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   259639篇
  免费   6009篇
  国内免费   3154篇
化学   113454篇
晶体学   3541篇
力学   10223篇
综合类   135篇
数学   24047篇
物理学   74903篇
无线电   42499篇
  2021年   2761篇
  2020年   2984篇
  2019年   3210篇
  2018年   3806篇
  2017年   3684篇
  2016年   5184篇
  2015年   3591篇
  2014年   5321篇
  2013年   11365篇
  2012年   9681篇
  2011年   11113篇
  2010年   8036篇
  2009年   8394篇
  2008年   10658篇
  2007年   10920篇
  2006年   10505篇
  2005年   9492篇
  2004年   8565篇
  2003年   7589篇
  2002年   7223篇
  2001年   8125篇
  2000年   6548篇
  1999年   5324篇
  1998年   4423篇
  1997年   4400篇
  1996年   4057篇
  1995年   3847篇
  1994年   3642篇
  1993年   3481篇
  1992年   3805篇
  1991年   3689篇
  1990年   3559篇
  1989年   3258篇
  1988年   3176篇
  1987年   2889篇
  1986年   2673篇
  1985年   3368篇
  1984年   3578篇
  1983年   2959篇
  1982年   3098篇
  1981年   3062篇
  1980年   2916篇
  1979年   2973篇
  1978年   3051篇
  1977年   3055篇
  1976年   3074篇
  1975年   2884篇
  1974年   2857篇
  1973年   3012篇
  1972年   1938篇
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
11.
Lithium (Li) metal, as an appealing candidate for the next-generation of high-energy-density batteries, is plagued by its safety issue mainly caused by uncontrolled dendrite growth and infinite volume expansion. Developing new materials that can improve the performance of Li-metal anode is one of the urgent tasks. Herein, a new MXene derivative containing pure rutile TiO2 and N-doped carbon prepared by heat-treating MXene under a mixing gas, exhibiting high chemical activity in molten Li, is reported. The lithiation MXene derivative with a hybrid of LiTiO2-Li3N-C and Li offers outstanding electrochemical properties. The symmetrical cell assembling lithiation MXene derivative hybrid anode exhibits an ultra-long cycle lifespan of 2000 h with an overpotential of ≈30 mV at 1 mA cm−2, which overwhelms Li-based anodes reported so far. Additionally, long-term operations of 34, 350, and 500 h at 10 mA cm−2 can be achieved in symmetrical cells at temperatures of −10, 25, and 50 °C, respectively. Both experimental tests and density functional theory calculations confirm that the LiTiO2-Li3N-C skeleton serves as a promising host for Li infusion by alleviating volume variation. Simultaneously, the superlithiophilic interphase of Li3N guides Li deposition along the LiTiO2-Li3N-C skeleton to avoid dendrite growth.  相似文献   
12.
Technical Physics - Taking damping into account in the problems of structural dynamics is an important and nontrivial problem. Its complexity is primarily determined by the required specification...  相似文献   
13.
Physics of Atomic Nuclei - In this paper, the analysis of the relation between the multiplication factor of neutrons of the multiplying system measured in critical experiments and the system...  相似文献   
14.
Siberian Mathematical Journal - Suppose that $ n $ is an integer, $ n\geq 3 $ . We prove that a periodic group saturated with a set of the finite simple groups $ O_{2n+1}(q) $ , where $ q $ is...  相似文献   
15.
We prove a well-posedness result for two pseudo-parabolic problems, which can be seen as two models for the same electrical conduction phenomenon in heterogeneous media, neglecting the magnetic field. One of the problems is the concentration limit of the other one, when the thickness of the dielectric inclusions goes to zero. The concentrated problem involves a transmission condition through interfaces, which is mediated by a suitable Laplace-Beltrami type equation.  相似文献   
16.
Kobayashi  M.  Zhang  Y.  Ishikawa  H.  Sun  J.  Oddershede  J.  Juul Jensen  D.  Miura  H. 《Experimental Mechanics》2021,61(5):817-828
Experimental Mechanics - The internal strain distribution developing during plastic deformation is important for understanding the mechanical properties of polycrystalline materials. Such...  相似文献   
17.
Recently, the successful synthesis of wafer-scale single-crystal graphene, hexagonal boron nitride (hBN), and MoS2 on transition metal surfaces with step edges boosted the research interests in synthesizing wafer-scale 2D single crystals on high-index substrate surfaces. Here, using hBN growth on high-index Cu surfaces as an example, a systematic theoretical study to understand the epitaxial growth of 2D materials on various high-index surfaces is performed. It is revealed that hBN orientation on a high-index surface is highly dependent on the alignment of the step edges of the surface as well as the surface roughness. On an ideal high-index surface, well-aligned hBN islands can be easily achieved, whereas curved step edges on a rough surface can lead to the alignment of hBN along with different directions. This study shows that high-index surfaces with a large step density are robust for templating the epitaxial growth of 2D single crystals due to their large tolerance for surface roughness and provides a general guideline for the epitaxial growth of various 2D single crystals.  相似文献   
18.
Russian Physics Journal - The specific features of the sorption activity of silver nanoparticles (AgNPs) on biodegradable polymers of natural (collagen) and artificial (polyamide 6.6) origin have...  相似文献   
19.
Journal of Communications Technology and Electronics - Abstract—The matrix coefficients of projection models of strip lines obtained using the Chebyshev basis are presented as a sum of...  相似文献   
20.
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