全文获取类型
收费全文 | 720篇 |
免费 | 83篇 |
专业分类
林业 | 58篇 |
农学 | 35篇 |
基础科学 | 2篇 |
137篇 | |
综合类 | 68篇 |
农作物 | 30篇 |
水产渔业 | 70篇 |
畜牧兽医 | 334篇 |
园艺 | 13篇 |
植物保护 | 56篇 |
出版年
2024年 | 2篇 |
2023年 | 5篇 |
2022年 | 7篇 |
2021年 | 28篇 |
2020年 | 32篇 |
2019年 | 50篇 |
2018年 | 28篇 |
2017年 | 24篇 |
2016年 | 39篇 |
2015年 | 35篇 |
2014年 | 32篇 |
2013年 | 37篇 |
2012年 | 61篇 |
2011年 | 65篇 |
2010年 | 32篇 |
2009年 | 22篇 |
2008年 | 33篇 |
2007年 | 45篇 |
2006年 | 34篇 |
2005年 | 37篇 |
2004年 | 31篇 |
2003年 | 33篇 |
2002年 | 30篇 |
2001年 | 4篇 |
2000年 | 9篇 |
1998年 | 2篇 |
1997年 | 7篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1965年 | 1篇 |
1962年 | 1篇 |
1955年 | 1篇 |
1941年 | 1篇 |
1937年 | 1篇 |
1936年 | 1篇 |
1933年 | 1篇 |
1931年 | 1篇 |
排序方式: 共有803条查询结果,搜索用时 15 毫秒
41.
Segurel MA Razungles AJ Riou C Trigueiro MG Baumes RL 《Journal of agricultural and food chemistry》2005,53(7):2637-2645
The origin of dimethyl sulfide (DMS) produced during wine aging was examined through different assays. The production of DMS during the model aging of a wine and the concomitant decrease of residual potential DMS (PDMS), as DMS released by heat-alkaline treatment in 0.5 M sodium hydroxide at 100 degrees C for 1 h, were demonstrated. Then, dimethyl sulfoxide (DMSO), methionine sulfoxide (MSO), S-methylmethionine (SMM), and dimethylsulfonium propanoic acid (DMSPA), reported previously as possible DMS precursors, were investigated for their ability to be DMS precursors in wine in the conditions of this model aging and of the heat-alkaline treatment. The results showed that DMSO, MSO, and DMSPA could hardly be DMS precursors in the conditions used, whereas SMM appeared to be a good candidate. Finally, the use of [(2)H(6)]-DMSPA as an internal standard for PDMS determination was proposed, because it provided better reproducibility than [(2)H(6)]-DMS used as an external standard. 相似文献
42.
Marie?DavidianEmail author David?M.?Giltinan 《Journal of Agricultural, Biological & Environmental Statistics》2003,8(4):387-419
Nonlinear mixed effects models for data in the form of continuous, repeated measurements on each of a number of individuals, also known as hierarchical nonlinear models, are a popular platform for analysis when interest focuses on individual-specific characteristics. This framework first enjoyed widespread attention within the statistical research community in the late 1980s, and the 1990s saw vigorous development of new methodological and computational techniques for these models, the emergence of general-purpose software, and broad application of the models in numerous substantive fields. This article presentsan overview of the formulation, interpretation, and implementation of nonlinear mixed effects models and surveys recent advances and applications. 相似文献
43.
Changes in fruit antioxidant activity among blueberry cultivars during cold-temperature storage 总被引:10,自引:0,他引:10
Connor AM Luby JJ Hancock JF Berkheimer S Hanson EJ 《Journal of agricultural and food chemistry》2002,50(4):893-898
Antioxidant activity, total phenolic content, anthocyanin content, and six other fruit characters including titratable acid concentration, soluble solids, firmness, and percentage of bruised berries were determined for nine blueberry (Vaccinium L. sp.) cultivars at harvest and at various postharvest intervals after storage at 5 degrees C. Berries from MSU-58, Brigitta, and Legacy stored successfully for 7 weeks, Bluegold stored for 3-5 weeks, Bluecrop, Elliott, and Nelson stored for 3 weeks, and Jersey and Little Giant stored for fewer than 3 weeks. During the time they retained marketable quality, one cultivar (MSU-58) demonstrated a 29% increase in antioxidant activity. None of the cultivars showed a significant decrease from the harvest antioxidant activity value during storage. Antioxidant activity, total phenolic content, and anthocyanin content were strongly correlated with each other (r = 0.87-0.99, P < 0.01). All three parameters were moderately correlated with soluble solids (r = 0.47, P < or =0.05; r = 0.44, P < or = 0.05; and r = 0.64, P < or = 0.01, respectively), and antioxidant activity and total phenolic content were both moderately correlated with pH (r = 0.53 and 0.49, respectively; P < or = 0.05). However, antioxidant activity, total phenolic content, and anthocyanin content showed no correlation with firmness, percent severely bruised berries, or weight loss. Antioxidant activity and total phenolic content at harvest both correlated with titratable acidity at harvest (r = 0.68, P < or = 0.05 and r = 0.70, P < or = 0.05, respectively) on a cultivar mean basis. Berries from Elliott were also harvested from plants at two levels of bush ripeness (30-50% and 60-80% ripe berries on plants) and separated into three fruit maturity classes on the basis of percent blue color. The level of bush ripeness had no significant effect on antioxidant activity, total phenolic content, or anthocyanin content; however, fruit maturity had a significant effect on antioxidant activity, total phenolic content, and anthocyanin content, and bush ripeness x fruit maturity interactions were significant for these three traits. Berries with 50-75% blue coloration harvested from bushes with 60-80% mature fruit showed a significant increase in antioxidant activity, total phenolic content, and anthocyanin content during the first 3 weeks in storage. Our results demonstrate that increases in antioxidant activity, total phenolic content, and anthocyanin content may occur in the blueberry during cold storage and are cultivar-dependent. The increases that occur in immature fruit, such as in Elliott, may be advantageous for producers who wish to delay marketing of the fruit. 相似文献
44.
Beow?Yong?YeapEmail author Paul?J.?Catalano Louise?M.?Ryan Marie?Davidian 《Journal of Agricultural, Biological & Environmental Statistics》2003,8(4):438-454
A robust two-stage approach is used to reanalyze the repeated measurements from an experiment of airway responsiveness in
rats randomized to long-term exposure at four ozone doses. The concentration-response data generated for each rat may be represented
as a hierarchical nonlinear model encompasing the sources of variation within and between individual profile for each rat,
the conditional modeling approach can assess the adequacy of an assumed mean model, a fundamental advantage not intrinsic
to marginal techniques. The two-stage population inference is based on the estimated individual parameters, thus maintaining
an intuitive appeal to the toxicologists who traditionally have fitted a separate curve for each animal and then applied ANOVA
to the summary statistics. However, we formally adjust the standard errors for the extra variability due to the initial estimation
of the individual parameters and also allow for their within-rat correlation. The robust two-stage method appropriately down
weights the a berrant responses arising sporadically within individualsand, more importantly, the rats which may be outlying
relative to the usual population variation. The true effect of chronic ozone exposure, including a significant gender interaction,
may be masked by a few rats which exert undue influence on the population estimates in a nonrobust analysis. 相似文献
45.
Michael Dreyer Merle Wichmann Marie Rischen Bruno M. Görlach Annika Ehmke Britta Pitann Karl H. Mühling 《植物养料与土壤学杂志》2020,183(3):389-396
Background : Manganese deficiency often becomes a yield limiting factor, particularly on calcareous soils, even though the total soil manganese content is usually sufficient. Although it is known that acidifying N fertilizers can improve Mn availability, the reason of this effect is still unknown. Aim : Our aim was to investigate the effect of stabilized ammonium fertilizers as a tool to distinguish between physiological‐ and nitrification‐induced acidification. Method : Two pot experiments with Triticum aestivum L. and one soil incubation experiment using different nitrogen forms (CN = calcium nitrate, AN = ammonium nitrate, AS = ammonium sulfate, ATS = ammonium thiosulfate) with and without addition of nitrification inhibitors (DCD, Nitrapyrin, Piadin, DMPP) were conducted to examine the effect on Mn availability in the soil and Mn uptake by the plants at different development stages (EC 31 und 39). Results : With increasing fertilizer content a higher Mn concentration was detected: CN: 32 µg Mn g?1 DM, AN: 39 µg Mn g?1 DW, AS: 55 µg Mn g?1 DM, ATS: 109 µg Mn g?1 DM. The addition of a nitrification inhibitor resulted in a significantly lower rhizosphere pH compared to the non‐stabilized fertilizer. Surprisingly, the use of different nitrification inhibitors led to unchanged (CN, AN) or lower Mn concentrations of wheat. Especially in the treatments (AS and ATS), this negative effect was very evident (AS+DCD: 42 µg Mn g?1 DM; ATS+DCD: 55 µg Mn g?1 DM). Conclusions : Mn availability was enhanced by ongoing nitrification process rather than physiological acidification. Compared to other N forms, ammonium thiosulfate led to the highest Mn availability in bulk soil. 相似文献
46.
Polyphenols, widely spread in our diet by the consumption of plant food products, are commonly determined using Folin-Ciocalteu reagent that interacts with other different reducing nonphenolic substances and leads to an overestimation of polyphenol content. In this paper we report an optimized Folin-Ciocalteu method to specifically determine the contents of total polyphenols and vitamin C. After the optimal conditions for the colorimetric assay were set, solid-phase extraction (Oasis HLB (hydrophilic-lipophilic balance)) was carried out to eliminate the water-soluble reducing interferences including vitamin C. Colorimetric correction was thus performed by subtracting interfering substances contained in the water washing extract from the raw extract. Moreover, vitamin C present in the water washing extract can be destroyed by heating and thus colorimetrically deduced. This procedure was set up with synthetic solutions and validated on different extracts from fruit products. 相似文献
47.
Klejdus B Mikelová R Petrlová J Potesil D Adam V Stiborová M Hodek P Vacek J Kizek R Kubán V 《Journal of agricultural and food chemistry》2005,53(15):5848-5852
An ultrafast HPLC/UV-vis DAD method working at 254 nm was applied for the determination of isoflavone aglycons and glycosides (genistin, genistein, daidzein, daidzin, glycitin, glycitein, ononin, formononetin, sissotrin, and biochanin A) in roots, stems, leaves, and soy pods of soy plants and in soybeans of five varieties (Korada, Quito, Rita, OAC Erin, and OAC Vison). An Atlantis dC18 ultrafast RP chromatographic column (20 mm x 2.1 mm, 3 microm particle size) was applied for separation of the isoflavone aglycons and glycosides. A flow rate of the mobile phase (0.1% (v/v) acetic acid, pH 3.75-solvent A and methanol-solvent B) was 0.35 mL min(-1), and the column temperature was 36 degrees C. A linear gradient profile from 13 up to 22% B (v/v) from zero to 2.5 min, up to 30% B to 3.21 min, up to 35% B to 4 min, up to 40% B to 4.5 min, up to 50% B to 5.14 min, and followed by negative gradient up to 13% B to 7.71 min was used. The absolute limits of detection per sample injection (5 microL) were the highest for biochanin A (166.2 fmol) and the lowest for genistin (17.0 fmol), respectively. An accelerated solvent extraction (ASE) in combination with sonication was applied for isolation of biologically active compounds. A solid-phase extraction procedure was used to purify the extracts in the case of analysis of soy plants parts. The recoveries of 96-106% were obtained for the different concentrations of the isoflavone aglycons and glycosides and the different matrixes (overall RSDs 2-9%). The highest isoflavone concentrations were found in roots (12.5 microg g(-1) dry weight), while the amounts were about 3-1100 microg g(-1) fresh weight in different varieties of soybeans. 相似文献
48.
Strålsjö L Alklint C Olsson ME Sjöholm I 《Journal of agricultural and food chemistry》2003,51(15):4291-4295
Folate concentrations in rosehips and commercial rosehip products and factors affecting folate retention during drying were investigated. On the basis of the raw material studied during 3 years, rosehips were shown to be a rich folate source, 400-600 microg/100 g based on dry matter and 160-185 microg/100 g based on the fresh weight (edible part). Rosehips are not often consumed fresh; therefore, drying to produce stable semimanufactures is a crucial step. The degradation of folate was shown to be dependent on the drying time until the water activity was below 0.75. The required drying time was reduced by cutting the rosehips in slices and to some extent also by increasing the temperature. Retention of folate and ascorbic acid was affected by the same factors, and high content of ascorbic acid could provide a possible protection for folate degradation. 相似文献
49.
Masotti V Juteau F Bessière JM Viano J 《Journal of agricultural and food chemistry》2003,51(24):7115-7121
The volatile components of the aerial parts of Artemisia molinieri, an endemic wormwood of southern France, were analyzed by GC and GC-MS. Among the 69 compounds identified, major components were ascaridole (19-76%), alpha-terpinene (traces-36%), p-cymene (1-17%), 1,8-cineole (0.3-8%), and germacrene D (0.6-15%). Quantitative variations have been characterized following the season, the phenological cycle, and the aging of the plants. Bioassays have been performed on a sample of essential oil, which has shown a strong inhibition of the growth of both tested yeasts (Candida albicans and Saccharomyces cerevisiae var. chevalieri) and minor activity on both tested Gram-negative bacteria (Escherichia coli and Enterococcus hirae). The oils have shown interesting antioxidant activities on the basis of alpha-tocopherol as reference compound, up to 400-1200%. 相似文献
50.
Wengelnik K Vidal V Ancelin ML Cathiard AM Morgat JL Kocken CH Calas M Herrera S Thomas AW Vial HJ 《Science (New York, N.Y.)》2002,295(5558):1311-1314
During asexual development within erythrocytes, malaria parasites synthesize considerable amounts of membrane. This activity provides an attractive target for chemotherapy because it is absent from mature erythrocytes. We found that compounds that inhibit phosphatidylcholine biosynthesis de novo from choline were potent antimalarial drugs. The lead compound, G25, potently inhibited in vitro growth of the human malaria parasites Plasmodium falciparum and P. vivax and was 1000-fold less toxic to mammalian cell lines. A radioactive derivative specifically accumulated in infected erythrocytes to levels several hundredfold higher than in the surrounding medium, and very low dose G25 therapy completely cured monkeys infected with P. falciparum and P. cynomolgi. 相似文献