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   1684篇
  免费   173篇
  国内免费   103篇
化学   38篇
晶体学   1篇
力学   277篇
综合类   13篇
数学   597篇
物理学   309篇
综合类   725篇
  2024年   4篇
  2023年   15篇
  2022年   24篇
  2021年   17篇
  2020年   23篇
  2019年   32篇
  2018年   32篇
  2017年   26篇
  2016年   32篇
  2015年   43篇
  2014年   71篇
  2013年   130篇
  2012年   122篇
  2011年   107篇
  2010年   72篇
  2009年   90篇
  2008年   105篇
  2007年   97篇
  2006年   108篇
  2005年   92篇
  2004年   68篇
  2003年   75篇
  2002年   68篇
  2001年   64篇
  2000年   51篇
  1999年   53篇
  1998年   50篇
  1997年   39篇
  1996年   42篇
  1995年   38篇
  1994年   29篇
  1993年   30篇
  1992年   30篇
  1991年   23篇
  1990年   17篇
  1989年   11篇
  1988年   8篇
  1987年   6篇
  1986年   3篇
  1985年   7篇
  1983年   1篇
  1982年   2篇
  1980年   1篇
  1979年   1篇
  1976年   1篇
排序方式: 共有1960条查询结果,搜索用时 15 毫秒
101.
We construct the Extended Relativity Theory in Born-Clifford-Phase spaces with an upper R and lower length λ scales (infrared/ultraviolet cutoff). The invariance symmetry leads naturally to the real Clifford algebra Cl (2, 6, R) and complexified Clifford ClC (4) algebra related to Twistors. A unified theory of all Noncommutative branes in Clifford-spaces is developed based on the Moyal-Yang star product deformation quantization whose deformation parameter involves the lower/upper scale . Previous work led us to show from first principles why the observed value of the vacuum energy density (cosmological constant) is given by a geometric mean relationship , and can be obtained when the infrared scale R is set to be of the order of the present value of the Hubble radius. We proceed with an extensive review of Smith’s 8D model based on the Clifford algebra Cl (1, 7) that reproduces at low energies the physics of the Standard Model and Gravity, including the derivation of all the coupling constants, particle masses, mixing angles, ....with high precision. Geometric actions are presented like the Clifford-Space extension of Maxwell’s Electrodynamics, and Brandt’s action related to the 8D spacetime tangent-bundle involving coordinates and velocities (Finsler geometries). Finally we outline the reasons why a Clifford-Space Geometric Unification of all forces is a very reasonable avenue to consider and propose an Einstein-Hilbert type action in Clifford-Phase spaces (associated with the 8D Phase space) as a Unified Field theory action candidate that should reproduce the physics of the Standard Model plus Gravity in the low energy limit.  相似文献   
102.
By using hyperbolic virtual unit of Clifford algebra, the concept of n-dimensional space-time unit spheres is introduced. It is used as n-dimensional Minkowski space-time and Lorentz transformation.  相似文献   
103.
Clifford algebraic geometry corresponds to Minkowski space. Using the discrete structure of Minkowski space, we can abstract a class n-dimensional hyperbolic Hilbert phase space. To discussing the causality of physical event in Minkowski space, we can obtain the geometrical interpretation of uncertainty relation.  相似文献   
104.
In this paper we introduce the notion of operator semirings of a -semiring to study -semirings. It is shown that the lattices of all left (right) ideals (two-sided ideals) of a -semiring and its right (respectively left) operator semiring are isomorphic. This has many applications to characterize various -semirings.AMS Subject Classification (2000): 16Y60, 16Y99  相似文献   
105.
This paper improves an old theorem about a rectangular hyperbola : its centre lies on the pedal circle of any point on with respect to any triangle inscribed in . We also prove that an analogous result holds for Cevian circles. These results are used to obtain new characterisations of the Feuerbach, Jarabek, and Kiepert hyperbolas of a triangle.  相似文献   
106.
研究了矩形广义系统的有穷极点配置问题.提出了利用动态补偿器对矩形广义系统进行有穷极点任意配置的一种方法及一个充要条件,并且得出了此方法所能任意配置的有穷极点的数目是r r_c个。通过动态补偿,将矩形广义系统的有穷极点配置问题转化为正常系统的极点配置问题,使整个闭环系统实现正则,无脉冲,任意极点配置。  相似文献   
107.
常压矩形容器壁板强度和刚度设计   总被引:1,自引:0,他引:1  
目前 ,国内化工行业中所用的矩形常压容器都是按 JB/T4735 -1997《钢制焊接常压容器》规范进行设计的。新版中增加了 ( APRV)一类新型容器。文章以矩形薄板的经典李维 ( L evy)解为基础 ,推导了三边简支一边自由 ,承受液体静压矩形板的应力和挠度计算公式 ,并由此进一步分析得到了常压矩形容器壁板的厚度、挠度计算公式和曲线。  相似文献   
108.
We describe the structure of semirings which are unions of a ring and a half-body.  相似文献   
109.
A quadrature Galerkin scheme with the Bogner–Fox–Schmit element for a biharmonic problem on a rectangular polygon is analyzed for existence, uniqueness, and convergence of the discrete solution. It is known that a product Gaussian quadrature with at least three‐points is required to guarantee optimal order convergence in Sobolev norms. In this article, optimal order error estimates are proved for a scheme based on the product two‐point Gaussian quadrature by establishing a relation with an underdetermined orthogonal spline collocation scheme. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2008  相似文献   
110.
A structure theorem is proved for the solutions to the Moisil–Théodoresco system in open subsets of ?3. Furthermore, it is shown that the Cauchy transform maps L2(?2, ?0, 2+) isomorphically onto H2(?+3, ?0, 3+), thus proving an elegant generalization to ?2 of the classical notion of an analytic signal on the real line. Copyright © 2008 John Wiley & Sons, Ltd.  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