全文获取类型
收费全文 | 253篇 |
免费 | 11篇 |
国内免费 | 1篇 |
专业分类
化学 | 183篇 |
晶体学 | 5篇 |
力学 | 5篇 |
数学 | 16篇 |
物理学 | 56篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 6篇 |
2019年 | 15篇 |
2018年 | 7篇 |
2017年 | 4篇 |
2016年 | 14篇 |
2015年 | 12篇 |
2014年 | 17篇 |
2013年 | 16篇 |
2012年 | 22篇 |
2011年 | 24篇 |
2010年 | 8篇 |
2009年 | 9篇 |
2008年 | 13篇 |
2007年 | 16篇 |
2006年 | 7篇 |
2005年 | 9篇 |
2004年 | 3篇 |
2003年 | 3篇 |
2002年 | 6篇 |
2001年 | 2篇 |
2000年 | 6篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 4篇 |
1989年 | 1篇 |
1987年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1977年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有265条查询结果,搜索用时 218 毫秒
151.
Dinda Soumitra Sarkar Koushik Panda Bikash Kumar Pramanik Kausikisankar Ganguly Sanjib 《Transition Metal Chemistry》2022,47(1):31-38
Transition Metal Chemistry - By using a multifunctional diarylazooxime ligand LNOH 1, incorporating electron deficient azo chromophore in conjunction with a pendant π-electron-rich naphthyl... 相似文献
152.
153.
We study optimal control of Markov processes with age-dependent transition rates. The control policy is chosen continuously over time based on the state of the process and its age. We study infinite horizon discounted cost and infinite horizon average cost problems. Our approach is via the construction of an equivalent semi-Markov decision process. We characterise the value function and optimal controls for both discounted and average cost cases. 相似文献
154.
The refluxing of a mixture of ethylcyanoacetate, aromatic aldehydes, and primary monoamines in ethanol produces highly substituted 2-amino-6-pyridones such as 2-amino-1-(alkyl)-5-cyano-6-oxo-4-(aryl)-1,6-dihydropyridine-3-ethylcarboxylates in one-pot. On the other hand the refluxing of a mixture of ethylcyanoacetate, aromatic aldehydes, and primary diamines (1,2-ethylenediamine/1,3-propylenediamine) in ethanol furnishes symmetrical zwitterionic 2-pyridones such as 1-(2-amino-ethyl/3-amino-propyl)-6-hydroxy-2-oxo-4-(aryl)-1,2-dihydropyridine-3,5-dicarbonitriles. The result shows that primary diamines and monoamines react differently in the reactions, which provides new mechanistic insight into the regioselective synthesis of these biologically important compounds. 相似文献
155.
The present research deals with the development of a hybrid yeast strain with the aim of converting pentose and hexose sugar components of lignocellulosic substrate to bioethanol by fermentation. Different fusant strains were obtained by fusing protoplasts of Saccharomyces cerevisiae and xylose-fermenting yeasts such as Pachysolen tannophilus, Candida shehatae and Pichia stipitis. The fusants were sorted by fluorescent-activated cell sorter and further confirmed by molecular characterization. The fusants were evaluated by fermentation of glucose?Cxylose mixture and the highest ethanol producing fusant was used for further study to ferment hydrolysates produced by acid pretreatment and enzymatic hydrolysis of cotton gin waste. Among the various fusant and parental strains used under present study, RPR39 was found to be stable and most efficient strain giving maximum ethanol concentration (76.8?±?0.31?g L?1), ethanol productivity (1.06?g L?1 h?1) and ethanol yield (0.458?g g?1) by fermentation of glucose?Cxylose mixture under test conditions. The fusant has also shown encouraging result in fermenting hydrolysates of cotton gin waste with ethanol concentration of 7.08?±?0.142?g L?1, ethanol yield of 0.44?g g?1, productivity of 0.45?g L?1?h?1 and biomass yield of 0.40?g g?1. 相似文献
156.
Zhang J Biradar AV Pramanik S Emge TJ Asefa T Li J 《Chemical communications (Cambridge, England)》2012,48(52):6541-6543
A new layered MOF material [Co(Hoba)(2)·2H(2)O] (1) (H(2)oba = 4,4'-oxybis(benzoic acid)) has been synthesized and used as a highly recyclable heterogeneous catalyst for olefin epoxidation reactions. Both high conversion (96%) and high selectivity of epoxide products (96%) are achieved. 相似文献
157.
Ghatak C Rao VG Pramanik R Sarkar S Sarkar N 《Physical chemistry chemical physics : PCCP》2011,13(9):3711-3720
The fluorescence resonance energy transfer (FRET) in a lipid bilayer system containing two different donors and one common acceptor at below and above transition temperature has been studied and all the FRET parameters are analyzed using steady state and time-resolved fluorescence spectroscopy. Using dynamic light scattering measurement, we have followed the process of preparation of small unilamellar vesicles, and by following the FRET parameters of C-153-Rh6G and C-151-Rh6G pairs inside SUVs at 16 °C and 33 °C (T(m) = 23.9 °C) we have noticed that there is greater effect of temperature on the FRET parameters in case of the C-153-Rh6G pair than that of the C-151-Rh6G pair. Finally we have concluded that this difference is due to their different location inside the lipid bilayer in which fluidity of the long alkyl chain markedly affects the FRET parameters for C-153-Rh6G pair embedded inside a small unilamellar vesicle of size 20-50 nm. 相似文献
158.
Electronic and magnetic properties of metal-(4,4'-bipyridine) sandwich complexes and their nanowires
Using calculations based on density functional theory, we have investigated the geometric, energetic, and magnetic properties of complexes of 4,4'-bipyridine (BPY) with metal atoms M (= Li, V, and Ti). The systems of interest include BPY-M(2) and BPY(2)-M(2) complexes and (BPY-M(2))(x) nanowires in which the sandwich structure is stacked infinitely along one direction. For each of these systems, a detailed analysis was performed on the electronic structure. First, we found that BPY-M (M = V and Ti) binding is stronger than BPY-Li binding because of the covalent nature of the former interaction. The difference in the magnetic properties of BPY-M(2) and BPY(2)-M(2) (M = V and Ti) complexes can be understood in terms of the different strengths of the M-M interactions mediated by d(M) or sd(M)-hybridized orbitals. Second, we found that the (BPY-Li(2))(x) nanowire is a semiconductor, whereas (BPY-V(2))(x) and (BPY-Ti(2))(x) nanowires are magnetic metals due to the spin-polarization in d(z)2(M)-derived bands. 相似文献
159.
Pramanik S Nakamura K Usui K Nakano S Saxena S Matsui J Miyoshi D Sugimoto N 《Chemical communications (Cambridge, England)》2011,47(10):2790-2792
We found that Hoogsteen base pairs were stabilized by molecular crowding and a histone H3-mimicking peptide, which was not observed for Watson-Crick base pairs. Our findings demonstrate that the type of DNA base pair is critical for the interaction between DNA and histones. 相似文献
160.
Single‐crystal X‐ray diffraction studies of two terminally protected tetrapeptides Boc‐Ile‐Aib‐Val‐m‐ABA‐OMe ( I ) and Boc‐Ile‐Aib‐Phe‐m‐ABA‐OMe ( II ) (Aib=α‐aminoisobutyric acid; m‐ABA=meta‐aminobenzoic acid) reveal that they form continuous H‐bonded helices through the association of double‐bend (type III and I) building blocks. NMR Studies support the existence of the double‐bend (type III and I) structures of the peptides in solution also. Field emission scanning electron‐microscopic (FE‐SEM) and high‐resolution transmission electron‐microscopic (HR‐TEM) images of the peptides exhibit amyloid‐like fibrils in the solid state. The Congo red‐stained fibrils of peptide I and II , observed between crossed polarizers, show green‐gold birefringence, a characteristic of amyloid fibrils. 相似文献