全文获取类型
收费全文 | 390篇 |
免费 | 13篇 |
国内免费 | 3篇 |
专业分类
化学 | 316篇 |
晶体学 | 4篇 |
力学 | 17篇 |
数学 | 11篇 |
物理学 | 58篇 |
出版年
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 5篇 |
2020年 | 3篇 |
2019年 | 3篇 |
2018年 | 4篇 |
2017年 | 3篇 |
2016年 | 9篇 |
2015年 | 10篇 |
2014年 | 8篇 |
2013年 | 10篇 |
2012年 | 33篇 |
2011年 | 22篇 |
2010年 | 18篇 |
2009年 | 16篇 |
2008年 | 30篇 |
2007年 | 28篇 |
2006年 | 25篇 |
2005年 | 23篇 |
2004年 | 15篇 |
2003年 | 18篇 |
2002年 | 36篇 |
2001年 | 11篇 |
2000年 | 9篇 |
1999年 | 1篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 12篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1969年 | 2篇 |
1967年 | 1篇 |
1931年 | 1篇 |
排序方式: 共有406条查询结果,搜索用时 15 毫秒
1.
In this paper we prove for several classes of ideals in regular local rings of equicharacteristic 0 that the symbolic square
of the ideal contains no minimal generator of the ideal. Our techniques come from residual intersections, integral closures
of ideals, and differentials.
Received January 14, 1997; in final form March 20, 1997 相似文献
2.
3.
Reversed-phase LC-MS/MS is used to determine major estrogenic alkylphenol ethoxylates (APEOs) and their biotransformation products. It allows the simultaneous analysis of eight APEOs, alkylphenoxy carboxylates (APECs) and alkylphenols (APs) in sewage treatment plant (STP) effluents in the same extract after solid-phase enrichment on polymeric Oasis HLB. As precursor ions, [APEO + NH4]+, [APEC - H]- and [AP - H]- were monitored. Instrumental limits of detection (LOD) were 2-600 pg, corresponding to sample concentrations of 0.04-12 ng l(-1), without correction for overall method recoveries. Matrix-induced signal suppression during electrospray ionisation (ESI) and extraction as well as overall method recoveries were assessed and the suitability of deuterated surrogates as internal standards was evaluated. 相似文献
4.
Zhu L Ostash B Rix U Nur-E-Alam M Mayers A Luzhetskyy A Mendez C Salas JA Bechthold A Fedorenko V Rohr J 《The Journal of organic chemistry》2005,70(2):631-638
The angucycline antibiotic family of the landomycins displays potent antitumor activity. To elucidate early post polyketide synthase (PKS) tailoring steps of the landomycin E biosynthetic pathway in Streptomyces globisporus 1912, the mutant S. globisporus M12 was prepared through gene replacement experiment of lndM2. It encodes an enzyme with putative oxygenase and reductase domains, according to sequencing of the gene and its counterpart lanM2 from S. cyanogenus S136 landomycin A biosynthetic gene cluster. The isolation of the novel shunt products 11-hydroxytetrangomycin and 4-hydroxytetrangomycin along with the well-known angucyclines tetrangomycin and tetrangulol from the culture of S. globisporus M12 provides evidence for the involvement of lndM2 in the early biosynthetic pathway of the landomycins, in particular in the formation of the alicyclic 6-hydroxy function of the landomycin aglycon. We therefore propose LndM2 to be responsible for both hydroxylation of the 6-position and its subsequent reduction. These reactions are necessary before the glycosylation reactions can occur. The results are in agreement with the originally published structure of landomycin but do not support the recently suggested revised structure. 相似文献
5.
Biener MM Biener J Friend CM 《Langmuir : the ACS journal of surfaces and colloids》2005,21(5):1668-1671
The Au-S interaction is probably the most intensively studied interaction of Au surfaces with nonmetals, as, for example, it plays an important role in Au ore formation(1) and controls the structure and dynamics of thiol-based self-assembled monolayers (SAMs). Various S-induced surface structures on Au(111) were recently reported for different conditions and predominantly interpreted in terms of a static Au surface. Here, we demonstrate that the Au(111) surface exhibits a very dynamic character upon interaction with adsorbed sulfur: large-scale surface restructuring and incorporation of Au atoms into a growing 2D AuS phase were observed in situ. These results provide new insight into the Au-S surface chemistry. 相似文献
6.
Three methods of determination for uranium and thorium traces and ultratraces in glass were developed: a simple and powerful ICP-MS method exhibiting limits of determination in the one ng/g-range; a complex method with end-determination by classical photometry and a limit of determination for U and Th of 20 ng/g; and a method with chelate-complex formation for U and Th and subsequent GC-detection with a 63Ni-ECD with limits of determination in the g/g-range. These methods are critically compared and tested for real type samples of special glasses.Abbreviations used AAS
Atomic absorption spectrophotometry
- ECD
Electron capture detector
- FOD
1,1,1,2,2,3,3-Heptafluoro-7,7-dimethyl-4,6-octanedion
- GC
Gas chromatography
- HFA
1,1,1,5,5,5-Hexafluoro-2,4-pentanedione
- ICP-AES, -MS
Inductively coupled plasma-atomic emission spectrometry, metry, -mass spectrometry
- LAS
Liquid absorption spectrophotometry = classical photometry
- NAA
Neutron activation analysis
- NIST
National Institute of Standardization and Technology (Gaithersburg, U.S.A.)
- TBP
Tri-(n-butyl)-phosphate
- TFA
1,1,1-Trifluoro-2,4-pentanedione
- TTFA
1-(2-Thenoyl)-3,3,3-trifluoroacetone
- XRS
X-ray (fluorescence) spectrometry 相似文献
7.
8.
The following substances could be prepared by Grignard reactions or by conversions with trichlorosilane: C6F5CH2CHCH2, C6F5(CH2)3SiCl3, CF3(CF2)9CH2CHCH2, CF3(CF2)7(CH2)2SiCl3, CF3(CF2)11(CH2)3CHCH2 und CF3(CF2)11(CH2)5SiCl3.They were characterized by spectroscopical and microanalytical methods. 相似文献
9.
10.
The hindered rotor transitions of H(2) adsorbed in the chemically related and prototypical porous metal-organic frameworks IRMOF-1, IRMOF-8, IRMOF-11, and MOF-177 were studied by inelastic neutron scattering to gain information on the specifics of H(2) binding in this class of adsorbents. Remarkably sharp and complex spectra of these materials signify a diversity of well-defined binding sites. Similarities in the spectral features as a function of H(2) loading and correlations with recent crystallographic studies were used to assign transitions ranging in rotational barrier from <0.04 to 0.6 kcal/mol as corresponding to localized adsorption sites on the organic and inorganic components of these frameworks. We find that binding of H(2) at the inorganic cluster sites is affected by the nature of the organic link and is strongest in IRMOF-11 in accord with our adsorption isotherm data. The sites on the organic link have lower binding energies, but a much greater capacity for increases in H(2) loading, which demonstrates their importance for hydrogen uptake by these materials. 相似文献