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排序方式: 共有93条查询结果,搜索用时 31 毫秒
71.
Colette Deschamps-Vallet Jean-Baptiste Ilotse Michèle Meyer-Dayan Darius Molho 《Tetrahedron letters》1979,20(13):1109-1112
Easy conversion of isoflavylium salts into 2-arylbenzofurans under mild perhydrol oxidation conditions suggests an alternative biogenetic pathway. 相似文献
72.
Lanthanide salt induced shifts in the NMR spectra of phenols are found to increase in basic media. The empirical relationships governing the interaction of phenolic hydroxyl groups, reported earlier, still apply. 相似文献
73.
Sequences of carefully timed and shaped optical pulses provide femtosecond snapshots of molecular structure as well as electronic and vibrational dynamical processes, in analogy with multidimensional NMR. We apply a genetic learning algorithm towards the design of pulse sequences which simplify the multidimensional signals by controlling the relative intensities of various peaks. Numerical simulations demonstrate how poorly resolved weak features may be amplified and observed by using optimized optical pulses, specifically shaped to achieve a desired spectroscopic target. 相似文献
74.
Transient absorption spectroscopy was used to investigate the dynamics of the photochromic indolinobenzospiropyran reaction in toluene solution and in phosphatidylcholine bilayers (1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)). After excitation with UV light, colorless (R/S)-2-(3',3'-dimethyl-6-nitro-3'H-spiro[chromene-2,2'-indol]-1'-yl)ethanol derivatives are converted to colored merocyanine products in high yield; Phi = 0.45 in DMPC liposomes. We find that the reaction occurs in the bilayer aliphatic region in the gel (P(beta)(')) and liquid (L(alpha)) phases. The Arrhenius activation energy for the isomerization in DMPC bilayers was approximately 3.5 times larger in the liquid phase (L(alpha), E(a) = 26.0 +/- 1.0 kJ mol(-1)) than that in the gel phase (P(beta)('), E(a) = 7.3 +/- 1.6 kJ mol(-1)). Analysis of the isomerization rate constant temperature dependence allows an estimation of the bilayer viscosity and free volume properties in the L(alpha) phase. 相似文献
75.
Corbeil CR Englebienne P Yannopoulos CG Chan L Das SK Bilimoria D L'heureux L Moitessier N 《Journal of chemical information and modeling》2008,48(4):902-909
HCV NS5B polymerase is a validated target for the treatment of hepatitis C, known to be one of the most challenging enzymes for docking programs. In order to improve the low accuracy of existing docking methods observed with this challenging enzyme, we have significantly modified and updated F itted 1.0, a recently reported docking program, into F itted 1.5. This enhanced version is now applicable to the virtual screening of compound libraries and includes new features such as filters and pharmacophore- or interaction-site-oriented docking. As a first validation, F itted 1.5 was applied to the testing set previously developed for F itted 1.0 and extended to include hepatitis C virus (HCV) polymerase inhibitors. This first validation showed an increased accuracy as well as an increase in speed. It also shows that the accuracy toward HCV polymerase is better than previously observed with other programs. Next, application of F itted 1.5 to the virtual screening of the Maybridge library seeded with known HCV polymerase inhibitors revealed its ability to recover most of these actives in the top 5% of the hit list. As a third validation, further biological assays uncovered HCV polymerase inhibition for selected Maybridge compounds ranked in the top of the hit list. 相似文献
76.
Lithuanian Mathematical Journal - We prove that every collection of analytic functions (f1(s), . . . , fr(s)) defined on the right-hand side of the critical strip can be simultaneously approximated... 相似文献
77.
Darius Vrubliauskas Christopher D. Vanderwal 《Angewandte Chemie (International ed. in English)》2020,59(15):6115-6121
A novel CoII‐catalyzed polyene cyclization was developed that is uniquely effective when performed in hexafluoroisopropanol as the solvent. The process is presumably initiated by metal‐catalyzed hydrogen‐atom transfer (MHAT) to 1,1‐disubstituted or monosubstituted alkenes, and the reaction is remarkable for its tolerance of internal alkenes bearing either electron‐rich methyl or electron‐deficient nitrile substituents. Electron‐rich aromatic terminators are required in both cases. Terpenoid scaffolds with different substitution patterns are obtained with excellent diastereoselectivities, and the bioactive C20‐oxidized abietane diterpenoid carnosaldehyde was made to showcase the utility of the nitrile‐bearing products. Also provided are the results of several mechanistic experiments that suggest the process features an MHAT‐induced radical bicyclization with late‐stage oxidation to regenerate the aromatic terminator. 相似文献
78.
Darius K. Deak Robert W. Lenz Simon W. Kantor 《Journal of polymer science. Part A, Polymer chemistry》1997,35(2):197-209
Three series of aromatic, thermotropic copolyesters, based on terephthalic acid (TA), ethylene glycol (EG), and another diol were prepared. The third monomer was selected from three different hydroquinones including, ethoxyhydroquinone (EHQ), phenylhydroquinone (PHQ), and hydroquinone itself (HQ). The amounts of the different hydroquinone terephthalate units were varied while the amounts of ethylene terephthalate units remained constant. The copolymers and terpolymers were characterized for solubility, for morphology by polarized light microscopy (PLM), for molecular weight by solution viscometry, and by NMR, DSC, and TGA. At elevated temperatures all samples, when observed by PLM, displayed the characteristic texture of a nematic phase. The melting transition temperatures, Tm, were found to vary from 255 to 325°C, while the 5 wt % loss temperatures, Td, were found to vary from 330 to 440°C. The inherent viscosities varied from 0.6 to 1.9 dL/g. Increases in the HQ monomer content caused a decreased solubility and an increase in melting point. Copolymer compositions determined by NMR showed that only about one-half of the EG added was incorporated into the copolymers. © 1997 John Wiley & Sons, Inc. 相似文献
79.
为了能够高效计算非线性光学响应函数,提出了级联方程组的混合海森堡-薛定谔方案以及块矩阵操作方法. 同时,这些方法也与最近发展的级联方程组的最优构建和过滤传播子相结合, 模拟了不同光学四波混频配置下激子二聚体模型体系的相干二维光谱,重点研究了其中分子间转移耦合和激子{激子相互作用的影响. 相似文献
80.
Dalia Jonynaite Darius Jasaitis Rimantas Raudonis Algirdas Selskis Remigijus Juskenas Jurate Senvaitiene Aivaras Kareiva 《Central European Journal of Chemistry》2012,10(5):1574-1583
In the present work, the formation of cobalt aluminium spinel (CoAl2O4) as well as novel cobalt neodymium-aluminates with nominal compositions of CoAl1.75Nd0.25O4, CoAl1.5Nd0.5O4 and CoAlNdO4 by an aqueous sol-gel process and the sinterability of the products are investigated. The metal ions, generated by dissolving
starting materials of metals in the diluted acetic acid were complexed by 1,2-ethanediol to obtain the precursors for the
mixed metal ceramics. The phase purity of the synthesized compounds was characterized by powder X-ray diffraction analysis
and infrared spectroscopy. The microstructural evolution and morphological features of the products were studied by scanning
electron microscopy and atomic force microscopy, which together with the optical characterization of these new compounds showed
that the sol-gel-derived materials could be successfully used as effective cobalt-based ceramic pigments.
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