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221.
Benzene, halobenzenes and some deactivated arenes readily reacted in anhydrous NaIO4/AcOH/Ac2O/concd. H2SO4 mixtures to afford, after quenching with excess aqueous Na2SO3 solution (a reducing agent), purified iodinated products in 27-88% yields. This novel method of aromatic iodination is simple, fairly effective and environmentally safe. 相似文献
222.
Dual‐Input Regulation and Positional Control in Hybrid Oligonucleotide/Discotic Supramolecular Wires 下载免费PDF全文
Dr. Miguel Ángel Alemán García Eva Magdalena Estirado Dr. Lech‐Gustav Milroy Prof. Dr. Luc Brunsveld 《Angewandte Chemie (International ed. in English)》2018,57(18):4976-4980
The combination of oligonucleotides and synthetic supramolecular systems allows for novel and long‐needed modes of regulation of the self‐assembly of both molecular elements. Discotic molecules were conjugated with short oligonucleotides and their assembly into responsive supramolecular wires studied. The self‐assembly of the discotic molecules provides additional stability for DNA‐duplex formation owing to a cooperative effect. The appended oligonucleotides allow for positional control of the discotic elements within the supramolecular wire. The programmed assembly of these hybrid architectures can be modulated through the DNA, for example, by changing the number of base pairs or salt concentration, and through the discotic platform by the addition of discotic elements without oligonucleotide handles. These hybrid supramolecular‐DNA structures allow for advanced levels of control over 1D dynamic platforms with responsive regulatory elements at the interface with biological systems. 相似文献
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225.
An easy and safe, though only moderately effective method is presented for preparing (diacetoxyiodo)arenes, ArI(OAc)2, from iodoarenes, ArI, using the commercially available and easily handled urea-hydrogen peroxide adduct (UHP) as the oxidant. The reactions take place in anhydrous AcOH/Ac2O/AcONa (a catalyst)mixtures, at 40 oC for 3.5 h to afford the purified ArI(OAc)2 in 37-78% yields. The fully interpreted (1)H- and (13)C-NMR spectra of the ArI(OAc)2 products are reported. 相似文献
226.
The purpose of this paper is to give characterizations of weightsfor which reverse inequalities of Hölder type for quasi-monotonefunctions are satisfied. Our inequalities with general weightsand with sharp constants complement the results of [2, 8, 9]and [16, 17] for the values of parameters p and q with 1pq<. 相似文献
227.
The paper is concerned with order-topological characterizations of topological Riesz spaces, in particular spaces of measurable functions, not containing Riesz isomorphic or linearly homeomorphic copies of or .
228.
Roman Luboradzki Wiktor Kozminski Lech Stefaniak 《Journal of chemical crystallography》1993,23(2):133-141
An X-ray diffraction study is reported for four molecules of mesoionic 2,3-diphenyltetrazoles. The results confirm a dipolar mesoionic structure, aromatic character of the tetrazole ring and no conjugation between the phenyl and tetrazole rings. The geometry of the exocyclic group is discussed in detail. The molecular parameters of the compounds investigated are correlated with13C and15N nmr data. The results obtained are compared with similar structures which have already been studied. 相似文献
229.
Dagmara Jacewicz Dr. Agnieszka Chylewska Aleksandra Da;akbrowska Lech Chmurzyński 《无机化学与普通化学杂志》2007,633(9):1493-1499
Kinetics of the reaction of [tetraamminediaquacobalt(III)] perchlorate ion with carbon dioxide in aqueous solution was studied at various temperatures (5–25 °C), variable concentration of CO2 (0.005M; 0.01M; 0.015M) and over the pH range 6.04–8.15 at a fixed ionic strength of solution (1 M NaClO4). Investigations were carried out using stopped‐flow spectrophotometry in the range of 300 – 700 nm. The results enabled determination of the number of steps of the reaction studied. Based on the kinetic equations, rate constants were determined for each step. Finally, the mechanism of carbon dioxide uptake by [tetraamminediaquacobalt(III)] perchlorate ion was proposed and discussed. 相似文献
230.
Lech Chmurzyski Grayna Wawrzyniak Zygmunt Warnke Zenon Pawlak 《Journal of heterocyclic chemistry》1997,34(1):215-219
The applicability of the direct method of pKa determination in the case of protonated heterocyclic amine N-oxides in a series of polar non-aqueous (aprotic and amphiprotic) solvents has been tested. The method is based on the pH determination of the non-aqueous solution of complex salt (the semiperchlorate in this case) formed by the N-oxides studied. The direct method not only provides for quick (one data point per each pKa determined), but also relatively accurate estimates of acidic dissociation constants. It has been experimentally shown on the example of substituted pyridine N-oxides that this method is precise enough in all studied non-aqueous solvents when applied to compounds of not too low basicity (the pKa being of the order of 5 or higher). To prove this, the pKa values of protonated monocyclic N-oxides obtained by the direct method have been compared with those resulting from the potentiometric titration curve. The agreement between the results found by using both methods is very good in most cases, the differences being within standard deviations. Based upon this observation it can be inferred that the pKa values of protonated bicyclic N-oxides in solvents studied determined by using the direct method can be also considered reliable, especially in the case of polar aprotic solvents. 相似文献