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261.
Prediction of melt depth in selected architectural materials during high-power diode laser treatment
The development of an accurate analysis procedure for many laser applications, including the surface treatment of architectural materials, is extremely complicated due to the multitude of process parameters and materials characteristics involved. A one-dimensional analytical model based on Fourier's law, with quasi-stationary situations in an isotropic and inhomogeneous workpiece with a parabolic meltpool geometry being assumed, was successfully developed. This model, with the inclusion of an empirically determined correction factor, predicted high-power diode laser-induced melt depths in clay quarry tiles, ceramic tiles and ordinary Portland cement that were in close agreement with those obtained experimentally. It was observed, however, that as the incident laser line energy increased (>15 W mm−1 s−1/2), the calculated and the experimental melt depths began to diverge at an increasing rate. It is believed that this observed increasing discrepancy can be attributed to the fact the model developed neglects sideways conduction which, although it can be reasonably neglected at low-energy densities, becomes significant at higher energy densities since one-dimensional heat transfer no longer holds true. 相似文献
262.
磷酸钙骨水泥/聚肽共聚物生物复合材料力学性能及微观结构 总被引:3,自引:0,他引:3
磷酸钙骨水(Calcium Phosphate Cement,CPC)是一种新型的人工骨材料,可用于人体骨缺损的修复,具有良好的生物相容性、骨传导性和骨替代性.然而,磷酸钙骨水泥的抗压强度较低,脆性较大,限制了其应用,因而提高抗压强度和减小其脆性成为CPC研究领域的一个重要课题.目前,普遍采用添加纤维的方法来提高CPC材料的抗压强度和韧性.然而大多数的纤维是非降解性的. 相似文献
263.
1引言 氯氧镁水泥(以下简称镁水泥),又称索瑞尔水泥(Sorel)[1],是由活性MgO、MgCl2和水形成的气硬性材料.镁水泥初期的相主要是相5(5Mg(OH)2·MgCl2·8H2O)和相3(3Mg(OH)2·MgCl2·8H2O).这两种相均不很稳定,受大气中CO2的作用而碳化为新相2(2MgCO3·Mg(OH)2·MgCl2·6H2O)[2].中期的镁水泥样品中会出现相2.在室外的镁水泥样品会受到CO2和水的双重作用.CO2的碳化和水的溶解浸蚀协同作用会使相2继续发生转化,最终会生成稳定相4(4MgCO3·Mg(OH)2·4H2O),即水菱镁矿[3],也可能有MgCO3生成(相1).所以后期的镁水泥室外样品是含有相4和相1这两种稳定相的. 相似文献
264.
El-Said N. Sayed M. S. Mikhail A. S. 《Journal of Thermal Analysis and Calorimetry》2000,63(2):525-532
The thermal stability of solidified NaNO3 salts in bitumen and cement has been investigated for safety considerations in the field of solidification of radioactive
waste. The thermal decomposition of bitumen and cement in presence of NaNO3 in a temperature range 22–650°C has been studied. The fraction decomposed of the pure samples and mixtures showed slow linear
reactions followed by acceleratory and decay stages. Data are analyzed according to both Freeman-Carroll and Coats-Redfern
kinetics to evaluate the activation energy and the order of reactions of all mixtures. It is found that the activation energies
of bitumen and cement were 594 and 203 kJ mol-1, respectively. The order of reactions of bitumen and cement was 2 and 4, respectively. The addition of NaNO3 shortens the duration of the induction period in all mixtures. It was concluded that solidification of radioactive waste
containing NaNO3 in bitumen and cement should be applied in the temperature range 22–300°C. At temperature higher than300°C
solidification should be in cement.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
265.
本文根据水泥强度的模糊性 ,运用模糊模式识别理论 ,建立了预测水泥强度的模糊贴近度模型 .通过对上海水泥厂提供的实测数据进行模糊计算 ,得到了令人满意的结果 ,为水泥强度的快速预测提供了一种新方法 ,有较好的实用价值 . 相似文献