全文获取类型
收费全文 | 445篇 |
免费 | 12篇 |
国内免费 | 5篇 |
专业分类
化学 | 215篇 |
晶体学 | 8篇 |
力学 | 18篇 |
数学 | 64篇 |
物理学 | 157篇 |
出版年
2021年 | 6篇 |
2020年 | 10篇 |
2019年 | 4篇 |
2018年 | 4篇 |
2016年 | 3篇 |
2015年 | 10篇 |
2014年 | 9篇 |
2013年 | 20篇 |
2012年 | 18篇 |
2011年 | 21篇 |
2010年 | 11篇 |
2009年 | 9篇 |
2008年 | 18篇 |
2007年 | 26篇 |
2006年 | 15篇 |
2005年 | 21篇 |
2004年 | 15篇 |
2003年 | 7篇 |
2002年 | 19篇 |
2001年 | 22篇 |
2000年 | 10篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 7篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1993年 | 7篇 |
1992年 | 16篇 |
1991年 | 6篇 |
1990年 | 3篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 7篇 |
1984年 | 3篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 12篇 |
1976年 | 15篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1973年 | 6篇 |
1972年 | 3篇 |
1971年 | 3篇 |
排序方式: 共有462条查询结果,搜索用时 343 毫秒
11.
The infrared spectra, transmittance, and polarized reflectance of Cs3CoCl5 are reported. The group theoretical analysis was executed and a vibrational assignment proposed on the basis of D4h symmetry. Factor group and site effects are discussed. 相似文献
12.
Tormos JR Wiley KL Seravalli J Nachon F Masson P Nicolet Y Quinn DM 《Journal of the American Chemical Society》2005,127(42):14538-14539
Secondary beta-deuterium kinetic isotope effects have been measured as a function of substrate concentration for recombinant human butyrylcholinesterase-catalyzed hydrolysis of acetyl-L3-thiocholine (L = 1H or 2H). The isotope effect on V/K is inverse, D3V/K = 0.93 +/- 0.03, which is consistent with conversion of the sp2 hybridized carbonyl carbon of the scissile ester bond of the E + A reactant state to a quasi-tetrahedral structure in the acylation transition state. In contrast, the isotope effect on Vmax under conditions of substrate activation is markedly normal, D3(betaVmax) = 1.29 +/- 0.06, an observation that is consistent with accumulation of a tetrahedral intermediate as the reactant state for catalytic turnover. Generally, tetrahedral intermediates for nonenzymatic ester hydrolyses are high-energy steady-state intermediates. Apparently, butyrylcholinesterase displays an unusual ability to stabilize such intermediates. Hence, the catalytic power of cholinesterases can largely be understood in terms of their ability to stabilize tetrahedral intermediates in the multistep reaction mechanism. 相似文献
13.
Christopher Batich Edgar Heilbronner Clayton B. Quinn John R. Wiseman 《Helvetica chimica acta》1976,59(2):512-522
Photoelectron spectroscopy has been used to examine the consequences of steric inhibition of conjugation in a distorted vinyl sulfide and vinyl ether. Based upon the degree of interaction a deviation from coplanarity of 70°–75° is calculated for 9-oxabicyclo[3.3.1]non-1-ene ( 3 ) and approximately 75°–80° for the sulfur analog 6 . 相似文献
14.
Polyelectrolyte multilayer thin films were prepared via the alternate deposition of poly(allylamine hydrochloride) (PAH) and a blend of poly(acrylic acid) (PAA) and poly(styrenesulfonate) (PSS). When the pH of the blend solution was 3.5, the presence of PAA in this solution significantly increased the total film thickness. With only 10 wt % PAA in the blend adsorption solution, a large increase in film thickness was observed (92 nm cf. 18 nm). It was also demonstrated that the total amount of PSS adsorbed was enhanced by the presence of PAA in the blend solution, showing that the blend solution composition influenced that of the multilayer films. Thin films prepared with nanoblended layers also showed improved pH stability, because they exhibited reduced film rearrangement upon exposure to acidic conditions (pH = 2.5). 相似文献
15.
16.
17.
18.
Formulas are derived for consistent evaluation of permutationally totally symmetric and determinantally antisymmetric powers of generalized combinations in which irreducible representations may occur with either positive or negative weights. 相似文献
19.
We investigate the existence of unbounded solutions and the period-two convergence of solutions of the equation in the title with the parameter γ positive, the remaining parameters nonnegative, and with nonnegative initial conditions. 相似文献
20.
Harish Holla Ian D. Jenkins Juliette E. Neve Rebecca H. Pouwer Ngoc Pham Simon J. Teague Ronald J. Quinn 《Tetrahedron letters》2012,53(52):7101-7103
A synthesis of the unusual cyclobutane-quinolinone alkaloids melicodenines C, D and E by intermolecular [2+2] cycloaddition is described. 相似文献