全文获取类型
收费全文 | 152篇 |
免费 | 4篇 |
国内免费 | 2篇 |
专业分类
化学 | 90篇 |
晶体学 | 1篇 |
力学 | 4篇 |
数学 | 17篇 |
物理学 | 31篇 |
无线电 | 15篇 |
出版年
2022年 | 4篇 |
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2015年 | 3篇 |
2014年 | 5篇 |
2013年 | 5篇 |
2012年 | 13篇 |
2011年 | 8篇 |
2010年 | 10篇 |
2009年 | 16篇 |
2008年 | 8篇 |
2007年 | 5篇 |
2006年 | 5篇 |
2005年 | 9篇 |
2004年 | 6篇 |
2003年 | 8篇 |
2002年 | 3篇 |
2001年 | 9篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1992年 | 2篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1978年 | 1篇 |
1910年 | 2篇 |
1904年 | 1篇 |
排序方式: 共有158条查询结果,搜索用时 359 毫秒
31.
Coclite Giuseppe Maria Dipierro Serena Maddalena Francesco Valdinoci Enrico 《Journal of Nonlinear Science》2020,30(4):1285-1305
The formation of singularities in finite time in nonlocal Burgers’ equations, with time-fractional derivative, is studied in detail. The occurrence of finite-time singularity is proved, revealing the underlying mechanism, and precise estimates on the blowup time are provided. The employment of the present equation to model a problem arising in job market is also analyzed.
相似文献32.
Pascal I. Binda Brittany R. Hill Brian W. Skelton 《Journal of Coordination Chemistry》2018,71(7):941-951
Four new sodium complexes of phenolate and bisphenolate ligands have been synthesized and characterized by NMR spectroscopy and X-ray crystallography to study their coordination chemistry. The monoanionic tridentate [ONN] phenolate ligand gave a dimeric compound [Na2L2] (2), which crystallized in the orthorhombic crystal system, where the sodium ions have four coordination environments. The dianionic tridentate [ONO] phenolate ligand gave a dimeric [Na2(LIH)2] (4) compound in the tetragonal crystal system. The sodium ions Na(1) and Na(1?) are four-coordinate both having a tetrahedral geometry with the O–Na–O angle being ca. 93°, the O^N^O ligand string comprising a tridentate ligand. Interestingly, despite the steric bulk of N(SiMe3)2, a mixture of compounds [NaL] (2) and NaN(SiMe3)2 was isolated as a dimeric structure [Na2L(N(SiMe3)2)]2 (5) crystallized in the monoclinic crystal system. Na(1) is four-coordinate bonding to the phenolic oxygen atom and two N atoms of the ligand L and the N of the N(SiMe3)2 ligand. The coordination around Na(1) is tetrahedrally distorted square planar with the ‘cis’ angles ranging from 75.11(4) to 117.40(5)° and the ‘trans’ angles being 140.87(4) and 154.82(5)°. Na(2) is three-coordinate, bonding to the two phenolate oxygen atoms and the N atom of the N(SiMe3)2 ligand. Na(2), however, is not coplanar with these atoms being displaced 0.42 Å from it. The coordination chemistry for 5 is very intriguing as the sodium ions have mixed four- and three-coordination numbers, probably due to the steric hindrance of the silylamide groups. 相似文献
33.
Giuseppe Chirico Prof. Maddalena Collini Prof. Laura D'Alfonso Prof. Franck Denat Prof. Yuri A. Diaz‐Fernandez Dr. Luca Pasotti Dr. Yoann Rousselin Dr. Nicolas Sok Dr. Piersandro Pallavicini Prof. 《Chemphyschem》2008,9(12):1729-1737
Potentiometric titrations, fluorescence versus pH titrations, dynamic light scattering and fluorescence polarization anisotropy studies demonstrate that inside the nanodimensioned Triton X‐100 micelles, 1‐pyrenecarboxylic acid, PCOO?, forms an apical complex with the Zn2+ cation encircled by a lipophilic cyclen ligand and hugely increasing its fluorescence. The ability of the Zn2+‐cyclen‐PCOO? complex plus its micellar container to act as a fluorescent sensor to evaluate the lipophilicity of molecular species is demonstrated on the fatty acid series CH3(CH2)xCOOH (x=0–16). At pH 7.4 a decrease in fluorescence is observed on the addition of fatty acids that is directly related to their chain length, that is, to their tendency to enter the micellar containers, where they dislocate PCOO? from the Zn2+ centre. The independent determination of fatty acid pKa values in the presence of Triton X‐100 micelles confirms that our fluorescent micellar device is capable of sensing their lipophilicity. 相似文献
34.
Hydroxycinnamic acids derivatives, monomeric and oligomeric flavan-3-ols, flavonols, and dihydrocalcones are four of the major polyphenolic groups found in apples leaves and peels. A simple extraction with minimal pre-treatment and a high-performance liquid chromatography-diode array detection determination are optimized and validated, in order to identify and quantitate the polyphenolic profile of leaves and peels of four apples varieties (Gala, Topaz, Golden Delicious, and Florina). The improved chromatographic method has led to better separation of some known polyphenols in a single course, and diode-array detection has been used for the previsional identification of some polyphenolic compounds not available as standards. Because the mobile phase and the chromatographic column are compatible with a mass spectrometer, this method could investigate the unknown flavanols, flavonols, hydrocinnamic acid derivatives, and chalcone-related compounds found in apple leaves and peel extracts analyzed. 相似文献
35.
Mohamad Sleiman Randy L. Maddalena Lara A. Gundel Hugo Destaillats 《Journal of chromatography. A》2009,1216(45):7899-7905
Tobacco-specific nitrosamines (TSNAs) are some of the most potent carcinogens in tobacco and cigarette smoke. Accurate quantification of these chemicals is needed to help assess public health risks. We developed and validated a specific and sensitive method to measure four TSNAs adsorbed to model surfaces and secondhand smoke (SHS) particles using gas chromatography–ion-trap tandem mass spectrometry. In an 18-m3 room-sized chamber, a smoking machine generated realistic concentrations of SHS that were actively sampled on Teflon-coated fiber glass (TCFG) filters, and passively sampled on cellulose substrates. A simple solid–liquid extraction protocol using methanol as solvent was successfully applied to both substrates with recoveries ranging from 85 to 115%. For each TSNA, tandem MS parameters were optimized and the major fragmentation pathways were elucidated. The method showed excellent performance, with a linear dynamic range from 2 to 1000 ng mL−1, low detection limits (S/N > 3) of 30–300 pg mL−1 and precision with experimental errors below 10% for all compounds. Moreover, no interfering peaks were observed, indicating a high selectivity of MS/MS without the need for a sample clean-up step. This method provides a suitable analytical tool to detect and quantify traces of TSNA in indoor environments polluted with SHS. 相似文献
36.
U. Coscia G. Ambrosone A. Ambrosio M. Ambrosio F. Bussolotti V. Carillo V. Grossi P. Maddalena M. Passacantando E. Perillo A. Raulo S. Santucci 《Solid State Sciences》2009,11(10):1806-1809
Structural, optical and electrical properties of multiwalled carbon nanotubes deposited by chemical vapour deposition at 750 °C on sapphire substrate have been investigated. The main results concern the photoconductivity measurements. The photocurrent induced by white light illumination is a linear function of either the bias voltage or the optical power density in wide ranges. The photoresponse increases from the near infrared to the ultraviolet region with decreasing the wavelength of the monochromatic incident radiation in the 325–850 nm range. The photoresponse is strongly correlated to the optical absorbance. The optical and photoconductivity properties explored in multiwalled carbon nanotube samples with relatively large area appear very interesting for the development of light sensors. 相似文献
37.
Maddalena Corsini Piero Zanello Renzo Cini Gabriella Tamasi 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(6):m219-m223
The title compound, [Cu(C10H9N2O)2] or [CuII(CYMB)2], (I), was obtained in an attempt to reduce trans‐bis(2‐{[3,5‐bis(trifluoromethyl)phenyl]iminomethyl}phenolato)copper(II), [Cu(TIMB)2], (II), with bis(pentamethylcyclopentadienyl)cobalt(II) [decamethylcobaltocene, Cp*2Co, (III)]. The molecular structure of (I) has the CuII centre located on an inversion centre of the C2/c space group. A density functional theory (DFT) analysis at the B3LYP/Lanl2dz(CuF);6‐31G**(CHNO) level performed in order to optimize the structures of the free ligands CYMB− and TIMB−, and the metal complexes [CuI/II(CYMB)2]−/0 and [CuI/II(TIMB)2]−/0, reproduced well the X‐ray diffraction structure and allowed us to infer the insertion of the cyanomethide anion on the 3,5‐bis(trifluoromethyl)phenyl system from an evaluation of the Mulliken atomic charges and the electronic energies. 相似文献
38.
S Piccinonna N Margiotta C Pacifico A Lopalco N Denora S Fedi M Corsini G Natile 《Dalton transactions (Cambridge, England : 2003)》2012,41(32):9689-9699
Geminal bisphosphonates (BPs), used in the clinic for the treatment of hypercalcaemia and skeletal metastases, have been also exploited for promoting the specific accumulation of platinum antitumor drugs in bone tissue. In this work, the platinum dinuclear complex [{Pt(en)}(2)(μ-AHBP-H(2))](+) (1) (the carbon atom bridging the two phosphorous atoms carrying a 2-ammonioethyl and a hydroxyl group, AHBP-H(2)) has been used as scaffold for the synthesis of a Pt(II) trinuclear complex, [{Pt(en)}(3)(μ-AHBP)](+) (2), and a Pt(IV) adamantane-shaped dinuclear complex featuring an oxo-bridge, [{Pt(IV)(en)Cl}(2)(μ-O)(μ-AHBP-H(2))](+) (3) (X-ray structure). Compound 2 undergoes a reversible, pH dependent, rearrangement with a neat switch point around pH = 5.4. Compound 3 undergoes a one-step electrochemical reduction at E(pc) = -0.84 V affording compound 1. Such a potential is far lower than that of glutathione (-0.24 V), nevertheless compound 3 can undergo chemical reduction to 1 by GSH, most probably through a different (inner-sphere) mechanism. In vitro cytotoxicity of the new compounds, tested against murine glioma (C6) and human cervix (HeLa) and hepatoma (HepG2) cell lines, has shown that, while the Pt(IV) dimer 3 is inactive up to a concentration of 50 μM, the two Pt(II) polynuclear compounds 1 and 2 have a cytotoxicity comparable to that of cisplatin with the trinuclear complex 2 generally more active than the dinuclear complex 1. 相似文献
39.
Dacarro G Cucca L Grisoli P Pallavicini P Patrini M Taglietti A 《Dalton transactions (Cambridge, England : 2003)》2012,41(8):2456-2463
A polyethylenimine (PEI) self-assembled monolayer (SAM) is prepared, capable of complexing silver and copper cations and of anchoring silver nanoparticles, exerting antibacterial activity against Escherichia coli and Staphylococcus aureus. Functionalized glassy surfaces have been fully characterized through spectroscopic techniques (UV-Vis spectroscopy, spectroscopic ellipsometry), atomic force microscopy imaging and quantitative Ag and Cu analysis (ICP optical emission spectroscopy). 相似文献
40.
Maddalena Cavicchioli 《Discrete Applied Mathematics》2012,160(7-8):1253-1256