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某轴流压气机叶尖间隙效应实验研究 总被引:3,自引:0,他引:3
本文对某低速轴流压气机叶尖间隙尺度对性能的影响进行了实验研究,并通过不同的机匣结构情况研究一种叶尖漏流不敏感机匣。实验表明,不同的间隙尺度对叶轮机总体性能存在十分明显的影响。对绝大部分运行状态,小间隙下的压升和效率均明显高于大间隙的情况。另外,所采用的毛刷式和篦齿式的机匣实验结果表明,不论毛刷式还是篦齿式机匣,在大流量负攻角情况下对性能的影响不大,但毛刷式机匣并不能达到提高失速裕度的目的,而篦齿式机匣在小流量情况下对压升有所提高,但对效率影响不大。 相似文献
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V. I. Grabovskii 《Fluid Dynamics》2003,38(2):193-202
The optimum shape of the cylindrical internal deformable (flexible) surface of a gas journal bearing of infinite length is designed. The variational problem of determining the clearance shape giving the maximum bearing load capacity is formulated and solved. 相似文献
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van de Waterbeemd H Smith DA Jones BC 《Journal of computer-aided molecular design》2001,15(3):273-286
Lipophilicity, often expressed as distribution coefficients (log D) in octanol/water, is an important physicochemical parameter influencing processes such as oral absorption, brain uptake and various pharmacokinetic (PK) properties. Increasing log D values increases oral absorption, plasma protein binding and volume of distribution. However, more lipophilic compounds also become more vulnerable to P450 metabolism, leading to higher clearance. Molecular size and hydrogen bonding capacity are two other properties often considered as important for membrane permeation and pharmacokinetics. Interrelationships among these physicochemical properties are discussed. Increasing size (molecular weight) often gives higher potency, but inevitably also leads to either higher lipophilicity, and hence poorer dissolution/solubility, or to more hydrogen bonding capacity, which limits oral absorption. Differences in optimal properties between gastrointestinal absorption and uptake into the brain are addressed. Special attention is given to the desired lipophilicity of CNS drugs. In examples using -blockers, Ca channel antagonists and peptidic renin inhibitors we will demonstrate how potency and pharmacokinetic properties need to be balanced. 相似文献
6.
To investigate the pharmacokinetic mechanism of hepatobiliary excretion and brain distribution of caffeine, this study uses a method based on microdialysis technique and liquid chromatography that allows continuous and concurrent in vivo monitoring of extracellular caffeine in the blood, brain and bile of anesthetized rats following the administration of caffeine (3 or 10 mg/kg, i.v.) through the femoral vein. Dialysates of the blood, brain and bile were directly injected onto the liquid chromatographic system and no further clean-up procedures were required. The study design consisted of two groups of six rats in parallel: the rats of the control group received caffeine (3 or 10 mg/kg, i.v.) alone and those of the cyclosporine treated-group were injected cyclosporine (10 mg/kg, i.v.) 10 min prior to caffeine administration (3 or 10 mg/kg, i.v.). The decline of caffeine in the blood, brain striatum and bile suggested that caffeine had rapid exchange and equilibration between the peripheral compartment and the central nervous system. In addition, the results indicated that caffeine underwent hepatobiliary excretion and was distributed into brain. When cyclosporine was co-administered, the pharmacokinetic parameters were not significantly altered. The results of this study reveal that the pharmacokinetic mechanism of hepatobiliary excretion and brain distribution of caffeine might not relate to P-glycoprotein. 相似文献
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To intensify experimental research within the field of orthopaedic tribology, a three-station, dual motion, high frequency (25.3 Hz) circular translation pin-on-disc wear test device was recently introduced. In the present study, the pins were CoCr with a spherical, polished bearing surface of 28 mm radius, whereas the flat discs were conventional UHMWPE. This configuration was intended to simulate the wear mechanisms of total knee prostheses. The number of wear cycles run was as high as 200 million. The mean wear rate was 0.35 mg per one million cycles (0.77 mg/24 h) which corresponded to a mean wear factor of 3.5 × 10−6 mm3/Nm. The study provided further proof that a wear test for orthopaedic implant materials can be accelerated by substantially increasing the cycle frequency, provided that the sliding velocity remains close to the values obtained from biomechanical studies. Hence, the moderate frictional heating will not lead to unrealistic wear mechanisms. 相似文献
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《Biomedical chromatography : BMC》2017,31(6)
We developed and validated a high‐resolution liquid chromatography mass spectrometry method for the quantification of furosemide in camel plasma which was used for a pharmacokinetic study in camels. Plasma samples were extracted by supported liquid extraction and furosemide and internal standard (furosemide‐D5) were separated on a an Agilent Zorbax XDB C18 column (50 × 2.1 mm i.d., 3.5 μm). Data was acquired in full‐scan mode over a mass range of 200–400 Da in negative electrospray mode at a resolution of 70,000. Linear calibration curves were obtained over the concentration ranges of 1.0–10,000 ng/mL. The validated method was then successfully applied in evaluating the pharmacokinetics and metabolites of furosemide in six camels (Camelus dromedarus ) and we were able to advice on a withdrawal time of furosemide treatment before racing. 相似文献
9.
明日叶黄酮类化合物清除羟基自由基活性研究 总被引:1,自引:0,他引:1
为了研究明日叶黄酮类化合物对羟基自由基的清除作用,以明日叶(主要取叶片)为原料,用体积分数为65%乙醇提取明日叶总黄酮,测定其总黄酮含量.通过Fenton反应体系产生羟基自由基,利用明日叶提取液中的功能成分黄酮类化合物对羟基自由基的清除作用进行研究.结果表明:明日叶提取物总黄酮质量分数为10.18%,且黄酮类化合物对羟基自由基有较强清除效力,当提取物总黄酮浓度在0.1~1.0 mg/mL范围内,其与清除率呈正相关.明日叶中黄酮类化合物对羟基自由基有较强清除效力,作为天然抗氧化产品开发具有一定价值. 相似文献
10.
光伏产业的发展使得对硅材料的需求日益增加,同时硅单晶生产行业竞争也日趋激烈。作为生产硅单晶的重要装备,单晶炉的稳定性和可靠性关系到硅单晶生产效率的提升和成本的下降,因此其驱动系统的设计和优化成为装备制造的关键环节。本文以NVT-HG2000-V1型硅单晶生长炉的驱动系统为研究对象,用SolidWorks三维建模实现虚拟装配,采用ADAMS建立其动力学仿真模型,并对驱动系统的运动过程进行仿真模拟。采用控制变量法定量分析了铜套与升降轴的配合间隙及丝杠参数对驱动力和驱动力矩的影响规律,进而在提高硅单晶生长炉装备稳定性和可靠性方面给出合理的技术建议。结果表明,铜套与升降轴的配合间隙达到0.071 mm后能有效降低驱动系统运行所需驱动力矩,丝杠倾斜度、螺纹螺距与螺纹间摩擦系数的增大均会导致驱动系统运行所需力矩大幅增加。 相似文献