全文获取类型
收费全文 | 5334篇 |
免费 | 207篇 |
国内免费 | 19篇 |
专业分类
化学 | 4307篇 |
晶体学 | 40篇 |
力学 | 45篇 |
数学 | 208篇 |
物理学 | 960篇 |
出版年
2023年 | 33篇 |
2021年 | 54篇 |
2020年 | 85篇 |
2019年 | 83篇 |
2018年 | 36篇 |
2017年 | 36篇 |
2016年 | 110篇 |
2015年 | 109篇 |
2014年 | 123篇 |
2013年 | 233篇 |
2012年 | 320篇 |
2011年 | 368篇 |
2010年 | 193篇 |
2009年 | 181篇 |
2008年 | 357篇 |
2007年 | 353篇 |
2006年 | 335篇 |
2005年 | 344篇 |
2004年 | 319篇 |
2003年 | 262篇 |
2002年 | 232篇 |
2001年 | 116篇 |
2000年 | 79篇 |
1999年 | 78篇 |
1998年 | 39篇 |
1997年 | 61篇 |
1996年 | 40篇 |
1995年 | 41篇 |
1994年 | 41篇 |
1993年 | 38篇 |
1992年 | 54篇 |
1991年 | 44篇 |
1990年 | 43篇 |
1989年 | 41篇 |
1988年 | 26篇 |
1987年 | 43篇 |
1986年 | 20篇 |
1985年 | 57篇 |
1984年 | 52篇 |
1983年 | 27篇 |
1982年 | 46篇 |
1981年 | 51篇 |
1980年 | 39篇 |
1979年 | 51篇 |
1978年 | 28篇 |
1977年 | 31篇 |
1976年 | 25篇 |
1975年 | 22篇 |
1974年 | 24篇 |
1973年 | 20篇 |
排序方式: 共有5560条查询结果,搜索用时 15 毫秒
81.
Tohru TakeiTakumi Ohki Yosuke HaradaNaoto Kumagai Hiroki FukumotoTake-aki Koizumi Akihiro MaedaTakahiro Kojima Yoshihisa SeiKohei Shiramizu Masahiro AbeMasashi Oota Takakazu Yamamoto 《Tetrahedron letters》2012,53(44):5907-5910
Dibromopyridines or dibromopyridone with -(CH2)m-SO3Na group(s) has been prepared via the reactions of the corresponding dibromopyridines with -OH and -NH2 groups with sultone. These compounds were converted into polymers with the -(CH2)m-SO3H groups via organometallic polycondensation. The polymer showed proton conducting properties and high stability toward oxidation. 相似文献
82.
Nobuhiro ShionozakiToru Yamaguchi Hiroyuki KitanoMitsutaka Tomizawa Kimiko Makino Hiromi Uchiro 《Tetrahedron letters》2012,53(38):5167-5170
Total synthesis of an antitumor compound myceliothermophin A and related compounds based on a convergent synthetic strategy was investigated. A common decalin skeleton of myceliothermophins was stereoselectively constructed by an IMDA reaction. The fully elaborated precursor of myceliothermophins was obtained via aldol reaction of N-protected γ-methoxylactam with decalin aldehyde. By using Teoc group for the protection of nitrogen atom of lactam ring, selective deprotection prior to the hydrolysis of methoxyaminal moiety was successfully achieved to obtain γ-methoxylactams (myceliothermophins C and D). Subsequent hydrolysis of these compounds afforded the corresponding γ-hydroxylactam, and myceliothermophins A and B in high yield. Myceliothermophin E was also synthesized by dehydration of the obtained γ-hydroxylactams. The absolute configurations of myceliothermophins A-E were also successfully determined. 相似文献
83.
84.
85.
Kenji Kinashi Yuki Kambe Masahiro Misaki Yasuko Koshiba Kenji Ishida Yasukiyo Ueda 《Journal of polymer science. Part A, Polymer chemistry》2012,50(24):5107-5114
Three types of bi‐functionalized copolymers ( P1FAz , P2FAz , and P3FAz ) with different numbers of fluorene units and an azobenzene unit were synthesized and characterized using UV–vis and polarized absorption spectroanalysis. The trans‐cis photoisomerization was conformed under 400 nm light irradiation for all copolymers in chloroform. However, in the film state, only the trans‐cis photoisomerization occurred by mono‐fluorene attached copolymer poly[(9,9‐di‐n‐octylfluorenyl‐2,7‐diyl)‐alt‐4,4′‐azobenzene)] ( P1FAz ). Photo‐induced alignment was achieved using the P1FAz film after irradiation with linear polarized 400 nm light and subsequent annealing at 60 °C. Surface orientation of a spin‐coating film of poly(9,9‐didodecylfluorene) ( F12 ) was achieved using the photo‐induced alignment layer of the P1FAz film after annealing at 90 °C. The photo‐induced alignment layer of P1FAz has potential application to the surface orientation technique for appropriate polymers, which will be useful for the fabrication of optoelectronics devices. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
86.
Seiichi Ohta Susumu Inasawa Yukio Yamaguchi 《Journal of Polymer Science.Polymer Physics》2012,50(12):863-869
When a mixture of liquid crystal (LC) and photo reactive monomer is irradiated by UV light, polymerization occurs and LC droplets form through phase separation, producing polymer dispersed LCs (PDLCs). Although size control of LC droplets and reduced amounts of LC in PDLC films are important in applications, precise size control of LC droplets at a low LC fraction has not yet been accomplished. In this study, the phase diagrams of the LC/initial monomer and the LC/polymer during polymerization were used to control LC droplet size at various LC fractions. Both the relative position of the sample in the initial phase diagram and the shift of the phase separation line during polymerization were shown to be important in determining the size of LC droplets. Our results are expected to provide a new strategy for precise size control of LC droplets especially at a low LC fraction range, which would be a great help for PDLC applications. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012 相似文献
87.
Annealing polyethylene terephthalate (PET)/polycarbonate (PC) blends enhance the transesterification reaction and increase the amount of copolymer at the interface of both polymers. The copolymer enhances the compatibility of PET with PC, because it contains both PET and PC blocks, which causes the interface between PET and PC to become fuzzy. When the PET/PC undergoes batch physical foaming with CO2, the copolymer significantly changes the resulting cell morphology, that is, the annealing time. Before annealing or in the absence of the copolymer, bubble nucleation occurs and dominates growth at the interface. When the PET/PC blends are annealed, the interface impedes bubble nucleation and growth. The polymer is stretched at the interface by bubble growth, forming fibril‐like structures connecting two polymer domains at the interface. Increased annealing time causes the interface to become more homogeneous and makes heterogeneous bubble nucleation difficult. At higher copolymer concentrations, the interface of PET and PC becomes fuzzy and the cell morphology becomes like those of foamed homogeneous polymers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012 相似文献
88.
89.
90.