全文获取类型
收费全文 | 212篇 |
免费 | 14篇 |
专业分类
化学 | 148篇 |
晶体学 | 1篇 |
力学 | 8篇 |
数学 | 26篇 |
物理学 | 43篇 |
出版年
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 6篇 |
2020年 | 6篇 |
2019年 | 2篇 |
2018年 | 7篇 |
2017年 | 8篇 |
2016年 | 10篇 |
2015年 | 13篇 |
2014年 | 15篇 |
2013年 | 14篇 |
2012年 | 10篇 |
2011年 | 14篇 |
2010年 | 20篇 |
2009年 | 11篇 |
2008年 | 16篇 |
2007年 | 10篇 |
2006年 | 13篇 |
2005年 | 6篇 |
2004年 | 5篇 |
2003年 | 11篇 |
2002年 | 4篇 |
2001年 | 6篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1988年 | 1篇 |
排序方式: 共有226条查询结果,搜索用时 31 毫秒
91.
Serbest Kerim Karaböcek Serdar Değirmencioğlu İsmail Güner Saadettin Kormali Fatma 《Transition Metal Chemistry》2001,26(4-5):375-379
A new ligand incorporating a dioxime moiety, 3-{2-[2-(2-hydroxyimino-1-methylpropylideneamino)ethylamino]ethylimino}butan-2-one oxime, (H2mdo), has been synthesized and its mono-, di- and trinuclear copper(II), and hetero-dinuclear copper(II)–manganese(II) complexes have been prepared and characterized by elemental analyses, magnetic moments, 1H- and 13C-n.m.r., i.r. and mass spectral studies. A mononuclear copper(II) complex of H2mdo was found to have a 1:1 metal:ligand ratio. Elemental analyses, stoichiometric and spectroscopic data of the metal complexes indicated that the metal ions are coordinated to the oxime and imine nitrogen atoms (C=N); the data support the proposed structure of H2mdo and its complexes. 相似文献
92.
Serbest Kerim Değirmencioğlu İsmail Karaböcek Serdar Güner Saadettin 《Transition Metal Chemistry》2001,26(1-2):232-236
A new binucleating ligand incorporating four oxime groups, butane-2,3-dione O-[4-aminooxy-2,3-bis-(2-hydroxyimino-1-methyl-propylideneaminooxymethyl)-but-2-enyl]-dioxime, (H4mto), has been synthesized and its dinuclear cobalt(III), copper(II), and homo- and hetero-tetranuclear copper(II)–manganese(II) complexes have been prepared and characterized by 1H- and 13C-n.m.r., i.r., magnetic moments and mass spectral studies. Elemental analyses, stoichiometric and spectroscopic data indicate that the metal ions in the complexes are coordinated to the oxime nitrogen atoms (C=N) and the data support the proposed structure for H4mto and its complexes. Moreover, dinuclear cobalt(III) and copper(II) complexes of H4mto have a 2:1 metal:ligand ratio. 相似文献
93.
The constitutive theories intended to quantitatively account for the complicated material response exhibited by polymers include, in general, adjustable material parameters. These must be identified from experimental data obtained from the material under consideration. This contribution presents the complete procedure studying the behavior of polymers at large strains in three basic steps: i) Accomplishment of homogeneous and 3-D inhomogeneous experiments under different deformation conditions. ii) Identification of the material parameters of a constitutive model by means of gradient–based optimization methods with respect to the homogeneous experimental data. iii) Validation of the identified material parameters by comparing 3-D FE simulations to the inhomogeneous experimental data. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
94.
Reaching a control on the mesoscopic morphology and internal molecular arrangement of cyanine aggregates is an important step for realization of devices with tailor-made optical properties. Despite a wealth of research, understanding of the relationship between molecular organization, excitonic states and dynamics of aggregates is still preliminary. To this end, we have employed polarized absorption spectroscopy to investigate the relationship between internal molecular organization and excitonic states of J-aggregates in 1,1′,3,3′tetraethyl-5,5′,6,6′-tetrachlorobenzimidazolocarbocyanine (TTBC) thin films in poly-vinyl alcohol (PVA). Angular dependence of the UV–vis spectra has been measured at 11 different orientations between the electric field polarization and the macroscopic alignment axis. Aggregate spectral response consisted of an asymmetrically split Davydov pair of bands exhibiting opposite polarization: an H-band (505 nm, Lorentzian-like, polarized along the macroscopic film axis) and a J-band (594 nm, one-dimensional J-aggregate like band shape, polarized perpendicular to the macroscopic film axis). The polarized absorption observations were found to be consistent with a herringbone model for which the internal molecular arrangement, the excited state structure and dynamics have recently been detailed by us upon interpretation of isotropic absorption data in ionic aqueous solution. 相似文献
95.
Basu and Basu (Statistica Sinica 8:841–860, 1998) have proposed an empty cell penalty for the minimum power-divergence estimators
which can lead to improvements in the small sample properties of these estimators. In this paper, we study the small and moderate
sample performances of the ordinary and penalized minimum power-divergence estimators in terms of efficiency and robustness
for the log-linear models in two-way contingency tables under the assumptions of multinomial sampling. Calculations made by
enumerating all possible sample combinations show that the penalized estimators are competitive with the ordinary estimators
for the moderate samples and definitely better for the smallest sample considered for both efficiency and robustness under
the considered models. The results also reveal that the bigger the main effects the more need for penalization. 相似文献
96.
Ismail Serdar Bakal Joseph Geunes H. Edwin Romeijn 《Journal of Global Optimization》2008,41(4):633-657
In the majority of classical inventory theory literature, demand arises from exogenous sources upon which the firm has little
or no control. In many practical contexts, however, aggregate demand is comprised of individual demands from a number of distinct
customers or markets. This introduces new dimensions to supply chain planning problems involving the selection of markets
or customers to include in the demand portfolio. We present a nonlinear, combinatorial optimization model to address planning
decisions in both deterministic and stochastic settings, where a firm constructs a demand portfolio from a set of potential
markets having price-sensitive demands. We first consider a pricing strategy that dictates a single price throughout all markets
and provide an efficient algorithm for maximizing total profit. We also analyze the model under a market-specific pricing
policy and describe its optimal solution. An extensive computational study characterizes the effects of key system parameters
on the optimal value of expected profit, and provides some interesting insights on how a given market’s characteristics can
affect optimal pricing decisions in other markets. 相似文献
97.
Derya Gülcemal Milena Masullo Ozgen Alankuş‐Çalışkan Tamer Karayıldırım Serdar G. Şenol Sonia Piacente Erdal Bedir 《Magnetic resonance in chemistry : MRC》2010,48(3):239-243
A new secondary metabolite, pterocephaline, along with the known cantleyoside, 7α‐morroniside, 3β,5α‐tetrahydrodesoxycordifoline lactam, 5S‐5‐carboxyvincoside, sweroside, and loganin have been isolated from the aerial parts of P. pinardii (Dipsacaceae). Moreover, cantleyoside‐methyl‐hemiacetal and cantleyoside‐dimethyl‐acetal were obtained as seco‐iridoid artifacts. The structures were elucidated by extensive spectroscopic methods including 1D‐(1H, 13C and TOCSY) and 2D‐NMR (DQF‐COSY, HSQC and HMBC). Monoterpenoid glucoindole alkaloids were encountered for the first time in Dipsacaceae family. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
98.
M. Serdar Çavu? 《Journal of Non》2011,357(1):202-205
In this paper, we begin introducing some basic definitions and mathematical preliminaries of the fractional calculus theory. By using the fractional calculus technique (that is, calculus of derivatives and integrals of any arbitrary real or complex order) a solution of the fractional master equation derived from the stochastic Ising model of Glauber has been obtained and the result is applied to an analysis of the dielectric relaxation processes. From the solution of the equation, the Cole-Cole dispersion relation, KWW (Kohlrausch-William-Watts) equation and algebraic decay relaxation functions are obtained easily. Then these functions are compared with Bozdemir's earlier analysis of the stochastic Ising model. 相似文献
99.
We report on the determination of choline and acetylcholine via biocentrivoltammetry. This method combines centrifugation and voltammetry and is based on a carbon paste electrode modified with acetylcholinesterase and choline oxidase. The electrode was placed at the bottom of a biocentrivoltammetric cell. Acetylcholine and choline are accumulated on the enzyme electrode via centrifugative forces, upon which a direct voltammetric scan is applied. Reaction time, pH values, quantities of enzyme and centrifugation parameters were optimized. A linear response is obtained in the 0.07 to 10?μM concentration range of acetylcholine, and a limit of detection as low as 0.5?μM. The linear range is between 0.1 and 500?μM for choline. The method was applied to the determination of acetylcholine and choline in spiked serum samples. Figure
This work constitutes the first application of biocentri-voltammetry for ACh detection. Biocentri-voltammetry is the method where centrifuge and voltammetry is combined in a specially designed working cell. As a result, sensitive and effective biosensor was obtained. 相似文献
100.
In this study, SnO2 nanoparticles (SNPs)-poly(vinylferrocenium) (PVF+) modified single-use graphite electrodes were developed for electrochemical monitoring of DNA hybridization. The surfaces of polymer modified and polymer-SNP modified pencil graphite electrodes (PGEs) were firstly characterized by using SEM analysis. The electrochemical behaviours of these electrodes were also investigated using the differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) techniques. The polymer-SNP modified PGEs were then tested for the electrochemical sensing of DNA based on the changes at the guanine oxidation signals. Experimental parameters, such as; different modifications in DNA oligonucleotides, DNA probe concentrations were examined to obtain more sensitive and selective electrochemical signals for nucleic acid hybridization. After optimization studies, DNA hybridization was investigated in the case of complementary of hepatitis B virus (HBV) probe, mismatch (MM), and noncomplementary (NC) sequences. 相似文献