全文获取类型
收费全文 | 377824篇 |
免费 | 3844篇 |
国内免费 | 1131篇 |
专业分类
化学 | 164464篇 |
晶体学 | 5374篇 |
力学 | 15531篇 |
综合类 | 7篇 |
数学 | 38467篇 |
物理学 | 109725篇 |
无线电 | 49231篇 |
出版年
2021年 | 3498篇 |
2020年 | 3775篇 |
2019年 | 4241篇 |
2018年 | 5719篇 |
2017年 | 5870篇 |
2016年 | 8060篇 |
2015年 | 4369篇 |
2014年 | 7657篇 |
2013年 | 17088篇 |
2012年 | 13092篇 |
2011年 | 15665篇 |
2010年 | 11962篇 |
2009年 | 12444篇 |
2008年 | 15114篇 |
2007年 | 15630篇 |
2006年 | 14513篇 |
2005年 | 12757篇 |
2004年 | 11907篇 |
2003年 | 10690篇 |
2002年 | 10593篇 |
2001年 | 12296篇 |
2000年 | 9547篇 |
1999年 | 7635篇 |
1998年 | 6594篇 |
1997年 | 6403篇 |
1996年 | 5922篇 |
1995年 | 5220篇 |
1994年 | 5137篇 |
1993年 | 4979篇 |
1992年 | 5405篇 |
1991年 | 5514篇 |
1990年 | 5232篇 |
1989年 | 4959篇 |
1988年 | 4638篇 |
1987年 | 4424篇 |
1986年 | 4111篇 |
1985年 | 5140篇 |
1984年 | 5181篇 |
1983年 | 4311篇 |
1982年 | 4315篇 |
1981年 | 4019篇 |
1980年 | 3907篇 |
1979年 | 4151篇 |
1978年 | 4122篇 |
1977年 | 4114篇 |
1976年 | 4062篇 |
1975年 | 3878篇 |
1974年 | 3776篇 |
1973年 | 3816篇 |
1972年 | 2730篇 |
排序方式: 共有10000条查询结果,搜索用时 301 毫秒
21.
Mathematical Notes - Subspaces of the space of analytic functions on a convex domain in the complex plane that are invariant with respect to the differentiation operator are studied. The problem of... 相似文献
22.
Mohammad A. Khalilzadeh Soo Young Kim Ho Won Jang Rafael Luque Rajender S. Varma Richard A. Venditti Mohammadreza Shokouhimehr 《Materials Today Chemistry》2022
The requirement of green and sustainable materials to prepare heterogeneous catalysts has intensified for practical reasons over the past few decades. Carbohydrates are possibly the most plentiful and renewable organic materials in nature with inimitable physiochemical properties, plausible low-cost and large-scale production, and sustainability features could be exploited in the generation of nanostructured heterogeneous catalysts. This review article outlines the organic transformations catalyzed by diverse carbohydrate-based nanostructured catalysts in greener and environmentally friendly processes. Selected examples are highlighted for a variety of organic reactions exploiting the proposed catalysts’ reactivity and reusability, and interactions with the intrinsic nature of the applied carbohydrate supports; advantages and speculated challenges of the introduced catalysts are deliberated as well. 相似文献
23.
Telecommunication Systems - Energy saving in User Equipment (UE) is one of the important issues for limited sources of power in the device. It is critical for the UE to maximize its energy... 相似文献
24.
Seredin P. V. Radam Ali Obaid Goloshchapov D. L. Len’shin A. S. Buylov N. S. Barkov K. A. Nesterov D. N. Mizerov A. M. Timoshnev S. N. Nikitina E. V. Arsentyev I. N. Sharafidinov Sh. Kukushkin S. A. Kasatkin I. A. 《Semiconductors》2022,56(4):253-258
Semiconductors - Abstract—In our work, we carry out a structural-spectroscopic study of AlGaN/GaN epitaxial layers grown by molecular-beam epitaxy with nitrogen-plasma activation on a hybrid... 相似文献
25.
Boltar K. O. Burlakov I. D. Iakovleva N. I. Vlasov P. V. Lazarev P. S. 《Journal of Communications Technology and Electronics》2022,67(9):1175-1184
Journal of Communications Technology and Electronics - In recent years, there has been a rapid improvement in photonics products due to the use of multilayer heterostructures grown on the basis of... 相似文献
26.
27.
Russian Physics Journal - The temperature dependences of the linear dielectric permittivity ε′ and the third harmonic coefficient γ3ω for nanocomposites obtained by embedding a... 相似文献
28.
Golam Haider Krishna Sampathkumar Tim Verhagen Lukáš Nádvorník Farjana J. Sonia Václav Valeš Jan Sýkora Peter Kapusta Petr Němec Martin Hof Otakar Frank Yang-Fang Chen Jana Vejpravová Martin Kalbáč 《Advanced functional materials》2021,31(29):2102196
Recent advancements in isolation and stacking of layered van der Waals materials have created an unprecedented paradigm for demonstrating varieties of 2D quantum materials. Rationally designed van der Waals heterostructures composed of monolayer transition-metal dichalcogenides (TMDs) and few-layer hBN show several unique optoelectronic features driven by correlations. However, entangled superradiant excitonic species in such systems have not been observed before. In this report, it is demonstrated that strong suppression of phonon population at low temperature results in a formation of a coherent excitonic-dipoles ensemble in the heterostructure, and the collective oscillation of those dipoles stimulates a robust phase synchronized ultra-narrow band superradiant emission even at extremely low pumping intensity. Such emitters are in high demand for a multitude of applications, including fundamental research on many-body correlations and other state-of-the-art technologies. This timely demonstration paves the way for further exploration of ultralow-threshold quantum-emitting devices with unmatched design freedom and spectral tunability. 相似文献
29.
We show that near periodic rivet chains that connect two Kirchhoff plates and are modeled by point Sobolev transmission conditions, Rayleigh waves arise, propagate along the chains, and decay exponentially in the orthogonal direction. Under additional geometric conditions we discover the standing (periodic) waves that carry no energy.
相似文献30.
Karandashev S. A. Lukhmyrina T. S. Matveev B. A. Remennyi M. A. Usikova A. A. 《Optics and Spectroscopy》2021,129(11):1231-1235
Optics and Spectroscopy - The current–voltage characteristics and photocurrent of “monolithic” diode optical pairs optically coupled by a substrate made of InAs common for them... 相似文献