全文获取类型
收费全文 | 256篇 |
免费 | 9篇 |
专业分类
化学 | 233篇 |
力学 | 1篇 |
数学 | 9篇 |
物理学 | 22篇 |
出版年
2017年 | 1篇 |
2016年 | 7篇 |
2015年 | 2篇 |
2014年 | 8篇 |
2013年 | 4篇 |
2012年 | 13篇 |
2011年 | 20篇 |
2010年 | 11篇 |
2009年 | 13篇 |
2008年 | 21篇 |
2007年 | 15篇 |
2006年 | 32篇 |
2005年 | 27篇 |
2004年 | 16篇 |
2003年 | 9篇 |
2002年 | 8篇 |
2001年 | 3篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1996年 | 3篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1974年 | 1篇 |
1965年 | 2篇 |
1964年 | 2篇 |
1963年 | 2篇 |
1962年 | 1篇 |
1961年 | 1篇 |
1955年 | 1篇 |
1954年 | 1篇 |
1943年 | 1篇 |
1924年 | 1篇 |
1923年 | 1篇 |
1909年 | 1篇 |
排序方式: 共有265条查询结果,搜索用时 31 毫秒
241.
Ortegren J Wantke KD Motschmann H Möhwald H 《Journal of colloid and interface science》2004,279(1):266-276
The dilatational properties of fluid surfaces and interfaces have been comprehensively investigated in recent years. For example, an improved oscillating bubble device provided experimental results that allow for critical testing of established surface models, such as the Lucassen/van den Tempel (LvdT) model. The comparison of the LvdT model with the oscillating bubble experiments demonstrates a mismatch between the model parameters. For example, near the CMC or the limit of solubility the calculated parameters of surfactant solutions become unrealistically large. The deviation can be explained by the introduction of more detailed surface models, in particular by the modification of the effective thickness of the surface layer, its internal structure and the molecular exchange processes between these structures. For the verification of such processes an experimental setup was realized which allows for an independent determination of the instantaneous adsorption state at the surface of an oscillating bubble inside a surfactant solution. The setup utilizes the Second Harmonic Generation (SHG)--effect at the air-solution interface generated by the light of a pulsed LASER. The set-up is described in detail, and the results of a first experimental series are presented and discussed in this paper. As system, aqueous solutions of the fluortenside F381 were used. 相似文献
242.
Cordeiro AL Coelho M Sukhorukov GB Dubreuil F Möhwald H 《Journal of colloid and interface science》2004,280(1):68-75
A parallel plate flow chamber was implemented to study the deformation and adhesion of individual spherical hollow polyelectrolyte multilayered shells adhering to a coated surface. The device provides a well-defined laminar flow allowing the determination of the shear stress to which the capsules are being exposed up to 15 N/m(2). The results of the investigations indicate a strong dependence of the adhesion and mechanical resistance on the capsule size and wall thickness. Thin walled capsules, constituted of 8 polyelectrolyte layers (thickness congruent with 12 nm), are immediately deformed when exposed to flow while thick capsules, constituted of 16 layers (thickness congruent with 24 nm), of equal dimensions are detached from the surface for drag forces below 50 nN. It was observed that adhering capsules exposed to flow undergo an increase in their adhesion area in the direction of flow, resulting in rolling of the capsules. It was also found that the resistance of the capsules decreases after acetone treatment, indicating a weakening of the polyelectrolyte multilayer structure in the presence of this solvent. 相似文献
243.
Colonna S Ronci F Cricenti A Perfetti L Berger H Grioni M 《Physical review letters》2005,94(3):036405
In this Letter we report the observation, by scanning tunneling microscopy, of a Mott metal to insulator transition at the surface of 1T-TaSe2. Our spectroscopic data compare considerably well with previous angle-resolved photoemission spectroscopy measurements and confirm the presence of a large hysteresis related to a first order process. The local character of the tunneling spectroscopy technique allows a direct visualization of the surface symmetry and provides spectroscopic measurements on the defect-free region of the sample. It follows that the electronic localization is driven purely by the enhancement of the charge density wave amplitude which drives a bandwidth controlled metal-insulator transition. 相似文献
244.
245.
246.
Helmuth M. Gilow Christopher S. Brown John N. Copeland Keith E. Kelly 《Journal of heterocyclic chemistry》1991,28(4):1025-1034
Methylsulfenylation of 1-substituted pyrroles and indoles was observed using 1-(methylthio)morpholine and an acid catalyst or with methylsulfenyl chloride and excess pyridine. 1-Substituents which are activating or weakly deactivating towards electrophilic substitution such as alkyl, 2-cyanoethyl, dimethylamino, trialkylsilyl, 2-chloroethyl and 2-phenylsulfonylethyl were used. The 2-chloroethyl and 2-phenylsulfonylethyl groups which can be removed with a strong base can be used to obtain 1H-methylthiopyrroles and indoles. 1-Phenylsulfonyl and 1-acetyl substituents are too strongly deactivating for these sulfenylations to be successful. Mono and disubstituted pyrroles and monosubstituted indoles can be isolated from these reactions, however, because the methylthio group is activating towards electrophilic substitution the main advantage of these reactions is the synthesis of tri and tetrasubstituted pyrroles and disubstituted indoles. 1-Methyl-2,3,4,5-tetra-methylthiopyrrole and 1-methyl-2,3-dimethylthioindole are oxidized to the corresponding 3,4-disulfoxide and 3-sulfoxide and with excess oxidizing agent to the tetrasulfone and disulfone, respectively. 相似文献
247.
de Souza PP Augusti DV Catharino RR Siebald HG Eberlin MN Augusti R 《Journal of mass spectrometry : JMS》2007,42(10):1294-1299
Rum and cacha?a are sugarcane distillates produced on large scales and of similar composition, and their differentiation is currently a subject of commercial dispute and a challenging analytical task. We have investigated the ability of direct-infusion electrospray ionization mass spectrometry in the negative ion mode, i.e. ESI(-)-MS, to distinguish between samples of these distillates. ESI(-)-MS fingerprints were collected for some samples of Brazilian artisan cacha?a, aged in two types of wooden casks, i. e. amburana (Amburana cearensis) and jequitibá (Cariniana estrellensis), and of commercial rum. The mass spectra were found to be very distinctive, showing sets of diagnostic ions for each type of sample, i. e. (1) cacha?a aged in amburana (m/z 271, 313, 377) and jequitibá (m/z 171, 255, 455) casks; and (2) commercial rum (m/z 89, 97, 179, 255, 283). When applied to the ESI(-)-MS data, principal component analysis and hierarchical cluster analysis split rum and cacha?a samples into well-defined groups. Moreover, the two types of cacha?a samples aged in wooden casks of amburana or jequitibá were also split into two distinct groups. Direct-infusion ESI(-)-MS can therefore be potentially applied to the rapid, simple, and accurate differentiation of these commercially important sugarcane distillates. 相似文献
248.
Radziuk D Shchukin DG Skirtach A Möhwald H Sukhorukov G 《Langmuir : the ACS journal of surfaces and colloids》2007,23(8):4612-4617
Silver nanoparticles of 10, 18, and 23 nm were synthesized in aqueous medium by chemical reduction of silver nitrate in excess of sodium borohydride. Modification of polyelectrolyte shells with synthesized silver nanoparticles was performed using the layer-by-layer approach. Remote opening of the polyelectrolyte/silver capsules was performed with a CW Nd:YAG FD laser with an average incident power output up to 70 mW. Capsules with a mixture of 10 and 18 nm silver nanoparticles in its polyelectrolyte shell were ruptured after less than 7 s of laser irradiation, while microcapsules with 23 nm silver nanoparticles in the shell were broken after 11 s of laser treatment and 10 nm silver nanoparticles were broken after 26 s. 相似文献
249.
250.
Schneider J Pflieger R Nikitenko SI Shchukin D Möhwald H 《The journal of physical chemistry. A》2011,115(2):136-140
Spectroscopic studies of single-bubble sonoluminescence (SBSL) in water and aqueous sodium chloride solutions with a defined concentration of argon were performed as a function of the driving acoustic pressure. The broad-band continuum ranging from 200 to 700 nm is characterized by fits using Planck's law of blackbody radiation. The obtained blackbody temperatures are in the range of 10(4) K and are revealed to be independent of the presence of a salt and the acoustic pressure, whereas the SL intensity increases by a factor of more than 10 within the studied acoustic pressure range. The different trends followed by SL intensity and blackbody temperatures question the blackbody model. In solutions with 70 mbar of argon, line emissions of OH(?) radicals and Na* are observed. The shape of the OH(?) radical emission spectrum is very similar to that in MBSL spectra, indicating the strong similarity of intrabubble conditions. An increase of the acoustic pressure causes the continuum to overlap the lines until they become indistinguishable. The emission line of Na* in NaCl is observed only at high NaCl concentrations. When sodium dodecylsulfate is used a pronounced Na* line is already observed in a 1 mM solution thanks to enrichment of sodium ions at the interface. The results presented in this work reveal the strong similarity of SBSL and MBSL under certain experimental conditions. 相似文献