全文获取类型
收费全文 | 759篇 |
免费 | 53篇 |
国内免费 | 3篇 |
专业分类
化学 | 659篇 |
晶体学 | 12篇 |
力学 | 6篇 |
数学 | 63篇 |
物理学 | 75篇 |
出版年
2023年 | 5篇 |
2022年 | 6篇 |
2021年 | 16篇 |
2020年 | 11篇 |
2019年 | 12篇 |
2018年 | 6篇 |
2017年 | 7篇 |
2016年 | 23篇 |
2015年 | 37篇 |
2014年 | 29篇 |
2013年 | 58篇 |
2012年 | 47篇 |
2011年 | 71篇 |
2010年 | 32篇 |
2009年 | 35篇 |
2008年 | 47篇 |
2007年 | 73篇 |
2006年 | 56篇 |
2005年 | 39篇 |
2004年 | 32篇 |
2003年 | 25篇 |
2002年 | 27篇 |
2001年 | 14篇 |
2000年 | 13篇 |
1999年 | 10篇 |
1998年 | 8篇 |
1997年 | 5篇 |
1996年 | 9篇 |
1995年 | 6篇 |
1994年 | 1篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有815条查询结果,搜索用时 15 毫秒
31.
Joaquin Barbera Mercedes Marcos Ana Omenat Jose-Luis Serrano Jesus I. Martinez Pablo J. Alonso 《Liquid crystals》2013,40(2):255-262
The synthesis and liquid crystalline behaviour of the first and second generations of a dendrimeric structure based on poly(propyleneimine)(DAB-dendr(NH2)x) are reported. 4-(4-n-Alkoxybenzoyloxy)salicylaldehydes are used as mesogenic moieties attached at the peripheral amino groups of the dendrimers giving rise to dendromesogens with four and eight mesogenic branches. From these dendromesogens, considered as organic ligands, were prepared six metal-containing dendrimers which incorporate two or four copper atoms in their structures. All the dendrimeric ligands and three of the metal-containing dendrimers exhibit liquid crystalline properties which were studied by optical microscopy, DSC, X-ray diffraction and EPR spectroscopy. 相似文献
32.
M. Parra Corresponding author J. Vergara C. Zúñiga E. Soto T. Sierra J. L. Serrano 《Liquid crystals》2013,40(4):457-462
Two new homologous series of chiral esters derived from Schiff's bases containing a 1,3,4‐thiadiazole unit (series 6 and 7) were synthesized and their liquid crystalline and ferroelectric properties investigated. All the compounds of series 6 exhibit SmC*–SmA dimorphism and the compounds of series 7 exhibit a SmC* phase. All the compounds of these series are ferroelectric liquid crystals. 相似文献
33.
M. Rosario De La Fuente Enrique Martín Miguel Ángel Pérez Jubindo Carmen Artal Blanca Ros José Luis Serrano 《Liquid crystals》2013,40(1):151-155
We present an achiral diacrylate that shows a phase transition from the synclinic smectic C phase (SmC) to the anticlinic smectic C (SmCalt). This last phase has been previously reported only for swallow-tailed or dimeric compounds. Our studies using differential scanning calorimetry, X-ray diffraction, polarizing optical microscopy and broad band dielectric spectroscopy suggest the existence of this mesophase in this bifunctional smectogen. 相似文献
34.
Eric Moore Nuria Sanvicens Miloslav Pravda George G. Guilbault 《International journal of environmental analytical chemistry》2013,93(7-8):545-553
This work is focused on the influence of pH and applied potential for the immobilisation of rabbit IgG on a carbon screen-printed electrode. The orientation of IgG molecule at the surface is fundamental for activity and reproducibility of the immunosensor. As the electrode potential is increased a particular order may be brought to the immobilised antibodies, i.e. the antibodies adapt a more favourable arrangement on the surface to facilitate better binding. The response increased when changing the pH from basic to acidic medium and the reverse trend was observed for the limit of detection (LOD). When a potential was applied to the electrode, the response generally decreased and the LOD increased in the order acidic > basic > neutral pH. The LODs obtained from antibodies immobilised at acidic pH and + 100 mV were better than the LODs obtained at other conditions. 相似文献
35.
Crispín Cristóbal Dr. Yohar A. Hernández Dr. Joaquín López‐Serrano Prof. Dr. Margarita Paneque Dr. Ana Petronilho Prof. Dr. Manuel L. Poveda Dr. Verónica Salazar Florencia Vattier Dr. Eleuterio Álvarez Dr. Celia Maya Prof. Dr. Ernesto Carmona 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(12):4003-4020
The reactivity of a series of iridium? pyridylidene complexes with the formula [TpMe2Ir(C6H5)2(C(CH)3C(R)N H] ( 1 a – 1 c ) towards a variety of substrates, from small molecules, such as H2, O2, carbon oxides, and formaldehyde, to alkenes and alkynes, is described. Most of the observed reactivity is best explained by invoking 16 e? unsaturated [TpMe2Ir(phenyl)(pyridyl)] intermediates, which behave as internal frustrated Lewis pairs (FLPs). H2 is heterolytically split to give hydride? pyridylidene complexes, whilst CO, CO2, and H2C?O provide carbonyl, carbonate, and alkoxide species, respectively. Ethylene and propene form five‐membered metallacycles with an IrCH2CH(R)N (R=H, Me) motif, whereas, in contrast, acetylene affords four‐membered iridacycles with the IrC(?CH2)N moiety. C6H5(C?O)H and C6H5C?CH react with formation of Ir? C6H5 and Ir? C?CPh bonds and the concomitant elimination of a molecule of pyridine and benzene, respectively. Finally the reactivity of compounds 1 a – 1 c against O2 is described. Density functional theory calculations that provide theoretical support for these experimental observations are also reported. 相似文献
36.
Adrián Serrano Mora Sean T. McBeath Clément A. Cid Michael R. Hoffmann Nigel J.D. Graham 《Current Opinion in Electrochemistry》2022
While diamond electrodes have been commonly used to generate ?OH to treat a variety of persistent water and wastewater micropollutants, mass transfer limitations and the non-selective, short-lived nature of the ?OH restrict the degradation to the solution at, or near, the electrode surface. However, diamond electrodes can generate oxidizing species that facilitate micropollutant degradation in the bulk water solution. These include persulfate, sulfate radicals, peroxodiphosphate, ferrate, permanganate, reactive chlorine species, hydrogen peroxide, and ozone, which have been reported during electrochemical treatment of water with diamond electrodes. Although still restricted to specialized applications, recent studies, summarized in this review, have proven the electrogeneration of these additional oxidant species to be effective. They have shown the adaptability and potential of diamond electrode-based water treatment to mitigate the presence of micropollutants in water. 相似文献
37.
A fast, simple and costless methodology without sample pre-treatment is proposed for the discrimination of beers. It is based on cyclic voltammetry (CV) using commercial carbon screen-printed electrodes (SPCE) and includes a correction of the signals measured with different SPCE units. Data are submitted to partial least squares discriminant analysis (PLS−DA) and support vector machine discriminant analysis (SVM−DA), which allow a reasonable classification of the beers. Also, CV data from beers can be used to predict their alcoholic degree by partial least squares (PLS) and artificial neural networks (ANN). In general, non-linear methods provide better results than linear ones. 相似文献
38.
If the baryon asymmetry of the Universe is produced by leptogenesis, CP violation is required in the lepton sector. In the seesaw extension of the standard model with three hierarchical right-handed neutrinos, we show that the baryon asymmetry is insensitive to the Pontecorvo-Maki-Nagakawa-Sakata phases: thermal leptogenesis can work for any value of the observable phases. This result was well known when there were no flavor effects in leptogenesis; we show that it remains true when flavor effects are included. 相似文献
39.
Voltammetric Determination of Pb(II) and Cd(II) Ions in Well Water Using a Sputtered Bismuth Screen‐Printed Electrode 下载免费PDF全文
Velia Sosa Núria Serrano Cristina Ariño José Manuel Díaz‐Cruz Miquel Esteban 《Electroanalysis》2014,26(10):2168-2172
A method using commercially available sputtered bismuth screen‐printed electrodes (BispSPE), as substitute to mercury electrodes, for the determination of trace Pb(II) and Cd(II) ions in drinking well water samples collected in a contaminated area in The Republic of El Salvador by means of differential pulse anodic stripping voltammetry (DPASV) has been proposed. The comparable detection and quantification limits obtained for both BispSPE and hanging mercury drop electrode (HMDE), together with the similar results with a high reproducibility obtained in these water samples analyses recommend the applicability of BispSPE for the determination of low level of metal concentrations in natural samples. 相似文献
40.