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   102450篇
  免费   1168篇
  国内免费   451篇
化学   31824篇
晶体学   903篇
力学   7046篇
数学   32965篇
物理学   17808篇
无线电   13523篇
  2023年   185篇
  2022年   228篇
  2021年   404篇
  2020年   331篇
  2019年   380篇
  2018年   12117篇
  2017年   11710篇
  2016年   7489篇
  2015年   1351篇
  2014年   971篇
  2013年   1324篇
  2012年   5216篇
  2011年   12733篇
  2010年   7542篇
  2009年   7519篇
  2008年   8140篇
  2007年   10526篇
  2006年   1065篇
  2005年   2347篇
  2004年   2414篇
  2003年   2703篇
  2002年   1608篇
  2001年   636篇
  2000年   654篇
  1999年   428篇
  1998年   379篇
  1997年   331篇
  1996年   372篇
  1995年   256篇
  1994年   200篇
  1993年   177篇
  1992年   144篇
  1991年   140篇
  1990年   123篇
  1989年   116篇
  1988年   114篇
  1987年   84篇
  1986年   74篇
  1985年   83篇
  1984年   71篇
  1983年   66篇
  1982年   66篇
  1981年   59篇
  1980年   62篇
  1979年   62篇
  1978年   53篇
  1914年   45篇
  1912年   40篇
  1909年   41篇
  1908年   40篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
41.
42.
43.
44.
45.
The thermoelastoplastic fracture mechanics problem of a thick-walled cylinder subjected to internal pressure and a nonuniform temperature field is solved by the method of elastic solutions combined with the finite-element method. The correctness of the solution is provided by using the Barenblatt crack model, in which the stress and strain fields are regular. The elastoplastic problem of a cracked cylinder subjected to internal pressure and a nonuniform temperature field are solved. The calculation results are compared with available data. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 3, pp. 173–183, May–June, 2008.  相似文献   
46.
47.
48.
The main interest of this study is a new method to solve the axisymmetric frictionless contact problem of functionally graded materials (FGMs). Based on the fact that an arbitrary curve can be approached by a series of continuous but piecewise linear curves, the FGM is divided into a series of sub-layers with shear modulus varying linearly in each sub-layer and continuous at the sub-interfaces. With this model, the axisymmetric frictionless contact problem of a functionally graded coated half-space is investigated. By using the transfer matrix method and Hankel integral transform technique, the problem is reduced to a Cauchy singular integral equation. The contact pressure, contact region and indentation are calculated for various indenters by solving the equations numerically. An erratum to this article can be found at  相似文献   
49.
Using the multipoles method, we formulate the problems of radiation (both heave and sway) of water waves by a submerged sphere in deep as well as in uniform finite depth water with an ice-cover, with the ice-cover being modelled as an elastic plate of very small thickness. In each case this leads to an infinite system of linear equations which are solved numerically by standard techniques. The added-mass and damping coefficients for a heaving and swaying sphere are obtained and depicted graphically against the wave number for various values of the radius of the submerged sphere and flexural rigidity of the ice-cover to show the effect of the presence of ice-cover on these quantities. When the flexural rigidity is taken to be zero, the numerical results for the added-mass and damping coefficient for water with a free surface are recovered.  相似文献   
50.
The paper presents a general method to find asymptotics for a (multi-)wedge system containing a thin wedge. It employs separation of the symmetric and anti-symmetric parts of the boundary displacements and tractions of the wedge. The method is applicable when the angle of the thin wedge turns to zero. A physical interpretation of the derived equations is obtained by using power expansions of non-polynomial functions, which appear after the Mellin transform. We establish that the first term in the expansion of the symmetric part corresponds to shear, while the first term of the anti-symmetric part describes deflection of the wedge axis. Numerical experiments, performed by using a code developed on the basis of the theory, show that using only the first terms of the expansions insignificantly influence accuracy: the approximate results coincide with the exact values of roots to the third significant digit even for the wedge angle of 30°.  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