全文获取类型
收费全文 | 2003篇 |
免费 | 369篇 |
国内免费 | 265篇 |
专业分类
化学 | 772篇 |
晶体学 | 27篇 |
力学 | 185篇 |
综合类 | 9篇 |
数学 | 18篇 |
物理学 | 619篇 |
无线电 | 1007篇 |
出版年
2024年 | 3篇 |
2023年 | 14篇 |
2022年 | 46篇 |
2021年 | 62篇 |
2020年 | 87篇 |
2019年 | 69篇 |
2018年 | 73篇 |
2017年 | 94篇 |
2016年 | 132篇 |
2015年 | 122篇 |
2014年 | 119篇 |
2013年 | 147篇 |
2012年 | 152篇 |
2011年 | 154篇 |
2010年 | 95篇 |
2009年 | 114篇 |
2008年 | 114篇 |
2007年 | 158篇 |
2006年 | 123篇 |
2005年 | 106篇 |
2004年 | 117篇 |
2003年 | 109篇 |
2002年 | 75篇 |
2001年 | 82篇 |
2000年 | 47篇 |
1999年 | 39篇 |
1998年 | 38篇 |
1997年 | 38篇 |
1996年 | 31篇 |
1995年 | 15篇 |
1994年 | 10篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 7篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1971年 | 1篇 |
1957年 | 2篇 |
排序方式: 共有2637条查询结果,搜索用时 125 毫秒
51.
2013年4月7日至10日,第八届IEEE国际纳米/微米工程及分子系统大会(IEEE-NEMS 2013)在中国苏州市召开[1-2],来自世界各地的360多位专家、学者齐聚一堂,就微纳研究领域的微/纳米制造和计量、微/纳米传感器、执行器和系统、纳米医学、微/纳流体、生物芯片、纳米材料、碳纳米管、石墨烯器件、微纳传热器件、能量采集器等多个方向展开了学术讨论和交流,充分展示了国内外在以上研究领域的最新研究成果、热点和动态,并对其发展趋势进行了分析。NEMS 2013国际会议的成功举办表明,以微/纳米分子系统等为代表的研究领域已成为高科技的重要代表,并极大地影响着世界的发展和人类生活。 相似文献
52.
Three types of textured indium-tin-oxide (ITO) surface, including nano-texturing and hybrid micro/nano-texturing with micro-holes (concave-hybrid-pattem) or micro-pillars (convex-hybrid-pattern), were applied to GaN-based light-emitting diodes (LEDs). The nano-texturing was realized by maskless wet-etching, and the micro-texturing was achieved by standard photolithography and wet-etching. Compared to LED chips with flat ITO surface, those with nano-pattern, concave-hybrid-pattern, and convex-hybrid-pattern exhibit enhancement of 11.3%, 15.8%, and 17.9%, respectively, for the light-output powers at 20 mA. The electrical performance has no degradation. Moreover, the convex-hybrid-pattern show higher light-output efficiency under small injection current, while the concave-hybrid-pattern exhibit better light-output efficiency at large injection current. The light- extraction efficiency is simulated by use of two-dimensional finite difference time domain method, and the numer- ical results are consistent with the experiments. 相似文献
53.
The interaction between two parallel charged plates in ionic solution is a general starting point for studying colloidal complexes. An intuitive expression of the pressure exerted on the plates is usually proposed, which includes an electrostatic plus an osmotic contribution. We present here an explicit and self-consistent derivation of this formula in the only framework of the Poisson–Boltzmann (PB) theory. We also show that, depending on external constraints, the correct thermodynamic potential can differ from the usual PB free energy. For asymmetric, oppositely charged plates, the resulting expression predicts a non-trivial equilibrium position with the plates separated by a finite distance. The depth of this energy minimum is decisive for the stability of the complex. It is therefore crucial to obtain its explicit dependence on the charge densities of the plates and on the ion concentration. Analytic expressions for the position and depth of the energy minimum were derived in 1975 by Ohshima [Colloid Polym. Sci. 253, 150 (1975)] but, surprisingly, these important results seem to have been overlooked. We retrieve these expressions in a simpler formalism, more familiar to the physics community, and give a physical interpretation of the observed behavior. 相似文献
54.
《Physics letters. A》2019,383(19):2272-2276
Magnetic field design is important in cylindrical Hall thrusters and using permanent magnets to generate magnetic field is very promising in the future. In two typical permanent magnet configurations (i.e., ring and cylindrical configurations) of cylindrical Hall thrusters, discharge characteristics are compared in this paper through the experiments and simulations. The study shows that the cylindrical configuration can bring about higher thruster performance in the same working condition. The reason is that the potential drop of the cylindrical configuration is mainly concentrated in the channel, which is beneficial for the electrons to obtain energy to promote the ionization of the propellant. However, the voltage regulation range of the cylindrical configuration is lower because the anode is more easily overheated. 相似文献
55.
《Journal of Polymer Science.Polymer Physics》2018,56(3):225-238
Structural evolution of gel‐spun ultra‐high molecular weight polyethylene fibers with high concentration solution via hot stretching process was investigated by in situ small‐angle X‐ray scattering, in situ wide‐angle X‐ray diffraction measurements, scanning electron microscopy, and differential scanning calorimetry. With the increase of stretching strain, the long period continuously increases at relative lower stretching temperature, while it first increases and then decreases rapidly at relative higher stretching temperature. The kebab thickness almost keeps constant during the whole hot‐stretching process and the kebab diameter continually decreases for all stretching temperatures. Moreover, the length of shish decreases slightly and the shish quantity increases although there is almost no change in the diameter of shish crystals during the hot stretching process. The degree of crystal orientation at different temperatures is as high as above 0.9 during the whole stretching process. These results indicate that the shish‐kebab crystals in ultra‐high molecular weight polyethylene fibers can transform continuously into the micro‐fibril structure composed mostly of shish crystals through the hot stretching process. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 225–238 相似文献
56.
Micro‐/Nanostructured Multicomponent Molecular Materials: Design,Assembly, and Functionality
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)
Prof. Dr. Dongpeng Yan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(13):4880-4896
Molecule‐based micro‐/nanomaterials have attracted considerable attention because their properties can vary greatly from the corresponding macro‐sized bulk systems. Recently, the construction of multicomponent molecular solids based on crystal engineering principles has emerged as a promising alternative way to develop micro‐/nanomaterials. Unlike single‐component materials, the resulting multicomponent systems offer the advantages of tunable composition, and adjustable molecular arrangement, and intermolecular interactions within their solid states. The study of these materials also supplies insight into how the crystal structure, molecular components, and micro‐/nanoscale effects can influence the performance of molecular materials. In this review, we describe recent advances and current directions in the assembly and applications of crystalline multicomponent micro‐/nanostructures. Firstly, the design strategies for multicomponent systems based on molecular recognition and crystal engineering principles are introduced. Attention is then focused on the methods of fabrication of low‐dimensional multicomponent micro‐/nanostructures. Their new applications are also outlined. Finally, we briefly discuss perspectives for the further development of these molecular crystalline micro‐/nanomaterials. 相似文献
57.
Yingjie Zhang Ping Ning Xueqian Wang Langlang Wang Yixing Ma Qiang Ma Yibing Xie 《应用有机金属化学》2019,33(6)
Manganese‐ and cerium oxide‐modified titania catalysts were prepared by the deposition precipitation for the removal of elemental mercury (Hg0) from simulated yellow phosphorus off‐gas at low temperature. In addition, these catalysts were characterized by X‐ray diffraction, Brunauer–Emmett–Teller measurements, X‐ray photoelectron spectroscopy and field‐emission scanning electron microscope to determine the surface morphology of the obtained compounds and explore their formation mechanism. The results revealed that a Mn–Ce loading and reaction temperature of 10% and 150 °C, respectively, as well as a Mn/Ce molar ratio of 2:1, led to an optimal efficiency for the oxidation of elemental mercury. Furthermore, the effects of flue gas components were investigated. The presence of O2 clearly promoted the oxidation of Hg0. A CO atmosphere did not affect the Hg0 oxidation, when compared with N2, whereas the presence of H2S and water vapor inhibited the oxidation process. Furthermore, the X‐ray photoelectron spectroscopy spectra of Hg 4f revealed that the elemental mercury adsorbed by the catalyst is present as HgO. Finally, the Hg0 catalytic oxidation mechanism was discussed on the basis of the experimental results and characterization analysis. 相似文献
58.
This work aims at elucidating the mechanism of solvation of a radical ion pair (RIP) in a micro‐heterogeneous binary solvent mixture using magnetically affected reaction yield (MARY) spectroscopy. For the exciplex‐forming 9,10‐dimethylanthracene/N,N‐dimethylaniline system a comparative, composition‐dependent MARY line‐broadening study is undertaken in a heterogeneous (toluene/dimethylsulfoxide) and a quasi‐homogenous (propyl acetate/butyronitrile) solvent mixture. The half‐saturation field extrapolated to zero‐quencher concentration, B1/2, and the self‐exchange rate constants are analyzed in the light of solvent dynamical properties of the mixtures and a dielectric continuum solvation model. The dependence of B1/2 on the solvent composition is explained by cluster formation giving rise to shortened RIP lifetimes. The results are in qualitative agreement with the continuum solvation model suggesting that it could serve as a theoretical basis for quantitative modeling. 相似文献
59.
60.