全文获取类型
收费全文 | 715篇 |
免费 | 16篇 |
国内免费 | 3篇 |
专业分类
化学 | 424篇 |
晶体学 | 9篇 |
力学 | 9篇 |
数学 | 42篇 |
物理学 | 250篇 |
出版年
2023年 | 7篇 |
2021年 | 8篇 |
2020年 | 8篇 |
2019年 | 10篇 |
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 6篇 |
2015年 | 16篇 |
2014年 | 12篇 |
2013年 | 21篇 |
2012年 | 26篇 |
2011年 | 34篇 |
2010年 | 14篇 |
2009年 | 12篇 |
2008年 | 46篇 |
2007年 | 52篇 |
2006年 | 48篇 |
2005年 | 53篇 |
2004年 | 56篇 |
2003年 | 37篇 |
2002年 | 25篇 |
2001年 | 13篇 |
2000年 | 14篇 |
1999年 | 12篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 11篇 |
1994年 | 7篇 |
1993年 | 11篇 |
1992年 | 8篇 |
1991年 | 9篇 |
1990年 | 13篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1986年 | 4篇 |
1985年 | 10篇 |
1984年 | 5篇 |
1981年 | 7篇 |
1979年 | 6篇 |
1977年 | 4篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1971年 | 3篇 |
1969年 | 3篇 |
1967年 | 3篇 |
1909年 | 3篇 |
1904年 | 3篇 |
1903年 | 3篇 |
1901年 | 3篇 |
1898年 | 3篇 |
排序方式: 共有734条查询结果,搜索用时 156 毫秒
1.
Analytical and Bioanalytical Chemistry - 相似文献
2.
3.
4.
5.
Cross ratios constitute an important tool in classical projective geometry. Using the theory of Tutte groups as discussed in [6] it will be shown in this note that the concept of cross ratios extends naturally to combinatorial geometries or matroids. From a thorough study of these cross ratios which, among other observations, includes a new matroid theoretic version and proof of the Pappos theorem, it will be deduced that for any projective space M=
n
(K) of dimension n2 of M over some skewfield K the inner Tutte group is isomorphic to the commutator factor group K
*/[K
*, K
*] of K
*K{0}. This shows not only that in case M=
n
(K) our matroidal cross ratios are nothing but the classical ones. It can also be used to correlate orientations of the matroid M=
n
(K) with the orderings of K. And it implies that Dieudonné's (non-commutative) determinants which, by Dieudonné's definition, take their values in K
*/[K
*, K
*] as well, can be viewed as a special case of a determinant construction which works for just every combinatorial geometry.Research supported by the DFG (Deutsche Forschungsgemeinschaft). 相似文献
6.
The development of an amperometric biosensor for the determination of phenolic compounds is described, using quinoprotein glucose dehydrogenase. The enzyme is integrated into carbon paste and its ability to donate electrons to oxidized phenolic compounds during glucose oxidation is exploited. The sensor response is based on electrochemical oxidation of the phenolic compound followed by its enzymatic regeneration when the bulk solution contains glucose and the electrode is potentiostated at +500 mV (vs. Ag/AgCl/0.1 mol/L KCl). As the result of the catalytic analyte regeneration the electrodes offer very sensitive measurements of redox species like p-aminophenol and hydroquinone and catecholamines such as epinephrine, norepinephrine, and dopamine. The sensor performance is characterized for the different substrates. Highest sensitivity is achieved for p-aminophenol which could be determined at sub-nanomolar level. 相似文献
7.
Sandrine Bouquillon Ulla Létinois-Halbes Jacques Muzart 《Journal of organometallic chemistry》2003,687(2):377-383
The reaction between palladium acetate, (−)-ephedrine and potassium acetate led to bis-chelate complex Pd[OCH(Ph)NH(Me)]2 whose the trans-structure is obtained from calculations. The use of this complex to catalyze either the 1,4-hydrogenation of (E)-2-benzyliden-1-tetralone or Heck reaction of phenyl iodide with 3-methyl-3-buten-2-ol led to a low enantiomeric excess. 相似文献
8.
Sonesson AW Callisen TH Brismar H Elofsson UM 《Langmuir : the ACS journal of surfaces and colloids》2005,21(25):11949-11956
We have analyzed surface diffusion properties of a variant of Thermomyces lanuginosa lipase (TLL) on hydrophilic silica and silica methylated with dichlorodimethylsilane (DDS) or octadecyltrichlorosilane (OTS). For this study a novel method for analysis of diffusion on solid surfaces was developed. The method is based on fluorescence recovery after photobleaching using confocal microscopy. When a rectangular area of the sample was photobleached, fluorescence recovery could be analyzed as one-dimensional diffusion, resulting in simplified mathematical expressions for fitting the data. The method was initially tested by measuring bovine serum albumin diffusion on glass, which led to a diffusion coefficient in good correspondence to earlier reports. For the analysis of TLL diffusion, ellipsometry data of TLL adsorption were used to calibrate fluorescence intensity to surface density of lipase, enabling measurements of the diffusion coefficient at different surface densities. The average diffusion coefficient was calculated in two time intervals after adsorption. Mobile fraction and diffusion coefficient were lowest on the OTS surface, when extrapolated to infinite surface dilution. Moreover, the diffusion rate decreased with time on the hydrophobic surfaces. Our observations can be explained by the surface dependence on the distribution of orientations and conformations of adsorbed TLL, where the transition from the closed to the catalytically active open and more hydrophobic structure is important. 相似文献
9.
Lithium reductions of 7-chloronorbornadiene and of bis(7-norbornadienyl)mercury both provide (C7H7)2Li2 ( 5a ). This product is accompanied by C7H7Li2Cl ( 5c ) in the first case, and by C7H7Li ( 5b ) in the second. The theoretically anticipated properties of all three organolithiums are apparent in the consistent Cs symmetry of their hydrocarbon ligands, their protolytic destruction by 12-crown-4, and their significant J(C(7), Li) ( 5a , 7.6; 5b , 16.0; 5c 8.9 Hz). 相似文献
10.
Nielsen UG Topsøe NY Brorson M Skibsted J Jakobsen HJ 《Journal of the American Chemical Society》2004,126(15):4926-4933
The first observations of the complete manifold of spinning sidebands (ssbs) including both the central and satellite transitions in (51)V MAS NMR spectra of surface vanadia nanoparticles on titania in DeNO(x) catalysts are presented. (51)V quadrupole coupling and chemical shift anisotropy parameters for the dominating vanadia structure are determined from (51)V MAS NMR spectra recorded at 9.4 and 14.1 T. Based on correlations previously established between (51)V NMR parameters and crystal structure data for inorganic vanadates, the NMR data are consistent with vanadium in a distorted octahedral oxygen coordination environment for the so-called strongly bonded vanadia species on the surface. The investigation includes two vanadia-titania model catalysts and six industrial-type DeNO(x) catalysts. 相似文献