全文获取类型
收费全文 | 131篇 |
免费 | 4篇 |
国内免费 | 1篇 |
专业分类
化学 | 108篇 |
力学 | 2篇 |
数学 | 10篇 |
物理学 | 16篇 |
出版年
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 10篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 1篇 |
2015年 | 4篇 |
2014年 | 4篇 |
2013年 | 14篇 |
2012年 | 2篇 |
2011年 | 14篇 |
2010年 | 5篇 |
2009年 | 5篇 |
2008年 | 10篇 |
2007年 | 5篇 |
2006年 | 5篇 |
2005年 | 4篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2002年 | 8篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1976年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有136条查询结果,搜索用时 31 毫秒
81.
A. Szady-Che
mieniecka Z. Rozwadowski T. Dziembowska E. Grech G. Wojciechowski B. Brzezinski 《Journal of Molecular Structure》2000,520(1-3):39-43
Two 3-diethylaminomethyl-5-R-salicylic aldehydes were obtained and studied in chloroform solutions by FTIR and NMR spectroscopy. The existence of an equilibrium between the structures with OHO=C and NHO intramolecular hydrogen bonds was suggested. In the case of compound 1 (R=OCH3) the OHO=C intramolecular hydrogen bond was more favorable whereas in the case of compound 2 (R=Br) the structure with the OHN intramolecular hydrogen bond was predominant. 相似文献
82.
Structural Chemistry - The object of the present study are BODIPY molecules obtained previously by Piskorz et al. (Dyes Pigm. 178:108322, 2020) for their antimicrobial activity. Structural analysis... 相似文献
83.
Piotr Łobacz Patryk Jasik Józef E. Sienkiewicz 《Central European Journal of Physics》2013,11(9):1107-1114
Semi-empirical adiabatic potential energy curves of highly excited states of the KRb molecule are calculated as a function of the internuclear distance R over a wide range from 3 to 150 a 0. The diatomic molecule is treated as an effective two-electron system by using the large core pseudopotentials and core polarization potentials. All calculations are performed by using the nonrelativistic CASSCF/MRCI method with accurate basis set functions. The spectroscopic constants of the calculated electronic states agree well with experimental data, including the recent ones from Lee et al., and with available theoretical results. 相似文献
84.
Piotr Ostalczyk Dariusz W. Brzezinski Piotr Duch Maciej Łaski Dominik Sankowski 《Central European Journal of Physics》2013,11(6):750-759
In this paper, the discrete differentiation order functions of the variable, fractional-order PD controller (VFOPD) are considered. In the proposed VFOPD controller, a variable, fractional-order backward difference is applied to perform closed-loop, system error, discrete-time differentiation. The controller orders functions which may be related to the controller input or output signal or an input and output signal. An example of the VFOPD controller is applied to the robot arm closed-loop control due to system changes in moment of inertia. The close-loop system step responses are presented. 相似文献
85.
86.
87.
88.
Karolina Wiatrak Tadeusz Morawiec Rafa Rj Patryk Kownacki Aleksandra Nitecka-Buchta Damian Niedzielski Piotr Wychowaski Agnieszka Machorowska-Pieniek Armand Cholewka Domenico Baldi Anna Mertas 《Molecules (Basel, Switzerland)》2021,26(13)
The aim of this study was to evaluate the effect of toothpaste containing natural tea tree essential oil (TTO) and ethanolic extract of propolis (EEP), on microflora and selected indicators of oral health in patients using removable acrylic partial dentures. Fifty patients with varying conditions of hygiene were divided into two groups. The study group received the toothpaste with TTO and EEP, while the control group received the same toothpaste but without TTO and EEP. At the first visit, oral hygiene and hygiene of the prostheses were carried out. Control visits took place 7 and 28 days later and compared to baseline. Indexes like API (Approximal Plaque Index), mSBI (modified Sulcus Bleeding Index), OHI-s (simplified Oral Hygiene Index), and DPI (Denture Plaque Index) were assessed in three subsequent stages, and swabs were collected from floor of the mouth area to assess the microbiota. After 7 and 28 days of using the toothpaste with TTO and EEP, a statistically significant decrease of the examined indicator values were observed in the study group as compared to the values upon the initial visit. The number of isolated strains of microorganisms in the study group was decreased or maintained at the same level, whereas in the control group an increase in the number of isolated strains was observed. The observed stabilization of oral microbiota in patients from the study group confirms the beneficial activity of toothpaste containing EEP and TTO compared to the control group. 相似文献
89.
Błażej Gierczyk Bogusława Łęska Bogumił Brzezinski Grzegorz Schroeder 《Supramolecular chemistry》2013,25(6):497-502
Three tris(oxaalkyl)phenylsilanes and two tris(oxaalkyl)phosphates were used as podand solvents in kinetic studies of proton transfer reactions between C-acids: dimethyl (4-nitrophenyl)malonate or phenyl-4-nitrophenylcyanomethane and the strong base: 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD). The acceptor numbers were measured for all new podand solvents. The kinetic parameters for studied reactions were obtained, discussed and compared with those of acetonitrile and OP(OEt) 3 as non-podand solvents. This study demonstrated that the second order rate constants strongly decreased and the energy barrier increased for the proton transfer reaction in podand solvents. Spectroscopic observations showed that ionic products were strongly stabilised and therefore their lifetime was relatively long. The podand solvents formed the ionic channels in which ionic products are strongly solvated. 相似文献
90.
Piotr Przybylski Maria Mauszynska Bogumi Brzezinski 《Journal of Molecular Structure》2005,750(1-3):152-157
The Schiff base of racemic gossypol with allylamine (GSBAL) has been studied by FT-IR, 1H and 13C NMR spectroscopy as well as by the PM5 semiempirical method. The spectroscopic methods have shown that GSBAL Schiff base exists in chloroform solution as enamine–enamine tautomer. The structure of GSBAL and the hydrogen bonds within this structure have been calculated to show that the allyl groups are out-of-planes of naphthalene rings. The strongest intramolecular hydrogen bond within the structure of GSBAL is formed between O7H–N16 atoms and it belongs to the medium strong bonds. The other hydrogen bonds, although very weak, play a very important role in stabilising the GSBAL enamine–enamine structure. 相似文献