全文获取类型
收费全文 | 793647篇 |
免费 | 8536篇 |
国内免费 | 2235篇 |
专业分类
化学 | 411691篇 |
晶体学 | 11300篇 |
力学 | 38371篇 |
综合类 | 26篇 |
数学 | 105246篇 |
物理学 | 237784篇 |
出版年
2021年 | 7044篇 |
2020年 | 7667篇 |
2019年 | 8575篇 |
2018年 | 11195篇 |
2017年 | 11162篇 |
2016年 | 16320篇 |
2015年 | 9583篇 |
2014年 | 15298篇 |
2013年 | 35810篇 |
2012年 | 27619篇 |
2011年 | 33346篇 |
2010年 | 24298篇 |
2009年 | 24063篇 |
2008年 | 31261篇 |
2007年 | 30996篇 |
2006年 | 28640篇 |
2005年 | 25611篇 |
2004年 | 23743篇 |
2003年 | 21152篇 |
2002年 | 20937篇 |
2001年 | 22663篇 |
2000年 | 17509篇 |
1999年 | 13677篇 |
1998年 | 11576篇 |
1997年 | 11280篇 |
1996年 | 10802篇 |
1995年 | 9776篇 |
1994年 | 9692篇 |
1993年 | 9361篇 |
1992年 | 10126篇 |
1991年 | 10484篇 |
1990年 | 10151篇 |
1989年 | 9815篇 |
1988年 | 9678篇 |
1987年 | 9517篇 |
1986年 | 9044篇 |
1985年 | 11692篇 |
1984年 | 12087篇 |
1983年 | 9923篇 |
1982年 | 10303篇 |
1981年 | 9897篇 |
1980年 | 9298篇 |
1979年 | 9996篇 |
1978年 | 10300篇 |
1977年 | 10177篇 |
1976年 | 10066篇 |
1975年 | 9547篇 |
1974年 | 9417篇 |
1973年 | 9590篇 |
1972年 | 6916篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
122.
ABSTRACT A new density functional for the study of associating inhomogeneous fluids based on Wertheim's first-order thermodynamic perturbation theory is presented and compared to the most currently used associating density functionals. This functional is developed using the weighted density approximation in the range of association of hard spheres. We implement this functional within the framework of classical density functional theory together with modified fundamental measure theory to account for volume exclusion of hard spheres. This approach is tested against molecular simulations from literature of pure associating hard spheres and mixtures of non-associationg and associating hard spheres with different number of bonding sites close to a hard uniform wall. Furthermore, we compare and review our results with the performance of associating functionals from literature, one based on fundamental measure theory and the inhomogeneous version of Wertheim's perturbation theory. Results obtained with classical DFT and the three functionals show excellent agreement with molecular simulations in systems with one hard wall. For the cases of small pores where only one or two layers of fluid are allowed discrepancies between results with classical DFT and molecular simulations were found. 相似文献
123.
124.
125.
126.
Journal of Structural Chemistry - Thermodynamic characteristics are calculated for aqueous alkanolamine solutions that are obtained by substituting alkyl radicals for the protons in the amino group... 相似文献
127.
Physical aging in amorphous poly(ethylene furanoate): Enthalpic recovery,density, and oxygen transport considerations 下载免费PDF全文
Steven K. Burgess Christopher R. Mubarak Robert M. Kriegel William J. Koros 《Journal of Polymer Science.Polymer Physics》2015,53(6):389-399
The current work utilizes three separate techniques to study the physical aging process in amorphous poly(ethylene furanoate) (PEF), which is a recently introduced engineering thermoplastic with enhanced properties compared to petroleum‐sourced poly(ethylene terephthalate). Differential scanning calorimetry aging experiments were conducted at multiple aging temperatures and times, and the resultant enthalpic recovery values compared to the theoretical maximum enthalpy loss evaluated from calculations involving extrapolation of the equilibrium liquid line. Density measurements reveal densification of the matrix for the aged versus unaged samples, and provide an estimate for the reduction in free volume for the aged samples. Complementary oxygen permeation and pressure‐decay sorption experiments provide independent verification of the free volume reduction mechanism for physical aging in glassy polymers. The current work provides the first detailed aging study for PEF. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 389–399 相似文献
128.
129.
Amphiphilic thermoset elastomers from metal‐free,click crosslinking of PEG‐grafted silicone surfactants 下载免费PDF全文
Michael A. Brook Frances Lasowski Heather Sheardown 《Journal of polymer science. Part A, Polymer chemistry》2015,53(9):1082-1093
The hydrophobicity of silicone elastomers can compromise their utility in some biomaterials applications. Few effective processes exist to introduce hydrophilic groups onto a polysiloxane backbone and subsequently crosslink the material into elastomers. This problem can be overcome through the utilization of metal‐free click reactions between azidoalkylsilicones and alkynyl‐modified silicones and/or PEGs to both functionalize and crosslink silicone elastomers. Alkynyl‐functional PEG was clicked onto a fraction of the available azido groups of a functional polysiloxane, yielding azido reactive PDMS‐g‐PEG rake surfactants. The reactive polymers were then used to crosslink alkynyl‐terminated PDMS of different molecular weights. Using simple starting materials, this generic yet versatile method permits the preparation and characterization of a library of amphiphilic thermoset elastomers that vary in their composition, crosslink density, elasticity, hydrogel formation, and wettability. An appropriate balance of PEG length and crosslink density leads to a permanently highly wettable silicone elastomer that demonstrated very low levels of protein adsorption. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1082–1093 相似文献