全文获取类型
收费全文 | 442437篇 |
免费 | 9803篇 |
国内免费 | 4691篇 |
专业分类
化学 | 226833篇 |
晶体学 | 5430篇 |
力学 | 21482篇 |
综合类 | 247篇 |
数学 | 63602篇 |
物理学 | 139337篇 |
出版年
2021年 | 2864篇 |
2020年 | 3363篇 |
2019年 | 3216篇 |
2018年 | 12036篇 |
2017年 | 12837篇 |
2016年 | 9417篇 |
2015年 | 5668篇 |
2014年 | 6431篇 |
2013年 | 16521篇 |
2012年 | 18069篇 |
2011年 | 28637篇 |
2010年 | 17581篇 |
2009年 | 17364篇 |
2008年 | 24788篇 |
2007年 | 28066篇 |
2006年 | 14094篇 |
2005年 | 19697篇 |
2004年 | 14779篇 |
2003年 | 13066篇 |
2002年 | 10875篇 |
2001年 | 10897篇 |
2000年 | 8596篇 |
1999年 | 6906篇 |
1998年 | 5585篇 |
1997年 | 5348篇 |
1996年 | 5583篇 |
1995年 | 4890篇 |
1994年 | 4594篇 |
1993年 | 4336篇 |
1992年 | 4795篇 |
1991年 | 4587篇 |
1990年 | 4245篇 |
1989年 | 4005篇 |
1988年 | 4308篇 |
1987年 | 3939篇 |
1986年 | 3783篇 |
1985年 | 5469篇 |
1984年 | 5537篇 |
1983年 | 4475篇 |
1982年 | 4814篇 |
1981年 | 4855篇 |
1980年 | 4585篇 |
1979年 | 4722篇 |
1978年 | 4731篇 |
1977年 | 4627篇 |
1976年 | 4631篇 |
1975年 | 4521篇 |
1974年 | 4377篇 |
1973年 | 4578篇 |
1972年 | 2572篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
141.
Mathematical Notes - 相似文献
142.
143.
144.
The stable phase equilibria of quaternary systems LiBr-NaBr-MgBr2-H2O and LiBr-KBr-MgBr2-H2O at 298.15 K were studied by both experimental measurement(isothermal solution saturation method) and theoretical prediction(Pitzer model). The solubilities of the saturated solution have been determined experimentally and two stable phase diagrams and relevant water diagrams of the two quaternary systems were obtained. Results show that quaternary system LiBr-NaBr-MgBr2-H2O is hydrate II type as NaBr and NaBr·2H2O coexistence. Its phase diagram consists of only one invariant point, four univariant curves, and five crystallization fields. The quaternary system LiBr-KBr-MgBr2-H2O is a complex type as the double salt KBr·MgBr2·6H2O formed. In addition to this double salt, the three single salts LiBr·2H2O, KBr and MgBr2·6H2O also crystallize. In this paper, the solubilities of phase equilibria in above quaternary systems were also calculated by the Pitzer's electrolyte solution model. All the needed parameters can be obtained from the literature or be fitted by experimental data. On the Basis of the experimental and calculated results, the phase diagram of the quaternary system was plotted for comparison. It shows that the calculation results are consistent with the experimental ones. 相似文献
145.
146.
Kinetics and Catalysis - A series of Cu-SSZ-13@CeO2 catalysts with surface modification with CeO2 was prepared by the modified self-resemble method based on the one-pot synthesized Cu-SSZ-13... 相似文献
147.
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
148.
149.
150.
Sh. M. Khaliullin V. D. Zhuravlev V. G. Bamburov L. V. Ermakova 《Physics of Atomic Nuclei》2015,78(12):1382-1388
Submicron CaZrO3 powder is obtained in combustion reactions (solution combustion synthesis—SCS) with glycine. It is found that SCS reduces the sintering temperature of CaZrO3 powders. The dielectric properties of calcium zirconate ceramics are studied by the electrochemical impedance method. It is shown that a ceramics of powders obtained by the SCS method has high dielectric characteristics. 相似文献