全文获取类型
收费全文 | 987篇 |
免费 | 19篇 |
国内免费 | 2篇 |
专业分类
化学 | 685篇 |
晶体学 | 18篇 |
力学 | 30篇 |
数学 | 57篇 |
物理学 | 218篇 |
出版年
2021年 | 7篇 |
2020年 | 15篇 |
2019年 | 12篇 |
2016年 | 14篇 |
2015年 | 23篇 |
2014年 | 8篇 |
2013年 | 24篇 |
2012年 | 18篇 |
2011年 | 22篇 |
2010年 | 24篇 |
2009年 | 22篇 |
2008年 | 36篇 |
2007年 | 42篇 |
2006年 | 30篇 |
2005年 | 33篇 |
2004年 | 36篇 |
2003年 | 37篇 |
2002年 | 21篇 |
2001年 | 28篇 |
2000年 | 19篇 |
1999年 | 17篇 |
1998年 | 19篇 |
1997年 | 13篇 |
1996年 | 14篇 |
1995年 | 15篇 |
1994年 | 12篇 |
1993年 | 7篇 |
1992年 | 10篇 |
1991年 | 7篇 |
1990年 | 10篇 |
1989年 | 10篇 |
1986年 | 13篇 |
1985年 | 14篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1982年 | 17篇 |
1981年 | 14篇 |
1980年 | 17篇 |
1979年 | 12篇 |
1978年 | 29篇 |
1977年 | 21篇 |
1976年 | 13篇 |
1975年 | 8篇 |
1974年 | 9篇 |
1973年 | 17篇 |
1972年 | 9篇 |
1968年 | 13篇 |
1967年 | 6篇 |
1915年 | 6篇 |
1904年 | 6篇 |
排序方式: 共有1008条查询结果,搜索用时 15 毫秒
991.
The Lewis acid assisted triflate/methyl, azide/methyl, and chlorine/methyl exchange reactions between silicon and antimony have been studied in the reaction of R(Me(3)Si)N-SbCl(2) (R = Ter) with AgOTf, AgN(3), KOtBu, GaCl(3), and Me(3)SiN(3)/GaCl(3), resulting in the formation of different methylantimony compounds. Furthermore, R(Me(3)Si)N-SbCl(2) (R = SiMe(3)) was reacted with GaCl(3) at low temperatures to yield a hitherto unreported amino(chloro)stibenium cation, the proposed intermediate in methyl exchange reactions. Tetrachloridogallate salts bearing different stibinostibonium cations such as [(Me(3)Sb)SbMe(2)](+) and [(Me(3)Sb)(2)SbMe](2+) along with the GaCl(3) adduct of SbMe(3) were isolated from such R(Me(3)Si)N-SbCl(2)/GaCl(3) mixtures (R = SiMe(3)) at ambient temperatures, depending on the reaction parameters. 相似文献
992.
Fürstner A Alcarazo M César V Lehmann CW 《Chemical communications (Cambridge, England)》2006,(20):2176-2178
A high yielding and modular approach to N,N'-disubstituted imidazolium salts is described, providing access to substitution patterns that are beyond the reach of established methodology. 相似文献
993.
Joerg Seidler Melaku Adal Dieter Kübler Dirk Bossemeyer Wolf D. Lehmann 《Analytical and bioanalytical chemistry》2009,395(6):1713-1720
The catalytic subunit of recombinant wild-type cyclic adenosine monophosphate-dependent protein kinase A (PKA) has been analyzed
by a combination of 1D gel electrophoresis, in-gel digestion by trypsin, chymotrypsin, or endoproteinase AspN, and nano-ultraperformance
liquid chromatography–MS/MS. The MS/MS spectra were annotated by MASCOT and the annotations were manually controlled. Using
Ga(III)-immobilized metal ion affinity chromatography (IMAC), in addition to the four established autophosphorylation sites
of the catalytic subunit of recombinant PKA, pSer10, pSer139, pThr197, and pSer338, six new phosphorylated residues have been
characterized–pSer14, pThr48, pSer53, pSer212, pSer259, and pSer325. The established phosphorylation sites all are part of
a PKA consensus motif and were found to be almost completely modified. In contrast, the newly detected sites were only partially
phosphorylated. For estimation of their degree of phosphorylation, a method based on signal intensity measurements was used.
For this purpose, signal intensities of all phospho- and non-phosphopeptides containing a particular site were added for estimation
of site-specific phosphorylation degrees. This addition was performed over all peptides observed in the different digestion
experiments, including their different charge states. pThr48 and pSer259 are located within PKA consensus motifs and were
observed to be phosphorylated at 20% and 24%, respectively. pSer14 and pSer53 are located within inverted PKA consensus motifs
and were found to be phosphorylated around 10% and 15%, respectively. The sequence environments of pSer212 and pSer325 have
no similarity to the PKA consensus motif at all and were observed to be phosphorylated at about 5% or lower. All newly observed
phosphorylation sites are located at the surface of the native protein structure of the PKA catalytic subunit. The results
add new information on the theme of site-specific (auto)phosphorylation by PKA.
相似文献
994.
Keeyoon Sung Linda R. Brown Xinchuan Huang David W. Schwenke Timothy J. Lee Stephen L. Coy Kevin K. Lehmann 《Journal of Quantitative Spectroscopy & Radiative Transfer》2012,113(11):1066-1083
Nearly 4800 features of ammonia between 6300 and 7000 cm?1 with intensities ≥4×10?24 cm?1/(molecule·cm?2) at 296 K were measured using 16 pure NH3 spectra recorded at various temperatures (296–185 K) with the McMath–Pierce Fourier Transform Spectrometer at Kitt Peak National Observatory, AZ. The line positions and intensities were retrieved by fitting individual spectra based on a Voigt line shape profile and then averaging the values to form the experimental linelist. The integrated intensity of the region was 4.68×10?19 cm?1/(molecule·cm?2) at 296 K. Empirical lower state energies were also estimated for 3567 absorption line features using line intensities retrieved from 10 spectra recorded at gas temperature between 185 and 233 K. Finally, using Ground State Combination Differences (GSCDs) and the empirical lower state energy estimates, the quantum assignments were determined for 1096 transitions in the room temperature linelist, along with empirical upper state energies for 434 levels. The assignments correspond to seven vibrational states, as confirmed from recent ab initio calculations. The resulting composite database of 14NH3 line parameters will provide experimental constraints to ab initio calculations and support remote sensing of gaseous bodies including the atmospheres of Earth, (exo)planets, brown dwarfs, and other astrophysical environments. 相似文献
995.
996.
997.
Thomas Lehmann 《Nachrichten aus der Chemie》1994,42(2):214-215
998.
999.
K. H. Herrmann H. Kostial G. Lehmann A. F. Rudolph M. Rummelsburg 《Crystal Research and Technology》1977,12(8):833-840
For applications of Pb1–xSnxTe in infrared light emitting and light detecting devices it is necessary to control the energy gap. For determining the gap in as-grown Bridgman crystals indirect methods have to be used (measurement of lattice constant and density). The results of these indirect methods are compared with results obtained by more direct measurements (spectral photoresponse, intrinsic absorption edge). 相似文献
1000.
Thomas Lehmann 《Nachrichten aus der Chemie》2000,48(12):1525-1525