全文获取类型
收费全文 | 202篇 |
免费 | 10篇 |
国内免费 | 16篇 |
专业分类
化学 | 101篇 |
晶体学 | 1篇 |
力学 | 10篇 |
数学 | 36篇 |
物理学 | 80篇 |
出版年
2023年 | 5篇 |
2022年 | 13篇 |
2021年 | 10篇 |
2020年 | 11篇 |
2019年 | 6篇 |
2018年 | 7篇 |
2017年 | 15篇 |
2016年 | 12篇 |
2015年 | 17篇 |
2014年 | 12篇 |
2013年 | 14篇 |
2012年 | 14篇 |
2011年 | 18篇 |
2010年 | 8篇 |
2009年 | 15篇 |
2008年 | 8篇 |
2007年 | 3篇 |
2006年 | 12篇 |
2005年 | 3篇 |
2004年 | 1篇 |
2003年 | 3篇 |
2002年 | 1篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
排序方式: 共有228条查询结果,搜索用时 46 毫秒
51.
《Solid State Ionics》1988,26(3):197-201
Some physical properties of n-TiO2 single crystals have been studied by electrochemical and photoelectrochemical techniques. X-ray diffractometry confirmed the TiO2 basic rutile type structure. For the TiO2/0.5 N NaOH system in the dark a Tafel slope of 0.11 V/decade was observed between 0.50 and 0.61 V versus SCE, suggesting a one-electron process. The potential, at which the gaseous oxygen evolution was confirmed, was well over 2.0 V versus SCE. On the other hand the potential for oxygen evolution was markedly decreased to −0.75 V versus SCE, when the TiO2 was illuminated. From these facts and the observation of passivation, transpassivation and current saturation an oxygen-pumping mechanism is proposed for the polarization behaviour of the TiO2 electrode in the dark. The spectral responses of photocurrent generated from TiO2 at 0.0 V bias versus SCE showed that the peak illumination current at 360 nm is larger than the dark current by three orders of magnitude. The band gap of TiO2 was determined as 3.1 eV by assuming that the photoelectrolysis of water involves an indirect energy transition. An anomalous photoresponse was observed at 1.8 eV, which is due to the presence of surface states at the TiO2/electrolyte interface. 相似文献
52.
Liying Wang Chong Gao Jianguo Feng Yong Xu Danqi Li Lixin Zhang 《Molecules (Basel, Switzerland)》2020,25(23)
The stability of the suspension system of the two crystal forms of pyraclostrobin is evaluated using multiple light technology, and the adsorption performance of polycarboxylate dispersant on the surface of two different crystalline pyraclostrobin particles is compared in combination with XRD, FTIR, XPS, and SEM from the microscopic view. The adsorption kinetics and thermodynamics studies of 2700 on the surfaces of different crystalline forms of pyraclostrobin particles show that the adsorption process of 2700 on the surfaces of pyraclostrobin crystal forms II and IV conform to pseudo-second-order kinetic adsorption model. The Ea values for crystal forms II and IV are 12.93 and 14.39 kJ∙mol−1, respectively, which indicates that both adsorption processes are physical adsorption. The adsorption models of 2700 on the surfaces of pyraclostrobin crystal forms II and IV are in accordance with Langmuir adsorption isotherms. The ∆Gad values of crystal forms II and IV are negative and the ∆Sad values are positive at different temperatures. Therefore, the adsorption processes are spontaneous and accompanied by entropy increase. The results of this study provide an important theoretical basis for the selection of polycarboxylate dispersants in the suspension of pyraclostrobin. This study also provides a reference for the research of polycrystalline pesticide suspension concentrate. 相似文献
53.
54.
《Journal of magnetism and magnetic materials》2005,295(3):269-276
The electronic structure of CeRu2Ge2 has been calculated using the self-consistent full-potential linearized augmented plane wave method (FP_LAPW) based on the density functional theory (DFT). The effect of the position exchanging between Ru and Ge atoms is studied. It shows that the magnetic moment of Ce ion is sensitive to the position exchanging between them. The result also reveals that the spin–orbit interaction and on-site Coulomb potential should be added on the Ce-derived 4f orbitals to obtain the correctly ground-state magnetic moment of CeRu2Ge2. The electronic structures of CeRu2Ge2 and its isostructural compound CeRu2Si2 have also been compared. 相似文献
55.
??A single distribution-free (nonparametric) Phase II exponentially weighted moving average (EWMA) chart based on the Cucconi statistic, referred to as the EWMA-Cucconi (EC) chart, is considered here for simultaneously monitoring shifts in the unknown location and scale parameters of a univariate continuous process. A comparison with some other existing nonparametric EWMA charts is presented in terms of the average, the standard deviation and some
percentiles of the run length distribution. Numerical results based on Monte Carlo analysis show that the EC chart provides quite a satisfactory performance. The effect of the Phase I (reference) sample size on the IC performance of the EC chart is studied in detail. The application of the EC chart is illustrated by two real data examples. 相似文献
56.
《European Journal of Operational Research》2005,167(1):208-225
This study presents an interval-parameter fuzzy two-stage stochastic programming (IFTSP) method for the planning of water-resources-management systems under uncertainty. The model is derived by incorporating the concepts of interval-parameter and fuzzy programming techniques within a two-stage stochastic optimization framework. The approach has two major advantages in comparison to other optimization techniques. Firstly, the IFTSP method can incorporate pre-defined water policies directly into its optimization process and, secondly, it can readily integrate inherent system uncertainties expressed not only as possibility and probability distributions but also as discrete intervals directly into its solution procedure. The IFTSP process is applied to an earlier case study of regional water resources management and it is demonstrated how the method efficiently produces stable solutions together with different risk levels of violating pre-established allocation criteria. In addition, a variety of decision alternatives are generated under different combinations of water shortage. 相似文献
57.
58.
In recent years, the operation efficiency of chaos-based image cryptosystems has drawn much more concerns. However, the workload arised from floating point arithmetic in chaotic map iteration prevents the efficiency promotion of these cryptosystems. In this paper, we present a novel image encryption scheme using Gray code based permutation approach. The new permutation strategy takes full advantage of (n, p, k)-Gray-code achievements, and is performed with high efficiency. A plain pixel-related image diffusion scheme is introduced to compose a complete cryptosystem. Simulations and extensive security analyses have been carried out and the results demonstrate the high security and operation efficiency of the proposed scheme. 相似文献
59.
In order to explore the potential application of combined physical treatment in producing highly lipophilic modified starch, the effects of ultrasound combined with freeze-thaw treatment on the microstructure and physicochemical properties of potato starch were investigated. The samples treated by combined treatment had the roughest structure and the oil adsorptive capacity value increased from 59.62% (native starch, NS) to 80.2% (7 cycles of ultrasound-freeze-thaw treatment starch, 7UT-FTS). Compared to NS, the crystalline type and chemical groups of modified starches did not change, but the relative crystallinity, enthalpy change, and paste viscosity decreased to varying degrees, while the gelatinization temperature increased. The digestibility of raw modified starch was higher than that of NS, but this phenomenon disappeared after gelatinization. 7UT-FTS showed better resist-digestibility than NS after encapsulating oil. Hence, this would be an efficient and environmentally friendly way to produce modified starch with safety, highly lipophilic and heat resistance. 相似文献
60.