全文获取类型
收费全文 | 225篇 |
免费 | 5篇 |
专业分类
化学 | 154篇 |
晶体学 | 1篇 |
力学 | 2篇 |
数学 | 36篇 |
物理学 | 37篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 2篇 |
2021年 | 4篇 |
2020年 | 8篇 |
2019年 | 7篇 |
2018年 | 7篇 |
2017年 | 4篇 |
2016年 | 5篇 |
2015年 | 6篇 |
2014年 | 11篇 |
2013年 | 19篇 |
2012年 | 17篇 |
2011年 | 26篇 |
2010年 | 9篇 |
2009年 | 9篇 |
2008年 | 13篇 |
2007年 | 8篇 |
2006年 | 12篇 |
2005年 | 9篇 |
2004年 | 10篇 |
2003年 | 3篇 |
2002年 | 6篇 |
2001年 | 2篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1988年 | 2篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1933年 | 2篇 |
1932年 | 2篇 |
排序方式: 共有230条查询结果,搜索用时 15 毫秒
71.
Bhupesh Kumar Mishra Arup Kumar Chakrabartty Debajyoti Bhattacharjee Ramesh Chandra Deka 《Structural chemistry》2013,24(5):1621-1626
Quantum mechanical calculations are carried out on the reactions of CH3OCHCl2 (DCDME) with Cl atom by means of DFT and couple cluster methods. The geometries of the reactants, products, and transition states involved in the reaction pathways are optimized at BHandHLYP level of theory using 6-311G(d,p) basis set. Transition states are searched on the potential energy surface involved during the reaction channels, and each of the transition states is characterized by the presence of only one imaginary frequency. The existence of transition states on the corresponding potential energy surface is ascertained by performing intrinsic reaction coordinate calculation. Single point energy calculations are performed at CCSD(T) level using the same basis set. The hydrogen abstraction rate constant for the title reaction is calculated at 298 K and atmospheric pressure using the canonical transition state theory including tunneling correction. The calculated value for rate constant as 1.204 × 10?12 cm3 molecule?1 s?1 is found to be in very good agreement with the recent experimental data. The percentage contributions of both reaction channels are also reported at 298 K. 相似文献
72.
Study of electron drift velocity caused by Etimes B motion is done with the help of a Mach probe in a dc cylindrical magnetron sputtering system at different plasma discharge parameters like discharge voltage, gas pressure and applied magnetic field strength. The interplay of the electron drift with the different discharge parameters has been investigated. Strong radial variation of the electron drift velocity is observed and is found to be maximum near the cathode and it decreases slowly with the increase of radial distance from the cathode. The sheath electric field, E measured experimentally from potential profile curve using an emissive probe is contributed to the observed radial variation of the electron drift velocity. The measured values of the drift velocities are also compared with the values from the conventional theory using the experimental values of electric and magnetic fields. This study of the drift velocity variation is helpful in providing a useful insight for determining the discharge conditions and parameters for sputter deposition of thin film. 相似文献
73.
Silicon nanoparticles formed using low energy (<50 keV) silver ion implantation in crystalline Si exhibit broad band light emission from ultraviolet (UV) to green. The formation of nanoparticles is confirmed using high resolution electron microscopy (HRTEM) and the resulting microscopy is used to obtain the size distribution of Si nanoparticles. Photoluminescence (PL) spectra were observed in the range of the UV to the green. The origin of emission is most likely from highly localized defects at the Si/SiO2 which is further confirmed from Photoluminescence Excitation (PLE) and effective mass theory estimation. 相似文献
74.
Kiron Kumar Ghosh Alexander Uttry Arup Mondal Francesca Ghiringhelli Philipp Wedi Manuel van Gemmeren 《Angewandte Chemie (International ed. in English)》2020,59(31):12848-12852
We report the ligand‐enabled C?H activation/olefination of free carboxylic acids in the γ‐position. Through an intramolecular Michael addition, δ‐lactones are obtained as products. Two distinct ligand classes are identified that enable the challenging palladium‐catalyzed activation of free carboxylic acids in the γ‐position. The developed protocol features a wide range of acid substrates and olefin reaction partners and is shown to be applicable on a preparatively useful scale. Insights into the underlying reaction mechanism obtained through kinetic studies are reported. 相似文献
75.
Bhupesh Kumar Mishra Arup Kumar Chakrabartty Ramesh Chandra Deka 《Structural chemistry》2014,25(2):463-470
The mechanism, kinetics, and thermochemistry of the gas-phase reactions of CF2ClC(O)OCH2CH3,ethyl chlorodifluoroacetate (ECDFA) with the OH radical and Cl atom are investigated. Geometry optimization and frequency calculations have been performed at the MPWB1K/6-31+G(d,p) level of theory and energetic information is refined by using G2(MP2) theory. Transition states are searched on the potential energy surface of reaction channels and each of the transition states is characterized by the presence of only one imaginary frequency. Connections of the transition states between designated local minima are confirmed by intrinsic reaction coordinate calculation. Theoretically calculated rate constants at 298 K using the Canonical Transition State Theory are found to be in good agreement with the experimentally measured ones. Using group-balanced isodesmic reactions as working chemical reactions, the standard enthalpies of formation for CF2ClC(O)OCH2CH3, CF2ClC(O)OCH2CH2, and CF3C(O)OCHCH3 are also reported for the first time. The hydrogen abstraction occurs mainly from –CH2 group. The T1 diagnostic calculation suggests that the multi-reference character is not an issue for such systems. The estimated atmospheric life time of ECDFA is expected to be around 24 days. 相似文献
76.
77.
Arup Bose 《Annals of the Institute of Statistical Mathematics》1990,42(4):753-768
We prove that the bootstrap principle works very well in moving average models, when the parameters satisfy the invertibility
condition, by showing that the bootstrap approximation of the distribution of the parameter estimates is accurate to the ordero(n
−1/2) a.s. Some simulation studies are also reported. 相似文献
78.
Patra SK Rahaman SM Majumdar M Sinha A Bera JK 《Chemical communications (Cambridge, England)》2008,(22):2511-2513
Oxidative additions of dichloromethanes to a diiridium(i) core, bridged by 2-ferrocenyl-1,8-naphthyridines (NP-Fc), provide an iridium(II) dimer, [IrCl2(CO)2(eta 1-NP-Fc)]2, featuring an unsupported Ir-Ir single bond (2.7121(8) A). 相似文献
79.
Vertical detachment energies (VDE) and UV/Vis absorption spectra of hydrated carbonate radical anion clusters, CO3.?.n H2O (n=1–8), are determined by means of ab initio electronic structure theory. The VDE values of the hydrated clusters are calculated with second‐order Moller–Plesset perturbation (MP2) and coupled cluster theory using the 6‐311++G(d,p) set of basis functions. The bulk VDE value of an aqueous carbonate radical anion solution is predicted to be 10.6 eV from the calculated weighted average VDE values of the CO3.?.n H2O clusters. UV/Vis absorption spectra of the hydrated clusters are calculated by means of time‐dependent density functional theory using the Becke three‐parameter nonlocal exchange and the Lee–Yang–Parr nonlocal correlation functional (B3LYP). The simulated UV/Vis spectrum of the CO3.?.8 H2O cluster is in excellent agreement with the reported experimental spectrum for CO3.? (aq), obtained based on pulse radiolysis experiments. 相似文献
80.
Dr. Sruti Mondal Tanmoy Pain Dr. Marco Villa Dr. Sara Angeloni Dr. Arup Tarai Prof. Dr. Paola Ceroni Dr. Sanjib Kar 《欧洲无机化学杂志》2023,26(24):e202300283
The synthesis, structural, spectroscopic characterization, and DFT/TD-DFT calculations of antimony corroles are reported herein. The studied complexes can be described as [(Corr)SbIII] and [(Corr)(oxo)SbV]2, where Corr is the trianion of corrole. All these complexes are diamagnetic in nature as is evident from sharp peaks with normal chemical shifts in the 1H NMR spectra. Single crystal XRD analysis reveals that the antimony(V) corrole complex is the bis-μ-oxo-bridged dinuclear antimony(V). Both the tetra and hexa-coordinated [(Corr)SbIII] and [(Corr)(oxo)SbV]2 antimony complexes adopt domed-structure with weak d-π electron coupling. The Sb−O bond distances in the co-facial dimer of [(Corr)(oxo)SbV]2 are 1.9802(16) Å (DFT: 2.0141 Å ) (for Sb1−O1), and 1.9639(17) Å (DFT: 1.9957 Å ) (for Sb2−O2) respectively. We observed that even though iodosobenzene is frequently used to oxidize [(Corr)SbIII] species, the oxidation of [(Corr)SbIII] is indeed very facile in nature and it even occurred in the air-equilibrated CHCl3 solution while storing for few days. Excitation of these antimony (III/V) corrole complexes in DCM/MeOH (1 : 1) at 77 K results in red emission with maxima at 640–720 nm. The singlet oxygen production of [(Corr)(oxo)SbV]2 has a quantum yield of 69 % and is two times higher than the analogous [(Corr)SbIII] derivatives. 相似文献