全文获取类型
收费全文 | 1193篇 |
免费 | 67篇 |
国内免费 | 8篇 |
专业分类
化学 | 770篇 |
晶体学 | 9篇 |
力学 | 47篇 |
数学 | 250篇 |
物理学 | 192篇 |
出版年
2023年 | 14篇 |
2022年 | 25篇 |
2021年 | 23篇 |
2020年 | 34篇 |
2019年 | 25篇 |
2018年 | 27篇 |
2017年 | 19篇 |
2016年 | 70篇 |
2015年 | 28篇 |
2014年 | 39篇 |
2013年 | 92篇 |
2012年 | 102篇 |
2011年 | 99篇 |
2010年 | 61篇 |
2009年 | 38篇 |
2008年 | 72篇 |
2007年 | 74篇 |
2006年 | 59篇 |
2005年 | 68篇 |
2004年 | 22篇 |
2003年 | 32篇 |
2002年 | 30篇 |
2001年 | 18篇 |
2000年 | 20篇 |
1999年 | 18篇 |
1998年 | 10篇 |
1997年 | 6篇 |
1996年 | 12篇 |
1995年 | 6篇 |
1993年 | 6篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 6篇 |
1989年 | 12篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1975年 | 4篇 |
1974年 | 10篇 |
1972年 | 4篇 |
1970年 | 2篇 |
1966年 | 4篇 |
排序方式: 共有1268条查询结果,搜索用时 0 毫秒
1.
Synthesis,Electronic Properties and WOLED Devices of Planar Phosphorus‐Containing Polycyclic Aromatic Hydrocarbons
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. François Riobé Rózsa Szűcs Dr. Pierre‐Antoine Bouit Dr. Denis Tondelier Bernard Geffroy Fátima Aparicio Julia Buendía Prof. Luis Sánchez Prof. Régis Réau Prof. László Nyulászi Prof. Muriel Hissler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(17):6547-6556
We describe the synthesis and the physical properties of polyaromatic hydrocarbons (PAHs) containing a phosphorus atom at the edge. In particular, the impact of the successive addition of aromatic rings on the electronic properties was investigated by experimental (UV/Vis absorption, fluorescence, cyclic voltammetry) and theoretical studies (DFT). The physical properties recorded in solution and in the solid state showed that the P‐containing PAHs exhibit properties expected for an emitter in white organic light‐emitting diodes (WOLEDs). 相似文献
2.
The direct regioselective C–H arylation of 3-methoxythiophene and 3,4-ethylenedioxythiophene (EDOT) was performed successfully under ‘Heck-type’ experimental conditions. This novel synthetic methodology has been used to prepare in a more simple way a series of oligothiophenes interesting for the electronic industry to build new synthetic organic materials. 相似文献
3.
Jelena Jefti Batrice Gillon Antoine Goujon Quitterie Nau Arsen Gukasov Epiphane Codjovi Franois Varret 《Polyhedron》2003,22(28):3555-3556
4.
5.
Packing two disks into a polygonal environment 总被引:1,自引:0,他引:1
We consider the following problem. Given a polygon P, possibly with holes, and having n vertices, compute a pair of equal radius disks that do not intersect each other, are contained in P, and whose radius is maximized. Our main result is a simple randomized algorithm whose expected running time, on any input, is O(nlogn). This is optimal in the algebraic decision tree model of computation. 相似文献
6.
Pierre Antoine Grillet 《Semigroup Forum》1995,50(1):317-326
An explicit upper bound is given for the number of commutative semigroups withn elements. 相似文献
7.
N. S. Oliveira J. Dorgan J. A. P. Coutinho A. Ferreira J. L. Daridon I. M. Marrucho 《Journal of Polymer Science.Polymer Physics》2007,45(5):616-625
The sorption of carbon dioxide in glassy Poly(lactic acid) (PLA) films was studied by quartz crystal microbalance (QCM) at high pressures. Two thermal treatments, melted and quenched, were performed in PLA with two different L:D contents, 80:20 and 98:2, films and compared with a third thermal protocol, annealed, and used in a previous work. The results obtained show that for pressures higher than 2 MPa, the carbon dioxide solubility is larger in PLA 80:20 than in PLA 98:2, indicating that the L:D plays a dominant role on this property. The thermal treatments only affect the gas solubility in PLA 98:2. Sorption isotherms at temperatures 303, 313, and 323 K, below the glass transition temperature of the polymer, and pressures up to 5 MPa were measured and analyzed with three different models, the dual‐mode sorption model, the Flory–Huggins equation, and a modified dual‐mode sorption model where the Henry's law term was substituted by the Flory–Huggins equation. This last model performs especially well for CO2 in PLA 80:20, due to the convex upward curvature of the solubility isotherms for that system. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 616–625, 2007 相似文献
8.
Antoine Royer 《Foundations of Physics》1992,22(5):727-736
For a wave packet evolving quantum mechanically, the rates of change of the expectations and uncertainties of the position and momentum are exactly the same as if Wigner's function instantaneously obeyed a classical Liouville equation (whatever the Hamiltonian). This extension of Ehrenfest's theorem should be useful for dealing with the evolution and manipulation of quantum states. 相似文献
9.
Summary This is a systematic X-ray diffraction study of the structure of the mesomorphic phases occurring with potassium soaps ranging from C8 to C22.Four types of structure have been identified. The first is lamellar with both polar groups and paraffin chains in the crystalline state. The second is also lamellar, but with both polar groups and paraffin chains in the liquid state. The third corresponds to the localization of indefinitely long ribbons on a two-dimensional oblique lattice; polar groups are crystalline and paraffin chains desorganized. The fourth corresponds to the localization of discs on a three-dimensionnalB-faces centered orthorhombic lattice; polar groups are crystalline and paraffin chains disorganized.The structural parameters and the polymorphism of the polar groups have been discussed.
Zusammenfassung Wir beschreiben hier eine systematische Röntgenstrahlendiffraktionsforschung der Struktur der mesomorphen Phasen von Kalium Seifen von C8 bis C22.Vier Strukturtypen wurden gefunden. Die erste Struktur ist lamellar; beides, die polaren Gruppen und die Paraffinketten sind kristallisiert. Die zweite Struktur ist auch lamellar; aber in diesem Falle sind beides, die polaren Gruppen und Paraffinketten geschmolzen. Die dritte Struktur entspricht einer Lokalisation von Seifenbändern in einem zweidimensionalen monoklinen Gitter; die polaren Gruppen sind kristallisiert und die Paraffinketten geschmolzen. Die vierte Struktur entspricht einer Lokalisation von Seifenscheiben in einemB-flächenzentrierten orthorhombischen Raumgitter; die Polargruppen sind kristallisiert und die Paraffinketten geschmolzen.Wir haben aus den experimentellen Resultaten einige Schlußfolgerungen gezogen.相似文献
10.
Moni Chauhan Claude Chuit Robert J. P. Corriu Catherine Rey Jean-Paul Declercq Antoine Dubourg 《Journal of organometallic chemistry》1996,510(1-2):173-179
The X-ray structure analysis of bis(8-dimethylamino-l-naphthyl)phenylphosphane (3) and of the corresponding sulphide 4 has revealed hexacoordination at phosphorus in both cases, the N … P separations being less than the sum of the van der Waal radii. Furthermore, in both cases the overall geometry corresponds to a distorted bicapped tetrahedron. The optimum geometry calculated for 4 via the
program developed by Autodesk (MM + method) suggests that the structure of the molecule is a function not only of steric requirements but also of electronic effects. 相似文献