全文获取类型
收费全文 | 3753篇 |
免费 | 131篇 |
国内免费 | 25篇 |
专业分类
化学 | 2475篇 |
晶体学 | 64篇 |
力学 | 88篇 |
数学 | 407篇 |
物理学 | 875篇 |
出版年
2023年 | 26篇 |
2022年 | 59篇 |
2021年 | 66篇 |
2020年 | 65篇 |
2019年 | 63篇 |
2018年 | 65篇 |
2017年 | 52篇 |
2016年 | 131篇 |
2015年 | 102篇 |
2014年 | 117篇 |
2013年 | 247篇 |
2012年 | 246篇 |
2011年 | 319篇 |
2010年 | 177篇 |
2009年 | 177篇 |
2008年 | 236篇 |
2007年 | 210篇 |
2006年 | 186篇 |
2005年 | 179篇 |
2004年 | 169篇 |
2003年 | 137篇 |
2002年 | 129篇 |
2001年 | 70篇 |
2000年 | 64篇 |
1999年 | 40篇 |
1998年 | 32篇 |
1997年 | 26篇 |
1996年 | 28篇 |
1995年 | 24篇 |
1994年 | 23篇 |
1993年 | 23篇 |
1992年 | 26篇 |
1991年 | 14篇 |
1990年 | 29篇 |
1989年 | 32篇 |
1988年 | 21篇 |
1987年 | 14篇 |
1986年 | 18篇 |
1985年 | 19篇 |
1984年 | 23篇 |
1983年 | 17篇 |
1982年 | 14篇 |
1981年 | 29篇 |
1980年 | 17篇 |
1979年 | 16篇 |
1978年 | 21篇 |
1977年 | 17篇 |
1976年 | 19篇 |
1975年 | 18篇 |
1974年 | 11篇 |
排序方式: 共有3909条查询结果,搜索用时 0 毫秒
1.
2.
The fuzzification of convex sets in median algebras is considered, and some of their properties are investigated. A characterization of finite valued fuzzy convex set is given. 相似文献
3.
Jong Chan Lee Jin Young Park So Young Yoon Yong Hun Bae Seung Jun Lee 《Tetrahedron letters》2004,45(1):191-193
A novel and direct method for the synthesis of α-halocarbonyl compounds using sequential treatment of carbonyl compounds with [hydroxy(tosyloxy)iodo]benzene followed by magnesium halides under solvent-free microwave irradiation conditions is described. 相似文献
4.
5.
In this paper, by extending Kucera's idea to the function field case, we obtain several determinant formulas involving the real class number and the relative class number of any subfield of cyclotomic function fields. We also provide several examples using these determinant formulas.
6.
Woo-Soo Kim Ruth Houbertz Tae-Ho Lee Byeong-Soo Bae 《Journal of Polymer Science.Polymer Physics》2004,42(10):1979-1986
Inorganic–organic hybrid polymers have been developed and tested for evaluation in optical and electrical applications. Although hybrid inorganic–organic polymers can be synthesized by sol–gel chemistry at first, the physical properties of hybrid inorganic–organic polymers are changed during thin film-making processes, that is, photocuring and thermal curing. To investigate the effect of photoinitiator on the material properties during processing, a model system containing methacrylic groups as organically polymerizable units was selected. The conversion of CC double bond of methacrylic groups depending on some kinds of photoinitiator quantities was characterized by Fourier transform infrared spectroscopy. It was confirmed to correlate the degree of CC double bond conversion with the refractive indices. Thermodynamically, the enthalpy of the photopolymerization of hybrid polymer was investigated by UV–DSC. UV–DSC spectra showed the exothermic nature of photopolymerization of ORMOCER® to be in dependence of photoinitiator quantities. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1979–1986, 2004 相似文献
7.
8.
Jem‐Kun Chen I‐Kuan Lin Fu‐Hsiang Ko Chih‐Feng Huang Kuo‐Shen Chen Chia‐Hao Chan Feng‐Chih Chang 《Journal of Polymer Science.Polymer Physics》2004,42(22):4063-4074
Polybenzoxazine (PBZZ) thin films can be fabricated by the plasma‐polymerization technique with, as the energy source, plasmas of argon, oxygen, or hydrogen atoms and ions. When benzoxazine (BZZ) films are polymerized through the use of high‐energy argon atoms, electronegative oxygen atoms, or excited hydrogen atoms, the PBZZ films that form possess different properties and morphologies in their surfaces. High‐energy argon atoms provide a thermodynamic factor to initiate the ring‐opening polymerization of BZZ and result in the polymer surface having a grid‐like structure. The ring‐opening polymerization of the BZZ film that is initiated by cationic species such as oxygen atoms in plasma, is propagated around nodule structures to form the PBZZ. The excited hydrogen atom plasma initiates both polymerization and decomposition reactions simultaneously in the BZZ film and results in the formation of a porous structure on the PBZZ surface. We evaluated the surface energies of the PBZZ films polymerized by the action of these three plasmas by measuring the contact angles of diiodomethane and water droplets. The surface roughness of the films range from 0.5 to 26 nm, depending on the type of carrier gas and the plasma‐polymerization time. By estimating changes in thickness, we found that the PBZZ film synthesized by the oxygen plasma‐polymerization process undergoes the slowest rate of etching in CF4 plasma. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4063–4074, 2004 相似文献
9.
Dong Jun Kang Tae-Ho Lee Byeong-Soo Bae 《Journal of Sol-Gel Science and Technology》2004,31(1-3):113-116
Fluorinated inorganic-organic hybrid materials (HYBRIMER) were successfully prepared from fluoroalkylsilanes (FASs) containing fluoro-alkyl functions and methacryloxypropyltrimethoxysilane (MPTMS) through a sol-gel process. The influence of concentration and fluoro-alkyl chain lengths of FASs on the physical characteristics of the fluorinated HYBRIMER films was examined. Larger fluorine contents lowered the refractive index within a range, which was closely dependent on the fluoro-alkyl chain lengths of FASs. Thermo-optic coefficients (TOC) were negative values, and the values grew with increasing fluorine contents and fluoro-alkyl chain lengths. Also, the thermal stability is enhanced by addition of fluorine in the HYBRIMER. 相似文献
10.
We study condensation of ethanol-hexanol vapour by numerical solution of kinetic equations. The number of droplets formed
in unit volume is computed within self-consistent classical model. It is shown that formation of ethanol-rich droplets prevails
at the initial stage of nucleation process, but in the stationary state formation of droplets near the saddle point (on cluster
formation energy surface) plays the dominant role.
Presented at the 6th Joint Seminar “Development of Materials Science in Research and Education”, Karlštejn, Czech Republic,
17–19 September 1996.
This work was supported by Grant No. A1010615 of the Grant Agency of the Academy of Sciences of the Czech Republic. 相似文献