全文获取类型
收费全文 | 1966篇 |
免费 | 53篇 |
国内免费 | 106篇 |
专业分类
化学 | 1635篇 |
晶体学 | 19篇 |
力学 | 4篇 |
综合类 | 6篇 |
数学 | 3篇 |
物理学 | 458篇 |
出版年
2024年 | 6篇 |
2023年 | 29篇 |
2022年 | 32篇 |
2021年 | 44篇 |
2020年 | 53篇 |
2019年 | 33篇 |
2018年 | 32篇 |
2017年 | 43篇 |
2016年 | 71篇 |
2015年 | 61篇 |
2014年 | 57篇 |
2013年 | 95篇 |
2012年 | 101篇 |
2011年 | 116篇 |
2010年 | 110篇 |
2009年 | 112篇 |
2008年 | 107篇 |
2007年 | 104篇 |
2006年 | 101篇 |
2005年 | 123篇 |
2004年 | 86篇 |
2003年 | 69篇 |
2002年 | 61篇 |
2001年 | 53篇 |
2000年 | 26篇 |
1999年 | 58篇 |
1998年 | 31篇 |
1997年 | 60篇 |
1996年 | 46篇 |
1995年 | 25篇 |
1994年 | 31篇 |
1993年 | 16篇 |
1992年 | 25篇 |
1991年 | 13篇 |
1990年 | 11篇 |
1989年 | 9篇 |
1988年 | 17篇 |
1986年 | 9篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1972年 | 2篇 |
排序方式: 共有2125条查询结果,搜索用时 15 毫秒
991.
992.
993.
《Journal of Saudi Chemical Society》2019,23(8):1070-1079
A new metal-organic framework compound formulated as [Co0.67Zn0.83(btc)(H2O)6] (1) was prepared and characterized by elemental analysis, and FT-IR spectroscopy. The single crystal analysis was used for determination of its structure. The complex was used for the preparation of two inorganic precursors [Co0.67Zn0.83(btc)(H2O)6]/SiO2 and [Co0.67Zn0.83(btc)(H2O)6]/Al2O3, which were thermally decomposed to obtain new Co-Zn alloy catalysts for Fischer-Tropsch synthesis. The same catalysts were prepared by the conventional impregnation method as reference catalysts. The catalysts were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and BET specific surface area, and their catalytic performances were studied in the temperature range 200–300 °C and P = 5 bar. The results show that the Co-Zn synthesized alloy catalysts have acceptable activity in the Fischer-Tropsch (FTS) synthesis and have better selectivity to desired products than reference catalysts. The difference between the Co-Zn alloy catalysts and the reference catalysts is mainly caused by their different particle size. 相似文献
994.
Clémentine Symonds Joel Bellessa Jean-Claude Plenet Edmond Cambril Audrey Miard Laurence Ferlazzo Aristide Lemaître 《Superlattices and Microstructures》2010
We report on the strong coupling between surface plasmons and inorganic quantum well excitons. The sample is formed by a corrugated silver film deposited on the top of a heterostructure consisting of five GaAs/GaAlAs quantum wells grown by molecular beam epitaxy. Reflectometry experiments at low temperature (77 K) evidence the formation of plasmon/heavy-hole exciton/light-hole exciton mixed states. The interaction energies, deduced by fitting the experimental data with a coupled oscillator model, amount to 22 meV for the plasmon/light-hole exciton and 21 meV for the plasmon/heavy-hole exciton. Some particularities of the plasmon–exciton coupling are also discussed and qualitatively related to the plasmon polarization. 相似文献
995.
The practical application of rigid, macro-porous organic polymer and silica based monolithic stationary phases as separation media has been described in the literature since 1992 and 1996, respectively. Today these materials are extensively used in chromatography and electrochromatography and several detailed reviews appear annually describing these materials, their synthesis and application. To compliment these publications, this review focuses upon the less commonly utilised materials for monolith synthesis, both those that have already been applied within separation science, and those that have found applications elsewhere, such as catalysis and water filtration, but have the clear potential to be explored as novel stationary phases in the near future. For the purpose of the review monoliths formed from these various alternative materials will be termed ‘Exotic Monoliths’, as these new substrates in many cases have only just begun to be explored for chromatographic separations, and in many instances have unusual and highly selective surface chemistries, which are attractive in terms of broadening the choice of monolithic materials for separation science. An extensive range of monolithic materials based on the following elements and their compounds (mostly oxides) are covered: Zr, Ti, Al, Hf, C, Au, Ag, Ce, Ge and hydroxyapatite, together with their relevant properties, methods of synthesis, and current and potential applications in separation science. 相似文献
996.
《Analytical letters》2012,45(15):2701-2712
Abstract Arsenic (III), arsenic (V), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) were separated by ion-exchange chromatography. The elution sequence was as follows: 1.5 M ammonia followed by 0.12 M hydrochloric acid yielding As(III) 1 M hydrochloric acid followed by water yielding first As(V) and then MMA. Detection was by hydride generation-atomic absorption spectrometry. No interference was noted from 13 metallic ions. The method provides a good linearity, precision, accuracy, and sensitivity. It has been applied to the speciation of arsenic in seawaters from the North West coast of Spain (1200 Km). 相似文献
997.
《Analytical letters》2012,45(2):105-110
Abstract A direct and simple method for arsenic in organic compounds involves merely dissolution of the sample in an organic solvent, such as benzene, cyclohexane, or methyl isobutyl ketone, and direct aspiration into a fuel-rich acetylene-oxygen flame. The arsenic line at 2350 Å is used; the detection limit is 2.2 ü/ml. From iron and copper matrices arsenic is isolated by extraction from a solution 9 M in HCI and 0.25 M in KI with benzene. 相似文献
998.
《Analytical letters》2012,45(2):123-128
Abstract An automated system for the determination of arsenic, selenium, antimony, bismuth and tin is described. These elements and their compounds are reduced with sodium borohydride to the corresponding hydride. Sensitivity of the automated system is comparable and in most cases better than the manual technique. The automated method was found superior to the manual with respect to reproducibility and ease of operation. 相似文献
999.
《Analytical letters》2012,45(3):406-416
Abstract An analytical method using microwave digestion and inductively coupled argon plasma-mass spectrometry (ICP‐MS) analysis was developed for the measurement of Cd, Hg, Pb, As, Cu, and Zn in human breast milk. We applied external calibration, internal calibration, and standard addition for reference material and pooled milk analysis. Method performances were defined in terms of detection limits, accuracy, and precision. Accuracy varied between 93% and 105% and precision between 3% and 8%. External calibration and background interferences were checked through a calibrator addition procedure. Our method has shown high accuracy, precision, and sensitivity, as well as linearity within a wide range of values. Our methodology, developed by treatment of reference material and pooled milk samples, was applied for determination of Cu, Zn, As, Cd, Hg, and Pb in 120 human breast milk samples. 相似文献
1000.
《Journal of Coordination Chemistry》2012,65(7):719-732
Two new inorganic–organic hybrid cobalt phosphomolybdates (Hdien)2[Co(dien)]2[Co(dien)(H2O)]2[CoMo12O24(HPO4)2(H2PO4)2(PO4)4(OH)6]?···?5H2O (1) and (H2dien)2[Co(dien)]2[Co(H2O)2]2[CoMo12O24(HPO4)4(PO4)4(OH)6]?···?7H2O (2) (dien?=?diethylenetriamine), involving molybdenum in the V oxidation state and covalently bonded transition metal complexes, have been prepared under mild hydrothermal conditions and structurally characterized by elemental analyses, IR spectra, TG analyses, and single-crystal X-ray diffraction. Compound 1 exhibits a one-dimensional (1D) chain framework, in which dien molecules adopt two kinds of coordination modes. Compound 2 shows a two-dimensional (2D) layer framework with three types of unusual tunnels. To the best of our knowledge, it is the first time [Co(dien)] units are directly incorporated into 1D and 2D skeletons of reduced molybdenum phosphates. The electrochemical properties of the two compounds were studied via the method of bulk-modified carbon paste electrodes. Furthermore, the magnetic properties of compound 2 are reported. 相似文献