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   86242篇
  免费   1964篇
  国内免费   1850篇
化学   30690篇
晶体学   877篇
力学   7269篇
综合类   136篇
数学   32872篇
物理学   18212篇
  2023年   175篇
  2022年   331篇
  2021年   361篇
  2020年   391篇
  2019年   392篇
  2018年   10692篇
  2017年   10484篇
  2016年   6450篇
  2015年   1289篇
  2014年   803篇
  2013年   1013篇
  2012年   4533篇
  2011年   11251篇
  2010年   6213篇
  2009年   6524篇
  2008年   7158篇
  2007年   9242篇
  2006年   682篇
  2005年   1709篇
  2004年   1787篇
  2003年   2232篇
  2002年   1326篇
  2001年   538篇
  2000年   520篇
  1999年   399篇
  1998年   366篇
  1997年   308篇
  1996年   308篇
  1995年   235篇
  1994年   184篇
  1993年   184篇
  1992年   131篇
  1991年   142篇
  1990年   95篇
  1989年   87篇
  1988年   80篇
  1987年   73篇
  1986年   79篇
  1985年   63篇
  1984年   50篇
  1983年   46篇
  1982年   48篇
  1981年   46篇
  1980年   48篇
  1979年   44篇
  1914年   45篇
  1913年   40篇
  1912年   40篇
  1909年   41篇
  1908年   40篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Photoelectrochemical(PEC)technique represents a promising approach to chemical transformation by harvesting sustainable solar energy.Despite the wide applications of PEC systems such as environmental remediation and solar energy conversion,the reported PEC reactions are dominated by the radical-based processes that are initiated by the single electron transfer between photo-induced carriers and adsorbed species on photoelectrode surface[1,2].For instance,hydroxyl radicals are often involved in the PEC oxidation reactions.As well known,it is a grand challenge to control the formation and evolution rates of radicals,which inevitably leads to the unsatisfactory product selectivity of PEC reactions.Naturally,such a circumstance brings about a question to the research community whether a different mechanism can be established to sustain efficient and selective oxygenation.Recently,based on their previous findings on PEC water oxidation[3,4],Zhao and coworkers[5]reported that many substrates can be oxidized in an oxygen atom transfer(OAT)pathway,a non-radical two electron process,to oxygenated products byα-Fe2O3 photoanodes.  相似文献   
2.
Journal of Optimization Theory and Applications - We distinguish two kinds of piecewise linear functions and provide an interesting representation for a piecewise linear function between two normed...  相似文献   
3.

We study the Bell nonlocality of high dimensional quantum systems based on quantum entanglement. A quantitative relationship between the maximal expectation value B of Bell operators and the quantum entanglement concurrence C is obtained for even dimension pure states, with the upper and lower bounds of B governed by C.

  相似文献   
4.
In the paper, the authors establish several integral representations for the generating functions of the large and little Schröder numbers and for the large and little Schröder numbers.  相似文献   
5.
Redox-based post-translational modification of protein thiols has become an attractive strategy in cellular homeostasis and cell signaling.Due to the reductive end of the redox buffer network,the vicinal dithiol-containing proteins(VDPs)maintains an appropriate oxidation-reduction state of proteins through the reversible transformation from vicinal dithiols to disulfide,which is responsible for a variety of  相似文献   
6.
Mesoscopic modeling at the pore scale offers great promise in exploring the underlying structure transport performance of flow through porous media. The present work studies the fluid flow subjected to capillarity-induced resonance in porous media characterized by different porous structure and wettability. The effects of porosity and wettability on the displacement behavior of the fluid flow through porous media are discussed. The results are presented in the form of temporal evolution of percentage saturation and displacement of the fluid front through porous media. The present study reveals that the vibration in the form of acoustic excitation could be significant in the mobilization of fluid through the porous media. The dependence of displacement of the fluid on physicochemical parameters like wettability of the surface, frequency along with the porosity is analyzed. It was observed that the mean displacement of the fluid is more in the case of invading fluid with wetting phase where the driving force strength is not so dominant.  相似文献   
7.
8.
We prove that the group of diffeomorphisms of the interval [0, 1] contains surface groups whose action on (0, 1) has no global fix point and such that only countably many points of the interval (0, 1) have non-trivial stabiliser.  相似文献   
9.
10.
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