全文获取类型
收费全文 | 1318篇 |
免费 | 44篇 |
国内免费 | 7篇 |
专业分类
化学 | 972篇 |
晶体学 | 15篇 |
力学 | 25篇 |
数学 | 48篇 |
物理学 | 309篇 |
出版年
2022年 | 11篇 |
2021年 | 14篇 |
2020年 | 21篇 |
2019年 | 20篇 |
2016年 | 24篇 |
2015年 | 26篇 |
2014年 | 29篇 |
2013年 | 57篇 |
2012年 | 53篇 |
2011年 | 75篇 |
2010年 | 41篇 |
2009年 | 49篇 |
2008年 | 70篇 |
2007年 | 73篇 |
2006年 | 56篇 |
2005年 | 60篇 |
2004年 | 57篇 |
2003年 | 52篇 |
2002年 | 65篇 |
2001年 | 41篇 |
2000年 | 32篇 |
1999年 | 29篇 |
1998年 | 13篇 |
1997年 | 9篇 |
1996年 | 10篇 |
1995年 | 9篇 |
1994年 | 14篇 |
1993年 | 16篇 |
1992年 | 35篇 |
1991年 | 20篇 |
1990年 | 18篇 |
1989年 | 17篇 |
1988年 | 21篇 |
1987年 | 13篇 |
1986年 | 7篇 |
1985年 | 19篇 |
1984年 | 18篇 |
1983年 | 16篇 |
1982年 | 13篇 |
1981年 | 12篇 |
1980年 | 9篇 |
1979年 | 8篇 |
1977年 | 14篇 |
1976年 | 10篇 |
1974年 | 9篇 |
1973年 | 15篇 |
1970年 | 6篇 |
1969年 | 6篇 |
1968年 | 9篇 |
1965年 | 6篇 |
排序方式: 共有1369条查询结果,搜索用时 234 毫秒
41.
Isolation of lignan glucosides and neolignan sulfate from the leaves of Glochidion zeylanicum (Gaertn) A. Juss 总被引:2,自引:0,他引:2
Six lignan and neolignan derivatives (1-6) were isolated from the n-BuOH-soluble fraction of a MeOH extract of the leaves of Glochidion zeylanicum. On the basis of spectral data, their structures were elucidated to be (+)-isolarisiresinol 3a-O-beta-glucopyranoside (1), dihydrodehydrodiconiferyl alcohol 4-, 9- and 9'-O-beta-D-glucopyranosides (2-4, respectively), (+)-isolarisiresinol 2a-O-beta-D-glucopyranoside (5), and dihydrodehydrodiconiferyl alcohol 9-O-sulfate (6), and 5 and 6 were new compounds. 相似文献
42.
43.
44.
45.
Takeda Y Isai N Masuda T Honda G Takaishi Y Ito M Otsuka H Ashurmetov OA Khodzhimatov OK 《Chemical & pharmaceutical bulletin》2001,49(8):1039-1041
From the aerial parts of Phlomis spinidens, two new flavonol bisglycosides, phlomisflavosides A (1) and B (2), were isolated together with the known compounds, astragalin, isoquercitrin, lamiridoside, phlomoside A, shanzhiside methyl ester, 8-O-acetylshanzhiside methyl ester, phlorigidoside C, rodioloside (=salidroside), forsythoside B, citroside A and lariciresinol-4'-O-beta-D-glucoside. The structures of the new compounds were elucidated based on spectral and chemical evidence. 相似文献
46.
47.
Determination of chemical form of antimony in contaminated soil around a smelter using X-ray absorption fine structure. 总被引:1,自引:0,他引:1
Masaki Takaoka Satoshi Fukutani Takashi Yamamoto Masato Horiuchi Naoya Satta Nobuo Takeda Kazuyuki Oshita Minoru Yoneda Shinsuke Morisawa Tsunehiro Tanaka 《Analytical sciences》2005,21(7):769-773
Only limited information is available about the behavior of antimony (Sb) in contaminated soils. However, understanding the behavior of Sb in contaminated soils is important, because the toxicity or solubility of this element depends on its chemical state. In this study, we investigated the levels of Sb and the chemical forms of Sb in the soil around a smelter using X-ray absorption fine structure (XAFS) spectra. The highest Sb concentration in the contaminated soil was 2900 mg/kg dry soil. According to Sb-K edge X-ray absorption near edge (XANE) spectra, the Sb in the soil was in the form of Sb(V) compounds. The similarity of extended XAFS (EXAFS) spectra suggests that Sb speciation was independent of the sampling site, which indicates that Sb or Sb2O3 emitted from the smelter was converted into Sb(V) compounds in the soil. 相似文献
48.
127I M?ssbauer spectra of good quality were obtained at 20 K using a Zn127mTe source produced by high flux neutron irradiation of 66Zn-126Te at reactor core. The M?ssbauer spectra for KI and some iodine(III) compounds with absorption intensity of about 5% suggest that the 127I M?ssbauer spectroscopy is useful in elucidating the bonding nature of the iodine compounds. Preparative method of the M?ssbauer source and experimental technique are reported in detail. 相似文献
49.
We implemented ab initio self‐consistent field (SCF) fractional occupation numbers (FON) calculation with Dunlap's interpolation scheme for the twisted ethylene, which is a prototype molecule of a σ–π biradical system. The calculational results are compared with those of complete‐active‐space (CAS) SCF and spin‐unrestricted Kohn–Sham (UKS) calculations on potential surfaces, occupation numbers of natural orbitals, and correlation entropies. It was found that the UKS methods gave similar results to CASSCF, while the FON solutions appeared in only the nearly complete degenerate region. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 93: 317–323, 2003 相似文献
50.
[reaction: see text] Reaction of gamma-p-toluenesulfonyl-alpha,beta-epoxysilane with alkyl halides and aldehydes followed by treatment with n-Bu4NF affords alpha,beta-unsaturated aldehydes via a Brook rearrangement-mediated tandem process under extremely mild conditions. 相似文献