全文获取类型
收费全文 | 10126篇 |
免费 | 1827篇 |
国内免费 | 1086篇 |
专业分类
化学 | 7128篇 |
晶体学 | 88篇 |
力学 | 590篇 |
综合类 | 66篇 |
数学 | 1154篇 |
物理学 | 4013篇 |
出版年
2024年 | 31篇 |
2023年 | 232篇 |
2022年 | 323篇 |
2021年 | 389篇 |
2020年 | 411篇 |
2019年 | 388篇 |
2018年 | 370篇 |
2017年 | 300篇 |
2016年 | 525篇 |
2015年 | 459篇 |
2014年 | 584篇 |
2013年 | 775篇 |
2012年 | 963篇 |
2011年 | 948篇 |
2010年 | 660篇 |
2009年 | 645篇 |
2008年 | 653篇 |
2007年 | 557篇 |
2006年 | 535篇 |
2005年 | 425篇 |
2004年 | 330篇 |
2003年 | 251篇 |
2002年 | 213篇 |
2001年 | 188篇 |
2000年 | 212篇 |
1999年 | 242篇 |
1998年 | 180篇 |
1997年 | 182篇 |
1996年 | 198篇 |
1995年 | 153篇 |
1994年 | 128篇 |
1993年 | 100篇 |
1992年 | 107篇 |
1991年 | 60篇 |
1990年 | 75篇 |
1989年 | 55篇 |
1988年 | 28篇 |
1987年 | 29篇 |
1986年 | 40篇 |
1985年 | 39篇 |
1984年 | 14篇 |
1983年 | 18篇 |
1982年 | 8篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1957年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
901.
Wenping Wang Hengming Cao Guojun Zhu Peng Wang 《Journal of polymer science. Part A, Polymer chemistry》2010,48(8):1782-1790
A core‐shell hybrid nanocomposites, possessing a hard core of nano titanium dioxide (n‐TiO2) and a soft shell of brushlike polystyrene (PS), were successfully prepared by surface‐initiated atom transfer radical polymerization (ATRP) at 90 °C in anisole solution using CuBr/PMDETA as the catalyst, in the presence of sacrificial initiator. FTIR, 1H NMR, XPS, TEM, SEM, TGA, and DSC were used to determine the chemical structure, morphology, thermal properties, and the grafted PS quantities of the resulting products. TEM images of the samples provided direct evidence for the formation of a core‐shell structure. The thermal stabilities of the grafted polymers were dramatically elevated relative to that of pristine PS according to TGA results. DSC results demonstrated that the TiO2‐PS nanocomposites exhibited higher glass transition temperature (Tg) compared with pristine PS. The molecular weights of the free polymers formed by sacrificial initiator, which were similar to that of surface‐attached polymers were measured by GPC instrument which showed that the molecular weights of PS were well controlled with a relatively narrow polydispersity index (PDI < 1.2). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1782–1790, 2010 相似文献
902.
903.
Various analytic approaches have been developed to solve the famous Landau-Zener (LZ) problem. Here, we introduce a time-evolution operator method to investigate such a problem by numerically solving the induced algebraic equations (by Runge-Kutta method). Based on these calculations, transitions between two levels driven by various time-dependent external fields can be simulated in detail, typically near the so-called avoided crossing points. Far from these points, our results reduce to the original Landau-Zener transition (LZT). 相似文献
904.
Jinming LiuXiaoru Zhao Libing DuanMengmeng Cao Huinan SunJifeng Shao Shuai ChenHaiyan Xie Xiao ChangChangle Chen 《Applied Surface Science》2011,257(23):10156-10160
Nb-doped TiO2 (TNO) thin films were prepared by sol-gel dip-coating method with Nb content in a wide range of 0-20 at.%. The prepared films were preheated at 400 °C and then undertaken by two different post-annealing processes: (a) three times vacuum annealing and (b) multi-round annealing. The designed multi-round annealing was shown to be an effective way to improve the conductive properties of the films, compared to the traditional vacuum annealing process. The minimum resistivity reached approximately 0.5 Ω cm with Nb doping concentration around 12 at.%, and the carrier density increased with Nb-doping concentration until the critical point of 12 at.%, which might be the optimal doping content for our TNO films prepared by sol-gel method. 相似文献
905.
906.
Using the mixed monotone method we establish existence and uniqueness results for a singular integral equation. The theorem
obtained is very general and complements previous known results.
The work was supported by the National Natural Science Foundation of China (No.10571021 and No.10701020) and Key Laboratory
for Applied Statistics of MOE(KLAS) and Subject Foundation of Harbin University (No. HXK200714). 相似文献
907.
The interfacial structure between the room-temperature ionic liquid, 1-butyl-3-methyl-imidazolium hexafluorophosphate (BMIM+/PF6-) and rutile (110) surface is simulated by classical molecular dynam-ics simulation, aiming to model a crucial constituent of the electrolyte/semiconductor interface. The simulation results show several enhanced layers forming in the interfacial region, especially for the anions. A well ordered double layering structure of the ions is also observed in the interfacial region. The c... 相似文献
908.
W. S. Andrews E. J. Waller P. Brousseau G. Roy X. Cao K. A. M. Creber L. S. Erhardt 《Journal of Radioanalytical and Nuclear Chemistry》2009,282(3):919-922
During the past decade, interest has increased in qualifying and quantifying the threat posed to the public by the illegal
use of radionuclides. In order to take investigations beyond the laboratory bench into more realistic scenarios, environmental
and safety considerations dictate that these studies be performed on stable and benign surrogates. This paper discusses some
of these studies, specifically the use of cerium dioxide for actinide ceramics and calcium and natural strontium ceramics
for those based on 90Sr. 相似文献
909.
Yunhua Xu Rong Guan Jiaxing Jiang Wei Yang Hongyu Zhen Junbiao Peng Yong Cao 《Journal of polymer science. Part A, Polymer chemistry》2008,46(2):453-463
A new strategy to realize efficient white‐light emission from a binary fluorene‐based copolymer (PF‐Phq) with the fluorene segment as a blue emitter and the iridium complex, 9‐iridium(III)bis(2‐(2‐phenyl‐quinoline‐N,C3′)(11,13‐tetradecanedionate))‐3,6‐carbazole (Phq), as a red emitter has been proposed and demonstrated. The photo‐ and electroluminescence properties of the PF‐Phq copolymers were investigated. White‐light emission with two bands of blue and red was achieved from the binary copolymers. The efficiency increased with increasing concentration of iridium complex, which resulted from its efficient phosphorescence emission and the weak phosphorescent quenching due to its lower triplet energy level than that of polyfluorene. In comparison with the binary copolymer, the efficiency and color purity of the ternary copolymers (PF‐Phq‐BT) were improved by introducing fluorescent green benzothiadiazole (BT) unit into polyfluorene backbone. This was ascribed to the exciton confinement of the benzothiadiazole unit, which allowed efficient singlet energy transfer from fluorene segment to BT unit and avoided the triplet quenching resulted from the higher triplet energy levels of phosphorescent green emitters than that of polyfluorene. The phosphorescence quenching is a key factor in the design of white light‐emitting polyfluorene with triplet emitter. It is shown that using singlet green and triplet red emitters is an efficient approach to reduce and even avoid the phosphorescence quenching in the fluorene‐based copolymers. The strategy to incorporate singlet green emitter to polyfluorene backbone and to attach triplet red species to the side chain is promising for white polymer light‐emitting diodes. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 453–463, 2008 相似文献
910.
Cao‐Yuan Niu Xian‐Fu Zheng Ling‐Ling Bai Xiao‐Ling Wu Chun‐Hong Kou 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(9):m305-m307
This study presents new coordinating modes of a Schiff base with three coordinating groups and an interesting two‐dimensional framework based on two types of constructing units. In the title compound, {[Ag(C14H10N4O)]ClO4}n, the AgI ion is coordinated by three N atoms and one O atom from three different N′‐(4‐cyanobenzylidene)isonicotinohydrazide (L) ligands, forming a primary distorted square‐planar coordination geometry. Two ligands each bridge two metal centres through one carbonitrile N atom in a monodentate mode and the hydrazide N and O atoms in a bidentate mode to form a small centrosymmetric (2+2)‐Ag2L2 ring as a principal constructing unit. The pyridyl N atoms from four ligands in four of these small rings coordinate to Ag atoms in adjacent rings to form a large hexanuclear silver grid. A two‐dimensional framework of rectangular grids is constructed from these small rings and large grids. Two perchlorate anions are located in each large grid and are bound to the grid by N—H...O hydrogen bonding. Crosslinking between the layers is achieved through long Ag...O interactions between the perchlorate anions and Ag atoms in adjacent layers. 相似文献