首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   8598篇
  免费   1851篇
  国内免费   831篇
化学   1717篇
晶体学   74篇
力学   147篇
综合类   53篇
数学   118篇
物理学   3604篇
无线电   5567篇
  2024年   40篇
  2023年   134篇
  2022年   233篇
  2021年   278篇
  2020年   293篇
  2019年   227篇
  2018年   207篇
  2017年   326篇
  2016年   401篇
  2015年   453篇
  2014年   631篇
  2013年   607篇
  2012年   631篇
  2011年   631篇
  2010年   500篇
  2009年   509篇
  2008年   576篇
  2007年   553篇
  2006年   585篇
  2005年   448篇
  2004年   450篇
  2003年   412篇
  2002年   323篇
  2001年   291篇
  2000年   270篇
  1999年   190篇
  1998年   177篇
  1997年   139篇
  1996年   143篇
  1995年   103篇
  1994年   85篇
  1993年   86篇
  1992年   100篇
  1991年   57篇
  1990年   37篇
  1989年   27篇
  1988年   37篇
  1987年   9篇
  1986年   11篇
  1985年   11篇
  1984年   11篇
  1983年   8篇
  1982年   11篇
  1981年   7篇
  1980年   5篇
  1979年   7篇
  1978年   3篇
  1977年   2篇
  1975年   2篇
  1973年   1篇
排序方式: 共有10000条查询结果,搜索用时 562 毫秒
1.
In the past, thinking of carrying electronic devices inside our bodies was only posed by non-real scenarios. The emergence of insertable devices has changed this. Since this technology is still in its initial development stages, few studies have investigated factors that influence its acceptance. This paper analyzes the predictors of the intention to use non-medical insertable devices in two Latin American contexts. We used partial least squares structural equation modeling to examine whether six constructs predicted intention to use insertable devices. A questionnaire was administered to undergraduate students located in Colombia and Chile (n = 672). We also examined whether these predictors influenced intention differently for both of them. Four common constructs significantly and positively influenced both Chilean and Colombian respondents to use insertable devices (hedonic motivation, habit, performance expectancy, and social influence). Also, the habit has a complementary mediating effect on the relationship between social influence and behavioral intention. By contrast, effort expectations were a positive and significant predictor, but only among Chilean respondents. Findings suggest that when technologies are emerging, well-known predictors of intention (e.g., performance and effort expectations) are less influential than predictors related to self-efficacy (e.g., habit and hedonic motivation). The use of insertable devices has a significant impact on society. Thus, a better understanding of what motivates their use has implications for both academia and industry.  相似文献   
2.
Shuyuan Lv 《中国物理 B》2022,31(12):124206-124206
Based on the phase-change material Ge2Sb2Te5 (GST), achromatic metasurface optical device in the longer-infrared wavelength is designed. With the combination of the linear phase gradient GST nanopillar and the adjustment of the crystalline fraction m value of GST, the polarization insensitive achromic metalenses and beam deflector metasurface within the longer-infrared wavelength 9.5 μm to 13 μm are realized. The design results show that the achromatic metalenses can be focused on the same focal plane within the working waveband. The simulation calculation results show that the full-width at half-maximum (FWHM) of the focusing spot reaches the diffraction limit at each wavelength. In addition, the same method is also used to design a broadband achromatic beam deflector metasurface with the same deflection angle of 19°. The method proposed in this article not only provides new ideas for the design of achromatic metasurfaces, but also provides new possibilities for the integration of optical imaging, optical coding and other related optical systems.  相似文献   
3.
A device able to electrokinetically concentrate cationic samples has many potential medical and industrial applications, but until now has remained undeveloped due to the lack of a commercial anion-permselective material leading to a prohibitively complex fabrication procedure. Herein, a novel multiscale-porous anion exchange membrane (MP-AEM) that enables the convenient and scalable electrokinetic concentration of cationic species is proposed. A mechanically enhanced multiscale-porous structure with a solid framework is realized by adopting polyester resin as an additive to overcome the intrinsic limitations of the AEM material. The scalable MP-AEM-embedded electrokinetic concentrator is devised based on the peculiar properties of the MP-AEM that for allow both ion and fluid transport. With the MP-AEM, the concentrator is fabricated in a highly streamlined manner consisting only of a simple insertion and assembly. The concentration performance of the MP-AEM-embedded electrokinetic concentrator is demonstrated with a positively charged fluorescent dye and a fluorescein-labeled protein, and the results show enrichment factors of 250 and 500, respectively. The MP-AEM makes cationic electrokinetic concentration more accessible and scalable, thereby enabling further progress in a wide range of fields.  相似文献   
4.
陆敏  王治乐  高萍萍  王华林 《红外与激光工程》2020,49(4):0426002-0426002-7
为了给海面溢油污染识别检测提供理论基础,根据菲涅尔反射公式的偏振反射系数,结合偏振双向反射率因子和粗糙海面的概率密度分布函数,建立了完善的pBRDF模型,仿真在不同太阳入射角度、不同探测器观测角度以及不同海面风速风向等条件下海水和油膜的偏振反射分布函数。结果表明:海水和油膜太阳天顶角为53°和56°时P偏振反射率分别为1.0×10^-5和2.5×10^-5,S偏振反射率随着太阳天顶角的增加而增加;海面风速越大偏振反射率峰值越小;海面风向只改变pBRDF的空间位置;海水和油膜线偏振度空间分布有明显差异。搭建实验平台相机以40°拍摄时,得出海水和油膜的线偏振度分别在0.2~0.4, 0.5~0.7之间,同时表明利用偏振探测获取目标场景的偏振度和偏振角图可提高图像质量。  相似文献   
5.
6.
A strongly electron deficient and high triplet energy host for blue emitters was developed by decorating a dibenzofuran modified biphenyl backbone structure with multiple CN units. Two hosts, 6,6′-bis(6-cyanodibenzo[b,d]furan-4-yl)-[1,1′-biphenyl]-3,3′-dicarbonitrile(CNDBF1) and 2,2′-bis(6-cyanodibenzo[b,d]furan-4-yl)-[1,1′-biphenyl]-4,4′-dicarbonitrile(CNDBF2), were derived from the CN decoration strategy for application in blue organic light-emitting diodes requiring high triplet energy host. They showed high triplet energy above 2.79 eV and acted as the electron transport type host based on the strong electron deficiency. The mixture of the CNDBF1 and CNDBF2 hosts with a hole transport type 3,3′-di(9H-carbazol-9-yl)-1,1′-biphenyl host performed as the exciplex host of a blue phosphor and accomplished high external quantum efficiency of 22.7% in the blue phosphorescent organic light-emitting diodes.  相似文献   
7.
Adsp-21060的主机接口在实时图像处理中的应用   总被引:1,自引:0,他引:1  
简要介绍了数字信号处理器Adsp 2 10 6 0和大规模可编程逻辑器件EP1K5 0。详细讨论了Adsp 2 10 6 0的主机接口工作模式以及一个实时图像跟踪处理器的硬件组成原理 ,在这个系统中EP1K5 0充当了主机。调试结果表明 ,所提出的硬件结构设计思想工作效率高 ,完全能够胜任实时图像处理的实际需要。  相似文献   
8.
文章针对使用USB存储设备造成的内部泄密问题,提出了一种USB存储设备访问控制方案,该方案对用户的身份认证基于安全强度很高的椭圆曲线数字签名算法,同时使用过滤器驱动程序实现了USB存储设备的读写控制,因而此方案具有较好的安全性、实用性和通用性。  相似文献   
9.
1 Introduction High power laser diode arrays (LDA) have many advan- tages such as small volume, long working life, high slope efficiency and high optical density, so they have many applications in medical treatment, material pro- cessing, and for the pumping source of solid laser and etc. But unfortunately, the LDA can not be easy to use directly in these fields because of their poor beam quality and extremely asymmetric divergent beams (!x≈ 5°~10°and !y≈20°~35°, for example), so it …  相似文献   
10.
应用二维器件仿真程序 PISCES- ,对槽栅结构和平面结构器件的特性进行了模拟比较 ,讨论了槽栅结构 MOSFET的沟道电场特征及其对热载流子效应的影响。槽栅结构对抑制短沟道效应和抗热载流子效应是十分有利的 ,而此种结构对热载流子的敏感 ,使器件的亚阈值特性、输出特性变化较大  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号