task in food control because of the higher commercial value of the former. Here, we explored the suitability of the relative abundance of cis-phytol as a marker for authentication of nonrefined edible oils. Phytol, the tetramethyl-branched, monoenoic alcohol, is found widespread in nature as a part of chlorophyll. In chlorophyll, only trans-phytol is found. In this study, we present a method for the analysis of the phytol isomers, considering that traces of cis-phytol (contributing 0.1% to the phytol content) can be determined next to trans-phytol. For this purpose, phytol was gathered with the unsaponifiable matter from the oil, trimethylsilylated, and analyzed by gas chromatography coupled to mass spectrometry. With this method, 27 samples of edible oils (16 refined and 11 nonrefined edible oils) were analyzed for the abundance of cis-phytol relative to trans-phytol. In the nonrefined oils (e.g., olive oil, rapeseed oil, maize oil, and sunflower oil), cis-phytol contributed 0.1% (n = 3) or less (n = 8) to the phytol content. In contrast, the refined olive oils (n = 4) contained a share of 1.3-3% cis-phytol; the refined rapeseed oil (n = 3) contained a share of 0.7-1.0% cis-phytol; and the refined sunflower oil (n = 4) contained a share of 0.3-0.9% cis-phytol. Only one refined pomegranate kernel did not contain cis-phytol. The phytol concentration was not suited to distinguish nonrefined from refined oils. In contrast, our data suggest that the virtual absence of cis-phytol can be used as a marker for nonrefined (e.g., cold-pressed) edible oils. 相似文献
105.
Catrina Cofalla Sebastian Hudjetz Sebastian Roger Markus Brinkmann Roy Frings Jan W?lz Burkhard Schmidt Andreas Sch?ffer Ulrike Kammann Markus Hecker Henner Hollert Holger Schüttrumpf 《Journal of Soils and Sediments》2012,12(3):429-442
Purpose
Flood events are expected to increase both in intensity and frequency due to climate change in the near future. From an environmental toxicology perspective, there is concern that such flood events could lead to the remobilization of contaminated sediment layers in rivers. The aim of this pilot study was to establish a novel and interdisciplinary framework combining methods of hydrodynamic engineering and ecotoxicological assessment to enable investigation of the potential risks associated with such remobilization events.Materials and methods
Formulated sediment was prepared according to OECD guideline 218 and spiked with a mixture of four polycyclic aromatic hydrocarbons (phenanthrene, chrysene, pyrene, benzo[a]pyrene) at concentrations of 3.3?C8.3?mg?kg?1 dry weight. Rainbow trout (Oncorhynchus mykiss) were exposed as test animals to re-suspended sediments in three out of five experiments. The experiments were carried out in an annular flume designed to investigate transport behaviour of fine-grained sediments. Several physicochemical (e.g. pH) and sedimentological (e.g. turbidity) parameters were measured to characterise environmental conditions and erosion behaviour of sediments. Furthermore, exposure concentrations were measured by means of an in vitro assay (7-ethoxyresorufin-o-deethylase (EROD), RTL-W1 cell assay) and chemical analysis.Results and discussion
Preparation and spiking of large amounts of formulated sediments were feasible but not practical. Successful spiking could be confirmed by the bioanalytical methods with the spiked sediments showing significantly elevated EROD induction compared to control sediments. Conditions within the annular flume remained stable throughout all experiments and were adequate to support rainbow trout. Flood events were successfully simulated, resulting in re-suspension of formulated sediment. Different erosion behaviours of sediments during the simulated flood events were observed and could be associated with changes in microbial composition of sediments due to differences in storage conditions. Therefore, maintaining constant storage conditions of formulated sediments is crucial to enable consistency and comparability among erosion experiments.Conclusions
This study clearly demonstrated the feasibility of a combined hydro-toxicological approach in support of the investigation of the potential ecotoxicological relevance of sediment re-suspension events. However, based on the results presented here, it is recommended to include additional physicochemical parameters, such as redox potential and conductivity, and to extend the experimental setup to natural sediments and different aquatic organisms. Future studies will use natural sediments containing representative microbial communities and extracellular polymeric substances to enable extrapolation from the annular flume to conditions in natural flowing waters. 相似文献106.
Hanno Zielke Thomas-Benjamin Seiler Sabine Niebergall Erik Leist Markus Brinkmann Denise Spira Georg Streck Werner Brack Ute Feiler Thomas Braunbeck Henner Hollert 《Journal of Soils and Sediments》2011,11(2):352-363
Purpose
Traditionally, methods for sediment extractions are characterised using chemical analyses. However, in order to evaluate sediment extracts with regard to biological effects and, thus, bioaccessibility, extraction methods have to be compared to effect data obtained from experiments with in situ exposure scenarios, i.e., sediment contact tests. This study compares four extraction methods and sediment contact test data from a previous project with respect to predictive power in the fish embryo test with zebrafish (Danio rerio).Materials and methods
A natural and an artificial sediment spiked with a mixture of six organic pollutants (2,4-dinitrophenol, diuron, fluoranthene, nonylphenol, parathion and pentachlorophenol) were extracted using (a) membrane dialysis extraction (MDE), (b) a Soxhlet procedure, (c) hydroxypropyl-??-cyclodextrin (HPCD) or (d) Tenax®-TA. Whereas the former two are regarded being exhaustive with respect to non-covalently bound contaminants, the latter two are considered to predict bioaccessibility. Resulting extracts were tested in the fish embryo assay with D. rerio for embryotoxic and teratogenic potential.Results and discussion
Mortalities caused by organic extracts from Soxhlet extraction and MDE were high. However, HPCD extracts turned out to be at least as effective as extracts obtained with these two methods. One possible reason might be short ageing time of the spiked sediments. Only Tenax®-TA extracts gave results comparable to the sediment contact assay for natural sediment, but revealed low reproducibility. Significant differences between natural and artificial sediment were found for extracts obtained with techniques using native (i.e., non-freeze-dried) sediments, i.e., HPCD and Tenax®-TA. In contrast, MDE and Soxhlet extracts used freeze-dried sediment and did not differentiate between natural and artificial sediment. Therefore, freeze-drying has likely altered and equalised sediment properties that influence accessibility, such as composition of bacterial communities and organic matter quality.Conclusions
Four extraction methods were successfully characterised with respect to their stringency and predictiveness for bioaccessibility. MDE was confirmed as an alternative to Soxhlet extraction. High mortalities induced by HPCD extracts underline the need to include ageing into consideration when assessing sediments. Although Tenax®-TA may basically be used to predict bioaccessibility in the fish embryo test, the high variability observed warrants further investigation of the relation between effect and extractability. Apparently, freeze-drying can severely affect sediment properties, potentially eliminating individual properties of natural sediments. 相似文献107.
Rombouts I Lagrain B Brunnbauer M Koehler P Brijs K Delcour JA 《Journal of agricultural and food chemistry》2011,59(4):1236-1243
Results in this paper confirm heat-induced isopeptide bond formation in wheat gluten. Heating (24 h, 130 °C) of wheat gluten [moisture content 7.4%] decreased its extractability in sodium dodecyl sulfate containing buffer (pH 6.8), even after reduction of disulfide (SS) bonds. Thus, both SS bonds and non-SS bonds were responsible for the extractability loss. Cross-links of the lysinoalanine and lanthionine type were not present in the heated samples, but heat treatment reduced levels of available amino groups. Heating of purified and alkylated high molecular weight glutenin subunits (HMW-GS) under similar conditions also resulted in extractability loss, demonstrating that cross-linking did not solely depend on the availability of cysteine or cystine. These observations indicated that heat treatment had induced isopeptide bond formation, resulting in larger and unextractable molecules. Heating HMW-GS lysine- and glutamine-containing peptides induced the formation of isopeptide bonds, thereby supporting the above hypothesis. The level of isopeptide bond formation increased with heating time. 相似文献
108.
文章通过计算各种蛋氨酸源的影子价格并进行比较,探讨其在实际配方中的应用。以现有肉鸡日粮推荐为基础配制了288个试验日粮,DL-methionine为标准添加蛋氨酸,计算蛋氨酸类似物的影子价格。结果表明:液体蛋氨酸羟基类似物(MHA-FA)的影子价格受多种因素的影响,如果想要替代产品具有竞争力的话,应在假定生物学效价计算出的价格上减去大约5.6%。 相似文献
109.
110.
Maria Orfanoudaki Anja Hartmann Julia Mayr Flix L. Figueroa Julia Vega John West Ricardo Bermejo Christine Maggs Markus Ganzera 《Marine drugs》2021,19(6)
This study presents the validation of a high-performance liquid chromatography diode array detector (HPLC-DAD) method for the determination of different mycosporine-like amino acids (MAAs) in the red alga Bostrychia scorpioides. The investigated MAAs, named bostrychines, have only been found in this specific species so far. The developed HPLC-DAD method was successfully applied for the quantification of the major MAAs in Bostrychia scorpioides extracts, collected from four different countries in Europe showing only minor differences between the investigated samples. In the past, several Bostrychia spp. have been reported to include cryptic species, and in some cases such as B. calliptera, B. simpliciuscula, and B. moritziana, the polyphyly was supported by differences in their MAA composition. The uniformity in the MAA composition of the investigated B. scorpioides samples is in agreement with the reported monophyly of this Bostrychia sp. 相似文献