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   233293篇
  免费   834篇
  国内免费   348篇
化学   118885篇
晶体学   4625篇
力学   10165篇
综合类   7篇
数学   22884篇
物理学   77909篇
  2021年   1952篇
  2020年   2209篇
  2019年   2493篇
  2018年   3048篇
  2017年   3173篇
  2016年   4534篇
  2015年   2648篇
  2014年   4129篇
  2013年   9418篇
  2012年   7688篇
  2011年   9329篇
  2010年   6804篇
  2009年   6847篇
  2008年   8574篇
  2007年   8397篇
  2006年   7974篇
  2005年   7230篇
  2004年   6574篇
  2003年   5885篇
  2002年   6062篇
  2001年   6561篇
  2000年   4967篇
  1999年   3906篇
  1998年   3487篇
  1997年   3362篇
  1996年   2968篇
  1995年   2804篇
  1994年   2777篇
  1993年   2591篇
  1992年   2924篇
  1991年   3088篇
  1990年   2884篇
  1989年   2936篇
  1988年   2798篇
  1987年   2623篇
  1986年   2535篇
  1985年   3176篇
  1984年   3354篇
  1983年   2867篇
  1982年   3034篇
  1981年   2823篇
  1980年   2734篇
  1979年   2940篇
  1978年   3196篇
  1977年   3096篇
  1976年   3032篇
  1975年   2903篇
  1974年   2971篇
  1973年   2921篇
  1972年   2037篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
141.
On the basis of nonassociative spinor field theory, the specific properties of a nonassociative spinor field are investigated. A new quantum number is introduced: the associator, which is a measure of the nonassociativeness of the field. To calculate the associator and spin in nonassociative algebra, open and closed products are introduced. It is shown that the spin consists of two components: the first half (calculated by the open-product rule) is similar to ordinary spin, while the second half (calculated by the closed-product rule) is attributed to the associator, i.e., is related to shear in the auxiliary isotopic space. The associator basis is expanded to a complete octonion basis, and the Poincaré group of four-dimensional space is expanded to a Poincaré group of eight-dimensional space. It is shown that, from these generators, in the particle rest system, the nonzero independent eigenvalues are: one, the sign of the particle energy, one of the spin components, one of the associator spatial components, and c7. Tbilisi Medical Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 101–109, October, 1998.  相似文献   
142.
We analyze the possibility of resonant optical radiation inducing evaporation and condensation growth of aerosol particles suspended in a vapor-gas mixture. The molecules of the vapor absorb radiation selectively as to velocity. We examine the Knudsen regime, in which the particle radius is much smaller than the mean free path of the molecules. Zh. éksp. Teor. Fiz. 113, 1036–1047 (March 1998)  相似文献   
143.
144.
145.
146.
A potential of interatomic interaction for simulating complex structural states of solids (grain boundaries and heterogeneous equilibrium states) is put forward. In simulating heterogeneous states of systems, the potential must simultaneously provide for stability conditions for several phases in equilibrium and correct values of a number of macroscopic parameters such as lattice constants, elastic moduli, internal energy, heat capacity, and stability parameters. The existing empirical potentials of interatomic interaction fail to provide agreement of the calculated and experimentally obtained parameters determining the structure of the system and structural transformations due to changes in the external parameters. The potential under discussion is a polynomial representing a solution to the problem of interpolation of functions and their derivatives to the nth order prescribed on a finite system of points (Hermit interpolation problem). The relation for a general solution to the foregoing problem is so complicated that it is virtually inapplicable. A new polynomial is constructed on the basis of the Lagrangian interpolation polynomial. The interpolation of the known interatomic potentials with allowance for the fourth-order derivatives by the polynomial is achieved with high accuracy where three to four interpolation nodes are specified. Local changes can easily be introduced to the polynomial. In doing so, the values of the potential and its derivatives in other regions of space are retained. This allows mechanical stability for stable and metastable phases to be ensured.  相似文献   
147.
148.
Summary The investigation methods of the action of xenobiotics on sterol biosynthesis from 14C-acetate in rat hepatocyte cultures can be developed, with regard to extraction using Extrelut and the separation of the sterol pattern by thin-layer chromatography, in such a way that they are suitable for wider application, e.g., screening. Good visualisation and recognition of changes in the sterol pattern are possible using autoradiography of the thin-layer chromatogram.
Dünnschicht-Chromatographie von radioaktiv markiertem Cholesterin und Vorstufen aus biologischem Material. Eine einfache und empfindliche Methode zur Untersuchung einer Beeinflussung des Sterolbiosynthesewegs

Dedicated to Dr. E. Roesch on occasion of his 65th birthday  相似文献   
149.
150.
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