全文获取类型
收费全文 | 5013篇 |
免费 | 1409篇 |
国内免费 | 582篇 |
专业分类
化学 | 2259篇 |
晶体学 | 66篇 |
力学 | 106篇 |
综合类 | 53篇 |
数学 | 293篇 |
物理学 | 4227篇 |
出版年
2024年 | 7篇 |
2023年 | 49篇 |
2022年 | 120篇 |
2021年 | 106篇 |
2020年 | 122篇 |
2019年 | 101篇 |
2018年 | 148篇 |
2017年 | 219篇 |
2016年 | 215篇 |
2015年 | 230篇 |
2014年 | 415篇 |
2013年 | 351篇 |
2012年 | 449篇 |
2011年 | 440篇 |
2010年 | 357篇 |
2009年 | 333篇 |
2008年 | 386篇 |
2007年 | 384篇 |
2006年 | 318篇 |
2005年 | 325篇 |
2004年 | 256篇 |
2003年 | 238篇 |
2002年 | 177篇 |
2001年 | 173篇 |
2000年 | 134篇 |
1999年 | 104篇 |
1998年 | 107篇 |
1997年 | 112篇 |
1996年 | 90篇 |
1995年 | 94篇 |
1994年 | 75篇 |
1993年 | 45篇 |
1992年 | 49篇 |
1991年 | 43篇 |
1990年 | 36篇 |
1989年 | 27篇 |
1988年 | 29篇 |
1987年 | 31篇 |
1986年 | 24篇 |
1985年 | 20篇 |
1984年 | 14篇 |
1983年 | 10篇 |
1982年 | 14篇 |
1981年 | 12篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有7004条查询结果,搜索用时 15 毫秒
71.
72.
S. Y. Wang S. C. Chen S. D. Lin C. J. Lin C. P. Lee 《Infrared Physics & Technology》2003,44(5-6):527-532
InAs/GaAs quantum dot infrared photodetectors were fabricated with quantum dots grown at three different temperatures. Large detection wavelength shift (5–14.5 μm) was demonstrated by changing 40 degrees of the epitaxy temperature. The smaller quantum dots grown at lower temperature generate 14.5 μm responses. The detectivity of the normal incident 15 μm QDIP at 77 K is 3 × 108 cm Hz1/2/W. A three-color detector was also demonstrated with quantum dots grown at medium temperature. The three-color detection comes from two groups of different sizes of dots within one QD layer. This new type of multicolor detector shows unique temperature tuning behavior that was never reported before. 相似文献
73.
The educational system has gradually shifted from a face-to-face to an e-learning system, which has become prevalent in advanced countries with the advance of information technology, and connection of global networks. Accordingly, a growing demand is emerging for more reliable individual certification with technical precision in order to measure and record learning achievements and credentials of participants. The present system has a limit in terms of registration capacity, therefore, its accuracy has often been questioned. Against this background, an individual certification system is proposed particularly for access control in e-learning. Under our proposed system, a compact optical correlator for facial recognition is employed. This correlator was previously tested for of biometrics authentication accuracy and proved highly reliable, having recorded remarkably low error rates (below 1%). The recorded error rate is sufficiently robust that the system itself can be regarded as a valid and practical viable attestation system. 相似文献
74.
激光相干阵列探测中的二元全息光栅 总被引:2,自引:0,他引:2
从外差阵列探测出发,围绕木振光束整形问题,就计算全息位相光栅在激光相干雷达系统中的应用进行了理论及实施方面的研究,得出较好的结果。 相似文献
75.
应用一种新颖的无损伤测量技术-连续波电光检测法(CWEOP)对GaAs/GaAlAs单异质结发光管列阵电场分布进行了扫描测量。实验结果反映了器件内电流注入的方向和载流子扩展情况;通过比较各单元电场分布,反映器件发光均匀性。文中详细介绍了测量原理、实验装置和实验结果及讨论,最后用计算机对电场分布作了模拟计算并与实验结果进行了对照。 相似文献
76.
Takanari Yasui Takeshi Ohtsuka Tetsu Suzuki Shigeki Okajima Kazuya Nakayama Mitsuru Tomioka Katsuhiro Kamimura Takeo Namekata Hiroaki Minamide Hiromasa Ito 《International Journal of Infrared and Millimeter Waves》2006,27(2):199-210
A new, wide-band, high-speed and high-sensitivity THz detector has been developed. The prototype detector consists of a parabolic
cylindrical mirror, a long wire antenna and a Schottky barrier diode. Direct detection measurements have shown a stable sensitivity
of 150 ± 50 V/W for 1–2 THz without any adjustments. The long wire antenna was fixed at the focus of parabolic cylindrical
mirror then it has been realized less operation steps, easy coupling to the external THz signals and a dramatic enhancement
in the practicality of this system. The optically polished mirror and frosted surface one showed comparable sensitivities,
thus easy polishing and less cost mirror fabrication can be applied for this system. The radiation pattern showed a maximum
radiation angle of approximately 23° with its dominant main lobe, which was attributed to the wire antenna character and confirmed
good agreements with classical antenna theory. 相似文献
77.
78.
79.
本文报道在国内首次采用离子束铣技术研制自集成透镜InGaAsP/InP DH LED的实验结果。采用烘烤正性光致抗蚀剂来形成球状掩膜适合于离子束铣,且重复性很好。为了获得光洁的刻蚀表面,刻蚀条件均已最优化。 相似文献
80.
本文推导了两种非标准色传感器在测色时引入的误差公式,并对其进行分析。最后通过计算8个样品的颜色对分析结果给于验证。 相似文献