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   11781篇
  免费   1530篇
  国内免费   1455篇
化学   6042篇
晶体学   82篇
力学   393篇
综合类   85篇
数学   791篇
物理学   2518篇
综合类   4855篇
  2024年   47篇
  2023年   208篇
  2022年   395篇
  2021年   397篇
  2020年   436篇
  2019年   450篇
  2018年   366篇
  2017年   365篇
  2016年   483篇
  2015年   550篇
  2014年   656篇
  2013年   767篇
  2012年   880篇
  2011年   869篇
  2010年   599篇
  2009年   594篇
  2008年   667篇
  2007年   540篇
  2006年   528篇
  2005年   476篇
  2004年   395篇
  2003年   473篇
  2002年   652篇
  2001年   532篇
  2000年   349篇
  1999年   345篇
  1998年   246篇
  1997年   203篇
  1996年   213篇
  1995年   159篇
  1994年   160篇
  1993年   133篇
  1992年   150篇
  1991年   109篇
  1990年   106篇
  1989年   72篇
  1988年   60篇
  1987年   45篇
  1986年   34篇
  1985年   16篇
  1984年   12篇
  1983年   12篇
  1982年   2篇
  1981年   4篇
  1979年   1篇
  1971年   1篇
  1959年   2篇
  1957年   2篇
  1955年   1篇
  1936年   3篇
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
81.
The wavelet and harmonic filtering method suggested by Zalevsky and Ouzieli is introduced in this paper and adopted in our volume holographic image recognition system. This composite filter combines several scaled versions of the cascaded wavelet and harmonic filter, obtaining high discrimination ability and wide dynamic range of rotation and scale deformations. Optical experiments are conducted to demonstrate the validity and practicability of the algorithm. To the best of our knowledge, this is the first report of using this algorithm in a volume holographic system. Moreover, the separate correlation approach proposed in this paper greatly simplifies the manufacturing process and reduces the cost of the system.  相似文献   
82.
IntroductionThemethoxyradical (CH3O)isanimportantinter mediateinthephotochemicaloxidationofhydrocarbonsintheatmosphere ,1 3andplaysasignificantroleintrans formingnitricoxidetonitrogendioxide .4 Similarly ,thereactionmechanismsofhydroxylandcarbonmonoxide5,6ando…  相似文献   
83.
We apply the least‐squares finite element method with adaptive grid to nonlinear time‐dependent PDEs with shocks. The least‐squares finite element method is also used in applying the deformation method to generate the adaptive moving grids. The effectiveness of this method is demonstrated by solving a Burgers' equation with shocks. Computational results on uniform grids and adaptive grids are compared for the purpose of evaluation. The results show that the adaptive grids can capture the shock more sharply with significantly less computational time. For moving shock, the adaptive grid moves correctly with the shock. © 2005 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2006  相似文献   
84.
In this paper,the Dirichlet problem of Stokes approximate of non-homogeneous incompressibleNavier-Stokes equations is studied.It is shown that there exist global weak solutions as well as global andunique strong solution for this problem,under the assumption that initial density ρ_0(x)is bounded away from0 and other appropriate assumptions(see Theorem 1 and Theorem 2).The semi-Galerkin method is applied toconstruct the approximate solutions and a prior estimates are made to elaborate upon the compactness of theapproximate solutions.  相似文献   
85.
简要评估了“926”植物生长调节剂的经济效益和生态环境。分析了开发应用的前景。  相似文献   
86.
Semilinear Differential Inclusions in Separable Banach SpacesXueXingmei(薛星美)andSongGuozhu(宋国柱)(DepartmentofMathematics,Nanjin...  相似文献   
87.
Differentkindsofopenchaincrownethershavebeensynthesizedasthemodelcompoundsofionophoresandtheirinteractionswithsodium,potassiumandrareearthionshavealsobeenstudiedl'z.PanshowedCe(III)yieldedalf1complexwithl,8-bis(8'-quinolyloxy)-3,6-dioxaandtheCe(IIl)ioncoordinatedbothtoetheroxygenandquinolinenitrogenatoms3.TUmInleridentifiedtwolanthanidenitratecomplexeshavingastoichiometryof3:2(3RE:2L)'.InordertostUdythefunctionsofbothquinolineandbenzenering,introducedintothepolyetherchain,a1inearpolyether…  相似文献   
88.
89.
90.
The correlation times (τc) and cross relaxation rates of toluene, dimethylformamide, tetrahydrofuran, water-acetone and water-dioxane adsorbed on silica gel, alumina and charcoal were obtained by measurements of the integrated intensities of cross and diagonal peaks in their NOESY spectra. The (τc) of the above mentioned systems is in the range of 10?6?10?9 s, much longer than that in the liquid (10?12?10?14 s). It was found that intramolecular rotation of toluene adsorbed on charcoal is slower than that on SiO2, Al2O3 and the inversion of α and β protons in tetrahydrofuran is very fast (τc = 1.76×10?9 s). The cross relaxation plays an important role in the relaxation of molecules adsorbed on solid surfaces with low electron densities.  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