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   126913篇
  免费   24262篇
  国内免费   11382篇
化学   100814篇
晶体学   1254篇
力学   6533篇
综合类   601篇
数学   12424篇
物理学   40931篇
  2024年   356篇
  2023年   2130篇
  2022年   3450篇
  2021年   3858篇
  2020年   5055篇
  2019年   5835篇
  2018年   4197篇
  2017年   3610篇
  2016年   7739篇
  2015年   7684篇
  2014年   8593篇
  2013年   10706篇
  2012年   11176篇
  2011年   10687篇
  2010年   8411篇
  2009年   8191篇
  2008年   8185篇
  2007年   6863篇
  2006年   6247篇
  2005年   5410篇
  2004年   4317篇
  2003年   3605篇
  2002年   4198篇
  2001年   3258篇
  2000年   2980篇
  1999年   2325篇
  1998年   1728篇
  1997年   1670篇
  1996年   1616篇
  1995年   1381篇
  1994年   1218篇
  1993年   1045篇
  1992年   917篇
  1991年   835篇
  1990年   677篇
  1989年   521篇
  1988年   392篇
  1987年   323篇
  1986年   332篇
  1985年   275篇
  1984年   161篇
  1983年   128篇
  1982年   109篇
  1981年   62篇
  1980年   44篇
  1979年   16篇
  1978年   2篇
  1957年   32篇
  1943年   1篇
  1922年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
This paper is concerned with well‐posedness results for a mathematical model for the transversal vibrations of a two‐dimensional hybrid elastic structure consisting of a rectangular Reissner–Mindlin plate with a Timoshenko beam attached to its free edge. The model incorporates linear dynamic feedback controls along the interface between the plate and the beam. Classical semigroup methods are employed to show the unique solvability of the coupled initial‐boundary‐value problem. We also show that the energy associated with the system exhibits the property of strong stability. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   
92.
In this paper, a generalized anti–maximum principle for the second order differential operator with potentials is proved. As an application, we will give a monotone iterative scheme for periodic solutions of nonlinear second order equations. Such a scheme involves the Lp norms of the growth, 1 ≤ p ≤ ∞, while the usual one is just the case p = ∞.  相似文献   
93.
Spectra Analysis of a Novel Ti-Doped LiAlO2 Single Crystal   总被引:5,自引:0,他引:5       下载免费PDF全文
LiAlO2 single crvstals doped with Ti at concentration 0.2at.% are grown by the Czochralskl technique with dimensions φ42×55mm. Ti ions in the crystal are quadrivalence proven by comparing the absorption and fluorescence spectra of pure LiAlO2 and Ti: LiAlO2. After air and Li-rich atmosphere annealing, the absorption peaks in the range of 600-800nm disappear. We conclude that 682 and 756nm absorption peaks are attributed to the VLi and Vo absorptions, respectively: The peaks at 716nm and 798nm may stem from the VLi^+ and absorptions. The colour-centre model can be applied to explain the experimental phenomena. Ti^4+-doping produces more lithium vacancies in the LiAlO2 crystal. The intensities of [LiO4] and the associated bonds remain unchanged, which improves the anti-hydrolyzation and thermal stability of LiAlO2 crystals.  相似文献   
94.
95.
Let f be a smooth map between unit spheres of possibly different dimensions. We prove the global existence and convergence of the mean curvature flow of the graph of f under various conditions. A corollary is that any area‐decreasing map between unit spheres (of possibly different dimensions) is isotopic to a constant map. © 2004 Wiley Periodicals, Inc.  相似文献   
96.
The main purpose of this paper is to use a mean value theorem of Dirichlet L-functions to study the asymptotic property of a hybrid mean value of a generalized Cochrane sum, and give an interesting mean value formula.2000 Mathematics Subject Classification: Primary—11F20; Secondary—11F99  相似文献   
97.
Jensen and Toft 8 conjectured that every 2‐edge‐connected graph without a K5‐minor has a nowhere zero 4‐flow. Walton and Welsh 19 proved that if a coloopless regular matroid M does not have a minor in {M(K3,3), M*(K5)}, then M admits a nowhere zero 4‐flow. In this note, we prove that if a coloopless regular matroid M does not have a minor in {M(K5), M*(K5)}, then M admits a nowhere zero 4‐flow. Our result implies the Jensen and Toft conjecture. © 2005 Wiley Periodicals, Inc. J Graph Theory  相似文献   
98.
This paper shows that the dimension of internal structure of a component can be measured remotely to a resolution better than 5 μm by use of the combination of high resolution optical microscopy and image processing.A specialised high resolution, long working distance and diffraction limited lens was used to image within the component. A series of digital images were made to map spatially the interior of the component. An edge detector was then used to localise the specific location of features in order that an accurate internal measurement could be made. A visualisation of the internal surface finish was also achieved.  相似文献   
99.
The Hawking effect of a nonuniformly rectilinearly accelerating Kinnersley black hole is studied. Its horizons are rotationally symmetric. Its Hawking temperature depends not only on the time, but also on the polar angle. When a Kinnersley black hole touches its Rindler horizon, the Hawking temperature at the contact point is reduced to zero. But at the opposite pole of the black hole, the Hawking temperature increases rapidly. A jet appears as a tail of the accelerating black hole.  相似文献   
100.
混合位级正交试验设计的极差分析方法   总被引:3,自引:0,他引:3  
本文指出,在混合位级的正交试验设计中,以往的极差分析方法存在着不足。本文给出了极差的修正方法,并用大量实例做了数值验证,说明这个修正确实很有效  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