全文获取类型
收费全文 | 297篇 |
免费 | 15篇 |
国内免费 | 27篇 |
专业分类
化学 | 114篇 |
晶体学 | 3篇 |
力学 | 2篇 |
综合类 | 4篇 |
数学 | 27篇 |
物理学 | 189篇 |
出版年
2023年 | 3篇 |
2022年 | 20篇 |
2021年 | 5篇 |
2020年 | 6篇 |
2019年 | 7篇 |
2018年 | 7篇 |
2017年 | 1篇 |
2016年 | 6篇 |
2015年 | 3篇 |
2014年 | 3篇 |
2013年 | 6篇 |
2012年 | 9篇 |
2011年 | 3篇 |
2010年 | 9篇 |
2009年 | 31篇 |
2008年 | 42篇 |
2007年 | 20篇 |
2006年 | 23篇 |
2005年 | 11篇 |
2004年 | 7篇 |
2003年 | 10篇 |
2002年 | 12篇 |
2001年 | 9篇 |
2000年 | 14篇 |
1999年 | 12篇 |
1998年 | 10篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1978年 | 1篇 |
排序方式: 共有339条查询结果,搜索用时 15 毫秒
71.
Summary The properties and the coverage density of chemically bonded phases depend among others on the properties of their supports. Controlled-porosity glasses (CPG) are materials used as a support of bio-active ligands. Their network mainly consist of SiO2 as well as of a small amount of B2O3 and Na2O. The characteristic feature of porous glasses is the possibility of a change in the surface boron concentration leading to the change of the properties of their surface.This paper deals with the results of the separation of fungal proteins on packings consisting of vanillin bonded to CPG with different boron concentration on its surface. It appears from the data obtained that the changes in the affinity of the fungal proteins to the packing are related to the extend of the thermal treatment of the CPG. The protein fractions separated by chromatography were confirmed to be homogeneous by poly-acryloamide gel disc electrophoresis. 相似文献
72.
We have investigated transformation of eight industrial dyes by a whiterot fungus, Trametes versicolor. The fungus was found to decolorize Reactive Golden Yellow R, Procion Red, Reactive Violet 5, Reactive Blue 28, and Ponceau
Red 4R at an initial dye concentration of 80 ppm within 72 h of incubation, whereas it took 5 d to completely decolorize Reactive
Black 5 (40 ppm). However, it did not significantly decolorize Reactive Red 152 and Novatic Blue BC S/D. During decolorization
in liquid medium, laccase and manganese-independent peroxidase (MiP) activities were detected in culture filtrate of T. versicolor. Dye-decolorizing activity of the culture was found to be associated with H2O2-dependent activity of the culture filtrate. Furthermore, dye-decolorizing activity of the culture filtrate was not influenced
by Mn2+ or veratryl alcohol, thus suggesting a role of extracellular MiP in decolorization of synthetic dyes by T. versicolor. 相似文献
73.
没食子酸-过氧化氢-甲醛体系中Co(Ⅱ)和Mn(Ⅱ)的化学发光同时测定 总被引:2,自引:0,他引:2
在较大量硫脲存在下,没食子酸-过氧化氢-甲醛体系中化学发光的动力学性质发生了变化,出现多峰现象,藉此实现了Co(Ⅱ)和Mn(Ⅱ)的化学发光同时测定。该法灵敏度高,选择性好,Co(Ⅱ)的测定范围是3×10-5~2ppm,Mn(Ⅱ)是0.03~10ppm。 相似文献
74.
75.
P. Lehnen W. Kleemann Th. Woike R. Pankrath 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(4):633-637
The linear birefringence (LB) of Sr
0.61-x
Ba
0.39
Nb
2
O
6
:Ce
3+
x (SBN61:Ce) has been measured as a function of temperature within the range of . Large tails have been observed above the ferroelectric phase transition temperatures T
c
= 350, 328, 320 and 291 K for the concentrations x
= 0, 0.0066, 0.0113 and 0.0207, respectively. Within an Ornstein-Zernike analysis the critical exponents , and are determined. It suggests that pure SBN61 belongs to the 3D Ising universality class. Doping with Ce
3+
ions, which seem to act as random fields, enhances the relaxor properties. The critical exponents and of SBN61:Ce shift against those of the three-dimensional random-field Ising model.
Received 1 October 1999 相似文献
76.
C. Chatelain P.E. Berche B. Berche 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,7(3):439-449
We investigate the influence of aperiodic modulations of the exchange interactions between nearest-neighbour rows on the phase
transition of the two-dimensional eight-state Potts model. The systems are studied numerically through intensive Monte-Carlo
simulations using the Swendsen-Wang cluster algorithm for different aperiodic sequences. The transition point is located through
duality relations, and the critical behaviour is investigated using FSS techniques at criticality. While the pure system exhibits
a first-order transition, we show that the deterministic fluctuations resulting from the aperiodic coupling distribution are
liable to modify drastically the physical properties in the neighbourhood of the transition point. For strong enough fluctuations
of the sequence under consideration, a second-order phase transition is induced. The exponents , and are obtained at the new fixed point and crossover effects are discussed. Surface properties are also studied.
Received: 18 March 1998 / Revised: 29 June 1998 / Accepted: 10 September 1998 相似文献
77.
Silica is a popular filler, but in epoxidized natural rubber, can act as a cross-linking agent. Unfortunately, a high amount of silica is necessary to obtain satisfactory tensile strength. Moreover, a high amount of silica in ENR/silica hybrids is associated with low elongation at break. In our paper, we propose natural phenolic compounds, including quercetin, tannic acid, and gallic acid as natural and safe additional crosslinkers dedicated to ENR/silica hybrids to obtain bio-elastomers with improved mechanical properties. Therefore, toxic crosslinkers, such as peroxides or harmful accelerators can be eliminated. The impact of selected natural phenolic compounds on crosslinking effect, mechanical properties, color, and chemical structure of ENR/silica composite have been analyzed. The obtained results indicated that only 3 phr of selected natural phenolic compounds is able to improve crosslinking effect as well as mechanical properties of ENR/silica hybrids. Moreover, some of the prepared materials tend to regain mechanical properties after reprocessing. Such materials containing only natural and safe ingredients have a chance of becoming novel elastomeric biomaterials dedicated to biomedical applications. 相似文献
78.
The critical temperature of layered Ising models on triangular and honeycomb lattices are calculated in simple, explicit form
for arbitrary distribution of the couplings. 相似文献
79.
80.
首先简要介绍了 copula的一些基本概念和性质 ,然后探讨了一种多元未定权益——二元数字期权的价格与 copula的关系 .结论表明 ,一个二元数字期权的价格恰好是一个 copula函数 ,由此结论进而给出了根据实际数据获得二元数字期权价格的基本思路和步骤 . 相似文献