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41.
42.
Soudabeh Saeid Mohammad A. Behnajady Pasi Tolvanen Tapio Salmi 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2018,92(5):876-883
The photooxidative removal of analgesic pharmaceutical compound phenazopyridine (PhP) from aqueous solutions by UV/H2O2 system with a re-circulated photoreactor was investigated. Response surface methodology (RSM) was employed to optimize the effect of operational parameters on the photooxidative removal efficiency. The investigated variables were: the initial PhP and H2O2 concentrations, irradiation time, volume of solution and pH. The analysis of variance (ANOVA) of quadratic model demonstrated that the described model was highly significant. The predicted values of the photooxidative removal efficiency were found to be in a fair agreement with experimental values (R2 = 0.9832, adjusted R2 = 0.9716). The model predicted that the optimal reaction conditions for a maximum removal of PhP (>98%) were: initial PhP concentration less than 23 mg L–1, initial concentration of H2O2 higher than 470 mg L–1, solution volume less than 500 mL, pH close to 2 and irradiation time longer than 6 min. 相似文献
43.
Summary A new analytical technique; purge-and-membrane-electron capture detection (ECD), is described and applied to the screening of halogenated aliphatic hydrocarbons. A water sample is first purged by helium and the purged compounds are collected from the gas phase through a silicone membrane to the analytical system. Purge-and-membrane-ECD provides very fast, selective and sensitive screening method for halogenated aliphatic hydrocarbons. The method was compared with conventional direct membrane extraction. Results obtained show that the limits of detection (0.01–2 g L–1) were comparable with both methods. However, significant shorter response times were measured with purge-and-trap than with direct membrane extraction. 相似文献
44.
Tuomikoski S Sikanen T Ketola RA Kostiainen R Kotiaho T Franssila S 《Electrophoresis》2005,26(24):4691-4702
We describe a novel electrospray tip design for MS which is fabricated completely out of SU-8 photoepoxy. A three-layer SU-8 fabrication process provides fully enclosed channels and tips. The tip shape and alignment of all SU-8 layers is done lithographically and is therefore very accurate. Fabrication process enables easy integration of additional fluidic functions on the same chip. Separation channels can be made with exactly the same process. Fluidic inlets are made in SU-8 during the fabrication process and no drilling or other postprocessing is needed. Channels have been fabricated and tested in the size range of 10 microm x 10 microm-50 microm x 200 microm. Mass spectrometric performance of the tips has been demonstrated with both pressure-driven flow and EOF. SU-8 microtips have been shown to produce stable electrospray with EOF in a timescale of tens of minutes. With pressure driven flow stable spray is maintained for hours. Taylor cone was shown to be small in volume and well defined even with the largest channel cross section. The spray was also shown to be well directed with our tip design. 相似文献
45.
Luo K Kuittu MP Tong C Majaniemi S Ala-Nissila T 《The Journal of chemical physics》2005,123(19):194702
We study the dynamics and equilibrium profile shapes of contact lines for wetting in the case of a spatially inhomogeneous solid wall with stripe defects. Using a phase-field model with conserved dynamics, we first numerically determine the contact line behavior in the case of a stripe defect of varying widths. For narrow defects, we find that the maximum distortion of the contact line and the healing length is related to the defect width, while for wide defects, it saturates to constant values. This behavior is in quantitative agreement with the experimental data. In addition, we examine the shape of the contact line between two stripe defects as a function of their separation. Using the phase-field model, we also analytically estimate the contact line configuration and find good qualitative agreement with the numerical results. 相似文献
46.
Alexey Kirilin Serap Sahin Päivi Mäki‐Arvela Johan Wärnå Tapio Salmi Dmitry Yu. Murzin 《国际化学动力学杂志》2010,42(10):629-639
The kinetics of the acylation of (R,S)‐1‐phenylethanol was investigated using lipase as a catalyst. The main parameters were temperature, reaction atmosphere, different acyl donors, and different amounts of acyl donor as well as the presence of some additives in the reaction mixture. The initial reaction rate increased with increasing temperature and with a decreasing amount of an acyl donor. The activated esters, such as isopropenyl‐ and vinyl acetate, exhibited very high acylation rates for R‐1‐phenylethanol, whereas low rates were obtained with ethyl acetate and 2‐methoxyethyl acetate. The addition of water and acetophenone decreased the acylation rate. A kinetic model was developed based on a sequential step mechanism, in which enzyme was reacting in the first step with an acyl donor followed by the reaction of a modified enzyme complex with the reactant, R‐1‐phenylethanol. Comparison with experimental data obtained at different temperatures allowed simplification of this model, leading to a kinetic equation with just one apparent parameter. The influence of the amount of acyl donor, ethyl acetate, could be quantitatively described by taking into account the competitive inhibition of the ethanol produced. The rate constants and apparent activation energy for experiments performed under different temperatures and the amounts of acylation agent were determined. The apparent activation energy was 24.5 kJ/mol. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 629–639, 2010 相似文献
47.
Esa Toukoniitty Päivi Mäki-Arvela Ahmad Kalantar Neyestanaki Ensio Laine Jyri-Pekka Mikkola Tapio Salmi Dmitry Yu. Murzin 《Reaction Kinetics and Catalysis Letters》2001,73(1):3-11
In the presence of ultrasound both the initial hydrogenation rate of 1-phenyl-1,2- propanedione and the enantiomeric excess of the main product, i.e. (R)-1-hydroxy- 1-phenylpropanone, increased by 75 % and 52 % in toluene, respectively, as compared to the silent hydrogenation. 相似文献
48.
Accelerated beam tracing algorithm 总被引:1,自引:0,他引:1
Determining early specular reflection paths is essential for room acoustics modeling. Beam tracing algorithms have been used to calculate these paths efficiently, thus allowing modeling of acoustics in real-time with a moving listener in simple, or complex but densely occluded, environments with a stationary sound source. In this paper, it is shown that beam tracing algorithms can still be optimized by utilizing the spatial coherence in path validation with a moving listener. Since the precalculations required for the presented technique are relatively fast, the acoustic reflection paths can be calculated even for a moving source in simple cases. Simulations were performed to show how the accelerated algorithm compares with the basic algorithm with varying scene complexity and occlusion. Up to two-orders of magnitude speed-up was achieved. 相似文献
49.
Shin J Ikonen T Khandkar MD Ala-Nissila T Sung W 《The Journal of chemical physics》2010,133(18):184902
We study the dynamics of flexible, semiflexible, and self-avoiding polymer chains moving under a Kramers metastable potential. Due to thermal noise, the polymers, initially placed in the metastable well, can cross the potential barrier, but these events are extremely rare if the barrier is much larger than thermal energy. To speed up the slow rate processes in computer simulations, we extend the recently proposed path integral hyperdynamics method to the cases of polymers. We consider the cases where the polymers' radii of gyration are comparable to the distance between the well bottom and the barrier top. We find that, for a flexible polymers, the crossing rate (R) monotonically decreases with chain contour length (L), but with the magnitude much larger than the Kramers rate in the globular limit. For a semiflexible polymer, the crossing rate decreases with L but becomes nearly constant for large L. For a fixed L, the crossing rate becomes maximum at an intermediate bending stiffness. For the self-avoiding chain, the rate is a nonmonotonic function of L, first decreasing with L, and then, above a certain length, increasing with L. These findings can be instrumental for efficient separation of biopolymers. 相似文献
50.
Jaakko Laakia Alexey Adamov Matti Jussila Christian S. Pedersen Alexey A. Sysoev Tapio Kotiaho 《Journal of the American Society for Mass Spectrometry》2010,21(9):1565-1572
This study demonstrates how positive ion atmospheric pressure photoionization-ion mobility spectrometry-mass spectrometry
(APPI-IMS-MS) can be used to produce different ionic forms of an analy te and how these can be separated. When hexane:toluene
(9:1) is used as a solvent, 2,6-di-tert-butylpyridine (2,6-DtBPyr) and 2,6-di-tert-4-methylpyridine (2,6-DtB-4-MPyr) efficiently produce radical cations [M]+ and protonated [M + H]+ molecules, whereas, when the sample solvent is hexane, protonated molecules are mainly formed. Interestingly, radical cations
drift slower in the drift tube than the protonated molecules. It was observed that an oxygen adduct ion, [M + O2]+, which was clearly seen in the mass spectra for hexane:toluene (9:1) solutions, shares the same mobility with radical cations,
[M]+. Therefore, the observed mobility order is most likely explained by oxygen adduct formation, i.e., the radical cation forrning
a heavier adduct. For pyridine and 2-tert-butylpyridine, only protonated molecules could be efficiently formed in the conditions used. For 1- and 2-naphthol it was
observed that in hexane the protonated molecule typically had a higher intensity than the radical cation, whereas in hexane:toluene
(9:1) the radical cation [M]+ typically had a higher intensity than the protonated molecule [M + H]+. Interestingly, the latter drifts slower than the radical cation [M]+, which is the opposite of the drift pattern seen for 2,6-DtBPyr and 2,6-DtB-4-MPyr. 相似文献