首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   137篇
  免费   16篇
林业   15篇
农学   11篇
  34篇
综合类   3篇
农作物   14篇
水产渔业   12篇
畜牧兽医   37篇
园艺   4篇
植物保护   23篇
  2024年   2篇
  2023年   3篇
  2022年   3篇
  2021年   3篇
  2020年   2篇
  2019年   3篇
  2018年   6篇
  2017年   8篇
  2016年   14篇
  2015年   10篇
  2014年   3篇
  2013年   12篇
  2012年   3篇
  2011年   9篇
  2010年   9篇
  2009年   6篇
  2008年   5篇
  2007年   1篇
  2006年   6篇
  2005年   3篇
  2004年   6篇
  2003年   3篇
  2002年   5篇
  2001年   2篇
  2000年   2篇
  1999年   2篇
  1998年   1篇
  1996年   1篇
  1995年   2篇
  1993年   1篇
  1990年   1篇
  1989年   2篇
  1988年   1篇
  1987年   2篇
  1986年   1篇
  1984年   2篇
  1983年   4篇
  1982年   1篇
  1981年   1篇
  1977年   1篇
  1971年   1篇
排序方式: 共有153条查询结果,搜索用时 15 毫秒
131.
Zinc (Zn) toxicity to a marine fouling dreissinid bivalveMytilopsis sallei was investigated and the safe concentration of Zn was determined for this bivalve. In acute toxicity tests onM. sallei the 96 h LC50 value for Zn is found to be 8.364 mg 1?1. The results suggest that Zn has the lowest toxic effect onM. sallei when compared to copper and mercury. Effect of Zn on the oxygen consumption ofM. sallei was studied. Sub-lethal concentrations of Zn functioned as respiratory depressants. Accumulation of Zn was investigated in relation to exposure period and concentration inM. sallei. Zn accumulation was found to be sensitive to both concentration of Zn and exposure time. The effect of exposure time and concentration on body biochemical components was also studied inM. sallei. This accumulated Zn has resulted in impairment of carbohydrate metabolism and protein utilisation.  相似文献   
132.
The phyla Leguminosae contains protease inhibitors, lectins, chitinases, and glycohydrolases as major defense proteins in their seeds. Electrophoretic analysis of the seed proteins of tamarind ( Tamarindus indica L.), an agri-waste material, indicated the unusual presence of two major proteins comparable to overexpression of recombinant proteins. These proteins were identified by amino-terminal analysis to be (1) Kunitz-type trypsin inhibitor and (2) class III endochitinase (34000 Da). These two proteins were purified to apparent homogeneity by a single-step chitin bead affinity chromatography and characterized. The Kunitz inhibitor was specific toward inhibiting trypsin with a stoichiometry of 1:1. The 33000 +/- 1000 Da protein, accounting for >50% of the total seed protein, is an acidic glycoprotein exhibiting a very low endotype hydrolytic activity toward chitin derivatives. SDS-PAGE followed by densitometry of tamarind seed germination indicates the disappearance of the chitinase with the concomitant appearance of a cysteine endopeptidase. On the basis of its abundance, accumulation without any pathogenesis-related stimulus, temporal regulation, amino acid composition, and very low enzyme activity, this 34000 Da protein designated "tamarinin" physiologically serves as the major storage protein.  相似文献   
133.
134.
在印度西高止山脉(Western Ghats),通过粪便取样和直接观察两种方法,对全球濒危物种灰头林鸽(Columba elphinstonii)的觅食生态进行了研究.结果表明,灰头林鸽取食39种植物的果实、11种植物的种子、4种植物的花和叶芽,以及少量地面无脊椎动物.不同季节的直接观察结果显示,有9种植物的被取食频率较高(占观察总次数的47%),其中取食樟科植物果实的频次最高.灰头林鸽主要在树冠中上部(高于6米)外围的树枝上取食,全年中拾取行为占取食方法的76%.取食果实的频率与果实丰富度显著相关,而后者由降雨量决定.本研究表明,林鸽在不同森林资源条件下需要一个多样化的食物谱.保护这一物种需要保留其全年所需资源的所有栖息地类型.  相似文献   
135.
Pimobendan is a benzimidazole‐pyridazinone derivative, marketed as a racemic mixture for the management of canine heart failure. Pharmacokinetics of the enantiomers of pimobendan and its oral bioavailability have not been described in dogs. The aim of this study was to describe pharmacokinetics of three formulations of pimobendan in healthy dogs: the licensed capsule product, and novel liquid and intravenous formulations. A three‐period, nested randomized two‐treatment crossover design was used. Pimobendan was administered p.o. at 0.25 and i.v. at 0.125 mg/kg. Blood and plasma samples were analysed by liquid chromatography–mass spectrometry. Noncompartmental modelling was used to describe the pharmacokinetics. Parameters were compared between formulations using a general linear model. Bioequivalence of the oral formulations was tested using CI90 for AUC(0–∞) and Cmax. Bioavailability of pimobendan after oral dosing was 70%. Liquid and capsule formulations were bioequivalent only for AUC. The positive enantiomer of pimobendan (PE) had a larger volume of distribution than the negative enantiomer (NE) (281 ± 48 vs. 215 ± 68 mL/kg; P = 0.003) and a shorter half‐life (21.7 vs. 29.9 min; P = 0.004). The NE was distributed more quickly than the PE into blood cells. Enantiomers of pimobendan have differing absorption, distribution and elimination. The pharmacokinetics of pimobendan in healthy dogs was described.  相似文献   
136.
137.
Isoflavone levels and isoflavone chemical composition in 11 cultivars of soybean, including 4 Indian and 7 genotypes of soybean grown in Bulgaria, were analyzed as determined by C 18 reversed phase high-performance liquid chromatography coupled with a photodiode array detector. Antioxidant activity of soybean extracts was assessed using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, and total phenolic compounds (TPC) were determined by using Folin-Ciocalteu reagent. The range of total isoflavones (TI) was 558.2-1048.6 microg g (-1) of soy in Indian cultivars, and it was 627.9-1716.9 microg g (-1) of soy in the case of Bulgarian cultivars. The highest and lowest total isoflavone contents were observed for Maus-2 (1048.6 microg g (-1) of soy) and Hardee (558.2 microg g (-1) of soy), respectively, for the Indian cultivars, and they were observed for Boryara (1716.9 microg g (-1) of soy) and Line 5 (627.9 microg g (-1) of soy) for the Bulgarian genotypes. DPPH radical scavenging activity did not differ significantly among the cultivars and did not correlate with TI, whereas TPC correlated well with TI and weakly with DPPH. Malonylglucoside of all the aglycones, total genistein (TGin), and total daidzein (TDin) showed strong correlation with total isoflavones, whereas acetylglucoside and aglycone levels did not significantly correlate with total isoflavone. Profiling of soybean isoflavone is helpful in understanding the regulation of isoflavone biosynthesis for greater improved resistance of crops to disease and greater health benefits for humans. This comparative study of soybean cultivars grown in India and Bulgaria throws light on their composition and nutraceutical value.  相似文献   
138.
Functional stay-green (FSG) is characterized by delayed senescence during the reproductive stage in rice. A recombinant inbred line (RIL) population derived from ‘Pusa 677’/‘PSG16’ was used to study the genetics of FSG in a rice mutant, ‘PSG16’. The RILs exhibited significant variation under two N regimes for agro-morphological traits, leaf chlorophyll content, flowering time, yield components and nitrogen (N) use. Using a genome wide linkage map spanning 1910.8 cM with 104 polymorphic markers, we have mapped six major quantitative trait loci (QTLs). One robust QTL on chromosome 1 was associated consistently across different N regimes with chlorophyll content and flowering time. The QTL on chromosome 7 was associated with grain number, whereas the QTL on chromosome 6 was found related to N harvest index and spikelet fertility. Although ‘PSG16’ showed a clear advantage in grain yield as well as having better N assimilation, we could not establish a direct genetic relationship SG trait and N use. Based on the QTL information, FSG trait of ‘PSG16’ could be useful in deciphering multiple stress responses in rice.  相似文献   
139.
Effects of Cd, Pb, and Ni on three freshwater green algae, Ankistrodesmus falcatus, Scenedesmus obliquus, and Chlorococcum spp., were studied. Cadmium and Pb had slight stimulatory effects on growth at lower concentrations (0.1 to 1.0 ppm) while they were lethal at higher concentrations (> 5 ppm). Nickel was not lethal between 0.1 and 10.0 ppm. When combined, both Cd and Ni and Cd and Pb showed interaction on A. falcatus. No interaction was noted between Pb and Ni.  相似文献   
140.
The aboveground biomass dynamics and net primary productivity were investigated to assess the productive potential of Dipterocarpus forest in Manipur, Northeast India. Two forest stands (stand I and II) were earmarked randomly in the study site for the evaluation of biomass in the different girth classes of tree species by harvest method. The total biomass was 22.50 t·ha-1 and 18.27 t·ha-1 in forest stand I and II respectively. Annual aboveground net primary production varied from 8.86 to 10.43 t·ha-1 respectively in two forest stands (stand I and II). In the present study, the values of production efficiency and the biomass accumulation ratio indicate that the forest is at succession stage with high productive potential.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号