全文获取类型
收费全文 | 13690篇 |
免费 | 3489篇 |
国内免费 | 926篇 |
专业分类
化学 | 3434篇 |
晶体学 | 562篇 |
力学 | 280篇 |
综合类 | 93篇 |
数学 | 237篇 |
物理学 | 13499篇 |
出版年
2024年 | 49篇 |
2023年 | 107篇 |
2022年 | 285篇 |
2021年 | 296篇 |
2020年 | 316篇 |
2019年 | 251篇 |
2018年 | 290篇 |
2017年 | 468篇 |
2016年 | 520篇 |
2015年 | 495篇 |
2014年 | 802篇 |
2013年 | 1267篇 |
2012年 | 966篇 |
2011年 | 929篇 |
2010年 | 689篇 |
2009年 | 843篇 |
2008年 | 1047篇 |
2007年 | 954篇 |
2006年 | 928篇 |
2005年 | 818篇 |
2004年 | 715篇 |
2003年 | 645篇 |
2002年 | 598篇 |
2001年 | 563篇 |
2000年 | 527篇 |
1999年 | 451篇 |
1998年 | 381篇 |
1997年 | 362篇 |
1996年 | 277篇 |
1995年 | 273篇 |
1994年 | 238篇 |
1993年 | 170篇 |
1992年 | 143篇 |
1991年 | 92篇 |
1990年 | 67篇 |
1989年 | 59篇 |
1988年 | 53篇 |
1987年 | 43篇 |
1986年 | 27篇 |
1985年 | 28篇 |
1984年 | 23篇 |
1983年 | 7篇 |
1982年 | 15篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1976年 | 1篇 |
1975年 | 3篇 |
1973年 | 3篇 |
1970年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
971.
Starting from optical nihility media (ONM), we design several intriguing devices with transformation optics method in two dimensions, such as a wave splitter, a concave lens, a field rotator, a concentrator, and an invisibility cloak. Though the extreme anisotropic property of ONM hinders the fabrication of these devices. We demonstrate that those devices could be effectively realized by simplified materials with Fabry–Pérot resonances (FPs) at discrete frequencies. Moreover, we propose a reduced version of simplified materials with FPs to construct a concentrator and a rotator, which is feasible in experimental fabrications. The simulations of total scattering cross-sections confirm their functionalities. 相似文献
972.
973.
In the calibration of the optical trap stiffness, it is found that there appears an attenuating oscillation as an oscillatory disturbance added to the trapped bead movement, when the scanner is driven by a triangular wave input.An equivalent oscillator model is put forward to explain the mechanism of the oscillatory disturbance. Both the measurements and calculations show that the attenuating oscillation comes from the oscillation of the scanner and the triangular wave drive causes this additional oscillation of the scanner. Furthermore, the analysis indicates that the oscillatory disturbance will become stronger, when the stiffness of the trap increases or the natural frequency of the scanner decreases. We adopt another driving way, i.e. a sinusoidal wave input is used instead of the triangular wave input. Our experiment has verified that in this case the oscillatory disturbance is eliminated completely. 相似文献
974.
975.
光学仪器胶粘剂应用现状及进展 总被引:4,自引:0,他引:4
本文是在对国内光学零件加工及光学仪器产品胶粘剂的应用现状与研究动态的调研基础上,结合作者的工作,综合介绍了光学零件加工过程中工艺用粘接材料与工艺材料用树脂结合剂;光学零件、光学分划元件、光学偏振元件、光学塑料元件等的胶合用光学胶;光学仪器产品结构用结构胶及非结构胶;光学仪器产品及部件用密封胶等的应用现状及其进展概况 相似文献
976.
A new mercury iodide complex of dppf, [HgI2(dppf)] (adduct 1 , dppf = 1,1‐bis(diphenylphosphino)ferrocene) was prepared and characterized. Single crystal X‐ray diffraction analysis established that the compound crystallizes in the monoclinic system, space group C2c, with a = 34.992(3), b = 10.236(5), c = 18.765(4) Å, β = 99.410(2)°, Z = 8, V = 6631.2(9) Å3. The coordination about the mercury atom is tetrahedral with two equivalent Hg–I and Hg–P bonds. Dppf functions as a chelating ligand. The nonlinear optical (NLO) properties were studied with an 8 ns‐pulsed laser at 532 nm. Its optical responses to the incident light exhibit weak optical absorptive and strong refractive effects, with n2 = 6.86 × 10–18 m2 · W–1 in a 2.48 × 10–4 mol · dm–3 DMF solution. 相似文献
977.
Eight types of bicomponent systems composed of antiferroelectric compounds with different polarity of achiral chain and different temperature dependence of helical pitch as well as three multicomponent mixtures composed of antiferroelectric compounds with opposite helical twist sense were studied. The phase miscibility was tested by polarising optical microscopy. The results of the helical pitch and helical twist sense measurements obtained by a spectrophotometric method of selectively reflected light and by polarimetric method, respectively, are presented. It was found that it is possible to control helical pitch length and temperature of helix twist inversion in antiferroelectric mixtures by controlling the ratio of compounds with left- and right-handed helix in such mixtures, although all of them have the same chiral terminal chain. 相似文献
978.
979.
微型平像场近红外光谱仪的消杂散光设计 总被引:1,自引:0,他引:1
设计和研制了结构紧凑、杂散光低的微型平像场近红外光谱仪。在分光系统设计中不采用附加杂散光遮挡装置的常规方法,而是在准直物镜前设置一块直径为8.5mm的平面反射镜,通过调节平面反射镜改变入射光束的空间角,使光束全部被准直镜接收,不再产生旁光,从而有效地消除系统内的杂散光,使仪器整体杂散光水平降低了1.13%。另外,该光谱仪选择线阵CCD作为探测器件,不再设置冷却系统也避免了平面光栅带有扫描旋转机构。由于使用CCD作探测器和新的消杂散光设计方法,该光谱仪实现了微型化。 相似文献
980.