全文获取类型
收费全文 | 428篇 |
免费 | 5篇 |
国内免费 | 12篇 |
专业分类
化学 | 154篇 |
晶体学 | 2篇 |
力学 | 159篇 |
综合类 | 3篇 |
数学 | 16篇 |
物理学 | 111篇 |
出版年
2024年 | 1篇 |
2023年 | 19篇 |
2022年 | 6篇 |
2021年 | 8篇 |
2020年 | 6篇 |
2019年 | 4篇 |
2018年 | 9篇 |
2017年 | 13篇 |
2016年 | 12篇 |
2015年 | 17篇 |
2014年 | 28篇 |
2013年 | 19篇 |
2012年 | 15篇 |
2011年 | 33篇 |
2010年 | 20篇 |
2009年 | 25篇 |
2008年 | 24篇 |
2007年 | 32篇 |
2006年 | 19篇 |
2005年 | 19篇 |
2004年 | 18篇 |
2003年 | 9篇 |
2002年 | 10篇 |
2001年 | 10篇 |
2000年 | 11篇 |
1999年 | 6篇 |
1998年 | 9篇 |
1997年 | 4篇 |
1996年 | 10篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有445条查询结果,搜索用时 0 毫秒
71.
Mingxing Ye Yurou Li Zhirong Yang Chang Yao Weixiao Sun Xiangxue Zhang Dr. Wenyao Chen Dr. Gang Qian Prof. Dr. Xuezhi Duan Dr. Yueqiang Cao Prof. Dr. Lina Li Prof. Dr. Xinggui Zhou Prof. Dr. Jing Zhang 《Angewandte Chemie (International ed. in English)》2023,62(19):e202301024
Polyethylene terephthalate (PET) hydrogenolysis can produce benzene, toluene, and xylene (BTX), where the selectivity control is challenging. We report a reaction pathway dictated by the Ru coordination environment by examining the binding geometries of adsorbates on differently coordinated Ru centers and their evolution during PET hydrogenolysis. A BTX yield of 77 % was obtained using a Ru/TiO2 with a Ru coordination number of ca. 5.0 where edge/corner sites are dominant, while more gas and saturated products were formed for Ru/TiO2 containing primarily terrace sites. Density functional theory and isotopic labelling revealed that under-coordinated Ru edge sites favor “upright” adsorption of aromatic adsorbates while well-coordinated Ru sites favor “flat-lying” adsorption, where the former mitigates ring hydrogenation and opening. This study demonstrates that reaction pathways can be directed through controlled reactant/intermediate binding via tuning of the Ru coordination environment for efficient conversion of PET to BTX. 相似文献
72.
73.
The Drucker–Prager yield criterion is used in conjunction with its associated flow rule to find the elastic/plastic stress and strain distributions within the rotating annular disks under plane stress conditions. The main distinguished feature of the model, as compared to typical models used for analysis of disks, is that the material is plastically compressible. Using an approach proposed elsewhere, the solution for strain rates is reduced to one nonlinear ordinary differential equation and two linear ordinary differential equations. These equations can be solved one by one, which significantly simplifies the numerical treatment and increases the accuracy of solution. 相似文献
74.
Shear transformations (i.e., localized rearrangements of particles resulting in the shear deformation of a small region of the sample) are the building blocks of mesoscale models for the flow of disordered solids. In order to compute the time-dependent response of the solid material to such a shear transformation, with a proper account of elastic heterogeneity and shear wave propagation, we propose and implement a very simple Finite-Element (FE)-based method. Molecular Dynamics (MD) simulations of a binary Lennard–Jones glass are used as a benchmark for comparison, and information about the microscopic viscosity and the local elastic constants is directly extracted from the MD system and used as input in FE. We find very good agreement between FE and MD regarding the temporal evolution of the disorder-averaged displacement field induced by a shear transformation, which turns out to coincide with the response of a uniform elastic medium. However, fluctuations are relatively large, and their magnitude is satisfactorily captured by the FE simulations of an elastically heterogeneous system. Besides, accounting for elastic anisotropy on the mesoscale is not crucial in this respect.The proposed method thus paves the way for models of the rheology of amorphous solids which are both computationally efficient and realistic, in that structural disorder and inertial effects are accounted for. 相似文献
75.
新型聚合物固体电解质的红外光谱研究 总被引:1,自引:0,他引:1
采用微波热交联技术制备出了多孔状的聚偏氟乙烯 /聚甲基丙烯酸甲酯 (PVDF PMMA)共混的聚合物固体电解质薄膜材料 ,电性能测试表明该固体电解质薄膜在室温下的电导率可达到 2 0 5× 10 - 3S·cm- 1 ,并具有良好的机械性能。用红外光谱对该膜进行了分析 ,结果表明在聚合物固态电解质中的PVDF ,PMMA ,LiClO4 和γ 丁内指 (BL)之间并不是简单的混合 ,而是存在着某种相互作用 ,并且这种作用只有在生成聚合物固态电解质时 ,才明显地得到了加强。 相似文献
76.
77.
Sarmimala Hore Dr. Robert Dinnebier Dr. Wen Wen Johnathan Hanson Joachim Maier 《无机化学与普通化学杂志》2009,635(1):88-93
The temperature dependent (150–290 K) crystal structure of the low‐temperature α‐phase, and high temperature β‐phase, of succinonitrile has been determined by high resolution in situ powder diffraction. The α‐phase has a monoclinic unit cell that contains four gauche molecules and belongs to the P21/a space group. The crystal undergoes a reversible first‐order phase transition at 233 K into the high temperature β‐phase. The lattice parameters increase with temperature and the phase transition leads to an abrupt 6.7 % increase in volume. The β‐phase crystallizes into a bcc‐structure that belongs to the space group. The high temperature phase; however, is a highly disordered plastic crystal at room temperature that contains both gauche and trans molecules. The non‐linearity in the overall isotropic temperature‐factor indicates other possible phase transitions in the temperature range of 233–250 K. 相似文献
78.
A mixture of post-consumer plastic waste (PE/PP/PS/PVC) was pyrolyzed over various catalysts using a fluid catalytic cracking (FCC) process operating isothermally at ambient pressure. Experiments with various catalysts gave good yields of valuable hydrocarbons with differing selectivity in the final products dependent on reaction conditions. A model based on kinetic and mechanistic schemes for the observed products associated with chemical reactions and catalyst deactivation has been developed. The model gives a good representation of experimental results. It is also an improvement on the currently available empirical “lumping” techniques which are usually severely restricted in terms of product definitions. Additionally, this model represents the benefits of product selectivity for the chemical composition in relation to the effect of structurally different catalyst types, and the performance of the reaction temperature used as well as the particle size of the catalyst selected. 相似文献
79.
Aninda Jiban Bhattacharyya Monalisa Patel Shyamal Kumar Das 《Monatshefte für Chemie / Chemical Monthly》2009,140(9):1001-1010
Abstract Soft matter provides diverse opportunities for the development of electrolytes for all solid state lithium batteries. Here
we review soft matter solid electrolytes for lithium batteriesthat are primarily obtained starting from liquid electrolytic
systems. This concept of solid electrolyte synthesis from liquid is significantly different from prevalent approaches. The
novelty of our approach is discussed in the light of various fundamental issues and in relation to its application to rechargeable
lithium batteries.
Graphical abstract
M. Patel and S. K. Das have contributed equally to the work. 相似文献
80.
The tensile behavior of nylon 6 films has been investigated in relation to water content. Modification of chain mobility in the amorphous phase via water plasticization appears to have a determining impact on the stress-strain response. More specifically, both yield stress value and hardening behavior over a large strain domain are strikingly equivalent for samples drawn at same ΔT between draw temperature Td and main amorphous relaxation temperature Tα. This apparent lack of thermal activation of crystal plasticity in the fibrillar transformation suggests that crystal block fragmentation proceeds via H-bond unzipping through water penetration at defective crystal interfaces. 相似文献