全文获取类型
收费全文 | 310篇 |
免费 | 9篇 |
专业分类
化学 | 197篇 |
晶体学 | 1篇 |
力学 | 16篇 |
数学 | 13篇 |
物理学 | 92篇 |
出版年
2023年 | 2篇 |
2022年 | 8篇 |
2021年 | 4篇 |
2020年 | 7篇 |
2019年 | 13篇 |
2018年 | 11篇 |
2017年 | 4篇 |
2016年 | 9篇 |
2015年 | 8篇 |
2014年 | 12篇 |
2013年 | 25篇 |
2012年 | 20篇 |
2011年 | 14篇 |
2010年 | 8篇 |
2009年 | 14篇 |
2008年 | 14篇 |
2007年 | 16篇 |
2006年 | 12篇 |
2005年 | 8篇 |
2004年 | 10篇 |
2003年 | 12篇 |
2002年 | 12篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1975年 | 1篇 |
1973年 | 2篇 |
1963年 | 2篇 |
排序方式: 共有319条查询结果,搜索用时 62 毫秒
311.
Ahuja G Mathur P 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,83(1):180-186
A new tetradentate bis benzimidaozlyl diamide ligand N,N'-Bis (benzimidazol-2-yl-methyl)-hexane-1,6-dicarboxamide (GBSA) has been synthesized and utilized to prepare new Fe(III) complexes with exogenous anionic ligand X=Cl(-) and NO(3)(-). Isomer shift values are in the range found for Iron in the +3 oxidation state while Quadrupole Splitting indicates large distortion from a six coordinate geometry, a finding supported by low temperature EPR work. The E(1/2) values are found to be quite cathodic indicating stability of the Iron (III) complexes. The oxidation of alcohols was investigated using [Fe(GBSA)Cl(3)] as the catalyst with TBHP as an alternate source of oxygen. The respective carbonyl products have been isolated and characterized by (1)H NMR, electronic spectroscopy, mass and IR spectral studies. 相似文献
312.
Y. Thirupathi Reddy Vijayakumar N. Sonar Peter A. Crooks Pavan K. Dasari P. Narsimha Reddy 《合成通讯》2013,43(13):2082-2088
An efficient and convenient method for the synthesis of substituted coumarins via Pechmann condensation of different phenols with ethylacetoacetate in the presence of ammonium cerium(IV) nitrate as the catalyst in a solvent- free media using both conventional heating and microwave irradiation. 相似文献
313.
A new reagent system comprising acetyl chloride, silver nitrate, and acetonitrile has been developed for the synthesis of 2-nitroglycals from the corresponding glycals. Under certain conditions, the formation of 2-nitro-1-acetamido sugars has also been observed. In addition, a few other non-carbohydrate-derived olefins also gave the corrresponding conjugated nitroolefins. 相似文献
314.
Srivari Chandrasekhar Togapur Pavan KumarKothapalli Haribabu Chada Raji ReddyChitumalla Ramesh Kumar 《Tetrahedron: Asymmetry》2011,22(6):697-702
An enantioselective Michael reaction of carbonyl compounds to nitroolefins has been accomplished using a novel chiral pyrrolidine-pyrazole catalyst. This newly prepared catalyst was found to be very effective in providing good yields as well as good diastereo- and enantio-selectivities. The mechanism of the reaction has also been substantiated by mass spectral studies. 相似文献
315.
M. Fantuzi C. M. Petrache D. Mengoni M. Axiotis D. Bazzacco G. Benzoni P. G. Bizzeti A. M. Bizzeti-Sona N. Blasi A. Bracco G. de Angelis E. Farnea A. Gadea Th. Kröll S. Leoni H. L. Liu S. Lunardi N. Marginean R. Menegazzo D. R. Napoli M. Nespolo P. Pavan C. Rossi Alvarez P. Spolaore C. A. Ur R. Venturelli F. R. Xu 《The European Physical Journal A - Hadrons and Nuclei》2008,38(1):43-51
Excited states in the very neutron-deficient122La nucleus have been established for the first time using the92Mo(40Ca, 2α1p1n) reaction at beam energies of 190 and 200MeV. The observed transitions were grouped in three bands. Configurations have been
assigned to the observed bands based on the properties extracted from the experimental data and on cranked shell model calculations. 相似文献
316.
O. Azzolini M. T. Barrera J. W. Beeman F. Bellini M. Beretta M. Biassoni C. Brofferio C. Bucci L. Canonica S. Capelli L. Cardani P. Carniti N. Casali L. Cassina M. Clemenza O. Cremonesi A. Cruciani A. D’Addabbo I. Dafinei S. Di Domizio F. Ferroni L. Gironi A. Giuliani P. Gorla C. Gotti G. Keppel M. Martinez S. Morganti S. Nagorny M. Nastasi S. Nisi C. Nones D. Orlandi L. Pagnanini M. Pallavicini V. Palmieri L. Pattavina M. Pavan G. Pessina V. Pettinacci S. Pirro S. Pozzi E. Previtali A. Puiu F. Reindl C. Rusconi K. Schäffner C. Tomei M. Vignati A. Zolotarova 《The European Physical Journal C - Particles and Fields》2018,78(5):428
The CUPID-0 detector hosted at the Laboratori Nazionali del Gran Sasso, Italy, is the first large array of enriched scintillating cryogenic detectors for the investigation of \(^{82}\)Se neutrinoless double-beta decay (\(0\nu \beta \beta \)). CUPID-0 aims at measuring a background index in the region of interest (RoI) for \(0\nu \beta \beta \) at the level of 10\(^{-3}\) counts/(keV kg years), the lowest value ever measured using cryogenic detectors. CUPID-0 operates an array of Zn\(^{82}\)Se scintillating bolometers coupled with bolometric light detectors, with a state of the art technology for background suppression and thorough protocols and procedures for the detector preparation and construction. In this paper, the different phases of the detector design and construction will be presented, from the material selection (for the absorber production) to the new and innovative detector structure. The successful construction of the detector lead to promising preliminary detector performance which is discussed here. 相似文献
317.
Sajesh P. Thomas Amol G. Dikundwar Sounak Sarkar Mysore S. Pavan Rumpa Pal Venkatesha R. Hathwar Tayur N. Guru Row 《Molecules (Basel, Switzerland)》2022,27(12)
The work carried out by our research group over the last couple of decades in the context of quantitative crystal engineering involves the analysis of intermolecular interactions such as carbon (tetrel) bonding, pnicogen bonding, chalcogen bonding, and halogen bonding using experimental charge density methodology is reviewed. The focus is to extract electron density distribution in the intermolecular space and to obtain guidelines to evaluate the strength and directionality of such interactions towards the design of molecular crystals with desired properties. Following the early studies on halogen bonding interactions, several “sigma-hole” interaction types with similar electrostatic origins have been explored in recent times for their strength, origin, and structural consequences. These include interactions such as carbon (tetrel) bonding, pnicogen bonding, chalcogen bonding, and halogen bonding. Experimental X-ray charge density analysis has proved to be a powerful tool in unraveling the strength and electronic origin of such interactions, providing insights beyond the theoretical estimates from gas-phase molecular dimer calculations. In this mini-review, we outline some selected contributions from the X-ray charge density studies to the field of non-covalent interactions (NCIs) involving elements of the groups 14–17 of the periodic table. Quantitative insights into the nature of these interactions obtained from the experimental electron density distribution and subsequent topological analysis by the quantum theory of atoms in molecules (QTAIM) have been discussed. A few notable examples of weak interactions have been presented in terms of their experimental charge density features. These examples reveal not only the strength and beauty of X-ray charge density multipole modeling as an advanced structural chemistry tool but also its utility in providing experimental benchmarks for the theoretical studies of weak interactions in crystals. 相似文献
318.
G. V. Pavan Kumar 《Journal of Raman spectroscopy : JRS》2009,40(12):2069-2073
Surface‐enhanced Raman scattering from carbon nanotube bundles adsorbed with plasmon‐tunable Ag‐core Au‐shell nanoparticles (Ag@Au nps) was carried out for the first time. By utilizing nanoparticles whose plasmon resonance peak (541, 642 nm) closely matches the commonly used Raman excitation sources (532, 632.81 nm), we can observe a large enhancement in the Raman signatures of carbon nanotubes. We obtain greater enhancement in the Raman signal for the above case when compared to nanotubes adsorbed with conventional Ag, Au or other ‘off resonant’ Ag@Au nps. The power‐dependent SERS experiment on single‐walled nanotubes (SWNTs) with resonant Ag@Au nps reveals a linear behavior between the G‐band intensity and the photon flux density, which is in agreement with the vibrational pumping model of SERS. The observed enhancement by resonance matching is pronounced for carbon nanotubes and may lead to insights into understanding nanotube–nanoparticle interaction. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
319.
Harshita Shet Manisha Patel Jyoti M. Waikar Dr. Pavan M. More Dr. Yogesh S. Sanghvi Dr. Anant R. Kapdi 《化学:亚洲杂志》2023,18(1):e202201006
The dimethylamino functionality has significant importance in industrially relevant molecules and methodologies to install these efficiently are highly desirable. We report herein a highly efficient, room-temperature dimethylamination of chloroheteroarenes performed via the in-situ generation of dimethylamine using N,N-dimethylformamide (DMF) as precursor wiith a large substrate scope that includes various heteroarenes, purines as well as commercially relevant drugs such as altretamine, ampyzine and puromycin precursor. 相似文献