全文获取类型
收费全文 | 5313篇 |
免费 | 126篇 |
国内免费 | 24篇 |
专业分类
化学 | 3842篇 |
晶体学 | 28篇 |
力学 | 112篇 |
数学 | 539篇 |
物理学 | 942篇 |
出版年
2022年 | 41篇 |
2021年 | 50篇 |
2020年 | 65篇 |
2019年 | 62篇 |
2018年 | 49篇 |
2017年 | 45篇 |
2016年 | 94篇 |
2015年 | 76篇 |
2014年 | 88篇 |
2013年 | 217篇 |
2012年 | 280篇 |
2011年 | 332篇 |
2010年 | 187篇 |
2009年 | 147篇 |
2008年 | 304篇 |
2007年 | 295篇 |
2006年 | 287篇 |
2005年 | 296篇 |
2004年 | 281篇 |
2003年 | 207篇 |
2002年 | 236篇 |
2001年 | 102篇 |
2000年 | 109篇 |
1999年 | 66篇 |
1998年 | 72篇 |
1997年 | 50篇 |
1996年 | 94篇 |
1995年 | 51篇 |
1994年 | 69篇 |
1993年 | 90篇 |
1992年 | 74篇 |
1991年 | 50篇 |
1990年 | 46篇 |
1989年 | 53篇 |
1988年 | 37篇 |
1987年 | 43篇 |
1986年 | 36篇 |
1985年 | 60篇 |
1984年 | 42篇 |
1983年 | 32篇 |
1982年 | 66篇 |
1981年 | 39篇 |
1980年 | 56篇 |
1979年 | 39篇 |
1978年 | 52篇 |
1977年 | 46篇 |
1976年 | 43篇 |
1975年 | 53篇 |
1974年 | 33篇 |
1973年 | 41篇 |
排序方式: 共有5463条查询结果,搜索用时 15 毫秒
871.
Wang Wan Monte S. Bedford Catherine A. Conrad Xiaoyan Yang Rhett C. Smith 《Journal of polymer science. Part A, Polymer chemistry》2019,57(11):1173-1179
A series of 10 polythiophene derivatives is reported, in which each polymer has a different percentage of carboxylic acid‐bearing repeat units. The properties of these polymers are explored under acidic conditions, where the carboxylic acid moieties remain neutral, and under basic conditions, where the carboxylic acid units become anionic carboxylates. The properties that are examined for both solutions and films include UV–vis absorption spectroscopy, photoluminescence spectroscopy, and red‐edge optical band gaps. All the properties studied are strongly dependent both on protonation state and percentage of carboxylic acid/carboxylate side chains along the polymer backbone. The anionic form of each polythiophene derivative was also used in layer‐by‐layer film deposition with a cationic phosphonium polyelectrolyte. The film growth process was studied by spectroscopic techniques to assess the influence of side‐chain composition on the film growth and optical properties. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 相似文献
872.
Kyung Min Lee Brandon M. Lynch Paul Luchette Timothy J. White 《Journal of polymer science. Part A, Polymer chemistry》2014,52(6):876-882
The photomechanical response and photochemistry of a conventional, unsubstituted azobenzene‐functionalized liquid crystalline polymer network (azo‐LCN) is contrasted to that of an analogous material prepared with meta‐fluorinated azobenzene chromophores. The polydomain azo‐LCN materials exhibit nearly identical thermomechanical and optical properties. Photomechanical characterization indicates that the fluorination of the azobenzene chromophore reduces the deflection of cantilevers composed of the materials by 50%, which spectroscopic analysis reveals is due to a reduction in the ability of this material to isomerize and potentially reorient. This work is further confirmation that the underlying photochemistry of azobenzene is a primary contributor to the generation of photomechanical work in these materials. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 876–882 相似文献
873.
874.
Lee Kookjin Elman Howard C. Powell Catherine E. Lee Dongeun 《BIT Numerical Mathematics》2022,62(3):965-994
BIT Numerical Mathematics - In uncertainty quantification, it is commonly required to solve a forward model consisting of a partial differential equation (PDE) with a spatially varying uncertain... 相似文献
875.
Nikolaos V. Tzouras Dr. Fady Nahra Dr. Laura Falivene Prof. Dr. Luigi Cavallo Marina Saab Prof. Dr. Kristof Van Hecke Dr. Alba Collado Dr. Christopher J. Collett Prof. Dr. Andrew D. Smith Prof. Dr. Catherine S. J. Cazin Prof. Dr. Steven P. Nolan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(20):4515-4519
We have been puzzled by the involvement of weak organic and inorganic bases in the synthesis of metal–N-heterocyclic carbene (NHC) complexes. Such bases are insufficiently strong to permit the presumed required deprotonation of the azolium salt (the carbene precursor) prior to metal binding. Experimental and computational studies provide support for a base-assisted concerted process that does not require free NHC formation. The synthetic protocol was found applicable to a number of transition-metal- and main-group-centered NHC compounds and could become the synthetic route of choice to form M–NHC bonds. 相似文献
876.
AbstractExperimental studies conducted on some species of Mediterranean red algae allowed to identify Sphaerococcus coronopifolius Stackhouse as a valid alternative to the Pacific alga Gloiopeltis furcata (Postels & Ruprecht) J. Agardh, for the extraction of a material usable as natural consolidant and adhesive in the field of restoration. Promising results have been observed by comparing the extracts obtained from these two algae after the same extraction procedure. Chemical analysis (FTIR) revealed that S. coronopifolius has qualities similar to G. furcata. Even more promising results for S. coronopifolius compared to G. furcata were observed after the analysis of pH and conductivity, and the adhesion tests carried out on both extracts. 相似文献
877.
878.
879.
880.
Catherine S. Branch Laura G. van Poppel Simon G. Bott Andrew R. Barron 《Journal of chemical crystallography》1999,29(9):993-996
The molecular structure of (tBu)3Al[O=C(OPh)2] has been determined. The increase in the C=O bond distance [1.258(4) Å] when compared to free O=C(OPh)2 [1.191(3) Å], is presented in respect to the activating ability of aluminum Lewis acids. Crystal data: monoclinic, P21/n, a = 10.653(2), b = 18.486(4), c = 14.551(3) Å, = 108.07(3)°, and V = 2724.3(9) Å3 for Z = 4. 相似文献