全文获取类型
收费全文 | 58157篇 |
免费 | 13691篇 |
国内免费 | 5098篇 |
专业分类
化学 | 57199篇 |
晶体学 | 622篇 |
力学 | 1962篇 |
综合类 | 256篇 |
数学 | 4684篇 |
物理学 | 12223篇 |
出版年
2024年 | 53篇 |
2023年 | 507篇 |
2022年 | 618篇 |
2021年 | 994篇 |
2020年 | 2175篇 |
2019年 | 3401篇 |
2018年 | 1822篇 |
2017年 | 1419篇 |
2016年 | 4465篇 |
2015年 | 4568篇 |
2014年 | 4732篇 |
2013年 | 5690篇 |
2012年 | 5031篇 |
2011年 | 4288篇 |
2010年 | 4323篇 |
2009年 | 4259篇 |
2008年 | 3964篇 |
2007年 | 3243篇 |
2006年 | 2817篇 |
2005年 | 2773篇 |
2004年 | 2336篇 |
2003年 | 2059篇 |
2002年 | 2882篇 |
2001年 | 2058篇 |
2000年 | 1894篇 |
1999年 | 959篇 |
1998年 | 515篇 |
1997年 | 464篇 |
1996年 | 431篇 |
1995年 | 366篇 |
1994年 | 308篇 |
1993年 | 284篇 |
1992年 | 201篇 |
1991年 | 181篇 |
1990年 | 183篇 |
1989年 | 133篇 |
1988年 | 97篇 |
1987年 | 75篇 |
1986年 | 73篇 |
1985年 | 76篇 |
1984年 | 40篇 |
1983年 | 43篇 |
1982年 | 38篇 |
1981年 | 27篇 |
1980年 | 16篇 |
1979年 | 12篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1974年 | 4篇 |
1916年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
You‐Liang Zhao Chuan‐Fu Chen Fu Xi 《Journal of polymer science. Part A, Polymer chemistry》2003,41(14):2156-2165
The atom transfer radical copolymerization of N‐substituted maleimides such as N‐phenylmaleimide (PhMI), N‐cyclohexylmaleimide (ChMI), and N‐butylmaleimide (NBMI) with styrene initiated with dendritic polyarylether 2‐bromoisobutyrates in an ionic liquid, 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([bmim][PF6]), at room temperature and anisole at 110 °C was investigated. The dendritic‐linear block copolymers obtained in ionic liquid possessed well‐defined molecular weight and low polydispersity (1.05 < Mw/Mn < 1.32) and could be used as a macroinitiator for chain‐extension polymerization, suggesting the living nature of the reaction system. The ionic liquids containing catalyst could be recycled in the atom transfer radical polymerization systems without further treatment. Compared with polymerization conducted in anisole, the polymerization in ionic liquid had a stronger tendency for alternation. The tendency for alternation decreased in the order PhMI > NBMI > ChMI in [bmim][PF6] and PhMI > ChMI > NBMI in anisole. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2156–2165, 2003 相似文献
112.
报道了硅基有机微腔的电致发光(EL).该微腔由上半透明金属膜、中心有源多层膜和多孔硅分布Bragg反射镜(PS DBR)组成.半透明金属膜由Ag(20nm)构成,充当发光器件的负电极和微腔的上反射镜.有源多层膜由Al (1 nm) / LiF(05 nm) /Alq3/Alq3:DCJTB/NPB/CuPc/ITO/SiO2组成,其中的Al/LiF为电子注入层,ITO为正电极,SiO2为使正、负电极电隔离的介质层.该PS DBR是采用设备简单、成本低廉且非常省时的电化学腐蚀法用单晶Si来制备的;该PS
关键词:
电化学腐蚀
电致发光
窄峰发射
硅基有机微腔 相似文献
113.
114.
Julien Ferrari Christian Terreaux Tibor Kurtn Attila Szikszai‐Kiss Sndor Antus JeromeD. Msonthi Kurt Hostettmann 《Helvetica chimica acta》2003,86(8):2768-2778
Investigation of the methanol extract of the roots of Gnidia involucrata (Thymelaeaceae) led to the isolation and characterization of two new 3,8″‐biflavonoid diastereoisomers, named GB‐4 ( 6a ) and GB‐4a ( 6b ). Their absolute configurations were determined in mixture by on‐line LC/CD measurements, which also allowed the revision of absolute configurations of the biflavanoids GB‐1 and GB‐2, and the configurational assignment of GB‐3. 相似文献
115.
116.
有限循环群的Fuzzy子群的等价类数 总被引:4,自引:2,他引:2
有限循环群G的F子群可以有无数个.但是.若当两个F子群的水平集构成的集合相等就称其等价的话,那么其等价类数是有限的。通过研究群的合成群列、商群列以及数的因数列和极大因数列找出了有限循环群的极大F子群和F子群的等价类数的求解公式.并给出二者之间的关系式. 相似文献
117.
118.
Aiqing Zhang Xiangdan Li Changwoon Nah Keejun Hwang Myong‐Hoon Lee 《Journal of polymer science. Part A, Polymer chemistry》2003,41(1):22-29
A soluble aromatic polyimide was chloromethylated via a reaction with chloromethyl methyl ether in the presence of tin(IV) chloride to produce a new starting material for the modification of aromatic polyimides. The chemical structure of the resulting polymer was confirmed by 1H NMR and Fourier transform infrared spectroscopy. The maximum number of chloromethyl groups per repeat unit was 1.81. The chloromethylated polyimide was stable up to 250 °C and soluble in both chloroform and tetrahydrofuran. So that its utilization for further modification could be demonstrated, cinnamic acid was reacted with the formed polyimide, and it produced a new photosensitive polyimide with a cinnamoyl side chain. The photosensitivity of the resulting polyimide was investigated with ultraviolet spectroscopic methods. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 22–29, 2003 相似文献
119.
The goal of the paper is to analyse properties of solutions for linear thermoelastic systems of type III in one space variable. Our approach does not use energy methods, it bases on a special diagonalization procedure which is different in different parts of the phase space. This procedure allows to derive explicit representations of solutions. These representations help to prove results for well‐posedness of the Cauchy problem, LP–Lq decay estimates on the conjugate line and results for propagation of singularities. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
120.
The original article to which this Erratum refers was published in Journal of Graph Theory 47:129–146,2004 . 相似文献