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排序方式: 共有128条查询结果,搜索用时 15 毫秒
61.
62.
Verschooten L Claerhout S Van Laethem A Agostinis P Garmyn M 《Photochemistry and photobiology》2006,82(4):1016-1023
Adequate photoprotection is essential to control UV-related disorders, including sunburn, photoaging and photocarcinogenisis. Sun avoidance, protection of skin with clothing, and sunscreens are presently the best way of photoprotection, assuming that they are used properly. However, new strategies, which are based on or make use of the endogenous protective response to UV light, may further improve currently used photoprotective means. The addition of repair enzymes and/or antioxidants has a positive effect on skin's recovery from UV-induced DNA-damage. Several botanical agents, mainly vitamins and polyphenols, have shown to influence signal transduction pathways leading to photoprotective effects. Also stimulation of endogenous UV-response pathways via irradiation with a low UV dose or via simulation of UV-induced DNA-damage results in photoprotective effects. Future research in this field and combination of different photoprotective strategies will hopefully lead to improved photoprotection. 相似文献
63.
Herrebout WA Delanoye SN Maes BU van der Veken BJ 《The journal of physical chemistry. A》2006,110(51):13759-13768
Infrared spectra of solutions of trifluoroethene and dimethyl ether, acetone, or oxirane in liquid krypton and liquid argon have been studied. For each Lewis base the formation of a 1:1 complex with the Lewis acid was observed. The C-H stretching of trifluoroethene being perturbed by a strong Fermi resonance, the complexes with trifuloroethene-d were also investigated and showed that in each case the hydrogen bond between the acid and base is of the traditional, red-shifting type. The structures of the complexes were investigated using ab initio calculations. These indicate that with dimethyl ether and acetone two different isomeres can be formed, but with a single one detected in the solution in each case. The Fermi resonance in the complex with unlabeled trifluoroethene is discussed using data derived form ab initio potential and dipole hypersurface calculations. The complexation enthalpies of the complexes were obtained from temperature dependent studies of the solutions and are discussed in relation to the ab initio complexation energies and Monte Carlo free energy perturbation calculations of solvent effects. 相似文献
64.
The reaction of the N-methylpyrrolidin-2-one hydrotribromide complex (MPHT) with substituted-1-tetralones has been investigated. This safety reagent proved to be successful for selective α,α-dibromination of tetralones. Moreover, under base-free conditions, several 2-bromo-1-naphtols were obtained from tetralones in a ‘one pot’ sequence in good to excellent yields. 相似文献
65.
Patrick Bultinck Sofie Van Damme Andrés Cedillo 《Journal of computational chemistry》2013,34(28):2421-2429
Bond Fukui functions and matrices are introduced for ab initio levels of theory using a Mulliken atoms in molecules model. It is shown how these indices may be obtained from first‐order density matrix derivatives without need for going to second‐order density matrices as in a previous work. The importance of taking into account the nonorthogonality of the basis in ab initio calculations is shown, contrasting the present results with previous work based on Hückel theory. It is shown how the extension of Fukui functions to Fukui matrices allows getting more insight into the nature of bond Fukui functions. All presently introduced indices respect the necessary normalization conditions and include the classical single atom condensed Fukui functions. © 2013 Wiley Periodicals, Inc. 相似文献
66.
Xavier Bekaert Marc Henneaux Alexander Sevrin 《Communications in Mathematical Physics》2001,224(3):683-703
We systematically study deformations of chiral forms with applications to string theory in mind. To first order in the coupling
constant, this problem can be translated into the calculation of the local BRST cohomological group at ghost number zero.
We completely solve this cohomology and present detailed proofs of results announced in a previous letter. In particular,
we show that there is no room for non-abelian, local, deformations of a pure system of chiral p-forms.
Received: 17 April 2000 / Accepted: 13 July 2001 相似文献
67.
68.
Frontispiece: Distinct Spacing Between Anionic Groups: An Essential Chemical Determinant for Achieving Thiophene‐Based Ligands to Distinguish β‐Amyloid or Tau Polymorphic Aggregates 下载免费PDF全文
69.
Asymmetric γ‐Allylation of α,β‐Unsaturated Aldehydes by Combined Organocatalysis and Transition‐Metal Catalysis 下载免费PDF全文
Line Næsborg Kim Søholm Halskov Dr. Fernando Tur Sofie M. N. Mønsted Prof. Dr. Karl Anker Jørgensen 《Angewandte Chemie (International ed. in English)》2015,54(35):10193-10197
The first asymmetric regio‐ and diastereodivergent γ‐allylation of cyclic α,β‐unsaturated aldehydes based on combined organocatalysis and transition‐metal catalysis is disclosed. By combining an aminocatalyst with an iridium catalyst, both diastereomers of branched allylated products can be achieved in moderate to good yields and excellent regio‐ and stereoselectivities. Furthermore, by replacing the iridium catalyst with a palladium catalyst, the linear allylated products are formed in good yields and excellent regio‐ and enantioselectivities. The developed method thus provides selective access to all six isomers of the γ‐allylated product in a divergent fashion by choosing the appropriate combination of organocatalyst, transition‐metal catalyst, and ligand. 相似文献
70.
A new computer program has been designed to build and analyze quantitative-structure activity relationship (QSAR) models through regression analysis. The user is provided with a range of regression and validation techniques. The emphasis of the program lies mainly in the validation of QSAR models in chemical applications. ARTE-QSAR produces an easy interpretable output from which the user can conclude if the obtained model is suitable for prediction and analysis. 相似文献