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   29963篇
  免费   1236篇
  国内免费   13篇
化学   20758篇
晶体学   226篇
力学   559篇
数学   4104篇
物理学   5565篇
  2023年   250篇
  2022年   171篇
  2021年   336篇
  2020年   502篇
  2019年   457篇
  2018年   664篇
  2017年   614篇
  2016年   1181篇
  2015年   949篇
  2014年   947篇
  2013年   1980篇
  2012年   2195篇
  2011年   2357篇
  2010年   1331篇
  2009年   1066篇
  2008年   1959篇
  2007年   1922篇
  2006年   1676篇
  2005年   1511篇
  2004年   1221篇
  2003年   937篇
  2002年   837篇
  2001年   639篇
  2000年   543篇
  1999年   402篇
  1998年   286篇
  1997年   206篇
  1996年   326篇
  1995年   216篇
  1994年   210篇
  1993年   260篇
  1992年   231篇
  1991年   149篇
  1990年   137篇
  1989年   118篇
  1988年   119篇
  1987年   118篇
  1986年   114篇
  1985年   176篇
  1984年   138篇
  1983年   117篇
  1982年   103篇
  1981年   97篇
  1980年   75篇
  1979年   91篇
  1978年   80篇
  1977年   73篇
  1976年   75篇
  1975年   70篇
  1973年   81篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
This work demonstrates the analytical applicability of single ion-selective membranes (ISMs) and potentiometric sensor array to distinguish and detect cathinone derivatives. Potentiometric data from ISMs based on cation exchanger and varying content of calix[4]arene derivative were processed by principal component analysis (PCA). Such a combination of methods allowed discriminating various individual synthetic cathinones and their recognition from the mixture comprising primary amines (substituted amphetamines+aminoindane). Analytical parameters of ISM containing 1wt % of calix[4]arene derivative were sufficient to detect 1.0×10−4 mol.l−1 1-(4-fluorophenyl)-2-(ethylamino)butan-1-one and 2-(methylamino)-1-phenylbutan-1-one (buphedrone) in both model and saliva samples.  相似文献   
3.
Journal of Solid State Electrochemistry - The addition of nanocrystalline titanium dioxide (P90) to a cathode of Li/S cell enhances its voltammetric charge capacity by 19%, from which only a small...  相似文献   
4.
Czechoslovak Mathematical Journal - We give a complete characterization of closed sets F ? ?2 whose distance function dF:= dist(·, F) is DC (i.e., is the difference of two convex...  相似文献   
5.
Doklady Mathematics - The paper studies the asymptotic behavior of the optimal control for the Poisson type boundary value problem in a domain perforated by holes of an arbitrary shape with...  相似文献   
6.

Organisations are concerned about measuring the performance of the product/service they deliver to their customers. In all types of organisations, if a proper performance assessment is to be developed, it should be measured in different dimensions. At University, the new study programs include the development and assessment of transversal competences due to their importance in enhancing the abilities and improving the employability of students. The achievement of transversal competences can be assessed in different levels/stages; for example, the 1st and 2nd years of a Bachelor’s degree; the 3rd and 4th years of a Bachelor’s degree and at Master’s level. The purpose of this paper is to integrate the research into performance management in organisations to develop an approach consisting of four components (a methodology, a solid and integrated performance management framework, graphical diagrams and quantitative techniques) to assess and manage the achievement of transversal competences through the different levels of study using a consolidated approach. The proposal uses the Analytic Network Process (ANP) to model dependences and feedback among the elements of the competences.

  相似文献   
7.
Central European Journal of Operations Research - Sustainability practice within supply chains remains in an early development phase. Enterprises still need tools that support the integration of...  相似文献   
8.
Journal of Optimization Theory and Applications - This paper proposes and analyzes a globalized version of the Newton method for finding a singularity of the nonsmooth vector fields. Basically, the...  相似文献   
9.
Publications mathématiques de l'IHÉS - We develop a theory of Bridgeland stability conditions and moduli spaces of semistable objects for a family of varieties. Our approach is based...  相似文献   
10.
Experimental Techniques - In the last years, the wind industry has increased in a large scale. A wind turbine out of service leeds to high costs due to both maintenance and repair costs and the...  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