全文获取类型
收费全文 | 1928篇 |
免费 | 57篇 |
国内免费 | 6篇 |
专业分类
化学 | 1278篇 |
晶体学 | 10篇 |
力学 | 99篇 |
数学 | 175篇 |
物理学 | 429篇 |
出版年
2022年 | 12篇 |
2021年 | 21篇 |
2020年 | 34篇 |
2019年 | 26篇 |
2018年 | 14篇 |
2017年 | 13篇 |
2016年 | 42篇 |
2015年 | 33篇 |
2014年 | 32篇 |
2013年 | 80篇 |
2012年 | 100篇 |
2011年 | 139篇 |
2010年 | 64篇 |
2009年 | 75篇 |
2008年 | 116篇 |
2007年 | 105篇 |
2006年 | 93篇 |
2005年 | 73篇 |
2004年 | 72篇 |
2003年 | 56篇 |
2002年 | 51篇 |
2001年 | 36篇 |
2000年 | 33篇 |
1999年 | 17篇 |
1998年 | 22篇 |
1997年 | 19篇 |
1996年 | 34篇 |
1995年 | 20篇 |
1994年 | 18篇 |
1993年 | 25篇 |
1992年 | 22篇 |
1991年 | 42篇 |
1990年 | 22篇 |
1989年 | 24篇 |
1988年 | 22篇 |
1987年 | 17篇 |
1986年 | 11篇 |
1985年 | 31篇 |
1984年 | 30篇 |
1983年 | 25篇 |
1982年 | 24篇 |
1981年 | 18篇 |
1980年 | 23篇 |
1979年 | 13篇 |
1978年 | 29篇 |
1977年 | 14篇 |
1976年 | 18篇 |
1975年 | 17篇 |
1972年 | 8篇 |
1968年 | 11篇 |
排序方式: 共有1991条查询结果,搜索用时 31 毫秒
151.
Cornelis Lensink Graeme J. Gainsford Neville I. Baxter 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(4):366-367
The title compound, [Ti(CF3O3S)2(C14H15NO2S)(C4H8O)], contains a unique ligand system in which the Ti ion is bound to the N and O atoms of a 2‐p‐toluenesulfonamide ligand, which is linked by an ethyl group to a coordinated cyclopentadiene moiety. The distorted octahedral geometry about the Ti ion is completed by two trifluoromethanesulfonate ligands and a tetrahydrofuran molecule. Comparison with related compounds shows that both the Ti—N and Ti—O bonds of the sulfonamide, although longer than normal values, indicate significant bonding interactions. 相似文献
152.
153.
A method making use of the photoacoustic effect to control the formation of large scale structures in an axisymmetric ethylene jet at Reynolds numbers ranging between 2,000 and 2,550 is described. The experiment involved modulating the beam of a CO2 laser at Strouhal frequencies between 0.31 and 0.46 and focussing the beam into the gas jet. Time-averaged flow fields, perturbed with photoacoustic pulses are compared to that forced with a sinusoidal acoustic excitation and the results of a parametric study of the photoacoustic forcing are presented. Perturbations, achieved by laser heating the gas molecules are shown to force the flow into the jet-column fundamental and harmonic mode and to enhance vortex pairing. Time-averaged merging events at different phases of the process are displayed. 相似文献
154.
155.
W. Franz S. Steeb H. Ebert H. Winter J. Voitländer 《Zeitschrift für Physik B Condensed Matter》1987,69(2-3):257-261
Soft X-ray emission experiments on Cu
x
Rh1–x
alloys for the compositionsx=0.0, 0.05, 0.10, 0.80 and 1.0, have been performed. In this paper we present the spectra of Cu-and Rh-L
III
core level-conduction band transitions. Using the data of recent self-consistent KKR-CPA electronic structure calculations we evaluate the corresponding SXS-cross sections and compare these theoretical results to our measurements. 相似文献
156.
Toby Cubitt Aram W. Harrow Debbie Leung Ashley Montanaro Andreas Winter 《Communications in Mathematical Physics》2008,284(1):281-290
Complementing recent progress on the additivity conjecture of quantum information theory, showing that the minimum output
p-Rényi entropies of channels are not generally additive for p > 1, we demonstrate here by a careful random selection argument that also at p = 0, and consequently for sufficiently small p, there exist counterexamples.
An explicit construction of two channels from 4 to 3 dimensions is given, which have non-multiplicative minimum output rank;
for this pair of channels, numerics strongly suggest that the p-Rényi entropy is non-additive for all p ≲ 0.11. We conjecture however that violations of additivity exist for all p < 1. 相似文献
157.
Andreas Winter Christian Friebe Manuela Chiper Martin D. Hager Ulrich S. Schubert 《Journal of polymer science. Part A, Polymer chemistry》2009,47(16):4083-4098
A series of main‐chain metallopolymers ( P1–P10 ) was prepared by the self‐assembly of rigid‐linear π‐conjugated bis(terpyridine) monomers ( 1–10 ) with ZnII ions and was fully characterized. The polymerization was additionally confirmed by UV/vis titration experiments. A strong increase in viscosities (around 1.6 times) relative to those of the monomer solutions was found. The thermal stability of P1–P10 compared with that of 1–10 was enhanced as a result of the metallopolymerization. The electro‐optical properties of the materials were investigated in detail. Tuning of the electrochemical and photophysical properties was enabled; thus, bright purple to green photoluminescent (PL) emission (PL quantum yields of 0.12–0.81) for P1–P10 was observed in solution with the emission color strongly depending on the nature of the π‐conjugated bis(terpyridine) system. Thin homogeneous films of P6 were prepared by solution processing, that is, spin‐coating and inkjet‐printing, and exhibited intense yellow PL emission in the solid state. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4083–4098, 2009 相似文献
158.
159.
160.
Andrew C. Benniston Dr. Graeme Copley Dr. Helge Lemmetyinen Dr. Nikolai V. Tkachenko Dr. 《Chemphyschem》2010,11(8):1685-1692
Two series of geometrically‐related dyads are discussed based on the difluoroborondipyrromethene (Bodipy) unit, and incorporating covalently attached hydroquinone/quinone groups. These units are anchored directly, or via a phenylene spacer, to the Bodipy core at the meso position in one series ( BD‐MHQ , BD‐MQ , BD‐MPHQ , BD‐MPQ ), but for the second series the attachment site is the 2‐position ( BD‐SHQ , BD‐SQ , BD‐SPHQ , BD‐SPQ ). The compounds show various levels of fluorescence depending on the oxidation state of the appended group and the substitution pattern. In non‐polar solvents such as toluene, diethyl ether and dichlorobenzene, the S1 state deactivation of the Bodipy unit in BD‐SPQ and BD‐MPQ is dominated by 1, 3exciplex formation, which has not been reported for Bodipy derivatives so far. In the latter molecule, the decay of the exciplex is divided between population of the Bodipy triplet state (13 %–21 %) and ground state reformation. This partitioning is not seen for the side‐on substituted derivative, BD‐SPQ , and only ground state reformation is observed following decay of the exciplex. This difference in behavior is explained by the radical‐pair inter‐system‐crossing mechanism, which more effectively operates in BD‐MPQ because of the orthogonality of the donor‐acceptor units. In the more polar solvent CH3CN all the quinone derivatives show fast formation of the charge‐separated state (kCS) followed by slower charge recombination (kCR). The ratio kCS/kCR≤80. 相似文献