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1.
野生及人工养殖中华鲟幼鱼肌肉营养成分的比较   总被引:26,自引:0,他引:26  
宋超  庄平  章龙珍  刘健  罗刚 《动物学报》2007,53(3):502-510
对野生及人工养殖中华鲟幼鱼的肌肉营养成分和营养品质进行了分析比较.结果表明:野生中华鲟幼鱼肌肉中水分、粗蛋白和粗灰分含量均显著高于人工养殖中华鲟(P<0.05),而粗脂肪含量显著低于人工养殖中华鲟(P<0.05).野生和人工养殖中华鲟幼鱼的氨基酸组成基本一致,均含有18种氨基酸,必需氨基酸指数(EAAI)分别为72.02、66.21,其构成比例符合联合国粮农组织/世界卫生组织(FAO/WHO)的标准.脂肪酸中二十碳五烯酸(EPA)与二十二碳六烯酸(DHA)的含量野生中华鲟显著高于人工养殖中华鲟(P<0.05),分别为22.99%、7.15%.矿物质含量丰富,微量元素含量野生中华鲟明显高于人工养殖中华鲟[动物学报 53(3):502-510,2007].  相似文献
2.
Towards an ecological understanding of biological nitrogen fixation   总被引:25,自引:5,他引:20  
N limitation to primary production and other ecosystem processes is widespread. To understand the causes and distribution of N limitation, we must understand the controls of biological N fixation. The physiology of this process is reasonably well characterized, but our understanding of ecological controls is sparse, except in a few cultivated ecosystems. We review information on the ecological controls of N fixation in free-living cyanobacteria, vascular plant symbioses, and heterotrophic bacteria, with a view toward developing improved conceptual and simulation models of ecological controls of biological N fixation.A model (Howarth et al. 1999) of cyanobacterial fixation in lakes (where N fixation generally increases substantially when N:P ratios are low) versus estuaries (where planktonic N fixation is rare regardless of N:P ratios) concludes that an interaction of trace-element limitation and zooplankton grazing could constrain cyanobacteria in estuaries and so sustain N limitation. Similarly. a model of symbiotic N fixation on land (Vitousek & Field 1999) suggests that shade intolerance, P limitation, and grazing on N-rich plant tissues could suppress symbiotic N fixers in late-successional forest ecosystems. This congruence of results raises the question – why do late-successional tropical forests often contain many potentially N-fixing canopy legumes, while N fixers are absent from most late-successional temperate and boreal forests? We suggest that relatively high N availability in lowland tropical forests permits legumes to maintain an N-demanding lifestyle (McKey 1994) without always being required to pay the costs of fixing N.Overall, both the few simulation models and the more-numerous conceptual models of ecological controls of biological N fixation suggest that there are substantial common features across N-fixing organisms and ecosystems. Despite the many groups of organisms capable of fixing N, and the very different ecosystems in which the process is important, we suggest that these common controls provide a foundation for the development of regional and global models that incorporate ecological controls of biological N fixation.  相似文献
3.
不同施肥水平下小麦籽粒中部分微量元素含量的研究   总被引:19,自引:0,他引:19  
在不同肥力水平和结构下对不同肥量籽粒中部分微量元素含量变化进行研究,结果表明:施肥量大小和肥料构成对小麦籽粒中微量元素含量有明显的影响,在低肥水平下籽粒中Mn、Zn和Fe含量增加,其中Zn的增幅超过1倍,Cu和Al含量降低;在中肥水平下微肥用量增加1倍,籽粒中Mn含量高11.2%,Al和Zn含量分别降低50%和30.1%,Fe和Cu元素含量变化不大,调节其它肥料量和结构,籽粒中Mn、Zn、Cu含量降低;在高肥水平下增加钾肥,有利于籽粒中Mn、Zn、Fe、Al含量积累,分别高23.2%、16.2%、33.9%和58.6%,而Cu含量变化不大。在中肥投入水平下调节氮肥籽粒中微量元素含量随着肥力水平提高而降低,在高肥投入水平下减少氮肥用量有利于籽粒中Fe、Al和Zn的积累,Fe含量变化最大,增加2.14~2.63倍,Al含量高63.7%~65.7%,锌含量高13.3%~17.5%,铜的含量变化不大。锰含量随着磷肥用量的增加而增加。  相似文献
4.
Oxidative stress, metabolism of ethanol and alcohol-related diseases   总被引:18,自引:0,他引:18  
Alcohol-induced oxidative stress is linked to the metabolism of ethanol. Three metabolic pathways of ethanol have been described in the human body so far. They involve the following enzymes: alcohol dehydrogenase, microsomal ethanol oxidation system (MEOS) and catalase. Each of these pathways could produce free radicals which affect the antioxidant system. Ethanol per se, hyperlactacidemia and elevated NADH increase xanthine oxidase activity, which results in the production of superoxide. Lipid peroxidation and superoxide production correlate with the amount of cytochrome P450 2E1. MEOS aggravates the oxidative stress directly as well as indirectly by impairing the defense systems. Hydroxyethyl radicals are probably involved in the alkylation of hepatic proteins. Nitric oxide (NO) is one of the key factors contributing to the vessel wall homeostasis, an important mediator of the vascular tone and neuronal transduction, and has cytotoxic effects. Stable metabolites--nitrites and nitrates--were increased in alcoholics (34.3 +/- 2.6 vs. 22.7 +/- 1.2 micromol/l, p < 0.001). High NO concentration could be discussed for its excitotoxicity and may be linked to cytotoxicity in neurons, glia and myelin. Formation of NO has been linked to an increased preference for and tolerance to alcohol in recent studies. Increased NO biosynthesis also via inducible NO synthase (NOS, chronic stimulation) may contribute to platelet and endothelial dysfunctions. Comparison of chronically ethanol-fed rats and controls demonstrates that exposure to ethanol causes a decrease in NADPH diaphorase activity (neuronal NOS) in neurons and fibers of the cerebellar cortex and superior colliculus (stratum griseum superficiale and intermedium) in rats. These changes in the highly organized structure contribute to the motor disturbances, which are associated with alcohol abuse. Antiphospholipid antibodies (APA) in alcoholic patients seem to reflect membrane lesions, impairment of immunological reactivity, liver disease progression, and they correlate significantly with the disease severity. The low-density lipoprotein (LDL) oxidation is supposed to be one of the most important pathogenic mechanisms of atherogenesis, and antibodies against oxidized LDL (oxLDL) are some kind of epiphenomenon of this process. We studied IgG oxLDL and four APA (anticardiolipin, antiphosphatidylserine, antiphosphatidylethanolamine and antiphosphatidylcholine antibodies). The IgG oxLDL (406.4 +/- 52.5 vs. 499.9 +/- 52.5 mU/ml) was not affected in alcoholic patients, but oxLDL was higher (71.6 +/- 4.1 vs. 44.2 +/- 2.7 micromol/l, p < 0.001). The prevalence of studied APA in alcoholics with mildly affected liver function was higher than in controls, but not significantly. On the contrary, changes of autoantibodies to IgG oxLDL revealed a wide range of IgG oxLDL titers in a healthy population. These parameters do not appear to be very promising for the evaluation of the risk of atherosclerosis. Free radicals increase the oxidative modification of LDL. This is one of the most important mechanisms, which increases cardiovascular risk in chronic alcoholic patients. Important enzymatic antioxidant systems - superoxide dismutase and glutathione peroxidase - are decreased in alcoholics. We did not find any changes of serum retinol and tocopherol concentrations in alcoholics, and blood and plasma selenium and copper levels were unchanged as well. Only the zinc concentration was decreased in plasma. It could be related to the impairment of the immune system in alcoholics. Measurement of these parameters in blood compartments does not seem to indicate a possible organ, e.g. liver deficiency.  相似文献
5.
桉树人工林地土壤酶活性与微量元素含量的关系   总被引:17,自引:2,他引:15       下载免费PDF全文
运用典范相关分析研究了桉树人工林地土壤酶活性和土壤微量元素含量关系。结果表明,Zn和Mn对土壤蛋白酶活性的促进作用最大。Zn在一定程度上对脲酶和过氧化氢酶有抑制作用;而Mn对脲酶和过氧化氢酶有促进作用。结合林地生物的生长特征等因子,"综合土壤酶因子"可作为土壤肥力评价的一个指标,对桉树林地土种的划分有一定意义。  相似文献
6.
应用古人骨的元素、同位素分析研究其食物结构   总被引:14,自引:1,他引:13  
本文从原理和方法上对目前由人骨元素、同位素分析研究古人类食物结构的三个主要方面,即骨胶原碳十三、氮十五的分析,微量元素锶、钡分析以及同位素锶、铅的分析逐一做了介绍。在此基础上结合自己的工作将国内该研究领域中有关的研究现状和主要研究成果,特别是获得的新进展做了回顾和总结。  相似文献
7.
Transport characteristics of essential trace elements as zinc, copper, selenium and iron have been studied in maternal–fetal direction in normal pregnancies, using in vitro perfusion of human placental lobules. Solutions of trace elements corresponding to twice the physiological concentrations were injected (100 l bolus) into the maternal arterial perfusate. Serial perfusate samples were collected every 30 sec from venous outflows for a study period of 5 min. Concentrations of these trace elements and their transport kinetics were determined. Transport fractions (TF) of zinc, copper, selenium and iron averaged 0.21, 0.49, 0.55 and 0.10% of maternal load respectively. Other parameters such as area under the curve, clearance, elimination constant, absorption and elimination rates showed some significant differences between the various elements. Copper and selenium appear to be transported passively in maternal–fetal direction, while for iron and zinc, role of active transport for transfer across the human placental membrane cannot be discounted. We speculate that alterations in copper: zinc TR50 (transport rate for 50% efflux) and TF ratios could serve as useful indicators for assessing placental transport status of these essential elements in complicated pregnancy states.  相似文献
8.
轮叶党参营养成分的研究   总被引:12,自引:1,他引:11  
本文研究了轮叶党参的茎叶、去皮根及根皮中的营养成分氨基酸、维生素、微量元素的含量。结果显示,这三种营养成分都在根皮中最多,茎叶和去皮根中的含量也都多于一般蔬菜中的含量,为轮叶党参的合理应用提供了科学依据。  相似文献
9.
Measurements of the Ca, Sr, and Mg contents of individual calcitic shells of non-marine ostracods and their host waters, both in lakes and controlled aquaria, permit the calculation of the distribution coefficients of Sr/Ca and Mg/Ca partitioning in ostracod shells. We report new KD[Sr] for seven genera of non-marine ostracods and KD[Mg] for Cyprideis at 25°C.Strontium partitioning is virtually temperature-independent, and is related to the Sr/Ca of the host water, and in Ca2+-saturated waters, to the salinity of the water. Magnesium partitioning is dependent on both temperature and Mg/Ca of the host water.For simple closed-basin lakes (crater lakes are ideal), the Sr content of ostracods is a sensitive indicator of salinity and thus evaporation/precipitation changes, which in turn, indicate variations in continental climate. A 10000-year continuous palaeosalinity record established by Sr and Mg contents of fossil ostracods for Lake Keilambete, southeastern Australia, is in close agreement with an independent palaeosalinity estimate based on sediment textures.We suggest rules that allow Sr and Mg analyses of suites of individual fossil ostracod shells from lacustrine sediments to be interpreted in terms of palaeosalinity and palaeotemperature variations.  相似文献
10.
5个太子参品系的微量元素分析研究   总被引:11,自引:3,他引:8  
对江苏、山东、安徽、福建5个不同产地的太子参品系进行了镁、钙、锰、铁、钴、铜、锌、硒8种微量元素的测定,并绘制了各太子参品系的微量元素图谱。研究结果表明不同品系的太子参的微量元素含量不同。各品系的微量元素图谱有明显的差异性,特别是福建柘荣品系的微量元素图谱与其他品系的微量元素图谱相比较其差异性较大,但太子参各品系的微量元素图谱也存在一定的共性。  相似文献
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