全文获取类型
收费全文 | 223篇 |
免费 | 7篇 |
国内免费 | 1篇 |
专业分类
化学 | 158篇 |
晶体学 | 2篇 |
力学 | 1篇 |
数学 | 49篇 |
物理学 | 21篇 |
出版年
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 1篇 |
2020年 | 4篇 |
2019年 | 1篇 |
2018年 | 4篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 2篇 |
2014年 | 6篇 |
2013年 | 3篇 |
2012年 | 10篇 |
2011年 | 14篇 |
2010年 | 5篇 |
2009年 | 12篇 |
2008年 | 10篇 |
2007年 | 18篇 |
2006年 | 14篇 |
2005年 | 13篇 |
2004年 | 9篇 |
2003年 | 11篇 |
2002年 | 12篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 8篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 7篇 |
1974年 | 1篇 |
1973年 | 4篇 |
1972年 | 1篇 |
1968年 | 1篇 |
1911年 | 2篇 |
排序方式: 共有231条查询结果,搜索用时 15 毫秒
81.
Stereospecific Cyclic Poly(methyl methacrylate) and Its Topology‐Guided Hierarchically Controlled Supramolecular Assemblies
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Jing Ming Ren Prof. Kotaro Satoh Dr. Tor Kit Goh Dr. Anton Blencowe Dr. Kanji Nagai Dr. Kenji Ishitake Dr. Andrew Joseph Christofferson Dr. George Yiapanis Prof. Irene Yarovsky Prof. Masami Kamigaito Prof. Greg Guanghua Qiao 《Angewandte Chemie (International ed. in English)》2014,53(2):459-464
In this study, the stereocomplexation between a novel stereospecific cyclic vinyl polymer, that is, cyclic syndiotactic poly(methyl methacrylate) (st‐PMMA), with the complementary linear isotactic (it‐) PMMA was investigated. Surprising new insight into the effects of the topology (i.e., end groups), size, and tacticity of the assembling components on stereocomplex formation was obtained. Characterization of the stereocomplexes revealed that the self‐assembly of cyclic st‐PMMAs and linear it‐PMMAs resulted in the formation of an unprecedented “polypseudorotaxane‐type” supramolecular assembly. This stereocomplex exhibited remarkably different physical properties as compared to the conventional PMMA triple‐helix stereocomplex as a result of the restricted topology imposed by the cyclic st‐PMMA assembling component. 相似文献
82.
The complete weight enumerator of the Delsarte–Goethals code over Z
4 is derived and an Assmus–Mattson-type approach at identifying t-designs in linear codes over Z
4 is presented. The Assmus–Mattson-type approach, in conjunction with the complete weight enumerator are together used to show that the codewords of constant Hamming weight in both the Goethals code over Z
4 as well as the Delsarte–Goethals code over Z
4 yield 3-designs, possibly with repeated blocks. 相似文献
83.
Rare earth element substituted bismuth ferrites (BiFeO3) are of enormous importance as magnetoelectric materials. The polycrystalline samples of Bi
x
La1−x
FeO3 (x=0, 0.2, 0.4, 0.6, 0.8) were prepared by solid-state reaction using standard ceramic method. The single-phase formation of
these compounds was confirmed by X-ray diffraction (XRD) studies. The samples with x=0, 0.2, 0.4, 0.6 are found to be orthorhombic while the sample with x=0.8 is triclinic. The dielectric constant (ε′) and dissipation factor (tan δ) were measured in the frequency range 100 Hz
to 1 MHz at room temperature and as a function of temperature at certain fixed frequencies (1 kHz, 10 kHz, 100 kHz, 1 MHz).
All the samples showed dielectric dispersion. The dielectric constant with temperature shows a broad peak; the peak temperature
shifts with frequency which reflects the relaxor-type behavior. The peak above 600 K in the measured temperature range corresponds
to antiferromagnetic ordering temperature (Néel temperature). The broadness of the peak changes with composition. The ac conductivity
as well as ε′ are found to be maximum for the sample x=0.2 at room temperature. 相似文献
84.
85.
86.
Influence of volatile chlorides on the molten salt synthesis of ternary oxide nanorods and nanoparticles 总被引:1,自引:0,他引:1
Rørvik PM Lyngdal T Saeterli R van Helvoort AT Holmestad R Grande T Einarsrud MA 《Inorganic chemistry》2008,47(8):3173-3181
A molten salt synthesis route, previously reported to yield BaTiO3, PbTiO3, and Na2Ti6O13 nanorods, has been re-examined to elucidate the role of volatile chlorides. A precursor mixture containing barium (or lead) and titanium was annealed in the presence of NaCl at 760 or 820 degrees C. The main products were respectively isometric nanocrystalline BaTiO3 and PbTiO3. Nanorods were also detected, but electron diffraction revealed that the composition of the nanorods was respectively BaTi2O5/BaTi5O11 and Na2Ti6O13 for the two different systems, in contradiction to the previous studies. It was shown that NaCl reacted with BaO (PbO) resulting in loss of volatile BaCl2 (PbCl2) and formation and preferential growth of titanium oxide-rich nanorods instead of the target phase BaTiO3 (or PbTiO3). The molten salt synthesis route may therefore not necessarily yield nanorods of the target ternary oxide as reported previously. In addition, the importance of NaCl(g) for the growth of nanorods below the melting point of NaCl was demonstrated in a special experimental setup, where NaCl and the precursors were physically separated. 相似文献
87.
A standard Cholesky decomposition of the two-electron integral matrix leads to integral tables which have a huge number of very small elements. By neglecting these small elements, it is demonstrated that the recursive part of the Cholesky algorithm is no longer a bottleneck in the procedure. It is shown that a very efficient algorithm can be constructed when family type basis sets are adopted. For subsequent calculations, it is argued that two-electron integrals represented by Cholesky integral tables have the same potential for simplifications as density fitting. Compared to density fitting, a Cholesky decomposition of the two-electron matrix is not subjected to the problem of defining an auxiliary basis for obtaining a fixed accuracy in a calculation since the accuracy simply derives from the choice of a threshold for the decomposition procedure. A particularly robust algorithm for solving the restricted Hartree-Fock (RHF) equations can be speeded up if one has access to an ordered set of integral tables. In a test calculation on a linear chain of beryllium atoms, the advocated RHF algorithm nicely converged, but where the standard direct inversion in iterative space method converged very slowly to an excited state. 相似文献
88.
Schafer D Gibson EA Amir W Erikson R Lawrence J Vestad T Squier J Jimenez R Marr DW 《Optics letters》2007,32(17):2568-2570
Two-photon absorption fluorescence is employed within a microfluidic device to create a three-dimensional chemical concentration map for mixing uniformity characterization. This multiphoton technique images fluorescence intensity directly and provides a simple, rapid, and readily employed route to composition characterization within microfluidic systems. 相似文献
89.
Knowledge of the local polarity of specific cavities in biopolymers can facilitate the design of selective low MW ligands that impact the structure and function of macromolecules. The most common tools for interrogating local polarity are fluorescent probes that are sensitive to their microenvironment. Researchers often evaluate and express this local polarity using dielectric constants, a parameter that reflects an inherent bulk property. A more appropriate expression should take into account solvent-solute interactions at the molecular level. Reevaluation of commonly used fluorophores illustrates the improved correlation between observed Stokes shift changes and E(T)(30) values as compared to the corresponding dielectric constants. 相似文献
90.
Liu L. Loh N. H. Tay B. Y. Tor S. B. Yin H. Q. Qu X. H. 《Applied Physics A: Materials Science & Processing》2011,103(4):1145-1151
Micro powder injection molding (μPIM) has been developed as a potential technique for mass production of microcomponents in microsystems due to its shaping
complexity at low cost, in which sintering is a crucial step to dictate the final properties of the microcomponents. In this
paper, final-stage sintering behavior of 316L stainless steel microsize structures prepared by μPIM, φ100 μm and φ60 μm, respectively, was studied. The effect of size reduction in the regime of micrometers on the density of various microsize
structures was investigated. Sintering kinetics of the microsize structures of φ100 μm and φ60 μm were studied based on particle level sintering models. It is found that the microsize structures of φ60 μm had higher density than the microsize structures of φ100 μm given the same sintering condition. The results indicate that size reduction in the regime of micrometers facilitated
densification of microsize structures. The grain growth mechanism of microsize structures varied with size. Whereas the grain
growth of the microsize structures of φ100 μm is governed by surface-diffusion-controlled pore drag, the grain growth of the microsize structures of φ60 μm is controlled by boundary diffusion. During densification, the microsize structures, φ100 μm and φ60 μm, are both controlled by lattice diffusion. The corresponding activation energies are reported in the paper. 相似文献