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   297936篇
  免费   3372篇
  国内免费   847篇
化学   162780篇
晶体学   4375篇
力学   12676篇
综合类   9篇
数学   34874篇
物理学   87441篇
  2020年   2546篇
  2019年   2740篇
  2018年   3475篇
  2017年   3462篇
  2016年   5260篇
  2015年   3350篇
  2014年   5046篇
  2013年   12333篇
  2012年   9805篇
  2011年   12073篇
  2010年   8153篇
  2009年   7833篇
  2008年   11166篇
  2007年   11376篇
  2006年   10712篇
  2005年   9805篇
  2004年   8896篇
  2003年   8011篇
  2002年   7848篇
  2001年   7722篇
  2000年   6036篇
  1999年   4693篇
  1998年   4186篇
  1997年   4172篇
  1996年   4035篇
  1995年   3662篇
  1994年   3789篇
  1993年   3455篇
  1992年   3917篇
  1991年   3902篇
  1990年   3803篇
  1989年   3662篇
  1988年   3783篇
  1987年   3653篇
  1986年   3464篇
  1985年   4704篇
  1984年   4960篇
  1983年   4103篇
  1982年   4302篇
  1981年   4232篇
  1980年   4187篇
  1979年   4148篇
  1978年   4432篇
  1977年   4329篇
  1976年   4370篇
  1975年   4052篇
  1974年   4087篇
  1973年   4243篇
  1972年   2938篇
  1971年   2452篇
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
71.
72.
73.
Bruzy  N.  Coret  M.  Huneau  B.  Kermouche  G.  Mondon  M.  Bertrand  E.  Stainier  L. 《Experimental Mechanics》2019,59(8):1145-1157

The allotropic phase change from ferrite to austenite represents a moment of massive interplay between the microstructural and mechanical states of iron. The difference of compacity between the two phases induces a microplastic accommodation in the material at grain scale. However, mechanical heterogeneities resulting from the transformation process remain challenging to characterise due to the high temperature conditions it is associated with. We developed experimental equipment for in situ observation of α ? γ and γ ? α transformations. Images of the surface of an iron sample taken by an optical camera were used as input for a Digital Image Correlation (DIC) routine. Special care was taken to maximize image resolution to capture sub-grain phenomena. Observations show that, at the mesoscopic scale, shear strain fields exhibit strong localisations that are evidence of transformations that are occurring.

  相似文献   
74.
Radiophysics and Quantum Electronics - Wind-related weather hazards remain difficult to recognize targets for weather radars. Methods that use estimates of the width of the reflected-signal...  相似文献   
75.
Russian Journal of General Chemistry - Highly dispersed CaO has been synthesized by heating an aqueous solution of calcium nitrate and D-glucose up to 800°C. Calcium oxide is formed with an...  相似文献   
76.
Given an n ‐vertex pseudorandom graph G and an n ‐vertex graph H with maximum degree at most two, we wish to find a copy of H in G , that is, an embedding φ : V ( H ) V ( G ) so that φ ( u ) φ ( v ) E ( G ) for all u v E ( H ) . Particular instances of this problem include finding a triangle‐factor and finding a Hamilton cycle in G . Here, we provide a deterministic polynomial time algorithm that finds a given H in any suitably pseudorandom graph G . The pseudorandom graphs we consider are ( p , λ ) ‐bijumbled graphs of minimum degree which is a constant proportion of the average degree, that is, Ω ( p n ) . A ( p , λ ) ‐bijumbled graph is characterised through the discrepancy property: | e ( A , B ) ? p | A | | B | | < λ | A | | B | for any two sets of vertices A and B . Our condition λ = O ( p 2 n / log n ) on bijumbledness is within a log factor from being tight and provides a positive answer to a recent question of Nenadov. We combine novel variants of the absorption‐reservoir method, a powerful tool from extremal graph theory and random graphs. Our approach builds on our previous work, incorporating the work of Nenadov, together with additional ideas and simplifications.  相似文献   
77.
Journal of Analytical Chemistry - HPTLC is a widely used tool in standardization of herbs because of its ability to estimate the presence of active components in samples. HPTLC-bioautography is a...  相似文献   
78.
Journal of Applied Spectroscopy - Aqueous solutions of human hemoglobin have been studied by the multi-angle static light scattering method. The tendency of sickle-shaped erythrocytes to aggregate...  相似文献   
79.
Xu  H. J.  Zhang  Q. G.  Debenest  G. 《Transport in Porous Media》2021,140(3):625-627
Transport in Porous Media - The theme of coupling problems for adsorption, absorption and thermochemical transport in porous media is very important for engineering applications. Based on the...  相似文献   
80.
Aliev  A. B.  Shafieva  G. H. 《Differential Equations》2022,58(8):1028-1042
Differential Equations - We study a mixed problem for systems of one-dimensional semilinear hyperbolic equations with variable nonlinearity growth rate and nonlinear boundary conditions. Theorems...  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