全文获取类型
收费全文 | 1312篇 |
免费 | 305篇 |
国内免费 | 180篇 |
专业分类
化学 | 372篇 |
晶体学 | 30篇 |
力学 | 60篇 |
综合类 | 19篇 |
数学 | 28篇 |
物理学 | 798篇 |
无线电 | 490篇 |
出版年
2024年 | 4篇 |
2023年 | 17篇 |
2022年 | 21篇 |
2021年 | 45篇 |
2020年 | 56篇 |
2019年 | 42篇 |
2018年 | 40篇 |
2017年 | 37篇 |
2016年 | 68篇 |
2015年 | 50篇 |
2014年 | 87篇 |
2013年 | 120篇 |
2012年 | 84篇 |
2011年 | 108篇 |
2010年 | 59篇 |
2009年 | 74篇 |
2008年 | 78篇 |
2007年 | 90篇 |
2006年 | 91篇 |
2005年 | 67篇 |
2004年 | 62篇 |
2003年 | 66篇 |
2002年 | 68篇 |
2001年 | 66篇 |
2000年 | 47篇 |
1999年 | 37篇 |
1998年 | 26篇 |
1997年 | 24篇 |
1996年 | 26篇 |
1995年 | 19篇 |
1994年 | 18篇 |
1993年 | 18篇 |
1992年 | 8篇 |
1991年 | 15篇 |
1990年 | 7篇 |
1989年 | 26篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1978年 | 3篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1970年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有1797条查询结果,搜索用时 0 毫秒
201.
本文采用TPF法测Krf^*准分子激光脉冲宽度为对象,研究了荧光介质氦-镉热管的特性,得出了处长He-Cd热管寿命的结构与特性参数。 相似文献
202.
研究了用注 F工艺制作的短沟 MOSFET的热载流子效应。实验结果表明 ,在栅介质中注入适量的 F能够明显地减小由热载流子注入引起的阈电压漂移、跨导退化和输出特性的变化。分析讨论了 F的抗热载流子损伤的机理 相似文献
203.
Formation of Superhydrophobic Alumina Coating Films with High Transparency on Polymer Substrates by the Sol-Gel Method 总被引:6,自引:0,他引:6
Kiyoharu Tadanaga Kaori Kitamuro Atsunori Matsuda Tsutomu Minami 《Journal of Sol-Gel Science and Technology》2003,26(1-3):705-708
Transparent, superhydrophobic coating films have been prepared on polymer substrates at low temperatures through the sol-gel method. Al2O3 gel films were prepared on poly(ethylene terephthalate) substrates from Al(O-sec-C4H9)3 chemically modified with ethyl acetoacetate. A small roughness of about 20–50 nm was found to form on the surface of the Al2O3 gel films dried at room temperature and then immersed in hot water at 60°C. The electron diffraction measurements have shown that this roughened surface consists of pseudoboehmite nanocrystals. The coating of hydrolyzed fluoroalkyltrimethoxysilane on the Al2O3 gel films with the small roughness produced transparent, superhydrophobic films with contact angle for water larger than 150°. 相似文献
204.
介绍了圆片级可靠性技术产生的背景,对其特点和作用作了详细的论述。测试内容上着重介绍了金属化完整性测试、氧化层完整性测试、连接完整性测试和热载流子注入测试,根据测试数据,对1.0μm工艺线单一失效机理的可靠性进行了评价,对不同测试结构的作用进行了说明。 相似文献
205.
新型的化学镀锡在无铅焊接之运用 总被引:1,自引:1,他引:0
阐述线路板的绿色表面涂覆的化学镀锡工艺的有关理论和技术,化学镀锡应用是实现取代热风整平表面涂覆绿色化的最重要的手段之一。我司第三代化学镀锡应用是突破目前化学沉锡的供应商共拥硫脲作为电位改变剂配方此环节,是一种新型独特的科技。 相似文献
206.
207.
C. Fort A. Bambini L. Cacciapuoti F.S. Cataliotti M. Prevedelli G.M. Tino M. Inguscio 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,3(2):113-118
We report on a theoretical and experimental investigation of 39K magneto-optical trapping. The small hyperfine splitting characterizing the upper level of the cooling transition affects
the cooling mechanism. In order to model the atom-laser interaction, the whole level structure of the D2 line has to be taken into account. Two different regimes have been recognized, one optimizing the loading of the trap, the
second minimizing the temperature of the atoms. We investigated these two regimes experimentally and found results in agreement
with the theoretical predictions.
Received: 6 March 1998 / Received in final form: 13 May 1998 / Accepted: 13 May 1998 相似文献
208.
209.
I. Josopait L. Dobrek L. Santos A. Sanpera M. Lewenstein 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):385-391
The atom optics of Bose-Einstein condensates containing a vortex of circulation one is discussed. We first analyze in detail
the reflection of such a condensate falling on an atomic mirror. In a second part, we consider a rotating condensate in the
case of attractive interactions. We show that for sufficiently large nonlinearity the rotational symmetry of the rotating
condensate is broken.
Received 16 September 2002 / Received in final form 17 November 2002 Published online 11 February 2003 相似文献
210.
N. Betz A. Le Moël E. Balanzat J. M. Ramillon J. Lamotte J. P. Gallas G. Jaskierowicz 《Journal of Polymer Science.Polymer Physics》1994,32(8):1493-1502
Poly(vinylidene difluoride) (PVDF) films were irradiated by means of heavy ions (in the electronic stopping-power range) and electrons. Both types of ionizing radiation induce in the polymer film ionizations and excitations, but swift heavy ions induce a huge density of excitations and ionizations along the ion path. Dose-range goes from 0.3 to 40 MGy. Irradiations were performed with Kr ions in the presence of helium, hydrogen, deuterium, and oxygen. Fourier transform infrared (FTIR) transmission measurements show differences in the nature of the created defects. Triple bonds are characteristic of the Kr ion irradiation. Double bonds, isolated and conjugated, exist for both kinds of radiation, but concentrations are higher with the Kr radiation. The presence of oxygen during irradiation produces oxidization defects. Typical bands of hydroxyls and carbonyls can be seen, respectively, in the 3800-3000 cm?1 zone and ca. 1850–1730 cm?1. The formation of conjugated double bonds is enhanced when the Kr irradiation is performed under an O2 atmosphere. © 1994 John Wiley & Sons, Inc. 相似文献