全文获取类型
收费全文 | 302篇 |
免费 | 5篇 |
专业分类
化学 | 159篇 |
晶体学 | 10篇 |
力学 | 6篇 |
数学 | 21篇 |
物理学 | 111篇 |
出版年
2024年 | 1篇 |
2022年 | 9篇 |
2021年 | 7篇 |
2020年 | 4篇 |
2019年 | 5篇 |
2018年 | 4篇 |
2017年 | 5篇 |
2016年 | 9篇 |
2015年 | 7篇 |
2014年 | 12篇 |
2013年 | 18篇 |
2012年 | 14篇 |
2011年 | 27篇 |
2010年 | 13篇 |
2009年 | 10篇 |
2008年 | 28篇 |
2007年 | 17篇 |
2006年 | 16篇 |
2005年 | 14篇 |
2004年 | 10篇 |
2002年 | 12篇 |
2001年 | 14篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1995年 | 2篇 |
1994年 | 7篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1970年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1960年 | 2篇 |
1958年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有307条查询结果,搜索用时 15 毫秒
301.
Schumacher HC Alves M Leite CA Santos JP Neto ET Murakami MM Galembeck F do Amaral M 《Journal of colloid and interface science》2007,305(2):256-263
Stable cationic latices were prepared by charge inversion of anionic styrene-acrylic copolymer latices upon binding Al3+ and Fe3+ ions. This is achieved by stabilizing the latices with a high-HLB (hydrophile-lypophile balance) nonionic surfactant that imparts strong steric stability to the latex, even in the presence of high concentrations of multivalent counterions while these are bound to the latex anionic sites. The cationic latices thus prepared have good stability properties, and the same procedure should be applicable to essentially any latex-carrying anionic sites. Analytical ESI-TEM images show that particle-bound iron is concentrated at the particle borders, but it is also found in the particle bulk. 相似文献
302.
Sarraguça MC Cruz AV Amaral HR Costa PC Lopes JA 《Analytical and bioanalytical chemistry》2011,399(6):2137-2147
This work compares the estimation of the particle size distribution of a pharmaceutical powder using near-infrared spectroscopy
(NIRS), powder flowability properties, and components concentration. The estimations were made by considering the former data
blocks separately and together using a multi-block approach. The powders were based on a formulation of paracetamol as the
pharmaceutical active ingredient. The reference method used to determine particle size distribution was sieving. Partial least
squares methods were used to estimate the multivariate regression models, and the results were compared in terms of figures
of merit. It was shown that the partial least squares methods gave similar prediction errors. Regarding the data blocks used,
the NIRS block was proven the most advantageous to estimate the particle size distribution. The prediction error of the NIRS
block was similar to the other data blocks with additional advantages such as less generalization problems and the possibility
of its use to predict additional physical and chemical properties with an improvement to analysis time. The multi-block approach
produced the worst results but nevertheless allowed a deeper understanding of the individual contributions of the data blocks
in the prediction of the particle size distribution. 相似文献
303.
Amaral SP Fernandez-Villamarin M Correa J Riguera R Fernandez-Megia E 《Organic letters》2011,13(17):4522-4525
A multigram synthesis of the repeating unit of GATG (gallic acid-triethylene glycol) dendrimers is described through an efficient and cost-effective route. These conditions overcome major problems precluding scaling up and afford product in excellent overall yield and purity. Special attention has been paid in this process to green chemistry principles: atom economy, safety, and waste reduction. This scheme could be easily adapted for the preparation of similar dendritic systems. 相似文献
304.
In this work we report the purification of a crude acetin mixture into mono‐, di‐ and triacetin by countercurrent chromatography. The process was initially tested on a small, semi‐preparative scale (0.5 g) to determine its efficiency. The process was then scaled up to accommodate 2.5 g of crude reaction products containing a mixture of the acetins. The solvent system ethyl acetate/n‐butanol/water 1:0.2:1 was used in all separation procedures. Mono‐, di‐ and triacetins were separated similarly in the semi‐preparative and preparative runs. 相似文献
305.
Erika Cristina Vargas de Oliveira Naira Rezende Maciel Lia Queiroz do Amaral 《Journal of Dispersion Science and Technology》2013,34(12):1656-1662
Oil-in-water emulsions were developed employing the HLB system and emulsion phase inversion (EPI) method. X-ray diffraction revealed that the anisotropic structures around the inner phase globules were lamellar gel network phases. The calculated distances between the lamellae made after preparation and 3 month latter showed that there was no swelling of the lamellar gel network indicating good stability and few changes during storage. The developed emulsions were stable and have potential to be employed for cosmetic and pharmaceutical purposes. The gel phase network and vegetal components seemed to be contributing factors. 相似文献
306.
G. N. P. Oliveira A. M. L. Lopes T. M. Mendon?a J. P. Araújo J. Agostinho Moreira A. Almeida V. S. Amaral J. G. Correia 《Hyperfine Interactions》2010,197(1-3):123-128
This work presents an electric field gradient and magnetic hyperfine field study, in the AgCrO2 multiferroic with triangular spin lattice. The temperature dependence of the electric field gradient (efg) and magnetic hyperfine field (mhf) at Cr site was studied at isolde via perturbed angular correlation measurements with the 111In probe, at room temperature and below the Néel temperature (T?≤?21 K) down to 12 K. The results show the presence of two distinct local environments. One axial symmetric efg with a very low mhf, and a non axially symmetric efg with a much higher one. The temperature dependences of mhf magnitude and of the angle between the mhf and the principle component of the efg are investigated. 相似文献
307.
D.C. Leitao C.T. Sousa J. Ventura J.S. Amaral F. Carpinteiro K.R. Pirota M. Vazquez J.B. Sousa J.P. Araujo 《Journal of Non》2008,354(47-51):5241-5243
In this work we use nanoporous alumina substrates as templates for the growth of Ni and Ni80Fe20 nanowires. Our membranes were obtained by a two-step anodization process of high-purity aluminum foils: first anodizations were performed at 40 V for 15 h in 0.3 M oxalic acid, at 2–6 °C; the second anodization was carried out using the same conditions for 30 min, resulting in pore lengths of ~1.3 μm. After the second anodization, the pore bottom barrier-layer was thinned, to allow the current to flow through electron tunneling. A pulsed electrodeposition method was then used to grow Ni and Ni80Fe20 nanowires. Transport characterization and isothermal magnetization measurements performed on the produced arrays are presented. 相似文献