全文获取类型
收费全文 | 207篇 |
免费 | 9篇 |
专业分类
化学 | 123篇 |
力学 | 7篇 |
数学 | 9篇 |
物理学 | 77篇 |
出版年
2023年 | 7篇 |
2022年 | 4篇 |
2021年 | 4篇 |
2020年 | 7篇 |
2019年 | 15篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 8篇 |
2015年 | 3篇 |
2014年 | 9篇 |
2013年 | 12篇 |
2012年 | 14篇 |
2011年 | 14篇 |
2010年 | 11篇 |
2009年 | 12篇 |
2008年 | 8篇 |
2007年 | 15篇 |
2006年 | 15篇 |
2005年 | 15篇 |
2004年 | 5篇 |
2003年 | 2篇 |
2000年 | 2篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有216条查询结果,搜索用时 15 毫秒
71.
A new easy-to-synthesize chemosensor, 3,3'-bis(indolyl)-4-chlorophenylmethane (hereafter S), was designed, synthesized and employed as a selective optical chemosensor for fluoride ions.(1)H NMR and density functional studies on the system have been carried out to determine the nature of the interaction between S and X(-) (X = inorganic anions) responsible for the significant fluoride-induced changes in the absorption properties of S. The experimental results reveal that abstraction of an acidic proton of S by the fluoride ion, leading to the formation of anionic species, is responsible for the spectral changes. These changes allow signaling for the fluoride ion to detect and estimate the concentration of fluoride ion present even at the submicromolar level, accurate up to 2 μM. Calculations of the transition energies of S, S(-), and S···F(-) (hydrogen bonded complex) show that only S(-) is responsible for the long-wavelength absorption band in the presence of F(-). 相似文献
72.
Summary The kinetic behaviour of cis-[Ru(bipy)2(H2O)2]2+ towards the anating ligand pyridine-2-aldoxime as a function of temperature, ligand concentration, substrate complex concentration and pH is reported and the rate expression Rate = k
1
k
2[Ru(bipy)2(H2O)2]2+ [LL]/(k
-1 + k
2[LL]) is established where k
1 is the water dissociation rate constant for the slow step, k
-1 is the rate constant for the aquation, k
2 is the ligand-capturing rate constant of the five-coordinate intermediate [Ru(bipy)2(H2O)]2+ and LL is pyridine-2-aldoxime. The reaction is pH-dependent in the pH range 3.65–5.50. The enthalpy and entropy of activation were obtained using Eyring plots. The results are in conformity with a dissociative mechanism. 相似文献
73.
Polymer‐supported palladium was synthesized by applying a single‐step wet chemical synthesis route and the resultant composite material was characterized by means of various techniques. Infrared and UV–visible spectra provided information on the chemical structure of the polymer. Microscopy techniques showed the general morphology of the polymer. The oxidation state of palladium was determined using the X‐ray photoelectron spectroscopy method. The synthesized material was applied as a heterogeneous catalyst for the Heck coupling reaction and also as an electrocatalyst for the oxidation of cysteine. 相似文献
74.
Babita Mallick Adithya Lakhsmanna Siva Umapathy 《Journal of Raman spectroscopy : JRS》2011,42(10):1883-1890
In this paper, we report on the concept and the design principle of ultrafast Raman loss spectroscopy (URLS) as a structure‐elucidating tool. URLS is an analogue of stimulated Raman scattering (SRS) but more sensitive than SRS with better signal‐to‐noise ratio. It involves the interaction of two laser sources, namely, a picosecond (ps) Raman pump pulse and a white‐light (WL) continuum, with a sample, leading to the generation of loss signals on the higher energy (blue) side with respect to the wavelength of the Raman pump unlike the gain signal observed on the lower energy (red) side in SRS. These loss signals are at least 1.5 times more intense than the SRS signals. An experimental study providing an insight into the origin of this extra intensity in URLS as compared to SRS is reported. Furthermore, the very requirement of the experimental protocol for the signal detection to be on the higher energy side by design eliminates the interference from fluorescence, which appears on the red side. Unlike CARS, URLS signals are not precluded by the non‐resonant background and, being a self‐phase‐matched process, URLS is experimentally easier. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
75.
This paper is aimed at estimating unknown parameters in a rectangular fin satisfying a predefined temperature. The differential transformation along with simplex method is used. The study has been done for different initial guess, random errors and measurement points. It is observed that, there is unique value of the convection-conduction parameter, but different conductivity and radiative parameters exist which will be useful in adjusting the parameters amongst various alternatives. 相似文献
76.
Biswajit Mallick Ramesh Chandra Behera Simanchal Panigrahi Tanmaya Badapanda Biswanath Parija Banita Behera Manas Panigrahi Madhumita Sarangi 《Indian Journal of Physics》2009,83(4):525-529
Electron microscopy is an important characterization technique for the study of textile fibre as it gives more information
on fabric wear, nature of fibre fracture, chemical degradation, abrasion, fatigue and many others. Electron Probe Micro Analyzer
(EPMA) micrographs of virgin and some neutron-irradiated samples (graphite coated) are discussed. The filament diameter, D, of virgin PET fibre obtained from EPMA study was 12.5 μn. The surface topography of single filament distinctly reveals the
core and sheath parts of the filament. The core diameter of the virgin fibre was estimated to be 1.43 μm. The fibre irradiated
at fluence 1 × 1012 n/cm2 shows radiation induced sphere like polymer balls or spherulites of diameter 2.27 μm in the expanded core region. Due to
irradiation, the sheath area crosslinks with expanded core region, which may be responsible for increase of strength and hardness
of the polymer materials. Moreover, the micrograph at 3000 X magnifications clearly shows that there is no preferred orientation
of the polymer in any direction confirming the isotropic nature of the sample.
相似文献
77.
Direct methanol fuel cells (DMFCs) within all types of fuel cells are the most viable alternative to lithium-ion batteries in the portable application and recently attracted much attention. This study reviews on passive DMFC material development with emphasis on to the performance activity, cost, durability and stability aspect. This paper has reported the basic desirable characteristics of each component with their material development. This paper has reviewed all possible materials of passive DMFC component, which can make the passive DMFC compact and feasible energy source in the future. 相似文献
78.
We report here a novel in-situ synthetic method for the
preparation of poly (o-methoxyaniline) and palladium nanoparticle composite
material. Ortho-Methoxyaniline and palladium acetate were used as the precursors;
during the reaction o-methoxyaniline was oxidized and forms poly
(o-methoxyaniline) and palladium acetate is reduced forming palladium
nanoparticles. IR and Raman spectra provide information on the structure of
the polymer. The TEM and SEM analysis are used to determine the size of the
nanoparticles and the morphology of the polymer respectively. 相似文献
79.
The article represents an experimentally supported quantitative analysis to observe the effect of time, temperature, nanoclusters’ morphology, and instantaneous volume fractions on perikinetic heat conduction and Brownian motion-based induced convection mechanisms of oxide (Al2O3 and TiO2, size 25–30 nm) based nanofluids. The appropriate models of thermal conductivity have been introduced to study the effect of various parameters such as; varying volume fractions, suspensions’ stabilities, nanoclusters’ growth, temperature, and the liquid layering. The developed model could predict the thermal conductivity enhancements of nanofluids within the accuracy of ± 0.5% to ± 4.5.0% in the temperature range from 20°C to 50°C.
Abbreviations: DI: De-ionized water; DLS: Dynamic light scattering; XRD: X-rays diffraction; TEM: Transmission electronic microscope; SDBS:Sodium dodecyl benzene sulphonate.
Figure Effect of temperature on the Brownian Reynold number for Al2O3-H2O and TiO2-H2O nanofluids. 相似文献
80.
Gour Chandra Mandal Rahul Mukherjee Khaleda Mallick Paulomi Mandal Ardhendu Sekhar Patra 《中国光学快报(英文版)》2019,(6)
We have projected and verified a bidirectional intra-/inter-radio-access-technology carrier-aggregation method for a next-generation heterogeneous mobile network supported by filter bank multicarrier(FBMC). Successful transmission of intra/inter-band carrier aggregation between five broadband FBMC signals and three bands 4G long-term-evolution-advanced signal over 50 km single-mode fiber plus 10 m free-space is successfully broadcasted by employing an incoherent light-injection scheme in downlink. In uplink, two intra-bands carrier-aggregated wireless local area network Institute of Electrical and Electronics Engineers 802.11 g signal is carried over the equal distance. High receiver sensitivity, low error vector magnitude, and clear constellation diagrams show successful delivery of different wireless services for different consumers. Therefore, the proposed hybrid system should become a potential solution for a future mobile front-haul network because of its low latency and high capacity. 相似文献