全文获取类型
收费全文 | 133篇 |
免费 | 3篇 |
国内免费 | 14篇 |
专业分类
化学 | 113篇 |
晶体学 | 8篇 |
力学 | 4篇 |
综合类 | 1篇 |
数学 | 4篇 |
物理学 | 20篇 |
出版年
2022年 | 1篇 |
2020年 | 2篇 |
2019年 | 6篇 |
2018年 | 2篇 |
2017年 | 4篇 |
2016年 | 7篇 |
2015年 | 4篇 |
2014年 | 10篇 |
2013年 | 18篇 |
2012年 | 7篇 |
2011年 | 6篇 |
2010年 | 7篇 |
2009年 | 8篇 |
2008年 | 6篇 |
2007年 | 8篇 |
2006年 | 10篇 |
2005年 | 8篇 |
2004年 | 7篇 |
2003年 | 10篇 |
2002年 | 1篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1985年 | 2篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有150条查询结果,搜索用时 15 毫秒
11.
《Green Chemistry Letters and Reviews》2013,6(3):281-287
Abstract Polyethylene glycol 400 (PEG 400) has been demonstrated as an efficient and eco-friendly reaction medium for the preparation of organic azides from structurally diverse halides by nucleophilic substitution reaction with NaN3 under mild conditions. The advantages of this protocol are: operational simplicity, environmental safety, broad substrate scope, excellent functional group tolerance, and short reaction time. The PEG 400 can be recovered and reused. 相似文献
12.
13.
《Comptes Rendus Chimie》2014,17(4):310-315
Submicron non-aqueous emulsions, of interest for biomedical and cosmetic formulations, were developed for the system comprising poly(ethylene glycol) (PEG) 400 and Miglyol 812, an enzymatic degradable liquid glycerine ester. These emulsions, with PEG 400 as continuous phase and Miglyol 812 droplets, in the size range of 200 nm, were stabilized by a poly(butadiene)-b-poly(2-vinylpyridine) (PBut-b-P2VP) block copolymer with a composition close to 50/50 wt%. The droplet size, stability and the rheological characteristics were examined as a function of the copolymer concentration. An original aspect of these anhydrous emulsions, with a water miscible continuous phase, is their water dispersibility without additional surfactant. In fact, the initial anhydrous emulsion is sterically stabilized and after water addition at low pH, the protonated P2VP sequence of the copolymer provides the electro-steric stabilization. This oil-in-water emulsion is characterized by sub micron sized Miglyol 812 droplets in an aqueous phase of PEG 400 and water at pH 1. 相似文献
14.
Satish Gaddam Harshavardhan Reddy Kasireddy Karnakar Konkala Ramesh Katla Nageswar Yadavalli Venkata Durga 《中国化学快报》2014,25(5):732-736
A simple and practical method for the synthesis of N-substituted-2-aminobenzothiazoles via a crosscoupling reaction of 2-iodo anilines with isothiocyanates is envisaged using nano copper oxide as a recyclable catalyst and Cs2CO3as a base in PEG-400,as a bio-degradable,reusable,inexpensive and nontoxic reaction medium,under ligand-free conditions.The present tandem process underlines environmental acceptability to access a wide range of N-substituted-2-aminobenzothiazoles in good to excellent yields. 相似文献
15.
A. Sibirtsev J. Haidenbauer H. -W. Hammer U. -G. Meißner 《The European Physical Journal A - Hadrons and Nuclei》2006,29(3):363-367
We show that the recently measured asymmetry in helicity-angle spectra of the Λ-hyperons, produced in the reaction pp → K
+Λp reaction, and the energy dependence of the total pp → K
+Λp cross-section can be explained consistently by the same Λp final-state interaction. Assuming that there is no final-state interaction in the Σ0
p channel, as suggested by the available data for the reaction pp → K
+Σ0
p, we can also reproduce the energy dependence of the Λ/Σ0 production ratio and, in particular, the rather large ratio observed near the reaction thresholds. The nominal ratio of the
Λ and Σ0 production amplitudes squared, i.e. when disregarding the final-state interaction, turns out to be about 3, which is in line with hyperon production data from
proton and nuclear targets available at high energies. 相似文献
16.
通过静态吸附试验,研究了强碱性树脂IRA-400对富马酸的吸附性能。结果表明,该树脂与弱碱性树脂IRA-94相比,受pH值影响较小,在pH=3.5时,该树脂对富马酸具有较好的吸附性能,其静态饱和吸附容量为1.466mmol/g湿树脂;该树脂对富马酸的吸附等温线符合Freundlich等温方程,在298.15K,308.15K和318.15K下的相关系数R2均大于0.99,方程的特征参数n1,属"优惠吸附";吸附过程ΔG0,ΔS0,ΔH0,表明此反应过程是放热的,自发进行的,降低温度有利于吸附反应的发生;吸附动力学研究表明,IRA-400树脂对富马酸的吸附过程主要受液膜扩散控制。 相似文献
17.
Vural E. Kafadar 《Physica B: Condensed Matter》2011,406(3):537-540
The dosimetric characteristics of many TL materials are influenced by changes in location, size and shape of the glow curves due to changes in the heating rate. In this study, the effect of heating rate on the integrated peak areas of CaF2:Dy (TLD-200), CaF2:Tm (TLD-300) and CaF2:Mn (TLD-400) crystals have been investigated after β-irradiation. It was observed that the peak temperatures of all peaks shifted to the high temperature sides and the integrated peak areas decrease as the heating rate increases due to thermal quenching, whose efficiency increases as temperature increases. 相似文献
18.
S.P. Avdeyev V.A. Karnaukhov W.D. Kuznetsov L.A. Petrov V.K. Rodionov A.S. Zubkevich H. Oeschler O.V. Bochkarev L.V. Chulkov E.A. Kuzmin A. Budzanovski W. Karcz M. Janicki E. Norbeck A.S. Botvina W.A. Friedman W. Nörenberg G. Papp 《The European Physical Journal A - Hadrons and Nuclei》1998,3(1):75-83
Multiple emission of intermediate-mass fragments has been studied for the collisions p + Au at 2.16, 3.6 and 8.1 GeV with
the FASA setup. The mean IMF multiplicities for events with at least one IMF are equal to 1.7, 1.9 and 2.1 (±0.2) respectively.
The multiplicity, charge distributions and kinetic energy spectra of IMF are described in the framework of a intranuclear
cascade model followed by the statistical multifragmentation model. However, between the two parts of the calculation the
excitation energies and the residual masses and charges are modified to take into account the losses during expansion. The
results support a scenario of true thermal multifragmentation of a hot and expanded target spectator.
Received: 15 December 1997 / Revised version: 24 April 1998 相似文献
19.
Diego AlvesMaraisa Sachini Raquel G. JacobEder J. Lenardão Maria E. ContreiraLucielli Savegnago Gelson Perin 《Tetrahedron letters》2011,52(1):133-135
PEG-400 and glycerol were successfully used as recyclable solvents for the synthesis of several organylthioenynes in good to excellent yields and high selectivity using solid supported catalyst (KF/Al2O3). This easy, general and improved method furnishes the corresponding alkenyl sulfides preferentially with Z configuration. The catalytic system and the glycerol or PEG-400 can be reused up to three times without previous treatment with comparable activity. 相似文献
20.
Methods for determining the heat content E
*/A of hot nuclei formed in energetic nuclear reactions are discussed. The primary factors involved in converting raw data into
thermal physics distributions include: 1) design of the detector array, 2) constraints imposed by the physics of the reaction
mechanism, and 3) assumptions involved in converting the filtered data into E
*/A. The two primary sources of uncertainty in the calorimetry are the elimination of nonequilibrium emissions from the event
components and accounting for the contribution of neutron emission to the excitation energy sum. 相似文献