全文获取类型
收费全文 | 1352篇 |
免费 | 49篇 |
国内免费 | 104篇 |
专业分类
化学 | 910篇 |
晶体学 | 42篇 |
力学 | 4篇 |
综合类 | 1篇 |
数学 | 1篇 |
物理学 | 547篇 |
出版年
2024年 | 1篇 |
2023年 | 28篇 |
2022年 | 21篇 |
2021年 | 23篇 |
2020年 | 33篇 |
2019年 | 12篇 |
2018年 | 18篇 |
2017年 | 30篇 |
2016年 | 61篇 |
2015年 | 40篇 |
2014年 | 45篇 |
2013年 | 40篇 |
2012年 | 70篇 |
2011年 | 99篇 |
2010年 | 104篇 |
2009年 | 100篇 |
2008年 | 89篇 |
2007年 | 82篇 |
2006年 | 85篇 |
2005年 | 83篇 |
2004年 | 62篇 |
2003年 | 39篇 |
2002年 | 42篇 |
2001年 | 48篇 |
2000年 | 18篇 |
1999年 | 49篇 |
1998年 | 15篇 |
1997年 | 34篇 |
1996年 | 25篇 |
1995年 | 8篇 |
1994年 | 13篇 |
1993年 | 10篇 |
1992年 | 4篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 7篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 9篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1972年 | 1篇 |
排序方式: 共有1505条查询结果,搜索用时 15 毫秒
31.
Hui Jin Yan-bing Hou Xian-guo Meng Feng Teng 《高分子科学》2006,(6):553-558
In this paper, photoexcitation processes in the bilayer devices based on inorganic materials and poly(N-vinylcarbazole) (PVK) were investigated. In order to clarify the roles of inorganic materials in photoconductive properties of bilayer devices, TiO2 and ZnS were chosen to combine with PVK. A model for generation of photocurrent (Iph) in single layer device of PVK was obtained. It is deduced that the recombination rate constant (Pcomb) and the ionization rate constant (y) ofexcitons should be considered as the most important factors for Iph. For inorganic materials (TiO2 or ZnS)/PVK bilayer devices, in reverse bias of-4 V, the photocurrent of 115 mA/cm^2 in the TiO2/PVK device was observed, but the photocurrent in the ZnS/PVK device was only 10 mA/cma under the illumination light of 340 nm and the light intensity of 14.2 mW/cm^2. The weaker photocurrent is attributed to the absorption of ZnS within UV region and the energy offset at the interface between PVK and ZnS, which impedes the transport of charge carriers. 相似文献
32.
CHARACTERIZATIONOFRADIATIONGRAFTCOPOLYMEROFINORGANICCOMPOUNDONTOALKENEZhangWanxi;CheJitai;YanMeilan(ChangchuninstituteofAppli... 相似文献
33.
Different stationary phases were prepared by mixing a series of inorganic salts with dimethylsiloxane polymer (SE-30) and then tested by capillary gas chromatography. It was demonstrated that the polarity (as evaluated by measurement of Rohrschneider constants) of the mixed stationary phases, which is inferior or equal to that of a medium-polar OV-25 phases, reached even lower values than SE-30 alone. The influence of NaF, NaCl, NaBr, AgNO3, and other inorganic salts on the polarity of capillaries is reflected by a better resolution and shorter retention time of cis/trans isomers of fatty acid methyl esters (FAMES) as well as positional isomers of triglycerides. 相似文献
34.
Kim WS Park M Lee DW Moon MH Lim H Lee S 《Analytical and bioanalytical chemistry》2004,378(3):746-752
Fly ash has been regarded as hazardous because of its high adsorption of toxic organic and/or inorganic pollutants. Fly ash is also known to have broad distributions of different chemical and physical properties, such as size and density. In this study, fly ash emitted from a solid waste incinerator was pre-fractionated into six sub-populations by use of gravitational SPLITT fractionation (GSF). The GSF fractions were then analyzed by sedimentation field-flow fractionation (SdFFF) and ICP–AES. SdFFF analysis showed the fly ash has a broad size distribution ranging from a few nanometers up to about 50 µm. SdFFF results were confirmed by electron microscopy. Inductively coupled plasma–atomic emission spectroscopy (ICP–AES) analysis of the GSF fractions showed the fly-ash particles contain a variety of inorganic elements including Ca, Si, Mg, Fe, and Pb. The most abundant in fly ash was Ca, followed by Si then Mg. No correlations were found between trace element concentration and particle size. 相似文献
35.
Maria Concetta Bruzzoniti Edoardo Mentasti Corrado Sarzanini Peter Hajs 《Journal of chromatography. A》1997,770(1-2):13-22
The retention behavior of biologically relevant monovalent (formic, acetic, propionic, lactic and pyruvic) and divalent (oxalic, malonic, succinic, fumaric, maleic and tartaric acids) car☐ylic acids together with inorganic analytes (chloride and sulphate) has been studied. The separation was performed on a latex-based strong anion-exchange resin using carbonate buffer systems in suppressed IC. The retention behaviour of analytes was investigated at different pH values and [HCO3−]+[CO32−] concentrations. A theoretical model, involving ion-exchange equilibria of sample and eluent anions, was derived and applied to the chromatographic data obtained. Chromatographic ion exchange selectivity values were determined and retention data were calculated for the anions using different carbonate eluent conditions. The average of errors between the predicted and the measured retention volumes of the analytes studied does not exceed 4.0%. The study effectively characteristics the behaviour of different analytes under elution conditions of practical importance. 相似文献
36.
Zn3V3O8 two-dimensional micro sheets are successfully synthesized by combination of solvothermal method and heat treatment. The Zn3V3O8 has better electrochemical performances after calcinations. 相似文献
37.
Glycerol of different quality classifications served as a model for a neutral excess component in the isotachophoretic determination of low-molecular-mass anionic trace impurities. Potential anionic contaminants such as nitrate, sulphate, chlorate, nitrite, oxalate, fluoride formate and phosphate were analysed up to an analyte-to-excess ratio of 1:4·107, thus providing the possibility of checking the sample for the mentioned analytes in the order of 2.5·10−6–9.5·10−6%. Because we used a column-coupling isotachophoretic instrument the electrolyte system consisted of two different leading electrolytes, one for the pre-separation (10 mmol/l HCl, β-alanine, pH 3.2) in the first capillary and one for the final separation (5 mmol/l HCl, 1,3-bis[tris(hydroxymethyl)methylamino]propane, β-alanine, pH 3.6) in the second capillary. The terminating electrolyte was citric acid. Due to an increased injection volume of 300 μl, limits of detection (LODs) in the nanomolar range were realised by conductivity detection. The developed method allows simultaneous analysis without sample preparation and/or preconcentration within 25 min and is for that reason suitable for in-place process control. 相似文献
38.
Summary A miniaturized flow cell for an electrical conductivity detector has been made and applied to the ion chromatography of inorganic anions. It consisted of stainless steel tubes (0.13 mm ID×0.31 mm OD) and PTFE tubes (0.25 mm ID×2 mm OD). The detection limit for chloride at S/N=3 was 36 pg or 0.33 ppm for a 0.11 l injection. 相似文献
39.
A review is presented detailing the development and use of suppression devices for the conductimetric detection of inorganic ions by ion chromatography (IC). An overview of the general response equation for conductivity detection is also given. Topics of discussion include the role and function of suppressors, the development of early suppressors including packed column and membrane devices from 1975 to 1990 and the subsequent progression towards present day commercially available suppressors and recent innovations. Post-suppression devices for signal enhancement are also discussed. 相似文献
40.
Speciation of inorganic arsenic by electrochemical hydride generation atomic absorption spectrometry 总被引:11,自引:0,他引:11
A simple procedure was developed for the speciation of inorganic arsenic by electrochemical hydride generation atomic absorption spectrometry (EcHG–AAS), without pre-reduction of As(V). Glassy carbon was selected as cathode material in the flow cell. An optimum catholyte concentration for simultaneous generation of arsine from As(III) and As(V) was 0.06 mol l−1 H2SO4. Under the optimized conditions, adequate sensitivity and difference in ratio of slopes of the calibration curves for As(III) and As(V) can be achieved at the electrolytic currents of 0.6 and 1 A. The speciation of inorganic arsenic can be performed by controlling the electrolytic currents, and the concentration of As(III) and As(V) in the sample can be calculated according to the equations of absorbance additivity obtained at two selected electrolytic currents. The calibration curves were linear up to 50 ng ml−1 for both As(III) and As(V) at 0.6 and 1 A. The detection limits of the method were 0.2 and 0.5 ng ml−1 for As(III) and As(V) at 0.6 A, respectively. The relative standard deviations were of 2.1% for 20 ng ml−1 As(III) and 2.5% for 20 ng ml−1 As(V). The method was validated by the analysis of human hair certified reference material and successfully applied to speciation of soluble inorganic arsenic in Chinese medicine. 相似文献