全文获取类型
收费全文 | 217篇 |
免费 | 6篇 |
专业分类
化学 | 149篇 |
晶体学 | 1篇 |
力学 | 6篇 |
数学 | 18篇 |
物理学 | 49篇 |
出版年
2023年 | 8篇 |
2022年 | 4篇 |
2021年 | 7篇 |
2020年 | 6篇 |
2019年 | 12篇 |
2018年 | 3篇 |
2017年 | 6篇 |
2016年 | 17篇 |
2015年 | 7篇 |
2014年 | 6篇 |
2013年 | 7篇 |
2012年 | 17篇 |
2011年 | 15篇 |
2010年 | 12篇 |
2009年 | 10篇 |
2008年 | 19篇 |
2007年 | 12篇 |
2006年 | 12篇 |
2005年 | 7篇 |
2004年 | 6篇 |
2003年 | 8篇 |
2002年 | 6篇 |
2001年 | 6篇 |
1999年 | 1篇 |
1993年 | 1篇 |
1987年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有223条查询结果,搜索用时 15 毫秒
101.
102.
We propose a universal definition of reaction-specific solvent coordinate, described in terms of molecular-dynamic trajectories of the solvent and suitable for a variety of reactions in viscous solvents. We then use molecular dynamics simulations to obtain two-dimensional potential energy and free energy surfaces of model liquid phase isomerisation reactions in solvent–solute coordinates and discuss factors determining their topography. 相似文献
103.
We report a highly diastereoselective approach for the synthesis of a functionalized dodecahydrobenz[a]indolo[3,2-h]quinolizine ring system that is present as the heterocyclic core of the manadomanzamine alkaloids. We have achieved complete control over the relative and absolute stereochemistries at the three contiguous stereocentres at ring positions 1, 10 and 24 in only two linear synthetic steps. The introduction of useful functionality to the heterocyclic skeleton is significant as this may allow for future derivatization, and application of this route in an asymmetric synthesis of the manadomanzamine natural products. 相似文献
104.
105.
Jilek RE Spencer LP Lewis RA Scott BL Hayton TW Boncella JM 《Journal of the American Chemical Society》2012,134(24):9876-9878
Metathesis reactions between uranium tetrachloride and lithium 2,6-diisopropylphenylamide in the presence of 4,4'-dialkyl-2,2'-bipyridyl (R(2)bpy; R = Me, (t)Bu) or triphenylphosphine oxide (tppo) appear to generate bis(imido)uranium(IV) in situ. These extremely reactive complexes abstract chloride from dichloromethane to generate U(NDipp)(2)Cl(R(2)bpy)(2) or U(NDipp)(2)Cl(tppo)(3) (Dipp = 2,6-(i)Pr(2)C(6)H(3)). The preparation of the bromide and iodide analogues U(NDipp)(2)X(R(2)bpy)(2) was achieved by addition of CH(2)X(2) (X = Br, I) to the uranium(IV) solutions. The uranium(V) halides were characterized by X-ray crystallography and found to exhibit linear N-U-N units and short U-N bonds. Electrochemical measurements were made on the chloride bipyridine species, which reacts readily with iodine or ferrocenium to generate bis(imido)uranium(VI) cations. 相似文献
106.
Alexandra van Remoortere René J. M. van Zeijl Nico van den Oever Julien Franck Rémi Longuespée Maxence Wisztorski Michel Salzet André M. Deelder Isabelle Fournier Liam A. McDonnell 《Journal of the American Society for Mass Spectrometry》2010,21(11):1922-1929
MALDI imaging and profiling mass spectrometry of proteins typically leads to the detection of a large number of peptides and
small proteins but is much less successful for larger proteins: most ion signals correspond to proteins of m/z < 25,000. This is a severe limitation as many proteins, including cytokines, growth factors, enzymes, and receptors have
molecular weights exceeding 25 kDa. The detector technology typically used for protein imaging, a microchannel plate, is not
well suited to the detection of high m/z ions and is prone to detector saturation when analyzing complex mixtures. Here we report increased sensitivity for higher
mass proteins by using the CovalX high mass HM1 detector (Zurich, Switzerland), which has been specifically designed for the
detection of high mass ions and which is much less prone to detector saturation. The results demonstrate that a range of different
sample preparation strategies enable higher mass proteins to be analyzed if the detector technology maintains high detection
efficiency throughout the mass range. The detector enables proteins up to 70 kDa to be imaged, and proteins up to 110 kDa
to be detected, directly from tissue, and indicates new directions by which the mass range amenable to MALDI imaging MS and
MALDI profiling MS may be extended. 相似文献
107.
Arylsilanes are efficient reagents for the gold-catalyzed oxyarylation of alkenes (21 examples, up to 85% isolated yield). Using commercially available Ph(3)PAuCl and readily prepared, benign arylsilanes, these two- and three-component reactions proceed smoothly in air. The oxidant, Selectfluor, not only facilitates entry to the Au(I/III) manifold but also provides a fluoride anion for silane activation, thereby avoiding the need for addition of a stoichiometric base. 相似文献
108.
Liam P. Spencer Ping Yang Brian L. Scott Enrique R. Batista James M. Boncella 《Comptes Rendus Chimie》2010,13(6-7):758-766
Novel cis- and trans-bis(imido) uranium disulfonamide derivatives have been prepared from iodide metathesis reactions between two equivalents of K[N(Me)(SO2Ar’)] (Ar’ = 4-Me-C6H4) and U(NtBu)2(I)2(L)x (L = OPPh3, x = 2; Me2bpy, x = 1; Me2bpy = 4,4’-dimethyl-2,2’-bipyridyl). These bis(amide) derivatives serve as useful precursors for the synthesis of the trans-diphenolate complex U(NtBu)2(O-2-tBuC6H4)2(OPPh3)2 (5), cis- and trans-dithiolate complexes U(NtBu)2(SPh)2(L)x (L = OPPh3 (6); Me2bpy (7)), and cis- and trans-dihalide complexes with the general formulas U(NtBu)2(X)2(L)x (X = Cl, L = OPPh3 (8), L = Me2bpy (10); X = Br, L = OPPh3 (9), L = Me2bpy (11)). DFT calculations performed on the trans-dihalide series U(NtBu)2(X)2(L)2 and the UO22+ analogues UO2X2(OPPh3)2 suggest that the uranium centers in the [U(NtBu)2]2+ ions possess more covalent character than analogous UO22+ derivatives but that the U-X bonds in the U(NtBu)2X2L2 complexes possess a more ionic nature. 相似文献
109.
Walsh AJ O'Dowd JA Bessler VM Shi K Smyth F Dailey JM Kelleher B Barry LP Ellis AD 《Optics letters》2012,37(10):1769-1771
An experimental method for characterizing the time-resolved phase noise of a fast switching tunable laser is discussed. The method experimentally determines a complementary cumulative distribution function of the laser's differential phase as a function of time after a switching event. A time resolved bit error rate of differential quadrature phase shift keying formatted data, calculated using the phase noise measurements, was fitted to an experimental time-resolved bit error rate measurement using a field programmable gate array, finding a good agreement between the time-resolved bit error rates. 相似文献
110.
[reaction: see text] The first total synthesis of the C(3)-symmetric and biologically active natural product, (-)-xyloketal A, has been accomplished in one step from phloroglucinol (1,3,5-trihydroxybenzene) and (4R)-3-hydroxymethyl-2,4-dimethyl-4,5-dihydrofuran. This remarkably direct process involved an exceedingly facile and diastereoselective boron trifluoride diethyl etherate-promoted triple electrophilic aromatic substitution reaction that was coupled to three bicyclic acetal formation reactions. 相似文献