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71.
Temperature- and pH-dependent morphology and FT-IR analysis of magnesium carbonate hydrates 总被引:3,自引:0,他引:3
Zhang Z Zheng Y Ni Y Liu Z Chen J Liang X 《The journal of physical chemistry. B》2006,110(26):12969-12973
Various morphologies of magnesium carbonate hydrates have been synthesized by carefully adjusting the reaction temperature and pH value of the initial reaction solution in the precipitation process. At lower temperatures (from room temperature to 328 K) and lower pH values (variation with the reaction temperature), magnesium carbonate hydrates are prone to display needlelike morphology, and the axis diameter of the particles decreases with the increase of reaction temperature and pH value. With the further increase of the reaction temperature (333-368 K) and pH value, the sheetlike crystallites become the preferred morphology, and at higher temperatures and pH values, these crystallites tend to assemble into layerlike structures with diverse morphologies, such as spherical-like particles with rosette-like structure and cakelike particles built from sheetlike structure. Fourier transform infrared (FT-IR) spectra show that these various morphologies are closely related to their compositions. The needlelike magnesium carbonate hydrate has a formula of MgCO3.xH2O, in which the value x is greatly affected by the experimental conditions, whereas with the morphological transformation from needlelike to sheetlike structure, their corresponding compositions also change from MgCO3.xH2O to Mg5(CO3)4(OH)2.4H2O in the interval of 328-333 K. 相似文献
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73.
Biqing Bao Lihui Yuwen Xiaowei Zhan Lianhui Wang 《Journal of polymer science. Part A, Polymer chemistry》2010,48(15):3431-3439
New water‐soluble hyperbranched polyfluorenes bearing carboxylate side chains have been synthesized by the simple “A2 + B2 + C3” protocol based on Suzuki coupling polymerization. The linear polyfluorene analogue LPFA was also synthesized for comparative investigation. The optical properties of the neutral precursory polymers in CHCl3 and final carboxylic‐anionic conjugated polyelectrolytes in buffer solution were investigated. The obtained hyperbranched polyelectrolyte HPFA2 with lower content of branch unit (2%) showed excellent solubility and high fluorescence quantum yield (?F = 89%) in aqueous solution. Fluorescence quenching of HPFA2 by different metal ions was also investigated, the polyelectrolyte showed high selectivity for Hg2+ and Cu2+ ions relative to other various metal ions in buffer solution. The Stern‐Volmer constant Ksv was determined to be 0.80 × 106 M?1 for Hg2+ and 3.11 × 106 M?1 for Cu2+, respectively, indicating the potential application of HPFA2 as a highly selective and sensitive chemosensor for Hg2+ and Cu2+ ions in aqueous solution. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3431–3439, 2010 相似文献
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传统的土地利用分类方法大多基于对资料或影像的人工解译,存在一定的局限性。近年来,结合空间大数据和自然语言处理技术进行低成本快速的土地资源管理已成为研究热点。以美国纽约市曼哈顿区为例,提出了融合遥感影像和社会感知数据的城市土地利用分类方法。从遥感影像中提取光谱特征、从推特数据中提取用户活动时空和主题特征,基于随机森林法和深度神经网络法,构建了细粒度的城市土地利用分类模型。通过对比不同特征组合分类方法的精度,得到结合光谱特征和用户活动时空、主题特征的深度神经网络方法的结果最优,总体精度达82.65%,Kappa系数为70.1%。结果表明,社会感知数据中隐含的用户活动时空模式和活动主题信息均有助于提高城市土地利用分类的精度,而神经网络法可有效融合多源数据,为快速、低成本获取城市土地利用信息提供了新的途径。 相似文献
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Yuhua Zhao Yuwen Wang Junping Shi 《Journal of Mathematical Analysis and Applications》2007,331(1):263-278
The set of steady state solutions to a reaction-diffusion equation modeling an autocatalytic chemical reaction is completely determined, when the reactor has spherical geometry, and the spatial dimension is n=1 or 2 for any reaction order, or n?3 for subcritical reaction order. Bifurcation approach and analysis of linearized problems are used to establish exact multiplicity and precise global bifurcation diagram of positive steady states. 相似文献
79.
In this paper, we study the perturbation problem for oblique projection generalized inverses of closed linear operators in Banach spaces. By the method of the perturbation analysis of linear operators, we obtain an explicit perturbation theorem and error estimates for the oblique projection generalized inverse of closed linear operators under the T-bounded perturbation, which extend the known results on the perturbation of the oblique projection generalized inverse of bounded linear operators in Banach spaces. 相似文献
80.
Jing Huang Yuwen Zhang J. K. Chen 《Applied Physics A: Materials Science & Processing》2011,103(1):113-121
Superheating of the liquid phase caused by non-equilibrium evaporation during femtosecond-laser processing of a thin metal
film is investigated by adopting the wave hypothesis along with the two-temperature model. The simulation results show that
the superheating in the liquid occurs shortly after the evaporation. For a 100-fs laser pulse of 0.7 J/cm2, the maximum degree of superheating in liquid can reach 600 K. The superheating in solid can also be captured in the current
model, which can be as high as 300 K. The effects of laser fluence, pulse duration and film thickness on the degree of superheating
were studied. A higher laser fluence will increase the degree of superheating in liquid significantly but has little effect
for the solid part. In the range adopted in the current work, the pulse duration has little effect on the degree of superheating
in both liquid and solid phases. 相似文献