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   481830篇
  免费   4260篇
  国内免费   1011篇
化学   242173篇
晶体学   7287篇
力学   23478篇
综合类   12篇
数学   66492篇
物理学   147659篇
  2020年   3272篇
  2019年   3586篇
  2018年   11977篇
  2017年   12634篇
  2016年   10465篇
  2015年   5091篇
  2014年   6787篇
  2013年   16921篇
  2012年   16490篇
  2011年   25836篇
  2010年   16925篇
  2009年   16801篇
  2008年   23291篇
  2007年   26179篇
  2006年   14132篇
  2005年   17923篇
  2004年   14381篇
  2003年   13391篇
  2002年   11516篇
  2001年   12252篇
  2000年   9486篇
  1999年   7167篇
  1998年   5735篇
  1997年   5784篇
  1996年   5683篇
  1995年   5149篇
  1994年   5326篇
  1993年   4814篇
  1992年   5679篇
  1991年   5736篇
  1990年   5559篇
  1989年   5383篇
  1988年   5470篇
  1987年   5313篇
  1986年   5003篇
  1985年   6561篇
  1984年   6815篇
  1983年   5584篇
  1982年   5703篇
  1981年   5525篇
  1980年   5492篇
  1979年   5690篇
  1978年   6074篇
  1977年   5904篇
  1976年   5874篇
  1975年   5459篇
  1974年   5512篇
  1973年   5697篇
  1972年   3935篇
  1971年   3240篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
992.
993.
Based on the discrete-structural theory of thin plates and shells, a calculation model for thin-walled elements consisting of a number of rigid anisotropic layers is put forward. It is assumed that the transverse shear and compression stresses are equal on the interfaces. Elastic slippage is allowed over the interfaces between adjacent layers. The solution to the problem is obtained in a geometrically nonlinear statement with account of the influence of transverse shear and compression strains. The stress-strain state of circular two-layer transversely isotropic plates, both without defects and with a local area of adhesion failure at their center, is investigated numerically and experimentally. It is found that the kinematic and static contact conditions on the interfaces of layered thin-walled structural members greatly affect the magnitude of stresses and strains. With the use of three variants of calculation models, in the cases of perfect and weakened contact conditions between layers, the calculation results for circular plates are compared. It is revealed that the variant suggested in this paper adequately reflects the behavior of layered thin-walled structural elements under large deformations. __________ Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 6, pp. 761–772, November–December, 2005.  相似文献   
994.
A partnership in a cooperative game is a coalition that possesses an internal structure and, simultaneously, behaves as an individual member. Forming partnerships leads to a modification of the original game which differs from the quotient game that arises when one or more coalitions are actually formed. In this paper, the Shapley value is used to discuss the convenience to form either coalitions or partnerships. To this end, the difference between the additive Shapley value of the partnership in the partnership game and the Shapley alliance value of the coalition, and also between the corresponding value of the internal and external players, are analysed. Simple games are especially considered. Research partially supported by Grant BFM 2003-01314 of the Science and Technology Spanish Ministry and the European Regional Development Fund.  相似文献   
995.
996.
997.
We describe a nonadiabatic electron gun operated in the mode of a currentconfined by spatial charge and intended for producing helical electron beams for high-power gyroresonantdevices.Results of numerical simulation of electron trajectories and electron-beam parameters arepresented. It is shown that for a high operating current, the pitch factor and the electronvelocity spread can be significantly better than in the conventional adiabatic systems. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48,No. 6, pp. 517–522, June 2005  相似文献   
998.
999.
The acoustoelectromagnetic interaction is examined in a regime where three mechanisms must be taken into account simultaneously: photoelasticity, quadratic photoelasticity, and elastic nonlinearity. It is shown that beyond the critical conditions, acoustic solitary waves are formed at harmonic and subharmonic frequencies in a crystal. Including damping and nonideal reflection at the boundaries does not lead to the establishment of any sort of stationary state: a soliton spatial-temporal dynamic develops. Fiz. Tverd. Tela (St. Petersburg) 39, 1101–1104 (June 1997)  相似文献   
1000.
The propagation of surface and volume magnetostatic waves in unsaturated films of yttrium iron garnet is studied experimentally for the case when the wavelength greatly exceeds the domain width, while the domain width is comparable to the film thickness. The characteristics of these waves are examined for symmetric linear, asymmetric linear, and symmetric zigzag strip domain structures in the films. These characteristics cannot be explained by a theory based on averaging the magnetization over all the domains. Zh. éksp. Teor. Fiz. 111, 1016–1031 (March 1997)  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