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91.
92.
Chiara Di Berardino Marcel A. Strauss Dominic Schatz Prof. Dr. Hermann A. Wegner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(12):e202104284
Predictive models based on incremental systems exist for many chemical phenomena, thus allowing easy estimates. Despite their low magnitude in isolated systems London dispersion interactions are ubiquitous in manifold situations ranging from solvation to catalysis or in biological systems. Based on our azobenzene system, we systematically determined the London dispersion donor strength of the alkyl substituents Me, Et, iPr up to tBu. Based on this data, we were able to implement an incremental system for London dispersion for the azobenzene scheme. We propose an equation that allows the prediction of the effect of change of substituents on London dispersion interactions in azobenzenes, which has to be validated in similar molecular arrangements in the future. 相似文献
93.
Qi Wang Yaomi Itoh Tohru Tsuruoka Shintaro Ohtsuka Tomohiro Shimizu Shoso Shingubara Tsuyoshi Hasegawa Masakazu Aono 《固体物理学:研究快报》2015,9(3):166-170
ReRAMs using oxygen vacancy drift in their resistive switching are promising candidates as next generation memory devices. One remaining issue is degradation of the on/off ratio down to 102 or less with an increased number of switching cycles. Such degradation is caused by a local hard breakdown in a set process due to a very high electric field formed just before the completion of a conductive filament formation. We found that introducing an ultra‐thin SiO2 layer prevents the hard breakdown by dynamical moderation of the electric field formed in the TaOx matrix, resulting in repeated switching while retaining a higher on/off ratio of about 105. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
94.
Regime-switching models can be used to describe stochastic movements of electricity prices in deregulated markets. This paper shows that regime-switching dynamics arise quite naturally in an equilibrium context in which the functional form of the supply curve is described by a two-state Markov process. This mechanism is responsible for random switches between regimes and it allows one to describe the main features of the price-formation process. With the interplay between demand and supply, the proposed methodology can be used to capture shortages in electricity generation, forced outages, and peaks in electricity demand. As an example of application, a two-regime model specification is proposed, and it will be shown that the empirical analysis, performed by estimating using the model on the California power market, offers an interesting agreement with observed data. 相似文献
95.
In this paper, we consider the following delayed Leslie-Gower predator-prey system
(∗) 相似文献
96.
Wenjie Liu Dr. Derong Cao Prof. Dr. Jinan Peng Hong Zhang Herbert Meier Prof. Dr. 《化学:亚洲杂志》2010,5(8):1896-1901
A series of Fréchet‐type dendrimers with 9‐benzyloxymethylanthracene cores were synthesized and characterized. The chiral source for the dendrimers was an (S)‐2‐methyl‐1‐butoxy group in the 3‐position of the benzene ring. Irradiation at 366 nm of a dilute benzene solution led to the formation of two diastereomers (1:1) through a quantitative intramolecular [4π+4π] cycloaddition between the central anthracene ring and the neighboring benzene ring. The process can be reversed with 254 nm UV light or heat. The benzene rings in the dendrons work as a light‐harvesting system. The optical rotation values measured for the reversible process showed fatigue resistance. Thus, a promising new type of chiroptical switch has been created that has optical rotation values as output signals. 相似文献
97.
《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(1):369-385
A range of covalently linked donor–acceptor compounds which contain 1) a hydroquinone (HQ) unit, 2) a 1,5‐dioxynaphthalene (DNP) ring system, or 3) a tetrathiafulvalene (TTF) unit as the π‐donor, and 4) cyclobis(paraquat‐p‐phenylene) (CBPQT4+) as the π‐accepting tetracationic cyclophane were prepared and shown to operate as simple molecular machines. The π‐donating arms can be included inside the cyclophane in an intramolecular fashion by virtue of stabilizing noncovalent bonding interactions. What amounts to self‐complexing/decomplexing equilibria were shown to be highly temperature dependent when the π‐donating arm contains either an HQ or DNP moiety. The thermodynamic parameters associated with the equilibria have been unraveled by using variable‐temperature 1H NMR spectroscopy. The negative ΔH° and ΔS° values account for the fact that the “uncomplexed” conformation becomes the dominant species, since the entropy gain associated with the decomplexation process overcomes the enthalpy loss resulting from the breaking of the donor–acceptor interactions. The arm's in‐and‐out movements with respect to the linked cyclophanes can be arrested by installing a bulky substituent at the end of the arm. In the case of compounds carrying a DNP ring system in their side arm, two diastereoisomeric, self‐complexing conformations are observed below 272 K in hexadeuterioacetone. By contrast, control over the TTF‐containing arm's movement is more or less ineffective through the thermally sensitive equilibrium although it can be realized by chemical and electrochemical ways as a result of TTF's excellent redox properties. Such self‐complexing compounds could find applications as thermo‐ and electroswitches. In addition, the thermochromism associated with the arm's movement could lead to some of the compounds finding uses as imaging and sensing materials. 相似文献
98.
(Eta6-arene)tricarbonylchromium 2 was synthesised by [3+2+1] benzannulation of the Fischer carbene complex 1 and converted to the thermodynamically more favorable regioisomer 3 by haptotropic metal migration. Photo-induced ligand-exchange reactions in both regioisomers with triphenylphosphine, triphenylphosphite, trimethylphosphine, and trimethylphosphite afforded dicarbonyl(phosphine or phosphite)arene complexes 4-11. The regioisomers were separated by high-performance liquid chromatography (HPLC), and kinetic analyses of the thermo-induced haptotropic metal shift were performed with regioisomers 4, 6, 8, and 10. The kinetic parameters were compared with those obtained for the parent tricarbonyl complex 2 and were discussed in terms of the steric and electronic properties of the phosphorus ligands by applying a quantitative analysis of ligand effects (QALE). The molecular structures of regioisomeric PPh3 and P(OPh)3 complexes 4/5 and 6/7 as well as of P(OMe)3 complex 10 have been established by single-crystal X-ray analysis. 相似文献
99.
Benjamin J. Coe Stephan Houbrechts Inge Asselberghs Andr Persoons 《Angewandte Chemie (International ed. in English)》1999,38(3):366-369
Low‐energy metal‐to‐ligand charge‐transfer (MLCT) excitations are associated with the very large molecular nonlinear optical (NLO) coefficients, β, of the complexes [RuII(NH3)5(N‐R‐4,4′‐bipyridinium)]3+ (R=methyl, phenyl, or 4‐acetylphenyl). Chemical oxidation to the RuIII forms causes bleaching of the MLCT absorptions and marked attenuation of the NLO responses. Both effects are completely reversed upon re‐reduction, and the extent of the β switching is about 10‐ to 20‐fold. 相似文献
100.
本文首先指出了采用电压信号的多值电路中,在多个开关串联时存在的问题,进而提出了适合于ECL电路设计的两种将串联开关转换成并联开关的方法,并具体设计了采用并联开关的三值ECL电路。设计实例表明这些方法具有简便、规范的特点。用PSPICE对设计的电路进行模拟得到的结果表明,采用并联开关技术设计的电路不仅具有正确的逻辑功能,而且比采用串联开关设计的电路具有更快的速度。 相似文献