全文获取类型
收费全文 | 104篇 |
免费 | 5篇 |
专业分类
化学 | 68篇 |
力学 | 5篇 |
数学 | 11篇 |
物理学 | 16篇 |
无线电 | 9篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 3篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2017年 | 4篇 |
2016年 | 2篇 |
2015年 | 3篇 |
2014年 | 6篇 |
2013年 | 4篇 |
2012年 | 8篇 |
2011年 | 7篇 |
2010年 | 7篇 |
2009年 | 7篇 |
2008年 | 12篇 |
2007年 | 6篇 |
2006年 | 9篇 |
2005年 | 2篇 |
2004年 | 5篇 |
2003年 | 5篇 |
2002年 | 5篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1996年 | 1篇 |
排序方式: 共有109条查询结果,搜索用时 0 毫秒
91.
Analysis of the wave properties of a new two-lane continuum model with the coupling effect 下载免费PDF全文
A multilane extension of the single-lane anisotropic continuum model (GK model) developed by Gupta and Katiyar for traffic flow is discussed with the consideration of the coupling effect between the vehicles of different lanes in the instantaneous traffic situation and the lane-changing effect. The conditions for securing the linear stability of the new model are presented. The shock and the rarefaction waves, the local cluster effect and the phase transition are investigated through simulation experiments with the new model and are found to be consistent with the diverse nonlinear dynamical phenomena observed in a real traffic flow. The analysis also focuses on empirically observed two-lane phenomena, such as lane usage inversion and the density dependence of the number of lane changes. It is shown that single-lane dynamics can be extended to multilane cases without changing the basic properties of the single-lane model. The results show that the new multilane model is capable of explaining some particular traffic phenomena and is in accordance with real traffic flow. 相似文献
92.
Electroactive thiophene substituted polyacetylene derivative, namely poly(2-methylbut-2-enyl thiophene-3-carboxylate) (PMT) was synthesized. First, novel acetylene monomer was synthesized by the reaction of 3-thiophenecarboxylic acid with propargyl bromide and then polymerized with a Rh catalyst to give the corresponding polymer. FTIR and FT-Raman spectra were recorded experimentally and used for complete normal mode analysis using Wilson’s GF matrix method and Phonon dispersion of poly(2-methylbut-2-enyl thiophene-3-carboxylate). The simple non-redundant set of internal coordinates and a simplified Urey-Bradley force-field approximation was employed in normal coordinate analysis and to calculate the potential energy distribution (PED) for each fundamental vibration. The PED contribution corresponding to each of the observed frequencies shows the reliability and accuracy of the spectral analysis. Apart from detailed assignments of modes, various characteristic features of dispersion curves have also been explained as arising due to internal symmetry in energy momentum space. Predicted values of intramolecular contribution to the heat capacity of this polymer calculated by density-of-states are also being reported. 相似文献
93.
Cell-based screening systems for pharmaceuticals are desired over molecular biosensing systems because of the information
they provide on toxicity and bioavailability. However, the majority of sensing systems developed are molecular biosensing
type screening systems and cannot be easily adapted to cell-based screening. In this study, we demonstrate that protein-based
molecular sensing systems that employ a fluorescent protein as a signal transducer are amenable to cell-based sensing by expressing
the protein molecular sensing system in the cell and employing these cells for screening of desired molecules. To achieve
this, we expressed a molecular sensing system based on the fusion protein of calmodulin (CaM) and enhanced green fluorescent
protein (EGFP) in bacterial cells, and utilized these cells for the screening of CaM antagonists. In the presence of Ca2+, CaM undergoes a conformational change exposing a hydrophobic pocket that interacts with CaM-binding proteins, peptides,
and drugs. This conformational change induced in CaM leads to a change in the microenvironment of EGFP, resulting in a change
in its fluorescence intensity. The observed change in fluorescence intensity of EGFP can be correlated to the concentration
of the analyte present in the sample. Dose-response curves for various tricyclic antidepressants were generated using cells
containing CaM-EGFP fusion protein. Additionally, we demonstrate the versatility of our system for studying protein-protein
interactions by using cells to study the binding of a peptide to CaM. The study showed that the CaM-EGFP fusion protein within
the intact cells responds similarly to that of the isolated fusion protein, hence eliminating the need for any isolation and
purification steps. We have demonstrated that this system can be used for the rapid screening of various CaM antagonists that
are potential antipsychotic drugs. 相似文献
94.
A rapid detection method for nucleic acid based on bioluminescence resonance energy transfer (BRET) from the luminescence
donor Renilla luciferase to an acceptor quantum dot upon oligonucleotide probe hybridization has been developed. Utilizing a competitive
assay, we detected the target nucleic acid by correlating the BRET signal with the amount of target present in the sample.
This method allows for the detection of as little as 4 pmol (20 nM) of nucleic acid in a single-step, homogeneous format both
in vitro in a buffer matrix as well as in a cellular matrix. Using this method, one may perform nucleic acid detection in
as little as 30 min, showing much improvement over time-consuming blotting methods and solid-phase methods which require multiple
wash steps to remove unbound probe. This is the first report on the use of quantum dots as a BRET acceptor in the development
of a nucleic acid hybridization assay.
An erratum to this article can be found at 相似文献
95.
P Singh S K Gupta M J Kansara A Agarwal S Santra Rajesh Kumar A Basu P Sapna S P Sarode N B V Subrahmanyam J P Bhatt P J Raut S S Pol P V Bhagwat S Kailas B K Jain 《Pramana》2002,59(5):739-744
The folded tandem ion accelerator (FOTIA) facility set up at BARC has become operational. At present, it is used for elemental
analysis studies using the Rutherford backscattering technique. The beams of1H, 7Li, 12C, 16O and 19F have been accelerated up to terminal voltages of about 3 MV and are available for experiments. The terminal voltage is stable
within ±2 kV. In this paper, present status of the FOTIA and future plans are discussed. 相似文献
96.
Reetuparna Ghosh Sylvia Badwar Bioletty Mary Lawriniang Vibha Vansola Haladhara Naik Yeshwant Naik SaraswatulaVenkata Suryanarayana Nilesh Subhash Tawade Sapna Padmakumar Suresh Chand Sharma Shri Krishna Gupta Betylda Jyrwa Srinivasan Ganesan Pitamber Singh Ashok Goswami 《Journal of Radioanalytical and Nuclear Chemistry》2016,307(2):1481-1487
97.
98.
99.
Dubey Sapna Sharma Neetu Khandelwal Chandra L. Sharma Prem D. 《Transition Metal Chemistry》2003,28(2):176-181
The kinetics of osmium(VIII)-catalyzed oxidation of hypophosphite with hexacyanoferrate(III) in alkaline medium has been studied. The rate is independent of the concentration of the oxidant. The order with respect to hydroxide ion is variable. Rate law (1) conforms with the experimental observations.
The equilibrium constant 'K
1' for step (2)
has been evaluated kinetically to be (21 ± 5.0), (23 ± 5.0), (26 ± 6) and (32 ± 6) at 25, 30, 32 and 35 °C and I = 1.0 mol dm–3 respectively. The energy and entropy of activation were calculated to be (42 ± 2.0) kJ mol–1 and (82 ± 6.0) J K–1 mol–1 respectively. A plausible reaction mechanism has been suggested. 相似文献
100.
Jain DS Subbaiah G Sanyal M Shrivastav PS Pal U Ghataliya S Kakad A Patel H Shah S 《Rapid communications in mass spectrometry : RCM》2006,20(23):3509-3521
A high-throughput and sensitive bioanalytical method using liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) has been developed for the estimation of sibutramine and its two metabolites (M1 and M2). The extraction of sibutramine, its metabolites and imipramine (internal standard (IS)) from the plasma involved treatment with phosphoric acid followed by solid-phase extraction (SPE) using a hydrophilic-lipophilic balanced HLB cartridge. The SPE eluate without drying and reconstitution was analyzed by LC/MS/MS, equipped with a with turbo ion spray (TIS) source, operating in the positive and multiple reaction monitoring (MRM) acquisition mode. Sample preparation by this method yielded extremely clean extracts with quantitative and consistent mean recoveries; 95.12% for sibutramine, 92.74% for M1, 95.97% for M2 and 96.60% for the IS. The total chromatographic run time was 3.0 min with retention times of 2.51, 2.13, 2.09 min for sibutramine, M1, M2 and imipramine, respectively. The developed method was validated in human plasma matrix, with a sensitivity of 0.1 ng/mL (coefficient of variance (CV), 2.07%) for sibutramine, 0.1 ng/mL (CV, 3.59%) for M1 and 0.2 ng/mL (CV, 4.93%) for M2. Validation of the method for its accuracy, precision, recovery, matrix effect and stability was carried out especially with regard to real subject sample analysis. The response was linear over the dynamic range 0.1 to 8.0 ng/mL for sibutramine and M1, and 0.2 to 16.0 ng/mL for M2 with correlation coefficients of r > or = 0.9959 (sibutramine), 0.9935 (M1) and 0.9943 (M2). The method was successfully applied for bioequivalence studies in 40 human subjects with 15 mg capsule formulations. 相似文献