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   2685篇
  免费   101篇
  国内免费   1篇
化学   1545篇
晶体学   30篇
力学   119篇
数学   578篇
物理学   515篇
  2023年   24篇
  2022年   27篇
  2021年   26篇
  2020年   64篇
  2019年   76篇
  2018年   83篇
  2017年   69篇
  2016年   131篇
  2015年   91篇
  2014年   120篇
  2013年   359篇
  2012年   130篇
  2011年   135篇
  2010年   99篇
  2009年   95篇
  2008年   125篇
  2007年   95篇
  2006年   102篇
  2005年   57篇
  2004年   73篇
  2003年   55篇
  2002年   51篇
  2001年   55篇
  2000年   35篇
  1999年   40篇
  1998年   35篇
  1997年   33篇
  1996年   36篇
  1995年   24篇
  1994年   28篇
  1993年   23篇
  1992年   12篇
  1991年   12篇
  1990年   14篇
  1989年   10篇
  1988年   17篇
  1987年   13篇
  1986年   12篇
  1985年   30篇
  1984年   18篇
  1983年   14篇
  1982年   13篇
  1981年   23篇
  1980年   24篇
  1979年   14篇
  1978年   13篇
  1977年   14篇
  1975年   13篇
  1973年   7篇
  1935年   7篇
排序方式: 共有2787条查询结果,搜索用时 415 毫秒
111.
112.
113.
114.
Research on Chemical Intermediates - Both photocatalytic and enzymatic degradation of phenol were studied in order to evaluate and to compare the catalytic potential of both methods. For this,...  相似文献   
115.
In this study, we investigate an adaptive decomposition and ordering strategy that automatically divides examinations into difficult and easy sets for constructing an examination timetable. The examinations in the difficult set are considered to be hard to place and hence are listed before the ones in the easy set in the construction process. Moreover, the examinations within each set are ordered using different strategies based on graph colouring heuristics. Initially, the examinations are placed into the easy set. During the construction process, examinations that cannot be scheduled are identified as the ones causing infeasibility and are moved forward in the difficult set to ensure earlier assignment in subsequent attempts. On the other hand, the examinations that can be scheduled remain in the easy set. Within the easy set, a new subset called the boundary set is introduced to accommodate shuffling strategies to change the given ordering of examinations. The proposed approach, which incorporates different ordering and shuffling strategies, is explored on the Carter benchmark problems. The empirical results show that the performance of our algorithm is broadly comparable to existing constructive approaches.  相似文献   
116.
A series of 25 phenol derivative compounds having potential antioxidant capacity were studied by cyclic voltammetry and square-wave voltammetry, in order to estimate the electrochemical parameters of the redox process occurring at the graphite electrode. A correlation between the structure of phenol derivatives, the peak potential, the HOMO–LUMO gap and their antioxidant activity lead to a qualitative classification of the studied compounds as a function of the increase of their antioxidant capacity.  相似文献   
117.
We study the electronic band structures of massless Dirac fermions in symmetrical graphene superlattice with cells of three regions. opening gaps and additional Dirac points. Finally, we inspect the potential effect on minibands, the anisotropy of group velocity and the energy bands contours near Dirac points. We also discuss the evolution of gap edges and cutoff region near the vertical Dirac points.  相似文献   
118.
119.
120.
The energy profile of a frustrated Lewis pair (FLP) dihydrogen splitting system was determined by a combined experimental kinetic and DFT study. A trimethylene‐bridged phosphane–borane FLP was converted into its endothermic H2‐cleavage product by sequential H+/H? addition. The system could be handled at low temperature, and the kinetics of the H2 elimination were determined to give a rate constant of kHH,exp(299 K)=(2.87±0.1)×10?4 s?1 in solution. The primary kinetic isotope effects were determined; for example, (kHH/kDD)exp=3.19. The system was accurately analyzed by DFT calculations.  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