全文获取类型
收费全文 | 203篇 |
免费 | 4篇 |
专业分类
化学 | 101篇 |
晶体学 | 8篇 |
力学 | 6篇 |
数学 | 39篇 |
物理学 | 53篇 |
出版年
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 6篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 8篇 |
2014年 | 5篇 |
2013年 | 19篇 |
2012年 | 13篇 |
2011年 | 16篇 |
2010年 | 7篇 |
2009年 | 9篇 |
2008年 | 11篇 |
2007年 | 13篇 |
2006年 | 10篇 |
2005年 | 5篇 |
2004年 | 9篇 |
2003年 | 1篇 |
2002年 | 4篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1963年 | 1篇 |
1937年 | 1篇 |
排序方式: 共有207条查询结果,搜索用时 15 毫秒
91.
We prove the law of the iterated logarithm for solutions of Stochastic Differential Equations (SDEs) driven by continuous semiraartingales, under suitable conditions. This extends a result of Kulinich for classical diffusions to solutions of SDEs which are not necessarily Markov 相似文献
92.
93.
M Rajasekhar KU Maheswara Rao CS Sundar NB Reddy SK Nayak CS Reddy 《Chemical & pharmaceutical bulletin》2012,60(7):854-858
A simple and efficient one pot synthesis of 2-amino-4H-chromen-4-yl phosphonate derivatives has been accomplished by the condensation of salicylaldehyde, malononitrile/ethylcyanoacetate and triethyl phosphite/trimethyl phosphite in the presence of molecular iodine as catalyst in water at room temperature. All the reactions were very clean and the products were obtained in very good to excellent yields. The title compounds are characterized by IR, 1H-, 13C-, 31P-NMR and mass spectra, also studied their antimicrobial and antioxidant activity. 相似文献
94.
Kunda UM Balam SK Nemallapudi BR Chereddy SS Nayak SK Cirandur SR 《Chemical & pharmaceutical bulletin》2012,60(1):104-109
A green and efficient preparation method for the amino bisphosphonates is accomplished by simple mixing and stirring of diethylphosphite, triethylorthoformate and various amines in the presence of amberlyst-15 as catalyst at room temperature under solvent free conditions. The title compounds are characterized by IR, (1)H-, (13)C-, (31)P-NMR and mass spectra, also studied their antimicrobial and antioxidant activity. 相似文献
95.
P. Yasodha A. Bharathi M.C. Valsakumar R. Rajaraman C.S. Sundar 《Journal of solid state chemistry》2010,183(11):2602-2608
Phonons in GdBaCo2O5.5 have been identified using infrared spectroscopy and their mode assignments have been carried out using ab initio lattice dynamical calculations. Metal insulator transitions in undoped and nickel-doped GdBaCo2O5.5 have been probed using infrared absorption spectroscopy. The phonon modes corresponding to the bending mode of the CoO6 octahedra/pyramids are seen to soften, broaden and develop an asymmetry across the insulator-metal transition pointing to extensive electron phonon interaction effects in these systems. Correlated changes of the phonon line shape parameters associated with the transition indicate a suppression of TMIT with increased nickel doping of the cobalt sublattice. Temperature dependence of the octahedral stretching mode frequencies in undoped GdBaCo2O5.5 points to distinct structural distortions accompanying the high temperature metallic transition. 相似文献
96.
M. Premila S. Abhaya R. Rajaraman T.R. Ravindran G. Amarendra C.S. Sundar 《Journal of Non》2012,358(6-7):1014-1018
Iron phosphate glasses have been investigated using positron lifetime and micro Raman spectroscopy to study the crystallization kinetics and defect evolution across the glass and crystallization transitions. Positron lifetime parameters show distinct changes at temperatures corresponding to both the transitions. These changes have been understood as the signature of the evolution of open volume defects and their clustering across the amorphous to crystalline interfaces. Micro Raman measurements on annealed samples have identified the crystalline phases as Fe3(P2O7)2 and FePO4. Ab-initio positron lifetime computations reveal that the positron probes the Fe/P sites in defect free crystals. The nature of open volume defects produced upon annealing is identified by computing positron lifetimes for various possible defect clusters. A combination of both experimental and theoretical techniques has provided insights in understanding the evolution of defects across the phase transition in these glasses. 相似文献
97.
Ramendra Sundar Dey Susmita Gupta Rupankar Paira Shen-Ming Chen C. Retna Raj 《Journal of Solid State Electrochemistry》2012,16(1):173-178
Au electrode modified with the self-assembled monolayer of a heterocyclic thiol, mercaptotriazole (MTz), is used for the electroanalysis
of uric acid (UA) and ascorbic acid (AA). MTz forms a less compact self-assembly on Au electrode. The self-assembly of MTz
on Au electrode favors the oxidation of UA and AA at less positive potential. Significant decrease (∼400 mV) in the overpotential
and enhancement in the peak current for the oxidation of interfering AA with respect to the unmodified electrode is observed.
The negative shift in the oxidation peak potential of AA favors electrochemical sensing of UA without any interference. Two
well-separated voltammetric peaks for AA and UA are observed in their coexistence. The large separation between the two voltammetric
peaks allows the simultaneous or selective sensing of the analytes without compromising the sensitivity. Linear response is
obtained for a wide concentration range. This electrode could sense as low as 1 μM of UA in the presence of 10-fold excess
of interfering AA. No change in the sensitivity (0.012 μA/μM) of the electrode toward UA in the presence and absence of AA
is observed. Reproducible and stable amperometric flow injection response was obtained upon repetitive injection. 相似文献
98.
Durai S Bosley A Abulencia AB Chandrasegaran S Ostermeier M 《Combinatorial chemistry & high throughput screening》2006,9(4):301-311
We have developed two bacterial one-hybrid systems for interrogating and selecting zinc finger-DNA interactions. Our systems utilize two plasmids: a zinc finger-plasmid containing the gene for the zinc finger fused to a fragment of the alpha subunit of RNA polymerase and a reporter plasmid where the zinc finger-binding site is located upstream of a reporter gene-either the gene encoding the green fluorescent protein (GFP) or chloramphenicol acetyltransferase (CAT). Binding of the zinc finger domain to the target binding site results in a 10-fold increase in chloramphenicol resistance with the CAT reporter and an 8- to 22-fold increase in total cell fluorescence with the GFP reporter. The CAT reporter allows for sequence specific zinc fingers to be isolated in a single selection step whereas the GFP reporter enables quantitative evaluation of libraries using flow cytometry and theoretically allows for both negative and positive selection. Both systems have been used to select for zinc fingers that have affinity for the motif 5'-GGGGCAGAA-3' from a library of approximately 2 x 10(5) variants. The systems have been engineered to report on zinc finger-DNA binding with dissociation constants less than about 1 microM in order to be most applicable for evaluating binding specificity in an in vivo setting. 相似文献
99.
Subhodip Samanta Pinki Saha Sardar Shyam Sundar Maity Anirban Pal Maitrayee Basu Roy Sanjib Ghosh 《Journal of Chemical Sciences》2007,119(2):175-183
A comparative time-resolved emission studies of several naphtho-crown ethers I–V, where metal ions can be complexed in a predetermined orientation with respect to the naphthalene (Naph) π-plane and naphthalene-linked aza crown ethers (L1 and L2) have been presented. In both the systems, crown ethers and aza
crown ethers, naphthalene fluorescence gets quenched. In the systems I to V, the quenching is mainly due to efficient spin-orbit coupling (SOC) leading to greater population of the lowest triplet state
of naphthalene. This SOC depends on the orientation of the crown ring with respect to the Naph-π-plane. However, in the systems L1 and L2, the quenching is due to photoinduced electron transfer (PET) from nitrogen lone
pair of the aza crown ring to naphthalene moiety and consequent exciplex formation. The results have been interpreted using
the time-resolved emission studies of all the compounds in various solvents, their alkali metal ion complexes, and protonated
ligands. 相似文献
100.
Saimani Sundar Wonbong Jang Choonkeun Lee Yonggun Shul Haksoo Han 《Journal of Polymer Science.Polymer Physics》2005,43(17):2370-2379
Sulfonated polyimides with tertiary nitrogen in the polymer backbone were synthesized with 1,4,5,8‐naphthalenetetracarboxylic dianhydride, 4,4′‐diaminobiphenyl 2,2′‐disulfonic acid, 2‐bis[4‐(4‐aminophenoxy)phenyl]hexafluoropropane, and diaminoacrydine hemisulfate. They were crosslinked with a series of dibromo alkanes to improve the hydrolytic stability. The crosslinked sulfonated polyimide films were characterized for their thermal stability, ion‐exchange capacity (IEC), water uptake, hydrolytic stability, and proton conductivity. All the sulfonated polyimides had good thermal stability and exhibited a three‐step degradation pattern. With an increase in the alkyl chain length of the crosslinker, IEC decreased as 1.23 > 1.16 > 1.06 > 1.01, and the water uptake decreased as 7.29 > 6.70 > 6.55 > 5.63. The order of the proton conductivity of the crosslinked sulfonated polyimides at 90 °C was as follows: polyimide crosslinked with dibromo butane (0.070) > polyimide crosslinked with dibromo hexane (0.055) > polyimide crosslinked with dibromo decane (0.054). The crosslinked polyimides showed higher hydrolytic stability than the uncrosslinked polyimides. Between the crosslinked polyimides, the hydrolytic stability decreased with an increase in the alkyl chain length of the crosslinker. The crosslinked and uncrosslinked sulfonated polyimides exhibited almost the same proton conductivities. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2370–2379, 2005 相似文献