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81.
Mokhtar Benziane Kamel Khimeche Djalal Trache Abdellah Dahmani 《Journal of Thermal Analysis and Calorimetry》2013,114(3):1383-1389
Solid–liquid equilibria for binary mixtures of {methyl stearate (1) + biphenyl (2)}, {methyl stearate (1) + naphthalene (2)}, {methyl palmitate (1) + biphenyl (2)} and {methyl palmitate (1) + naphthalene (2)} were measured using differential scanning calorimeter. Simple eutectic behaviours for these systems were observed. The experimental results were correlated by means of the NRTL, Wilson, UNIQUAC and ideal models. The root-mean-square deviations of the solubility temperatures for all measured data vary from 0.5477 K (for UNIQUAC model) to 7.79 K; the deviations depend on the binary system studied and particular model used. The best solubility correlation was obtained with UNIQUAC model and this observation confirms previous results. 相似文献
82.
Qingyun Qian Dr. Javier Ruiz‐Martínez Prof. Dr. Mohamed Mokhtar Prof. Dr. Abdullah M. Asiri Prof. Dr. Shaeel A. Al‐Thabaiti Prof. Dr. Suliman N. Basahel Hendrik E. van der Bij Dr. Jan Kornatowski Prof. Dr. Bert M. Weckhuysen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(34):11204-11215
The formation of hydrocarbon pool (HCP) species during methanol‐to‐olefin (MTO) and ethanol‐to‐olefin (ETO) processes have been studied on individual micron‐sized SAPO‐34 crystals with a combination of in situ UV/Vis, confocal fluorescence, and synchrotron‐based IR microspectroscopic techniques. With in situ UV/Vis microspectroscopy, the intensity changes of the λ=400 nm absorption band, ascribed to polyalkylated benzene (PAB) carbocations, have been monitored and fitted with a first‐order kinetics at low reaction temperatures. The calculated activation energy (Ea) for MTO, approximately 98 kJ mol?1, shows a strong correlation with the theoretical values for the methylation of aromatics. This provides evidence that methylation reactions are the rate‐determining steps for the formation of PAB. In contrast for ETO, the Ea value is approximately 60 kJ mol?1, which is comparable to the Ea values for the condensation of light olefins into aromatics. Confocal fluorescence microscopy demonstrates that during MTO the formation of the initial HCP species are concentrated in the outer rim of the SAPO‐34 crystal when the reaction temperature is at 600 K or lower, whereas larger HCP species are gradually formed inwards the crystal at higher temperatures. In the case of ETO, the observed egg‐white distribution of HCP at 509 K suggests that the ETO process is kinetically controlled, whereas the square‐shaped HCP distribution at 650 K is indicative of a diffusion‐controlled process. Finally, synchrotron‐based IR microspectroscopy revealed a higher degree of alkylation for aromatics for MTO as compared to ETO, whereas high reaction temperatures favor dealkylation processes for both the MTO and ETO processes. 相似文献
83.
An L-band remotely-pumped erbium-doped fiber amplifier incorporating a secondary pumping scheme utilizing stimulated Raman
Scattering (SRS) was demonstrated. 1423 nm Raman laser was employed to generate SRS which became the secondary pump source.
The amplifier displayed excellent gain of up to 27.3 dB at 1570 nm for −30 dBm input. Noise figures were also kept to a minimum,
with the highest figure measured at 11 dB which was influenced by imperfection of the C/L coupler utilized in this architecture.
Overall transmission performance was measured as well and demonstrated an encouraging outcome with gain as high as 24 dB while
the noise figure was maintained at about 11 dB. The L-band signal amplification was also contributed by the stimulated Raman
scattering along the transmission fiber. The outcome of this study emphasized the feasibility of secondary pumping scheme
using SRS in L-band gain enhancement. 相似文献
84.
Dr. M. Merced Montero‐Campillo Prof. Manuel Yáñez Dr. Al Mokhtar Lamsabhi Prof. Otilia Mó 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(18):5309-5316
The most stable complexes between squaric acid and its sulfur‐ and selenium‐containing analogues (C4X4H2; X=O, S, Se) with BeY2 (Y=H, F) were studied by means of the Gaussian 04 (G4) composite ab initio theory. Squaric acid derivatives are predicted to be very strong acids in the gas phase; their acidity increases with the size of the chalcogen, with C4Se4H2 being the strongest acid of the series and stronger than sulfuric acid. The relative stability of the C4X4H2 ? BeY2 (X=O, S, Se; Y=H, F) complexes changes with the nature of the chalcogen atom; but more importantly, the formation of the C4X4H2 ? BeF2 complexes results in a substantial acidity enhancement of the squaric moiety owing to the dramatic electron‐density redistribution undergone by the system when the beryllium bond is formed. The most significant consequence of this acidity enhancement is that when BeF2 is replaced by BeH2, a spontaneous exergonic loss of H2 is observed regardless of the nature of the chalcogen atom. This is another clear piece of evidence of the important role that closed‐shell interactions play in the modulation of physicochemical properties of the Lewis acid and/or the Lewis base. 相似文献
85.
Ahmed Alsaedi Bashir Ahmad Mokhtar Kirane Belgacem Rebiai 《Mathematical Methods in the Applied Sciences》2019,42(12):4378-4393
Local and blowing‐up solutions for the Cauchy problem for a system of space and time fractional evolution equations with time‐nonlocal nonlinearities of exponential growth are considered. The existence and uniqueness of the local mild solution is assured by the Banach fixed point principle. Then, we establish a blow‐up result by Pokhozhaev capacity method. Finally, under some suitable conditions, an estimate of the life span of blowing‐up solutions is established. 相似文献
86.
Achouak Bekkai Belgacem Rebiai Mokhtar Kirane 《Mathematical Methods in the Applied Sciences》2019,42(6):1819-1830
In this paper, we are concerned with local existence and blowup of a unique solution to a time‐space fractional evolution equation with a time nonlocal nonlinearity of exponential growth. At first, we prove the existence and uniqueness of the local solution by the Banach contraction mapping principle. Then, the blowup result of the solution in finite time is established by the test function method with a judicious choice of the test function. 相似文献
87.
Résumé SoitT un courant positif fermé sur un voisinage de 0 dansC
n. Nous montrons queT admet un c?ne tangent (limite de la famille de ses homothétiques), dès que les masses projectivesv
T(r) convergent assez vite versV
T(0) pour que (v
T(r)−v
T(0))/r soit localement sommable enr=0. Cette condition suffisante est optimale: nous construisons des courants de bidegré (1, 1) n'ayant pas de c?ne tangent,
tels que l'intégrale de (v
T(r)−v
T(0))/r soit aussi peu divergente qu'on le souhaite. LorsqueT est le courant d'intégration sur un ensemble analytique, on vérifie quev
T(r)−v
T(0)=0r
ε), ce qui redonne le théorème de Thie-King sur l'existence du c?ne tangent. 相似文献
88.
Lamsabhi AM Mó O Yáñez M Guillemin JC Haldys V Tortajada J Salpin JY 《Journal of mass spectrometry : JMS》2008,43(3):317-326
The gas-phase reactions between Ni(+) ((2)D(5/2)) and aminoacetonitrile, a molecule of prebiological interest as possible precursor of glycine, have been investigated by means of mass spectrometry techniques. The mass-analyzed ion kinetic energy (MIKE) spectrum reveals that the adduct ions [NC--CH(2)--NH(2), Ni(+)] spontaneously decompose by loosing HCN, H(2), and H(2)CNH, the loss of hydrogen cyanide being clearly dominant. The structures and bonding characteristics of the aminoacetonitrile-Ni(+) complexes as well as the different stationary points of the corresponding potential energy surface (PES) have been theoretically studied by density functional theory (DFT) calculations carried out at B3LYP/6-311G(d,p) level. A cyclic intermediate, in which Ni(+) is bisligated to the cyano and the amino group, plays an important role in the unimolecular reactivity of these ions, because it is the precursor for the observed losses of HCN and H(2)CNH. In all mechanisms associated with the loss of H(2), the metal acts as hydrogen carrier favoring the formation of the H(2) molecule. The estimated bond dissociation energy of aminoacetonitrile-Ni(+) complexes (291 kJ mol(-1)) is larger than those measured for other nitrogen bases such as pyridine or pyrimidine and only slightly smaller than that of adenine. 相似文献
89.
Lamsabhi AM 《The journal of physical chemistry. A》2008,112(8):1791-1797
The specific hydration of 2,7-dimethyl-1,2,4-triazepine oxo-thio derivatives by one water molecule has been investigated at the B3LYP/6-311++G(3df,2p)//B3LYP/6-311+G(d,p) level of theory. The existence of different hydrogen bond (HB) donor and acceptor centers in these molecules led to different kinds of hydrogen bonds (CH-O, OH-S, NH-O, OH-N, and OH-O) and different kinds of complexes. Among them, the most stable structures correspond to complexes where the heteroatom X or Y at positions 3 and 5 behaves as HB acceptor and the hydrogen atom associated with the nitrogen atom at position 4 as HB donor. In accordance with previous studies, it has been shown that the thiocarbonyl group forms stronger HBs than the carbonyl group because the sulfur atom is a better HB acceptor than the oxygen one. With the help of the AIM (atoms in molecules) theory and ELF (electron localization function) analysis, it has been shown that, in the case of 3O5O, 3S5O, and 3S5S, the most basic site is the heteroatom at position 3, while in 3O5S species the most basic center is the sulfur atom. 相似文献
90.
Medina A Claessens CG Rahman GM Lamsabhi AM Mó O Yáñez M Guldi DM Torres T 《Chemical communications (Cambridge, England)》2008,(15):1759-1761
We have designed, synthesized and probed a dodecafluoro-subphthalocyaninato boron(III) unit, which bears a triphenylamine moiety in its axial position, as a novel electron donor-acceptor system. 相似文献