全文获取类型
收费全文 | 723篇 |
免费 | 14篇 |
专业分类
化学 | 379篇 |
晶体学 | 3篇 |
力学 | 9篇 |
数学 | 134篇 |
物理学 | 212篇 |
出版年
2023年 | 6篇 |
2021年 | 9篇 |
2020年 | 8篇 |
2019年 | 10篇 |
2018年 | 10篇 |
2017年 | 9篇 |
2016年 | 18篇 |
2015年 | 19篇 |
2014年 | 47篇 |
2013年 | 83篇 |
2012年 | 35篇 |
2011年 | 17篇 |
2010年 | 21篇 |
2009年 | 12篇 |
2008年 | 25篇 |
2007年 | 17篇 |
2006年 | 14篇 |
2005年 | 9篇 |
2003年 | 12篇 |
2002年 | 17篇 |
2001年 | 12篇 |
2000年 | 8篇 |
1999年 | 8篇 |
1998年 | 14篇 |
1997年 | 7篇 |
1996年 | 7篇 |
1995年 | 8篇 |
1993年 | 9篇 |
1992年 | 8篇 |
1991年 | 7篇 |
1990年 | 12篇 |
1989年 | 16篇 |
1988年 | 9篇 |
1987年 | 11篇 |
1986年 | 11篇 |
1985年 | 6篇 |
1984年 | 11篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1981年 | 11篇 |
1980年 | 11篇 |
1979年 | 12篇 |
1978年 | 14篇 |
1977年 | 8篇 |
1976年 | 7篇 |
1975年 | 8篇 |
1974年 | 7篇 |
1973年 | 8篇 |
1972年 | 8篇 |
1970年 | 6篇 |
排序方式: 共有737条查询结果,搜索用时 0 毫秒
731.
The transport activity of a membrane protein, bilitranslocase (T.C. # 2.A.65.1.1), which acts as a transporter of bilirubin from blood to liver cells, was experimentally determined for a large set of various endogenous compounds, drugs, purine and pyrimidine derivatives. On these grounds, the structure-activity models were developed following the OECD principles of QSAR models and their predictive ability for new chemicals was evaluated. The applicability domain of the models was estimated by Euclidean distances criteria according to the applied modeling method. The selection of the most influential structural variables was an important stage in the adopted modeling methodology. The interpretation of selected variables was performed in order to get an insight into the mechanism of transport through the cell membrane via bilitranslocase. Validation of the optimized models was performed by a previously determined validation set. The classification model was build to separate active from inactive compounds. The resulting accuracy, sensitivity, and specificity were 0.73, 0.89, and 0.64, respectively. Only active compounds were used to develop a predictive model for bilitranslocase inhibition constants. The model showed good predictive ability; Root Mean Squared error of the validation set, RMS(V)=0.29 log units. 相似文献
732.
M. Humar M. Škarabot M. Ravnik S. Žumer I. Poberaj D. Babič I. Muševič 《The European physical journal. E, Soft matter》2008,27(1):73-79
We show that diffraction of visible light from 2D dipolar nematic colloidal crystals can be tuned electrically. When the external
electric field of ∼ 1V/μm is applied in a direction perpendicular to the plane of the 2D colloidal crystal, the induced strain
is highly anisotropic, and the inter-colloidal spacing changes by as much as 20% along one direction and ∼ 2% along the perpendicular
one. Although the speed of response is in the range of several seconds, this novel mechanism could provide interesting photonic
applications. 相似文献
733.
I. Živković V. P.S. Awana H. Berger 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(4):423-431
We have performed an investigation of the nonlinear magnetic response in ruthenocuprates. A negative, diverging-like peak
at the main magnetic transition TN in RuSr2
RECu2O8 (RE = Gd, Y) indicates a possible canted antiferromagnetic order. Another well defined feature above TN points to a blocking of superparamagnetic particles through the T-3 dependence of the third harmonic at higher temperatures. Below TN a nondiverging peak appears, which is strongly affected by the addition of 10% of Cu ions in the RuO2 planes. In RuSr2
RE
2-xCexCu2O10 the main magnetic transition TM is accompanied by two characteristic temperatures in the third harmonic of the ac susceptibility, in agreement with recent
studies from μSR and M?ssbauer spectroscopy. We find that the spin-spin correlation temperature is the same in both families
of ruthenocuprates. 相似文献
734.
Jonas Žurauskas Dr. Soňa Boháčová Dr. Shangze Wu Dr. Valeria Butera Simon Schmid Michał Domański Dr. Tomáš Slanina Dr. Joshua P. Barham 《Angewandte Chemie (International ed. in English)》2023,62(44):e202307550
Electron-deficient acridones and in situ generated acridinium salts are reported as potent, closed-shell photooxidants that undergo surprising mechanisms. When bridging acyclic triarylamine catalysts with a carbonyl group (acridones), this completely diverts their behavior away from open-shell, radical cationic, ‘beyond diffusion’ photocatalysis to closed-shell, neutral, diffusion-controlled photocatalysis. Brønsted acid activation of acridones dramatically increases excited state oxidation power (by +0.8 V). Upon reduction of protonated acridones, they transform to electron-deficient acridinium salts as even more potent photooxidants (*E1/2=+2.56–3.05 V vs SCE). These oxidize even electron-deficient arenes where conventional acridinium salt photooxidants have thusfar been limited to electron-rich arenes. Surprisingly, upon photoexcitation these electron-deficient acridinium salts appear to undergo two electron reductive quenching to form acridinide anions, spectroscopically-detected as their protonated forms. This new behaviour is partly enabled by a catalyst preassembly with the arene, and contrasts to conventional SET reductive quenching of acridinium salts. Critically, this study illustrates how redox active chromophoric molecules initially considered photocatalysts can transform during the reaction to catalytically active species with completely different redox and spectroscopic properties. 相似文献
735.
736.
UV-vis spectra of homopolymers and copolymers of 2-aminobenzoic acid (OAB) and 2-methoxyaniline (OMA) were analyzed in order to obtain information about the oxidation state and proton doping level of these polymers. Dimethyl sulfoxide (DMSO) was used as a solvent in which protonated forms of polyanilines are preserved and a mixture of N-methyl-2-pyrrolidone and triethylamine (0.5 %) as a solvent (NMP/TEA) in which polyanilines are assumed to be non-protonated. Polymers were prepared in the emeraldine salt form, externally doped with HCl. It was found that only external doping is eliminated in NMP/TEA while internal doping by carboxylate groups bound in OAB units remains operative. Since doped quinoid units do not contribute to the quinoid band (Q-band at 630 nm), the intensity ratio of the Q-band and benzenoid band (B-band at 320 nm) cannot be simply correlated with the oxidation state of poly(OMA-co-OAB) copolymers in contrast to poly(OMA) and polyaniline. Spectra of copolymers with less than 60 % of OMA units as well as those of poly(OAB) in DMSO and NMP/TEA are almost identical due to internal doping, which is proposed to lead to structures in which main-chain protons are coulombically bound with immobile carboxylate anions. In the spectra of copolymers with less than 60 % of OMA units, a well-resolved band occurs at 500 nm, which can be ascribed to alternating or close-to-alternating sequences of OMA and OAB units. 相似文献
737.
Dr. Matko Mužević Assoc. Prof. Dr. Igor Lukačević Ivan Kovač Dr. Davor Gracin Andreja Žužić Prof. Dr. Jelena Macan Asst. Prof. Dr. Maja Varga Pajtler 《Chemphyschem》2023,24(9):e202200837
Inorganic perovskite CaMnO was proposed as a substitution for the TiO anatase in electron transport layers of solar cells containing the hybrid perovskite CH NH PbI based on increased mobility of electrons and better optical matching. Due to a suitable band gap concerning the absorption of sunlight, we investigate the potential of CaMnO and similar manganite perovskites, where Ca is replaced by either Sr, Ba or La, as an absorber layer in inorganic perovskite solar cells. In this study, we have used optical measurements on the synthesized AMnO (A=Ca, Sr, Ba, La) samples to aid density functional theory calculations (DFT) in order to accurately simulate the electronic and optical properties of AMnO compounds and gauge their potential for the role of absorber layer. Both experimental measurements and theoretical calculations show suitable band gap of 1.1-1.5 eV, depending on the compound, and absorption coefficients of the order of cm in the visible part of the spectrum. 相似文献