全文获取类型
收费全文 | 2942篇 |
免费 | 122篇 |
国内免费 | 16篇 |
专业分类
化学 | 1790篇 |
晶体学 | 6篇 |
力学 | 129篇 |
数学 | 618篇 |
物理学 | 537篇 |
出版年
2024年 | 2篇 |
2023年 | 30篇 |
2022年 | 65篇 |
2021年 | 126篇 |
2020年 | 73篇 |
2019年 | 91篇 |
2018年 | 68篇 |
2017年 | 52篇 |
2016年 | 115篇 |
2015年 | 110篇 |
2014年 | 126篇 |
2013年 | 191篇 |
2012年 | 227篇 |
2011年 | 249篇 |
2010年 | 146篇 |
2009年 | 109篇 |
2008年 | 202篇 |
2007年 | 172篇 |
2006年 | 160篇 |
2005年 | 164篇 |
2004年 | 114篇 |
2003年 | 105篇 |
2002年 | 94篇 |
2001年 | 38篇 |
2000年 | 31篇 |
1999年 | 25篇 |
1998年 | 15篇 |
1997年 | 28篇 |
1996年 | 22篇 |
1995年 | 17篇 |
1994年 | 16篇 |
1993年 | 13篇 |
1992年 | 6篇 |
1991年 | 2篇 |
1990年 | 8篇 |
1989年 | 7篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1937年 | 2篇 |
排序方式: 共有3080条查询结果,搜索用时 640 毫秒
81.
Viviana De Luca Paolo Digiamberardino Giovanna Di Pasquale Salvatore Graziani Antonino Pollicino Elena Umana Maria Gabriella Xibilia 《Journal of Polymer Science.Polymer Physics》2013,51(9):699-734
Smart systems adapt to the surrounding environments in a number of ways. They are capable to scavenge energy from available sources, sense and elaborate external stimuli and adequately react. Electro Active Polymers are playing a main role in the realization of smart systems for applications if fields such as bio inspired and autonomous robotics, medicine, and aerospace. This paper focus on the possibility to use Ionic Polymer Metal Composites as a class of materials relevant to the realization of post silicon smart systems. The three main aspects of this new technology, i.e., fabrication methods, modeling, and applications are described with emphasis to most recent results. Attention is given to main challenges and shortcomings to be solved for technology, modelling, and control of IPMC based devices that need to be solved before this new technology can be fully exploited in real world applications. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 相似文献
82.
Dr. Robert Ludmerczki Prof. Luca Malfatti Dr. Luigi Stagi Dr. Manuela Meloni Prof. Carlo Maria Carbonaro Prof. Maria Francesca Casula Dr. Dóra Bogdán Dr. Stefania Mura Prof. István M. Mándity Prof. Plinio Innocenzi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(7):2543-2550
Carbonized polymer dots (CPDs), a peculiar type of carbon dots, show extremely high quantum yields, making them very attractive nanostructures for application in optics and biophotonics. The origin of the strong photoluminescence of CPDs resides in a complicated interplay of several radiative mechanisms. To understand the correlation between CPD processing and properties, the early stage formation of carbonized polymer dots has been studied. In the synthesis, citric acid monohydrate and 2-amino-2-(hydroxymethyl)propane-1,3-diol have been thermally degraded at 180 °C. The use of an oil bath instead of a more traditional hydrothermal reactor has allowed the CPD properties to be monitored at different reactions times. Transmission electron microscopy, time-resolved photoluminescence, nuclear magnetic resonance, infrared, and Raman spectroscopy have revealed the formation of polymeric species with amide and ester bonds. Quantum chemistry calculations have been employed to investigate the origin of CPD electronic transitions. At short reaction times, amorphous C-dots with 80 % quantum yield, have been obtained. 相似文献
83.
84.
In this paper we propose an Ant Colony Optimisation (ACO) algorithm for defining the signal settings on urban networks following a local approach. This consists in optimising the signal settings of each intersection of an urban network as a function only of traffic flows at the accesses to the same intersection, taking account of the effects of signal settings on costs and on user route choices. This problem, also known as Local Optimisation of Signal Settings (LOSS), has been widely studied in the literature and can be formulated as an asymmetric assignment problem. The proposed ACO algorithm is based on two kinds of behaviour of artificial ants which allow the LOSS problem to be solved: traditional behaviour based on the response to pheromones for simulating user route choice, and innovative behaviour based on the pressure of an ant stream for solving the signal setting definition problem. Our results on real-scale networks show that the proposed approach allows the solution to be obtained in less time but with the same accuracy as in traditional MSA (Method of Successive Averages) approaches. 相似文献
85.
We prove the existence of maximizers of Sobolev–Strichartz estimates for a general class of propagators, involving relevant examples, as for instance the wave, Dirac and the hyperbolic Schrödinger flows. 相似文献
86.
87.
88.
To safeguard analytical tractability and the concavity of objective functions, the vast majority of models belonging to oligopoly theory relies on the restrictive assumption of linear demand functions. Here we lay out the analytical solution of a differential Cournot game with hyperbolic inverse demand, where firms accumulate capacity over time à la Ramsey. The subgame perfect equilibrium is characterized via the Hamilton–Jacobi–Bellman equations solved in closed form both on infinite and on finite horizon setups. To illustrate the applicability of our model and its implications, we analyze the feasibility of horizontal mergers in both static and dynamic settings, and find appropriate conditions for their profitability under both circumstances. Static profitability of a merger implies dynamic profitability of the same merger. It appears that such a demand structure makes mergers more likely to occur than they would on the basis of the standard linear inverse demand. 相似文献
89.
Alessio Melli Simone Potenti Dr. Mattia Melosso Dr. Sven Herbers Dr. Lorenzo Spada Dr. Andrea Gualandi Kevin G. Lengsfeld Prof. Luca Dore Philipp Buschmann Prof. Pier Giorgio Cozzi Prof. Jens-Uwe Grabow Prof. Vincenzo Barone Prof. Cristina Puzzarini 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(65):15016-15022
Phenylmethanimine is an aromatic imine with a twofold relevance in chemistry: organic synthesis and astrochemistry. To tackle both aspects, a multidisciplinary strategy has been exploited and a new, easily accessible synthetic approach to generate stable imine-intermediates in the gas phase and in solution has been introduced. The combination of this formation pathway, based on the thermal decomposition of hydrobenzamide, with a state-of-the-art computational characterization of phenylmethanimine laid the foundation for its first laboratory observation by means of rotational electric resonance spectroscopy. Both E and Z isomers have been accurately characterized, thus providing a reliable basis to guide future astronomical observations. A further characterization has been carried out by nuclear magnetic resonance spectroscopy, showing the feasibility of this synthetic approach in solution. The temperature dependence as well as possible mechanisms of the thermolysis process have been examined. 相似文献
90.
We prove a density lower bound for some functionals involving bulk and interfacial energies. The bulk energies are convex functions with p-power growth not subjected to any further structure conditions. The interface \(\partial E\) is the boundary of a set \(E\subset \Omega \) such that \(|E|=d\) is prescribed. Then we get \(\mathcal {H}^{n-1}((\partial E{\setminus }\partial E^*)\cup \Omega )=0\).
相似文献