全文获取类型
收费全文 | 215篇 |
免费 | 5篇 |
专业分类
化学 | 152篇 |
晶体学 | 3篇 |
力学 | 6篇 |
数学 | 24篇 |
物理学 | 35篇 |
出版年
2022年 | 3篇 |
2021年 | 5篇 |
2018年 | 5篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 5篇 |
2014年 | 6篇 |
2013年 | 9篇 |
2012年 | 10篇 |
2011年 | 17篇 |
2010年 | 12篇 |
2009年 | 12篇 |
2008年 | 18篇 |
2007年 | 11篇 |
2006年 | 13篇 |
2005年 | 14篇 |
2004年 | 15篇 |
2003年 | 7篇 |
2002年 | 8篇 |
2001年 | 5篇 |
2000年 | 1篇 |
1998年 | 3篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 4篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1972年 | 1篇 |
排序方式: 共有220条查询结果,搜索用时 31 毫秒
81.
The mechanical behavior of Zr-based bulk amorphous alloy composites (BAACs) was investigated at 77 K. The 5 vol. % Ta-BAAC maintained large plastic strains of approximately 13% with a 16% strength increase, when compared with that at 298 K. The interaction between shear bands and particles shows that shear extension in particles has limited penetration, and shear bands build up around particles. In addition to on the failure surface of the amorphous matrix, molten characteristics were also found on the surface of sheared particles. Pair distribution function studies were performed to understand the mechanical behavior. 相似文献
82.
Potassium iodide-mediated radical sulfonylation/1,2-carbon migration sequences of alkenylcyclobutanols has been developed. The reaction was effectively accelerated using potassium iodide as a catalyst under mild reaction conditions without other metal oxidant. This approach is environmentally benign by use of shelf-stable arylsulfonyl hydrazides as arylsulfonyl radical precursor and water as solvent. This approach offers a facile way to prepare β-sulfonated cyclic ketone derivatives. 相似文献
83.
Janus Graft Block Copolymers: Design of a Polymer Architecture for Independently Tuned Nanostructures and Polymer Properties
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Zi‐Hao Guo An N. Le Dr. Xunda Feng Youngwoo Choo Bingqian Liu Danyu Wang Zhengyi Wan Yuwei Gu Julia Zhao Vince Li Prof. Chinedum O. Osuji Prof. Jeremiah A. Johnson Prof. Mingjiang Zhong 《Angewandte Chemie (International ed. in English)》2018,57(28):8493-8497
The graft‐through synthesis of Janus graft block copolymers (GBCPs) from branched macromonomers composed of various combinations of homopolymers is presented. Self‐assembly of GBCPs resulted in ordered nanostructures with ultra‐small domain sizes down to 2.8 nm (half‐pitch). The grafted architecture introduces an additional parameter, the backbone length, which enables control over the thermomechanical properties and processability of the GBCPs independently of their self‐assembled nanostructures. The simple synthetic route to GBCPs and the possibility of using a variety of polymer combinations contribute to the universality of this technique. 相似文献
84.
The effect on overall waiting time including service is investigated when there is positive correlation between the first and second stage service times in a two stage tandem system. The importance of understage waiting (or “buffer”) space is underlined. The analysis is an application of the authors' work reported in [1]. 相似文献
85.
86.
The Shubnikov-de Haas (S-dH) results at 1.5 K for AlxGa1−xN/AlN/GaN heterostructures and the fast Fourier transformation data for the S-dH data indicated the occupation by a two-dimensional electron gas (2DEG) of one subband in the GaN active layer. Photoluminescence (PL) spectra showed a broad PL emission about 30 meV below the GaN exciton emission peak at 3.474 eV that could be attributed to recombination between the 2DEG occupying in the AlN/GaN heterointerface and photoexcited holes. A possible subband structure was calculated by a self-consistent method taking into account the spontaneous and piezoelectric polarizations, and one subband was occupied by 2DEG below the Fermi level, which was in reasonable agreement with the S-dH results. These results can help improve understanding of magnetotransport, optical, and electronic subband properties in AlxGa1−xAs/AlN/GaN heterostructures. 相似文献
87.
Transmission electron microscopy (TEM) and photocurrent (PC) measurements were carried out to investigate the microstructural and excitonic transitions in In0.52Ga0.48As/In0.55Al0.45As multiple quantum wells (MQWs). TEM images showed that high-quality 11-period strain-compensated In0.52Ga0.48As/In0.55Al0.45As MQWs had high-quality heterointerfaces. Based on the TEM results, a possible crystal structure for the In0.52Ga0.48As/In0.55Al0.45As MQWs is presented, and their strains are compensated. The results for the PC data at 300 K for several applied electric fields showed that several excitonic transitions shifted to longer wavelengths as the applied electric field increased. These results indicate that the strain-compensated In0.52Ga0.48As/In0.55Al0.45As MQWs hold promise for electroabsorption modulator devices. 相似文献
88.
The self-consistent reaction field (SCRF) method based on Onsager's reaction field theory is applied to investigate the effect of polar media on molecular structures of complexes of trimethylamime (TMA) with SOx (x=2,3). The calculated SCRF N–S bond lengths at the MPW1PW91/6-311+G(3df) level are in satisfactory agreement with the experimental N–S bond lengths for the TMA–SOx upon crystallization. The results are enough to demonstrate the usefulness of the reaction field theory in providing qualitative understanding of the medium effect on the partially bonded system such as TMA–SOx. 相似文献
89.
A new counterion-buffered molybdate electrolyte was developed and optimized for simultaneous quantitative determination of up to eight anions (chloride, sulphate, oxalate, fluoride, formate, malonate, succinate, and acetate) in Bayer liquor by capillary electrophoresis with indirect detection at 214 nm. The separation parameters were optimized in respect to separation of the critical analyte group fluoride-formate-malonate, with the optimal electrolyte prepared from molybdic trioxide containing 5.0 mmol/L MoO3, 1.3 mmol/L cetyltrimethylammonium bromide (CTAB), and buffered with diethanolamine (DEA) to pH 9.2 (ca. 20 mM DEA). Total length of separation capillary was 80 cm, resulting in run time of under 4 min. The method is suitable for a wide concentration range of the analytes (1-50 mg/L) with linear calibration plots (R2 = 0.9983-0.9999). Relative standard deviations were 0.05%-0.07% for migration times and 0.67%-2.04% for peak areas. The detection limits were in the range of 0.17-0.51 mg/L or 2-10 micromol/L (hydrostatic injection of 30 s of 1000 x diluted sample). Due to its good buffering capacity, the electrolyte exhibited an excellent ruggedness and good tolerance to the alkaline samples. Consequently, Bayer liquor samples could be diluted as little as 100 x which allows more sensitive determination of minor components over previous methods. The method was successfully applied to analysis of Bayer liquor samples with recoveries in the range of 95-105%. 相似文献
90.
Effect of chlorine on adsorption/ultrafiltration treatment for removing natural organic matter in drinking water 总被引:4,自引:0,他引:4
In drinking water treatment, prechlorination is often applied in order to control microorganisms and taste-and-odor-causing materials, which may influence organics removal by adsorption and membrane filtration. Thus, the addition of chlorine into an advanced water treatment process using a hybrid of adsorption and ultrafiltration (UF) was investigated in terms of natural organic matter (NOM) removal and membrane permeability. A comparison between two adsorbents, iron oxide particles (IOP) and powdered activated carbon (PAC), was made to understand the sorption behavior for NOM with and without chlorination. Chlorine modified the properties of dissolved and colloidal NOM in raw water, which brought about lower TOC removal, during IOP/UF. The location of IOPs, whether they were in suspension or in a cake layer, affected NOM removal, depending on the presence of colloidal particles in feedwater. Chlorine also played a role in reducing the size of particulate matter in raw water, which could be in close association with a decline in permeate flux after chlorination. 相似文献