全文获取类型
收费全文 | 576篇 |
免费 | 29篇 |
国内免费 | 1篇 |
专业分类
化学 | 541篇 |
晶体学 | 3篇 |
数学 | 7篇 |
物理学 | 55篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 8篇 |
2020年 | 2篇 |
2019年 | 14篇 |
2018年 | 5篇 |
2017年 | 12篇 |
2016年 | 10篇 |
2015年 | 14篇 |
2014年 | 24篇 |
2013年 | 33篇 |
2012年 | 38篇 |
2011年 | 36篇 |
2010年 | 23篇 |
2009年 | 24篇 |
2008年 | 33篇 |
2007年 | 37篇 |
2006年 | 46篇 |
2005年 | 33篇 |
2004年 | 39篇 |
2003年 | 48篇 |
2002年 | 38篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有606条查询结果,搜索用时 265 毫秒
81.
Enantioselective synthesis of phomallenic acid C, an inhibitor of bacterial FAS II pathway, was successful. Allenyldiyne structure was constructed by a direct anti-SN2′ coupling of propargyl mesylate with diynylindium in the presence of palladium catalyst. Enantiomeric purity was determined by Ohrui-Akasaka method to be 83%ee. 相似文献
82.
Dr. Soichiro Ogi Aiko Takamatsu Kentaro Matsumoto Shintaro Hasegawa Prof. Dr. Shigehiro Yamaguchi 《Angewandte Chemie (International ed. in English)》2023,62(34):e202306428
We have investigated the folding and assembly behavior of a cystine-based dimeric diamide bearing pyrene units and solubilizing alkyl chains. In low-polarity solvents, it forms a 14-membered ring through double intramolecular hydrogen bonds between two diamide units. The spectroscopic studies revealed that the folded state is thermodynamically unstable and eventually transforms into more energetically stable helical supramolecular polymers that show an enhanced chiral excitonic coupling between the transition dipoles of the pyrene units. Importantly, compared to an alanine-based monomeric diamide, the dimeric diamide exhibits a superior kinetic stability in the metastable folded state, as well as an increased thermodynamic stability in the aggregated state. Accordingly, the initiation of supramolecular polymerization can be regulated using a seeding method even under microfluidic mixing conditions. Furthermore, taking advantage of a self-sorting behavior observed in a mixture of l -cysteine- and d -cysteine-based dimeric diamides, a two-step supramolecular polymerization was achieved by stepwise addition of the corresponding seeds. 相似文献
83.
We prepared reversible micelles with dye loaded on the shells or cores by ion exchange. A poly(4-styrylmethyl triphenylphosphonium
chloride)-block-polystyrene diblock copolymer prepared from poly(4-vinylbenzylchloride)-block-polystyrene and triphenylphosphine
was reacted with methyl orange in a mixed solvent of benzene and acetonitrile to produce poly[4-styrylmethyl triphenylphosphonium
4-(4-dimethylamino)phenylazobenzenesulfonate]-block-polystyrene. The loading of the methyl orange on the micellar shells or
cores was dependent on the composition of the mixed solvents. Dynamic light scattering demonstrated that the loading of the
dye on the cores significantly expanded the micelles when compared to that on the shells. The loading of the dye on the cores
shifted the UV wavelength of the methyl orange, whereas that on the shells produced no changes in the UV wavelength. Transmission
electron microscopy confirmed the formation of the spherical micelles. 相似文献
84.
Okada T Sano M Yamamoto Y Muramatsu H 《Langmuir : the ACS journal of surfaces and colloids》2008,24(8):4050-4055
We evaluated the binding affinity of peptide probes for profilin (protein) using force curve measurement techniques and atomic force microscopy (AFM). The peptide probes designed and synthesized for this investigation were H-A3GP5GP5GP5G-OH (1), H-A3GP5G-OH (2), H-A3G7-OH (3), and H-A3G-OH (4). Each peptide probe was immobilized on a cantilever tip, and the interaction force to profilin, immobilized on a mica substrate, was examined by force curve measurements. The retraction forces obtained showed a sequence-dependent affinity of the peptide probe for profilin. The retraction force for peptide probe 1 was the largest of the four probes examined, and it confirmed that peptide probe 1 has high affinity for profilin. The single molecular retraction force between peptide probe 1 and profilin was estimated to be 96 pN, as determined by Gaussian fitting to the histogram of the retraction forces. 相似文献
85.
86.
Tomoko Shirahase 《Polymer Degradation and Stability》2007,92(8):1626-1631
Poly(l-lactide) (PLLA) was melt-blended with poly(p-vinyl phenol) (PVPh) using a two-roll mill, and the miscibility between PLLA and PVPh and degradation of the blend films were investigated. It was found that PLLA/PVPh blend has miscibility in the amorphous state because only single Tg was observed in the DSC and DMA measurements. The Tg of the PLLA/PVPh blend could be controlled in the temperature range from 55 °C to 117 °C by changing the PVPh weight fraction. In alkaline solution, degradation rate of PLLA/PVPh blends was faster than that of neat PLLA because PVPh could dissolve in alkaline solution. The surface morphology of degraded PLLA and PLLA/PVPh blend were observed by SEM. The surface morphology of degraded PLLA/PVPh blend was finer than that of PLLA. Young's modulus of PLLA/PVPh blend increased with increasing PVPh content. Yield stress of PLLA/PVPh blends whose PVPh content was less than 30 wt% kept the level of about 55 MPa and that of PLLA/PVPh blend whose PVPh content was 40 wt% is much lower than that of neat PLLA. 相似文献
87.
Fujiwara A Kameo Y Hoshi A Haraga T Nakashima M 《Journal of chromatography. A》2007,1140(1-2):163-167
Extraction chromatography with commercially available UTEVA resin (for uranium and tetravalent actinide) was applied for the separation of Th and U from control solutions prepared from a multi-element control solution and from sample solutions of solidified simulated waste. Thorium and U in control solutions with 1-5mol/dm(3) HNO(3) were extracted with UTEVA resin and recovered with a solution containing 0.1mol/dm(3) HNO(3) and 0.05mol/dm(3) oxalic acid to be separated from the other metallic elements. Extraction behavior of U in the sample solutions was similar to that in the control solutions, but extraction of Th was dependent on the concentration of HNO(3). Thorium was extracted from 5mol/dm(3) HNO(3) sample solutions but not from 1mol/dm(3) HNO(3) sample solutions. We conjecture that thorium fluoride formation interferes with extraction of Th. Addition of Al(NO(3))(3) and Fe(NO(3))(3), which have higher stability constant with fluoride ion than Th, does improve extractability of Th from 1mol/dm(3) HNO(3) sample solution. 相似文献
88.
Yoshio Fuchita Kazuhiko Yoshinaga Tomoko Hanaki Hiroyuki Kawano Junko Kinoshita-Nagaoka 《Journal of organometallic chemistry》1999,580(2):2258
Cyclopalladation of mono-, di- and tribenzylamine has been investigated by reacting the corresponding amines with an equimolar amount of palladium(II) acetate (reaction i), or by heating the corresponding bis-amine complexes [Pd(O2CMe)2{(PhCH2)nNH3−n}2] (n=1, 2) (reaction ii). By the reaction i, all the three amines undergo cyclopalladation. However, in the case of the reaction ii, only the dibenzylamine complex [Pd(O2CMe)2{(PhCH2)2NH}2] has been converted into a cyclopalladated complex. The reactivity of the three benzylamines towards cyclopalladation has been discussed in terms of the co-ordinating ability influenced by the bulkiness around the nitrogen atom. Temperature-dependent 1H-NMR spectra are observed for mononuclear cyclopalladated complexes [Pd(O2CMe){C6H4CH2N(CH2Ph)2–C1, N}L] (L=PPh3, AsPh3) and are attributed to the dissociation of the nitrogen atom in the cyclopalladated chelate ring. A heteroleptic bis-cyclopalladated complex [Pd[C6H4CH2N(CH2Ph)2–C1, N](C6H4CH2NMe2–C1, N)] has also been prepared. X-ray crystallographic studies on [{Pd(O2CMe)[C6H4CH2N(CH2Ph)2–C1, N]}2] and [Pd[C6H4CH2N(CH2Ph)2–C1, N](C6H4CH2NMe2–C1, N)] have been reported. 相似文献
89.
90.