全文获取类型
收费全文 | 9638篇 |
免费 | 2489篇 |
国内免费 | 769篇 |
专业分类
化学 | 751篇 |
晶体学 | 125篇 |
力学 | 1245篇 |
综合类 | 57篇 |
数学 | 385篇 |
物理学 | 6170篇 |
无线电 | 4163篇 |
出版年
2024年 | 40篇 |
2023年 | 89篇 |
2022年 | 156篇 |
2021年 | 167篇 |
2020年 | 236篇 |
2019年 | 206篇 |
2018年 | 215篇 |
2017年 | 251篇 |
2016年 | 309篇 |
2015年 | 340篇 |
2014年 | 647篇 |
2013年 | 570篇 |
2012年 | 609篇 |
2011年 | 810篇 |
2010年 | 632篇 |
2009年 | 666篇 |
2008年 | 732篇 |
2007年 | 761篇 |
2006年 | 699篇 |
2005年 | 597篇 |
2004年 | 542篇 |
2003年 | 495篇 |
2002年 | 440篇 |
2001年 | 437篇 |
2000年 | 374篇 |
1999年 | 299篇 |
1998年 | 273篇 |
1997年 | 253篇 |
1996年 | 218篇 |
1995年 | 166篇 |
1994年 | 142篇 |
1993年 | 119篇 |
1992年 | 97篇 |
1991年 | 75篇 |
1990年 | 67篇 |
1989年 | 42篇 |
1988年 | 29篇 |
1987年 | 18篇 |
1986年 | 13篇 |
1985年 | 14篇 |
1984年 | 13篇 |
1983年 | 9篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 1篇 |
1976年 | 3篇 |
1974年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
141.
142.
振动系统的模态分析实验设计 总被引:8,自引:0,他引:8
利用模态分析原理和简单试验仪器,得到了直观的悬臂梁和圆盘前4阶模态振型,使学生熟悉了模态分析原理和测试方法,有利于学生对振动规律的理解. 相似文献
143.
144.
The propagation properties of decentered twisted Gaussian Schell-model (DTGSM) beams passing through a misaligned first-order optical system are studied. The explicit expressions for the cross-spectral density function and Wigner distribution function of the output beam are derived, which retain their form unchanged. It is shown that the DTGSM beams preserve their closed property. The second-order moments matrix and the Wigner distribution function evolve with the usual laws, whereas the first-order moments matrix varies, as if a ray passes through such system. The propagation of DTGSM beams through an aligned first-order optical system is treated as the limiting case that corresponds to the vanishing misalignment parameters. 相似文献
145.
O. Maksimov P. Fisher M. Skowronski P.A. Salvador M. Snyder J. Xu X. Weng 《Journal of Crystal Growth》2008,310(11):2760-2766
MgO films were grown on (0 0 1) yttria-stabilized zirconia (YSZ) substrates by molecular beam epitaxy (MBE). The crystalline structures of these films were investigated using X-ray diffraction and transmission electron microscopy. Growth temperature was varied from 350 to 550 °C, with crystalline quality being improved at higher temperatures. The MgO films had a domain structure: (1 1 1)[1 1 2¯]MgO(0 0 1)[1 0 0]YSZ with four twin variants related by a 90° in-plane rotation about the [1 1 1]MgO axis. The observed epitaxial orientation was compared to previous reports of films grown by pulsed laser deposition and sputtering and explained as resulting in the lowest interface energy. 相似文献
146.
By means of a new force sensor based on optical beam deflection (OBD), the mechanical effects of laser-matter interaction underwater at different incident laser energy are investigated in detail. The experimental results show that a target underwater is impacted in turn by laser-plasma ablation force and high-speed liquid-jet impulse induced by bubbles collapse in the vicinity of a solid boundary. Furthermore, the amplitudes of the two forces increase monotonously with laser energy. According to the ablation force detected by the experiment and the theoretical relationship between laser intensity and ablation pressure, the value of liquid-jet impact against a solid boundary can be easily obtained. In addition, based on the model of a collapsing bubble, some characteristic parameters, such as the liquid-jet impact velocity, the maximum bubble radius, the bubble energy can also be obtained at different laser energy, which are valuable in the corresponding research fields. 相似文献
147.
Reduction of dislocation density and improvement of optical quality in ZnO layers by MgO-buffer annealing 总被引:1,自引:0,他引:1
Hiroki Goto Hisao Makino Agus Setiawan Takuma Suzuki Chihiro Harada Tsutomu Minegishi Meoung-Whan Cho Takafumi Yao 《Current Applied Physics》2004,4(6):637-639
Optical properties of ZnO thin films with/without MgO-buffer annealing were investigated by low and room temperature photoluminescence measurements. The ZnO films were grown on c-sapphire substrates by plasma-assisted molecular-beam epitaxy employing a thin MgO-buffer layer. Dislocation density of ZnO layer was reduced from 5.3 × 109 to 1.9 × 109 cm−2 by annealing MgO-buffer prior to the growth of ZnO. The intensity of free exciton emission from the sample with MgO-buffer annealing was almost twice of that from the sample without annealing, while the deep level emission from the sample with MgO-buffer annealing was about 1/3 of that without annealing. The MgO-buffer annealing improves optical quality of overgrown ZnO films. 相似文献
148.
Y. Huang D.J.H. Cockayne C. Marsh J.M. Titchmarsh A.K. Petford-Long 《Applied Surface Science》2005,252(5):1954-1958
A method using a focused ion beam (FIB) to prepare a silicon amorphous material is presented. The method involves the redeposition of sputtered material generated during the interaction of the Ga+ ion beam with a silicon substrate material. The shape and dimensions of this amorphous material are self-organized and reproducible. The stability of this amorphous material under electron irradiation was investigated in the transmission electron microscopy (TEM). Electron irradiation can induce recrystallization of the amorphous material, resulting in the lateral and vertical growth, starting at an amorphous-crystalline interface, of polysilicon containing defects. 相似文献
149.
HL-2A tokamak, the first tokamak with divertor in China, has been constructed and put into operation in 2002. The main parameters are R=1.65 m, a=0.4 m, BT=2.8 T, Ip = 0. 48 MA. The divertor of HL-2A is unique, because it is characterized with a large closed divertor chamber. The device has double divertor chamber, but now it is operating with lower single null configuration to study the physics of divertor for the next step design of a divertor. Supersonic molecular beam injection (SMBI) system with LN2 cooling trap was first installed and demonstrated on the HL-2A tokamak in 2004. The first results of SMBI into HL-2A plasma are to demonstrate the function of the HL-2A divertor and to observe the cold pulse propagation during multi-pulse SMBI on HL-2A Tokamak. 相似文献
150.
综述了暗中空光束自旋与轨道角动量的一些性质及其与中性原子之间的相互作用,并简单介绍了暗中空光束及其角动量在原子光学和玻色_爱因斯坦凝聚(BEC)以及各种原子光学器件研制方面的应用. 相似文献