全文获取类型
收费全文 | 510篇 |
免费 | 21篇 |
国内免费 | 7篇 |
学科分类
数理化 | 538篇 |
出版年
2022年 | 5篇 |
2021年 | 7篇 |
2020年 | 8篇 |
2019年 | 6篇 |
2018年 | 4篇 |
2016年 | 12篇 |
2015年 | 10篇 |
2014年 | 20篇 |
2013年 | 38篇 |
2012年 | 28篇 |
2011年 | 32篇 |
2010年 | 24篇 |
2009年 | 27篇 |
2008年 | 33篇 |
2007年 | 20篇 |
2006年 | 26篇 |
2005年 | 16篇 |
2004年 | 19篇 |
2003年 | 19篇 |
2002年 | 24篇 |
2001年 | 24篇 |
2000年 | 16篇 |
1999年 | 4篇 |
1998年 | 7篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 8篇 |
1994年 | 7篇 |
1993年 | 11篇 |
1992年 | 8篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 6篇 |
1986年 | 5篇 |
1985年 | 9篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1978年 | 2篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1969年 | 2篇 |
1968年 | 1篇 |
排序方式: 共有538条查询结果,搜索用时 12 毫秒
81.
Phosphorescent Cyclometalated Iridium(III) Complexes That Contain Substituted 2‐Acetylbenzo[b]thiophen‐3‐olate Ligand for Red Organic Light‐Emitting Devices 下载免费PDF全文
Chen Yang Dr. Shiu‐Lun Lai Dr. Sharon Lai‐Fung Chan Dr. Kam‐Hung Low Dr. Gang Cheng Kwan‐Ting Yeung Dr. Chi‐Chung Kwok Prof. Dr. Chi‐Ming Che 《化学:亚洲杂志》2014,9(12):3572-3585
We report the synthesis of a new class of thermally stable and strongly luminescent cyclometalated iridium(III) complexes 1 – 6 , which contain the 2‐acetylbenzo[b]thiophene‐3‐olate (bt) ligand, and their application in organic light‐emitting diodes (OLEDs). These heteroleptic iridium(III) complexes with bt as the ancillary ligand have a decomposition temperature that is 10–20 % higher and lower emission self‐quenching constants than those of their corresponding complexes with acetylacetonate (acac). The luminescent color of these iridium(III) complexes could be fine‐tuned from orange (e.g., 2‐phenyl‐6‐(trifluoromethyl)benzo[d]thiazole (cf3bta) for 4 ) to pure red (e.g., lpt (Hlpt=4‐methyl‐2‐(thiophen‐2‐yl)quinolone) for 6 ) by varying the cyclometalating ligands (C‐deprotonated C^N). In particular, highly efficient OLEDs based on 6 as dopant (emitter) and 1,3‐bis(carbazol‐9‐yl)benzene (mCP) as host that exhibit stable red emission over a wide range of brightness with CIE chromaticity coordinates of (0.67, 0.33) well matched to the National Television System Committee (NTSC) standard have been fabricated along with an external quantum efficiency (EQE) and current efficiency of 9 % and 10 cd A?1, respectively. A further 50 % increase in EQE (>13 %) by replacing mCP with bis[4‐(6H‐indolo[2,3‐b]quinoxalin‐6‐yl)phenyl]diphenylsilane (BIQS) as host for 6 in the red OLED is demonstrated. The performance of OLEDs fabricated with 6 (i.e., [(lpt)2Ir(bt)]) was comparable to that of the analogous iridium(III) complex that bore acac (i.e., [(lpt)2Ir(acac)]; 6 a in this work) [Adv. Mater. 2011 , 23, 2981] fabricated under similar conditions. By using ntt (Hnnt=3‐hydroxynaphtho[2,3‐b]thiophen‐2‐yl)(thiophen‐2‐yl)methanone) ligand, a substituted derivative of bt, the [(cf3bta)2Ir(ntt)] was prepared and found to display deep red emission at around 700 nm with a quantum yield of 12 % in mCP thin film. 相似文献
82.
A new continuous-flow gradient-elution micellar electrokinetic capillary chromatography method is developed for the determination of airborne carbonyls after derivatization with 2,4-dinitrophenylhydrazine. A total of 16 carbonyls can be determined with detection limits ranging from 0.94 to 8.50 mg/L, working range from 4.72 to 346 mg/L, and repeatabilities (relative standard deviation, n=5) from 1.23 to 4.6% or 3.93 to 7.6% for migration time and peak area, respectively. Coupling with denuder-filter sampling, a preliminary survey has been conducted to determine gaseous and particulate carbonyls from air sampled at a roadside station. The method is shown to have sufficient sensitivity for 1-h sampling of ambient carbonyls with detection limits ranging from 0.045 to 1.2 microg/m3 and working range from 0.11 to 43.3 microg/m3 at a flow rate of 10 Lpm. The method requires minimal modification of commercially available capillary electrophoresis equipment and can differentiate gaseous and particulate carbonyls to provide essential information and objective data for adopting effective measures to combat the discharge of carbonyl compounds to the atmosphere. 相似文献
83.
84.
X射线辐照前后,在BaF(Cl,Br):Sm^2+中以560nm的Nd:YAG脉冲光在液氮温度下进行了双光子烧孔实验和光激励发光实验,结果表明,Sm^2+掺杂的碱土金属氟卤化物光谱烧孔过程中伴随着光激励发光过程,这一过程直接影响光谱烧孔过程的进行。 相似文献
85.
Kevin Kam Fung Yuen 《Fuzzy Optimization and Decision Making》2014,13(1):105-130
Group decision making is the process to explore the best choice among the screened alternatives under predefined criteria with corresponding weights from assessment of a group of decision makers. The Fuzzy TOPSIS taking an evaluated fuzzy decision matrix as input is a popular tool to analyze the ideal alternative. This research, however, finds that the classical fuzzy TOPSIS produces a misleading result due to some inappropriate definitions, and proposes the rectified fuzzy TOPSIS addressing two technical problems. As the decision accuracy also depends on the evaluation quality of the fuzzy decision matrix comprising rating scores and weights, this research applies compound linguistic ordinal scale as the fuzzy rating scale for expert judgments, and cognitive pairwise comparison for determining the fuzzy weights. The numerical case of a robot selection problem demonstrates the hybrid approach leading to the much reliable result for decision making, comparing with the conventional fuzzy Analytic Hierarchy Process and TOPSIS. 相似文献
86.
生物力学与基因-献给周培源教授诞辰100周年 总被引:1,自引:0,他引:1
生物界包罗万象,其中有力的作用,所以有生物力学.自Galileo,Harvey, Boreli, Hooke, Euler,Young等创始以来,生物力学阐明了鸟飞鱼游,人体运动,血液循环,人工脏器等,对人世社会,有所贡献.生物力学的基础是质点力学,传统地用连续体力学的概念来简化.但近年做生物组织在应力的作用下改造的问题,引起了必须更改传统连续体力学的几个公理的问题.我们将仔细讨论这些公理,然后指出新公理存在的理由,是由于基因在细胞里的日常工作.基因不单主宰遗传,变异;并且忙着控制日常生活.不过,现在仅见其端倪.详细的情形,要等将来来阐发了. 相似文献
87.
(WO3)0.15(BiO1.5)0.85 exhibits a tetragonal structure derived from the fluorite subcell. The electrical conductivity of (WO3)0.15(BiO1.5)0.85 is lower than that of Y2O3-doped Bi2O3. The structure and electrical conductivity of samples formulated as (YO1.5)
x
(WO3)0.15(BiO1.5)0.85-
x
(x = 0.1, 0.2, 0.3, and 0.4) were investigated. The as-sintered (YO1.5)0.1(WO3)0.15(BiO1.5)0.75 exhibited a single cubic structure that is isostructural with δ-Bi2O3. For x = 0.2, 0.3, and 0.4, the as-sintered samples consisted of a cubic fluorite structure and rhombohedral Y6WO12. After heat treatment at 600 °C for 200 h, the cubic structures are stable for x = 0.1, 0.3, and 0.4. A transformation from cubic to rhombohedral phase after heat treatment at 600 °C for 200 h was observed
in the sample originally formulated as (YO1.5)0.2(WO3)0.15(BiO1.5)0.65. 相似文献
88.
89.
Synthesis and thermal properties of mesomorphic 1,1'-bis[ω-(4'-cyano-4-biphenyloxy)alkyl] ferrocenes
A new series of 1,1'-disubstituted ferrocene compounds of the type [(η5-C5H4(CH2)nOC6H4C6H4CN]2Fe (3a-d, n = 5, 6, 8, 11) incorporating a variable length alkyloxy cyanobiphenyl unit has been prepared and their mesomorphic properties have been investigated. Compounds 3b, c and d exhibit a thermotropic smectic C phase and 3c also exhibits a monotropic smectic A phase over a fairly wide range near ambient temperature. 相似文献
90.
A new technique has been developed to compute mean and fluctuating concentrations in complex turbulent flows. An initial distribution of material is discretised into any small clouds which are advected by a combination of the mean flow and large scale turbulence. The turbulence can be simulated either by Kinematic Simulation or by a stochastic model for the motion of each cloud centroid. The clouds also diffuse relative to their centroids; the statistics for this are obtained from a separate calculation of the growth of individual clouds in small scale turbulence, generated by Kinematic Simulation. The ensemble of discrete clouds is periodically rediscretised, to limit the size of the small clouds and prevent overlapping. The model is illustrated with simulations of dispersion in uniform flow and in a coastal flow, and the results are compared with analytic, steady state solutions where available. 相似文献