全文获取类型
收费全文 | 41194篇 |
免费 | 6066篇 |
国内免费 | 2778篇 |
专业分类
化学 | 15336篇 |
晶体学 | 555篇 |
力学 | 1095篇 |
综合类 | 332篇 |
数学 | 2117篇 |
物理学 | 13446篇 |
无线电 | 17157篇 |
出版年
2024年 | 121篇 |
2023年 | 456篇 |
2022年 | 945篇 |
2021年 | 1135篇 |
2020年 | 1275篇 |
2019年 | 1028篇 |
2018年 | 1029篇 |
2017年 | 1385篇 |
2016年 | 1742篇 |
2015年 | 1762篇 |
2014年 | 2342篇 |
2013年 | 3463篇 |
2012年 | 2725篇 |
2011年 | 2729篇 |
2010年 | 2141篇 |
2009年 | 2233篇 |
2008年 | 2507篇 |
2007年 | 2532篇 |
2006年 | 2373篇 |
2005年 | 2120篇 |
2004年 | 1901篇 |
2003年 | 1710篇 |
2002年 | 1612篇 |
2001年 | 1171篇 |
2000年 | 1183篇 |
1999年 | 914篇 |
1998年 | 818篇 |
1997年 | 668篇 |
1996年 | 580篇 |
1995年 | 633篇 |
1994年 | 479篇 |
1993年 | 392篇 |
1992年 | 332篇 |
1991年 | 256篇 |
1990年 | 209篇 |
1989年 | 154篇 |
1988年 | 157篇 |
1987年 | 125篇 |
1986年 | 115篇 |
1985年 | 105篇 |
1984年 | 100篇 |
1983年 | 52篇 |
1982年 | 66篇 |
1981年 | 51篇 |
1980年 | 44篇 |
1979年 | 48篇 |
1978年 | 25篇 |
1977年 | 16篇 |
1976年 | 13篇 |
1973年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
Ana Luísa Daniel‐da‐Silva João Carlos Moura Bordado José Miguel Martín‐Martínez 《Journal of Polymer Science.Polymer Physics》2007,45(22):3034-3045
The degree of phase separation in several moisture‐cured poly(urethane urea)s (PUUs) was studied by FTIR spectroscopy, wide angle X‐ray diffraction (WAXD), and temperature‐modulated differential scanning calorimetry (TMDSC). This latter technique was shown to be particularly useful in analysing the degree of phase separation in PUU polymers. Both phase mixing and phase segregation coexisted in the PUUs and the degree of phase separation increased as the urea hard segment (HS) content in the PUU increased. The maximum solubility of urea HSs into the polyol soft segments (SSs) was achieved for 50 wt % urea HS content in diol‐based PUUs, whereas for triol‐based PUUs the highest solubility between HS and SS was reached for lower urea HS amount. Finally, the higher the urea HS content the higher the extent of phase separation in the PUU. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3034–3045, 2007 相似文献
112.
Zhang Xinliang Huang Dexiu Sun Junqiang Liu Deming 《Optical and Quantum Electronics》2004,36(7):627-634
A simple scheme for single to multi-channel wavelength conversion based on cross-gain modulation of amplified spontaneous emission (ASE) spectrum in semiconductor optical amplifier (SOA) is described. Single to 16-channel wavelength conversion at 10 Gb/s is first demonstrated without any additional probe lights, the modulation information carried by input signal could be converted into arbitrary many channels if only the demultiplexer with enough channels is exploited. Output performance and pattern effects are investigated experimentally. 相似文献
113.
通过对TFM调制技术的研究,修正了其中预调制滤波器冲击响应波形g(f)在时间轴上的位置及其频谱G(w)的表达式.然后将TFM基带信号进行近似,即对TFM的相位路径进行进一步的控制,得到一个改进的TFM调制技术.改进后的TFM调制技术和原TFM调制技术相比,频带压缩能力提高了一倍,误码性能不变,但会出现3 dB的寄生调幅,需要提高发射机的发射功率. 相似文献
114.
Rhythmic growth of ring‐banded spherulites in blends of liquid crystalline methoxy‐poly(aryl ether ketone) (M‐PAEK) and poly(aryl ether ether ketone) (PEEK) has been investigated by means of differential scanning calorimetry (DSC), polarized light microscopy (PLM), and scanning electron microscopy (SEM) techniques. The measurements reveal that the formation of the rhythmically grown ring‐banded spherulites in the M‐PAEK/PEEK blends is strongly dependent on the blend composition. In the M‐PAEK‐rich blends, upon cooling, an unusual ring‐banded spherulite is formed, which is ascribed to structural discontinuity caused by a rhythmic radial growth. For the 50:50 M‐PAEK/PEEK blend, ring‐banded spherulites and individual PEEK spherulites coexist in the system. In the blends with PEEK as the predominant component, M‐PAEK is rejected into the boundary of PEEK spherulites. The cooling rate and crystallization temperature have great effect on the phase behavior, especially the ring‐banded spherulite formation in the blends. In addition, the effects of M‐PAEK phase transition rate and phase separation rate on banded spherulite formation is discussed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3011–3024, 2007 相似文献
115.
基于组件对象模型(COM)技术和微软Office 2000套件的自动化技术,采用内嵌可视BASIC语言(VB)应用编程方法开发了一个基于Outlook 2000的客户端文字邮件语音播放系统.详细介绍了微软语音插件Speech SDK v5.1的架构以及在Outlook 2000中内嵌VB的开发过程.该系统在功能上实现了邮件正文及附件的自动语音播放,在软件界面上实现了语音应用模块与Outlook的无缝集成. 相似文献
116.
117.
118.
119.
Diffractive optical elements have a large number of industrial applications, such as beam shaping and optical filtering. Traditionally, these elements modulate the phase of the incoming light or its amplitude, but not both. To overcome this limitation, full complex-amplitude modulation diffractive optical elements were developed. Well-established integrated circuit fabrication steps were employed to fabricate the devices with high precision. Using this approach, the new element‘s optical performances are improved also for near field operations. With this device it is possible to obtain 100% efficient spatial filtering and low noise reconstructed images. 相似文献
120.
本文提出从高分辨电子显微像中,利用光学、全息和部分相干等方法,提取传递函数,制作相位和振幅滤波器,实现解卷,提高高分辨电子显微像的分辨率. 相似文献