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   1997篇
  免费   49篇
  国内免费   4篇
化学   1205篇
晶体学   16篇
力学   41篇
数学   188篇
物理学   600篇
  2023年   16篇
  2022年   41篇
  2021年   36篇
  2020年   43篇
  2019年   52篇
  2018年   43篇
  2017年   52篇
  2016年   75篇
  2015年   41篇
  2014年   80篇
  2013年   143篇
  2012年   114篇
  2011年   120篇
  2010年   89篇
  2009年   87篇
  2008年   116篇
  2007年   105篇
  2006年   71篇
  2005年   56篇
  2004年   48篇
  2003年   36篇
  2002年   45篇
  2001年   36篇
  2000年   30篇
  1999年   20篇
  1998年   10篇
  1997年   11篇
  1996年   17篇
  1995年   22篇
  1994年   22篇
  1993年   33篇
  1992年   26篇
  1991年   25篇
  1990年   23篇
  1989年   24篇
  1988年   12篇
  1987年   28篇
  1986年   19篇
  1985年   21篇
  1984年   15篇
  1983年   17篇
  1982年   14篇
  1981年   15篇
  1980年   15篇
  1979年   20篇
  1978年   6篇
  1974年   5篇
  1973年   6篇
  1966年   4篇
  1965年   7篇
排序方式: 共有2050条查询结果,搜索用时 15 毫秒
11.
12.
13.
A novel Mitsunobu-based protocol was developed for the synthesis of carbamates from the corresponding alcohols using carbon dioxide and amines in good to excellent yields. This protocol is mild, chemoselective, and efficient compared to other reported methods.  相似文献   
14.
Traditional inventory models assume that a buyer places one order with a supplier in each order cycle. A large number of researchers have studied the benefits of dual sourcing such that an order quantity is split and placed simultaneously with two suppliers. We show that many of the benefits of dual sourcing are due to order splitting rather than using two suppliers. We investigate order splitting with one supplier such that the first part of the order is sent out immediately but the second part of the order is released later (scheduled-release). Through extensive computational results, we show that in many situations where dual sourcing or the use of a cheaper supplier would be cost effective, single sourcing with order splitting using scheduled-release orders is better. The paper provides a quantitative rationale to continue with one supplier. We also summarize the qualitative reasons to prefer single sourcing or multiple sourcing.  相似文献   
15.
This is the report of flavor physics and model building working group at WHEPP-9. While activites in flavor physics have been mainly focused on B-physics, those in model building have been primarily devoted to neutrino physics. We present summary of working group discussions carried out during the workshop in the above fields, and also briefly review the progress made in some projects subsequently.  相似文献   
16.
The adsorption of mercury(II) on potassium titanate has been studied in chloride media at different pH values, adsorbate concentrations and temperatures. Effect of different ligands and acid concentrations on the uptake was also investigated. Desoprtion studies were also done to check the reversibility of the process. Interestingly a more or less constant and high value of adsorption has been found at different temperatures, pH values and concentrations and a decrease in the uptake with an increase in the bulk acid concentration was observed.  相似文献   
17.
18.
19.
M Mishra  S N Jena  T N Tiwari 《Pramana》1989,32(1):1-11
The heavy mesons of the charmonium and upsilon family are described in an alternative static potential model chosen in a combination of Hulthen and linear potential. We find that the quark-confining potential in the form of an equal admixture of vector and scalar parts successfully explains the fine-hyperfine structures of \(c\bar c\) and \(b\bar b\) systems in a flavour-independent manner. The leptonic decay widths of the vector mesons ofψ and γ families are calculated taking into account the Poggio-Schnitzer correction. We obtain some of the bound states of the yet-to-be observed \(t\bar t\) system for thet-quark mass ranging from 50 to 200 GeV.  相似文献   
20.
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