全文获取类型
收费全文 | 1121篇 |
免费 | 33篇 |
国内免费 | 10篇 |
专业分类
化学 | 645篇 |
晶体学 | 4篇 |
力学 | 35篇 |
数学 | 233篇 |
物理学 | 247篇 |
出版年
2023年 | 10篇 |
2022年 | 12篇 |
2021年 | 8篇 |
2020年 | 17篇 |
2019年 | 16篇 |
2018年 | 16篇 |
2017年 | 16篇 |
2016年 | 31篇 |
2015年 | 24篇 |
2014年 | 28篇 |
2013年 | 56篇 |
2012年 | 62篇 |
2011年 | 76篇 |
2010年 | 44篇 |
2009年 | 40篇 |
2008年 | 57篇 |
2007年 | 52篇 |
2006年 | 52篇 |
2005年 | 53篇 |
2004年 | 48篇 |
2003年 | 30篇 |
2002年 | 36篇 |
2001年 | 16篇 |
2000年 | 17篇 |
1999年 | 19篇 |
1998年 | 18篇 |
1997年 | 18篇 |
1996年 | 15篇 |
1995年 | 14篇 |
1994年 | 21篇 |
1993年 | 9篇 |
1992年 | 17篇 |
1991年 | 20篇 |
1990年 | 16篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1986年 | 9篇 |
1985年 | 7篇 |
1984年 | 22篇 |
1983年 | 8篇 |
1982年 | 12篇 |
1981年 | 11篇 |
1980年 | 9篇 |
1979年 | 6篇 |
1978年 | 11篇 |
1977年 | 7篇 |
1975年 | 7篇 |
1974年 | 5篇 |
1973年 | 9篇 |
1917年 | 4篇 |
排序方式: 共有1164条查询结果,搜索用时 0 毫秒
41.
42.
43.
Scalable bottom‐up assembly of suspended carbon nanotube and graphene devices by dielectrophoresis 下载免费PDF全文
Antonios Oikonomou Nick Clark Sebastian Heeg Andrey Kretinin Sarah Varey Geliang Yu Aravind Vijayaraghavan 《固体物理学:研究快报》2015,9(9):539-543
Bottom‐up assembly by dielectrophoresis (DEP) has emerged in recent years as a viable alternative to conventional top–down fabrication of electronic devices from nanomaterials, particularly carbon nanotubes and graphene. Here, we demonstrate how this technique can be extended to fabricate devices containing carbon nanotubes and graphene suspended between two electrodes over a back‐gate electrode. The suspended device geometry is critical for the development of nano‐electromechanical devices and to extract maximum performance out of electronic and optoelectronic devices. This technique allows for parallel assembly of devices over large scale. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
44.
This paper presents the oil uptake of porous sorbent polymer sheets consisting of ultra‐high molecular weight polyethylene. A comprehensive set of experiments are performed showing the saturation contact time, retention value, mechanical properties, oil pick‐up ratio, pick‐up density, and dynamic dripping profile. Kinetic modeling of the oil sorption is also provided. The experimental results show a good correlation with the pseudo‐second order model. The sheets exhibit high oil uptake speeds, requiring less than 2 min in contact with the oil to reach saturation. The sheets fulfill the criteria of high uptake kinetics, high sorption capacity, and high mechanical strength simultaneously. Those characteristics enable their use in practical spill response. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
45.
Kirsty McKay Tara L. Salter Andrew Bowfield James L. Walsh Ian S. Gilmore James W. Bradley 《Journal of the American Society for Mass Spectrometry》2014,25(9):1528-1537
Plasma-based desorption/ionization sources are an important ionization technique for ambient surface analysis mass spectrometry. In this paper, we compare and contrast three competing plasma based desorption/ionization sources: a radio-frequency (rf) plasma needle, a dielectric barrier plasma jet, and a low-temperature plasma probe. The ambient composition of the three sources and their effectiveness at analyzing a range of pharmaceuticals and polymers were assessed. Results show that the background mass spectrum of each source was dominated by air species, with the rf needle producing a richer ion spectrum consisting mainly of ionized water clusters. It was also seen that each source produced different ion fragments of the analytes under investigation: this is thought to be due to different substrate heating, different ion transport mechanisms, and different electric field orientations. The rf needle was found to fragment the analytes least and as a result it was able to detect larger polymer ions than the other sources. Figure
? 相似文献
46.
Prof. Ashok R. Patel Nick Cludts Mohd Dona Bin Sintang Benny Lewille Ans Lesaffer Prof. Koen Dewettinck 《Chemphyschem》2014,15(16):3435-3439
The preparation and characterization of oleogels structured by using a combination of a surface‐active and a non‐surface‐active polysaccharide through an emulsion‐templated approach is reported. Specifically, the oleogels were prepared by first formulating a concentrated oil‐in‐water emulsion, stabilized with a combination of cellulose derivatives and xanthan gum, followed by the selective evaporation of the continuous water phase to drive the network formation, resulting in an oleogel with a unique microstructure and interesting rheological properties, including a high gel strength, G′>4000 Pa, shear sensitivity, good thixotropic recovery, and good thermostability. 相似文献
47.
48.
Nonlinear Dynamics - This paper introduces new methods to study behaviours among the 52 largest cryptocurrencies between 01-01-2019 and 30-06-2021. First, we explore evolutionary correlation... 相似文献
49.
Harry J. Whitlow Margaretha Andersson Mikael Hult Leif Persson Mohamed El Bouanani Mikael Östling Carina Zaring Nils Lundberg David D. Cohen Nick Dytlewski Peter N. Johnston Ian F. Bubb Scott R. Walker Erik Johanson Sture Hogmark P. Anders Ingemarsson 《Mikrochimica acta》1995,120(1-4):171-181
Recoil Spectrometry covers a group of techniques that are very similar to the well known Rutherford backscattering Spectrometry technique, but with the important difference that one measures the recoiling target atom rather than the projectile ion. This makes it possible to determine both the identity of the recoil and its depth of origin from its energy and velocity, using a suitable detector system. The incident ion is typically high-energy (30–100MeV)35C1,81Br or127I. Low concentrations of light elements such as C, O and N can be profiled in a heavy matrix such as Fe or GaAs. Here we present an overview of mass and energy dispersive recoil Spectrometry and illustrate its successful use in some typical applications. 相似文献
50.
Nick A. Thomburg Ihab M. Abdelrehim Steve Pullins Donald P. Land 《Journal of the American Society for Mass Spectrometry》1994,5(6):583-587
A method for deflecting ions, such as K+, produced outside a Fourier-transform mass spectrometer cell during laser-induced thermal desorption, is described. This technique has been shown to deflect laser-generated K and Ti ions from two Ti foil samples (biomedical implant model surfaces), yielding mass spectra of coadsorbed organic species. Further studies characterizing the laser desorption/deflection parameters have shown that ion deflection improves with higher deflection voltages and greater sample to Fourier-transform mass spectrometry cell separation. Higher laser power densities resulted in greater surface ion production; hence higher deflection voltages were necessary. A 6% increase in laser power necessitated a fourfold increase in deflection voltage for the Ti sample. 相似文献