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   8779篇
  免费   1466篇
  国内免费   839篇
化学   6302篇
晶体学   92篇
力学   478篇
综合类   50篇
数学   1021篇
物理学   3141篇
  2024年   19篇
  2023年   152篇
  2022年   251篇
  2021年   274篇
  2020年   330篇
  2019年   318篇
  2018年   281篇
  2017年   255篇
  2016年   374篇
  2015年   400篇
  2014年   477篇
  2013年   669篇
  2012年   785篇
  2011年   782篇
  2010年   556篇
  2009年   518篇
  2008年   586篇
  2007年   479篇
  2006年   486篇
  2005年   397篇
  2004年   361篇
  2003年   269篇
  2002年   272篇
  2001年   202篇
  2000年   139篇
  1999年   155篇
  1998年   145篇
  1997年   157篇
  1996年   150篇
  1995年   111篇
  1994年   114篇
  1993年   88篇
  1992年   55篇
  1991年   52篇
  1990年   59篇
  1989年   40篇
  1988年   29篇
  1987年   21篇
  1986年   32篇
  1985年   28篇
  1984年   22篇
  1983年   19篇
  1982年   11篇
  1981年   13篇
  1980年   16篇
  1979年   10篇
  1978年   22篇
  1977年   10篇
  1976年   13篇
  1974年   12篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Summary Consider a TPBVP for transferable nonlinear DAE's. In general the shooting equation has a singular Jacobian. A multiple shooting method which has a nonsingular Jacobian and also produces consistent initial values for the integration is presented. The estimation of the condition of the Jacobian shows the well-posedness of the method. Some illustrative examples are given  相似文献   
992.
Synthetic saponites have been intercalated with hydroxyl aluminium oligomers and characterized with several techniques. The basal 001 peak of the pillared saponite (PS) is 1. 8 nm. The amount of the aluminium in the tctrahedral sheet is correlative with cross-linking density. The sheet-to-pillar linkage mode may be Si-O-AlpⅥ. The acid sites in pillared saponite may locate either at surface of clay or at that of pillar. The cumene conversion is relative to accessible acid sites on the surface of PS. The pillar density in the PS has an effect on the pore structure which is correlative with shape selectivity during the reaction between ethanol and ammonia.  相似文献   
993.
994.
ON THE EMPTY CONVEX PARTITION OF A FINITE SET IN THE PLANE   总被引:2,自引:0,他引:2  
The authors discuss the partition of a finite set of points in the plane into empty convex polygons, and improve some upper bound and lower bound in the related enumeration problems.  相似文献   
995.
基态和激发态氧振动光谱的量子力学计算   总被引:3,自引:0,他引:3       下载免费PDF全文
利用分子势能函数的Murrell-Sorbie和PG函数形式,将时域有限差分法应用基态和激发态氧分子的振动能级的量子力学计算,计算结果令人满意.  相似文献   
996.
本实验提供一种测量透明度或半透明度液体的折射率和扩散系数的方法。此方法可用于食品工业、日用化学工业、石油工业及制药工业部门。  相似文献   
997.
In studying the multiple scattering of acoustic waves by a half-space of distributed discrete scatterers, the quasicrystalline approximation(QCA) approach together with the hole correction (HC) or the pair distribution functions (PDF) have been used extensively, in which a system of simultaneous equations must be solved to determine the effective propagation constant and the expansion coefficients of the coherent exciting field. In this paper, we analyse the same problem under Foldy's approximation (EFA) by using the so-called modified T-matrix approach (MTMA) which was first proposed by Twersky. Two equations in a considerably simple and clear form are obtained for determining the effective propagation constant and the amplitude of the coherent transmitted field, as the scatterers are identical spheres. The numerical results in the low-frequency limit are also discussed in brief.  相似文献   
998.
The study of focused ion beam (FIB) milling for making etched facet and semiconductor/air distributed Bragg reflector (DBR) facets of AlGaInP-based red laser diodes (LD) is presented in this letter. For the Ga ion beam current of 100 pA at fixed accelerated voltage 30 kV, FIB milling rate of GaAs was found to be 0.46 μm3/nC. As a trade-off between high reflectivity and enough technical tolerance, the combination of third Bragg orders of semiconductor wall and air gap was chosen. The deeply etched mirror and distributed Bragg reflector facet consisting of pairs of semiconductor wall/air gap on laser diodes (LD) cavity facets with vertical sidewall on AlGaInP LDs were fabricated by focused Ga ion beam milling. Comparison of the AlGaInP LD with the mirrors between cleaved and FIB made facet was given and discussed.  相似文献   
999.
 For every conductor f{1,3,4,5,7,8,9,11,12,15} there exist non-zero abelian varieties over the cyclotomic field Q f ) with good reduction everywhere. Suitable isogeny factors of the Jacobian variety of the modular curve X 1 (f) are examples of such abelian varieties. In the other direction we show that for all f in the above set there do not exist any non-zero abelian varieties over Q f ) with good reduction everywhere except possibly when f=11 or 15. Assuming the Generalized Riemann Hypothesis (GRH) we prove the same result when f=11 and 15. Received: 19 April 2001 / Revised version: 21 October 2001 / Published online: 10 February 2003  相似文献   
1000.
In this paper,we derive the continuous dependence on the terminal condition of solutions to nonlinear reflected backward stochastic differential equations involving the subdifferential operator of a lower semi-continuous,proper and convex function under non-Lipschitz condition by means of the corollary of Bihari inequality.  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