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171.
Density functional theory is carried out to study cis-doubly N-confused porphyrin and its metal (Cu3+, Ag3+, and Au3+) complexes. The electronic structures and bonding situations of these molecules have been investigated by using the natural bond orbital analysis and the topological analysis of the electron localization function. We have studied the electronic spectra of cis-doubly N-confused porphyrin and its metal complexes with time-dependent density functional theory. The introduction of group 11 transition metals leads to blueshifts of their electronic spectra with respect to that of cis-doubly N-confused porphyrin. In particular, the absorption spectra of the copper complex show some weak Q bands that mainly arise from a combination of ligand-to-metal charge transfer and ligand-to-ligand charge transfer transitions. The relativistic time-dependent density functional theory with spin-orbit coupling calculations indicates that the effects of spin-orbit coupling on the excitation energies of the copper and silver complexes are so small that it is safe enough to neglect spin-orbit interactions for these two complexes. However, it has a significant effect on the absorption spectra of the gold complex. 相似文献
172.
This paper proposes an adaptive buffer replacement algorithm for NAND flash memory-based databases, which is called HDC. HDC introduces an efficient replacing index for selecting pages to be evicted. This replacing index considers two factors: the hot degree of each page and the cost of writing the victim page back to NAND flash memory. It can adaptively change the weight of each factor according to the cost ratio of NAND flash memory. HDC also introduces an efficient partial update scheme, which only writes the dirty data within the dirty victim page back to NAND flash memory for further reducing the number of write operations and writes the dirty data to the free block with the lowest erase count for improving the wear-leveling degree of NAND flash memory. We conduct trace-driven simulations on two kinds of NAND flash memories the cost ratios of which are 118:1 and 2:1. The experimental results show that HDC outperforms the state-of-the-art algorithms on both these kinds of NAND flash memories. 相似文献
173.
We propose a mechanism of the formation of band structures of electromagnetic waves in one-dimensional periodic or nonperiodic systems containing single-negative metamaterials. The formation of passbands in these periodic systems is attributed to two factors, i.e., the existence of localized modes and ‘phase’ matching condition. It is completely different from the Bragg scattering. For the wave transmission in disordered systems, the two factors also play an important role. If they are satisfied, there are abnormal transmission behaviors of electromagnetic waves. It implies that the formation of passbands may not depend on periodic structures. 相似文献
174.
We experimentally investigate optical storage with electromagnetically induced transparency in a dense cold (85)Rb atomic ensemble. By varying the optical depth (OD) from 0 to 140, we observe that the optimal storage efficiency has a saturation value of 50% as OD>50. Our result is consistent with that obtained from hot vapor cell experiments. 相似文献
175.
超声场中气泡的耦合运动 总被引:5,自引:0,他引:5
超声场中气泡除径向振动外,还可能会平动并且相互影响.本文以考虑邻近气泡次级声辐射影响后的球形气泡径向振动模型为基础,结合气泡在声场中受到的力,利用数值方法研究了平面波声场中不同尺寸的两气泡径向振动和平动规律.发现尺寸较大气泡的径向振动具有一定的本征性特征且具有较大平动位移.利用高速摄影系统定性地观察了气泡运动和泡群分布... 相似文献
176.
一种新型Cymbal换能器的研究 总被引:2,自引:0,他引:2
提出并研究了一种新型的Cymbal换能器.与传统的Cymbal换能器相比,该换能器中的压电陶瓷圆盘由一个金属圆环和压电陶瓷圆盘的径向组合体所代替.论文首先探讨了压电陶瓷圆盘和金属圆环组合体的径向振动,用解析方法得出了其径向振动的机电等效电路.在此基础上,得出了新型Cymbal换能器的机电等效电路,并得出了其共振及反共振... 相似文献
177.
脂肪酸囊泡(FAV)是一类重要的纳米容器,然而其形成pH范围较窄且偏碱性环境,限制了其应用。 本文将共轭亚油酸(CLA)与海藻酸钠(SA)在近中性环境下共同自组装囊泡化纳米容器并提高其膜稳定性。动态激光光散射(DLS)和透射电子显微镜(TEM)结果表明,当SA质量分数为25%~50%时复合体系可在近中性条件下自组装形成50~250 nm尺寸的囊泡化纳米容器,且pH=7.4时随着质量分数增加囊泡化纳米容器直径增大。 根据SA和CLA在中性环境的物种存在形式推测,二者通过氢键作用驱动形成囊泡化纳米容器。 体外模拟释放实验表明,囊泡化纳米容器具有较高包覆率和较优缓释效果,有望应用于药物传输领域。 相似文献
178.
179.
Dr. Shuyu Zhou Yuxuan Sun Tong Gao Junhong Liao Prof. Shixi Zhao Prof. Guozhong Cao 《Angewandte Chemie (International ed. in English)》2023,62(42):e202311930
Cation-disordered Rocksalt oxides (DRXs) are a promising new class of cathode materials for Li-ion batteries due to their natural abundance, low cost and great electrochemical performance. High entropy strategy in Mn-based DRXs appears to be an effective strategy for improving the rate capability, but it suffers from challenges including capacity degradation. The present paper reports a new group of high entropy DRXs (HE DRX) based on Ni2+-Nb5+ pair; the structural and chemical evolution upon cycling of DRXs with an increasing transition metal (TM) species are systematically investigated. An explanation is proposed for how the crystal field stability energy determines that HE DRX could exist in single Rocksalt solid solution structures. We further reveal that the charge compensation mechanism in HE DRX is the result of various TM synergistic effect. More importantly, through various in situ and ex situ techniques and theoretical calculation, the effective integration of more TM cation species within the HE DRX framework promotes better Li+ diffusion and improves lattice oxygen stability, consequently increasing capacity upon cycling. 相似文献
180.
Wenbo Wu Kui Chen Dr. Xiunan Zhang Dr. Ting Wang Shuyu Li Hongtu Zhao Prof. Lina Zhou Prof. Xin Huang Prof. Hongxun Hao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2023,29(1):e202202598
Multiple stimuli-responsive molecular crystals are attracting extensive attentions due to their potential as smart materials, such as molecular machines, actuators, and sensors. However, the task of giving a single crystal multiple stimuli-responsive properties remains extremely challenging. Herein, we found two polymorphs (Form O and Form R) of a Schiff base compound, which could respond to multiple stimuli (external force, acid, heat). Form O and Form R have different elastic deformability, which can be attributed to the differences in the molecular conformation, structural packing and intermolecular interactions. Moreover, both polymorphs exhibit reversible bending driven by volatile acid vapor, which we hypothesize is caused by reversible protonation reaction of imines with formic acid. In addition, jumping can be triggered by heating due to the significant anisotropic expansion. The integration of reversible bending and jumping into one single crystal expands the application scope of stimuli-responsive crystalline materials. 相似文献