全文获取类型
收费全文 | 664篇 |
免费 | 22篇 |
国内免费 | 1篇 |
专业分类
化学 | 434篇 |
晶体学 | 17篇 |
力学 | 3篇 |
数学 | 53篇 |
物理学 | 180篇 |
出版年
2023年 | 6篇 |
2022年 | 8篇 |
2021年 | 11篇 |
2020年 | 12篇 |
2019年 | 10篇 |
2018年 | 6篇 |
2017年 | 8篇 |
2016年 | 20篇 |
2015年 | 17篇 |
2014年 | 20篇 |
2013年 | 62篇 |
2012年 | 55篇 |
2011年 | 40篇 |
2010年 | 21篇 |
2009年 | 21篇 |
2008年 | 33篇 |
2007年 | 23篇 |
2006年 | 30篇 |
2005年 | 25篇 |
2004年 | 24篇 |
2003年 | 24篇 |
2002年 | 16篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1992年 | 7篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 9篇 |
1988年 | 4篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1985年 | 9篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1978年 | 11篇 |
1977年 | 5篇 |
1976年 | 10篇 |
1975年 | 8篇 |
1973年 | 5篇 |
1958年 | 4篇 |
1957年 | 4篇 |
排序方式: 共有687条查询结果,搜索用时 687 毫秒
31.
Archana Chaudhary Ram Gopal Meena Nagar Rakesh Bohra 《Journal of Sol-Gel Science and Technology》2014,69(1):102-106
Some oxime modified complexes of the type [Zr{OPri}4?n{L}n] {where, n = 1–4 and LH=(CH3)2C=NOH (1–4) and C9H16C=NOH (5–8)} have been synthesized by the reaction of [Zr(OPri)4·PriOH] with oximes, in anhydrous refluxing benzene. These synthesized complexes were characterized by elemental analyses, molecular weight measurements, ESI-mass, FT-IR and NMR (1H and 13C{1H}) spectral studies. The ESI-mass spectral studies indicate dimeric nature for [Zr{OPri}2{ONC(CH3)2}2] (2), [Zr{OPri}3{ONC10H16}] (5) and [Zr{OPri}{ONC10H16}3] (7) and monomeric nature for [Zr{ONC10H16}4] (8). Oximato ligands appear to bind the zirconium in side on manner in all the complexes. Thermogravimetric curves of (2) and (8) exhibit multi-step decomposition with the formation of ZrO2, under nitrogen atmosphere. Sol–gel transformations of precursors (5), (6), (7) and (8) in organic medium, yielded nano-sized tetragonal phase of zirconia samples (a), (b), (c) and (d), respectively, on sintering at ~600 °C. All these samples were characterized by Powder XRD patterns and EDX analyses. Surface morphologies of these samples were investigated by SEM images. 相似文献
32.
Gopal Lamichhane Prakash Raj Pandeya Ramakanta Lamichhane Su-jin Rhee Hari Prasad Devkota Hyun-Ju Jung 《Molecules (Basel, Switzerland)》2022,27(3)
Background: Ponciri Fructus, a crude drug consisting of the dried immature fruits of Poncirus trifoliata (L.) Raf., is a popular folk medicine used for the treatment of allergy and gastrointestinal disorders in Korea and China. In this study, the anti-adipogenic activity of extracts and isolated compounds were evaluated using 3T3-L1 preadipocytes. Methods: Dried immature fruits were extracted and fractionated into n-hexane, ethyl acetate (EtOAc), n-butanol and water-soluble fractions. The ethanol extract and fractions were tested for anti-adipogenic activity in the 3T3-L1 cell line. The active fractions (n-hexane and EtOAc fractions) were further subjected to chromatographic techniques to isolate and identify active compounds. Furthermore, the isolated compounds were evaluated for their anti-adipogenic activity. Results: Altogether, seven compounds, including two flavonoids, one phytosteroid and four coumarin derivatives, were isolated. Ethanol extract, n-hexane fraction, EtOAc fraction and three isolated compounds (phellopterin, oxypeucedanin and poncirin) showed significant anti-adipogenic activity as observed by reduced lipid deposition in differentiated 3T3-L1 cells. Further, oxypeucedanin downregulated the key adipogenic markers, such as peroxisome proliferator-activated receptors proteins γ (PPAR-γ), sterol response element binding proteins-1 (SREBP-1), CCAAT/enhancer binding proteins-α (C/EBP-α), adipocyte-specific lipid binding proteins (FABP-4), adipocyte fatty acid binding proteins (aP2), lipoprotein lipase (LPL) and leptin. Conclusion: This study indicated that the ethanol extract, hexane fraction and ethyl acetate fraction of P. trifoliata fruits possess strong anti-adipogenic activity, containing the active compounds such as phellopterin, oxypeucedanin and poncirin. Further research is recommended to explore their efficacy and safety in animal and clinical models. 相似文献
33.
Trialkyl acyl ammonium halides have found to be superior phase transfer catalysts. They were easy to prepare and afford the reactions to be carried out at elevated temperature, owing to their stability. 相似文献
34.
Gopal Krishan M. S. Rao C. P. Kumar Prabhat Semwal 《Journal of Radioanalytical and Nuclear Chemistry》2015,303(3):2221-2225
35.
The synthesis of the title pheromones involves solvomer-curation of an olefin and reductive carbon-carbon bond formation with α,β-unsaturated carbonyl compounds to give the key intermediates 3(a & b), which by simple conventional methods offered (1) & (2). 相似文献
36.
The effect of pressure on the conductivity of fast ion conducting AgI-Ag2O-MoO3 glasses has been investigated down to 150 K. The observed variation of conductivities appears to support the application
of cluster model to the ionic glasses.
Contribution No. 258 from the Solid State and Structural Chemistry Unit. 相似文献
37.
38.
39.
Electrical resistance measurements are reported for amorphous In20Te80 and Cu25Au5Te70 alloys up to a pressure of 80 Kbar using a Bridgman anvil apparatus and a four lead arrangement to measure resistances. The amorphous samples are produced by liquisol quenching. The resistance shows time dependent changes which are analysed in detail. The contention that there is a pressure-induced transformation from the amorphous to the crystalline phase is confirmed by X-ray diffraction of samples recovered after they were pressurised to 35 Kbar in a hydrostatic environment. 相似文献
40.