全文获取类型
收费全文 | 11224篇 |
免费 | 355篇 |
国内免费 | 427篇 |
专业分类
化学 | 1731篇 |
晶体学 | 127篇 |
力学 | 94篇 |
综合类 | 16篇 |
数学 | 294篇 |
物理学 | 6816篇 |
无线电 | 2928篇 |
出版年
2024年 | 14篇 |
2023年 | 109篇 |
2022年 | 110篇 |
2021年 | 146篇 |
2020年 | 184篇 |
2019年 | 160篇 |
2018年 | 169篇 |
2017年 | 289篇 |
2016年 | 364篇 |
2015年 | 369篇 |
2014年 | 861篇 |
2013年 | 595篇 |
2012年 | 435篇 |
2011年 | 887篇 |
2010年 | 610篇 |
2009年 | 750篇 |
2008年 | 704篇 |
2007年 | 797篇 |
2006年 | 618篇 |
2005年 | 469篇 |
2004年 | 412篇 |
2003年 | 345篇 |
2002年 | 368篇 |
2001年 | 302篇 |
2000年 | 238篇 |
1999年 | 271篇 |
1998年 | 252篇 |
1997年 | 190篇 |
1996年 | 200篇 |
1995年 | 120篇 |
1994年 | 99篇 |
1993年 | 81篇 |
1992年 | 80篇 |
1991年 | 75篇 |
1990年 | 80篇 |
1989年 | 72篇 |
1988年 | 51篇 |
1987年 | 24篇 |
1986年 | 10篇 |
1985年 | 32篇 |
1984年 | 16篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1975年 | 6篇 |
1974年 | 4篇 |
1973年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
通过对Σ-原子的理论分析,数值求解了相应的Dirac方程,得到 了一组Σ-原子的能级值,与实验数据相当吻合;其结果连同K-原子的情况支持了Batty 光学模型势在奇异原子中应用的正确性,进而表明核子间的强相互作用力为吸引力. 相似文献
32.
33.
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
34.
The propagation property of flattened Gaussian beams (FGBs) is studied based on the Collins formula, and analytical propagation equations for FGBs with and without an aperture are derived. It is shown that the closed-form expressions for the FGB of order N passing through paraxial ABCD optical systems without an aperture can be written as the combinations of Confluent Hyper-geometric Functions, and that the analytical equations for the FGB of order N passing through apertured paraxial ABCD optical systems may involve Error Functions. The proposed algorithms for the considered beams can save computing time, provide intuitive physical insights, and help to design optical systems. Our results are confirmed and illustrated with numerical examples. 相似文献
35.
利用引进的制造技术和设备,制作出了 APT(STLRI)—1.78型系列化光纤连接器。 相似文献
36.
37.
38.
Giuseppe Coppola Andrea Irace Giovanni Breglio Mario Iodice Luigi Zeni Antonello Cutolo Pasqualina M. Sarro 《Optics and Lasers in Engineering》2003,39(3):317-332
In this paper we describe two different kind of optoelectronic devices both based on a three terminals active device and exploit the plasma dispersion effect to achieve the desired working. The first device exploits this effect in order to obtain an optical modulation. The second device is an optoelectronic router based on the mode-mixing principle together with the injection-induced optical phase shift. Both devices are integrated into a Silicon on Silicon optical channel waveguide which can be realized using a standard bipolar process. The possibility of using standard, well-known technology presents several advantages with respect to III–V Optoelectronics. The active three terminal device used is a Bipolar Mode Field Effect Transistor (BMFET). Numerical simulation results are presented on both devices. 相似文献
39.
简要介绍了ASON技术的特点、ASON的引入为新一代光网络带来的好处及衡量网络质量的一些参数和注意事项。 相似文献
40.
The identification of incomplete signal re-setting of optically stimulated luminescence signals in sedimentary quartz is a vitally important step in the continued improvement of optical dating. It is shown that narrow spectrum (blue-green) laboratory partial bleaching of aliquots of natural sedimentary quartz has a significant effect on equivalent dose (measured using a single aliquot procedure) calculated as a function of measurement time (De(t)). The blue-green stimulation spectrum mimics that found underwater and the results suggest that incomplete re-setting of waterlain sediments may be possible using the De(t) method. 相似文献