全文获取类型
收费全文 | 591345篇 |
免费 | 14036篇 |
国内免费 | 7989篇 |
专业分类
化学 | 297318篇 |
晶体学 | 8940篇 |
力学 | 30866篇 |
综合类 | 524篇 |
数学 | 83287篇 |
物理学 | 192435篇 |
出版年
2022年 | 5156篇 |
2021年 | 6277篇 |
2020年 | 6740篇 |
2019年 | 7198篇 |
2018年 | 14630篇 |
2017年 | 15074篇 |
2016年 | 15222篇 |
2015年 | 9113篇 |
2014年 | 12822篇 |
2013年 | 26266篇 |
2012年 | 24898篇 |
2011年 | 34063篇 |
2010年 | 23515篇 |
2009年 | 23377篇 |
2008年 | 29321篇 |
2007年 | 31289篇 |
2006年 | 19918篇 |
2005年 | 21947篇 |
2004年 | 18084篇 |
2003年 | 16170篇 |
2002年 | 14443篇 |
2001年 | 15390篇 |
2000年 | 11943篇 |
1999年 | 9607篇 |
1998年 | 8047篇 |
1997年 | 7679篇 |
1996年 | 7501篇 |
1995年 | 6601篇 |
1994年 | 6474篇 |
1993年 | 6134篇 |
1992年 | 6659篇 |
1991年 | 6688篇 |
1990年 | 6325篇 |
1989年 | 6137篇 |
1988年 | 5793篇 |
1987年 | 5957篇 |
1986年 | 5528篇 |
1985年 | 7053篇 |
1984年 | 7076篇 |
1983年 | 6015篇 |
1982年 | 6126篇 |
1981年 | 5695篇 |
1980年 | 5607篇 |
1979年 | 5989篇 |
1978年 | 6034篇 |
1977年 | 5862篇 |
1976年 | 5902篇 |
1975年 | 5638篇 |
1974年 | 5569篇 |
1973年 | 5785篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
A liquid dewetting method for the determination of the viscoelastic properties of ultrathin polymer films has been extended to study thickness effects on the properties of ultrathin polycarbonate (PC) films. PC films with film thicknesses ranging from 4 to 299 nm were placed on glycerol at temperatures from below the macroscopic glass transition temperature (Tg) to above it with the dewetting responses being monitored. It is found that the isothermal creep results for films of the same thickness, but dewetted at different temperatures can be superposed into one master curve, which is consistent with the fact of PC being a thermorheologically simple material. Furthermore, the results show that the Tg of PC thin films is thickness dependent, but the dependence is weaker than the results for freely standing films and similar to literature data for PC films supported on rigid substrates. It was also found that the rubbery plateau region for the PC films stiffens dramatically, but still less than what has been observed for freely standing polycarbonate films. The rubbery stiffening is discussed in terms of a recently reported model that relates macroscopic segmental dynamics with the stiffening. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1559–1566 相似文献
3.
4.
Nanocomposite hydrogel consisting of Na‐montmorillonite with enhanced mechanical properties 下载免费PDF全文
Ting Li Shuangfei Xiang Piming Ma Huiyu Bai Weifu Dong Mingqing Chen 《Journal of Polymer Science.Polymer Physics》2015,53(14):1020-1026
A new kind of nanocomposite (NC) hydrogel with Na‐montmorillonite (MMT) is presented in this article. The NC hydrogels were synthesized by free radical copolymerization of acrylamide and (3‐acrylamidopropyl) trimethylammonium chloride (ATC) in the presence of MMT and N,N′‐methylene‐bis‐acrylamide used as chemical cross‐linker. Due to the cation‐exchange reaction between MMT and ATC (cationic monomer) during the synthesis of NC hydrogels, MMT platelets were considered chemical “plane” cross‐linkers, different from “point” cross‐linkers. With increasing amount of MMT, the crosslinking degree enhanced, causing a decrease of the swelling degree at equilibrium. Investigations of mechanical properties indicated that NC hydrogels exhibited enhanced strength and toughness, which resulted from chemical interaction between exfoliated MMT platelets and polymer chains in hydrogels. Dynamic shear measurements showed that both storage modulus and loss modulus increased with increasing MMT content. The idea described here provided a new route to prepare hydrogels with high mechanical properties by using alternative natural Na‐MMT. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1020–1026 相似文献
5.
Knyazev A. A. Karyakin M. E. Krupin A. S. Galyametdinov Yu. G. 《Russian Journal of General Chemistry》2015,85(12):2806-2812
Russian Journal of General Chemistry - Hybrid liquid crystal systems with different ratios of the components have been prepared on the basis of 5,5′-di(heptadecyl)-2,2′-bipyridine... 相似文献
6.
7.
8.
We study the full counting statistics of transport electrons through a semiconductor two-level quantum dot with Rashba spin–orbit (SO) coupling, which acts as a nonabelian gauge field and thus induces the electron transition between two levels along with the spin flip. By means of the quantum master equation approach, shot noise and skewness are obtained at finite temperature with two-body Coulomb interaction. We particularly demonstrate the crucial effect of SO coupling on the super-Poissonian fluctuation of transport electrons, in terms of which the SO coupling can be probed by the zero-frequency cumulants. While the charge currents are not sensitive to the SO coupling. 相似文献
9.
10.