全文获取类型
收费全文 | 795篇 |
免费 | 14篇 |
专业分类
化学 | 666篇 |
晶体学 | 3篇 |
力学 | 7篇 |
数学 | 37篇 |
物理学 | 96篇 |
出版年
2023年 | 4篇 |
2022年 | 10篇 |
2021年 | 15篇 |
2020年 | 8篇 |
2019年 | 10篇 |
2018年 | 5篇 |
2017年 | 4篇 |
2016年 | 14篇 |
2015年 | 11篇 |
2014年 | 19篇 |
2013年 | 40篇 |
2012年 | 51篇 |
2011年 | 45篇 |
2010年 | 41篇 |
2009年 | 30篇 |
2008年 | 57篇 |
2007年 | 51篇 |
2006年 | 53篇 |
2005年 | 39篇 |
2004年 | 27篇 |
2003年 | 15篇 |
2002年 | 19篇 |
2001年 | 20篇 |
2000年 | 23篇 |
1999年 | 20篇 |
1998年 | 15篇 |
1997年 | 7篇 |
1996年 | 11篇 |
1995年 | 10篇 |
1994年 | 14篇 |
1993年 | 14篇 |
1992年 | 15篇 |
1991年 | 10篇 |
1990年 | 18篇 |
1989年 | 12篇 |
1988年 | 9篇 |
1987年 | 11篇 |
1986年 | 8篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1935年 | 2篇 |
排序方式: 共有809条查询结果,搜索用时 0 毫秒
101.
Chemical activation of carbon mesophase pitches 总被引:10,自引:0,他引:10
Mora E Blanco C Pajares JA Santamaría R Menéndez R 《Journal of colloid and interface science》2006,298(1):341-347
This paper studies the chemical activation of mesophase pitches of different origins in order to obtain activated carbons suitable for use as electrodes in supercapacitors. The effect that the activating agent (NaOH, LiOH, and KOH), the alkaline hydroxide/pitch ratio, and the activation temperature had on the characteristics of the resultant activated carbons was studied. LiOH was found to be a noneffective activating agent, while activation with NaOH and KOH yielded activated carbons with high apparent surface areas and pore volumes. The increase of the KOH/pitch ratio caused an increase of the chemical attack on the carbon, producing higher burnoffs and development of porosity. Extremely high apparent surface areas were obtained when the petroleum pitch was activated with 5:1 KOH/carbon ratio. The increase of the activation temperature caused an increase of the burnoff, although the differences were not as significant as those derived from the use of different proportions of activating agent. 相似文献
102.
103.
Vecchio Ciprioti Stefano Rotaru Andrei Blanco Ignazio Erceg Matko 《Journal of Thermal Analysis and Calorimetry》2020,142(5):1601-1604
Journal of Thermal Analysis and Calorimetry - 相似文献
104.
Alvarez-Puebla RA dos Santos DS Blanco C Echeverria JC Garrido JJ 《Journal of colloid and interface science》2005,285(1):41-49
Illite clays are known to have a strong affinity for metallic pollutants in the environment and can be applied as low-cost adsorbents for industrial waste treatment. A crucial factor in the development of such applications, however, is the understanding of the chemical, mineralogical, and colloidal properties of these clays. It is also important to understand the mechanisms involved in the surface adsorption of metals by these adsorbants. In order to study the retention of transition metals on illite clays, we have applied surface characterization techniques such as FPIA, SEM-EDX, XRD, N2 (77 K) adsorption, and FTIR. In addition to these experimental techniques, we have also employed a theoretical model that accounts for the chemistry of transition metal ions, and considers the global retention process to be the sum of several single retention processes. This model adequately fits the experimental data and allows for the speciation of metal retention on illite surfaces. Between pH values of 2.53 and 3.01 the only adsorption processes are the electrostatic sorption of [Cu(H2O)6]2+, and the surface complexation of [Cu(H2O)6]2+ and [Cu(OH)(H2O)5]+ ions. Surface complexation of [Cu(OH)(H2O)5]+ ions increases with pH, overcoming [Cu(H2O)6]2+ retention, and thus contributing to the surface precipitation of Cu(OH)2. 相似文献
105.
A. Viña Orjales M. I. Turnes Carou M. C. Prieto Blanco P. López Mahía S. Muniategui Lorenzo D. Prada Rodríguez 《Chromatographia》2000,51(1-2):77-82
Summary A systematic investigation of operational buffer systems, sample preparation and instrument parameters for achieving the best
possible performance for determinating an homologous series of N-benzyl-N-alkyl-N,N-dimethylammonium chloride compounds by
capillary zone electrophoresis with direct UV detection. The most effective separation was achieved within 3.5 min with the
addition of acetonitrile (40%) in a phosphate buffer (20 mM pH 5.2) using a 40 cm fused-silica capillary operating at 25 KV
and 20°C. Degassing of all electrolyte solutions and samples was very important. The linearity and repeatability for each
compounds were satisfactory. To improve detection limits, on-column sample preconcentration, sample stacking, was investigated
achieving a tenfold enrichment factor and quantitation limits about 10−7M. 相似文献
106.
Temperature measurements of shock heated materials using multispectral pyrometry: Application to bismuth 总被引:1,自引:0,他引:1
A new device for temperature measurements of shock heated materials has been developed in order to refine their equations
of state. We present temperature measurements for bismuth samples in contact with a lithium fluoride window. The shock pressure
of these experiments ranges from 18 to 97 GPa.
Received 2 June 1997 / Accepted 26 January 1998 相似文献
107.
The preparation of various (hex-5-ynyl)silanes was achieved following two different synthetic approaches from readily available materials such as 4-bromobutene, 6-iodohexyne and chlorosilanes. Different reaction conditions for intramolecular hydrosilylation were tested to prepare the corresponding 2-methylidene-1-silacyclohexanes. Notably, the use of Speier’s catalyst allowed the regioselective formation of the desired products in moderate yields. 相似文献
108.
The catalytic effect of various ions on the aerial oxidation of Co(II) when extracted from weakly acidic solutions with quinolin-8-ol in chlorofom was studied. Oxidation is complete only in the presence of Fe(III) or V(V). Mixtures of Al(III), Cu(II), Fe(III) and Ni(II) with Co(II) at concentrations in the range 1–8 μg ml?1 were analysed by using a multi-component analysis program involving first-order derivative spectra. Because of the metal ion interaction, a multivariate calibration process is required. The recovery factors achieved ranged from 93 to 111%. 相似文献
109.
Long-Distance Transmission at Zero Dispersion: Exact Expressions for One-Time Statistical Properties
We study the transmission of a signal through a dispersionless fiber with in-line amplifiers. The nonlinearities of the fiber and the noise generated at each amplifier are taken into account. Exact analytical expressions are obtained for the field averages. From these results we obtain the distributed amplification approximation, and study the conditions under which this approximation is valid. 相似文献
110.
Anserinones A and B are natural products that have been shown to have potential anticancer, antifungal, and antibacterial properties. This work entails the novel synthesis of these natural products. 相似文献