全文获取类型
收费全文 | 506篇 |
免费 | 38篇 |
国内免费 | 4篇 |
专业分类
化学 | 402篇 |
晶体学 | 5篇 |
力学 | 19篇 |
数学 | 36篇 |
物理学 | 86篇 |
出版年
2024年 | 2篇 |
2023年 | 8篇 |
2022年 | 18篇 |
2021年 | 27篇 |
2020年 | 32篇 |
2019年 | 32篇 |
2018年 | 37篇 |
2017年 | 36篇 |
2016年 | 49篇 |
2015年 | 25篇 |
2014年 | 22篇 |
2013年 | 69篇 |
2012年 | 35篇 |
2011年 | 35篇 |
2010年 | 24篇 |
2009年 | 24篇 |
2008年 | 18篇 |
2007年 | 15篇 |
2006年 | 8篇 |
2005年 | 4篇 |
2004年 | 5篇 |
2003年 | 1篇 |
2002年 | 3篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有548条查询结果,搜索用时 15 毫秒
61.
The reactive 1:1 intermediate produced in the reaction between isocyanides and dialkyl acetylenedicarboxylates was trapped with 1,2-diacylhydrazines to yield highly functionalized pyrazoles in good yields. 相似文献
62.
Danika Locatelli Silvio Quici Stefania Righetto Dominique Roberto Francesca Tessore Geoffrey J. Ashwell Mukhtar Amiri 《Progress in Solid State Chemistry》2005,33(2-4):223-232
The new ligands (E)-4-[2-(4-(N-methyl-N-hexadecylaminophenyl)ethenyl]pyridine (L1) and 4′-(C6H4-p-N(Me)(hexadecyl))-2,2′:6′,2″-terpyridine (L2) were prepared along with their complexes [cis-Ir(CO)2ClL1], [fac-Os(CO)3Cl2L1], [ZnCl2L2] and [IrCl3L2]. Whereas these complexes show a large second-order nonlinear optical (NLO) response at the molecular level, similar to that of related organic alkylated salts as evidenced by the Electric Field Induced Second-Harmonic (EFISH) generation technique, their Langmuir–Blodgett (LB) film susceptibility is lower than that of the salts. 相似文献
63.
An efficient and highly chemoselective synthesis of symmetrical secondary amines via reductive amination of aldehydes with inexpensive and commercially available HMDS and sodium borohydride in high to quantitative yields is reported. 相似文献
64.
A technique for measuring absorption from excited states with nanosecond lifetimes utilizing pulsed tunable dye laser probes is described. The method features a simple experimental set-up, and high signal-to-noise ratio. The excited singlet state absorption spectrum of one transition in acridine red is presented. 相似文献
65.
Human serum albumin consists of a single polypeptide of 585 amino acid residues with 1 Trp residue. In the present work, we
measured fluorescence lifetimes of the protein in both native and denatured states. The results indicate that Trp emission
occurs with three lifetimes in both states. Lifetimes values and contribution to the global emission decay differ between
the two states. Data are interpreted as the results of an emission occurring from three substructures of the tryptophan formed
in the excited state. Two of these substructures are already present for the tryptophan free in solution. The third lifetime
is the result of the interaction between the tryptophan residue and surrounding microenvironment. The populations of these
substructures characterized by the pre-exponential parameters of the fluorescence lifetimes are dependent on the fluorophore
microenvironment and on the global protein structure. 相似文献
66.
Saeid Amiri Bertrand S. Clarke Jennifer L. Clarke 《Journal of computational and graphical statistics》2018,27(1):195-208
We present a technique for clustering categorical data by generating many dissimilarity matrices and combining them. We begin by demonstrating our technique on low-dimensional categorical data and comparing it to several other techniques that have been proposed. We show through simulations and examples that our method is both more accurate and more stable. Then we give conditions under which our method should yield good results in general. Our method extends to high-dimensional categorical data of equal lengths by ensembling over many choices of explanatory variables. In this context, we compare our method with two other methods. Finally, we extend our method to high-dimensional categorical data vectors of unequal length by using alignment techniques to equalize the lengths. We give an example to show that our method continues to provide useful results, in particular, providing a comparison with phylogenetic trees. Supplementary material for this article is available online. 相似文献
67.
For a finite group G, let ψ(G) denote the sum of element orders of G. The aim of this article is to show that ψ(H) < ψ(A n ) for every proper subgroup H of the symmetric group of degree n, which is different from the alternating group A n . 相似文献
68.
Seyyed Majid Jafarian Amiri 《代数通讯》2013,41(6):2055-2059
69.
Meisam Amiri Vahid Esfahanian Mohammad Reza Hairi-Yazdi Mohsen Esfahanian Amir Mohammad Fazeli Ali Nabi 《Mathematical and Computer Modelling of Dynamical Systems: Methods, Tools and Applications in Engineering and Related Sciences》2013,19(2):191-207
With the stricter limitations on both fuel consumption and air pollution, the advantages of a hybrid electric vehicle are becoming more evident than ever. In the present study, an energy management system for a hybrid electric vehicle is developed. Because the plant under consideration is nonlinear, multi-domain, time-varying, has multiple uncertainties and, in addition, the designed control strategy must be able to obey the driver's commands and achieve the par-internship for a new generation of vehicle regulations, the fuzzy logic approach is chosen. A feed-forward hybrid vehicle simulation model is used to demonstrate the validity and the convenience of the current approach and its results have been compared with the other parallel hybrid electric vehicle control strategies. Simulation results show considerable improvement in the efficiency of the internal combustion engine and, consequently, fuel consumption and acceleration performances. 相似文献
70.
Aboubacar Amiri 《Statistical Inference for Stochastic Processes》2013,16(2):81-96
The main purpose of this paper is to estimate the regression function by using a recursive nonparametric kernel approach. We derive the asymptotic normality for a general class of recursive kernel estimate of the regression function, under strong mixing conditions. Our purpose is to extend the work of Roussas and Tran (Ann Stat 20:98–120, 1992) concerning the Devroye–Wagner estimate. 相似文献