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   216篇
  免费   39篇
  国内免费   36篇
化学   120篇
晶体学   1篇
力学   2篇
数学   103篇
物理学   65篇
  2023年   3篇
  2022年   1篇
  2021年   3篇
  2020年   8篇
  2019年   5篇
  2018年   2篇
  2017年   5篇
  2016年   7篇
  2015年   9篇
  2014年   18篇
  2013年   23篇
  2012年   16篇
  2011年   28篇
  2010年   25篇
  2009年   27篇
  2008年   22篇
  2007年   35篇
  2006年   19篇
  2005年   7篇
  2004年   8篇
  2003年   2篇
  2002年   2篇
  2001年   4篇
  2000年   2篇
  1999年   3篇
  1998年   1篇
  1997年   2篇
  1996年   1篇
  1995年   1篇
  1988年   1篇
  1985年   1篇
排序方式: 共有291条查询结果,搜索用时 31 毫秒
41.
By revisiting the preferential attachment (PA) mechanism for generating a classical scale-free network, we propose a class of novel preferential attachment similarity indices for predicting future links in evolving networks. Extensive experiments on 14 real-life networks show that these new indices can provide more accurate prediction than the traditional one. Due to the improved prediction accuracy and low computational complexity, these proposed preferential attachment indices can be helpful for providing both instructions for mining unknown links and new insights to understand the underlying mechanisms that drive the network evolution.  相似文献   
42.
朱振和  洪勇  葛培文  俞育德 《中国物理》2004,13(12):1982-1991
The stability of the shapes of the growing crystal face and dissolution face in a two-dimensional mathematical model of crystal growth from solution under microgravity is studied. Effects of the interface kinetics and anisotropy of crystallization and dissolution on the stability are also studied. It is proved that the stable shapes of crystal growth face and dissolution face do exist, which are of suitably shaped curves with their upper parts inclined backward properly no matter whether the interface kinetics and the anisotropy are taken into account or not. The stable shapes of the growing crystal faces and dissolution faces are calculated for various cases. The interface kinetics will make the inclination degree of stable crystal growth face reduce and that of stable dissolution face reduce slightly. The anisotropy of crystallization and dissolution may make the inclination degree of stable-growing crystal face smaller or larger, and that of the stable dissolution face varies very slightly.  相似文献   
43.
The stability of the shapes of crystal growth face and dissolution face in a two-dimensional mathematical model of crystal growth from solution under microgravity is studied.It is proved that the stable shapes of crystal growth face and dissolution face do exist,which are suitably shaped curves with their upper parts inclined backward properly.The stable shapes of crystal growth faces and dissolution faces are calculated for various values of parameters,Ra,Pr and Sc.It is shown that the stronger the convection relative to the diffusion in solution is,the more backward the upper parts of the stable crystal growth face and dissolution face are inclined.The orientation and the shape of dissolution face hardly affect the stable shape of crystal growth face and vice versa.  相似文献   
44.
N指标d维广义Brownian Sheet的像集及图集的Hausdorff测度   总被引:2,自引:0,他引:2  
徐赐文 《数学学报》2001,44(6):1131-114
本文得到了N指标d维广义Brownian Sheet的像集及图集的Hausdorff测度的上、下界.  相似文献   
45.
吡啶作为苯环的生物等排体常被用作分子设计的有效基团[1,2],含吡啶类农药已成为近20多年来新农药创制研究的热点领域之一。1,3,4-噻二唑衍生物具有杀虫、杀菌、除草、调节植物生长以及药物活性等多种功效[3-9],因而该类化合物的研究迄今仍方兴未艾。本文根据活性亚结构连接法,  相似文献   
46.
酶催化动力学光度法测定锌   总被引:2,自引:0,他引:2  
近年来酶法在分析测定方面的研究非常活跃,酶法测定锌已有报道,基本为终点测定法。本文中的研究是基于LDH催化下列反应:丙酮酸+NADH=乳酸+NAD^+(氧化型烟酰胺腺嘌呤二核苷酸),锌离子的存在对酶催化反应具有抑制作用,反应速度的变化率与锌离子的浓度呈相关关系,从而可测定试样中的锌离子含量。本方法不需要底物转变完全,与终点测定法相比,可减少测定时间并节省酶量。  相似文献   
47.
宋新建  王胜  汪焱钢 《结构化学》2006,25(4):402-406
1 INTRODUCTION 1,3,4-Thiadiazole derivatives represent an interes- ting class of compounds possessing broad spectrum biological activities[1~4]. Aroyl ureas are known to exhibit diverse biological effects, such as insecticidal, fungicidal, herbicidal and plant growth regulating activities[5~8]. Therefore, it is worthwhile to investi- gate the compounds incorporating both 1,3,4-thiadia- zole nucleus and aroyl urea group. In the previous paper[9], a series of aroyl ureas containing 1,3,4-t…  相似文献   
48.
Luo  Jing  Qin  Hong 《应用数学学报(英文版)》2019,35(4):885-892
Acta Mathematicae Applicatae Sinica, English Series - Ranking and rating individuals is a fundamental problem in multiple comparisons. One of the most well-known approaches is the Plackett-Luce...  相似文献   
49.
邢富冲 《数学学报》2006,49(1):105-114
本文在Bergman空间Bqp(01)中研究关于旋转连续模的Hardy Littlewood逆定理,在通常条件下,得到了与在空间Hp(0相似文献   
50.
In this paper, we investigate the isolated closed orbits of two types of cubic vector fields in R3 by using the idea of central projection transformation, which sets up a bridge connecting the vector field X(x) in R3 with the planar vector fields. We have proved that the cubic vector field in R3 can have two isolated closed orbits or one closed orbit on the invariant cone. As an application of this result, we have shown that a class of 3-dimensional cubic system has at least 10 isolated closed orbits located on 5 invariant cones, and another type of 3-dimensional cubic system has at least 26 isolated closed orbits located on 13 invariant cones or 26 invariant cones.  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