全文获取类型
收费全文 | 607篇 |
免费 | 21篇 |
专业分类
化学 | 377篇 |
晶体学 | 1篇 |
力学 | 28篇 |
数学 | 96篇 |
物理学 | 126篇 |
出版年
2023年 | 13篇 |
2022年 | 3篇 |
2021年 | 19篇 |
2020年 | 21篇 |
2019年 | 25篇 |
2018年 | 15篇 |
2017年 | 16篇 |
2016年 | 26篇 |
2015年 | 26篇 |
2014年 | 11篇 |
2013年 | 26篇 |
2012年 | 38篇 |
2011年 | 42篇 |
2010年 | 20篇 |
2009年 | 22篇 |
2008年 | 30篇 |
2007年 | 41篇 |
2006年 | 29篇 |
2005年 | 23篇 |
2004年 | 21篇 |
2003年 | 15篇 |
2002年 | 12篇 |
2001年 | 8篇 |
2000年 | 7篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 11篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1990年 | 5篇 |
1987年 | 2篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1981年 | 6篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1966年 | 2篇 |
1956年 | 2篇 |
1954年 | 4篇 |
1909年 | 2篇 |
1887年 | 1篇 |
1884年 | 1篇 |
排序方式: 共有628条查询结果,搜索用时 985 毫秒
41.
Zhihui Yi Luca Giacomo Bettini Gaia Tomasello Prajwal Kumar Paolo Piseri Irina Valitova Paolo Milani Francesca Soavi Fabio Cicoira 《Journal of Polymer Science.Polymer Physics》2017,55(1):96-103
Planar organic electrochemical transistors (OECTs) using PEDOT:PSS as the channel material and nanostructured carbon (nsC) as the gate electrode material and poly(sodium 4‐styrenesulfonate (PSSNa) gel as the electrolyte were fabricated on flexible polyethylene terephthalate (Mylar®) substrates. The nsC was deposited at room‐temperature by supersonic cluster beam deposition (SCBD). Interestingly, the OECT acts as a hybrid supercapacitor (to give a device that we indicate as transcap). The energy storage ability of transcaps has been studied with two cell configurations: one featuring PEDOT:PSS as the positive electrode and nsC as the negative electrode and another configuration with reversed electrode polarity. Potentiostatic charge/discharge studies show that both supercapacitors show good performance in terms of voltage retention, in particular, when PEDOT:PSS is used as the positive electrode. Galvanostatic charge–discharge characteristics show typical symmetric triangular shape, indicating a nearly ideal capacitive behavior with a high columbic efficiency (close to 100%). © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 96–103 相似文献
42.
A. Casavola G. Colonna A. De Giacomo M. Capitelli 《Applied Physics A: Materials Science & Processing》2004,79(4-6):1315-1317
In this paper a theoretical model to study the time and space evolution of the plasma generated during the interaction between a KrF laser and a Ti surface has been developed. An optimisation of the initial parameters in the continuous evaporation approximation, such as temperature (T0), rate production of matter (zd), velocity (v0) and ionization degree (), has been carried out to reproduce the experimental profiles obtained by time and space resolved laser induced plasma spectroscopy. The best initial conditions have been found by Downhill simplex method and their effects on the plasma evolution have been discussed. PACS 47.70.Fw; 52.25.Dg; 52.38.Mf; 82.20.Wt 相似文献
43.
A major research field in mechanistic systems biology is represented by the development of methods for investigating the structural and dynamic features of systems with multiple interacting components, in order to understand their function. A combination of NMR techniques can be used in such respect, among which the employment of paramagnetic metal ions, 13C direct detection, and solid-state NMR, possibly supported by other techniques like small angle X-ray scattering. Among the results, the information on the conformational heterogeneity experienced by multicomponent systems in solution can be mentioned. The structural and functional characterization of large biological systems, not affordable with standard solution NMR techniques, can be tackled through a synergistic use of solution and MAS solid-state NMR. 13C direct detection NMR spectroscopy is on the other hand advantageous for improving the quality and quantity of observed nuclear signals, for their intrinsically smaller linewidths and larger signal breadth. Details on these approaches are reviewed here. 相似文献
44.
45.
46.
47.
Rocco Angelone Dr. Francesco Ciardelli Prof. Arturo Colligiani Prof. Francesco Greco Dr. Paolo Masi Prof. Annalisa Romano Dr. Giacomo Ruggeri Prof. 《Chemphyschem》2010,11(2):460-465
A derivative of 2‐methylindole, 3‐[2‐(4‐nitrophenyl)ethenyl]‐1‐allyl‐2‐methylindole, NPEMI‐A, is studied for its photoconductivity and photorefractivity behaviour. Its blends with the organic polymer poly‐(2,3‐dimethyl‐N‐vinylindole), PVDMI, are also investigated. Due to the expected and devised mutual solubility of the two components of the blends, it is possible to carry out measurements with the weight percent of the chromophore NPEMI‐A changing from zero to 100. Films were produced by a squeezing process between two ITO‐covered glass sheets. No opacity phenomena, that are so common for many other organic blends due to the segregation of the dissolved chromophore, are observed. The photorefractive optical gain Γ2 is obtained as a function of the chromophore content. Differential scanning calorimetry measurements (DSC) are also carried out to obtain the whole change of the glass transition temperature Tg as a function of the amount of chromophore contained in the blends. From the experimental trend of Tg a meaningful quantitative estimate of the value of the electrostatic interactions acting in the studied blends, is obtained. The importance of the value of Tg, and of the electrostatic interactions, in determining the extent of the photorefractivity is clearly evident. The results are compared for NPEMI‐A (Γ2=210 cm?1) and for NPEMI‐E (Γ2 ≈ 2000 cm?1) that has a N‐2‐ethylhexyl group instead of a N‐allyl group. The Pockels and Kerr contributions and—for the first time—a “collaborative effect” of the photorefractivity of NPEMI‐A are distinguished and quantitatively evaluated. 相似文献
48.
Livraghi S Corazzari I Paganini MC Ceccone G Giamello E Fubini B Fenoglio I 《Chemical communications (Cambridge, England)》2010,46(44):8478-8480
A safe UV filter may be obtained by inhibiting the photo-generation of free radicals through modification of the surface of TiO(2) nanoparticles with carbon. 相似文献
49.
Leo Liberti Nenad Mladenović Giacomo Nannicini 《Mathematical Programming Computation》2011,3(4):349-390
Finding good (or even just feasible) solutions for Mixed-Integer Nonlinear Programming problems independently of the specific
problem structure is a very hard but practically important task, especially when the objective and/or the constraints are
nonconvex. With this goal in mind, we present a general-purpose heuristic based on Variable Neighborhood Search, Local Branching,
a local Nonlinear Programming algorithm and Branch-and-Bound. We test the proposed approach on MINLPLib, comparing with several
existing heuristic and exact methods. An implementation of the proposed heuristic is freely available and can employ all NLP/MINLP
solvers with an AMPL interface as the main search tools. 相似文献
50.
In this paper we propose practical strategies for generating split cuts, by considering integer linear combinations of the
rows of the optimal simplex tableau, and deriving the corresponding Gomory mixed-integer cuts; potentially, we can generate
a huge number of cuts. A key idea is to select subsets of variables, and cut deeply in the space of these variables. We show
that variables with small reduced cost are good candidates for this purpose, yielding cuts that close a larger integrality
gap. An extensive computational evaluation of these cuts points to the following two conclusions. The first is that our rank-1
cuts improve significantly on existing split cut generators (Gomory cuts from single tableau rows, MIR, Reduce-and-Split,
Lift-and-Project, Flow and Knapsack cover): on MIPLIB instances, these generators close 24% of the integrality gap on average;
adding our cuts yields an additional 5%. The second conclusion is that, when incorporated in a Branch-and-Cut framework, these
new cuts can improve computing time on difficult instances. 相似文献