全文获取类型
收费全文 | 29761篇 |
免费 | 4666篇 |
国内免费 | 3338篇 |
专业分类
化学 | 21134篇 |
晶体学 | 392篇 |
力学 | 1750篇 |
综合类 | 240篇 |
数学 | 3418篇 |
物理学 | 10831篇 |
出版年
2024年 | 58篇 |
2023年 | 559篇 |
2022年 | 720篇 |
2021年 | 971篇 |
2020年 | 1114篇 |
2019年 | 1099篇 |
2018年 | 937篇 |
2017年 | 959篇 |
2016年 | 1390篇 |
2015年 | 1389篇 |
2014年 | 1635篇 |
2013年 | 2144篇 |
2012年 | 2563篇 |
2011年 | 2724篇 |
2010年 | 1772篇 |
2009年 | 1699篇 |
2008年 | 1940篇 |
2007年 | 1729篇 |
2006年 | 1603篇 |
2005年 | 1335篇 |
2004年 | 1085篇 |
2003年 | 889篇 |
2002年 | 852篇 |
2001年 | 637篇 |
2000年 | 575篇 |
1999年 | 662篇 |
1998年 | 545篇 |
1997年 | 514篇 |
1996年 | 571篇 |
1995年 | 475篇 |
1994年 | 470篇 |
1993年 | 327篇 |
1992年 | 305篇 |
1991年 | 287篇 |
1990年 | 231篇 |
1989年 | 168篇 |
1988年 | 146篇 |
1987年 | 117篇 |
1986年 | 122篇 |
1985年 | 99篇 |
1984年 | 72篇 |
1983年 | 63篇 |
1982年 | 46篇 |
1981年 | 38篇 |
1980年 | 32篇 |
1979年 | 20篇 |
1978年 | 12篇 |
1977年 | 10篇 |
1975年 | 9篇 |
1973年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
本文以一道题为例对研究性教学中的习题环节进行了实例研究.大致按照事件发生的顺序叙述以再现现场情景. 相似文献
62.
A novel technique to overcome the long-term drift and hysteresis of a scanning Fabry–Perot filter was developed and applied to wavelength and power monitoring of DWDM system. By using the comb peaks generated by a temperature-stabilized, near threshold-biased Fabry–Perot diode laser as wavelength reference for the scanning Fabry–Perot filter, wavelength and power measurement accuracy of better than ±10 pm and 0.2 dB, respectively, were achieved. 相似文献
63.
64.
65.
66.
A multi-exposure of color fringes method has been developed to improve the capture speed of a conventional color CCD camera. In the method, four groups of projected fringe patterns encoded with different colors and different directions are stored in one CCD frame. Therefore the capture frequency of the conventional CCD can be improved to 200 Hz. It is available to measure the insect wings with low beating frequency, such as dragonfly, moth, or butterfly, whose beating frequency is about 30–40 Hz. We have used the method to measure the beating motion of a moth successfully. 相似文献
67.
Newton-Leibniz integration rule only applies to commuting functions of continuum variables, while operators made of Dirac’s symbols (ket versus bra, e.g., |q〉〈q| of continuous parameter q) in quantum mechanics are usually not commutative. Therefore, integrations over the operators of type |〉〈| cannot be directly performed by Newton-Leibniz rule. We invented an innovative technique of integration within an ordered product (IWOP) of operators that made the integration of non-commutative operators possible. The IWOP technique thus bridges this mathematical gap between classical mechanics and quantum mechanics, and further reveals the beauty and elegance of Dirac’s symbolic method and transformation theory. Various applications of the IWOP technique, including constructing the entangled state representations and their applications, are presented. 相似文献
68.
The orientation-selective growth of LaNiO3 films on Si(100) by pulsed laser deposition using a MgO buffer 总被引:4,自引:0,他引:4
X.Y. Chen K.H. Wong C.L. Mak J.M. Liu X.B. Yin M. Wang Z.G. Liu 《Applied Physics A: Materials Science & Processing》2002,75(4):545-549
Highly (100)-oriented, (110)-oriented and polycrystalline LaNiO3 (LNO) films were successfully prepared on Si(100) using an oriented MgO film as a buffer. It was somewhat surprising to find
that that the orientation relation between the LNO film and the corresponding MgO buffer was: LNO(100)\MgO(110), LNO(110)\MgO(111)
and LNO(polycrystalline)\MgO(100). The crystalline quality of the LNO films was shown to be sensitive to the preparation conditions
of the MgO buffer. The film surface was very smooth, without micrometer-sized droplets being observed. All LNO films were
of metallic conductivity, with a room-temperature resistivities of approximately 250, 280 and 420 μΩ cm for the (110)-oriented,
(100)-oriented and polycrystalline LNO, respectively.
Received: 2 April 2001 / Accepted: 23 October 2001 / Published online: 3 June 2002 相似文献
69.
70.
Soliton interaction under the influence of higher-order effects 总被引:6,自引:0,他引:6
In this paper, we present exact N-soliton solution by employing simple, straightforward Darboux transformation based on the Lax pair for Hirota equation, a higher-order nonlinear Schrödinger (HNLS) equation. As examples, one- and two-soliton solutions in explicit forms are given and their properties are also analyzed. A bound solution without interaction will be theoretically predicted if one can adjust frequency shift for each soliton appropriately. Further, we obtain the approximate eigenvalues by employing two-soliton solution and discuss analytically the interaction between neighboring solitons under the influence of the higher-order effects. It is shown that the combined effects of the higher-order effects can restrain the interaction between neighboring solitons to some extent. The results are proved by directly solving HNLS equation numerically. 相似文献