全文获取类型
收费全文 | 309篇 |
免费 | 11篇 |
国内免费 | 4篇 |
专业分类
化学 | 233篇 |
晶体学 | 6篇 |
力学 | 3篇 |
数学 | 32篇 |
物理学 | 50篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 25篇 |
2021年 | 31篇 |
2020年 | 17篇 |
2019年 | 14篇 |
2018年 | 14篇 |
2017年 | 9篇 |
2016年 | 17篇 |
2015年 | 20篇 |
2014年 | 5篇 |
2013年 | 19篇 |
2012年 | 6篇 |
2011年 | 19篇 |
2010年 | 10篇 |
2009年 | 7篇 |
2008年 | 9篇 |
2007年 | 9篇 |
2006年 | 8篇 |
2005年 | 12篇 |
2004年 | 7篇 |
2003年 | 8篇 |
2002年 | 8篇 |
2001年 | 5篇 |
1996年 | 2篇 |
1994年 | 1篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1972年 | 1篇 |
排序方式: 共有324条查询结果,搜索用时 0 毫秒
91.
A practical approach is presented for identifying the analyte peaks stacked by transient ITP (TITP) in samples of uncontrolled salinity. For TITP with chloride ions acting as the leading electrolyte, the effect of matrix chloride of an unknown concentration was calibrated using multiple internal standards to predict the migration times of weakly acidic anionic analytes behaving as strong electrolytes to an accuracy of over 99.9%. The calibration equations for the migration time of an analyte are given as a function of the migration times of internal standards using the mobilities of the relevant ions as parameters. The effects of matrix chloride and various separation conditions such as the temperature, plug length, ionic strength, and pH of the BGE were completely eliminated from the calibration equations. In addition, the actual mobilities, determined for a standard saline sample under the working conditions, were used, and thus, there was no need to conduct supplementary experiments to determine the absolute mobilities at infinite dilution. The internal standards were dyes, which were easily identified in an auxiliary channel monitoring the absorbance at a longer wavelength. For five standard saline matrices containing 100-300 mM NaCl at intervals of 50 mM, the mean absolute error (MAE) in migration times calibrated with two internal standards was 0.4 s (n=5x13). For an electropherogram of a real standard reference urine sample, peaks of spiked analytes were identified with an MAE of 0.9 s (n=13) without conductivity normalizing or desalting of the sample. 相似文献
92.
The objective of this investigation was to verify the degradation of endrin by gamma irradiation. 60Co was used as radiation source for irradiation of 50 mg L?1 endrin with a varied dose of 1–6 kGy. High performance liquid chromatography (HPLC) coupled with diode array detector was used as an analytical technique to monitor the degradation rate along with numbers of degradation products formed. At dose rate of 6 kGy ≥99% of endrin was degraded. It is proposed that utilization of ionization radiations can be an effective and efficient tool for the removal of halogenated pesticides. 相似文献
93.
Asad Ullah Saira Ahmad Milan Maric Syed Mujtaba Shah Hazrat Hussain 《Journal of polymer science. Part A, Polymer chemistry》2022,60(16):2488-2499
A low temperature ATRP of methacryloisobutyl POSS (POSS-MA) is carried out, using poly(propylene glycol) (PPG)-based macroinitiator, in toluene with CuCl/PMDETA as the catalyst system, generating well-defined P(POSS-MA)-b-PPG-b-P(POSS-MA) triblock copolymer with Ð ~ 1.1. The semilogarithmic kinetic plot reveals first-order kinetics and the dispersity is observed to decrease as the reaction progresses—an indication of the controlled behavior of the polymerization. To assess the chain-end fidelity of the produced block copolymer, chain extension is carried out with oligo(ethylene glycol methacrylate) (OEGMA) that afforded water-soluble P(OEGMA)-b-P(POSSMA)-b-PPG-b-P(POSSMA)-b-P(OEGMA) pentablock copolymers. The SEC profiles suggest a quantitative initiation by the macroinitiator. By varying the monomer to initiator molar ratio, block copolymers with various P(OEGMA) chain lengths, ranging from 19 to 58 units on each side have been achieved with relative lower dispersity (Ð < 1.4). Kinetic analysis of the ATRP of OEGMA, with P(POSSMA)-b-PPG-b-P(POSSMA) as the macroinitiator, suggests first-order kinetics and controlled nature of the polymerization. The PPG and P(OEGMA) segments impart a thermosensitive character to the obtained water-soluble amphiphilic hybrid block copolymers; hence they display temperature-dependent self-assembly behavior in aqueous medium. 相似文献
94.
M. Saleem Riaz Qadeer Javed Hanif M. Afzal 《Journal of Radioanalytical and Nuclear Chemistry》1994,182(2):415-419
The adsorption of metal ions such as Ce3+, Sm3+, Eu3+ and Gd3+ ions on activated charcoal has been studied as a function of pH. The adsorption mechanism of these ions is discussed in terms of hydrolyzed species formed in aqueous solution at different pH. 相似文献
95.
H. Wajahat A. Riaz 《理论物理通讯》2019,71(8):912-920
Using a quasideterminant Darboux matrix, we compute soliton solutions of a negative order AKNS (AKNS($-$1)) equation. Darboux transformation (DT) is defined on the solutions to the Lax pair and the AKNS($-$1) equation. By iterated DT to K-times, we obtain multisoliton solutions. It has been shown that multisoliton solutions can be expressed in terms of quasideterminants and shown to be related with the dressed solutions as obtained by dressing method. 相似文献
96.
Riaz A. Usmani 《BIT Numerical Mathematics》1977,17(2):227-234
A finite difference method for the numerical integration of the linear two-point boundary value problem $$y^{(4)} + f(x)y = g(x),y(a) = A_1 ,y(b) = A_2 ,y''(a) = B_1 ,y''(b) = B_2$$ is constructed and analyzed. The method usesf′,f″,g′,g″ at the boundary points to obtain anO(h 6) global error, while requiring only the solution of a system of linear equations associated with a five-band matrix. A typical numerical example is included to demonstrate the practical usefulness of the numerical procedure as well. 相似文献
97.
Simultaneous determination of nitrite and nitrate by normal phase ion-pair liquid chromatography 总被引:1,自引:0,他引:1
Normal phase ion-pair high performance liquid chromatography has been used for simultaneous separation of nitrite and nitrate using tetraethylammonium (TEA)(+) as ion-pairing reagent. The concentration effect of (TEA)(+), buffer salt and pH of the eluent on separation is investigated. The UV detector response at various wavelengths has been optimized. The performance of the proposed method is compared with ion chromatography for quantification of the anions in potable water, wastewater and in food samples, such as spinach and lettuce. 相似文献
98.
M. Saleem M. Afzal Javed Hanif Riaz Qadeer Imtiaz Hanif 《Journal of Radioanalytical and Nuclear Chemistry》1990,142(2):393-402
An XRF-method for the determination of Sm, Gd, Dy, Er and Eu in uranium solution by use of simple polyethylene bottles has been established. Spectral interferences and matrix effects like absorption enhancement have been rectified using standards of similar composition in the absence of internal standard. Analytical application of the method used has been established on the basis of statistical evaluation. 相似文献
99.
S. S.?Riaz S.?Dutta S.?Kar D. S.?RayEmail author 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,47(2):255-263
We analyze the condition for instability and pattern formation
induced by additive noise in spatially extended systems. The
approach is based on consideration of higher moments which
extract out nonlinearities of appropriate order. Our analysis
reveals that cubic nonlinearity plays a crucial role for the
additive noise to a leading order that determines the
instability threshold which is corroborated by numerical
simulation in two specific reaction-diffusion systems. 相似文献
100.
This paper is concerned with polynomial splines on a uniform mesh. Linear dependence relations connecting spline values (or derivatives) and integral values of the spline are developed. 相似文献