全文获取类型
收费全文 | 464604篇 |
免费 | 5971篇 |
国内免费 | 2661篇 |
专业分类
化学 | 254102篇 |
晶体学 | 6674篇 |
力学 | 19366篇 |
综合类 | 22篇 |
数学 | 54572篇 |
物理学 | 138500篇 |
出版年
2021年 | 4337篇 |
2020年 | 4695篇 |
2019年 | 5037篇 |
2018年 | 6485篇 |
2017年 | 6336篇 |
2016年 | 9970篇 |
2015年 | 6411篇 |
2014年 | 9469篇 |
2013年 | 22258篇 |
2012年 | 17799篇 |
2011年 | 21592篇 |
2010年 | 14852篇 |
2009年 | 14770篇 |
2008年 | 19389篇 |
2007年 | 19169篇 |
2006年 | 17728篇 |
2005年 | 15976篇 |
2004年 | 15092篇 |
2003年 | 12977篇 |
2002年 | 12691篇 |
2001年 | 13923篇 |
2000年 | 10491篇 |
1999年 | 8258篇 |
1998年 | 6872篇 |
1997年 | 6556篇 |
1996年 | 6378篇 |
1995年 | 5669篇 |
1994年 | 5591篇 |
1993年 | 5451篇 |
1992年 | 6039篇 |
1991年 | 6050篇 |
1990年 | 5787篇 |
1989年 | 5578篇 |
1988年 | 5589篇 |
1987年 | 5456篇 |
1986年 | 5178篇 |
1985年 | 6729篇 |
1984年 | 6837篇 |
1983年 | 5408篇 |
1982年 | 5476篇 |
1981年 | 5466篇 |
1980年 | 5035篇 |
1979年 | 5427篇 |
1978年 | 5558篇 |
1977年 | 5456篇 |
1976年 | 5395篇 |
1975年 | 4976篇 |
1974年 | 4943篇 |
1973年 | 4954篇 |
1972年 | 3493篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
82.
83.
Natalia L. Calvo Sebastian O. SimonettiRubén M. Maggio Teodoro S. Kaufman 《Analytica chimica acta》2015
Exposure of cimetidine (CIM) to dry heat (160–180 °C) afforded, upon cooling, a glassy solid containing new and hitherto unknown products. The kinetics of this process was studied by a second order chemometrics-assisted multi-spectroscopic approach. Proton and carbon-13 nuclear magnetic resonance (NMR), as well as ultraviolet and infrared spectroscopic data were jointly used, whereas multivariate curve resolution with alternating least squares (MCR-ALS) was employed as the chemometrics method to extract process information. It was established that drug degradation follows a first order kinetics. 相似文献
84.
85.
86.
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
87.
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
88.
Synthesis,Electronic Properties and WOLED Devices of Planar Phosphorus‐Containing Polycyclic Aromatic Hydrocarbons 下载免费PDF全文
Dr. François Riobé Rózsa Szűcs Dr. Pierre‐Antoine Bouit Dr. Denis Tondelier Bernard Geffroy Fátima Aparicio Julia Buendía Prof. Luis Sánchez Prof. Régis Réau Prof. László Nyulászi Prof. Muriel Hissler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(17):6547-6556
We describe the synthesis and the physical properties of polyaromatic hydrocarbons (PAHs) containing a phosphorus atom at the edge. In particular, the impact of the successive addition of aromatic rings on the electronic properties was investigated by experimental (UV/Vis absorption, fluorescence, cyclic voltammetry) and theoretical studies (DFT). The physical properties recorded in solution and in the solid state showed that the P‐containing PAHs exhibit properties expected for an emitter in white organic light‐emitting diodes (WOLEDs). 相似文献
89.
90.
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