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   432677篇
  免费   4867篇
  国内免费   1540篇
化学   208243篇
晶体学   6312篇
力学   22506篇
综合类   8篇
数学   74272篇
物理学   127743篇
  2021年   3498篇
  2020年   3847篇
  2019年   4307篇
  2018年   15372篇
  2017年   15381篇
  2016年   13893篇
  2015年   5659篇
  2014年   8185篇
  2013年   17710篇
  2012年   17751篇
  2011年   26681篇
  2010年   17404篇
  2009年   17607篇
  2008年   21358篇
  2007年   23119篇
  2006年   14175篇
  2005年   13412篇
  2004年   12753篇
  2003年   11723篇
  2002年   10798篇
  2001年   11059篇
  2000年   8339篇
  1999年   6463篇
  1998年   5501篇
  1997年   5305篇
  1996年   5061篇
  1995年   4263篇
  1994年   4230篇
  1993年   4091篇
  1992年   4433篇
  1991年   4628篇
  1990年   4367篇
  1989年   4269篇
  1988年   4039篇
  1987年   4177篇
  1986年   3900篇
  1985年   5020篇
  1984年   5027篇
  1983年   4183篇
  1982年   4337篇
  1981年   3999篇
  1980年   3964篇
  1979年   4178篇
  1978年   4144篇
  1977年   4132篇
  1976年   4091篇
  1975年   3864篇
  1974年   3780篇
  1973年   3789篇
  1972年   2698篇
排序方式: 共有10000条查询结果,搜索用时 859 毫秒
61.
The design of new solid-state proton-conducting materials is a great challenge for chemistry and materials science. Herein, a new anionic porphyrinylphosphonate-based MOF ( IPCE-1Ni ), which involves dimethylammonium (DMA) cations for charge compensation, is reported. As a result of its unique structure, IPCE-1Ni exhibits one of the highest value of the proton conductivity among reported proton-conducting MOF materials based on porphyrins (1.55×10−3 S cm−1 at 75 °C and 80 % relative humidity).  相似文献   
62.
In the paper, the authors establish several integral representations for the generating functions of the large and little Schröder numbers and for the large and little Schröder numbers.  相似文献   
63.
Cavitation erosion is caused in solids exposed to strong pressure waves developing in an adjacent fluid field. The knowledge of the transient distribution of stresses in the solid is important to understand the cause of damaging by comparisons with breaking points of the material. The modeling of this problem requires the coupling of the models for the fluid and the solid. For this purpose, we use a strategy based on the solution of coupled Riemann problems that has been originally developed for the coupling of 2 fluids. This concept is exemplified for the coupling of a linear elastic structure with an ideal gas. The coupling procedure relies on the solution of a nonlinear equation. Existence and uniqueness of the solution is proven. The coupling conditions are validated by means of quasi‐1D problems for which an explicit solution can be determined. For a more realistic scenario, a 2D application is considered where in a compressible single fluid, a hot gas bubble at low pressure collapses in a cold gas at high pressure near an adjacent structure.  相似文献   
64.
Russian Journal of General Chemistry - Hybrid liquid crystal systems with different ratios of the components have been prepared on the basis of 5,5′-di(heptadecyl)-2,2′-bipyridine...  相似文献   
65.
66.
67.
68.
69.
70.
Mesoscopic modeling at the pore scale offers great promise in exploring the underlying structure transport performance of flow through porous media. The present work studies the fluid flow subjected to capillarity-induced resonance in porous media characterized by different porous structure and wettability. The effects of porosity and wettability on the displacement behavior of the fluid flow through porous media are discussed. The results are presented in the form of temporal evolution of percentage saturation and displacement of the fluid front through porous media. The present study reveals that the vibration in the form of acoustic excitation could be significant in the mobilization of fluid through the porous media. The dependence of displacement of the fluid on physicochemical parameters like wettability of the surface, frequency along with the porosity is analyzed. It was observed that the mean displacement of the fluid is more in the case of invading fluid with wetting phase where the driving force strength is not so dominant.  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