全文获取类型
收费全文 | 152篇 |
免费 | 7篇 |
专业分类
化学 | 79篇 |
力学 | 9篇 |
数学 | 4篇 |
物理学 | 67篇 |
出版年
2022年 | 1篇 |
2021年 | 7篇 |
2020年 | 9篇 |
2018年 | 7篇 |
2017年 | 4篇 |
2016年 | 10篇 |
2015年 | 1篇 |
2014年 | 4篇 |
2013年 | 9篇 |
2012年 | 8篇 |
2011年 | 8篇 |
2010年 | 7篇 |
2009年 | 4篇 |
2008年 | 4篇 |
2007年 | 10篇 |
2006年 | 10篇 |
2005年 | 6篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2002年 | 6篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1987年 | 6篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有159条查询结果,搜索用时 387 毫秒
101.
Haidar Ali A. Q. Baig Muhammad Kashif Shafiq 《Journal of Applied Mathematics and Computing》2017,55(1-2):313-334
There is really a lot of mathematics involved in electrical and electronic engineering. It depends on what area of electrical and electronic engineering, for example there is a lot more abstract mathematics in communication theory and signal processing and networking etc. Networks involve nodes communicating with each other. A lot of computers linked together form a network. Cell phone users form a network. Networking involves the study of the best way of implementing a network. Graph theory has found a considerable use in this area of research. In this paper, we extend this study to interconnection networks and derive analytical closed results of general Randi? index \(R_{\alpha }(G)\) for different values of “\(\alpha \)” for block shift network (BSN-1) and (BSN-2), Hierarchical hypercube (HHC-1) and (HHC-2). We also compute first Zagreb, \(\textit{ABC}\), \(\textit{GA}\), \(\textit{ABC}_{4}\) and \(\textit{GA}_{5}\) indices and give closed formulae of these indices for Hierarchical interconnection networks. 相似文献
102.
Oan Muhammad Sahito Hassan Imran Afridi Jameel Ahmed Baig 《International journal of environmental analytical chemistry》2015,95(11):1066-1079
In the present study, three-step Community Bureau of Reference sequential extraction scheme (BCR-SES) and single extraction methods were performed to assess the mobility and availability of heavy metals (Cd, Cu, Pb, Fe and Zn) in an agricultural soil before and after amendment with poultry waste (PW).The PW samples were collected from poultry farms, situated in Hyderabad Sindh, Pakistan. The extractable heavy metals were measured by flame and electrothermal atomic absorption spectrometry. The validation of the method was carried out by analysis of a certified reference material of soil amended with sewage sludge (BCR-483). The single extractions using calcium chloride and EDTA, separately, while BCR-SESs were developed to evaluate the available heavy metals to plants and their environmental accessibility for control soil (CS), PW and soil amended with PW (SPW).The pH of the PW and SPW were found to be < 6.0, which may enhance the leaching of heavy metals to agricultural soil. The results from the partitioning study indicated that easily mobilised forms (acid exchangeable) of Cd were higher than other heavy metals. The oxidisable fractions of all heavy metals were dominant in PW and SPW as compared to found in CS samples. The EDTA- and CaCl2-extractable heavy metals correspond to 5.0 to 10 and 0.5 to 3.0%, respectively of total contents in all three solid samples. Contamination factors revealed that the retention of Pb and Zn were higher compared with Cu, Cd and Fe in CS, PW and SPW samples. 相似文献
103.
Kazi TG Baig JA Shah AQ Kandhro GA Khan S Afridi HI Kolachi NF Wadhwa SK Shah F Baig AM 《Journal of AOAC International》2011,94(1):293-299
A simple and rapid cloud point extraction (CPE) procedure was applied for preconcentration of trace quantities of arsenic (As) in scalp hair samples. The samples were subjected to microwave-assisted digestion in a mixture of nitric acid and hydrogen peroxide (2 + 1, v/v) prior to preconcentration by CPE. The As in digested samples was complexed with ammonium pyrrolidine dithiocarbamate (APDC), and the resultant As-PDC complex was extracted by a nonionic surfactant, octylphenoxypolyethoxyethanol (Triton X-114). After centrifugation, the surfactant-rich phase was diluted with 0.1 M HNO3 in methanol and analyzed by electrothermal atomic absorption spectrometry. The experimental parameters, i.e., amount of APDC, concentration of Triton X-114, equilibrium temperature and time, were optimized. For validation of the proposed method, a certified reference material (CRM) of human hair (BCR 397) was used. No significant difference (P > 0.05) was observed between the experimental results and certified values of the CRM (paired t-test). The LOD and LOQ obtained under the optimal conditions were 0.025 and 0.083 microg/kg, respectively. The developed method was applied for the determination of As in scalp hair samples from male and female subjects of two villages of Khairpur Mir's, Pakistan. 相似文献
104.
Kolachi NF Kazi TG Afridi HI Khan S Baig JA Wadhwa SK Shah AQ Shah F 《Journal of AOAC International》2011,94(4):1069-1075
Advanced extraction methods have been developed for direct speciation of dissolved inorganic and organic selenium (Se) species in aqueous extracts of medicinal plants (MPs). The inorganic species of Se (SeIV and SeVI) were separated from organic forms by adsorbing inorganic Se on alumina, while the organic Se was not retained. The retained inorganic Se species was eluted with 10 mL 0.2 M HCl. The total inorganic Se species was determined after prereduction of SeVI into SeIV with concentrated HCl. The SeIV in the eluent and total inorganic Se species were then complexed with diethyldithiocarbamate. The resultant complexes were entrapped in the nonionic surfactant Triton X-114. The total Se, organic Se, total inorganic Se, and SeIV species were determined by electrothermal atomic absorption spectrometry with a modifier. The SeVI concentration was obtained by subtracting SeIV from total inorganic Se contents. The main factors affecting the methodologies were investigated in detail. Under the optimized experimental conditions, the LOD for SeIV was 50 microg/L. Among dissolved inorganic and organic Se species in aqueous extracts of MPs, organic Se species were present in the range of 74-84%, SeIV 3.62-7.47%, and SeVI 12.4-18.57% of total Se contents. 相似文献
105.
Sadia Baig Pankaj Kumar Jenner Ngai Prof. Yuning Li Dr. Safeer Ahmed 《Chemphyschem》2020,21(9):895-907
This work reports development of yttrium doped copper oxide (Y−CuO) as a new hole transport material with supplemented optoelectronic character. The pure and Y-doped CuO thin films are developed through a solid-state method at 200 °C and recognized as high performance p-channel inorganic thin-film transistors (TFTs). CuO is formed by oxidative decomposition of copper acetylacetonate, yielding 100 nm thick and conductive (40.9 S cm−1) compact films with a band gap of 2.47 eV and charge carrier density of ∼1.44×1019 cm−3. Yttrium doping generates denser films, Cu2Y2O5 phase in the lattice, with a wide band gap of 2.63 eV. The electrical conductivity increases nine-fold on 2 % Y addition to CuO, and the carrier density increases to 2.97×1021 cm−3, the highest reported so far. The TFT devices perform remarkably with high field-effect mobility (μsat) of 3.45 cm2 V−1 s−1 and 5.3 cm2 V−1 s−1, and considerably high current-on/off ratios of 0.11×104 and 9.21×104, for CuO and Y−CuO films, respectively (at −1 V operating voltage). A very small width hysteresis, 0.01 V for CuO and 1.92 V for 1 % Y−CuO, depict good bias stability. Both the devices work in enhancement mode with stable output characteristics for multiple forward sweeps (5 to −60 V) at −1Vg. 相似文献
106.
Ferit G"{U}RB"{U}Z 《数学年刊B辑(英文版)》2020,41(1):77-98
Let L =-?+V(x) be a Schr?dinger operator, where ? is the Laplacian on ■~n,while nonnegative potential V(x) belonging to the reverse H?lder class. The aim of this paper is to give generalized weighted Morrey estimates for the boundedness of Marcinkiewicz integrals with rough kernel associated with Schr?dinger operator and their commutators.Moreover, the boundedness of the commutator operators formed by BMO functions and Marcinkiewicz integrals with rough kernel associated with Schr?dinger operators is discussed on the generalized weighted Morrey spaces. As its special cases, the corresponding results of Marcinkiewicz integrals with rough kernel associated with Schr?dinger operator and their commutators have been deduced, respectively. Also, Marcinkiewicz integral operators, rough Hardy-Littlewood(H-L for short) maximal operators, Bochner-Riesz means and parametric Marcinkiewicz integral operators which satisfy the conditions of our main results can be considered as some examples. 相似文献
107.
Dénès Georges Muntasar Abdualhafeed Kozak Kathy M. Baig Arif A. White Donald J. 《Hyperfine Interactions》2002,141(1-4):255-260
Hyperfine Interactions - SnF2 is an important toothpaste ingredient, added for the provision of clinical efficacy for hard and soft tissue diseases and in breath protection. Synthetic calcium... 相似文献
108.
N. Amin S. Mahmood M. Saleem M. A. Kalyar M. A. Baig 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,40(3):331-337
The photoionization cross-sections from the 2p2P1/2, 3/2, 3d2D3/2, 5/2 and 3s2S1/2 excited states of lithium have
been measured at different ionizing laser wavelengths, above the first
ionization threshold. The experiments are performed by using a thermionic
diode working in the space charge limited mode and the cross-sections are
measured by employing the saturation technique. By changing the ionization
photon energy, a smooth frequency dependence of the cross-sections has been
observed for the 2p and 3d states. The cross-section from the 3s excited
state has been measured at a single photon energy. The measured values of
the photoionization cross are compared with the available data. 相似文献
109.
B. S. Yilbas I. H. Toor C. Karatas F. Patel M.M.A. Baig 《Surface and interface analysis : SIA》2012,44(10):1364-1369
Laser controlled melting of metal surface provides a local treatment with improved surface properties such as corrosion resistance. In the present study, laser surface treatment of iron base superalloy (A286) is carried out. The corrosion resistance of the laser‐treated surface is examined through potentiodynamic tests using 0.5 N NaCl solution. The microstructural and morphological changes in the laser‐treated layer are investigated incorporating scanning electron microscopy (SEM), X‐ray diffraction (XRD) and energy dispersive spectroscopy. The residual stress formed at the laser‐treated surface is measured using the XRD technique. It is found that laser treatment enhances corrosion resistance of A286 superalloy surface, which is attributed to the formation of fine grains and dense layer at the treated surface. Although locally scattered few corrosion induced microcracks are observed at the treated surface, they are not extended to form large cracks or crack network at the surface. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
110.
P. J. Kunert D. Georgen L. Bogunia M. T. Baig M. A. Baggash M. Johanning Ch. Wunderlich 《Applied physics. B, Lasers and optics》2014,114(1-2):27-36
We present the design, fabrication, and characterization of a segmented surface ion trap with integrated current-carrying structures. The latter produce a spatially varying magnetic field necessary for magnetic-gradient-induced coupling between ionic effective spins. We demonstrate trapping of strings of 172Yb+ ions and characterize the performance of the trap and map magnetic fields by radio frequency-optical double-resonance spectroscopy. In addition, we apply and characterize the magnetic gradient and demonstrate individual addressing in a string of three ions using RF radiation. 相似文献