全文获取类型
收费全文 | 572篇 |
免费 | 19篇 |
专业分类
化学 | 329篇 |
晶体学 | 16篇 |
力学 | 12篇 |
数学 | 62篇 |
物理学 | 172篇 |
出版年
2023年 | 7篇 |
2022年 | 10篇 |
2021年 | 16篇 |
2020年 | 13篇 |
2019年 | 12篇 |
2018年 | 10篇 |
2017年 | 9篇 |
2016年 | 24篇 |
2015年 | 11篇 |
2014年 | 22篇 |
2013年 | 36篇 |
2012年 | 35篇 |
2011年 | 40篇 |
2010年 | 24篇 |
2009年 | 24篇 |
2008年 | 22篇 |
2007年 | 30篇 |
2006年 | 18篇 |
2005年 | 23篇 |
2004年 | 35篇 |
2003年 | 18篇 |
2002年 | 24篇 |
2001年 | 6篇 |
2000年 | 10篇 |
1999年 | 14篇 |
1998年 | 5篇 |
1997年 | 7篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 12篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有591条查询结果,搜索用时 881 毫秒
61.
Domenico Perrone 《Results in Mathematics》2014,66(1-2):213-225
In this paper, we show that if an integrable contact pseudo-metric manifold of dimension 2n + 1, n ≥ 2, has constant sectional curvature \({\kappa}\) , then the structure is Sasakian and \({\kappa=\varepsilon=g(\xi,\xi)}\) , where \({\xi}\) is the Reeb vector field. We note that the notion of contact pseudo-metric structure is equivalent to the notion of non-degenerate almost CR manifold, then an equivalent statement of this result holds in terms of CR geometry. Moreover, we study the pseudohermitian torsion \({\tau}\) of a non-degenerate almost CR manifold. 相似文献
62.
A new technique is proposed to improve information confidentiality in optical-fiber communications without bandwidth consumption. A pseudorandom vectorial sequence was generated by a dynamic system algorithm and used to codify a multi-level polarization modulation based on the Stokes vector. Optical-fiber birefringence, usually considered as a disturbance, was exploited to obfuscate the signal transmission. At the receiver end, the same pseudorandom sequence was generated and used to decode the multi-level polarization modulated signal. The proposed scheme, working at the physical layer, provides strong information security without introducing complex processing and thus latency. 相似文献
63.
Within a large class of exact solutions of the Einstein equations describing a black hole embedded in a Friedmann universe it is shown that, under certain assumptions, only those with comoving Hawking–Hayward quasi-local mass are generic, in the sense that they are late-time attractors. 相似文献
64.
We study the subvariety of integrable 1-forms in a finite-dimensional vector space W⊂Ω1(Cn,0). We prove that the irreducible components with dimension comparable with the rank of W are of minimal degree. 相似文献
65.
S. Acquaviva M. Fernández G. Leggieri A. Luches M. Martino A. Perrone 《Applied Physics A: Materials Science & Processing》1999,69(7):S471-S474
We have designed and built an ultra-high vacuum chamber which allows thin film deposition on large area (up to 100 mm diameter) flat substrates and on three-dimensional substrates (e.g. 100 mm long, 50 mm diameter cylinders) by the pulsed laser deposition and reactive pulsed laser deposition techniques. Heating of substrates during and after film deposition is possible using either resistive heaters or a lamp array. Metal (Cu) and metal nitride (TiN) and carbide (TiC) films were deposited on Si wafers (60 and 100 mm diameter), three-dimensional steel substrates (steel cylinders and screws), Teflon plates, and paper sheets. 相似文献
66.
Hany Nasef Valerio Beni Veli C. Őzalp Ciara K. O’Sullivan 《Analytical and bioanalytical chemistry》2010,396(7):2565-2574
Cystic fibrosis is one of the most common genetically inherited diseases in northern Europe, with the DF508 mutation being
the most common, and among the Caucasian population being responsible for almost 70% of cases. In this work, we report on
the use of thermally modulated electrochemical impedance spectroscopy for the discrimination of the DF508 mutation from the
wild-type sequence. DNA probes (15 and 21 bases long) were immobilised on the surface of gold electrodes and the variation
of the charge-transfer resistance was monitored as a function of hybridisation. Two sets of targets were used in this work:
synthetic 15-mer sequences and two single-stranded synthetic analogues of PCR products 82 (mutant) and 85 (wild type) bases
long. Hybridisation with short targets resulted in very sequence specific charge-transfer-resistance variation with a discrimination
factor at room temperature between fully complementary and mismatched sequences of approximately fivefold. However, in the
case of the single-stranded synthetic PCR product analogues, a lower discrimination factor was recorded (1.5-fold). The effect
of temperature was investigated to improve discrimination and the use of a posthybridisation wash at elevated temperature
resulted in a fivefold improvement in the discrimination factor. Using an electrode array with probes immobilised against
each of the mutant and wild-type sequences, we achieved an unequivocal detection of the DF508 mutation. 相似文献
67.
Ab initio calculations on twenty van der Waals dimers of small polar molecules at the experimentally observed intermolecular separation R, using Hartree-Fock molecular moments, show that the minima in the electrostatic interaction expanded up to R−6 converges to angular structures which are close to those observed experimentally for such complexes. 相似文献
68.
Valerio Faraoni 《Annals of Physics》2005,317(2):366-382
We study the phase space of spatially homogeneous and isotropic cosmology in general scalar-tensor theories. A reduction to a two-dimensional phase space is performed when possible—in these situations the phase space is usually a two-dimensional curved surface embedded in a three-dimensional space and composed of two sheets attached to each other, possibly with complicated topology. The results obtained are independent of the choice of the coupling function of the theory and, in certain situations, also of the potential. 相似文献
69.
Biofunctionalization of Polyoxometalates with DNA Primers,Their Use in the Polymerase Chain Reaction (PCR) and Electrochemical Detection of PCR Products
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Ahmed M. Debela Dr. Mayreli Ortiz Dr. Valerio Beni Prof. Serge Thorimbert Dr. Denis Lesage Prof. Richard B. Cole Prof. Ciara K. O'Sullivan Prof. Bernold Hasenknopf 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(49):17721-17727
The bioconjugation of polyoxometalates (POMs), which are inorganic metal oxido clusters, to DNA strands to obtain functional labeled DNA primers and their potential use in electrochemical detection have been investigated. Activated monooxoacylated polyoxotungstates [SiW11O39{Sn(CH2)2CO}]8? and [P2W17O61{Sn(CH2)2CO}]6? have been used to link to a 5′‐NH2 terminated 21‐mer DNA forward primer through amide coupling. The functionalized primer was characterized by using a battery of techniques, including electrophoresis, mass spectrometry, as well as IR and Raman spectroscopy. The functionality of the POM‐labeled primers was demonstrated through hybridization with a surface‐immobilized probe. Finally, the labeled primers were successfully used in the polymerase chain reaction (PCR) and the PCR products were characterized by using electrophoresis. 相似文献
70.
Rio-Echevarria IM Tavano R Causin V Papini E Mancin F Moretto A 《Journal of the American Chemical Society》2011,133(1):8-11
The stabilizing action of C(α)-tetrasubstituted α-amino acids inserted into a sequence of short peptides allowed for the first time the preparation of water-soluble nanoparticles of different materials coated with a helix-structured undecapeptide. This peptide coating strongly favors nanoparticle uptake by human immune system cells. 相似文献