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951.
We consider the Euler–Poincaré equation on ${\mathbb{R}^d, \, d \geqq 2}$ R d , d ≧ 2 . For a large class of smooth initial data we prove that the corresponding solution blows up in finite time. This settles an open problem raised by Chae and Liu (Commun Math Phys 314:671–687, 2012). Our analysis exhibits some new concentration mechanisms and hidden monotonicity formulas associated with the Euler–Poincaré flow. In particular we show an abundance of blowups emanating from smooth initial data with certain sign properties. No size restrictions are imposed on the data. We also showcase a class of initial data for which the corresponding solution exists globally in time. 相似文献
952.
完整约束多体系统第一类Lagrange方程建模得到的运动方程是指标-3形式的微分-代数方程(differental-algebraic equations,DAEs).如果同时考虑速度约束,将得到超定运动方程,该方程是指标-2的超定微分-代数方程(over-determined differential-algebraic equations,ODAEs).基于结构动力学中常用的广义-α方法,将其拓展,求解包含速度约束的超定运动方程,相对于其他求解指标-2 ODAEs的算法,新的算法没有增加离散得到的非线性方程组方程的数目.通过数值实验验证算法,并说明其求解ODAEs不存在精度降阶的现象,仍然具有二阶精度,同时算法的数值耗散也是可以控制的.最后新方法与其他求解多体系统ODAEs形式运动方程算法的CPU时间进行了比较分析. 相似文献
953.
By using a KNO3-aging ferrous hydroxide gel method, Fe3O4 particles with sizes ranging from 35 to 1500 nm were synthesized. The particles were covered with a silica coating to form Fe3O4-SiO2 core-shell structures by using the improved conventional Stöber polycondensation method. The thickness of the SiO2 covering on magnetite particles surface varies from 10 to 20 nm. The morphology, size and composition of the particles were determined by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The particles with and without coating with SiO2 were pressed into slices with an oil press at 10 MPa. Subsequently, the coercive forces HC of the particles were measured by VSM at room temperature, and the critical size for a single domain was estimated. The shape of the particles is basically spherical when the size is smaller than 800 nm, while it is hexagonal for larger particles. The HC of Fe3O4-SiO2 core-shell structure was larger than that of the uncoated Fe3O4 particles by 20%, which was explained to be due to the reduction of inter-particle magnetostatic interaction, supported by an agreement with the packing factor. The dependence of HC on magnetic particle size could be explained and fitted by the Heewell-Knozam stacking density equation and object-oriented micromagnetic computing framework (OOMMF) micromagnetic software. the results agree well with the experimental data. 相似文献
954.
Xianliang Sheng Jin Zhai Lei Jiang Daoben Zhu 《Applied Physics A: Materials Science & Processing》2009,96(2):473-479
Abstract ZnO nanoparticles with average diameter of 12 nm were used to fabricate ZnO photoanodes by electrohydrodynamic (EHD)
technique for dye-sensitized solar cells (DSSCs). To enhance the light scattering and conversion efficiency, the ZnO film
with scattering hollow cavities (HCs) was realized by calcining polystyrene spheres (PSs) in the film. The films had strong
light scattering ability and the overall light to electricity conversion efficiency (η) was improved and reached 5.5% under illumination of simulated solar light (AM-1.5, 100 mW/cm2). 相似文献
955.
956.
提出一种基于双相位编码的单通道彩色图像加密方法. 在该方法中,将彩色图像转换到HSI空间,I分量即可作为相位编码的原始待加密图像;而采用双随机相位加密技术对S分量加密后得到的相息图,与H分量一起构成了对I分量加密的双相位. 由于双随机相位加密技术有很高的安全性,在不知密钥的情况下解出S分量几乎是不可能的,由此保证了彩色图像加密的安全性. 模拟实验结果证明了该方法的有效性.
关键词:
彩色图像
单通道
双相位编码 相似文献
957.
发光二极管(KED)可较广泛地应用于电学演示实验中,其低工作电流、单向导通、多色彩等特点,可弥补小白炽灯泡及检流计的一些不足,使演示实验不仅简便易行,而且演示效果直观,生动。 相似文献
958.
959.
960.
Fenxia Zhu Yingxiang Du Jiaquan Chen Bin Chen Yanqian Zhu Xiang Zhai Shu Xu Wenhui Zhou 《Chromatographia》2009,69(11-12):1315-1320
Polygalacturonic acid, a linear high molecular weight homopolysaccharide was investigated as a chiral selector in capillary zone electrophoresis for the separation of enantiomers of basic drugs. The choices of running buffer pH and concentration of chiral selector were found to be important for the improvement of enantioselectivity. The effects of background electrolyte concentration and the capillary temperature on the separation were also examined. Enantioseparations were carried out in the acidic conditions using 1.5% polygalacturonic acid (w/v) in a 40 mM phosphate buffer under an applied voltage of 15 kV. The optimization of these separations was dependent on the nature of the analytes and could be achieved by the proper choice of experimental conditions. A brief mechanism of enantiorecognition by polygalacturonic acid was also given. 相似文献