全文获取类型
收费全文 | 375篇 |
免费 | 13篇 |
专业分类
化学 | 329篇 |
晶体学 | 1篇 |
力学 | 4篇 |
数学 | 18篇 |
物理学 | 36篇 |
出版年
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 7篇 |
2020年 | 10篇 |
2019年 | 8篇 |
2018年 | 6篇 |
2017年 | 7篇 |
2016年 | 10篇 |
2015年 | 7篇 |
2014年 | 8篇 |
2013年 | 17篇 |
2012年 | 29篇 |
2011年 | 30篇 |
2010年 | 26篇 |
2009年 | 12篇 |
2008年 | 28篇 |
2007年 | 30篇 |
2006年 | 33篇 |
2005年 | 28篇 |
2004年 | 21篇 |
2003年 | 16篇 |
2002年 | 16篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1974年 | 1篇 |
1965年 | 2篇 |
排序方式: 共有388条查询结果,搜索用时 15 毫秒
331.
332.
Five novel compounds, applanatines A-E (1-5), and a known one (6) were isolated from the culture broth of Ganoderma applanatum. Their structures including the relative configurations were determined by the interpretation of spectroscopic data. Compounds 3 and 4 suppressed the growth of Fusobacterium nucleatum, that is, a prominent member of the oral microflora implicated in periodontitis. 相似文献
333.
The solvent-free Horner-Wadsworth-Emmons reaction with a variety of aldehydes using 1.5 equiv of DBU gave E-α,β-unsaturated esters and ketones in high yields. The E-selectivity was high and the used DBU was recovered. 相似文献
334.
The tensor interaction plays an important role to determine the nuclear structure. In this study, we propose a tensor-optimized few-body model (TOFM) in the few body framework with bare nucleon-nucleon interaction. In TOFM, the configurations caused by the one-operation of the tensor operator to the S-wave ground state are introduced in the total wave function. It is shown that TOFM reproduces more than 90 % of the total binding energy and the tensor correlation of the few-body results for s-shell nuclei. We further apply TOFM to the p-shell, as 5He. We work out the variational calculation for 5He and discuss the structure difference between two resonance states 3/2? and 1/2?. In particular, we shed light on the roles of the tensor interaction in two states, such as the LS splitting energy. 相似文献
335.
Amari S Aizawa M Zhang J Fukuzawa K Mochizuki Y Iwasawa Y Nakata K Chuman H Nakano T 《Journal of chemical information and modeling》2006,46(1):221-230
We have developed a visualized cluster analysis of protein-ligand interaction (VISCANA) that analyzes the pattern of the interaction of the receptor and ligand on the basis of quantum theory for virtual ligand screening. Kitaura et al. (Chem. Phys. Lett. 1999, 312, 319-324.) have proposed an ab initio fragment molecular orbital (FMO) method by which large molecules such as proteins can be easily treated with chemical accuracy. In the FMO method, a total energy of the molecule is evaluated by summation of fragment energies and interfragment interaction energies (IFIEs). In this paper, we have proposed a cluster analysis using the dissimilarity that is defined as the squared Euclidean distance between IFIEs of two ligands. Although the result of an ordered table by clustering is still a massive collection of numbers, we combine a clustering method with a graphical representation of the IFIEs by representing each data point with colors that quantitatively and qualitatively reflect the IFIEs. We applied VISCANA to a docking study of pharmacophores of the human estrogen receptor alpha ligand-binding domain (57 amino acid residues). By using VISCANA, we could classify even structurally different ligands into functionally similar clusters according to the interaction pattern of a ligand and amino acid residues of the receptor protein. In addition, VISCANA could estimate the correct docking conformation by analyzing patterns of the receptor-ligand interactions of some conformations through the docking calculation. 相似文献
336.
Ando K 《The Journal of organic chemistry》2006,71(5):1837-1850
Transition structures for the lithium-bromine exchange reaction of 1,1-dibromoalkenes with methyllithium have been located by both the B3LYP and the MP2 levels of theory with the 6-31+G basis set. The reaction with methyllithium dimer gave similar results with lower activation energies. These calculations predict both the kinetic and the thermodynamic stereoselectivity correctly. That is, the sterically more constrained bromine atom of 1,1-dibromoalkenes was predominantly reacted with alkyllithium (dimer) in the kinetic condition. The intramolecular substitution reaction of 4,4-dibromo-3-methyl-3-pentenol in the presence of methyllithium has been investigated. After deprotonation of the alcohol and the lithium-bromine exchange reaction, the intramolecular substitution reaction occurs to give dihydrofuran in a concerted manner. The intermolecular substitution of alpha-chloro alkenyllithium with methyllithium was also studied for comparison. The formation of the indene derivative from 3-(o-bromophenyl)-1,1-dibromo-1-propene in the presence of methyllithium occurs in a similar manner. The lithium-bromine exchange reaction of bromobenzene with methyllithium occurs in an S(N)2 mechanism and the solvent plays an important role. 相似文献
337.
Rotational dynamics of solvated carbon dioxide (CO(2)) has been studied. The infrared absorption band of the antisymmetric stretch mode in acetonitrile is found to show a non-Lorentzian band shape, suggesting a non-exponential decay of the vibrational and/or rotational correlation functions. A combined method of a molecular dynamics (MD) simulation and a quantum chemical calculation well reproduces the observed band shape. The analysis suggests that the band broadening is almost purely rotational, while the contribution from the vibrational dephasing is negligibly small. The non-exponential rotational correlation decay can be explained by a simple rotor model simulation, which can treat large angle rotations of a relatively small molecule. A polarized Raman study of the symmetric stretch mode in acetonitrile gives a rotational bandwidth consistent with that obtained from the infrared analysis. A sub-picosecond time-resolved infrared absorption anisotropy measurement of the antisymmetric stretch mode in ethanol also gives a decay rate that is consistent with the observed rotational bandwidths. 相似文献
338.
Kaori Hayashi Tominari Choshi Kyoko Chikaraishi Aimi Oda Rikako Yoshinaga Noriyuki Hatae Minoru Ishikura Satoshi Hibino 《Tetrahedron》2012,68(22):4274-4279
A new entry to the total synthesis of isocryptolepine (cryptosanguinolentine), isolated from Cryptolepis sanguinolenta, was achieved by constructing a tetracyclic ring system through a microwave-assisted tandem Curtius rearrangement and electrocyclic reaction of an aza 6π-electron system. The tetracyclic lactam was converted to isocryptolepine in a four-step sequence. 相似文献
339.
Shigehito Tanahashi Kaori Segawa Meihong Zheng Junko Kuze Kazuhiko Ukai 《Optical Review》2012,19(5):345-348
The authors examined whether the perceptual reversal rate changes under monocular versus binocular viewing conditions. Our results suggest that the perceptual reversal interval increases during monocular viewing. The ratio of the reversal rate (1/interval) for the two viewing conditions (binocular/monocular) was 1.28 over a wide range of pattern luminance levels. The quoted ratio was 1.40 when the luminance was high. Such a ratio parallels the value of a well-known binocular summation index $(\sqrt 2 )$ , which was derived from the signal detection theory. The binocular summation index shows that the strength of an input signal is enhanced by binocular viewing. However, how the binocular summation shortens the perceptual reversal interval is unclear. This issue can be resolved if the perceptual reversal is derived by integrating the strength of an unconscious image signal. Thus, we discussed the mechanism of perceptual switch by associating two classical, well-studied phenomena, binocular summation and perceptual switch. 相似文献
340.
Taishiro Nakagawa Takashi Ishihara Hideaki Yoshida Takashi Yoneya Kaori Wakamatsu Toshihiko Kadoya 《Journal of separation science》2010,33(14):2045-2051
Accurate prediction of the elution tendency of monoclonal antibodies in column chromatography would be beneficial for the efficient setup of purification procedures. Hydroxyapatite chromatography experiments using 37 recombinant human monoclonal antibodies were performed by sodium chloride gradient elution with 5 mM sodium phosphate to correlate the retention times with antibody structures (subclass and light‐chain isotypes). The contribution of metal affinity interactions in the interaction of antibodies with hydroxyapatite was investigated by (i) eliminating 5 mM sodium phosphate in buffers, (ii) comparing sodium chloride versus sodium phosphate gradient elutions, and (iii) using IgG4 antibodies with a leucine→glutamate mutation. By using antibodies of different subclasses but with identical Fab regions, the elution behavior in sodium chloride elution could be classified by subclass and type of light chain. It is considered that the retention of monoclonal antibodies to hydroxyapatite is affected by the cooperation of phosphoryl cation exchange and metal affinity interactions. The contribution of the metal affinity interactions is greater in the sodium chloride gradient elution method than in the sodium phosphate gradient elution method. 相似文献