全文获取类型
收费全文 | 9919篇 |
免费 | 1587篇 |
国内免费 | 1401篇 |
专业分类
化学 | 7570篇 |
晶体学 | 163篇 |
力学 | 509篇 |
综合类 | 121篇 |
数学 | 1042篇 |
物理学 | 3502篇 |
出版年
2024年 | 27篇 |
2023年 | 256篇 |
2022年 | 440篇 |
2021年 | 412篇 |
2020年 | 505篇 |
2019年 | 486篇 |
2018年 | 377篇 |
2017年 | 401篇 |
2016年 | 514篇 |
2015年 | 522篇 |
2014年 | 661篇 |
2013年 | 816篇 |
2012年 | 939篇 |
2011年 | 952篇 |
2010年 | 677篇 |
2009年 | 614篇 |
2008年 | 680篇 |
2007年 | 588篇 |
2006年 | 523篇 |
2005年 | 389篇 |
2004年 | 322篇 |
2003年 | 211篇 |
2002年 | 268篇 |
2001年 | 229篇 |
2000年 | 178篇 |
1999年 | 150篇 |
1998年 | 122篇 |
1997年 | 92篇 |
1996年 | 97篇 |
1995年 | 93篇 |
1994年 | 69篇 |
1993年 | 39篇 |
1992年 | 45篇 |
1991年 | 50篇 |
1990年 | 28篇 |
1989年 | 21篇 |
1988年 | 19篇 |
1987年 | 11篇 |
1986年 | 10篇 |
1985年 | 17篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1977年 | 3篇 |
1974年 | 5篇 |
1971年 | 2篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Based on the studies of influence of YAG laser heating conditions for Al alloy melt and steel on wettability,the mechanics of the laser overlap braze welding of 6056 Al and XC18 steel sheet has been investigated.Under the temperature range which is above the melting point of the Al alloy and below the melting point of the steel, two dissimilar metals can be joined by means of laser braze welding. There is no crack observed in the joining area, i.e. Al-Fe intermetallic phase (Fe3Al/FeAl/FeAl3/Fe2Al5) layer formed by solution and diffusion between liquid-solid interface. The temperature range can be defined as the process temperatures of laser braze welding of Al-Fe materials. Selecting a higher laser heating temperature can improve the wettability of Al melt to steel surface, but the intermetallic phase layer is also thicker. When the laser heating temperature is so high that the joining surface of steel is melted, there is a crack trend in the joining area. 相似文献
992.
993.
Jianyi Yang Fan Wang Xiaoqing Jiang Hongchang Qu Yaming Wu Minghua Wang Yuelin Wang 《中国光学快报(英文版)》2005,3(6)
By applying the microring resonator to the Mach-Zehnder (MZ) optical modulator and employing the super-linear phase change characteristic of the all-pass filter, the sublinear modulation curve of the conventional MZ modulator is highly linearized. With properly controlled power coupling between the microring and the arm of the MZ modulator, the third-order distortion can be suppressed. If the transmission coefficient is set between 0.25 and 0.42, the linearity range larger than 90% can be easily achieved. The maximum linearity range is even up to 99.5%. 相似文献
994.
A new simple optical system based on optical beam deflection combining the holophote corner cube was developed in order to study the dynamics of laser-induced shock waves in air. In this method, we adopt a He-Ne laser beam as the detection beam. The He-Ne laser beam, reflected by corner cube, intersects the propagating shock wave at two successive positions. The measurement of the shock wave velocity benefits from the double peak signals induced by the same acting laser pulse, which is calculated from the time interval between the corresponding oscilloscope signals and the distance of the two He-Ne laser beams. By virtue of this setup, we are also able to determine the pressure of the generated shock waves. It is shown that this method is simple with a fairly good precision and is much easier than the conventional methods used for this task. 相似文献
995.
996.
The invariant sets and the solutions of the 1 2-dimensional generalized thin film equation are discussed. It is shown that there exists a class of solutions to the equations, which are invariant with respect to the set E0 = {u : ux = vxF(u), uy = vyF(u)}, where v is a smooth function of variables x, y and F is a smooth function of u. This extends the results of Galaktionov (2001) and for the l l-dimensional nonlinear evolution equations. 相似文献
997.
998.
Part of this work was carried out while the authors were visiting the University of Franche-Comté, Besan?on, and Hokkaido
University, Sapporo, respectively 相似文献
999.
本文探讨了抑制Rugate光学薄膜通带内反射次峰的各种方法。以五次函数匹配和正弦调制相结合的方法获得了在宽光谱范围内能很好抑制反射次峰并能保持其截止带反射率的Rugate膜系。 相似文献
1000.