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   188208篇
  免费   2831篇
  国内免费   512篇
化学   101201篇
晶体学   2220篇
力学   7642篇
综合类   12篇
数学   21594篇
物理学   58882篇
  2020年   1577篇
  2019年   1541篇
  2018年   1952篇
  2017年   1931篇
  2016年   3450篇
  2015年   2308篇
  2014年   3310篇
  2013年   8057篇
  2012年   6568篇
  2011年   8044篇
  2010年   5481篇
  2009年   5282篇
  2008年   7333篇
  2007年   7313篇
  2006年   6875篇
  2005年   6301篇
  2004年   5544篇
  2003年   4792篇
  2002年   4701篇
  2001年   5064篇
  2000年   3925篇
  1999年   3018篇
  1998年   2620篇
  1997年   2563篇
  1996年   2450篇
  1995年   2337篇
  1994年   2362篇
  1993年   2193篇
  1992年   2519篇
  1991年   2459篇
  1990年   2269篇
  1989年   2240篇
  1988年   2157篇
  1987年   2077篇
  1986年   1972篇
  1985年   2649篇
  1984年   2758篇
  1983年   2261篇
  1982年   2462篇
  1981年   2334篇
  1980年   2300篇
  1979年   2413篇
  1978年   2559篇
  1977年   2443篇
  1976年   2445篇
  1975年   2357篇
  1974年   2405篇
  1973年   2346篇
  1972年   1516篇
  1971年   1370篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
Electrochemical separation of lead-silver alloys into the constituents by thin-layer electrolysis in molten electrolytes, with bismuth as metal separator, is studied. It is proposed to determine the extent of component recovery by potentiometry.  相似文献   
112.
In this paper, a two-dimensional finite volume unstructured mesh method (FVUM) based on a triangular background interpolation mesh is developed for analysing the evolution of the saltwater intrusion into single and multiple coastal aquifer systems. The model formulation consists of a ground-water flow equation and a salt transport equation. These coupled and non-linear partial differential equations are transformed by FVUM into a system of differential/algebraic equations, which is solved using backward differentiation formulas of order one through five. Simulation results are compared with previously published solutions where good agreement is observed.  相似文献   
113.
In this paper a new state called odd-excited binomial state (OEBS) is introduced. It interpolates between the odd number state and the odd-excited coherent state. We discuss some statistical properties, such as the Glauber second-order correlation function and squeezing phenomenon (normal and amplitude-squared squeezing) for this state. The quasiprobability distribution functions (Husimi Q-function and Wigner W-function) are also examined.  相似文献   
114.
115.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 6, pp. 970–975, June, 1991.  相似文献   
116.
In a twisted nematic liquid crystal cell we report and study the self-transparency effect induced by the creation of an isotropic droplet. A simple theoretical model is presented and good agreement with experimental data is found. In a two beams configuration transistor-like behavior is observed and theoretically discussed.  相似文献   
117.
We study a site analogue of directed percolation. Random trajectories are generated and their critical behavior is studied. The critical behavior corresponds to that of simple percolation in some of the parameter space, but elsewhere the exponents reveal new universality classes. As a byproduct, we use the model to make an improved estimate of the percolation hull exponents and to calculate the site percolation probability for the square lattice.  相似文献   
118.
The finite-size corrections, central chargesc, and scaling dimensionsx of tricritical hard squares and critical hard hexagons are calculated analytically. This is achieved by solving the special functional equation or inversion identity satisfied by the commuting row transfer matrices of these lattice models at criticality. The results are expressed in terms of Rogers dilogarithms. For tricritical hard squares we obtainc=7/10,x=3/40, 1/5, 7/8, 6/5 and for hard hexagons we obtainc=4/5,x=2/15, 4/5, 17/15, 4/3, 9/5, in accord with the predictions of conformal and modular invariance.  相似文献   
119.
120.
Summary In 1980 Dahmen-DeVore-Scherer introduced a modulus of continuity which turns out to reflect invariance properties of compound cubature rules effectively. Accordingly, sharp error bounds are derived, the existence of relevant counterexamples being a consequence of a quantitative resonance principle, established previously.  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