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排序方式: 共有388条查询结果,搜索用时 31 毫秒
361.
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363.
对粘接结构进行超声导波无损检测与评估是一个有挑战性的前沿性课题.针对此问题,研究了SH0导波在界面为理想连接的三层板状粘接结构中传播时的相位变化情况.首先基于波传播的控制方程,建立了粘接结构中反射和透射SH0导波相对于入射SH0导波的相位差解析模型.然后利用数值模拟计算了铝/环氧树脂/铝粘接结构中反射和透射SH0导波的相位差曲线.最后分析了入射角度和频厚积的变化对反射和透射SH0导波相位差的影响.结果表明,对于具体的粘接结构,反射和透射SH0导波在其中传播时的相位差变化主要依赖于入射角度、频率等参数.在特定的频厚积下,当声波水平入射时,反射和入射SH0导波同相位.无论入射角度为多大,随着频厚积的增大,反射SH0导波的相位差曲线均会产生周期性谐振.对于透射SH0导波,当声波垂直入射时,其相位差曲线的改变无规律可循;但是随着入射角度逐渐增大,透射SH0导波的相位差曲线逐渐变规则.所得结果可为实验时研究板状粘接结构中SH0导波的传播特性以及提取SH0导波回波中的有用信息和定位提供一定的理论指导. 相似文献
364.
Virtudes Navarro-Bañón José Vega-Baudrit Patricia Vázquez José Miguel Martín-Martínez 《Macromolecular Symposia》2005,221(1):1-10
Fumed nanosilicas with different degree of silanization were used to obtain nanosilica-polyurethane (TPU) composites to modify their rheological and mechanical properties. The higher the silanol content of the nanosilica, the higher the storage modulus and the thermal stability of the silica-TPU composite. DMTA experiments confirmed that the TPU-silica interactions increased by increasing the silanol content of the nanosilica. 相似文献
365.
通过一种分光棱镜组的胶合工艺,从胶合仪器的工作原理、调试、胶合方法及胶合剂等方面讨论了在现有技术水平且无专用仪器的情况下,如何保持分光棱镜组支光路中光束的折转角变、平行性及位置精度。 相似文献
366.
The adhesive strength of a fiber-polymer interface is determined, where epoxy resin blends and linear heat-resistant thermoplastics - polysulfone (PSF) and polyetherimide (Ultem) - are used as matrices. Steel wire and polyamide (nylon-6) fibers are taken as reinforcing fillers. It is shown that the addition of PSF to epoxy resin results in a maximum on the concentration curve corresponding to a 10% PSF content. It is also found that the adhesive strength of the ED-20+Ultem-steel wire interface is practically independent of the modifier content under low (up to 10%) Ultem concentrations. 相似文献
367.
This paper is devoted to the behaviour analysis of adhesion interfaces considered either from the point of view of the adherence mechanical tests, or from the point of view of the adhesive joint resistance and wet atmosphere ageing. Adhesive interfaces between rubber-like silicon polymers and oxide substrates are investigated. The first part considers the physicochemical optimisation and mechanical efficiency evaluation of primer surface treatments. A new route of optimisation for primer film elaboration is proposed, using the sol-gel chemistry. The simple-lap shear adherence test is analysed and modelled through finite element calculation. It is proved that, in the case of rubber-like adhesive, the macroscopic shear results in dominant principal tension stresses in the polymer film. It is demonstrated that the valuable criterium for adherence evaluation is the principal stretch to fracture. This applies to fracture located in the interface region as well as to fracture initiated in the polymer bulk. An additional result is the influence of the substrate surface physicochemistry on the crosslinking process of the elastomer during adhesion process. The ageing process in hot water or wet atmosphere of that kind of adhesion joints is studied by several investigation means. It is shown to be strongly dependant on the degradation mechanisms of the substrates. A basic explanation of the ageing behaviour is proposed, involving a progressive modification of the aggressive medium by the substrate corrosion residues, inducing a degradation of the interface region. The CaCO3 reinforcing charge is proved to play a protective role, by a sacrificial action. 相似文献
368.
K. Mühle 《Colloid and polymer science》1985,263(8):660-672
The adhesive forces between solid particles mutually attached during coagulation or bridging flocculation are important for modelling floc stability. Results are presented in this study which are obtained from experiments on the adhesion of glass or quartz particles to a flat glass substrate (centrifugal method) or to the wall of a glass capillary through which an aqueous electrolyte solution was passed. Coagulation experiments carried out in 10–2 mole/1 MgCl2 showed the action of hydration layers on hydrophilic surfaces, whereas surface methylation is associated with adhesion in the inner potential minimum. In addition essential ageing effects interpreted as interparticle gelation were observed, especially on the interaction of alkali glass surfaces. Adhesive strength in the case of flocculation with hydrolysed polyacrylamide and a cationic Praestol mainly depends on the polymer concentration and on the preadsorption conditions before the particle-substrate attachment. A significant strengthening of adhesion due to reconformation of the bridging agents was not observed for a contact time greater than 3 min. The effect of steric stabilization with polymer overdosing could be proved by a special preparation technique.Publication no. 922 from the Research Institute of Mineral Processing of the Academy of Sciences of German Democratic Republic, Freiberg. 相似文献
369.
可见光固化树脂已广泛应用于牙科临床。为了改进树脂性能,需对不同配方的材料进行选择,这就要建立各种比较评价的方法。本文所述付里叶变换红外吸收光谱法(FTIR)是一种方便、实用的方法,可出牙釉质粘合剂中双的反应情况,由其变化温度及最终的殘率可推断材料的组成与结构,结合对材料其它性能的测定,能为各种体系的比较提供依据。 相似文献
370.
自然界中许多昆虫通过分泌一层油性液体薄膜实现其爪垫表皮和光滑壁面之间粘附和解粘附,从而实现在光滑壁布的快速爬行.为了提示昆虫爪垫与光滑壁面间微量液体薄膜对生物粘着的意义,基于自行研制的粘着接触实验仪,采用微量的[emim[Tf2N]离子液体和聚α烯烃油,观测其受限在纳米级光滑钢球表面与玻璃表面之间的接触行为以及法向粘着力.实验发现,临界体积(10-12—10-9L)范围内的受限液滴达到临界厚度(小于2μm)后会出现自动铺展和瞬时收缩行为,并同时提供幅值稳定且数值
关键词:
受限液体
粘着力
昆虫爪垫
类固化 相似文献