全文获取类型
收费全文 | 22755篇 |
免费 | 925篇 |
国内免费 | 86篇 |
专业分类
化学 | 14888篇 |
晶体学 | 114篇 |
力学 | 640篇 |
综合类 | 2篇 |
数学 | 3451篇 |
物理学 | 4671篇 |
出版年
2021年 | 185篇 |
2020年 | 241篇 |
2019年 | 274篇 |
2018年 | 228篇 |
2017年 | 182篇 |
2016年 | 500篇 |
2015年 | 519篇 |
2014年 | 535篇 |
2013年 | 933篇 |
2012年 | 984篇 |
2011年 | 1124篇 |
2010年 | 783篇 |
2009年 | 708篇 |
2008年 | 1047篇 |
2007年 | 985篇 |
2006年 | 1023篇 |
2005年 | 924篇 |
2004年 | 882篇 |
2003年 | 758篇 |
2002年 | 817篇 |
2001年 | 502篇 |
2000年 | 438篇 |
1999年 | 287篇 |
1998年 | 279篇 |
1997年 | 277篇 |
1996年 | 336篇 |
1995年 | 301篇 |
1994年 | 325篇 |
1993年 | 317篇 |
1992年 | 344篇 |
1991年 | 270篇 |
1990年 | 247篇 |
1989年 | 210篇 |
1988年 | 233篇 |
1987年 | 223篇 |
1986年 | 212篇 |
1985年 | 270篇 |
1984年 | 282篇 |
1983年 | 227篇 |
1982年 | 287篇 |
1981年 | 246篇 |
1980年 | 265篇 |
1979年 | 256篇 |
1978年 | 263篇 |
1977年 | 248篇 |
1976年 | 242篇 |
1975年 | 208篇 |
1974年 | 217篇 |
1973年 | 197篇 |
1972年 | 102篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
The growth-fragmentation equation describes a system of growing and dividing particles, and arises in models of cell division, protein polymerisation and even telecommunications protocols. Several important questions about the equation concern the asymptotic behaviour of solutions at large times: at what rate do they converge to zero or infinity, and what does the asymptotic profile of the solutions look like? Does the rescaled solution converge to its asymptotic profile at an exponential speed? These questions have traditionally been studied using analytic techniques such as entropy methods or splitting of operators. In this work, we present a probabilistic approach: we use a Feynman–Kac formula to relate the solution of the growth-fragmentation equation to the semigroup of a Markov process, and characterise the rate of decay or growth in terms of this process. We then identify the Malthus exponent and the asymptotic profile in terms of a related Markov process, and give a spectral interpretation in terms of the growth-fragmentation operator and its dual. 相似文献
4.
5.
6.
7.
8.
Claudia Poloni Marc C. A. Stuart Pieter van der Meulen Wiktor Szymanski Ben L. Feringa 《Chemical science》2015,6(12):7311-7318
The external photocontrol over peptide folding, by the incorporation of molecular photoswitches into their structure, provides a powerful tool to study biological processes. However, it is limited so far to switches that exhibit only a rather limited geometrical change upon photoisomerization and that show thermal instability of the photoisomer. Here we describe the use of an overcrowded alkene photoswitch to control a model β-hairpin peptide. This photoresponsive unit undergoes a large conformational change and has two thermally stable isomers which has major influence on the secondary structure and the aggregation of the peptide, permitting the phototriggered formation of amyloid-like fibrils. 相似文献
9.
Photoisomerisation in Aminoazobenzene‐Substituted Ruthenium(II) Tris(bipyridine) Complexes: Influence of the Conjugation Pathway
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Anissa Amar Dr. Paul Savel Dr. Huriye Akdas‐Kilig Dr. Claudine Katan Prof. Hacène Meghezzi Prof. Abdou Boucekkine Dr. Jean‐Pierre Malval Dr. Jean‐Luc Fillaut 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(22):8262-8270
Transition‐metal complexes containing stimuli‐responsive systems are attractive for applications in optical devices, photonic memory, photosensing, as well as luminescence imaging. Amongst them, photochromic metal complexes offer the possibility of combining the specific properties of the metal centre and the optical response of the photochromic group. The synthesis, the electrochemical properties and the photophysical characterisation of a series of donor–acceptor azobenzene derivatives that possess bipyridine groups connected to a 4‐dialkylaminoazobenzene moiety through various linkers are presented. DFT and TD‐DFT calculations were performed to complement the experimental findings and contribute to their interpretation. The position and nature of the linker (ethynyl, triazolyl, none) were engineered and shown to induce different electronic coupling between donor and acceptor in ligands and complexes. This in turn led to strong modulations in terms of photoisomerisation of the ligands and complexes. 相似文献
10.
Naphthalimide‐phthalimide derivative based photoinitiating systems for polymerization reactions under blue lights
下载免费PDF全文
![点击此处可从《Journal of polymer science. Part A, Polymer chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Pu Xiao Frédéric Dumur Jing Zhang Bernadette Graff Didier Gigmes Jean Pierre Fouassier Jacques Lalevée 《Journal of polymer science. Part A, Polymer chemistry》2015,53(5):665-674
Naphthalimide‐phthalimide derivatives (NDPDs) have been synthesized and combined with an iodonium salt, N‐vinylcarbazole, amine or 2,4,6‐tris(trichloromethyl)‐1,3,5‐triazine to produce reactive species (i.e., radicals and cations). These generated reactive species are capable of initiating the cationic polymerization of epoxides and/or the radical polymerization of acrylates upon exposure to very soft polychromatic visible lights or blue lights. Compared with the well‐known camphorquinone based systems used as references, the novel NDPD based combinations employed here demonstrate clearly higher efficiencies for the cationic polymerization of epoxides under air as well as the radical polymerization of acrylates. Remarkably, one of the NDPDs (i.e., NDPD2) based systems is characterized by an outstanding reactivity. The structure/reactivity/efficiency relationships of the investigated NDPDs were studied by fluorescence, cyclic voltammetry, laser flash photolysis, electron spin resonance spin trapping, and steady state photolysis techniques. The key parameters for their reactivity are provided. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 665–674 相似文献