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991.
An exact analytical method is employed for studying the diffraction problems in an ocean due to the presence of a specific type of cylinders. In this current work, two models are studied: (i) a floating surface-piercing truncated partial-porous cylinder, (ii) a surface-piercing truncated partial-porous cylinder placed at the bottom. In both cases, the configuration of the composite cylinder is such that it consists of an impermeable inner cylinder rising above the free surface and a coaxial truncated porous cylinder around the lower part of the inner cylinder with the top of the porous cylinder being impermeable. By using linear water wave theory, a three-dimensional representation of the problem is developed based on eigenfunction expansion method. The condition on the porous boundary is defined by applying Darcy’s law. Pressure and velocity satisfy continuity conditions across the linear interface between the adjacent fluid domains. Hydrodynamic force, moment and wave run-up are calculated by using the velocity potentials. Comparisons are carried out with results of wave diffraction by a floating and bottom-mounted compound cylinder, i.e., when the whole cylinder is non-porous. Handy agreements are observed from these comparisons. Through numerical tests, various experiments are carried out to investigate the impact of various parameters, such as porous coefficients, draft ratio, the ratio of inner and outer radii, the water depth etc., on hydrodynamic force, moment and wave run-up. The results clearly indicate that an appropriate optimal ratio for various parameters may be considered in designing practical ocean structures with minimum adverse hydrodynamic effect. The appearance of resonance in the results and role of porosity in mitigating resonance effect are explained. Proposal to select various appropriate parameters for the best possible effect is put forward. 相似文献
992.
E. Yanovska I. Savchenko Y. Polonska L. Ol’khovik D. Sternik O. Kychkyruk 《Molecular Crystals and Liquid Crystals》2018,672(1):92-103
AbstractBy mean of heterophase polimarzation on the silica gel surface has been made in situ immobilization of poly[4-methacroyloxy-(4’-carboxy-3-Сhloro)-azobenzene] and has been received new organic-mineral composit material. The fact of polymer immobilization has been confirmed by IR spectroscopic method and thermogravimetric analysis combined with mass spectrometry. According to the results of thermogravimetric analysis, has been found the mass of the immobilized polymer is 13.33%.The synthesized composite revealed sorption activity to the ions of Cu (II), Pb (II) and Fe (III) micro quantities in a neutral water environment. Maximum sorption ions Cu (II), Pb (II) and Fe (III) degree is reached during first contact hour in static sorption condition. According to the results of isotherms sorption treatment has been determined the silica gel surface poly [4-methacryloxy- (4'-carboxy-3-chloro)-azobenzene] modification led to the sorbtion volum Cu (II) ions more than 1.5 times, for ions Pb (II) - 3.6 times, but for Fe (III) ions - almost 2 times. 相似文献
993.
In this paper a flat structurally tunable acoustic metasurface is constructed based on the helical unit cell. The length of the acoustic channel can be tuned by the screw-in depth of the helix. Accordingly, the wave phase for the transmitted acoustic wave can be tuned and the wavefront can be manipulated. Then multifunctions such as anomalous refraction, point focusing, beam focusing and self-bending can be realized and switched just by screwing in or out the helixes. At the same time, the broadband operating frequency is also realized. The experiments for anomalous refraction and point focusing are also performed, and the results show that the designed metasurface is effective. The present studies have important applications in dynamic manipulation of acoustic waves by metasurfaces. 相似文献
994.
采用电喷雾-离子阱-飞行时间串联质谱(ESI-IT-TOF)技术, 在正/负离子检测模式下对芒柄花素及其同分异构体7-甲氧基异黄酮的质谱裂解规律进行了系统研究. 实验结果表明, 该化合物在正、负离子模式下均得到了5级高分辨质谱. 结果显示, 二者在负离子模式下的碎片相同, 而在正离子模式下的碎片裂解不同. 根据正负离子模式的5级高分辨质谱推导了两者的可能裂解规律, 丰富了异黄酮的ESI-MSn数据, 为其它异黄酮类化合物的分析鉴定提供了有效的质谱方法. 相似文献
995.
采用量子化学方法对丝氨酸组酰胺切割5'-pTpTpCp-3'的作用机理进行了研究. 通过计算得到了两者之间形成多氢键作用的有效分子识别模型以及相关分子结构参数. 从理论上解释了丝氨酸组酰胺对5'-pTpTpCp-3'切割的水解机理. 相似文献
996.
质子化N,N,N',N'-四苄基乙二胺(L)可与[MCl4]2-(M=Mn, Co, Cu)形成二次球形配合物. 通过N—H…Cl相互作用构筑了1D带状和2D层状框架结构, 层中配体L的苄基通过C—H…Cl相互作用分别采取水平和垂直取向, 使1D带状和2D层状呈现凸凹交替排列. 通过层间凸凹部位的C—H…H—C相互作用, 形成了层间空穴, 进而构筑成了3D疏水型隧道框架结构, 乙醇分子能够填充于隧道之中. 在L·2H+·[CuBr4]2-晶体中, 由于[CuBr4]2-没有与配体L的苄基形成C—H…Br氢键, 使配体L的苄基采取了同向取向. 因而, 形成的2D层状框架结构是平展的, 未形成3D疏水型隧道框架结构, 也未发现与乙醇分子的包结现象. 相似文献
997.
998.
999.
围绕圆轮的皮带在达到临界状态前外载增加或降低过程中,局部静摩擦力会发生大小
和方向的改变. 皮带任一点处内力变化可以沿指数曲线增加或减小,取决于加载历史. 皮带
本身是线弹性材料,但变形与力之间是非线性关系,且加载与卸载过程不同,形成滞回圈.
滞回圈内每一点都是皮带可能出现的载荷和变形状态. 相似文献
1000.