全文获取类型
收费全文 | 152篇 |
免费 | 10篇 |
专业分类
化学 | 106篇 |
力学 | 5篇 |
数学 | 13篇 |
物理学 | 38篇 |
出版年
2023年 | 3篇 |
2022年 | 8篇 |
2021年 | 4篇 |
2020年 | 5篇 |
2019年 | 6篇 |
2018年 | 10篇 |
2017年 | 5篇 |
2016年 | 12篇 |
2015年 | 4篇 |
2014年 | 4篇 |
2013年 | 15篇 |
2012年 | 10篇 |
2011年 | 6篇 |
2010年 | 9篇 |
2009年 | 7篇 |
2008年 | 3篇 |
2007年 | 5篇 |
2006年 | 1篇 |
2005年 | 2篇 |
2004年 | 5篇 |
2003年 | 6篇 |
2002年 | 3篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1998年 | 3篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1993年 | 2篇 |
1991年 | 1篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1980年 | 3篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1963年 | 1篇 |
1959年 | 1篇 |
1958年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有162条查询结果,搜索用时 15 毫秒
91.
Deepika G. Karmalkar Muniyandi Sankaralingam Mi Sook Seo Roman Ezhov Yong‐Min Lee Yulia N. Pushkar Won‐Suk Kim Shunichi Fukuzumi Wonwoo Nam 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(45):16270-16275
A mononuclear nonheme manganese(IV)–oxo complex binding the Ce4+ ion, [(dpaq)MnIV(O)]+–Ce4+ ( 1 ‐Ce4+), was synthesized by reacting [(dpaq)MnIII(OH)]+ ( 2 ) with cerium ammonium nitrate (CAN). 1 ‐Ce4+ was characterized using various spectroscopic techniques, such as UV/Vis, EPR, CSI‐MS, resonance Raman, XANES, and EXAFS, showing an Mn?O bond distance of 1.69 Å with a resonance Raman band at 675 cm?1. Electron‐transfer and oxygen atom transfer reactivities of 1 ‐Ce4+ were found to be greater than those of MnIV(O) intermediates binding redox‐inactive metal ions ( 1 ‐Mn+). This study reports the first example of a redox‐active Ce4+ ion‐bound MnIV‐oxo complex and its spectroscopic characterization and chemical properties. 相似文献
92.
Brady F. Cress Ujjwal Bhaskar Deepika Vaidyanathan Asher Williams Chao Cai Xinyue Liu Li Fu Vandhana M‐Chari Fuming Zhang Shaker A. Mousa Jonathan S. Dordick Mattheos A. G. Koffas Robert J. Linhardt 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(18):6023-6027
Heparin is a highly sulfated, complex polysaccharide and widely used anticoagulant pharmaceutical. In this work, we chemoenzymatically synthesized perdeuteroheparin from biosynthetically enriched heparosan precursor obtained from microbial culture in deuterated medium. Chemical de‐N‐acetylation, chemical N‐sulfation, enzymatic epimerization, and enzymatic sulfation with recombinant heparin biosynthetic enzymes afforded perdeuteroheparin comparable to pharmaceutical heparin. A series of applications for heavy heparin and its heavy biosynthetic intermediates are demonstrated, including generation of stable isotope labeled disaccharide standards, development of a non‐radioactive NMR assay for glucuronosyl‐C5‐epimerase, and background‐free quantification of in vivo half‐life following administration to rabbits. We anticipate that this approach can be extended to produce other isotope‐enriched glycosaminoglycans. 相似文献
93.
J. S. Baijal P. Sumitra Deepika Kothari Chandra Prakash Pran Kishan 《Hyperfine Interactions》1987,35(1-4):879-882
57Fe Mössbauer effect studies were made on titanium substituted Li?Zn ferrite with composition Li0.45+0.5tZn0.1 Tit Fe2.45–1.5tO4 (t=0.0 to 1.2) at 300K. The Mössbauer spectra for t≤0.4 show two well defined Zeeman sextets corresponding to the Fe3+ ions at tetrahedral (A) and octahedral (B) sites. The spectra for t=0.6, 0.8 and 0.9 show relaxation but can still be resolved into 2 sextets. The spectra for t=1.0, 1.2 show strong ferrimagnetic relaxation with the spectra for t=1.2 exhibiting an additional central doublet. The effect of Ti4+ substitution on the Isomer shift (I.S), Quadrupole splitting (Q.S.) and nuclear magnetic fields of Li?Zn ferrites have been reported in this paper. The I.S. was found to be independent of substitution level t, while the quadrupole splitting was observed to be negligible. The variation of hyperfine field with t has been explained on the basis of superexchange interaction and cation distribution. 相似文献
94.
95.
Deepika Chaudhary Mansi Sharma S. Sudhakar Sushil Kumar 《Plasma Chemistry and Plasma Processing》2017,37(1):189-205
In the present article we report the transition regime of hydrogenated amorphous (a-Si:H) to nano-crystalline (nc-Si:H) silicon thin films in Silane (SiH4) plasma using 27.12 MHz assisted plasma enhanced chemical vapor deposition process with the approach of plasma diagnosis. The observed transitions occur within a narrow range of diverse deposition process window and hence plasma diagnosis was vital towards envisaging this variation. Impedance Analyser (V/I probe) was used to monitor plasma characteristics during growth at various process pressure (0.03–0.4 Torr) and applied power (4–20 W). Efforts were made to understand the radicals’ formation and plasma-substrate interaction by evaluating the discharge parameters such as electron density, bulk field, and sheath voltage. From the result of plasma characterizations, highest bulk field (5.7 V/cm) in combination to low sheath voltage (0.1 V) observed on 0.2 Torr pressure at 15 W power which thus provides a clear signature of transition from a-Si:H to nc-Si:H. The structural characterizations also validate the results of observed transition where in particular it was found that the mean crystallite size (4.2 nm) with high crystalline volume fraction (42%) and wider band gap (2.01 eV) with higher hydrogen content (35%) signifies the existing nano-crystalline phase. On account of these results, an empirical relation between plasma impedance and phase angle was established in terms of expansion and contraction of two distinct discharge zones (bulk and sheath) to diagnose the phase transition. 相似文献
96.
97.
98.
99.
Subodh Kumar Deepika ChaturvediAshika Jain Poonam Tandon C.M. Nautiyal 《Vibrational Spectroscopy》2011,56(2):116-122
Normal modes of vibration and their dispersion for polyoxacyclobutane modification I (POCB I) have been obtained by using Urey-Bradley force field and the Wilson's GF matrix method as modified by Higgs. Characteristic features of the dispersion curves such as crossing, repulsion and regions of high density-of-states have been explained. Heat capacity measurements have been interpreted and the limitations of the present work discussed. 相似文献
100.
Deepika Khandelwal Sunita Hooda A. S. Brar Ravi Shankar 《Journal of polymer science. Part A, Polymer chemistry》2012,50(16):3350-3362
Copolymerization of isobornyl methacrylate and methyl acrylate ( I/M ) is performed by atom transfer radical polymerization using methyl‐2‐bromopropionate as an initiator and PMDETA/CuBr as catalyst under nitrogen atmosphere at 70 °C. The copolymer compositions determined from 1H NMR spectra are used to determine reactivity ratios of the monomers. The reactivity ratio determined from linear Kelen–Tudos method and non‐linear error‐in‐variable method, are rI = 1.25 ± 0.10, rM = 0.84 ± 0.08 and rI = 1.20, rM = 0.82, respectively. 1D, distortion less enhancement by polarization transfer and 2D, heteronuclear single quantum coherence, and total correlation spectroscopy NMR experiments are employed to resolve highly overlapped and complex 1H and 13C{1H} NMR spectra of the copolymers. The carbonyl carbon of I and M units and methyl carbon of I unit are assigned up to triad compositional and configurational sequences, whereas β‐methylene carbons are assigned up to tetrad compositional and configurational sequences. Similarly, methine carbon of I unit is assigned up to triad level. The couplings of carbonyl carbon and quaternary carbon resonances are studied in detail using 2D hetero nuclear multiple bond correlation spectra. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献