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   105819篇
  免费   18132篇
  国内免费   10161篇
化学   71641篇
晶体学   1222篇
力学   6931篇
综合类   536篇
数学   11959篇
物理学   41823篇
  2024年   371篇
  2023年   2142篇
  2022年   3658篇
  2021年   3961篇
  2020年   4260篇
  2019年   4158篇
  2018年   3564篇
  2017年   3300篇
  2016年   5204篇
  2015年   4964篇
  2014年   6046篇
  2013年   7800篇
  2012年   9456篇
  2011年   9781篇
  2010年   6466篇
  2009年   6183篇
  2008年   6558篇
  2007年   6023篇
  2006年   5502篇
  2005年   4614篇
  2004年   3422篇
  2003年   2691篇
  2002年   2444篇
  2001年   1995篇
  2000年   1776篇
  1999年   2080篇
  1998年   1850篇
  1997年   1721篇
  1996年   1889篇
  1995年   1502篇
  1994年   1461篇
  1993年   1167篇
  1992年   1071篇
  1991年   986篇
  1990年   791篇
  1989年   563篇
  1988年   464篇
  1987年   382篇
  1986年   374篇
  1985年   318篇
  1984年   241篇
  1983年   154篇
  1982年   143篇
  1981年   106篇
  1980年   76篇
  1979年   44篇
  1978年   34篇
  1976年   36篇
  1975年   33篇
  1974年   45篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
141.
142.
谐振子薛定谔方程的简单解法   总被引:2,自引:0,他引:2  
物质的许多物理与化学性质都可以用线性谐振子模型解释,本文用简单的数学运算求解线性谐振子的薛定谔方程,避免了特殊函数等复杂的数学运算,得出了量子力学教材完全相同的结果。  相似文献   
143.
High-level ab initio calculations are carried out to study the relative stability of the two hydrogen bonded structures of water-hydrogen sulfide complex, one with water as the proton donor (A) and the other with hydrogen sulfide as the proton donor (B). The results show that structure A is considerably more stable than B at the correlated level, which is in contrast with previous results obtained from Hartree-Fock calculations.  相似文献   
144.
A series of Gd(1−x)Bx alloys have been prepared by arc melting method. After introducing small quantity of B atom in Gd, the Curie temperature of these alloys increase while the magnetic entropy changes are almost same as that of Gd. The refrigerant capacities of these alloys are also greater than that of Gd. These results suggest that Gd(1−x)Bx alloys may be utilized as refrigerant in household magnetic refrigeration.  相似文献   
145.
Mathematical models with stage structures are proposed to describe the process of awareness, evaluation and decision-making. First, a system of ordinary differential equations is presented that incorporates the awareness stage and the decision-making stage. If the adoption rate is bilinear and imitations are dominant, we find a threshold above which innovation diffusion is successful. Further, if the adoption rate has a higher nonlinearity, it is shown that there exist bistable equilibria and a region such that an innovation diffusion is successful inside and is unsuccessful outside. Secondly, a model with a time delay is proposed that includes an evaluation stage of a product. It is proved that the system exhibits stability switches. The bifurcation direction of equilibria is also discussed.  相似文献   
146.
147.
In this paper,the UV-theory and P-differential calculus are employed to study second-order ex-pansion of a class of D.C.functions and minimization problems.Under certain conditions,some properties ofthe U-Lagrangian,the second-order expansion of this class of functions along some trajectories are formulated.Some first and second order optimality conditions for the class of D.C.optimization problems are given.  相似文献   
148.
The purpose of this work is to investigate the weakened Ambrosetti–Prodi type multiplicity results for weak doubly periodic solutions of damped beam equations. By using the topological degree theory, the author obtains a result which is similar to the result for damped wave equations in the literature.  相似文献   
149.
A simple graphG is said to be fractionaln-factor-critical if after deleting anyn vertices the remaining subgraph still has a fractional perfect matching. For fractionaln-factor-criticality, in this paper, one necessary and sufficient condition, and three sufficient conditions related to maximum matching, complete closure are given.  相似文献   
150.
Recently, the theory of sortability of partition property has been shown to be an effective tool to prove the existence of an optimal partition with that property. In this paper, we extend the theory to multi-partition where the partition is on t types of components. We apply our results to settle an optimal assignment problem whose proof was incomplete as given in the literature.  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