全文获取类型
收费全文 | 1439篇 |
免费 | 74篇 |
国内免费 | 274篇 |
专业分类
化学 | 1248篇 |
晶体学 | 8篇 |
力学 | 72篇 |
综合类 | 1篇 |
数学 | 179篇 |
物理学 | 279篇 |
出版年
2023年 | 9篇 |
2022年 | 19篇 |
2021年 | 29篇 |
2020年 | 24篇 |
2019年 | 19篇 |
2018年 | 34篇 |
2017年 | 25篇 |
2016年 | 29篇 |
2015年 | 30篇 |
2014年 | 46篇 |
2013年 | 134篇 |
2012年 | 114篇 |
2011年 | 122篇 |
2010年 | 71篇 |
2009年 | 97篇 |
2008年 | 81篇 |
2007年 | 80篇 |
2006年 | 55篇 |
2005年 | 76篇 |
2004年 | 145篇 |
2003年 | 120篇 |
2002年 | 90篇 |
2001年 | 29篇 |
2000年 | 26篇 |
1999年 | 27篇 |
1998年 | 26篇 |
1997年 | 24篇 |
1996年 | 21篇 |
1995年 | 11篇 |
1994年 | 7篇 |
1993年 | 16篇 |
1992年 | 10篇 |
1990年 | 7篇 |
1989年 | 9篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1984年 | 9篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 4篇 |
1972年 | 6篇 |
1967年 | 4篇 |
1958年 | 4篇 |
1929年 | 4篇 |
排序方式: 共有1787条查询结果,搜索用时 15 毫秒
161.
162.
Vincent Besse Loïc Le Pluart Wayne D. Cook Thi‐Nhàn Pham Pierre‐Jean Madec 《Journal of polymer science. Part A, Polymer chemistry》2013,51(23):5046-5055
Phosphonic acids are known to be useful monomers in dental restorative materials because of their good potential to provide enhanced adhesion to hydroxyapatite and their high hydrolytic stability. In this study, the photopolymerization of phosphonic acid‐based monomer via the camphorquinone (CQ)/ethyl‐4‐(dimethylaminobenzoate) (EDAB) photoredox system is compared with a ternary system composed of iodonium hexafluorophosphate and CQ/EDAB. Photocalorimetry shows that the ternary system does not provide a significant acceleration of the polymerization with either acrylamide or methacrylate phosphonic acids. The complexation of the iodonium by the phosphonic moiety of the acidic monomers leads to a lowered iodonium reactivity and reduced polarizability of the medium and as a consequence limits the rate enhancement effect normally observed by phosphonic acids on the polymerization rate. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5046–5055 相似文献
163.
164.
A new reagent for spectrophotometric determination of Mo(VI) was developed utilizing micellar effects. For this purpose, differences
in the ultraviolet and visible spectral properties of Mo(VI), gallic acid, L-serine, and their binary and ternary solutions were studied in the presence and absence of cationic, anionic, and non-ionic
surface active agents. L-serine was observed to form binary complexes and a ternary complex with Mo(VI) and gallic acid below its isoelectric point.
The maximum Mo(VI) sensitivity was exerted by the Mo(VI) + gallic acid + L-serine + hexadecyltrimethylammonium bromide system at pH of 4.5. This system was proposed for use in the spectrophotometric
determination of Mo(VI) as a superior alternative to the Mo(VI) + gallic acid + hexadecyltrimethylammonium bromide system
and to most of the instrumental analysis methods referred to in the literature. The mechanism of micellar effects was discussed
on the basis of the spectral data obtained above and below the isoelectric point of L-serine and explained in terms of the molecular charge of the substrates and the surfactants. 相似文献
165.
166.
167.
168.
Sakihito Kitajima Kaeko Kamei Shigeru Taketani Masamitsu Yamaguchi Fumiko Kawai Aino Komatsu Yoshihiro Inukai 《BMC biochemistry》2010,11(1):6
Background
Plant latex is the cytoplasm of highly specialized cells known as laticifers, and is thought to have a critical role in defense against herbivorous insects. Proteins abundantly accumulated in latex might therefore be involved in the defense system. 相似文献169.
Mudasir Ahmad Tantry Reehana Khan Seema Akbar Abdul Rouf Dar Abdul Sami Shawl Mohammad Sarwar Alam 《中国化学快报》2011,22(5):575-579
An unusual oleanane triterpene(1) was isolated from aerial parts of Rhododendron campanulatum.The compound had shown prominent antibacterial and immunomodulatory activities.The structure of the compound was determined by spectroscopic data including 1D and 2D NMR spectral analysis. 相似文献
170.
Katsuhiko Takenaka Natsuyo Shibata Akihiko Oshikiri Masamitsu Miya Hiroki Takeshita Tomoo Shiomi 《Journal of polymer science. Part A, Polymer chemistry》2010,48(17):3714-3721
Anionic polymerizations of three 1,3‐butadiene derivatives containing different N,N‐dialkyl amide functions, N,N‐diisopropylamide (DiPA), piperidineamide (PiA), and cis‐2,6‐dimethylpiperidineamide (DMPA) were performed under various conditions, and their polymerization behavior was compared with that of N,N‐diethylamide analogue (DEA), which was previously reported. When polymerization of DiPA was performed at ?78 °C with potassium counter ion, only trace amounts of oligomers were formed, whereas polymers with a narrow molecular weight distribution were obtained in moderate yield when DiPA was polymerized at 0 °C in the presence of LiCl. Decrease in molecular weight and broadening of molecular weight distribution were observed when polymerization was performed at a higher temperature of 20 °C, presumably because of the effect of ceiling temperature. In the case of DMPA, no polymer was formed at 0 °C and polymers with relatively broad molecular weight distributions (Mw/Mn = 1.2) were obtained at 20 °C. The polymerization rate of PiA was much faster than that of the other monomers, and poly(PiA) was obtained in high yield even at ?78 °C in 24 h. The microstructure of the resulting polymers were exclusively 1,4‐ for poly(DMPA), whereas 20–30% of the 1,2‐structure was contained in poly(DiPA) and poly(PiA). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3714–3721, 2010 相似文献