全文获取类型
收费全文 | 3934篇 |
免费 | 165篇 |
国内免费 | 2篇 |
专业分类
化学 | 2630篇 |
晶体学 | 9篇 |
力学 | 98篇 |
数学 | 556篇 |
物理学 | 808篇 |
出版年
2023年 | 28篇 |
2022年 | 18篇 |
2021年 | 30篇 |
2020年 | 51篇 |
2019年 | 34篇 |
2018年 | 67篇 |
2017年 | 36篇 |
2016年 | 93篇 |
2015年 | 101篇 |
2014年 | 107篇 |
2013年 | 200篇 |
2012年 | 276篇 |
2011年 | 289篇 |
2010年 | 145篇 |
2009年 | 124篇 |
2008年 | 198篇 |
2007年 | 228篇 |
2006年 | 193篇 |
2005年 | 178篇 |
2004年 | 154篇 |
2003年 | 117篇 |
2002年 | 117篇 |
2001年 | 61篇 |
2000年 | 32篇 |
1999年 | 25篇 |
1998年 | 23篇 |
1997年 | 23篇 |
1996年 | 20篇 |
1995年 | 20篇 |
1994年 | 20篇 |
1993年 | 19篇 |
1988年 | 16篇 |
1983年 | 18篇 |
1982年 | 16篇 |
1981年 | 23篇 |
1980年 | 15篇 |
1977年 | 15篇 |
1937年 | 20篇 |
1936年 | 16篇 |
1935年 | 17篇 |
1934年 | 26篇 |
1933年 | 24篇 |
1932年 | 29篇 |
1931年 | 18篇 |
1930年 | 24篇 |
1929年 | 24篇 |
1928年 | 20篇 |
1927年 | 28篇 |
1926年 | 15篇 |
1924年 | 20篇 |
排序方式: 共有4101条查询结果,搜索用时 15 毫秒
1.
Dr. Aurélien Blanc Dr. Pierre de Frémont 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(41):9553-9567
Merging gold(I) cations with polyoxometalate anions results in various interclusters and complexes. Herein, the synthesis of these newly emerging gold(I)/polyoxometalate materials is reviewed. The applications of these promising hybrids in organic catalysis are also summarized and evaluated in terms of the advantages and limitations of the catalysts including efficiency, synergistic effects and recyclability. 相似文献
2.
Mariem Ghali Chaima Brahmi Mahmoud Benltifa Cyril Vaulot Aissam Airoudj Philippe Fioux Frédéric Dumur Corine Simonnet-Jégat Fabrice Morlet-Savary Salah Jellali Latifa Bousselmi Jacques Lalevée 《Journal of polymer science. Part A, Polymer chemistry》2021,59(2):153-169
Different inorganic/organic photocomposites based on polyoxometalate (POM) nanoparticles have been developed for photocatalytic applications. Currently, polyoxometalate nanoparticles have been successfully in-situ embedded into an acrylate polymer network by photopolymerization upon mild visible light irradiation at 405 nm. The proposed POM/polymer photocomposites have been characterized using complementary techniques for a better understanding of their photocatalytic activity. Interestingly, the obtained photocomposites exhibit high rigidity, excellent thermal stability, a non-negligible porosity and new functionalities such as light reactivity and redox properties. Moreover, developed composites showed efficient catalytic activity for the color removal of aqueous solutions of erythrosine and rose Bengal under Light Emitting Diodes LED@375 nm irradiation reaching 80 and 90% as a final color removal, respectively. 相似文献
3.
4.
Naphthalic anhydride derivatives: Structural effects on their initiating abilities in radical and/or cationic photopolymerizations under visible light 下载免费PDF全文
Pu Xiao Frédéric Dumur Jing Zhang Bernadette Graff Fabrice Morlet‐Savary Jean Pierre Fouassier Didier Gigmes Jacques Lalevée 《Journal of polymer science. Part A, Polymer chemistry》2015,53(24):2860-2866
Only one naphthalic anhydride derivative has been reported as light sensitive photoinitiator, this prompted us to further explore the possibility to prepare a new family of photoinitiators based on this scaffold. Therefore, eight naphthalic Naphthalic anhydride derivatives (ANH1‐ANH8) have been prepared and combined with an iodonium salt (and optionally N‐vinylcarbazole) or an amine (and optionally 2,4,6‐tris(trichloromethyl)‐1,3,5‐triazine) to initiate the cationic polymerization of epoxides and the free radical polymerization of acrylates under different irradiation sources, that is, very soft halogen lamp (~ 12 mW cm?2), laser diode at 405 nm (~1.5 mW cm?2) or blue LED centered at 455 nm (80 mW cm?2). The ANH6 based photoinitiating systems are particularly efficient for the cationic and the radical photopolymerizations, and even better than that of the well‐known camphorquinone based systems. The photochemical mechanisms associated with the chemical structure/photopolymerization efficiency relationships are studied by steady state photolysis, fluorescence, cyclic voltammetry, laser flash photolysis, and electron spin resonance spin‐trapping techniques. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2860–2866 相似文献
5.
“(Diphosphine)Nickel”‐Catalyzed Negishi Cross‐Coupling: An Experimental and Theoretical Study 下载免费PDF全文
Dr. Emmanuel Nicolas Alexia Ohleier Florian D'Accriscio Dr. Anne‐Frédérique Pécharman Dr. Matthieu Demange Dr. Philippe Ribagnac Dr. Jorge Ballester Dr. Corinne Gosmini Dr. Nicolas Mézailles 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(21):7690-7694
The use of a strongly donating “(bis‐dialkylphosphine)Ni” fragment promotes the catalytic coupling of a large range of ArCl and ArZnCl derivatives under mild conditions. Stoichiometric mechanistic investigations and DFT calculations prove that a Ni0/NiII cycle is operative in this system. 相似文献
6.
Structure/reactivity/photoinitiation ability relationships in novel benzo pyrazolo (or imidazo) isoquinolinone derivatives upon visible light LEDs 下载免费PDF全文
Pu Xiao Frédéric Dumur Jing Zhang Mariem Bouzrati‐Zerelli Bernadette Graff Didier Gigmes Jacques Lalevée 《Journal of polymer science. Part A, Polymer chemistry》2015,53(15):1806-1815
Isoquinolinone derivatives bearing amino‐ or nitro‐ substituent (IQNs) have been synthesized as photoinitiators and combined with various additives (i.e., iodonium salt, N‐vinylcarbazole, amine or 2,4,6‐tris(trichloromethyl)?1,3,5‐triazine) to initiate ring‐opening cationic polymerizations (CP) or free radical polymerizations under exposure to visible LEDs (e.g., LEDs at 405 nm or 455 nm, or cold white LED) or a halogen lamp. Compared to the well‐known camphorquinone‐based systems, the novel IQNs‐based combinations employed here demonstrate higher efficiencies for the CP of epoxides. The photochemically generated reactive species (i.e., cations and radicals) from the IQNs‐based systems have been investigated by steady state photolysis, cyclic voltammetry, fluorescence, laser flash photolysis, and electron spin resonance spin trapping techniques. The structure/reactivity/photoinitiating ability relationships of IQNs‐based combinations are also discussed; the crucial role of the excited state lifetimes of the photoinitiators to ensure efficient quenching by additives is clearly underlined. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1806–1815 相似文献
7.
Pauline L. Nasatto Frédéric Pignon Joana L. M. Silveira Maria Eugênia R. Duarte Miguel D. Noseda Marguerite Rinaudo 《International Journal of Polymer Analysis and Characterization》2015,20(2):110-118
In this study, thermogelation of methylcelluloses is investigated in relation to the molar mass and concentration in aqueous medium. A large hysteresis between heating and cooling ramps was observed whatever the conditions. The heating process in particular was studied to analyze the two steps of gelation using rheometry. At low temperature, in the sol state, viscosity depends on the concentration and molar mass. Over 30°C a gel-like behavior was observed including two steps (the second step is a strong gel with phase separation) having storage moduli that are nearly independent of polymer molar mass but are directly related to polymer concentration. 相似文献
8.
9.
10.
Agata Kozioł Jakub Frątczak Ewa Grela Maryla Szczepanik Beata Gabryś Katarzyna Dancewicz 《Natural product research》2020,34(10):1399-1403
AbstractTerpenoid derivatives, which contain a preserved carane system in their structure, exhibit a broad spectrum of biological activities. Among them, we can distinguish insecticides, structures with pharmacological application etc. In the presented paper, the substrate - (–)-cis-caran-trans-4-ol was transformed using the reactions of typical organic synthesis to obtain novel derivatives. Most importantly, bromolactone ((–)-(1R,4R,6S)-2'-(bromomethyl)-4,7,7-trimethylspiro[bicyclo[4.1.0]heptan-3,3'-furan]-5'(4'H)-one) with the preserved carane system was synthesized. This bromolactone was tested for antifeedant activity against the lesser mealworm, Alphitobius diaperinus Panzer, and peach potato aphid (Myzus persicae). In addition, its moderate antibacterial activity was observed against the Bacillus subtilis strain (with Minimal Inhibitory Concentration of 200 µg/mL). 相似文献