全文获取类型
收费全文 | 930篇 |
免费 | 23篇 |
国内免费 | 4篇 |
专业分类
化学 | 791篇 |
晶体学 | 4篇 |
力学 | 20篇 |
数学 | 45篇 |
物理学 | 97篇 |
出版年
2023年 | 9篇 |
2022年 | 16篇 |
2021年 | 36篇 |
2020年 | 25篇 |
2019年 | 32篇 |
2018年 | 43篇 |
2017年 | 31篇 |
2016年 | 38篇 |
2015年 | 38篇 |
2014年 | 20篇 |
2013年 | 59篇 |
2012年 | 46篇 |
2011年 | 50篇 |
2010年 | 37篇 |
2009年 | 29篇 |
2008年 | 47篇 |
2007年 | 45篇 |
2006年 | 46篇 |
2005年 | 34篇 |
2004年 | 25篇 |
2003年 | 28篇 |
2002年 | 22篇 |
2001年 | 18篇 |
2000年 | 12篇 |
1999年 | 10篇 |
1998年 | 6篇 |
1997年 | 7篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1992年 | 8篇 |
1991年 | 9篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1983年 | 8篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 8篇 |
1978年 | 4篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1975年 | 5篇 |
1974年 | 8篇 |
1972年 | 5篇 |
1971年 | 4篇 |
1969年 | 4篇 |
1967年 | 3篇 |
1966年 | 3篇 |
排序方式: 共有957条查询结果,搜索用时 250 毫秒
921.
Yuriy N. Malyar Mikhail A. Mikhailenko Natalia A. Pankrushina Alexander N. Mikheev Ilia V. Eltsov Svetlana A. Kuznetsova Anna S. Kichkailo Tatyana P. Shakhtshneider 《Chemical Papers》2018,72(5):1257-1263
In this work, a water-soluble supramolecular complex was synthesized in an aqueous suspension of betulin diacetate (BDA) and arabinogalactan (AG) upon microwave heating. Microwave heating allows reducing the time required for the complex formation, compared with conventional heating in a water bath. The specific effect of microwave irradiation on the initial reagents and preparation of a supramolecular complex was studied. In contrast to conventional heating, under microwave heating AG macromolecules may break into roughly equal fragments when the temperature increases up to 100 °C. A change in the surface morphology of BDA crystals under microwave heating of the suspension suggests that microwave irradiation facilitates the dissolution of BDA in water. It has been shown that the use of dimethylsulfoxide as a reaction medium for microwave heating led to a decrease in BDA content in the product due to the inclusion of DMSO into AG macromolecules. The BDA–AG complex was isolated from the microwave-heated aqueous solution, after water evaporation, as a thin amorphous film, which exhibited antitumor activity against Ehrlich ascites carcinoma cells and can be a promising material for pharmacological applications. 相似文献
922.
Oxana L. Gribkova Alexander A. Nekrasov Varvara A. Cabanova Tatyana V. Krivenko Natalia V. Nekrasova Sergey A. Yakovlev Evgeny I. Terukov Alexey R. Tameev 《Chemical Papers》2018,72(7):1741-1752
Polymer nanocomposite based on stable water-dispersible polyaniline complex with poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PANI–PAMPSA) and 2D molybdenum disulphide (MoS2) was developed. The nanocomposite layers obtained by drop-casting were characterized by Vis–NIR- and FTIR spectroscopies, as well as by atomic force, transmission electron, and Kelvin-probe microscopies, X-ray diffraction, cyclic voltammetry, Hall effect, and DC-conductivity measurements. It was shown that the preparation procedure allows easy adjusting of MoS2 content in the nanocomposite resulting in the growth of DC conductivity by up to six times in the case of 20 wt% MoS2 as compared with the additive-free PANI–PAMPSA complex. FTIR spectroscopy revealed the existence of hydrophobic interactions between PANI–PAMPSA and 2D MoS2 nanophase, which facilitate interchain electron transfer. Hall effect studies showed that while increasing MoS2 content in the nanocomposite, a transition occurs from monopolar hole transport, characteristic of PANI–PAMPSA, to ambipolar transport. This feature makes the obtained PANI–PAMPSA/MoS2 composite a promising material for different optoelectronic devices, in particular tandem solar cells. 相似文献
923.
Tatyana V. Tyumkina Nataliya N. Makhmudiyarova Guzeliya M. Kiyamutdinova Ekaterina S. Meshcheryakova Kamil Sh. Bikmukhametov Marat F. Abdullin Leonard M. Khalilov Askhat G. Ibragimov Usein M. Dzhemilev 《Tetrahedron》2018,74(15):1749-1758
An efficient method has been developed for the synthesis of 7′-arylspiro{adamantane-[2,3′]-(1′,2′,4′,5′,7′-tetraoxazocanes)} by the ring transformation reaction of spiro{adamantane-[2,3’]-(1′,2′,4′,5′,7′-pentaoxacane)} with arylamines in the presence of Sm(NO3)3·6H2O as the catalyst. NMR signals of the synthesized compounds were assigned considering the conformation dynamics of the tetraoxazocane ring with two rigid peroxide bonds. The structures of some of the compounds were studied by X-ray diffraction. The thermal stability of single crystal was determined by DSC method. Compounds 7′-(2-methylphenyl)spiro{adamantane-[2,3′]-(1′,2′,4′,5′,7′-tetraoxazocane)} and 7′-(4-fluorophenyl)spiro{adamantane-[2,3′]-(1′,2′,4′,5′,7′-tetraoxazocane)} exhibited cytotoxicity towards cancer cells. 相似文献
924.
Gribanova Tatyana N. Minyaev Ruslan M. Minkin Vladimir I. Boldyrev Alexander I. 《Structural chemistry》2020,31(6):2105-2128
Structural Chemistry - The review presents results of the recent studies of non-typical forms of boron derivatives, including flat hexagonal boron, boron fullerenes, supertetrahedral boron, and... 相似文献
925.
Jodi Kraus Rupal Gupta Manman Lu Angela M. Gronenborn Mikael Akke Tatyana Polenova 《Chemphyschem》2020,21(13):1436-1443
Chemical shift tensors obtained from solid-state NMR spectroscopy are very sensitive reporters of structure and dynamics in proteins. While accurate 13C and 15N chemical shift tensors are accessible by magic angle spinning (MAS) NMR, their quantum mechanical calculations remain challenging, particularly for 15N atoms. Here we compare experimentally determined backbone 13Cα and 15NH chemical shift tensors by MAS NMR with hybrid quantum mechanics/molecular mechanics/molecular dynamics (MD-QM/MM) calculations for the carbohydrate-binding domain of galectin-3. Excellent agreement between experimental and computed 15NH chemical shift anisotropy values was obtained using the Amber ff15ipq force field when solvent dynamics was taken into account in the calculation. Our results establish important benchmark conditions for improving the accuracy of chemical shift calculations in proteins and may aid in the validation of protein structure models derived by MAS NMR. 相似文献
926.
Ludmila A. Oparina Alexander V. Artem'ev Nikita A. Kolyvanov Oksana V. Vysotskaya Nataliya A. Chernysheva Vladimir I. Smirnov Tatyana N. Borodina Nina K. Gusarova Boris A. Trofimov 《Heteroatom Chemistry》2015,26(1):72-78
Earlier unknown S‐[1‐(organosulfanyl)ethyl]‐ and S‐[1‐(organoselenyl)ethyl] dithiophosphinates were synthesized in 85–97% yields by regioselective addition of dithiophosphinic acids to diverse vinyl sulfides and selenides under mild conditions (ambient temperature, Et2O, 3 h). 相似文献
927.
Igumenova TI Brath U Akke M Palmer AG 《Journal of the American Chemical Society》2007,129(44):13396-13397
928.
Yulia G. Budnikova Oleg G. Sinyashin Tatyana P. Gryaznova Mikhail P. Egorov 《Journal of organometallic chemistry》2007,692(19):4067-4072
Convenient synthetic route to prepare the germylene complexes of tungsten pentacarbonyls, W(CO)5GeCl2 and W(CO)5GeW(CO)5, electrochemically is developed. Combined quantum-chemical/IR spectroscopic approach is used for identification of the synthesized compounds. Good agreement between theoretical and experimental spectra can be regarded as one of the proofs of their supposed structures. 相似文献
929.
Elisaveta V. Lider Eugenia V. Peresypkina Anton I. Smolentsev Valentina N. Elokhina Tatyana I. Yaroshenko Alexander V. Virovets Vladimir N. Ikorskii Ludmila G. Lavrenova 《Polyhedron》2007
Novel copper(II) complexes, molecular [Cu6(μ6-Cl)(μ3-OH)2(μ-L)6Cl9(H2O)3] · 3H2O (1) and polymeric [Cu(μ-L)(μ-OH)(H2O)2]Cl (2) (L = 4-(4-hydroxyphenyl)-1,2,4-triazole), have been prepared and characterized by X-ray structural analysis. Compound 1 appears to be an unusual example of a chloride ion with six equal Cu–Cl distances of 2.8397(3) Å. It has also been characterized by X-ray powder diffraction and magnetic measurements. Both complexes have distorted octahedral configurations of copper ions; the coordination cores are CuN2Cl2O2 or CuN2Cl3O (1) and CuN2O4 (2). 相似文献
930.
Parashchuk OD Laptinskaya TV Paraschuk DY 《Physical chemistry chemical physics : PCCP》2011,13(9):3775-3781
Donor-acceptor blends based on conjugated polymers are the heart of state-of-the-art polymer solar cells, and the control of the blend morphology is crucial for their efficiency. As the film morphology can inherit the polymer conformational state from solution, the approaches for probing and controlling the polymer conformational state in the blends are of high importance. In this study, we show that the macromolecular dynamics in solutions of the archetypical conjugated polymer, MEH-PPV, is essentially changed upon addition of an acceptor 2,4,7-trinitrofluorenone (TNF) by using dynamic light scattering (DLS). We have observed four new types of the macromolecular dynamics absent in the parent polymer determined by the polymer and acceptor content. The MEH-PPV?:?TNF ground-state charge-transfer complex (CTC) is suggested to result in these dynamics. In the dilute polymer solution, the CTC formation leads to slower dynamics as compared with the pristine polymer. This is evidence of aggregates formed by intercoil links that are the CTCs involving two conjugated segments of different coils with acceptor molecules being sandwiched between them. At low acceptor content, the aggregates are not stable but at high acceptor content, they are. In the semidilute solution at low acceptor content, the dynamics becomes faster as compared with the pristine polymer that is explained by confinement of the coupled motions of entangled polymer chains. At high acceptor content, the dynamics is far much slower with a characteristic long-range correlation at the scale 3-5 μm that is explained by aggregation of polymer chains in clusters. One can expect that the DLS technique could become a useful tool to study the nano- and microstructure of donor-acceptor conjugated polymer blends to achieve controllable morphology in the corresponding blend films. 相似文献