全文获取类型
收费全文 | 2013篇 |
免费 | 81篇 |
国内免费 | 4篇 |
学科分类
数理化 | 2098篇 |
出版年
2023年 | 15篇 |
2022年 | 9篇 |
2021年 | 38篇 |
2020年 | 44篇 |
2019年 | 53篇 |
2018年 | 22篇 |
2017年 | 31篇 |
2016年 | 68篇 |
2015年 | 57篇 |
2014年 | 56篇 |
2013年 | 130篇 |
2012年 | 130篇 |
2011年 | 153篇 |
2010年 | 109篇 |
2009年 | 87篇 |
2008年 | 148篇 |
2007年 | 141篇 |
2006年 | 131篇 |
2005年 | 109篇 |
2004年 | 115篇 |
2003年 | 72篇 |
2002年 | 60篇 |
2001年 | 20篇 |
2000年 | 20篇 |
1999年 | 10篇 |
1998年 | 17篇 |
1997年 | 11篇 |
1996年 | 14篇 |
1995年 | 12篇 |
1994年 | 6篇 |
1993年 | 14篇 |
1992年 | 17篇 |
1991年 | 9篇 |
1990年 | 7篇 |
1989年 | 9篇 |
1988年 | 11篇 |
1986年 | 10篇 |
1985年 | 15篇 |
1984年 | 15篇 |
1983年 | 13篇 |
1982年 | 9篇 |
1981年 | 8篇 |
1980年 | 11篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 4篇 |
1972年 | 5篇 |
排序方式: 共有2098条查询结果,搜索用时 15 毫秒
1.
Peralta Cecilia Mariana Acosta Gimena Henestrosa Cecilia Gil Raúl Andrés Fernández Liliana Patricia 《Journal of Analytical Chemistry》2022,77(3):308-317
Journal of Analytical Chemistry - The present development involved a flow injection strategy using a mini-column of multiwalled carbon nanotubes and fluorescent detection (λex of 283 nm,... 相似文献
2.
End group polarity and block symmetry effects on cloud point and hydrodynamic diameter of thermoresponsive block copolymers 下载免费PDF全文
Xu Xiang Xiaochu Ding Ning Chen Beilu Zhang Patricia A. Heiden 《Journal of polymer science. Part A, Polymer chemistry》2015,53(24):2838-2848
Thermoresponsive block copolymers are of interest for delivery vehicles in the body. Often an interior domain is designed for the active agent and the exterior domain provides stability in the bloodstream, and may carry a targeting ligand. There is still much to learn about how block sequence and chain end identity affect micelle structure, size, and cloud points. Here, hydrophilic oligo(ethylene glycol) methyl ether acrylate and more hydrophobic di(ethylene glycol) methyl ether methacrylate monomers were polymerized to give amphiphilic block copolymers with amphiphilic chain ends. The block sequence and chain end identity were both controlled by appropriate choice of RAFT chain transfer agents to study the effect of ‘matched’ and ‘mismatched’ chain end polarity with amphiphilic block sequence. The affect of matching or mismatching chain end polarity and block sequence was studied on the hydrodynamic diameter, cloud point, and temperature range of the chain collapse on linear di‐ and triblock copolymers and star diblock polymers. The affects of matching or mismatching chain end polarity were significant with linear diblock copolymers but more complex with triblock and star copolymers. Explanations of these results may help guide others in designing thermoresponsive block copolymers. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2838–2848 相似文献
3.
4.
5.
Dr. Beatriz Feringán Jesús Cerdá Dr. Beatriz Diosdado Dr. Juan Aragó Prof. Dr. Enrique Ortí Dr. Raquel Giménez Dr. Teresa Sierra 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(66):15313-15322
The ability of a star-shaped tris(triazolyl)triazine derivative to hierarchically build supramolecular chiral columnar organizations through the formation of H-bonded complexes with benzoic acids was studied from a theoretical and experimental point of view. The combined study has been done at three different levels including the study of the structure of the triazine core, the association with benzoic acids in stoichiometry 1:3, and the assembly of 1:3 complexes in helical aggregates. Although the star-shaped triazine core crystallizes in a non-C3 conformation, the C3-symmetric conformation is theoretically predicted to be more stable and gives rise to a favorable C3 supramolecular 1:3 complex upon the interaction with three benzoic acids in their voids. In addition, calculations at different levels (DFT, PM7, and MM3) for the 1:3 host-guest complex predict the formation of large stable columnar helical aggregates stabilized by the compact packing of the interstitial acids by π–π and CH⋅⋅⋅π interactions. The acids restrict the movement of the the star-shaped triazine cores along the stacking axis causing a template effect in the self-assembly of the complex. Theoretical predictions correlate with experimental results, since the interaction with achiral or chiral 3,4,5-(4-alkoxybenzyloxy)benzoic acids gives rise to supramolecular complexes that organize in bulk hexagonal columnar mesophases stable at room temperature with intracolumnar order. The existence of supramolecular chirality in the mesophase was determined for complexes formed by acids derived from (S)-2-octanol. Chiral aggregation was also evidenced for complexes formed in dodecane. 相似文献
6.
Carvalho Patricia R. Munita Casimiro S. Neves Eduardo G. Zimpel Carlos A. 《Journal of Radioanalytical and Nuclear Chemistry》2020,324(3):1053-1058
Journal of Radioanalytical and Nuclear Chemistry - This research aims to contribute to the discussion of ceramic objects found at the Monte Castelo shellmound, an archaeological site located at... 相似文献
7.
8.
9.
Prof. Dr. Javier A. Cabeza Dr. Pablo García-Álvarez Prof. Dr. Mar Gómez-Gallego Laura González-Álvarez Alba D. Merinero Prof. Dr. Miguel A. Sierra 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(36):8635-8642
The reactivity of amidinatotetrylenes of the type E(tBu2bzm)R1 (E=Si, Ge; tBu2bzm=N,N′-bis(tertbutyl)benzamidinate; R1=alkyl or aryl) with the chromium Fischer alkynylcarbene complexes [Cr{C(OEt)C2R2}(CO)5] (R2=Ph; ferrocenyl, Fc) has been studied. At room temperature, two different reaction pathways have been identified: (a) attack of the amidinatotetrylene to the alkynyl C2 atom (γ-attack), which leads to σ-allenyl complexes in which the original Ccarbene atom maintains its attachment to the Cr(CO)5 and OEt groups (compounds 3 ), and (b) attack of the amidinatotetrylene to the Ccarbene atom (α-attack), which ends in σ-allenyl complexes in which the original Ccarbene atom is not attached to the metal atom and has been inserted into an E−N bond of the amidinatotetrylene forming an E-C-N-C-N five-membered ring (compounds 4 ). It has been found that compounds 3 are thermodynamically less stable than their corresponding 4 isomers and that some of the former (E=Ge; R1=CH2SiMe3) can be transformed into the latter upon heating. At high temperatures (>70 °C) the reactions involving bulky amidinatotetrylenes (R1=Mes, tBu) end in the carbene-substitution products [Cr{E(tBu2bzm)R1}(CO)5]. 相似文献
10.