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11.
Ao‐kai Zhang Jun Ling Kewen Li Guo‐dong Fu Tasuku Nakajima Takayuki Nonoyama Takayuki Kurokawa Jian Ping Gong 《Journal of Polymer Science.Polymer Physics》2016,54(13):1227-1236
In this study, controlled amount of dangling ends is introduced to the two series of poly(ethylene glycol)‐based hydrogel networks with three and four crosslinking functionality by using click chemistry. The structure of the gels with regulated defect percentage is confirmed by comparing the results of low‐field NMR characterization and Monte Carlo simulation. The mechanical properties of these gels were characterized by tensile stress–strain behaviors of the gels, and the results are analyzed by Gent model and Mooney–Rivlin model. The shear modulus of the swollen gels is found to be dependent on the functionality of the network, and decreases with the defect percentage. Furthermore, the value of shear modulus well obeys the Phantom model for all the gels with varied percentage of the defects. The maximum extension ratio, obtained from the fitting of Gent model, is also found to be dependent on the functionality of the network, and does not change with the defect percentage, except at very high defect percentage. The value of the maximum extension ratio is between that predicted from Phantom model and the Affine model. This indicates that at the large deformation, the fluctuation of the crosslinking points is suppressed for some extend but still exists. Polymer volume fractions at various defect percentages obtained from prediction of Flory–Rehner model are found to be in well agreement with the swelling experiment. All these results indicate that click chemistry is a powerful method to regulate the network structure and mechanical properties of the gels. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1227–1236 相似文献
12.
Wenjia Wang Xiaoyun Yang Guangcai Chang Pengfei An Kewen Cha Yuhui Dong Peng Liu 《Journal of synchrotron radiation》2017,24(4):781-786
A method to calibrate and stabilize the incident X‐ray energy for anomalous diffraction data collection is provided and has been successfully used at the single‐crystal diffraction beamline 1W2B at the Beijing Synchrotron Radiation Facilities. Employing a feedback loop to control the movement of the double‐crystal monochromator, this new method enables the incident X‐ray energy to be kept within a 0.2 eV range at the inflection point of the absorption edge. 相似文献
13.
疏水性L-酒石酸酯立体选择性萃取分离氯噻酮对映体 总被引:11,自引:0,他引:11
研究了氯噻酮对映体在含有疏水性L-酒石酸酯手性选择体的水-1,2-二氯乙烷两相系统萃取分配行为,考察了pH、L-酒石酸酯烷基链长度、L-酒石酸酯浓度和磷酸盐浓度对分配系数和分离因子的影响。实验表明:L-酒石酸酯与氯噻酮I( )-对映体比与Ⅱ(-)-对映体形成更稳定的非对映体复合物;随着L-酒石酸酯取代烷基链长的增长,分配系数和分离因子增大;随着pH增大,分配系数增大,而分离因子降低;同时,L-酒石酸酯和磷酸盐浓度影响也比较大。 相似文献
14.
Kewen Zhao 《Monatshefte für Mathematik》2009,20(1):279-293
Let G be a simple graph with n vertices. For any v ? V(G){v \in V(G)} , let N(v)={u ? V(G): uv ? E(G)}{N(v)=\{u \in V(G): uv \in E(G)\}} , NC(G) = min{|N(u) èN(v)|: u, v ? V(G){NC(G)= \min \{|N(u) \cup N(v)|: u, v \in V(G)} and
uv \not ? E(G)}{uv \not \in E(G)\}} , and NC2(G) = min{|N(u) èN(v)|: u, v ? V(G){NC_2(G)= \min\{|N(u) \cup N(v)|: u, v \in V(G)} and u and v has distance 2 in E(G)}. Let l ≥ 1 be an integer. A graph G on n ≥ l vertices is [l, n]-pan-connected if for any u, v ? V(G){u, v \in V(G)} , and any integer m with l ≤ m ≤ n, G has a (u, v)-path of length m. In 1998, Wei and Zhu (Graphs Combinatorics 14:263–274, 1998) proved that for a three-connected graph on n ≥ 7 vertices, if NC(G) ≥ n − δ(G) + 1, then G is [6, n]-pan-connected. They conjectured that such graphs should be [5, n]-pan-connected. In this paper, we prove that for a three-connected graph on n ≥ 7 vertices, if NC
2(G) ≥ n − δ(G) + 1, then G is [5, n]-pan-connected. Consequently, the conjecture of Wei and Zhu is proved as NC
2(G) ≥ NC(G). Furthermore, we show that the lower bound is best possible and characterize all 2-connected graphs with NC
2(G) ≥ n − δ(G) + 1 which are not [4, n]-pan-connected. 相似文献
15.
Decline curve analysis (DCA) is a traditional method for production prediction, which is still being used because it works
in many cases and it is relatively simple to apply. However, DCA methods can neither match nor predict the fluctuating oil
production during the early period when applied to entire reservoirs. The change in oil production may be because of variation
in production conditions or the number of injection/production wells. In this study, we focused on the latter problem, change
in the number of production wells. Obviously, there would be a significant oil production boost during a specific time period
if more oil wells are drilled. The traditional DCA approach cannot match the increase in oil production due to the increase
in the number of oil production wells. We have developed a method to match the oil production of entire reservoirs for the
life span by considering the change in the number of production wells. The main idea of this approach came from the concept
of effective wells. We applied this approach in several sandstone oil reservoirs with different permeabilities. The proposed
effective-well model could match the oil production data in different reservoirs, even during the early period of production
when the oil production rate change with time because of the variation in the number of producers. Comparison with the existing
models (exponential, hyperbolic model, and harmonic models) was made and the results showed the proposed approach had the
best fit to the production history in the cases studied. 相似文献
16.
Capillary pressure curves of six low porosity and low permeability core samples from The Geysers geothermal field were measured
using the mercury-intrusion approach to characterize the heterogeneity of rock. One high permeability Berea sandstone core
sample was analyzed similarly, for comparison. The maximum pressure of mercury intruded into the rock was about 200 MPa to
reach the extremely small pores. Experimental data showed that the capillary pressure curves of The Geysers rock are very
different from that of the Berea sandstone. It was found that the frequently used capillary pressure models could not be used
to represent the data from The Geysers rock samples. This might be because of the fractures in the rock. To this end, a fractal
technique was proposed to model the features of the capillary pressure curves and to characterize the difference in heterogeneity
between The Geysers rock and Berea sandstone. The results demonstrated that the rock from The Geysers geothermal field was
fractal over a scaling range of about five orders of magnitude. The values of the fractal dimension of all the core samples
(six from The Geysers and one Berea sandstone) calculated using the proposed approach were in the range from 2 to 3. The results
showed that The Geysers rock with a high density of fractures had a greater fractal dimension than Berea sandstone which is
almost without fractures. This shows that The Geysers rock has greater heterogeneity, as expected. 相似文献
17.
A New Method for Calculating Two-Phase Relative Permeability from Resistivity Data in Porous Media 总被引:4,自引:0,他引:4
Kewen Li 《Transport in Porous Media》2008,74(1):21-33
Many resistivity data from laboratory measurements and well logging are available. Papers on the relationship between resistivity
and relative permeability have been few. To this end, a new method was developed to infer two-phase relative permeability
from the resistivity data in a consolidated porous medium. It was found that the wetting phase relative permeability is inversely
proportional to the resistivity index of a porous medium. The proposed model was verified using the experimental data in different
rocks (Berea, Boise sandstone, and limestone) at different temperatures up to 300°F. The results demonstrated that the oil
and water relative permeabilities calculated from the experimental resistivity data by using the model proposed in this article
were close to those calculated from the capillary pressure data in the rock samples with different porosities and permeabilities.
The results demonstrated that the proposed approach to calculating two-phase relative permeability from resistivity data works
satisfactorily in the cases studied. 相似文献
18.
Experimental Study of Water Injection into Geothermal Systems 总被引:1,自引:0,他引:1
Water injection or reinjection in geothermal reservoirs has been proven as a successful engineering technique with many benefits
such as maintaining reservoir pressure and sustaining well productivity. However, many questions related to water injection
into geothermal reservoirs still remain unclear; for example, how the in-situ water saturation changes with reservoir pressure
and temperature, and how the reservoir pressure influences well productivity. In order to answer these questions, we studied
the effects of temperature and pressure on the in-situ water saturation in a core sample using an experimental apparatus developed
in this study. It was found that the in-situ water saturation decreases very sharply near the saturation pressure but not
to the residual water saturation. When the mean pressure in the core sample decreases further, the in-situ water saturation
decreases sharply again to the residual water saturation. Also investigated were the effects of pressure on well productivity
index. We found that well productivity increased with an increase of mean reservoir pressure within a certain range and then
decreased. The well productivity reached the maximum value at a pressure close to the saturation pressure. The results of
this study may be useful to evaluate projects such as the waste water injection scheme at The Geysers. 相似文献
19.
20.
二茂铁是一种结构很特殊的化合物,它的发现在金属有机化合物研究中具有里程碑意义。简介了二茂铁的发现、结构确定、制备和应用。 相似文献