首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   373917篇
  免费   3237篇
  国内免费   984篇
化学   190605篇
晶体学   6099篇
力学   18540篇
综合类   15篇
数学   42632篇
物理学   120247篇
  2021年   3219篇
  2020年   3409篇
  2019年   4090篇
  2018年   5585篇
  2017年   5540篇
  2016年   7651篇
  2015年   4223篇
  2014年   7183篇
  2013年   16345篇
  2012年   12871篇
  2011年   15340篇
  2010年   11383篇
  2009年   11429篇
  2008年   14224篇
  2007年   14265篇
  2006年   13164篇
  2005年   11766篇
  2004年   11078篇
  2003年   9915篇
  2002年   9802篇
  2001年   10992篇
  2000年   8368篇
  1999年   6374篇
  1998年   5308篇
  1997年   5360篇
  1996年   4952篇
  1995年   4510篇
  1994年   4461篇
  1993年   4267篇
  1992年   4839篇
  1991年   4952篇
  1990年   4789篇
  1989年   4667篇
  1988年   4637篇
  1987年   4621篇
  1986年   4363篇
  1985年   5574篇
  1984年   5923篇
  1983年   4894篇
  1982年   5016篇
  1981年   4965篇
  1980年   4664篇
  1979年   5052篇
  1978年   5131篇
  1977年   5293篇
  1976年   5366篇
  1975年   4983篇
  1974年   4868篇
  1973年   5102篇
  1972年   3587篇
排序方式: 共有10000条查询结果,搜索用时 671 毫秒
201.
Thin films (monolayer and bilayer) of cylinder forming polystyrene‐block‐polydimethylsiloxane (PS‐b‐PDMS) were shear aligned by the swelling and deswelling of a crosslinked PDMS pad that was physically adhered to the film during solvent vapor annealing. The nanostructures formed by self‐assembly were exposed to ultraviolet‐ozone to partially oxidize the PDMS, followed by calcination in air at 500 °C. In this process, the PS segments were fully decomposed, while the PDMS yielded silica nanostructures. The highly aligned PDMS cylinders were thus deposited as silica nanolines on the silicon substrate. Using a bilayer film, the center‐to‐center distance of these features were effectively halved from 38 to 19 nm. Similarly, by sequential shear‐alignment of two distinct layers, a rhombic array of silica nanolines was fabricated. This methodology provides a facile route to fabricating complex topographically patterned nanostructures. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1058–1064  相似文献   
202.
203.
Vlasov  V. V.  Rautian  N. A. 《Doklady Mathematics》2021,103(1):10-13
Doklady Mathematics - Integro-differential equations with unbounded operator coefficients in a Hilbert space are studied. The equations under consideration are abstract hyperbolic equations...  相似文献   
204.
The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films were investigated using a number of techniques. A high saturation magnetic induction up to B s = 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed, which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of the composition. The text was submitted by the authors in English.  相似文献   
205.
Methods for phase stabilization of ammonium nitrate were sought for in order to considerably expand the application area of this oxidizing agent in various-purpose self-combustible formulations, including that in a new generation of gas-generating formulations for automobile air bags. New methods for stabilization of ammonium nitrate were studied and, in particular, a search was made for organic compounds that can stabilize ammonium nitrate even at their low content. The mechanism of phase state stabilization of ammonium nitrate by compounds of this kind was examined.  相似文献   
206.
Using the simplest (sinusoidal) corrugation profile in the approximation of absence of losses in the material as an example, we study the regimes of complete transformation of an incident wave to the diffraction lobe by a corrugated metal surface or a corrugated interface of two dielectric media. A numerical-intuitive pattern of appearance and evolution of such regimes with increasing corrugation amplitude is revealed. It is shown that the regimes of complete transformation of an incident wave to the diffraction lobe are possible in both the case of autocollimation and the case of a considerable deviation from it. The examination is based on a numerical method of solving the integral equation by means of a specially created interactive processing system in Visual Fortran.  相似文献   
207.
The European Physical Journal E - The isothermal gas adsorption of two hexane isomers (n-hexane and cyclohexane) in the mesopores of MCM-41 silica have been investigated by small angle neutron...  相似文献   
208.
209.
210.
In this paper, integration of interference phenomenon into femtosecond laser micromachining was reported as the femtosecond laser pulses were reshaped spatially to perform ablation. The generation of circular interference pattern was demonstrated by overlapping infrared femtosecond laser pulses. The interference pattern was subsequently focused on a copper substrate to ablate microstructures of concentric circular rings. The present technique is expected to open up new applications in the areas of rapid fabrication of micro-Fresnel lenses, hybrid microlenses and lens arrays.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号