全文获取类型
收费全文 | 417篇 |
免费 | 17篇 |
国内免费 | 9篇 |
专业分类
化学 | 279篇 |
晶体学 | 4篇 |
力学 | 18篇 |
数学 | 59篇 |
物理学 | 83篇 |
出版年
2023年 | 1篇 |
2022年 | 8篇 |
2021年 | 18篇 |
2020年 | 14篇 |
2019年 | 28篇 |
2018年 | 31篇 |
2017年 | 27篇 |
2016年 | 28篇 |
2015年 | 12篇 |
2014年 | 25篇 |
2013年 | 57篇 |
2012年 | 38篇 |
2011年 | 26篇 |
2010年 | 13篇 |
2009年 | 22篇 |
2008年 | 19篇 |
2007年 | 22篇 |
2006年 | 13篇 |
2005年 | 8篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 1篇 |
2001年 | 5篇 |
1997年 | 2篇 |
1994年 | 1篇 |
1989年 | 2篇 |
1985年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1974年 | 2篇 |
排序方式: 共有443条查询结果,搜索用时 15 毫秒
71.
Chiral SU2 × SU2 breaking, Cabibbo angle, non-electromagnetic isospin breaking, η → 3π decay rate, and pion and kaon mass differences are related to one another in a nonlinear Lagrangian model of broken chiral SU3 × SU3 symmetry. The agreement with experiment is very good. 相似文献
72.
Transmittance measurements were carried out for LiF thin films directly after preparation, then one day, one week, four weeks
and six weeks later. The aging effect on the optical properties of the film was thus studied. This showed that the aged LiF
films have refractive indices larger than those of fresh films. 相似文献
73.
Jamal Aalaie Ebrahim Vasheghani-Farahani Mohammad Ali Semsarzadeh Ali Rahmatpour 《Journal of Macromolecular Science: Physics》2013,52(5):1017-1027
Novel semi-Interpenetrating Polymer Network (semi-IPN) hydrogels based on partially Hydrolyzed Polyacrylamide (HPAM) and Poly(Vinyl Alcohol) (PVA) were prepared by solution crosslinking using chromium triacetate. Effects of PVA content on the gelation process and swelling behavior in tap water and different electrolyte solutions were investigated. Study of the gelation behavior using dynamic rheometery showed that the limiting storage modulus of the semi-IPN gels decreased with increasing PVA content. It was also found that increasing the PVA content increases the loss factor, indicating that the viscous properties of this gelling system increase more strongly than the elastic properties. The swelling ratio of the semi-IPN gels in tap water decreased as the concentration of the PVA increased. However, the semi-IPN gels showed lower salt sensitivity factor in synthetic oil reservoir water as compared with HPAM gels. Therefore, they are potentially good candidates for enhanced oil recovery applications. 相似文献
74.
75.
Ebrahim Kianmehr Narges Shamsaei Zafarghandi Mohammad Ghanbari 《Molecular diversity》2013,17(2):383-388
Novel $N$ -alkyl-2-(alkylthio)-1 $H$ -imidazole derivatives were synthesized in a single step by an efficient and simple method in high yields. Readily available starting materials, mild reaction conditions, operational simplicity and novelty are the key advantages of this method. Besides their novel structures, these compounds may have important biological activities and industrial applications. 相似文献
76.
The behavior of composite coated Al electrodes fabricated by surface mechanical alloying ‘SMA’ was studied. The work was accomplished using Cyclic voltammetry and electrochemical impedance spectroscopy (EIS) techniques in alkaline media were done at room temperature. Results show hydroxyl ions accumulate on the surface due to Al deformation micro cavities filling with until full charge blockage reached. A barrier cover layer development causing an increase of both resistance and capacitance as it becomes more stable and thinner with exposure time increase. Migrating hydroxyl ion inside micro cavity changed its composition from Al2O3 to stable tetrahedral aluminate ions. Therefore future benefits could be reached by developing such surfaces having charge accumulation that enables environmental interaction. 相似文献
77.
Microchimica Acta - Accurate detection of temperature and oxygen concentration at the cellular level is important in tumor diagnosis. Multifunctional nanocomposites are described that consist of... 相似文献
78.
In this article, the palladium (II) mixed-ligand complex synthesized with reduced graphene oxides containing tetraethoxysilane and menthone oxime was used as an efficient solid catalyst for the Heck coupling reaction. To maintain stability and catalytic activity in the C–C bond reaction, graphene was considered due to the available surface as the solid support. Then, the structure of new heterogeneous catalyst was investigated by FT-IR, UV–Vis DRS, FE-SEM, EDX, AFM, XRD, ICP-OES, Raman, and TGA. The newly synthesized nanocatalyst have beneficial properties, including product’s easy separation, the shorter time to react, purity products (yield 79–99%), and easier work-up procedure. Furthermore, the catalyst was reused six times without significant degradation in catalytic activity and performance. 相似文献
79.
Ebrahim Salehi 《Applications of Mathematics》2016,61(5):565-584
In this paper, we consider the linear and circular consecutive k-out-of-n systems consisting of arbitrarily dependent components. Under the condition that at least n?r+1 components (r ≤ n) of the system are working at time t, we study the reliability properties of the residual lifetime of such systems. Also, we present some stochastic ordering properties of residual lifetime of consecutive k-out-of-n systems. In the following, we investigate the inactivity time of the component with lifetime Tr:n at the system level for the consecutive k-out-of-n systems under the condition that the system is not working at time t > 0, and obtain some stochastic properties of this conditional random variable. 相似文献
80.