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121.
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基于等级特征与可变信息板(VMS)研究了交叉巢式Logit(CNL)模型及网络交通流分配。综合幂函数与指数函数表示方法给出新的信息效用衰减因子,结合道路等级特征表示VMS对车流的影响系数及CNL模型的分配系数;给出等级结构道路网络的随机用户均衡条件下的交叉巢式Logit路径选择模型及其等价数学规划,并设计网络流分配算法。通过实例网络的计算与分析,得到一些有意义的结论:等级结构越显著的路网总出行时间费用越低且其分散参数(θ)弹性绝对值越大;对具有较强随机性的实际路网,若增加一定的确定性则节省更多网络总出行时间;道路网络中设置了VMS时总出行时间受分散参数的影响更小。 相似文献
123.
A fully 3D OSEM reconstruction method for positron emission tomography (PET) based on symmetries and sparse matrix technique is described. Great savings in both storage space and computation time were achieved by exploiting the symmetries of scanner and sparseness of the system matrix. More reduction of storage requirement was obtained by introducing the approximation of system matrix. Iteration-filter was performed to restrict image noise in reconstruction. Performances of simulation data and phantom data got from Micro-PET (Type: Epuls-166) demonstrated that similar image quality was achieved using the approximation of the system matrix. 相似文献
124.
通过共沉淀法制备了Al2O3-CeO2复合材料,并将其作为电解质应用于半导体离子燃料电池(SIFC)。探究了Al2O3、CeO2物质的量之比不同的Al2O3-CeO2复合电解质对SIFC电化学性能的影响。采用X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)对材料进行了表征。其中,Al2O3、CeO2物质的量之比为1:0.5的Al2O3-CeO2(1:0.5)电池获得了最佳性能,在550℃下,开路电压为1.099 V时最大功率密度为1 142 mW·cm-2。得益于复合电解质在测试气氛下两相间的界面效应,Al2O3-CeO2(1:0.5)电池在较低测试温度下取得了优异的混合离子传导和功率输出性能。 相似文献
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126.
基于粗糙集的指标体系优化及评价方法研究 总被引:2,自引:0,他引:2
粗糙集方法能客观、有效地对有限指标数据进行挖掘,通过属性约简剔除冗余指标,并根据属性重要度生成指标权重,系统地探讨了利用粗糙集进行指标体系优化和综合评价的全过程思路及方法,并通过同行评议专家科技信用评价实例,验证了方法的实用性. 相似文献
127.
The fractai expressions for flow rate and hydraulic conductivity for power-law fluids in a single capillary are derived based on the fractai nature of tortuous capillaries. Every parameter in the proposed expressions has clear physical meaning. The flow rate and hydraulic conductivity for power-law fluids are found to be related to the tortuosity fractal dimension and the power-law index. The flow rate for power-law fluids increases with the increasing power-law index but decreases with the increasing tortuosity fractal dimension. Good agreement between the model predictions for flow in a fractai capillary and in a converging-diverging duct is obtained. The results suggest that the fractal capillary model can be used to model the power-law fluids with different rheologicai properties. 相似文献
128.
Adsorption and Reaction of CO on (100) Surface of SrTiO3 by Density Function Theory Calculation
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Adsorption and reaction of CO on two possible terminations of SrTiO3 (100) surface are investigated by the first-principles calculation of plane wave ultrasoft pseudopotentiai based on the density function theory. The adsorption energy, Mulliken population analysis, density of states (DOS) and electronic density difference of CO on SrTiO3 (100) surface, which have never been investigated before as far as we know are performed. The calculated results reveal that the Ti-CO orientation is the most stable configuration and the adsorption energy (0.449eV) is quite small. CO molecules adsorb weakly on the SrTiO3 (100) surface, there is predominantly electrostatic attraction between CO and the surface rather than a chemical bonding mechanism. 相似文献
129.
First-Principles Calculation of Electronic Structure and Optical Properties of Sb-Doped ZnO
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The geometric structure, electronic structure, optical properties and the formation energy of Sb-doped ZnO with the wurtzite structure are investigated using the first-principles ultra-soft pseudo-potential approach of plane wave based upon the density functional theory. The calculated results indicate that the volume of ZnO doped with Sb becomes larger, and the doping system yields the lowest formation energy of Sb on the interstitial site and the oxygen site. Furthermore, Sb dopant first occupies the octahedral oxygen sites of the wurtzite structure. It is found that Sb substituting on oxygen site behaves as a deep acceptor and shows the p-type degenerate semiconductor character. After doping, the electron density difference demonstrates the considerable electron charge density redistribution, which induces the effect of Sb-doped ZnO to increase the charge overlap between atoms. The density of states move towards lower energy and the optical band gap is broadened. Our culated results are in agreement with other experimental results and could make more precise monitoring and controlling possible during the growth of ZnO p-type materials. 相似文献
130.