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71.
The traditional standard stochastic system models, such as the autoregressive (AR), moving average (MA) and autoregressive moving average (ARMA) models, usually assume the Gaussian property for the fluctuation distribution, and the well-known least squares method is applied on the basis of only the linear correlation data. In the actual sound environment system, the stochastic process exhibits various non-Gaussian distributions, and there exist potentially various nonlinear correlations in addition to the linear correlation between input and output time series. Consequently, the system input and output relationship in the actual phenomenon cannot be represented by a simple model. In this study, a prediction method of output response probability for sound environment systems is derived by introducing a correction method based on the stochastic regression and fuzzy inference for simplified standard system models. The proposed method is applied to the actual data in a sound environment system, and the practical usefulness is verified. 相似文献
72.
S. Waheed N. Siddique J. H. Zaidi 《Journal of Radioanalytical and Nuclear Chemistry》2011,289(3):765-771
A proficiency test (PT) exercise was offered by the International Atomic Energy Agency (IAEA) for major, minor and trace elements
in Chinese ceramic reference material (IAEA-CU-2006-06). Neutron activation analysis (NAA) laboratory at PINSTECH, Pakistan
participated in the exercise and submitted the results for 28 elements. The aim of participation was to develop a suitable
methodology for accurate measurement of as many elements as possible in ceramic material using a low power reactor (PARR-2)
as this would help future investigation in a project on the authenticity of art objects, for provenance, conservation and
management of ancient cultural heritage of the country. After receiving the final report of the PT exercise, a critical review
of our data and final scoring of each element is made to check the suitability of our methodology and reliability of the acquired
data. Most of the reported results passed different statistical evaluation criterion such as relative bias, z-score and u-scores and ratio of our results and IAEA target values. One element (Yb) falls in the unacceptable range of relative bias
and z-scores. Hf and Tb showed slightly high z-scores within the questionable range. Ho, Mo and Sn were determined during this study but their results were not submitted
to the IAEA. The confidence of accuracy observed for most of the elements in ceramic material has made it mandatory to report
their results as information values. 相似文献
73.
N. Siddique A. Majid M. Tufail 《Journal of Radioanalytical and Nuclear Chemistry》2011,290(3):691-699
A study was undertaken to assess the air quality of Lahore by the elemental analysis of air conditioner (AC) filter dust samples
collected from 15 different commercial sites. Samples were prepared using the Leeds Public Analyst Method and were analyzed
using instrumental neutron activation analysis (INAA) for up to 31 elements. The elements Al, As, Ba, Ce, Co, Cr, Cs, Fe,
Hf, K, La, Lu, Mn, Na, Nd, Rb, Sc, Sm, Sn, Ta, Th, Yb and Zn were detected in all 15 samples whereas the remaining elements
have been detected in fewer samples; i.e. Mg, Sb and Tb were detected in 14 samples, Br and V in ten samples, U in nine samples
and Ca and Ti in eight samples only. Al, Ca, Fe, K, Mg and Na were determined in all samples at percentage levels. The concentrations
of most elements were found to lie around the mean values for the 15 samples studied and were not orders of magnitude different.
However the concentrations of Ca, Mg, Sn and Zn were found to be more variable and were found to be dependant on activities
such as construction, fruit and vegetable handling, tin plating and transport, respectively. 相似文献
74.
The ultrasonic velocity (U), has been measured for three α‐amino acids, namely L‐lysine monohydrochloride, L‐arginine and L‐histidine in solutions (1 mol/L aqueous) of sodium acetate (SA), potassium acetate (PA) and calcium acetate (CA) at different temperatures (303.15, 308.15, 313.15, 318.15 and 323.15 K). With the help of these results various ultrasonic derived parameters, viz. isentropic compressibility (κs), change in isentropic compressibility (Δκs), relative change in isentropic compressibility (Δκr), specific acoustic impedance (Z), relative association (RA), and apparent molal compressibility (?) have been estimated. The results have been interpreted in the light of intermolecular interactions between solute and solvent. 相似文献
75.
A facile, green, and efficient Fe(III) chloride, one-pot, multicomponent reaction (MCR) for synthesis of 2-aminothiazole-based compounds is reported. Considering the medicinal importance of fused ring 2-aminothiazoles, this process provides an easy route to the synthesis of this class of compound. Detailed mechanism of the reaction has been discussed. 相似文献
76.
77.
78.
M.J. Tait A.A. El Damatty N. Isyumov M.R. Siddique 《Journal of Fluids and Structures》2005,20(8):1007-1023
The tuned liquid damper (TLD) is increasingly being used as an economical and effective dynamic vibration absorber to mitigate the dynamic response of structures. In this paper the results of two numerical flow models of TLD behaviour are compared with experimental data. These include the free surface motion, the resulting base shear forces, and the energy dissipated by a TLD with slat screens. The importance of this experimental study is that it examines TLD behaviour over a large range of normalized excitation amplitude values, covering the practical range of serviceability accelerations for buildings subjected to wind loads and larger excitation amplitudes more representative of earthquake motion. In addition, the experimental results are used to assess the models for larger fluid depth to tank length values, and for the use of modelling TLDs equipped with multiple screens. For screens consisting of a number of thin plate slats, a method for determining the loss coefficient is presented, which is a required parameter for the models used in this paper. Findings indicate that the linear model is capable of providing an initial estimate of the energy dissipating characteristics of a TLD. The nonlinear model can accurately describe the response characteristics within the range of excitation amplitudes experimentally tested. 相似文献
79.
S. Waheed S. Rahman N. Siddique Y. Faiz 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(2):1453-1461
Eleven chelated calcium supplements intended for human consumption and produced by national and multinational companies have been studied for their mineral contents. Instrumental neutron activation analysis technique was used to quantify 12 elements (As, Br, Ce, Co, Cr, Fe, K, Na, Sb, Sn, Sr and Zn) while atomic absorption spectrometry technique quantified Cd, Cu and Ni. Three different irradiation protocols were adopted using a 27 kW tank-in-pool type miniature neutron source reactor. Most of the elements were present as minor or trace constituents except for Na that was quantified as major element in CaS-1 (3.73 %), CaS-2 (1.45 %), CaS-4 (1.56 %), CaS-5 (2.31 %), CaS-6 (1.84 %), CaS-7 (1.22), CaS-8 (1.73), CaS-9 (1.94), CaS-10 (2.07) and CaS-11 (2.48). However supplement CaS-3 with Ca source of calcium acetate contained only 53 μg/g of Na and the highest amount of Fe while As, Br, Cd and Sb were not detected in this sample. Percentage daily intakes with respect to their recommended dietary reference intake s and provisional tolerable daily intakes of essential and toxic elements showed that these elements contribute to a very low percentage of the recommended/tolerable levels for most of the supplements studied. Nevertheless the findings depict that it is very important for pharmaceutical and neutraceutical firms to completely identify these elements in the supplements and include their potency on the labels before being released to the consumers. 相似文献
80.
S. Waheed Y. Faiz S. Rahman N. Siddique 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(1):143-150
Geophagy of multani mitti (MM) clay is very common in central Pakistan especially amongst women. It was therefore mandatory to establish baseline levels of toxic elements in this clay for its safe dietary consumption by consumers of different genders, age groups and physical states. Instrumental neutron activation analysis and atomic absorption spectrometry techniques were used to determine the nutritional safety of MM clay for oral intake. All quantified toxic elements were detected at trace levels with composition in the descending order; Pb > Br > As > Sb > Hg > Cd. Comparison of these elements in MM clay with other clays shows that As, Cd, and Pb, are lowest in MM clay while its Br and Hg contents are high. Highest weekly dietary intakes of As, Br, Cd, Hg, and Sb were found to be 18, 0.05, 1.6, 9.2 and 1.1 % of the respective recommended provisional tolerable weekly intakes. The findings of this study show that As, Br, Cd, Hg and Sb in MM clay are well below the tolerance levels. However its Pb concentration is very high and may pose health concerns. The data presented in this study can be used as national base level guideline for geophagy of MM clay by men, women (normal, pregnant and lactating) and children. 相似文献