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排序方式: 共有257条查询结果,搜索用时 15 毫秒
201.
O. M. Denysenko 《Nonlinear Oscillations》2007,10(2):181-202
We consider a one-dimensional stationary quasiperiodic Schrödinger equation with analytic potential. Using methods of the KAM theory, we construct the boundaries of instability zones and solutions corresponding to these boundaries and estimate the sizes of instability zones. In addition, we consider the case where the potential is a trigonometric polynomial of finite degree. 相似文献
202.
Chemical and Structural Stability of Zirconium‐based Metal–Organic Frameworks with Large Three‐Dimensional Pores by Linker Engineering
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Dr. Suresh B. Kalidindi Dr. Sanjit Nayak Dr. Michael E. Briggs Dr. Susanna Jansat Dr. Alexandros P. Katsoulidis Dr. Gary J. Miller Dr. John E. Warren Dr. Dmytro Antypov Dr. Furio Corà Dr. Ben Slater Dr. Mark R. Prestly Dr. Carlos Martí‐Gastaldo Prof. Matthew J. Rosseinsky 《Angewandte Chemie (International ed. in English)》2015,54(1):221-226
The synthesis of metal–organic frameworks with large three‐dimensional channels that are permanently porous and chemically stable offers new opportunities in areas such as catalysis and separation. Two linkers (L1=4,4′,4′′,4′′′‐([1,1′‐biphenyl]‐3,3′,5,5′‐tetrayltetrakis(ethyne‐2,1‐diyl)) tetrabenzoic acid, L2=4,4′,4′′,4′′′‐(pyrene‐1,3,6,8‐tetrayltetrakis(ethyne‐2,1‐diyl))tetrabenzoic acid) were used that have equivalent connectivity and dimensions but quite distinct torsional flexibility. With these, a solid solution material, [Zr6O4(OH)4(L1)2.6(L2)0.4]?(solvent)x, was formed that has three‐dimensional crystalline permanent porosity with a surface area of over 4000 m2 g?1 that persists after immersion in water. These properties are not accessible for the isostructural phases made from the separate single linkers. 相似文献
203.
Dmytro Kostiuk Michal Bodik Peter Siffalovic Matej Jergel Yuriy Halahovets Martin Hodas Marco Pelletta Michal Pelach Martin Hulman Zdenko Spitalsky Maria Omastova Eva Majkova 《Journal of Raman spectroscopy : JRS》2016,47(4):391-394
We report on a reference‐free Raman spectroscopy method for a precise thickness determination of the multilayered graphene oxide flakes. The method is based on the normalization of the total integral intensity of D and G Raman bands to the integral intensity of the second‐order optical phonon peak of the silicon substrate in the Raman spectrum. The normalization provides discrete ratio values corresponding to the number of graphene oxide layers in the respective flakes with the intensity linearly increasing with the number of layers. This provides a fast and robust determination of the thickness of graphene oxide flakes in terms of the layer number up to high values. A comparison with conventional spectrally resolved reflectivity mapping shows similar sensitivity, while selectivity to particular functional chemical groups is a bonus of the Raman‐based method. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
204.
Dmytro V. Kravtsov Oleksii Yu. Voskoboinik Serhii I. Kovalenko 《Journal of heterocyclic chemistry》2021,58(1):212-225
A series of novel 6-substituted 2-(benzo[4,5]imidazo[1,2-c]quinazolin-5(6H)-yl)acetic acids were synthesized and characterized by 1H, 13C, 19F NMR, 1H-1H-COSY, 1H-13C-HSQC, NOESY, LC-MS, IR, and elemental analysis. The mitotic toxicity of the synthesized compounds was determined according to the Allium test procedure. The 2-(6-(pentafluorophenyl)benzo[4,5]imidazo[1,2-c]quinazolin-5(6H)-yl)acetic acid inhibited mitotic spindle formation, which resulted in significant cytotoxic effect for meristematic cells of Allium cepa l . roots. In a preliminary antimicrobial evaluation, only Streptococcus pyogenes and Candida albicans were slightly susceptible to some of the synthesized compounds. 相似文献
205.
Pablo Baudin Dmytro Bykov Dmitry Liakh Patrick Ettenhuber Kasper Kristensen 《Molecular physics》2017,115(17-18):2135-2144
ABSTRACTThe recently developed Local Framework for calculating Excitation energies (LoFEx) is extended to the coupled cluster singles and doubles (CCSD) model. In the new scheme, a standard CCSD excitation energy calculation is carried out within a reduced excitation orbital space (XOS), which is composed of localised molecular orbitals and natural transition orbitals determined from time-dependent Hartree–Fock theory. The presented algorithm uses a series of reduced second-order approximate coupled cluster singles and doubles (CC2) calculations to optimise the XOS in a black-box manner. This ensures that the requested CCSD excitation energies have been determined to a predefined accuracy compared to a conventional CCSD calculation. We present numerical LoFEx-CCSD results for a set of medium-sized organic molecules, which illustrate the black-box nature of the approach and the computational savings obtained for transitions that are local compared to the size of the molecule. In fact, for such local transitions, the LoFEx-CCSD scheme can be applied to molecular systems where a conventional CCSD implementation is intractable. 相似文献
206.
Kristina Karal Martin Bollmark Rouven Stulz Dmytro Honcharenko Ulf Tedebark Roger Strmberg 《Molecules (Basel, Switzerland)》2021,26(22)
2′-O-(N-(Aminoethyl)carbamoyl)methyl-modified 5-methyluridine (AECM-MeU) and 5-methylcytidine (AECM-MeC) phosphoramidites are reported for the first time and prepared in multigram quantities. The syntheses of AECM-MeU and AECM-MeC nucleosides are designed for larger scales (approx. 20 g up until phosphoramidite preparation steps) using low-cost reagents and minimizing chromatographic purifications. Several steps were screened for best conditions, focusing on the most crucial steps such as N3 and/or 2′-OH alkylations, which were improved for larger scale synthesis using phase transfer catalysis (PTC). Moreover, the need of chromatographic purifications was substantially reduced by employing one-pot synthesis and improved work-up strategies. 相似文献
207.
Sara Janowska Dmytro Khylyuk Agnieszka Gornowicz Anna Bielawska Micha Janowski Robert Czarnomysy Krzysztof Bielawski Monika Wujec 《Molecules (Basel, Switzerland)》2022,27(20)
Based on the results of previous work, we designed and synthesized 1,3,4-thiadiazole derivatives. The cytotoxic activity of the obtained compounds was then determined in biological studies using MCF-7 and MDA-MB-231 breast cancer cells and a normal cell line (fibroblasts). The results showed that all compounds displayed weak anticancer activity towards two breast cancer lines: an estrogen-dependent cell line (MCF-7) and an estrogen-independent cell line (MDA-MB-231). The compound most active towards MCF-7 breast cancer cells was SCT-4, which decreased DNA biosynthesis to 70% ± 3 at 100 µM. The mechanism of the anticancer action of 1,3,4-thiadiazole was also investigated. We choose a set of the most investigated proteins, which are attractive anticancer targets. In silico studies demonstrated a possible multitarget mode of action for the synthesized compounds but the most likely mechanism of action for the new compounds is connected with the activity of caspase 8. 相似文献
208.
Yana I. Sakhno Anton V. Kozyryev Sergey M. Desenko Svetlana V. Shishkina Vladimir I. Musatov Dmytro O. Sysoiev Valentin A. Chebanov 《Tetrahedron》2018,74(5):564-571
Three-component heterocyclizations of pyruvic acids and their esters with 5-aminopyrazoles and aromatic aldehydes, in addition to the sequential versions of these reactions, under different activating conditions were studied. Under conventional heating, pyrazolopyrimidine derivatives containing a hydroxyl group in the 6-position were formed in both two- and three-component treatments. Whereas the application of an inert atmosphere did not influence the outcome of these reactions, the use of ultrasonic irradiation led to the formation of 7-hydroxy-tetrahydropyrazolopyrimidines in multi-component reactions and 6-hydroxy-dihydropyrazolopyrimidines in the case of a step-by-step approach. The products of the latter treatment were further transformed into heteroaromatized 6-hydroxy-pyrazolopyrimidines by conventional heating. 相似文献
209.
Dr. Galyna Sych Dr. Ramin Pashazadeh Dr. Yan Danyliv Dr. Oleksandr Bezvikonnyi Dr. Dmytro Volyniuk Dr. Algirdas Lazauskas Prof. Juozas V. Grazulevicius 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(8):2826-2836
Three new quinoline and di-tert-butyl phenothiazine isomeric derivatives were synthesized and characterized towards applications for oxygen sensing and optical information multicoding. The compounds with phenylene linker showed outstanding phase-dependent reversibility between ON/OFF states (low and high emission intensity, drastic shifting of emission colors, short- and long-lived fluorescence) in systematic grinding/fuming cycles, as required for multichannel memory devices based on optical information multicoding. The conformational diversity of the phenothiazine unit resulted in dual emission of the doped films implemented by the different luminescence mechanisms with peaks located at 414/530, 416/540, and 440/582 nm. The presence of a phenylene linker and thus two rotational degrees of freedom resulted in quenching of the delayed fluorescence of quasi-equatorial conformers in the solid state. The compound containing no phenylene bridge was characterized by two different driving photoluminescence mechanisms of the doped films: short fluorescence of the quasi-axial conformer and thermally activated delayed fluorescence of the quasi-equatorial form. This compound showed oxygen sensitivity with a Stern–Volmer constant of 7.5×10−4 ppm−1. 相似文献
210.
Ghosh D Kosenkov D Vanovschi V Williams CF Herbert JM Gordon MS Schmidt MW Slipchenko LV Krylov AI 《The journal of physical chemistry. A》2010,114(48):12739-12754
The implementation of the effective fragment potential (EFP) method within the Q-CHEM electronic structure package is presented. The EFP method is used to study noncovalent π-π and hydrogen-bonding interactions in DNA strands. Since EFP is a computationally inexpensive alternative to high-level ab initio calculations, it is possible to go beyond the dimers of nucleic acid bases and to investigate the asymptotic behavior of different components of the total interaction energy. The calculations demonstrated that the dispersion energy is a leading component in π-stacked oligomers of all sizes. Exchange-repulsion energy also plays an important role. The contribution of polarization is small in these systems, whereas the magnitude of electrostatics varies. Pairwise fragment interactions (i.e., the sum of dimer binding energies) were found to be a good approximation for the oligomer energy. 相似文献