全文获取类型
收费全文 | 2856篇 |
免费 | 449篇 |
国内免费 | 448篇 |
专业分类
化学 | 2369篇 |
晶体学 | 56篇 |
力学 | 127篇 |
综合类 | 35篇 |
数学 | 272篇 |
物理学 | 894篇 |
出版年
2024年 | 5篇 |
2023年 | 97篇 |
2022年 | 137篇 |
2021年 | 161篇 |
2020年 | 222篇 |
2019年 | 196篇 |
2018年 | 153篇 |
2017年 | 132篇 |
2016年 | 191篇 |
2015年 | 212篇 |
2014年 | 208篇 |
2013年 | 235篇 |
2012年 | 252篇 |
2011年 | 240篇 |
2010年 | 210篇 |
2009年 | 179篇 |
2008年 | 169篇 |
2007年 | 138篇 |
2006年 | 110篇 |
2005年 | 82篇 |
2004年 | 65篇 |
2003年 | 60篇 |
2002年 | 56篇 |
2001年 | 53篇 |
2000年 | 27篇 |
1999年 | 21篇 |
1998年 | 16篇 |
1997年 | 15篇 |
1996年 | 17篇 |
1995年 | 7篇 |
1994年 | 12篇 |
1993年 | 17篇 |
1992年 | 8篇 |
1991年 | 12篇 |
1990年 | 8篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 5篇 |
1981年 | 1篇 |
1976年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有3753条查询结果,搜索用时 0 毫秒
81.
A new one-step synthesis of 3-hydroxymethylbenzofuran, based on intramolecular cyclization of 2- (methoxymethyl)-2-(2'-methoxymethyl-4'-methylphenyl)-butanone I under diluted hydrochloric acid in THF, was developed. The mechanism for this process was investigated via chemical equilibrium shift of tautomer in acidic conditions. The applicability of this new method was studied further in this paper. 相似文献
82.
83.
84.
Jie Miao Weiwei He Lifen Zhang Yi Wang Zhenping Cheng Xiulin Zhu 《Journal of polymer science. Part A, Polymer chemistry》2012,50(11):2194-2200
In this work, living radical polymerizations of a water‐soluble monomer poly(ethylene glycol) monomethyl ether methacylate (PEGMA) in bulk with low‐toxic iron catalyst system, including iron chloride hexahydrate and triphenylphosphine, were carried out successfully. Effect of reaction temperature and catalyst concentration on the polymerization of PEGMA was investigated. The polymerization kinetics showed the features of “living”/controlled radical polymerization. For example, Mn,GPC values of the resultant polymers increased linearly with monomer conversion. A faster polymerization of PEGMA could be obtained in the presence of a reducing agent Fe(0) wire or ascorbic acid. In the case of Fe(0) wire as the reducing agent, a monomer conversion of 80% was obtained in 80 min of reaction time at 90 °C, yielding a water‐soluble poly(PEGMA) with Mn = 65,500 g mol?1 and Mw/Mn = 1.39. The features of “living”/controlled radical polymerization of PEGMA were verified by analysis of chain‐end and chain‐extension experiments. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
85.
Jincheng Li Huan Liu Chaoying Wang Lidong Wu Dan Liu 《Analytical and bioanalytical chemistry》2016,408(24):6537-6544
86.
As an emerging donor building block, naphthodithiophene (NDT) is causing more concerns in the field of organic semiconductors. With the rigid and coplanar molecule structure, NDT will exhibit more application space relying on its own advantage for facilitating the charge carrier transport. In this review article, we have summarized the development progress on the NDT-based donor materials for solution processed organic solar cells. Discussions and comments on those representative NDT type materials about structure and property are also presented. 相似文献
87.
Yanfeng Chu Huan Yu Yunti Zhang Guangyan Zhang Yingying Ma Renxi Zhuo Xulin Jiang 《Journal of polymer science. Part A, Polymer chemistry》2014,52(23):3346-3355
Biodegradable amphiphilic ABC Y‐shaped triblock copolymer (MPBC) containing PEG, PBLA, and PCL segments was synthesized via the combination of enzymatic ring‐opening polymerization (ROP) of epsilon‐caprolactone, ROP of BLA‐N‐carboxyanhydride and click chemistry, where PEG, PBLA, and PCL are poly(ethylene glycol), poly(benzyl‐l ‐aspartate), and polycaprolactone, respectively. Propynylamine was employed as ROP initiator for the preparation of alkynyl‐terminated PBLA and methyloxy‐PEG with hydroxyl and azide groups at the chain‐end was used as enzymatic ROP initiator for synthesis of monoazido‐midfunctionalized block copolymer mPEG‐b‐PCL. The subsequent click reaction led to the formation of Y‐shaped asymmetric heteroarm terpolymer MPBC. The polymer structures were characterized by different analyses. The MPBC terpolymer self‐assembled into micelles and physically encapsulated drug doxorubicin (DOX) to form DOX‐loaded micelles, which showed good stability and slow drug release. In vitro cytotoxicity study indicated that the MPBC micelles were nontoxic and the DOX‐loaded micelles displayed obvious anticancer activity similar to free DOX against HeLa cells. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3346–3355 相似文献
88.
89.
90.
Wang Fei Cressault Yann Teulet Philippe Li Huan Yang Ke 《Plasma Chemistry and Plasma Processing》2019,39(4):1049-1069
Plasma Chemistry and Plasma Processing - Gas tungsten arc welding (GTAW), a widely used industrial process, is one of the most intense artificial sources of optical radiation. This paper presents a... 相似文献