全文获取类型
收费全文 | 341篇 |
免费 | 11篇 |
国内免费 | 2篇 |
专业分类
化学 | 144篇 |
晶体学 | 9篇 |
力学 | 8篇 |
数学 | 50篇 |
物理学 | 143篇 |
出版年
2022年 | 6篇 |
2021年 | 4篇 |
2020年 | 6篇 |
2019年 | 6篇 |
2018年 | 5篇 |
2017年 | 9篇 |
2016年 | 14篇 |
2015年 | 7篇 |
2014年 | 11篇 |
2013年 | 18篇 |
2012年 | 17篇 |
2011年 | 33篇 |
2010年 | 29篇 |
2009年 | 12篇 |
2008年 | 18篇 |
2007年 | 14篇 |
2006年 | 22篇 |
2005年 | 5篇 |
2004年 | 15篇 |
2003年 | 8篇 |
2002年 | 12篇 |
2001年 | 5篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 8篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1988年 | 3篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1982年 | 7篇 |
1976年 | 3篇 |
1968年 | 2篇 |
1967年 | 3篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1957年 | 1篇 |
1942年 | 2篇 |
1931年 | 2篇 |
1928年 | 3篇 |
1924年 | 1篇 |
1921年 | 1篇 |
1873年 | 1篇 |
1872年 | 2篇 |
排序方式: 共有354条查询结果,搜索用时 15 毫秒
21.
The complexing properties of the sub-isoforms of several mammalian Zn-containing metallothioneins (ZnMT) from different origins (rat, rabbit and human foetal livers) have been investigated by capillary zone electrophoresis coupled to diode array detection (CZE-DAD). MTs were submitted to three different experiments: gradual additions of Cd to MT at pH 8.0, variation of the pH and addition of Cd followed by a variation of the pH. On the whole there seems to be no displacement of the zinc originally present in the MT, but incorporation of Cd in the molecule in order to reach saturation. Furthermore, the pH variations allow one to conclude a certain reversibility of the system. All these results confirm those previously obtained by differential pulse polarography (DPP). The procedure used in this work shows that the sub-isoforms of an MT may exhibit variable complexing properties. This is particularly well illustrated in the case of rat liver MT-2. Much likely there are different mixed complexes of Cd and Zn in each sub-isoform, forming various metalloforms. This work illustrates a different and original use of CZE-DAD for studying the complexing properties of metal-binding proteins. 相似文献
22.
We study a Josephson junction (JJ) in the regime of incoherent Cooper-pair tunneling, capacitively coupled to a nonequilibrium noise source. The current-voltage (I-V) characteristics of the JJ are sensitive to the excess voltage fluctuations in the source, and can thus be used for wideband noise detection. Under weak driving, the odd part of the I-V can be related to the second cumulant of noise, whereas the even part is due to the third cumulant. After calibration, one can measure the Fano factors for the noise source, and get information about the frequency dependence of the noise. 相似文献
23.
V.?Jani?Email author J.?Kolorenc V.??picka 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,35(1):77-91
We study noninteracting quantum charged particles (electron gas) subject to a strong random potential and perturbed by a weak classical electromagnetic field. We examine consequences of gauge invariance and charge conservation in the space of Bloch waves. We use two specific forms of the Ward identity between the one- and two-particle averaged Green functions to establish exact relations between the density and current response functions. In particular, we find precise conditions under which we can extract the current-current from the density-density correlation functions and vice versa. We use these results to prove a formula relating the density response and the electrical conductivity in strongly disordered systems. We introduce quantum diffusion as a response function that reduces to the diffusion constant in the static limit. We then derive Ficks law, a quantum version of the Einstein relation and prove the existence of the diffusion pole in the quasistatic limit of the zero-temperature electron-hole correlation function. We show that the electrical conductivity controls the long-range spatial fluctuations of the electron-hole correlation function only in the static limit.Received: 10 June 2003, Published online: 22 September 2003PACS:
72.10.Bg General formulation of transport theory - 72.15.Eb Electrical and thermal conduction in crystalline metals and alloys - 72.15.Qm Scattering mechanisms and Kondo effect 相似文献
24.
25.
In the present article, the relationships between oxidation processes, surface strains and the microstructure of duplex stainless steels were investigated. Specimens were oxidized at 500 °C under secondary vacuum for 1 h to form a thin oxide film (thickness in the range of 20–50 nm). Such specimens were considered as the model system for developing novel methods of analysis in understanding the behavior of passive films. The interfacial strain field after oxidation was measured experimentally at the microscale using the point grid method. On the other hand, the chemical composition of the oxide film was determined at the submicroscopic scale by means of local scanning Auger spectroscopy (with a spot diameter of 50 nm). Local variations of the chemical composition of the oxide film were analyzed according to the specimen microstructure and the strain field. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
26.
Rapid solidification processing (cooling rate from the interval 105–106 K s−1) was used to prepare deeply undercooled cryolite-alumina melts. Such prepared samples were analyzed by the XRD method. Besides
cryolite, XRD patterns belonging to ι-Al2O3 were recorded. The influence of annealing on the XRD patterns of deeply undercooled melts was also investigated. 相似文献
27.
Michal Korenko Marián Kucharík Jozef Vincenc Oboňa Dušan Janičkovič Rosa Córdoba José María De Teresa Blanka Kubíková 《Helvetica chimica acta》2008,91(7):1389-1399
The rapid‐solidification processing (by a cooling rate of 105–106 K/s) was used for the preparation of deeply undercooled cryolite/alumina (Na3AlF6/Al2O3) melts. We found a mass of nanotubes on the surface of these undercooled melts. The nanotubes were preferentially located on the defect places of the surface with the following approximate dimensions: base≈100×100 nm, length≈1000 nm. The solidified samples with the nanotubes on the surface were analyzed by scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDX), X‐ray diffraction (XRD), and infrared spectroscopy (IR). 相似文献
28.
The nature of metal-metal bonding in group 13 dimetallenes REER (E = Al, Ga, In, Tl; R = H, Me, (t)Bu, Ph) was investigated by use of quantum chemical methods that include HF, second order M?ller-Plesset perturbation theory (MP2), coupled cluster (CCSD(T)), complete active space with (CASPT2) and without (CAS) second order perturbation theory, and two density functionals, namely, B3LYP and M06-2X. The results show that the metal-metal interaction in group 13 dimetallenes stems almost exclusively from static and dynamic electron correlation effects: both dialuminenes and digallenes have an important singlet diradical component in their wave function, whereas the bonding in the heavier diindenes and, in particular, dithallenes is dominated by closed shell metallophilic interactions. The reported calculations represent a systematic attempt to determine the metal and ligand dependent bonding changes in these systems. 相似文献
29.
Mika Mahosenaho Felice Caprio Laura Micheli Adama M. Sesay Giuseppe Palleschi Vesa Virtanen 《Mikrochimica acta》2010,170(3-4):243-249
A disposable tri-enzymatic biosensor is presented for the determination of α-amylase in human saliva. It is based on the quantity of maltose generated by hydrolysis of maltopentose in the presence of salivary α-amylase. The biosensor is fabricated by co-immobilization of the enzymes α-glucosidase, glucose oxidase, and mutarotase on screen-printed electrodes modified with Prussian Blue. The assay can be performed with a “drop” of sample, this allowing for ease and simplicity. A linear relationship is found for the range from 5 to 250 units per mL, with an LOD of 5 units per mL. The biosensor is stable for at least one month and over this time retains 80% of its original activity. The system was then evaluated for matrix effects of human saliva and compared to a spectrometric method using a commercially available kit. 相似文献
30.
This article describes the synthesis, structural features, and thermal studies of novel Mn(III) heterochelates of the type
[Mn(SB
n
)(L)(H2O)]·xH2O [H2SB
n
= Nicotinic acid [1-(3-methyl-5-oxo-1-phenyl-4,5 dihydro-1H-pyrazol-4yl)-acylidene]-hydrazide where acyl = acetyl (H2SB1); benzoyl (H2SB2); propionyl (H2SB3); buteryl (H2SB4); phenyl acetyl (H2SB5); and HL = 5-Chloro-7-iodo-8-hydroxyquinoline (clioquinol)]. The heterochelates have been characterized on the basis of elemental
analyses, magnetic susceptibility measurements, cyclic voltammetric studies, (FTIR and electronic) spectra, and thermal studies.
The FAB mass spectrum of [Mn(SB1)(L)H2O]·3H2O has been carried out. The cyclic voltammetric studies reveal that quasi-reversible reduction process of Mn(III)/Mn(II) coupled
system suggesting that the ligands readily destabilize higher oxidation states of metal ion. Kinetic parameters such as order
of reaction (n) and the energy of activation (Ea) were calculated using Freeman–Carroll method. The pre-exponential factor
(A), the activation entropy (S*), the activation enthalpy (H*), and the free energy of activation (G*) were calculated using Horowitz–Metzger equations. 相似文献