全文获取类型
收费全文 | 265篇 |
免费 | 8篇 |
专业分类
化学 | 181篇 |
晶体学 | 8篇 |
力学 | 18篇 |
数学 | 9篇 |
物理学 | 57篇 |
出版年
2023年 | 2篇 |
2022年 | 8篇 |
2021年 | 6篇 |
2020年 | 13篇 |
2019年 | 7篇 |
2018年 | 8篇 |
2017年 | 6篇 |
2016年 | 6篇 |
2015年 | 9篇 |
2014年 | 13篇 |
2013年 | 23篇 |
2012年 | 19篇 |
2011年 | 29篇 |
2010年 | 16篇 |
2009年 | 19篇 |
2008年 | 14篇 |
2007年 | 15篇 |
2006年 | 13篇 |
2005年 | 8篇 |
2004年 | 11篇 |
2003年 | 12篇 |
2002年 | 8篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 3篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有273条查询结果,搜索用时 19 毫秒
21.
Research on Chemical Intermediates - Caryota urens seeds are an agro-based material that can be used as an eco-friendly and low cost adsorbent for the removal of metal ions. In the present study,... 相似文献
22.
Magnetic metal and metal oxide nanoparticles capped with alkylamines have been synthesized and characterized by transmission
electron microscopy. X-ray diffraction, energy dispersive X-ray analysis and magnetization measurements. Core-shell Pd-Ni
particles with composition, Pd561Ni3000, (diameter ∼3.3 nm) are superparamagnetic at 5 K and organize themselves into two-dimensional crystalline arrays. Similar
arrays are obtained with Pd561Ni3000Pd1500 nanoparticles containing an additional Pd shell. Magnetic spinel particles of γ-Fe2O3, Fe3O4 and CoFe2O4 of average diameters in the 4–6 nm range coated with octylamine are all supermagnetic at room temperature and yield close-packed
disordered arrays. Relatively regular arrays are formed by dodecylaminecapped Fe3O4 nanoparticles (∼8.6 nm diameter) while well-ordered hexagonal arrays were obtained with octylamine-covered Co3O4 nanoparticles (∼4.2 nm diameter). 相似文献
23.
[reaction: see text] Syntheses of two novel omuralide derivatives are described. 相似文献
24.
Saravanan C Shao Y Baer R Ross PN Head-Gordon M 《Journal of computational chemistry》2003,24(5):618-622
A sparse matrix multiplication scheme with multiatom blocks is reported, a tool that can be very useful for developing linear-scaling methods with atom-centered basis functions. Compared to conventional element-by-element sparse matrix multiplication schemes, efficiency is gained by the use of the highly optimized basic linear algebra subroutines (BLAS). However, some sparsity is lost in the multiatom blocking scheme because these matrix blocks will in general contain negligible elements. As a result, an optimal block size that minimizes the CPU time by balancing these two effects is recovered. In calculations on linear alkanes, polyglycines, estane polymers, and water clusters the optimal block size is found to be between 40 and 100 basis functions, where about 55-75% of the machine peak performance was achieved on an IBM RS6000 workstation. In these calculations, the blocked sparse matrix multiplications can be 10 times faster than a standard element-by-element sparse matrix package. 相似文献
25.
Saravanan Gowrisankar 《Tetrahedron letters》2008,49(10):1670-1673
We synthesized 2-arylquinolines and tetrahydropyridines via palladium-mediated Heck type reactions starting from the Baylis-Hillman adducts. 2-Arylquinolines were prepared via the Heck type cyclization followed by concomitant aerobic oxidation. 相似文献
26.
27.
Chinnusamy Saravanan Sengodan Senthil Palaninathan Kannan 《Journal of polymer science. Part A, Polymer chemistry》2008,46(23):7843-7860
Copolymer containing new thermally reversible click chemistry‐assisted triazole‐substituted azobenzene and fulgimide units in the pendant F‐co‐A was prepared by free‐radical solution addition polymerization technique. The F and A were also prepared for comparison. The DSC analysis of F indicates that the polymer possessing the C‐form of fulgimide unit exhibited higher Tm than that of E‐form of the same polymer and revealed that the C‐form of fulgimide unit in F is highly ordered. The cis‐trans back isomerization behavior of the click chemistry‐assisted triazole‐substituted azobenzene unit in film A has thermal irreversibility, while in F‐co‐A it exhibited thermal reversibility. The UV‐exposed film of F‐co‐A heated around Tg leads to cis‐trans back isomerization of azobenzene unit and thermally stable C‐form of fulgimide which retains its conjugated structure where both the photochromic units are converted into planar conformations and exhibit high fluorescence properties. The fluorescence maxima of C‐form in F‐co‐A red shifted compared with F , because the substituted triazole ring in the azobenzene unit stabilized the C‐form of fulgimide unit. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7843–7860, 2008 相似文献
28.
R. Renganath Rao M. Vimudha N. R. Kamini M. K. Gowthaman B. Chandrasekran P. Saravanan 《Applied biochemistry and biotechnology》2017,182(2):511-528
Enzyme-based unhairing in replacement of conventional lime sulfide system has been attempted as an alternative for tackling pollution. The exorbitant cost of enzyme and the need for stringent process control need to be addressed yet. This study developed a mechanism for regulated release of protease from cheaper agro-wastes, which overcomes the necessity for stringent process control along with total cost reduction. The maximum protease activity of 1193.77 U/g was obtained after 96 h of incubation with 15% inoculum of the actinomycete strain Brevibacterium luteolum (MTCC 5982) under solid-state fermentation (SSF). The medium after SSF was used for unhairing without the downstream processing to avoid the cost involved in enzyme extraction. This also helped in the regulated release of enzyme from bran to the process liquor for controlled unhairing and avoided the problem of grain-pitting. Unhairing process parameters were standardized as 20% enzyme offer, 40% Hide-Float ratio at 5 ± 1 rpm, and process pH of 9.0. The cost of production of 1000 kU of the protease was calculated as 0.44 USD. The techno-economic feasibility studies for setting up an SSF enzyme production plant showed a high return on investment of 15.58% with a payback period of 6.4 years. 相似文献
29.
P. Saravanan G. Venkata RamanaK. Srinivasa Rao B. SreedharV.T.P. Vinod V. Chandrasekaran 《Journal of magnetism and magnetic materials》2011,323(15):2083-2089
Self-assembled Sm-Co nanoparticles in the form of spherical aggregates (referred as nanospheres) with diameter ranging from 50 to 180 nm were achieved by means of polyol technique. The size distribution of the Sm-Co nanospheres can be regulated close to ∼100 nm by controlling the molar ratio of Sm:Co precursor. The spherical aggregates exhibited Sm2Co7 phase as a major constituent; while the aggregates obtained at higher Co concentration showed co-existence of Co-phase with Sm2Co7 phase. Upon annealing, the biphasic nature of nanospheres (Sm2Co7/Co) transformed into Sm2Co17 structure. By varying the Sm:Co precursor ratio from 1:5 to 1:9, the coercivity (Hc) and magnetization (Ms) values of the as-synthesized nanospheres can be tuned from 336 to 140 Oe and from 63.7 to 108 emu/g, respectively, and these values significantly improved after annealing. Maximum values of Hc (1050 Oe) at the Sm:Co molar ratio of 1:5 and Ms of 184.6 emu/g at the Sm:Co molar ratio of 1:9 were achieved in the annealed samples. 相似文献
30.
Ramachandran Saravanan Yasuhiro Ono Kahoru Ohno 《Journal of Physics and Chemistry of Solids》2003,64(1):51-58
Electron density distribution of GaAs is determined by means of the maximum entropy method (MEM) using reasonably good X-ray data collected at room temperature and 200 K. The bonding electron distributions are clearly visible in the MEM map and the mixed covalent-ionic character in GaAs is evidenced. The density distributions at 200 K show more condensed electronic clouds as compared to the room temperature map, preserving the trend in the bonding characters. The electron densities at the middle of the bond are 0.79 and 0.70 e/Å3 at 200 K and at room temperature, respectively. The refined harmonic thermal factors are in good agreement with the published values. 相似文献